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Human pluripotent stem cells (hPSCs) can provide a platform to model bone organogenesis and disease. To reflect the developmental process of the human skeleton, hPSC differentiation methods should include osteogenic progenitors (OPs) arising from three distinct embryonic lineages: the paraxial mesoderm, lateral plate mesoderm, and neural crest. Although OP differentiation protocols have been developed, the lineage from which they are derived, as well as characterization of their genetic and molecular differences, has not been well reported. Therefore, to generate lineage-specific OPs from human embryonic stem cells and human induced pluripotent stem cells, we employed stepwise differentiation of paraxial mesoderm-like cells, lateral plate mesoderm-like cells, and neural crest-like cells toward their respective OP subpopulation. Successful differentiation, confirmed through gene expression and in vivo assays, permitted the identification of transcriptomic signatures of all three cell populations. We also report, for the first time, high FGF1 levels in neural crest-derived OPs-a notable finding given the critical role of fibroblast growth factors (FGFs) in osteogenesis and mineral homeostasis. Our results indicate that FGF1 influences RUNX2 levels, with concomitant changes in ERK1/2 signaling. Overall, our study further validates hPSCs' power to model bone development and disease and reveals new, potentially important pathways influencing these processes.

Fibrous dysplasia (FD) is a mosaic skeletal disorder caused by somatic activating variants of GNAS encoding for Gαs and leading to excessive cyclic adenosine monophosphate signaling in bone-marrow stromal cells (BMSCs). The effect of Gαs activation in the BMSC transcriptome and how it influences FD lesion microenvironment are unclear. We analyzed changes induced by Gαs activation in the BMSC transcriptome and secretome. RNAseq analysis of differential gene expression of cultured BMSCs from patients with FD and healthy volunteers, and from an inducible mouse model of FD, was performed, and the transcriptomic profiles of both models were combined to build a robust FD BMSC genetic signature. Pathways related to Gαs activation, cytokine signaling, and extracellular matrix deposition were identified. To assess the modulation of several key secreted factors in FD pathogenesis, cytokines and other factors were measured in culture media. Cytokines were also screened in a collection of plasma samples from patients with FD, and positive correlations of several cytokines to their disease burden score, as well as to one another and bone turnover markers, were found. These data support the pro-inflammatory, pro-osteoclastic behavior of FD BMSCs and point to several cytokines and other secreted factors as possible therapeutic targets and/or circulating biomarkers for FD. [ABSTRACT FROM AUTHOR]

BACKGROUND:Bone marrow stromal cells (BMSCs) have classically been cultured in media supplemented with fetal bovine serum (FBS). As an alternative to FBS, pooled solvent detergent apheresis platelets, HPGF-C18, was evaluated for BMSC culture. METHODS:A comparison of passage 2 BMSC growth revealed that 10% HPGF-C18 produced similar cell numbers as 20% FBS. Marrow aspirates from 5 healthy subjects were cultured for 4 passages in 10% HPGF-C18 or 20% FBS and were analyzed for proliferation, colony formation efficiency (CFE), surface marker expression, suppression of mixed lymphocyte reactions (MLRs), global gene and microRNA expression analysis. BMSC supernatant cytokine and growth factor concentrations were also compared. RESULTS:Primary cultures of marrow aspirates in 10% HPGF-C18 and 20% FBS yielded similar numbers and CFE. After 4 passages, 10% HPGF-C18 and 20% FBS yielded similar numbers of BMSCs, surface marker expression patterns and immunosuppression effects. Gene and microRNA expression analysis revealed that BMSCs cultured under the two conditions had distinct expression profiles. Gene Set Enrichment Analysis (GSEA) revealed HPGF-C18-cultured BMSCs were enriched in metabolic processing and biosynthetic pathways, cell proliferation and cell cycle pathways, and immune response pathways. FBS-cultured BMSCs were enriched in MAPK signaling, TGF-beta signaling, cell adhesion and extracellular matrix pathways. Differently expressed microRNAs were related to the osteogenesis of BMSCs. The supernatant of HPGF-C18 BMSCs had higher levels of PEDF and TGFB1 and lower levels of IL6, VEGF, SDF1 and PLGF. CONCLUSIONS:Traditional measures, expansion, surface marker expression and inhibition of MLRs suggest that BMSC cultured in HPGF-C18 and FBS were similar, but analysis at the molecular level revealed many differences. BMSCs cultured in HPGF-C18 should be assessed in specific functional assays that reflect application-specific potency before substituting FBS with HPGF-C18.

WISP1/CCN4 (hereafter referred to as WISP1), a member of the CCN family, is found in mineralized tissues and is produced by osteoblasts and their precursors. In this study, Wisp1-deficient (Wisp1(-/-)) mice were generated. Using dual-energy x-ray absorptiometry, we showed that by 3 months, the total bone mineral density of Wisp1(-/-) mice was significantly lower than that of WT mice. Further investigation by micro-computed tomography showed that female Wisp1(-/-) mice had decreased trabecular bone volume/total volume and that both male and female Wisp1(-/-) mice had decreased cortical bone thickness accompanied by diminished biomechanical strength. The molecular basis for decreased bone mass in Wisp1(-/-) mice arises from reduced bone formation likely caused by osteogenic progenitors that differentiate poorly compared with WT cells. Osteoclast precursors from Wisp1(-/-) mice developed more tartrate-resistant acid phosphatase-positive cells in vitro and in transplants, suggesting that WISP1 is also a negative regulator of osteoclast differentiation. When bone turnover (formation and resorption) was induced by ovariectomy, Wisp1(-/-) mice had lower bone mineral density compared WT mice, confirming the potential for multiple roles for WISP1 in controlling bone homeostasis. Wisp1(-/-) bone marrow stromal cells had reduced expression of β-catenin and its target genes, potentially caused by WISP1 inhibition of SOST binding to LRP6. Taken together, our data suggest that the decreased bone mass found in Wisp1(-/-) mice could potentially be caused by an insufficiency in the osteodifferentiation capacity of bone marrow stromal cells arising from diminished Wnt signaling, ultimately leading to altered bone turnover and weaker biomechanically compromised bones.

Chondrogenic induction of bone-marrow-derived stromal cells (BMSCs) is typically accomplished with medium supplemented with growth factors (GF) from the transforming growth factor-beta (TGF-β)/bone morphogenetic factor (BMP) superfamily. In a previous study, we demonstrated that brief (1–3 days) stimulation with TGF-β1 was sufficient to drive chondrogenesis and hypertrophy using small-diameter microtissues generated from 5000 BMSC each. This biology is obfuscated in typical large-diameter pellet cultures, which suffer radial heterogeneity. Here, we investigated if brief stimulation (2 days) of BMSC microtissues with BMP-2 (100 ng/mL) or growth/differentiation factor (GDF-5, 100 ng/mL) was also sufficient to induce chondrogenic differentiation, in a manner comparable to TGF-β1 (10 ng/mL). Like TGF-β1, BMP-2 and GDF-5 are reported to stimulate chondrogenic differentiation of BMSCs, but the effects of transient or brief use in culture have not been explored. Hypertrophy is an unwanted outcome in BMSC chondrogenic differentiation that renders engineered tissues unsuitable for use in clinical cartilage repair. Using three BMSC donors, we observed that all GFs facilitated chondrogenesis, although the efficiency and the necessary duration of stimulation differed. Microtissues treated with 2 days or 14 days of TGF-β1 were both superior at producing extracellular matrix and expression of chondrogenic gene markers compared to BMP-2 and GDF-5 with the same exposure times. Hypertrophic markers increased proportionally with chondrogenic differentiation, suggesting that these processes are intertwined for all three GFs. The rapid action, or "temporal potency", of these GFs to induce BMSC chondrogenesis was found to be as follows: TGF-β1 > BMP-2 > GDF-5. Whether briefly or continuously supplied in culture, TGF-β1 was the most potent GF for inducing chondrogenesis in BMSCs. [ABSTRACT FROM AUTHOR]

Adoptive transfer of cultured BMSCs was shown to be immune-suppressive in various inflammatory settings. Many factors play a role in the process, but no master regulator of BMSC-driven immunomodulation was identified. Consequently, an assay that might predict BMSC product efficacy is still unavailable. Below, we show that BMSC donor variability can be monitored by IL-10 production of monocytes/macrophages using THP-1 cells (immortalized monocytic leukemia cells) co-cultured with BMSCs. Using a mixed lymphocyte reaction (MLR) assay, we also compared the ability of the different donor BMSCs to suppress T-cell proliferation, another measure of their immune-suppressive ability. We found that the BMSCs from a donor that induced the most IL-10 production were also the most efficient in suppressing T-cell proliferation. Transcriptome studies showed that the most potent BMSC batch also had higher expression of several known key immunomodulatory molecules such as hepatocyte growth factor (HGF), PDL1, and numerous members of the PGE2 pathway, including PTGS1 and TLR4. Multiplex ELISA experiments revealed higher expression of HGF and IL6 by the most potent BMSC donor. Based on these findings, we propose that THP-1 cells may be used to assess BMSC immunosuppressive activity as a product characterization assay. [ABSTRACT FROM AUTHOR]

Confusion about mesenchymal stem cells is making it easier for people to sell unproven treatments, warn Douglas Sipp, Pamela G. Robey and Leigh Turner.Confusion about mesenchymal stem cells is making it easier for people to sell unproven treatments, warn Douglas Sipp, Pamela G. Robey and Leigh Turner., Author(s): Douglas Sipp, Pamela G. Robey, Leigh TurnerAuthor Affiliations:Clear up this stem-cell mess Scanning electron micrograph of what is called a human mesenchymal stem cell, which some say can develop [...]

For bone marrow stromal cells (BMSC) to be useful in cartilage repair their propensity for hypertrophic differentiation must be overcome. A single day of TGF-β1 stimulation activates intrinsic signaling cascades in BMSCs which subsequently drives both chondrogenic and hypertrophic differentiation. TGF-β1 stimulation upregulates SP7, a transcription factor known to contribute to hypertrophic differentiation, and SP7 remains upregulated even if TGF-β1 is subsequently withdrawn from the chondrogenic induction medium. Herein, we stably transduced BMSCs to express an shRNA designed to silence SP7, and assess the capacity of SP7 silencing to mitigate hypertrophy. SP7 silencing dampened both hypertrophic and chondrogenic differentiation processes, resulting in diminished microtissue size, impaired glycosaminoglycan production and reduced chondrogenic and hypertrophic gene expression. Thus, while hypertrophic features were dampened by SP7 silencing, chondrogenic differentation was also compromised. We further investigated the role of SP7 in monolayer osteogenic and adipogenic cultures, finding that SP7 silencing dampened characteristic mineralization and lipid vacuole formation, respectively. Overall, SP7 silencing affects the trilineage differentiation of BMSCs, but is insufficient to decouple BMSC hypertrophy from chondrogenesis. These data highlight the challenge of promoting BMSC chondrogenesis whilst simultaneously reducing hypertrophy in cartilage tissue engineering strategies. [ABSTRACT FROM AUTHOR]

(1) Background: There are no high-throughput microtissue platforms for generating bone marrow micro-ossicles. Herein, we describe a method for the assembly of arrays of microtissues from bone marrow stromal cells (BMSC) in vitro and their maturation into bone marrow micro-ossicles in vivo. (2) Methods: Discs with arrays of 50 microwells were used to assemble microtissues from 3 × 105 BMSCs each on a nylon mesh carrier. Microtissues were cultured in chondrogenic induction medium followed by hypertrophic medium in an attempt to drive endochondral ossification, and then they were implanted in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice, where they were remodeled into bone marrow micro-ossicles. Mice were transplanted with 105 human umbilical cord blood CD34+ cells. (3) Results: Micro-ossicles contained more human CD45+ cells, but fewer human CD34+ progenitor cells than mouse marrow. Human hematopoietic progenitor cells cycle rapidly at non-physiological rates in mouse marrow, and reduced CD34+ cell content in micro-ossicles is consistent with the notion that the humanized niche better controls progenitor cell cycling. (4) Conclusions: Assembling microtissues in microwells, linked by a nylon membrane carrier, provides an elegant method to manufacture and handle arrays of microtissues with bone organ-like properties. More generally, this approach and platform could aid bridging the gap between in vitro microtissue manipulation and in vivo microtissue implantation. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) are the focus of intensive efforts worldwide directed not only at elucidating their nature and unique properties but also developing cell-based therapies for a diverse range of diseases. More than three decades have passed since the original formulation of the concept, revolutionary at the time, that multiple connective tissues could emanate from a common progenitor or stem cell retained in the postnatal bone marrow. Despite the many important advances made since that time, substantial ambiguities still plague the field regarding the nature, identity, function, mode of isolation and experimental handling of MSCs. These uncertainties have a major impact on their envisioned therapeutic use., Narrowing the focus on the stem cell Unbeknown to most readers of the copious literature dealing with both fundamental and clinical aspects of MSC biology, the current, widespread general concept [...]

Sepsis causes over 200,000 deaths yearly in the US; better treatments are urgently needed. Administering bone marrow stromal cells (BMSCs--also known as mesenchymal stem cells) to mice before or shortly after inducing sepsis by cecal ligation and puncture reduced mortality and improved organ function. The beneficial effect of BMSCs was eliminated by macrophage depletion or pretreatment with antibodies specific for interleukin-10 (IL-10) or IL-10 receptor. Monocytes and/or macrophages from septic lungs made more IL-10 when prepared from mice treated with BMSCs versus untreated mice. Lipopolysaccharide (LPS)-stimulated macrophages produced more IL-10 when cultured with BMSCs, but this effect was eliminated if the BMSCs lacked the genes encoding Toll-like receptor 4, myeloid differentiation primary response gene-88, tumor necrosis factor (TNF) receptor-1a or cyclooxygenase-2. Our results suggest that BMSCs (activated by LPS or TNF-[alpha]) reprogram macrophages by releasing prostaglandin E2 that acts on the macrophages through the prostaglandin EP2 and EP4 receptors. Because BMSCs have been successfully given to humans and can easily be cultured and might be used without human leukocyte antigen matching, we suggest that cultured, banked human BMSCs may be effective in treating sepsis in high-risk patient groups., Sepsis, a serious medical condition that affects 18 million people per year worldwide, is characterized by a generalized inflammatory state caused by infection. Widespread activation of inflammation and coagulation pathways [...]

Many patients with a bone disease called fibrous dysplasia may not need surgery to cut away bone growing around the optic nerve. This surgery is very risky and can cause blindness. In a study of 38 patients with fibrous dysplasia, all but two patients had normal vision even though most of them had bone growing around the optic nerve.

Abstract Background Bone marrow stromal cells (BMSCs) are being used to treat a variety of conditions. For many applications a supply of cryopreserved products that can be used for acute therapy is needed. The establishment of a bank of BMSC products from healthy third party donors is described. Methods The recruitment of healthy subjects willing to donate marrow for BMSC production and the Good Manufacturing Practices (GMP) used for assessing potential donors, collecting marrow, culturing BMSCs and BMSC cryopreservation are described. Results Seventeen subjects were enrolled in our marrow collection protocol for BMSC production. Six of the 17 subjects were found to be ineligible during the donor screening process and one became ill and their donation was cancelled. Approximately 12 ml of marrow was aspirated from one posterior iliac crest of 10 donors; one donor donated twice. The BMSCs were initially cultured in T-75 flasks and then expanded for three passages in multilayer cell factories. The final BMSC product was packaged into units of 100 × 106 viable cells, cryopreserved and stored in a vapor phase liquid nitrogen tank under continuous monitoring. BMSC products meeting all lot release criteria were obtained from 8 of the 11 marrow collections. The rate of growth of the primary cultures was similar for all products except those generated from the two oldest donors. One lot did not meet the criteria for final release; its CD34 antigen expression was greater than the cut off set at 5%. The mean number of BMSC units obtained from each donor was 17 and ranged from 3 to 40. Conclusions The production of large numbers of BMSCs from bone marrow aspirates of healthy donors is feasible, but is limited by the high number of donors that did not meet eligibility criteria and products that did not meet lot release criteria.

Bone marrow stromal or stem cells (BMSCs) remain a promising potential therapy for ischemic cardiomyopathy. The primary objective of this study was to evaluate the safety and feasibility of direct intramyocardial injection of autologous BMSCs in patients undergoing transmyocardial revascularization (TMR) or coronary artery bypass graft surgery (CABG). A phase I trial was conducted on adult patients who had ischemic heart disease with depressed left ventricular ejection fraction and who were scheduled to undergo TMR or CABG. Autologous BMSCs were expanded for 3 weeks before the scheduled surgery. After completion of surgical revascularization, BMSCs were directly injected into ischemic myocardium. Safety and feasibility of therapy were assessed. Cardiac functional status and changes in quality of life were evaluated at 1 year. A total of 14 patients underwent simultaneous BMSC and surgical revascularization therapy (TMR+BMSCs = 10; CABG+BMSCs = 4). BMSCs were successfully expanded, and no significant complications occurred as a result of the procedure. Regional contractility in the cell-treated areas demonstrated improvement at 12 months compared with baseline (TMR+BMSCs Δ strain: −4.6% ± 2.1%; P =.02; CABG+MSCs Δ strain: −4.2% ± 6.0%; P =.30). Quality of life was enhanced, with substantial reduction in angina scores at 1 year after treatment (TMR+BMSCs: 1.3 ± 1.2; CABG+MSCs: 1.0 ± 1.4). In this phase I trial, direct intramyocardial injection of autologous BMSCs in conjunction with TMR or CABG was technically feasible and could be performed safely. Preliminary results demonstrate improved cardiac function and quality of life in patients at 1 year after treatment. [ABSTRACT FROM AUTHOR]

Fibrous dysplasia (FD) of bone is a complex disease of the skeleton caused by dominant activating mutations of the GNAS locus encoding for the α subunit of the G protein-coupled receptor complex (Gsα). The mutation involves a substitution of arginine at position 201 by histidine or cysteine (GsαR201H or R201C), which leads to overproduction of cAMP. Several signaling pathways are implicated downstream of excess cAMP in the manifestation of disease. However, the pathogenesis of FD remains largely unknown. The overall FD phenotype can be attributed to alterations of skeletal stem/progenitor cells which normally develop into osteogenic or adipogenic cells (in cis), and are also known to provide support to angiogenesis, hematopoiesis, and osteoclastogenesis (in trans). In order to dissect the molecular pathways rooted in skeletal stem/progenitor cells by FD mutations, we engineered human skeletal stem/progenitor cells with the GsαR201C mutation and performed transcriptomic analysis. Our data suggest that this FD mutation profoundly alters the properties of skeletal stem/progenitor cells by pushing them towards formation of disorganized bone with a concomitant alteration of adipogenic differentiation. In addition, the mutation creates an altered in trans environment that induces neovascularization, cytokine/chemokine changes and osteoclastogenesis. In silico comparison of our data with the signature of FD craniofacial samples highlighted common traits, such as the upregulation of ADAM (A Disintegrin and Metalloprotease) proteins and other matrix-related factors, and of PDE7B (Phosphodiesterase 7B), which can be considered as a buffering process, activated to compensate for excess cAMP. We also observed high levels of CEBPs (CCAAT-Enhancer Binding Proteins) in both data sets, factors related to browning of white fat. This is the first analysis of the reaction of human skeletal stem/progenitor cells to the introduction of the FD mutation and we believe it provides a useful background for further studies on the molecular basis of the disease and for the identification of novel potential therapeutic targets. [ABSTRACT FROM AUTHOR]