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microRNAs (miRNAs) play a critical role in a variety of biological processes, including embryogenesis and the physiological functions of cells. Evolutionarily conserved microRNA-31 (miR-31) has been found to be involved in cancer, bone formation, and lymphatic development. We previously discovered that, in the sea urchin, miR-31 knockdown (KD) embryos have shortened dorsoventral connecting rods, mispatterned skeletogenic primary mesenchyme cells (PMCs) and shifted and expanded Vegf3 expression domain. Vegf3 itself does not contain miR-31 binding sites; however, we identified its upstream regulators Eve and Wnt1 to be directly suppressed by miR-31. Removal of miR-31’s suppression of Eve and Wnt1 resulted in skeletal and PMC patterning defects, similar to miR-31 KD phenotypes. Additionally, removal of miR-31’s suppression of Eve and Wnt1 results in an expansion and anterior shift in expression of Veg1 ectodermal genes, including Vegf3 in the blastulae. This indicates that miR-31 indirectly regulates Vegf3 expression through directly suppressing Eve and Wnt1. Furthermore, removing miR-31 suppression of Eve is sufficient to cause skeletogenic defects, revealing a novel regulatory role of Eve in skeletogenesis and PMC patterning. Overall, this study provides a proposed molecular mechanism of miR-31’s regulation of skeletogenesis and PMC patterning through its cross-regulation of a Wnt signaling ligand and a transcription factor of the endodermal and ectodermal gene regulatory network.

BACKGROUND The vertebrate jaw is thought to have evolved through developmental modification of the mandibular arch. An extant jawless vertebrate, the lamprey, possesses a structure called "velum"-a mandibular arch derivative-in addition to the oral apparatus. This leads us to assess the velum's possible contribution to the evolution of jaws. RESULTS The velar muscles develop from progenitor cells distinct from those from which the oral muscles develop. In addition, the oral and velar regions originate from the different sub-population of the trigeminal neural crest cells (NCCs): the former region receives NCCs from the midbrain, whereas the latter region receives NCCs from the anterior hindbrain. The expression of patterning genes (eg, DlxA and MsxA) is activated at a later developmental stage in the velum compared to the oral region, and more importantly, in different cells from those in the oral region. CONCLUSION The lamprey mandibular arch consists of two developmental units: the anterior oral unit and the posterior velar unit. Because structural elements of the lamprey velum may be homologous to the jaw, the evolution of vertebrate jaws may have occurred by the velum being released from its functional roles in feeding or respiration in jawless vertebrates.

AIM The aim of this study was to evaluate the molecular mechanisms of Lactobacillus strains in improving ageing of the musculoskeletal system. METHODS AND RESULTS The anti-ageing mechanism of three probiotics strains Lactobacillus fermentum DR9, Lactobacillus paracasei OFS 0291 and L. helveticus OFS 1515 were evaluated on gastrocnemius muscle and tibia of d-galactose-induced ageing rats. Upon senescence induction, aged rats demonstrated reduced antioxidative genes CAT and SOD expression in both bone and muscle compared to the young rats (P

Secreted ADAMTS metalloproteases are involved in the sculpting, remodeling, and erosion of connective tissues throughout the body, including in the musculoskeletal system. ADAMTS proteases contribute to musculoskeletal development, pathological tissue destruction, and are mutated in congenital musculoskeletal disorders. Examples include versican cleavage by ADAMTS9 which is required for interdigital web regression during limb development, ADAMTS5-mediated aggrecan degradation in osteoarthritis resulting in joint erosion, and mutations in ADAMTS10 or ADAMTS17 that cause Weill-Marchesani syndrome, a short stature syndrome with bone, joint, muscle, cardiac, and eye involvement. Since the function of ADAMTS proteases and proteases in general is primarily defined by the molecular consequences of proteolysis of their respective substrates, it is paramount to identify all physiological substrates for each individual ADAMTS protease. Here, we review the current knowledge of ADAMTS proteases and their involvement in musculoskeletal development and disease, focusing on some of their known physiological substrates and the consequences of substrate cleavage. We further emphasize the critical need for the identification and validation of novel ADAMTS substrates and binding partners by describing the principles of mass spectrometry-based approaches and by emphasizing strategies that need to be considered for validating the physiological relevance for ADAMTS-mediated proteolysis of novel putative substrates.

The proliferation and hypertrophy of chondrocytes play important roles in endochondral ossification, which is tightly regulated during skeleton development. However, the regulation mechanism remains largely unknown. Here we show that DDB1 (Damaged DNA Binding Protein 1) has a critical function in the development of growth plates. Using chondrocyte-specific DDB1 knockout mice, we found that DDB1 deletion in chondrocytes results in dwarfism due to the aberrant skeleton development. The structure of growth plate in tibia becomes disordered at P21, not in femur. But at P70, the changes are severer in femur than tibia. Chondrocyte proliferation and differentiation are attenuated and asynchronous in both tibia and femur at P7 and P21. Furthermore, DDB1 deficiency induces p27 upregulation and subsequent cell cycle arrest in primary chondrocytes. Therefore, our data reveal that DDB1 is essential for the skeleton development by controlling chondrocyte proliferation and differentiation.

BACKGROUND The extremely derived body plan of turtles has sparked a great interest in studying their developmental biology. Here, we describe the embryonic development of the Stinkpot, or common musk turtle (Sternotherus odoratus), a small aquatic turtle from the family Kinosternidae. RESULTS We identify 20 distinct developmental stages, some comparable to stages described by previous studies on other turtles and some in between these, improving the resolution of the generalities of turtle development. We provide a detailed account of both the external morphology and skeletal development, as well as a general look at the early stages of muscular development until the attainment of the adult muscular anatomical pattern. CONCLUSIONS Several potential skeletal and muscular apomorphies of turtles are identified or elaborated. The musk turtle, with its small size and hard-shelled egg, could become an important species for the study of turtle evolution and development, suitable for in ovo experimentation and late stage imaging of well-advanced anatomical features.

Articular cartilage has limited self-healing capacity and damaged cartilage can lead to osteoarthritis, and to the need for joint replacement surgery. Biomaterial based scaffolds have shown limited potential to regenerate osteochondral tissue and generally have insufficient mechanical properties to withstand the mechanically demanding and dynamic joint environment. To overcome this limitation, the primary research goal of this thesis was to develop reinforced collagen based scaffolds for musculoskeletal tissue engineering, with focus on articular cartilage, bone, and osteochondral tissue. A process was initially developed in Chapter 2 to produce a range of 3D printed polycaprolactone (PCL) scaffolds with high reproducibility. Optimized 3D printing parameters resulted in a range of PCL scaffolds designs with different compressive moduli and high porosities suitable for bone, cartilage, and osteochondral tissue engineering. A multiple linear regression (MLR) model was developed that can be used to predict the compressive modulus of future designs of 3D printed PCL scaffolds, and to tune it for specific tissues to make suitable composite scaffolds containing different ECM based matrices. In Chapter 3, the PCL scaffold with mechanical properties optimized for cartilage repair 2 was combined with a collagen type I and hyaluronic acid (CI-HyA) matrix, to make a composite scaffold capable of directing MSC differentiation towards chondrogenesis and having mechanical properties suitable for cartilage repair. Sulphated glycosaminoglycan (sGAG) deposition by MSCs undergoing chondrogenic differentiation in the developed composite CI-HyA scaffold led to increased mechanical properties over culture time. In Chapter 4, a PCL scaffold with a high compressive modulus developed in Chapter 2 was combined with a collagen type I and nano-hydroxyapatite (CI-nHA) matrix, to make composite scaffolds with a composition that can promote MSC osteogenic differentiation to regenerate bone. The composite CI-nHA scaffold sustained MSC osteogenic differentiation and achieved an even calcium distribution throughout its 4 whole volume while having a compressive modulus suitable for bone tissue engineering. In Chapter 5, a composite scaffold for osteochondral repair was made by combining the composite scaffolds developed in Chapter 3 and Chapter 4. These bi-layered composite scaffolds were made with a novel one-step freeze drying technique which achieved spatially defined CI-nHA and CI-HyA layers. The bi-layered composite scaffold induced layer-specific MSC differentiation, with sGAG deposition in the cartilage layer which spread to form a sGAG rich matrix over culture time and an increased calcium deposition over culture time in the bone layer, although the results suggested further optimization of the composition of the cartilage layer was needed to minimize risk of calcification. In Chapter 6 a refined cartilage layer consisting of collagen type I, type II and hyaluronic acid was used in a reinforced tri-layered composite scaffold which also contained an intermediate layer consisting of collage type I and hyaluronic acid to reduce off-site calcification in the cartilage layer. The reinforced tri-layered composite scaffold contained a compressive modulus gradient that resisted shear forces and could be securely fixed in the articular joint. The layered matrix composition led to layer-specific MSC differentiation with sGAG rich ECM being deposited throughout the depth of the cartilage layer with calcium deposition contained to the intermediate and bone layers. In conclusion, the thesis has led to the development of a series of composite scaffold systems based on 3D printed PCL designs which incorporated specific collagen-based matrices with biochemical composition tailored to facilitate cartilage, bone, and osteochondral regeneration. The scaffolds have demonstrated potential to facilitate desired MSC differentiation and matrix formation in vitro, and have the mechanical properties required to withstand the compression and shear forces present in articulating joints suggesting can be used as off-the-shelf treatments for regeneration cartilage, bone, or osteochondral defects, with the potential to avoid or delay the need for joint replacement surgery.

Advances in next-generation sequencing have transformed our ability to identify genetic variants associated with clinical disorders of the musculoskeletal system. However, the means to functionally validate and analyze the physiological repercussions of genetic variation have lagged behind the rate of genetic discovery. The zebrafish provides an efficient model to leverage genetic analysis in an in vivo context. Its utility for orthopedic research is becoming evident in regard to both candidate gene validation as well as therapeutic discovery in tissues such as bone, tendon, muscle, and cartilage. With the development of new genetic and analytical tools to better assay aspects of skeletal tissue morphology, mineralization, composition, and biomechanics, researchers are emboldened to systematically approach how the skeleton develops and to identify the root causes, and potential treatments, of skeletal disease. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:925-936, 2020.

In this review, we highlight themes from a recent workshop focused on "Plasticity of Cell Fate in Musculoskeletal Tissues" held at the Orthopaedic Research Society's 2019 annual meeting. Experts in the field provided examples of mesenchymal cell plasticity during normal musculoskeletal development, regeneration, and disease. A thorough understanding of the biology underpinning mesenchymal cell plasticity may offer a roadmap for promoting regeneration while attenuating pathologic differentiation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:708-718, 2020.

ACL injuries are becoming increasingly common in children and adolescents, but little is known regarding age-specific ACL function in these patients. To improve our understanding of changes in musculoskeletal tissues during growth and given the limited availability of pediatric human cadaveric specimens, tissue structure and function can be assessed in large animal models, such as the pig.Using cadaveric porcine specimens ranging throughout skeletal growth, we aimed to assess age-dependent changes in (1) joint kinematics under applied AP loads and varus-valgus moments, (2) biomechanical function of the ACL under the same loads, (3) the relative biomechanical function of the anteromedial and posterolateral bundles of the ACL; and (4) size and orientation of the anteromedial and posterolateral bundles.Stifle joints (analogous to the human knee) were collected from female Yorkshire crossbreed pigs at five ages ranging from early youth to late adolescence (1.5, 3, 4.5, 6, and 18 months; n = 6 pigs per age group, 30 total), and MRIs were performed. A robotic testing system was used to determine joint kinematics (AP tibial translation and varus-valgus rotation) and in situ forces in the ACL and its bundles in response to applied anterior tibial loads and varus-valgus moments. To see if morphological changes to the ACL compared with biomechanical changes, ACL and bundle cross-sectional area, length, and orientation were calculated from MR images.Joint kinematics decreased with increasing age. Normalized AP tibial translation decreased by 44% from 1.5 months (0.34 ± 0.08) to 18 months (0.19 ± 0.02) at 60° of flexion (p0.001) and varus-valgus rotation decreased from 25° ± 2° at 1.5 months to 6° ± 2° at 18 months (p0.001). The ACL provided the majority of the resistance to anterior tibial loading at all age groups (75% to 111% of the applied anterior force; p = 0.630 between ages). Anteromedial and posterolateral bundle function in response to anterior loading and varus torque were similar in pigs of young ages. During adolescence (4.5 to 18 months), the in situ force carried by the anteromedial bundle increased relative to that carried by the posterolateral bundle, shifting from 59% ± 22% at 4.5 months to 92% ± 12% at 18 months (data for 60° of flexion, p0.001 between 4.5 and 18 months). The cross-sectional area of the anteromedial bundle increased by 30 mm throughout growth from 1.5 months (5 ± 2 mm) through 18 months (35 ± 8 mm; p0.001 between 1.5 and 18 months), while the cross-sectional area of the posterolateral bundle increased by 12 mm from 1.5 months (7 ± 2 mm) to 4.5 months (19 ± 5 mm; p = 0.004 between 1.5 and 4.5 months), with no further growth (17 ± 7 mm at 18 months; p = 0.999 between 4.5 and 18 months). However, changes in length and orientation were similar between the bundles.We showed that the stifle joint (knee equivalent) in the pig has greater translational and rotational laxity in early youth (1.5 to 3 months) compared with adolescence (4.5 to 18 months), that the ACL functions as a primary stabilizer throughout growth, and that the relative biomechanical function and size of the anteromedial and posterolateral bundles change differently with growth.Given the large effects observed here, the age- and bundle-specific function, size, and orientation of the ACL may need to be considered regarding surgical timing, graft selection, and graft placement. In addition, the findings of this study will be used to motivate pre-clinical studies on the impact of partial and complete ACL injuries during skeletal growth.

The fibrillins are large extracellular matrix molecules that polymerize to form microfibrils. Fibrillin microfibrils are distinctive architectural elements that are both ubiquitous in the connective tissue space and also unique, displaying tissue-specific patterns. Mutations in the genes for fibrillin-1 (FBN1) result in multiple distinct pleiotropic disorders. Most of the more than 3000 mutations known today in FBN1 cause the Marfan syndrome. Marfan mutations can occur in any of the 56 domains that compose fibrillin-1. In contrast, rare mutations in FBN1 that are confined to only certain domains cause several different types of acromelic dysplasia. These genetic disorders demonstrate that specific domains of fibrillin-1 perform roles important to musculoskeletal growth. Many of the phenotypes of acromelic dysplasias are the opposite of those found in Marfan syndrome. Knowledge of the functions and structural organization of fibrillin molecules within microfibrils is required to understand how one protein and one gene can be the basis for multiple genetic disorders.

Tendons and ligaments are fibrous connective tissues vital to the transmission of force and stabilization of the musculoskeletal system. Arising in precise regions of the embryo, tendons and ligaments share many properties and little is known about the molecular differences that differentiate them. Recent studies have revealed heterogeneity and plasticity within tendon and ligament cells, raising questions regarding the developmental mechanisms regulating tendon and ligament identity. Here, we discuss recent findings that contribute to our understanding of the mechanisms that establish and maintain tendon progenitors and their differentiated progeny in the head, trunk and limb. We also review the extent to which these findings are specific to certain anatomical regions and model organisms, and indicate which findings similarly apply to ligaments. Finally, we address current research regarding the cellular lineages that contribute to tendon and ligament repair, and to what extent their regulation is conserved within tendon and ligament development.

Musculoskeletal (MSK) disorders are one of the leading causes of disability for people of all ages and impart significant socio-economic burdens on society [...]

Forkhead (Fkh/Fox) domain transcription factors (TFs) mediate multiple cardiogenic processes in both mammals and Drosophila. We showed previously that the Drosophila Fox gene jumeau (jumu) controls three categories of cardiac progenitor cell division—asymmetric, symmetric, and cell division at an earlier stage—by regulating Polo kinase activity, and mediates the latter two categories in concert with the TF Myb. Those observations raised the question of whether other jumu-regulated genes also mediate all three categories of cardiac progenitor cell division or a subset thereof. By comparing microarray-based expression profiles of wild-type and jumu loss-of-function mesodermal cells, we identified nebbish (neb), a kinesin-encoding gene activated by jumu. Phenotypic analysis shows that neb is required for only two categories of jumu-regulated cardiac progenitor cell division: symmetric and cell division at an earlier stage. Synergistic genetic interactions between neb, jumu, Myb, and polo and the rescue of jumu mutations by ectopic cardiac mesoderm-specific expression of neb demonstrate that neb is an integral component of a jumu-regulated subnetwork mediating cardiac progenitor cell divisions. Our results emphasize the central role of Fox TFs in cardiogenesis and illustrate how a single TF can utilize different combinations of other regulators and downstream effectors to control distinct developmental processes.

PURPOSE OF REVIEW: The ability to analyze the molecular events occurring within individual cells as opposed to populations of cells is revolutionizing our understanding of musculoskeletal tissue development and disease. Single cell studies have the great potential of identifying cellular subpopulations that work in a synchronized fashion to regenerate and repair damaged tissues during normal homeostasis. In addition, such studies can elucidate how these processes break down in disease as well as identify cellular subpopulations that drive the disease. This review highlights three emerging technologies: single cell RNA sequencing (scRNA-seq), Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq), and Cytometry by Time-Of-Flight (CyTOF) mass cytometry. RECENT FINDINGS: Technological and bioinformatic tools to analyze the transcriptome, epigenome, and proteome at the individual cell level have advanced rapidly making data collection relatively easy; however, understanding how to access and interpret the data remains a challenge for many scientists. It is, therefore, of paramount significance to educate the musculoskeletal community on how single cell technologies can be used to answer research questions and advance translation. SUMMARY: This article summarizes talks given during a workshop on “Single Cell Omics” at the 2020 annual meeting of the Orthopedic Research Society. Studies that applied scRNA-seq, ATAC-seq, and CyTOF mass cytometry to cartilage development and osteoarthritis are reviewed. This body of work shows how these cutting-edge tools can advance our understanding of the cellular heterogeneity and trajectories of lineage specification during development and disease.

Homozygous mutation of the Csf1r locus (Csf1rko) in mice, rats and humans leads to multiple postnatal developmental abnormalities. To enable analysis of the mechanisms underlying the phenotypic impacts of Csf1r mutation, we bred a rat Csf1rko allele to the inbred dark agouti (DA) genetic background and to a Csf1r-mApple reporter transgene. The Csf1rko led to almost complete loss of embryonic macrophages and ablation of most adult tissue macrophage populations. We extended previous analysis of the Csf1rko phenotype to early postnatal development to reveal impacts on musculoskeletal development and proliferation and morphogenesis in multiple organs. Expression profiling of 3-week old wild-type (WT) and Csf1rko livers identified 2760 differentially expressed genes associated with the loss of macrophages, severe hypoplasia, delayed hepatocyte maturation, disrupted lipid metabolism and the IGF1/IGF binding protein system. Older Csf1rko rats developed severe hepatic steatosis. Consistent with the developmental delay in the liver Csf1rko rats had greatly-reduced circulating IGF1. Transfer of WT bone marrow (BM) cells at weaning without conditioning repopulated resident macrophages in all organs, including microglia in the brain, and reversed the mutant phenotypes enabling long term survival and fertility. WT BM transfer restored osteoclasts, eliminated osteopetrosis, restored bone marrow cellularity and architecture and reversed granulocytosis and B cell deficiency. Csf1rko rats had an elevated circulating CSF1 concentration which was rapidly reduced to WT levels following BM transfer. However, CD43hi non-classical monocytes, absent in the Csf1rko, were not rescued and bone marrow progenitors remained unresponsive to CSF1. The results demonstrate that the Csf1rko phenotype is autonomous to BM-derived cells and indicate that BM contains a progenitor of tissue macrophages distinct from hematopoietic stem cells. The model provides a unique system in which to define the pathways of development of resident tissue macrophages and their local and systemic roles in growth and organ maturation., Author summary Monocytes and macrophages are cells of the innate immune system produced by the bone marrow that can be recruited into tissues to support defense against infection and repair following injury. So-called resident macrophages are abundant in every tissue in the body. Their numbers are controlled by a hormone-like growth factor called macrophage colony-stimulating factor (CSF1). Mutations in the surface receptor (CSF1R) that enables macrophages to respond to CSF1 lead to the loss of tissue macrophages. Human patients born with CSF1R mutations may die in infancy or suffer severe developmental abnormalities in the skeleton and brain. In this study we report the effects of the loss of tissue macrophages on postnatal growth and development in a rat model of CSF1R deficiency. In this model there was a global loss of resident macrophages, severe postnatal growth defects, failure of development of multiple organs including the liver and early death. The effects of the mutation could be rescued completely by transfer of normal bone marrow cells into the peritoneal cavity at weaning permitting long term survival and even fertility. The results indicate that postnatal expansion of tissue macrophage populations is essential for normal development.

The biological signals that coordinate the three-dimensional outgrowth and patterning of the vertebrate limb bud have been well delineated. These include a number of vital embryonic signaling pathways, including the fibroblast growth factor, WNT, transforming growth factor, and hedgehog. Collectively these signals converge on multiple progenitor populations to drive the formation of a variety of tissues that make up the limb musculoskeletal system, such as muscle, tendon, cartilage, stroma, and bone. The basic mechanisms regulating the commitment and differentiation of diverse limb progenitor populations has been successfully modeled in vitro using high density primary limb mesenchymal or micromass cultures. However, this approach is limited in its ability to more faithfully recapitulate the assembly of progenitors into organized tissues that span the entire musculoskeletal system. Other biological systems have benefitted from the development and availability of three-dimensional organoid cultures which have transformed our understanding of tissue development, homeostasis and regeneration. Such a system does not exist that effectively models the complexity of limb development. However, limb bud organ cultures while still necessitating the use of collected embryonic tissue have proved to be a powerful model system to elucidate the molecular underpinning of musculoskeletal development. In this methods article, the derivation and use of limb bud organ cultures from murine limb buds will be described, along with strategies to manipulate signaling pathways, examine gene expression and for longitudinal lineage tracking.

Previous research indicates that the musculoskeletal development of pullets is improved when pullets are reared in aviaries compared to conventional rearing cages. However, there are considerable differences in rearing aviary design. To measure locomotion and musculoskeletal development of brown (n = 7) and white-feathered (n = 8) strains of pullets, 15 commercial flocks in three styles of rearing aviaries differing in structural complexity (n = 5 per style) were visited three times: 25.9 ± 6.67, 68.0 ± 4.78, and 112.1 ± 3.34 days of age. Locomotion (duration of standing, sitting, walking, running, flying, and rates jumping, flying, group running and walking) was analysed from videos recorded three times per day: at the beginning, middle, and end of the light cycle. Pullets for dissection were taken on visits 2 and 3. Pullets in the most complex system (style 3, S3) spent the most time locomoting throughout rearing (p &lt, 0.05). Pullets in S3, particularly white-feathered strains, performed the highest rate of vertical transitions (p &lt, 0.05). There were no differences in any of the proportional muscle weights between aviaries styles (p &gt, 0.05) despite the differences in locomotion. White-feathered strains, however, had proportionally heavier pectoralis major (p &lt, 0.0001), pectoralis minor (p &lt, 0.0001), and lighter leg muscles (p &lt, 0.0001) than brown-feathered strains. White-feathered strains and pullets in S3 also had proportionally stronger tibiae and femurs than brown-feathered strains and pullets housed in the least structurally complex system (style 1, S1) (p &lt, 0.05). However, there were no differences found in the breaking strength of the radius and humerus between strain colours or aviary styles (p &lt, 0.05). Therefore, strain, as well as differences in rearing aviary design, can affect the types of locomotion that growing pullets perform, which may, in turn, impact their skeletal development.

Studies and reviews show that the vast majority of students around the world use heavy and uncomfortable backpacks, which could negatively affect their musculoskeletal development or at least generate a non-physiological functional overload. In this regard, non-invasive analyses were carried out on a sample of 150 healthy students aged between 14 and 15 years using a wearable inertial device for gait analysis: G-Walk System by BTS Bioengineering. Each student performed a gait analysis session consisting in a walk of 15 meters along a straight path in two different conditions: free walk and walk with backpack. A backpack with a sturdy backrest, wide and padded straps and abdominal belt with buckle was chosen. The weight inside the backpack was fixed at 9.3 kg in accordance with scientific studies conducted by Stefano Negrini of ISICO (Istituto Scientifico Italiano Colonna Vertebrale). Aim of this work is to understand, through an accurate analysis both instrumental and statistical, if we can talk about differential influence of musculoskeletal type generated by a school backpack full load compared to no backpack, trying to find out if and how much this affects walking both in terms of space-time parameters and detachment from normality values, and in terms of kinematic parameters such as pelvic rotations angles. Results showed a statistically significant difference between the space-time parameters computed in the two different study conditions, moreover a qualitative and quantitative difference was found for kinematic parameters too, which could imply potential musculoskeletal disorders associated with prolonged and long-lasting use of heavy and uncomfortable backpacks. This study has the ambition to raise awareness of this issue in order to extend legislative limits to the "working" environment of children, that is the school, as it is done for working environments adults (D. lgs 81/08 related to manual maintenance of loads).Studi e revisioni mostrano che la stragrande maggioranza degli studenti di tutto il mondo utilizza zaini pesanti e non confortevoli, che potrebbero influire negativamente sul loro sviluppo muscolo-scheletrico o quantomeno generare un sovraccarico funzionale non fisiologico. A tal proposito sono state svolte analisi non invasive su un campione di 150 studenti sani di età compresa tra i 14 ed i 15 anni mediante l’utilizzo di un dispositivo medico inerziale indossabile per analisi del movimento: il sistema G-WALK della BTS Bioengineering. Ogni singolo studente ha percorso un tratto rettilineo di 15 metri sia a corpo libero che indossando uno zaino; è stato scelto uno zaino dotato di robusto schienale, bretelle ampie ed imbottite e cintura addominale con fibbia con massa pari a 9.3 kg in accordo con gli studi scientifici condotti da Stefano Negrini dell’ISICO (Istituto Scientifico Italiano Colonna Vertebrale). L’obiettivo del presente lavoro è di comprendere, attraverso un’analisi accurata sia di tipo strumentale che statistica, se si può parlare di influenza differenziale di tipo muscolo-scheletrico generata da uno zaino scolastico a pieno carico paragonato a nessuno zaino, cercando di individuare se e quanto tutto ciò incide nella deambulazione sia in termini di parametri spazio-temporali e distacco dai valori di normalità, che in termini di parametri cinematici quali gli angoli di rotazione pelvica. I risultati hanno mostrato una differenza statisticamente significativa tra i parametri spaziotemporali e differenze qualitative e quantitative tra i parametri cinematici calcolati nelle due differenti condizioni di cammino il che potrebbe presupporre potenziali disturbi muscoloscheletrici associati ad un uso prolungato e duraturo di zaini pesanti e non confortevoli. Lo studio ha la velleità di sensibilizzare tale tema al fine di estendere limiti legislativi anche all’ambiente “lavorativo” dei bambini ovvero la scuola così come viene fatto per gli ambienti lavorativi adulti (D.lgs 81/08 relativo alla manutenzione manuale dei carichi).

Syncytial skeletal muscle cells contain hundreds of nuclei in a shared cytoplasm. We investigated nuclear heterogeneity and transcriptional dynamics in the uninjured and regenerating muscle using single-nucleus RNA-sequencing (snRNAseq) of isolated nuclei from muscle fibers. This revealed distinct nuclear subtypes unrelated to fiber type diversity, previously unknown subtypes as well as the expected ones at the neuromuscular and myotendinous junctions. In fibers of the Mdx dystrophy mouse model, distinct subtypes emerged, among them nuclei expressing a repair signature that were also abundant in the muscle of dystrophy patients, and a nuclear population associated with necrotic fibers. Finally, modifications of our approach revealed the compartmentalization in the rare and specialized muscle spindle. Our data identifies nuclear compartments of the myofiber and defines a molecular roadmap for their functional analyses; the data can be freely explored on the MyoExplorer server (https://shiny.mdc-berlin.de/MyoExplorer/)., The transcriptional programs of nuclei in the muscle syncytium were assumed to be homogenous except at the neuromuscular and myotendinous junctions. Here, using single-nucleus transcriptomics, the authors reveal a previously unrecognized diversity and dynamics of myonuclear transcriptional programs.

During musculoskeletal system development, mechanical tension is generated between muscles and tendon-cells. This tension is required for muscle differentiation and is counterbalanced by tendon-cells avoiding tissue deformation. Both, Jbug/Filamin, an actin-meshwork organizing protein, and non-muscle Myosin-II (Myo-II) are required to maintain the shape and cell orientation of the Drosophila notum epithelium during flight muscle attachment to tendon cells. Here we show that halving the genetic dose of Rho kinase (Drok), the main activator of Myosin-II, enhances the epithelial deformation and bristle orientation defects associated with jbug/Filamin knockdown. Drok and activated Myo-II localize at the apical cell junctions, tendon processes and are associated to the myotendinous junction. Further, we found that Jbug/Filamin co-distribute at tendon cells with activated Myo-II. Finally, we found that Jbug/Filamin and Myo-II are in the same molecular complex and that the actin-binding domain of Jbug/Filamin is necessary for this interaction. These data together suggest that Jbug/Filamin and Myo-II proteins may act together in tendon cells to balance the tension generated during development of muscles-tendon interaction, maintaining the shape and polarity of the Drosophila notum epithelium.

Skeletal abnormalities are common in children and adolescents diagnosed and treated for a malignancy. The spectrum ranges from mild pain to debilitating osteonecrosis and fractures. In this review, we summarize the impact of cancer therapy on the developing skeleton, provide an update on therapeutic strategies for prevention and treatment, and discuss the most recent advances in musculoskeletal research. Early recognition of skeletal abnormalities and strategies to optimize bone health are essential to prevent long-term skeletal sequelae and diminished quality of life in childhood cancer survivors.

Female gymnasts have been evidenced to experience sport-specific growth, of which broad shoulders and narrow hips are common characteristics. In addition to being a central component of handstand performance, postural control mechanisms, including whole-body and lumbo-pelvic stability, have been identified as risk factors for overuse spinal pathology. The study aimed to develop a fundamental understanding of musculoskeletal growth and postural control responses of female artistic gymnasts in order to extend longitudinal insights into overuse spinal pathology risk. Whole-body anthropometric measures were collected for 12 competitive female gymnasts (age at recruitment: nine to 15 years) at three time points across a 12 month period. Musculoskeletal growth was partially defined as the rate of bicristal-to-biacromial breadth ratio development, and informed shoulder- and pelvis-dominant growth sub-groups. Kinematic and kinetic indicators of postural control were determined for a total of 700 handstand trials. The shoulder-dominant (gymnastics-specific) growth group was found to have significantly greater biomechanical risk for general stability (p

Background/Aims: There is limited information on the impact of recombinant human growth hormone (rhGH) on the muscle-bone unit in children with Crohn’s disease (CD). In this pilot study, we report on the effects of rhGH on bone formation, dual-energy X-ray absorptiometry (DXA) total body (TB) bone mineral density adjusted for height and lumbar spine (LS) bone mineral apparent density (BMAD), and body composition. Methods: Prospective study of 8 children with CD (6 male), aged 14.8 years (9.0–16.4), who received rhGH for 24 months. Serum procollagen type 1 N-terminal propeptide (P1NP) was measured at baseline and at 6 months. DXA was performed every 6 months. Results: Six months of rhGH led to improvement in P1NP SDS adjusted for bone age from –3.6 (–7.9 to –0.9) to –2.4 (–3.7 to 0.4) (p = 0.01). At baseline, reduction in LS-BMAD and TB lean mass SDS was observed being –1.2 (–3.6 to 0.8) (p = 0.01 vs. zero) and –0.8 (–2.4 to 3.0) (p = 0.11 vs. zero), respectively. No significant changes were seen in DXA bone and muscle parameters over the 24 months. Conclusion: Twenty-four months of therapy with rhGH in CD did not lead to an improvement in DXA BMD and lean mass, despite improvement in P1NP and linear growth.

Increased youth participation in sports has resulted in increased injury tolls due to shifts toward participation in competitive sports at earlier ages, increased training intensity and competition schedules, as well as specialization into one sport. The physiology of the growing musculoskeletal system makes the growing athlete particularly vulnerable to specific types of injuries. Radiologists must understand the differences between pediatric and adult athletes to recognize the particular injuries to which these young athletes are prone. Imaging and pertinent clinical details of major representative acute and overuse injuries characteristic to pediatric athletes will be discussed.

Purpose To determine the changes of diffusion-tensor imaging (DTI) and tractography in the distal femur and proximal tibia related to age, sex, and height. Materials and Methods Following institutional review board approval, with waiver of consent and with HIPAA compliance, the authors retrospectively analyzed DTI images of the knee in 151 children, 73 girls (median age, 14.1 years; range, 6.5-17.8 years) and 78 boys (median age, 16.6 years; range, 6.9-17.9 years), studied from January 2013 to October 2014. At sagittal echo-planar DTI (20 directions, b values of 0 and 600 sec/mm

Defining the mechanisms underlying the programming of early life growth is fundamental for improving adult health and wellbeing. While the association between maternal diet, offspring growth and adult disease risk is well-established, the effect of father's diet on offspring development are largely unknown. Therefore, we fed male mice an imbalanced low protein diet (LPD) to determine the impact on post-fertilisation development and fetal growth. We observed that in preimplantation embryos derived from LPD fed males, expression of multiple genes within the central metabolic AMPK pathway was reduced. In late gestation, paternal LPD programmed increased fetal weight, however, placental weight was reduced, resulting in an elevated fetal:placental weight ratio. Analysis of gene expression patterns revealed increased levels of transporters for calcium, amino acids and glucose within LPD placentas. Furthermore, placental expression of the epigenetic regulators Dnmt1 and Dnmt3L were increased also, coinciding with altered patterns of maternal and paternal imprinted genes. More strikingly, we observed fetal skeletal development was perturbed in response to paternal LPD. Here, while offspring of LPD fed males possessed larger skeletons, their bones comprised lower volumes of high mineral density in combination with reduced maturity of bone apatite. These data offer new insight in the underlying programming mechanisms linking poor paternal diet at the time of conception with the development and growth of his offspring.

The evolution of ballistic tongue projection in plethodontid salamanders—a high-performance and thermally robust musculoskeletal system—is ideal for examining how the components required for extreme performance in animal movement are assembled in evolution. Our comparative data on whole-organism performance measured across a range of temperatures and the musculoskeletal morphology of the tongue apparatus were examined in a phylogenetic framework and combined with data on muscle contractile physiology and neural control. Our analysis reveals that relatively minor evolutionary changes in morphology and neural control have transformed a muscle-powered system with modest performance and high thermal sensitivity into a spring-powered system with extreme performance and functional robustness in the face of evolutionarily conserved muscle contractile physiology. Furthermore, these changes have occurred in parallel in both major clades of this largest family of salamanders. We also find that high-performance tongue projection that exceeds available muscle power and thermal robustness of performance coevolve, both being emergent properties of the same elastic-recoil mechanism. Among the taxa examined, we find muscle-powered and fully fledged elastic systems with enormous performance differences, but no intermediate forms, suggesting that incipient elastic mechanisms do not persist in evolutionary time. A growing body of data from other elastic systems suggests that similar coevolution of traits may be found in other ectothermic animals with high performance, particularly those for which thermoregulation is challenging or ecologically costly.

The Ror-family receptor tyrosine kinases (RTKs), consisting of Ror1 and Ror2, play crucial roles in morphogenesis and formation of various tissues/organs, including the bones and skeletal muscles, the so-called musculoskeletal system, during embryonic development, by acting as receptors or coreceptors for a noncanonical Wnt protein Wnt5a. Furthermore, several lines of evidence have indicated that Ror1 and/or Ror2 play critical roles in the regeneration and maintenance of the musculoskeletal system in adults. Considering the anatomical and functional relationship between the skeleton and skeletal muscles, their structural and functional association might be tightly regulated during their embryonic development, development after birth, and their regeneration after injury in adults. Importantly, in addition to their congenital anomalies, much attention has been paid onto the age-related disorders of the musculoskeletal system, including osteopenia and sarcopenia, which affect severely the quality of life. In this article, we overview recent advances in our understanding of the roles of Ror1- and/or Ror2-mediated signaling in the embryonic development, regeneration in adults, and congenital and age-related disorders of the musculoskeletal system and discuss possible therapeutic approaches to locomotive syndromes by modulating Ror1- and/or Ror2-mediated signaling.

Nascent myotubes undergo a dramatic morphological transformation during myogenesis in which the myotubes elongate over several cell diameters and choose the correct muscle attachment sites. Although this process of myotube guidance is essential to pattern the musculoskeletal system, the mechanisms that control myotube guidance remain poorly understood. Using transcriptomics, we found that components of the Fibroblast Growth Factor (FGF) signaling pathway were enriched in nascent myotubes in Drosophila embryos. Null mutations in the FGF receptor heartless (htl), or its ligands, caused significant myotube guidance defects. The FGF ligand Pyramus is expressed broadly in the ectoderm and ectopic Pyramus expression disrupted muscle patterning. Mechanistically, Htl regulates the activity of Rho/Rac GTPases in nascent myotubes and effects changes in the actin cytoskeleton. FGF signals are thus essential regulators of myotube guidance that act through cytoskeletal regulatory proteins to pattern the musculoskeletal system.

The hypothalamus-pituitary-thyroid (HPT) axis plays a crucial role in the metabolism, homeostasis, somatic growth and development of teleostean fishes. Thyroid hormones regulate essential biological functions such as growth and development, regulation of stress, energy expenditure, tissue compound, and psychological processes. Teleost thyroid follicles produce the same thyroid hormones as in other vertebrates: thyroxin (T4) and triiodothyronine (T3), making the zebrafish a very useful model to study hypo- and hyperthyroidism in other vertebrate taxa, including humans. Here we investigate morphological changes in T3 hyperthyroid cases in the zebrafish to better understand malformations provoked by alterations of T3 levels. In particular, we describe musculoskeletal abnormalities during the development of the zebrafish appendicular skeleton and muscles, compare our observations with those recently done by us on the normal developmental of the zebrafish, and discuss these comparisons within the context of evolutionary developmental pathology (Evo-Devo-Path), including human pathologies.

Subjective energy intake (sEI) is often misreported, providing unreliable estimates of energy consumed. Therefore, relating sEI data to health outcomes is difficult. Recently, Börnhorst et al. compared various methods to correct sEI-based energy intake estimates. They criticised approaches that categorise participants as under-reporters, plausible reporters and over-reporters based on the sEI:total energy expenditure (TEE) ratio, and thereafter use these categories as statistical covariates or exclusion criteria. Instead, they recommended using external predictors of sEI misreporting as statistical covariates. We sought to confirm and extend these findings. Using a sample of 190 adolescent boys (mean age=14), we demonstrated that dual-energy X-ray absorptiometry-measured fat-free mass is strongly associated with objective energy intake data (onsite weighted breakfast), but the association with sEI (previous 3-d dietary interview) is weak. Comparing sEI with TEE revealed that sEI was mostly under-reported (74 %). Interestingly, statistically controlling for dietary reporting groups or restricting samples to plausible reporters created a stronger-than-expected association between fat-free mass and sEI. However, the association was an artifact caused by selection bias – that is, data re-sampling and simulations showed that these methods overestimated the effect size because fat-free mass was related to sEI both directly and indirectly via TEE. A more realistic association between sEI and fat-free mass was obtained when the model included common predictors of misreporting (e.g. BMI, restraint). To conclude, restricting sEI data only to plausible reporters can cause selection bias and inflated associations in later analyses. Therefore, we further support statistically correcting sEI data in nutritional analyses. The script for running simulations is provided.

Endochondral ossification is under the regulation of endocrine, paracrine and otocrine factors including transforming growth factor-β superfamily members, fibroblast growth factors, retinoids, products of hedgehog gene, parathyroid hormone-related peptide, molecules involved in cell adhesion, and extracellular matrix components. Natriuretic peptide receptor-B, and its ligand C-type natriuretic peptide have also been implicated in the regulation of limb bone development. Results of recent studies are promising in terms of systemic elevation of C-type natriuretic peptide level inducing growth. In addition, same strategy also overcomes the dwarf phenotype of achondroplasia, the most frequently seen skeletal dysplasia in human, in a mouse model. Based on this literature and a series of recent experiments discussed here, this perspective underlines the abundant C-type natriuretic peptide expression in trabecular bone derived mesenchymal stem cells of human, chicken, and rat origin, and proposes the potential use of mesenchymal stem cells as a part of growth inducing treatment strategy in osteochondrodisyplasias in the future. © 2016 Bentham Science Publishers.

The limb musculoskeletal system provides a primary means for locomotion, manipulation of objects and protection for most vertebrate organisms. Intricate integration of the bone, tendon and muscle tissues are required for function. These three tissues arise largely independent of one another, but the connections formed during later development are maintained throughout life and are re-established following injury. Each of these tissues also have mesenchymal stem/progenitor cells that function in maintenance and repair. Here in, we will review the major events in the development of limb skeleton, tendon, and muscle tissues, their response to injury, and discuss current knowledge regarding resident progenitor/stem cells within each tissue that participate in development, repair, and regeneration in vivo.

Entheses have rarely been systematically studied in the field of human evolution. However, the investigation of their morphological variability (e.g., robusticity) could provide new insight into their evolutionary significance in the European Neanderthal populations. The aim of this work is to study the entheses and joint features of the lower limbs of El Sidrón Neanderthals (Spain; 49 ka), using standardized scoring methods developed on modern samples. Paleobiology, growth, and development of both juveniles and adults from El Sidrón are studied and compared with those of Krapina Neanderthals (Croatia, 130 ka) and extant humans. The morphological patterns of the gluteus maximus and vastus intermedius entheses in El Sidrón, Krapina, and modern humans differ from one another. Both Neanderthal groups show a definite enthesis design for the gluteus maximus, with little intrapopulation variability with respect to modern humans, who are characterized by a wider range of morphological variability. The gluteus maximus enthesis in the El Sidrón sample shows the osseous features of fibrous entheses, as in modern humans, whereas the Krapina sample shows the aspects of fibrocartilaginous ones. The morphology and anatomical pattern of this enthesis has already been established during growth in all three human groups. One of two and three of five adult femurs from El Sidrón and from Krapina, respectively, show the imprint of the vastus intermedius, which is absent among juveniles from those Neanderthal samples and in modern samples. The scant intrapopulation and the high interpopulation variability in the two Neanderthal samples is likely due to a long-term history of small, isolated populations with high levels of inbreeding, who also lived in different ecological conditions. The comparison of different anatomical entheseal patterns (fibrous vs. fibrocartilaginous) in the Neanderthals and modern humans provides additional elements in the discussion of their functional and genetic origin., This work is funded by the Spanish Ministry of Economy and Competitiveness: CGL2016-75109-P.

Fetal kicking and movements generate biomechanical stimulation in the fetal skeleton, which is important for prenatal musculoskeletal development, particularly joint shape. Developmental dysplasia of the hip (DDH) is the most common joint shape abnormality at birth, with many risk factors for the condition being associated with restricted fetal movement. In this study, we investigate the biomechanics of fetal movements in such situations, namely fetal breech position, oligohydramnios and primiparity (firstborn pregnancy). We also investigate twin pregnancies, which are not at greater risk of DDH incidence, despite the more restricted intra-uterine environment. We track fetal movements for each of these situations using cine-MRI technology, quantify the kick and muscle forces, and characterise the resulting stress and strain in the hip joint, testing the hypothesis that altered biomechanical stimuli may explain the link between certain intra-uterine conditions and risk of DDH. Kick force, stress and strain were found to be significantly lower in cases of breech position and oligohydramnios. Similarly, firstborn fetuses were found to generate significantly lower kick forces than non-firstborns. Interestingly, no significant difference was observed in twins compared to singletons. This research represents the first evidence of a link between the biomechanics of fetal movements and the risk of DDH, potentially informing the development of future preventative measures and enhanced diagnosis. Our results emphasise the importance of ultrasound screening for breech position and oligohydramnios, particularly later in pregnancy, and suggest that earlier intervention to correct breech position through external cephalic version could reduce the risk of hip dysplasia.

The search for talent is pervasive in youth sports. Selection/exclusion in many sports follows a maturity-related gradient largely during the interval of puberty and growth spurt. As such, there is emphasis on methods for assessing maturation. Commonly used methods for assessing status (skeletal age, secondary sex characteristics) and estimating timing (ages at peak height velocity (PHV) and menarche) in youth athletes and two relatively recent anthropometric (non-invasive) methods (status-percentage of predicted near adult height attained at observation, timing-predicted maturity offset/age at PHV) are described and evaluated. The latter methods need further validation with athletes. Currently available data on the maturity status and timing of youth athletes are subsequently summarised. Selection for sport and potential maturity-related correlates are then discussed in the context of talent development and associated models. Talent development from novice to elite is superimposed on a constantly changing base-the processes of physical growth, biological maturation and behavioural development, which occur simultaneously and interact with each other. The processes which are highly individualised also interact with the demands of a sport per se and with involved adults (coaches, trainers, administrators, parents/guardians).

BACKGROUND Somatosensory evoked potentials (SEPs) make it possible to obtain functional data on the activity of somatosensory pathway. OBJECTIVE To evaluate the ontogeny of electrical nerve conduction in male rhesus monkeys using SEPs in correlation with the development of the musculoskeletal system based on somatometry and musculoskeletal enzymes. METHODS Somatosensory evoked potentials of the medial and tibial nerves were performed, and somatometric measurements were obtained: total length, arm and forearm length, and thigh and calf length. Analysis of the musculoskeletal enzymes, lactic dehydrogenase, and creatininase was conducted using blood samples in 20 rhesus monkeys divided into 5 groups. RESULTS Statistical analysis manifested a delay in the appearance of latencies as age increased. Also evident was a strong, direct relation between the lengths and the value of the latencies of the SEP, together with an inverse relation between the musculoskeletal enzymes. CONCLUSIONS These findings contribute to standardizing this animal model in the neurophysiological sciences.

To investigate the impact of a selective reduction in dietary phosphorus (P) supply on healthy growing dogs, a total of 23 Beagles and 30 Foxhound crossbreds (FBI) were used in a feeding trial between 6 and 24 weeks of age. Sixteen Beagles and 19 FBI were fed with selectively reduced P concentrations (low phosphorus, LP). The remaining puppies received a completely balanced control diet (CON). With these diets, the P supply in the Beagles at the age of 12 weeks added up to 2.5 +/- 0.6 (LP) and 9.8 +/- 1.4 g P/kg DM (CON), and in the FBI 4.3 +/- 0.9 (LP) and 13.0 +/- 1.6 g P/kg DM (CON). Therefore, the LP Beagles received an average of 33 +/- 11% of the recommended daily allowances (RDA) of P, the LP FBI 41 +/- 11%. The calcium (Ca) concentration stayed unaltered and led to a Ca/P ratio above the recommended range of 1.3/1 to 2/1. The apparent digestibility (aD) of phosphorus was reduced in the LP Beagle;otherwise, the aD of both minerals was not affected by the P concentration of the diet. The renal excretion of P was reduced to zero in both LP groups while the renal calcium excretion increased significantly. Several of the puppies from both breeds showed impaired appetite, growth, skin and fur quality, and a few also clinically showed relevant signs of a disturbed musculoskeletal system after the LP feeding. A rapid loss of muscle strength and posture within hours led to severe deviation of the limb axis with hyperflexion of the joints but no radiological aberrations or signs of pain. Immediate transition of affected puppies to a balanced diet with sufficient phosphorus resulted in a complete recovery of the puppies in less than one month. The results demonstrate the importance of an adequate P supply on the healthy development of growing dogs.

Introduction The quantity and quality of scientific research within physiotherapy has unquestionably grown and matured over the last few decades, especially since the "formal" onset of evidence-based physiotherapy in the 1990s. The urgent need to evaluate our practice for effectiveness and efficiency has been responded to with thought and respect to both scientific integrity and shop-floor clinical needs. However, after thirty years or more of a professionally-governed and strategic approach to research activity, it is now timely to reflect, review, and consider the next chapter in the relationship between scientific research and clinical practice. Purpose This masterclass aims to develop a research vision for the future of physiotherapy. It is proposed that a crisis is evident within evidence-based physiotherapy, particular so given the assumed complexity and context-sensitivity of our clinical practice. This crisis period has highlighted fundamental limitations within the way research and practice are currently related. These limitations are presented and framed within the problematisation of empirical and philosophical concerns. As research becomes increasingly aligned to traditional scientific principles, examination of the real world context in which its outcomes are intended expose critical challenges for both research and clinical practice. Implications A reconceptualisation of fundamental elements of scientific research may allow more meaningful relationships between research and clinical practice. A proposed research vision encourages scientific activity to embrace real-world complexity in a way that it is presently unable to. An enhanced person-centered, scientifically-informed world of effective musculoskeletal practice is envisaged.

Transcriptional regulation can be tightly orchestrated by epigenetic regulators. Among these, ubiquitin-like with PHD and RING finger domains 1 (Uhrf1) is reported to have diverse epigenetic functions, including regulation of DNA methylation. However, the physiological functions of Uhrf1 in skeletal tissues remain unclear. Here we show that limb mesenchymal cell-specific Uhrf1 conditional knockout mice (Uhrf1ΔLimb/ΔLimb) exhibit remarkably shortened long bones that have morphological deformities due to dysregulated chondrocyte differentiation and proliferation. RNA-seq performed on primary cultured chondrocytes obtained from Uhrf1ΔLimb/ΔLimb mice showed abnormal chondrocyte differentiation. In addition, integrative analyses using RNA-seq and MBD-seq revealed that Uhrf1 deficiency decreased genome-wide DNA methylation and increased gene expression through reduced DNA methylation in the promoter regions of 28 genes, including Hspb1, which is reported to be an IL-1-related gene and to affect chondrocyte differentiation. Hspb1 knockdown in cKO chondrocytes can normalize abnormal expression of genes involved in chondrocyte differentiation such as Mmp13. These results indicate that Uhrf1 governs cell-type specific transcriptional regulation by controlling the genome-wide DNA methylation status and regulating consequent cell differentiation and skeletal maturation.

In order to recognize abnormalities on the physical evaluation, it is mandatory to understand normal developmental variations of the musculoskeletal system. Many abnormalities are self-limiting and, therefore, it is important to recognize which problems require intervention for a successful outcome and which may be complicated by treatment. The importance of a complete and thorough physical evaluation cannot be overemphasized and is the most productive diagnostic tool for recognizing most abnormalities of the skeletal system whether as a component of an after-foaling examination or for lameness or conformation evaluation in foals of all ages.

While there has been considerable progress in identifying molecular regulators of musculoskeletal development, the role of physical forces in regulating induction, differentiation, and patterning events is less well understood. Here, we highlight recent findings in this area, focusing primarily on model systems that test the mechanical regulation of skeletal and tendon development in the limb. We also discuss a few of the key signaling pathways and mechanisms that have been implicated in mechanotransduction and highlight current gaps in knowledge and opportunities for further research in the field.

Mustn1 is a specific musculoskeletal protein that plays a critical role in myogenesis and chondrogenesis in vertebrates. Whole-mount in situ hybridization revealed that mustn1b mRNAs are specifically expressed in skeletal and cardiac muscles in Zebrafish embryos. However, the precise function and the regulatory elements required for its muscle-specific expression are largely unknown.The purpose of this study was to explore and uncover the target genomic regions that regulate mustn1b gene expression by in vivo functional characterization of the mustn1b promoter. We report here stable expression analyses of eGFP from fluorescent transgenic reporter Zebrafish line containing a 0.8kb_mustn1b-Tol2-eGFP construct. eGFP expression was specifically found in the skeletal and cardiac muscle tissues. We show that reporter Zebrafish lines generated replicate the endogenous mustn1b expression pattern in early Zebrafish embryos. Specific site directed-mutagenesis analysis revealed that promoter activity resides in two annotated genomic regulatory regions, each one corresponding to a specific functional transcription factor binding site.Our data indicate that mustn1b is specifically expressed in skeletal and cardiac muscle tissues and its muscle specificity is controlled by the 0.2-kb promoter and flanking sequences and in vivo regulated by the action of two sequence-specific families of transcription factors. Developmental Dynamics 246:992-1000, 2017. © 2017 Wiley Periodicals, Inc.

Aside from its important role in blood clotting, vitamin K is an important dietary factor in regulating bone and cartilage mineralization. The vitamin K requirements to maintain musculoskeletal health may be more than the current recommendations and subclinical vitamin K deficiency may be involved in the pathogenesis of osteoporosis and osteoarthritis. Observational studies suggest that diets low in vitamin K are associated with increased risk of fractures and osteoarthritis in older adults. However, so far randomized controlled trials of vitamin K supplementation in Caucasian populations have not shown clinically significant improvements in bone mineral density at major skeletal sites. Supplementation with vitamin K may reduce the risk of fractures, but this conclusion comes from clinical trials with methodological limitations. At this time, only one randomized controlled trial has examined the effect of vitamin K supplementation on radiographic hand osteoarthritis and found no overall effect. Large well-designed randomized controlled trials are needed to compare the efficacies of vitamin K1 and K2 on fractures and osteoarthritis among older adults. In summary, currently there is not enough evidence to recommend the use of vitamin K supplements for the prevention of bone loss, fractures, or osteoarthritis in postmenopausal women.