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Significance: Impaired wound healing is a major complication of diabetes, and can lead to development of chronic foot ulcers in a significant number of patients. Despite the danger posed by poor healing, very few specific therapies exist, leaving patients at risk of hospitalization, amputation, and further decline in overall health. Recent Advances: Redox signaling is a key regulator of wound healing, especially through its influence on the extracellular matrix (ECM). Normal redox signaling is disrupted in diabetes leading to several pathological mechanisms that alter the balance between reactive oxygen species (ROS) generation and scavenging. Importantly, pathological oxidative stress can alter ECM structure and function. Critical Issues: There is limited understanding of the specific role of altered redox signaling in the diabetic wound, although there is evidence that ROS are involved in the underlying pathology. Future Directions: Preclinical studies of antioxidant-based therapies for diabetic wound healing have yielded promising results. Redox-based therapeutics constitute a novel approach for the treatment of wounds in diabetes patients that deserve further investigation. Antioxid. Redox Signal. 27, 823-838. [ABSTRACT FROM AUTHOR]

Extracellular matrix is composed of a complex array of molecules that together provide structural and functional support to cells. These properties are mainly mediated by the activity of collagenous and elastic fibers, proteoglycans, and proteins such as fibronectin and laminin. ECM composition is tissue-specific and could include matricellular proteins whose primary role is to modulate cell–matrix interactions. In adults, matricellular proteins are primarily expressed during injury, inflammation and disease. Particularly, they are closely associated with the progression and prognosis of cardiovascular and fibrotic diseases, and cancer. This review aims to provide an overview of the potential use of matricellular proteins in drug delivery including the generation of therapeutic agents based on the properties and structures of these proteins as well as their utility as biomarkers for specific diseases. [ABSTRACT FROM AUTHOR]

Biomaterials are essential to modern medicine as components of reconstructive implants, implantable sensors, and vehicles for localized drug delivery. Advances in biomaterials have led to progression from simply making implants that are nontoxic to making implants that are specifically designed to elicit particular functions within the host. The interaction of implants and the extracellular matrix during the foreign body response is a growing area of concern for the field of biomaterials, because it can lead to implant failure. Expression of matricellular proteins is modulated during the foreign body response and these proteins interact with biomaterials. The design of biomaterials to specifically alter the levels of matricellular proteins surrounding implants provides a new avenue for the design and fabrication of biomimetic biomaterials. [ABSTRACT FROM AUTHOR]

Abstract: Despite many successful applications of microelectrode arrays (MEAs), typical two-dimensional in-vitro cultures do not project the full scale of the cell growth environment in the three-dimensional (3D) in-vivo setting. This study aims to on-line monitor in-vitro cell growth in a 3D matrix on the surface-modified MEAs with a dynamic perfusion culture system. A 3D matrix consisting of poly(ethylene glycol) hydrogel supplemented with poly-d-lysine was subsequently synthesized in situ on the self-assembled monolayer modified MEAs. FTIR spectrum analysis revealed a peak at 2100cm−1 due to the degradation of the structure of the 3D matrix. After 2 wks, microscopic examination revealed that the non-degraded area was around 1500μm2 and provided enough space for cell growth. Fluorescence microscopy revealed that the degraded 3D matrix was non-cytotoxic allowing the growth of NIH3T3 fibroblasts and cortical neurons in vitro. Time-course changes of total impedance including resistance and reactance were recorded for 8 days to evaluate the cell growth in the 3D matrix on the MEA. A consistent trend reflecting changes of reactance and total impedance was observed. These in-vitro assays demonstrate that our 3D matrix can construct a biomimetic system for cell growth and analysis of cell surface interactions. [Copyright &y& Elsevier]

Abstract: Matrix metalloproteinases (MMPs) are enzymes with specificity towards extracellular matrix (ECM) components. MMPs, especially MMP-9, have been shown to degrade components of the basal lamina and disrupt the blood-brain barrier (BBB) and thus, contribute to neuroinflammation. In the present study we examined the role of MMP-9 in the foreign body response in the brain. Millipore filters of mixed cellulose ester were implanted into the brain cortex of wild type and MMP-9-null mice for a period of 2 d to 8 wks and the response was analyzed by histology and immunohistochemistry. We observed enhanced and prolonged neuroinflammation in MMP-9-null mice, evidenced by persistence of neutrophils, macrophages/microglia, and reactive astrocytes up to 8 wks post-implantation. In addition, blood vessel density around implants was increased in MMP-9-null mice and detection of mouse serum albumin (MSA) indicated that vessels were leaky. Immunohistochemical and western blot analyses indicated that this defect was associated with the absence of tight junction proteins zonula occludens-1 (ZO-1) and ZO-2 from vessels in proximity to implants. Analysis of brain sections and brain protein extracts revealed that the levels of the pro-inflammatory cytokine interleukin-1β (IL-1β), which is a substrate for MMP-9, were significantly higher in MMP-9-null mice at 8wks post-implantation. Collectively, our studies suggest that increased levels of IL-1β and the delayed repair of BBB are associated with prolongation of the FBR in MMP-9-null mice. [Copyright &y& Elsevier]

Abstract: Matrix metalloproteinase- (MMP-9) is involved in processes that occur during cutaneous wound healing such as inflammation, matrix remodeling, and epithelialization, To investigate its role in healing, full thickness skin wounds were made in the dorsal region of MMP-9-null and control mice and harvested up to 14 days post wounding. Gross examination and histological and immunohistochemical analysis indicated delayed healing in MMP-9-null mice. Specifically, MMP-9-null wounds displayed compromised reepithelialization and reduced clearance of fibrin clots. In addition, they exhibited abnormal matrix deposition, as evidenced by the irregular alignment of immature collagen fibers. Despite the presence of matrix abnormalities, MMP-9-null wounds displayed normal tensile strength. Ultrastructural analysis of wounds revealed the presence of large collagen fibrils, some with irregular shape. Keratinocyte proliferation, inflammation, and angiogenesis were found to be normal in MMP-9-null wounds. In addition, VEGF levels were similar in control and MMP-9-null wound extracts. To investigate the importance of MMP-9 in wound reepithelialization we tested human and murine keratinocytes in a wound migration assay and found that antibody-based blockade of MMP-9 function or MMP-9 deficiency retarded migration. Collectively, our observations reveal defective healing in MMP-9-null mice and suggest that MMP-9 is required for normal progression of wound closure. [Copyright &y& Elsevier]

The inhibitor of angiogenesis, thrombospondin 2 (TSP2), belongs to a group of matricellular proteins that are induced in response to injury and modulate the healing of dermal wounds. Thus, TSP-2-null mice display abnormal connective tissue architecture and increased angiogenesis in the dermis, and heal wounds at an accelerated rate. In this study, we report that the content of TSP2 is increased in the uninjured skin of aged mice. Furthermore, in primary dermal fibroblasts, TSP2 expression is increased both as a function of the age of the donor and days in culture. To determine the significance of the increased TSP2 in aged mice (two years or older), we performed full-thickness excisional wounds and compared their healing in aged and young (3–4 months) wild-type and TSP2-null mice. Gross morphological examination of wounds indicated that aged TSP2-null mice healed faster than their aged wild-type counterparts, but healing in aged mice was always sub-optimal in comparison to that in young animals. Surprisingly, despite the increase in TSP2, a potent inhibitor of angiogenesis, in wounds in aged mice, the vascular density of these wounds was not reduced in comparison to that in young animals. However, immunohistochemical analysis of healing wounds revealed a shift in the peak content of TSP2, from day 10 in young mice to day 14 or later in aged mice, and there was a corresponding delay in the expected increase in matrix metalloproteinase (MMP) 2 levels in aged TSP2-null mice. We suggest that the delay in expression of TSP2 and MMP2 in the wounds of aged mice could contribute to their impaired rate of wound healing. [Copyright &y& Elsevier]

Presents information on a study which demonstrated that the foreign body reaction might be altered in thrombospondin 2-null mice. Materials and methods; Results and discussion.

Focuses on a study which disrupted the thrombospondin 2 (Thbs2) gene in murine embryonic stem cells and generated homozygous TSP2 -null mice in an effort to determine the biological role of TSP2. Materials and methods used to conduct this study; Generation of TSP2-null mice; Indication that TSP2-null mice exhibit a striking abnormality in skin; Results and discussion of the study.

Impaired wound healing in diabetic patients is the leading cause of diabetes‐associated hospitalizations and approximately 50% of lower limb amputations. This is due to multiple factors, including elevated glucose, sustained hypoxia, and cell dysfunction. Previously, diabetic wounds were found to contain excessive levels of the matricellular protein thrombospondin‐2 (TSP2) and genetic ablation of TSP2 in diabetic mice or treatment of wounds with a hydrogel derived from TSP2‐null mouse skin improved healing. Previously, TSP2 has been shown to be repressed by hypoxia, but in the present study we observed sustained hypoxia and overlapping TSP2 deposition in diabetic wounds. We determined this observation was due to the insufficient HIF‐1α activation verified by western blot and immunofluorescent analysis of wound tissues and in vitro hypoxia experiments. Application of Dimethyloxalylglycine (DMOG), which can stabilize HIF‐1α, inhibited TSP2 expression in diabetic fibroblasts in hypoxic conditions. Therefore, we prepared DMOG‐containing TSP2KO hydrogel and applied it to the wounds of diabetic mice. In comparison to empty TSP2KO hydrogel or DMOG treatment, we observed improved wound healing associated with a reduction of TSP2, reduced hypoxia, and increased neovascularization. Overall, our findings shed light on the intricate interplay between hyperglycemia, hypoxia, and TSP2 in the complex environment of diabetic wounds. [ABSTRACT FROM AUTHOR]

The biggest challenge in current isolation methods for lipid bilayer‐encapsulated vesicles, such as exosomes, secretory, and synthetic vesicles, lies in the absence of a unified approach that seamlessly delivers high purity, yield, and scalability for large‐scale applications. To address this gap, an innovative method is developed that utilizes photosensitive lipid nanoprobes for the efficient isolation of vesicles and sorting them into subpopulations based on size. The photosensitive component in the probe undergoes cleavage upon exposure to light, facilitating the release of vesicles in their near‐native form. The method demonstrates a superior ability in isolating high purity extracellular vesicles from complex biological media and separating them into size‐based subpopulations within 1 h, achieving more efficiency and purity than ultracentrifugation. Furthermore, this method's cost‐effectiveness and rapid enrichment of the vesicles align with demands for large‐scale isolation and downstream analyses of nucleic acids and proteins. The method opens new avenues in exploring, analyzing, and utilizing synthetic and extracellular vesicle subpopulations in various biomedical applications, including diagnostics, therapeutic delivery, and biomarker discovery. [ABSTRACT FROM AUTHOR]

• Creation and characterization of muscle-derived extracellular matrix hydrogels from TSP2 KO mice shows altered composition, assembly, and biomechanical properties when compared to WT. • TSP2 KO hydrogels allow greater myocyte spreading and invasion as well increased tube formation by endothelial cells in vitro. • In vivo study showed excellent foreign body response of TSP2 KO hydrogels associated with enhanced cell invasion, innervation, and angiogenesis. • TSP2 KO hydrogels were used to treat VML injury in mice and were found to induce greater recruitment of repair cells and enhanced tissue remodeling. Volumetric muscle loss (VML) represents a clinical challenge due to the limited regenerative capacity of skeletal muscle. Most often, it results in scar tissue formation and loss of function, which cannot be prevented by current therapies. Decellularized extracellular matrix (DEM) has emerged as a native biomaterial for the enhancement of tissue repair. Here, we report the generation and characterization of hydrogels derived from DEM prepared from WT or thrombospondin (TSP)-2 null muscle tissue. TSP2-null hydrogels, when compared to WT, displayed altered architecture, protein composition, and biomechanical properties and allowed enhanced invasion of C2C12 myocytes and chord formation by endothelial cells. They also displayed enhanced cell invasion, innervation, and angiogenesis following subcutaneous implantation. To evaluate their regenerative capacity, WT or TSP2 null hydrogels were used to treat VML injury to tibialis anterior muscles and the latter induced greater recruitment of repair cells, innervation, and blood vessel formation and reduced inflammation. Taken together, these observations indicate that TSP2-null hydrogels enhance angiogenesis and promote muscle repair in a VML model. [ABSTRACT FROM AUTHOR]

Each year, hundreds of thousands coronary bypass procedures are performed in the US, yet there currently exists no off-the-shelf alternative to autologous vessel transplant. In the present study, we investigated the use of mouse thrombospondin-2 knockout (TSP2 KO) cells, which secrete a non-thrombogenic and pro-migratory extracellular matrix (TSP2 KO ECM), to modify small diameter vascular grafts. To accomplish this, we first optimized the incorporation of TSP2 KO ECM on decellularized rat aortas. Because MMP levels are known to be elevated in TSP2 KO cell culture, it was necessary to probe the effect of the modification process on the graft's mechanical properties. However, no differences were found in suture retention, Young's modulus, or ultimate tensile strength between modified and unmodified grafts. Platelet studies were then performed to determine the time point at which the TSP2 KO ECM sufficiently reduced thrombogenicity. Finally, grafts modified by either TSP2 KO or WT cells or unmodified grafts, were implanted in an abdominal aortic interposition model in rats. After 4 weeks, grafts with incorporated TSP2 KO ECM showed improved endothelial and mural cell recruitment, and a decreased failure rate compared to control grafts. Therefore, our studies show that TSP2 KO ECM could enable the production of off-the-shelf vascular grafts while promoting reconstruction of native vessels. [ABSTRACT FROM AUTHOR]

The extracellular matrix (ECM) protein thrombospondin 2 (TSP2) functions as matricellular protein by modulating cell-ECM interactions. Studies in TSP2-null mice have demonstrated increased angiogenesis in several tissues, especially after injury to tissues. In the present study, we evaluated the ability of TSP2-null mice to respond to ischemia in the hindlimb for a period of 4 wks following excision of the left femoral artery. Measurements of blood flow indicated that, when compared to littermate control mice, TSP2-null mice recovered at an accelerated rate. The observed changes correlated with the temporal expression of TSP2 in ischemic muscle from control mice. Immunohistochemical analysis revealed a dramatic increase in angiogenesis in the TSP2-null ischemic muscle and elevated deposition of MMP9. The latter was confirmed by zymography and western blot of muscle protein extracts. Furthermore, TSP2-null mice displayed increased arteriogenesis determined by angiography. Taken together, our observations implicate TSP2 as an inhibitor of angiogenesis and arteriogenesis in ischemia. [ABSTRACT FROM AUTHOR]

Mice that lack the extracellular matrix protein thrombospondin 2 have, among several abnormalities, an increase in vascular density, abnormal collagen fibrils, and dermal fibroblasts that are defective in adhesion. These findings suggested that responses involving these processes, such as wound healing, might be altered. To investigate the healing process, excisional wounds were made with the aid of a biopsy punch. Such wounds, observed over a 14 d period, appeared to heal at an accelerated rate and with less scarring in thrombospondin 2-null mice. Histologic analysis of thrombospondin 2-null wound sites revealed the presence of an irregularly organized and highly vascularized granulation tissue. In addition, thrombospondin 2-null wounds retained a higher total cellular content, than control wounds. No differences in wound re-epithelization rates were observed, but thrombospondin 2-null epithelia formed rete pegs and were thicker than control epithelia. By immunohistochemistry, we detected elevated levels and an irregular deposition pattern for fibronectin in thrombospondin 2-null wounds, observations that correlated with the abnormal collagen organization in the granulation tissue. Immunostaining for thrombospondin 2 in control wounds showed that the protein is present in both early and late wounds, in a scattered cell-associated pattern or widely distributed cell- and matrix-associated pattern, respectively. Our results suggest that thrombospondin 2 plays a crucial part in the organization and vascularization of the granulation tissue during healing, possibly by modulating fibroblast–matrix interactions in early wounds and regulating the extent of angiogenesis in late wounds. [ABSTRACT FROM AUTHOR]

Fibroblasts are a major cell population that perform critical functions in the wound healing process. In response to injury, they proliferate and migrate into the wound space, engaging in extracellular matrix (ECM) production, remodeling, and contraction. However, there is limited knowledge of how fibroblast functions are altered in diabetes. To address this gap, several state-of-the-art microscopy techniques were employed to investigate morphology, migration, ECM production, 2D traction, 3D contraction, and cell stiffness. Analysis of cell-derived matrix (CDM) revealed that diabetic fibroblasts produce thickened and less porous ECM that hindered migration of normal fibroblasts. In addition, diabetic fibroblasts were found to lose spindle-like shape, migrate slower, generate less traction force, exert limited 3D contractility, and have increased cell stiffness. These changes were due, in part, to a decreased level of active Rac1 and a lack of co-localization between F-actin and Waskott-Aldrich syndrome protein family verprolin homologous protein 2 (WAVE2). Interestingly, deletion of thrombospondin-2 (TSP2) in diabetic fibroblasts rescued these phenotypes and restored normal levels of active Rac1 and WAVE2-F-actin co-localization. These results provide a comprehensive view of the extent of diabetic fibroblast dysfunction, highlighting the regulatory role of the TSP2-Rac1-WAVE2-actin axis, and describing a new function of TSP2 in regulating cytoskeleton organization. [ABSTRACT FROM AUTHOR]

Abstract: Background: Numerous proteins and small leucine-rich proteoglycans (SLRPs) make up the composition of the extracellular matrix (ECM). Assembly of individual fibrillar components in the ECM, such as collagen, elastin, and fibronectin, is understood at the molecular level. In contrast, the incorporation of non-fibrillar components and their functions in the ECM are not fully understood. Scope of review: This review will focus on the role of the matricellular protein thrombospondin (TSP) 2 in ECM assembly. Based on findings in TSP2-null mice and in vitro studies, we describe the participation of TSP2 in ECM assembly, cell–ECM interactions, and modulation of the levels of matrix metalloproteinases (MMPs). Major conclusions: Evidence summarized in this review suggests that TSP2 can influence collagen fibrillogenesis without being an integral component of fibrils. Altered ECM assembly and excessive breakdown of ECM can have both positive and negative consequences including increased angiogenesis during tissue repair and compromised cardiac tissue integrity, respectively. General significance: Proper ECM assembly is critical for maintaining cell functions and providing structural support. Lack of TSP2 is associated with increased angiogenesis, in part, due to altered endothelial cell–ECM interactions. Therefore, minor changes in ECM composition can have profound effects on cell and tissue function. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties. [Copyright &y& Elsevier]

Thrombospondins (TSPs) 1 and 2 are extracellular modular glycoproteins that are best known for their anti-angiogenic properties and their ability to modulate cell–matrix interactions. However, these proteins, and in particular TSP2, are pleiotropic in function and affect processes as disparate as bone growth and hemostasis. In recognition of their ability to influence a wide variety of cell functions, and in the absence of convincing evidence for their participation as integral components of extracellular structures, the term ‘matricellular’ has been applied to these and a small group of functionally related proteins. In this review, we focus on the role of TSP1 and 2 in two forms of injury in mice, excisional skin wounds and subcutaneously implanted biomaterials, and take advantage of mice with targeted disruptions of one or both genes to identify likely biochemical mechanisms that could account for the characteristics of the injury response in these knockout mice. In work that stems largely from our own laboratory, we show that pericellular levels of the matrix metalloproteinase, MMP2, are controlled to a large extent by TSP2 (and potentially also by TSP1), and that elevated levels of MMP2 are likely to account in part for defects as diverse as reduced cellular adhesion, abnormal collagen fibril structure, and increased endothelial cell and vascular proliferation. [Copyright &y& Elsevier]

In the article "Photosensitive Nanoprobes for Rapid High Purity Isolation and Size-Specific Enrichment of Synthetic and Extracellular Vesicle Subpopulations," researchers Roshan W. Gunasekara, Sathish Ramakrishnan, and their team introduce photosensitive lipid nanoprobes that can isolate extracellular vesicles with high purity while preserving their natural state and functionality. These nanoprobes use hydrophobic interactions and photochemistry to separate vesicles into subpopulations based on size. This ability to isolate vesicles of different sizes is valuable for studying vesicle biogenesis and engineering uniform vesicle populations. [Extracted from the article]

Infection is a devastating complication following an open fracture. We investigated whether local rifampin‐loaded hydrogel can combat infection and improve healing in a murine model of methicillin‐resistant Staphylococcus aureus (MRSA) osteomyelitis. A transverse fracture was made at the tibia midshaft of C57BL/6J mice aged 10–12 weeks and stabilized with an intramedullary pin. A total of 1 × 106 colony‐forming units (CFU) of MRSA was inoculated. A collagen‐based hydrogel containing low‐dose (60 μg) and high‐dose (300 μg) rifampin was applied before closure. Postoperative treatment response was assessed through bacterial CFU counts from tissue and hardware, tibial radiographs and microcomputed tomography (μCT), immunohistochemistry, and histological analyses. All untreated MRSA‐infected fractures progressed to nonunion by 28 days with profuse MRSA colonization. Infected fractures demonstrated decreased soft callus formation on safranin O stain compared to controls. Areas of dense interleukin‐1β stain were associated with poor callus formation. High‐dose rifampin hydrogels reduced the average MRSA load in tissue (p < 0.0001) and implants (p = 0.041). Low‐dose rifampin hydrogels reduced tissue bacterial load by 50% (p = 0.021). Among sterile models, 88% achieved union compared to 0% of those infected. Mean radiographic union scale in tibia scores improved from 6 to 8.7 with high‐dose rifampin hydrogel (p = 0.024) and to 10 with combination local/systemic rifampin therapy (p < 0.0001). μCT demonstrated reactive bone formation in MRSA infection. Histology demonstrated restored fracture healing with bacterial elimination. Rifampin‐loaded hydrogels suppressed osteomyelitis, prevented implant colonization, and improved healing. Systemic rifampin was more effective at eliminating infection and improving fracture healing. Further investigation into rifampin‐loaded hydrogels is required to correlate these findings with clinical efficacy. [ABSTRACT FROM AUTHOR]

Novel biological vascular conduits, such as decellularized tissue engineered vascular grafts (TEVGs) are hindered by high thrombogenicity. To mimic the antithrombogenic surface of native vessels with a continuous glycosaminoglycan layer that is present on endothelial cells (ECs), a hyaluronic acid (HA) modified surface is established, to effectively shield blood platelets from collagen‐triggered activation. Using the amine groups present on 4 mm diameter decellularized TEVGs, a continuous HA hydrogel coating is built via a bifunctional thiol‐reactive cross‐linker, thereby avoiding nonspecific collagen matrix cross‐linking. The HA hydrogel layer recreates a luminal wall, "hiding" exposed collagen from the bloodstream. In vitro blood tests show that adhered platelets, fibrinogen absorption, and fibrin formation on HA‐coated decellularized TEVGs are significantly lower than on uncoated decellularized TEVGs. The HA surface also inhibits macrophage adhesion in vitro. HA‐coated decellularized syngeneic rat aortae (≈1.5 mm diameter), and TEVGs in rat and canine models, respectively, are protected from aggressive thrombus formation, and preserve normal blood flow. Re‐endothelialization is also observed. HA‐coated TEVGs may be an off‐the‐shelf small‐diameter vascular graft with dual benefits: antithrombogenic protection and promotion of endothelium. [ABSTRACT FROM AUTHOR]

Impaired wound healing is a major complication of diabetes, and despite the associated risks, treatment strategies for diabetic wounds remain limited. This is due, in part, to an incomplete understanding of the underlying pathological mechanisms, including the effects of hyperglycemia on components of the extracellular matrix (ECM). In the current study, we explored whether the expression of thrombospondin 2 (TSP2), a matricellular protein with a demonstrated role in response to injury, was associated with delayed healing in diabetes. First, we found that TSP2 expression was elevated in diabetic mice and skin from patients with diabetes. Then, to determine the contribution of TSP2 to impaired healing in diabetes, we developed a novel diabetic TSP2-deficient model. Though the TSP2-deficient mice developed obesity and hyperglycemia comparable with diabetic control mice, they exhibited significantly improved healing, characterized by accelerated reepithelialization and increased granulation tissue formation, fibroblast migration, and blood vessel maturation. We further found that hyperglycemia increased TSP2 expression in fibroblasts, the major cellular source of TSP2 in wounds. Mechanistically, high glucose increased activation of the hexosamine pathway and nuclear factor-κB signaling to elevate TSP2 expression. Our studies demonstrate that hyperglycemia-induced TSP2 expression contributes to impaired healing in diabetes. [ABSTRACT FROM AUTHOR]

Decellularized biologic scaffolds are gaining popularity over synthetic biomaterials as naturally derived materials capable of promoting improved healing. Nevertheless, the most widely used biologic material – acellular dermal matrix (ADM) – exhibits slow repopulation and remodeling, which prevents integration. Additionally, engineering control of these materials is limited because they require a natural source for their production. In the current report, we demonstrate the feasibility of using genetically engineered animals to create decellularized biologic scaffolds with favorable extracellular matrix (ECM) properties. Specifically, we utilized skin from thrombospondin (TSP)-2 KO mice to derive various decellularized products. Scanning electron microscopy and mechanical testing showed that TSP-2 KO ADM exhibited an altered structure and a reduction in elastic modulus and ultimate tensile strength, respectively. When a powdered form of KO ADM was implanted subcutaneously, it was able to promote enhanced vascularization over WT. Additionally, when implanted subcutaneously, intact slabs of KO ADM were populated by higher number of host cells when compared to WT. In vitro studies confirmed the promigratory properties of KO ADM. Specifically, degradation products released by pepsin digestion of KO ADM induced greater cell migration than WT. Moreover, cell-derived ECM from TSP-2 null fibroblasts was more permissive to fibroblast migration. Finally, ADMs were implanted in a diabetic wound model to examine their ability to accelerate wound healing. KO ADM exhibited enhanced remodeling and vascular maturation, indicative of efficient integration. Overall, we demonstrate that genetic manipulation enables engineered ECM-based materials with increased regenerative potential. [ABSTRACT FROM AUTHOR]

Thrombospondin-2 (TSP2) is a potent inhibitor of angiogenesis whose expression is dynamically regulated following injury. In the present study, it is shown that HIF-1α represses TSP2 transcription. Specifically, in vitro studies demonstrate that the prolyl hydroxylase inhibitor DMOG or hypoxia decrease TSP2 expression in fibroblasts. This effect is shown to be via a transcriptional mechanism as hypoxia does not alter TSP2 mRNA stability and this effect requires the TSP2 promoter. In addition, the documented repressive effect of nitric oxide (NO) on TSP2 is shown to be non-canonical and involves stabilization of hypoxia inducible factor-1a (HIF-1α). The regulation of TSP2 by hypoxia is supported by the in vivo observation that TSP2 has spatiotemporal expression distinct from regions of hypoxia in gastrocnemius muscle following murine hindlimb ischemia (HLI). A role for TSP2 regulation by HIF-1α is supported by the dysregulation of TSP2 expression in SM22α-cre HIF-1α KO mice following HLI. Indeed, there is a reduction in blood flow recovery in the SM22a-cre HIF-1α KO mice compared to littermate controls following HLI surgery, associated with impaired recovery and increased TSP2 levels. Moreover, SM22α-cre HIF-1α KO smooth muscle cells mice have increased TSP2 mRNA levels that persist in hypoxia. These findings identify a novel, ischemia-induced pro-angiogenic mechanism involving the transcriptional repression of TSP2 by HIF-1α. [ABSTRACT FROM AUTHOR]

In order to bypass the limitation of bulk metallic glasses fabrication, we synthesized thin film metallic glasses to study the corrosion characteristics of a wide atomic% composition range, Mg(35.9–63%)Ca(4.1–21%)Zn(17.9–58.3%), in simulated body fluid. We highlight a clear relationship between Zn content and corrosion current such that Zn-medium metallic glasses exhibit minimum corrosion. In addition, we found higher Zn content leads to a poor in vitro cell viability. These results showcase the benefit of evaluating a larger alloy compositional space to probe the limits of corrosion resistance and prescreen for biocompatible applications. [ABSTRACT FROM AUTHOR]

"This works was funded by National Institutes of Health (Grant nos. Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-022-26337-1, published online 28 December 2022 The Funding section in the original version of this Article was incomplete. [Extracted from the article]

"This works was funded by National Institutes of Health (Grant nos. Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-022-26337-1, published online 28 December 2022 The Funding section in the original version of this Article was incomplete. [Extracted from the article]

Interactions between collagenous extracellular matrices and von Willebrand factor (VWF) are critical for hemostasis and thrombosis. In the present study, we investigated the contribution of an extracellular matrix (ECM) abnormality to the bleeding diathesis in thrombospondin-2 (TSP2) knockout (KO) mice. First, we performed adoptive bone marrow transplantation and observed that introduction of wild-type (WT) marrow into lethally irradiated TSP2 KO mice did not rescue the bleeding diathesis. However, platelets in transplanted mice displayed an inherent aggregation defect, which complicated interpretation. Second, we performed interposition of arterial segments denuded of endothelium. Denuded TSP2 KO arteries grafted into WT mice remained patent in vivo. In contrast, WT grafts underwent thrombosis and were completely occluded within 24 to 48 hours. The nonthrombogenic property of the TSP2 KO ECM was confirmed in vitro by exposing platelets to TSP2 KO dermal fibroblast (DF)-derived ECM. To further probe the effect of TSP2 deficiency, ECM production and deposition by WT and TSP2 KO DFs was analyzed via polymerase chain reaction, immunofluorescence, and scanning electron microscopy and showed similar patterns. In addition, atomic force microscopy (AFM) analysis of WT and TSP2 KO ECM did not reveal differences in stiffness. In contrast, reduced VWF accumulation on TSP2 KO ECM was observed when matrices were subjected to plasma under physiological flow. AFM utilizing VWF-coated 2-üm beads confirmed the weak binding to TSP2 KO ECM, providing a mechanistic explanation for the lack of thrombus formation. Therefore, our studies show that ECM assembly is critical for interaction of collagen with VWF and subsequent thrombogenic responses. [ABSTRACT FROM AUTHOR]

The foreign body response (FBR) begins with injury acquired during implantation of a biomaterial (BM) and is detrimental due to the eventual encapsulation of the implant. Fusion of macrophages to form foreign body giant cells (FBGC), a hallmark of the FBR, is the consequence of a multistep mechanism induced by interleukin (IL)-4 that includes the acquisition of a fusion competent state and subsequent cytoskeletal rearrangements. However, the precise mechanism, regulation, and interplay among molecular mediators to generate FBGCs are insufficiently understood. Seeking novel mediators of fusion that might be regulated at the post-transcriptional level, we examined the role of microRNAs (miRs) in this process. A miR microarray was screened and identified miR-223 as a negative regulator of macrophage fusion. In addition, transfection of primary macrophages with a mir-223 mimic attenuated IL-4-induced fusion. Furthermore, miR-223 KO mice and mir-223 deficient cells displayed increased fusion in vivo and in vitro, respectively. Finally, we developed a method for in vivo delivery of miR-223 mimic utilizing PLGA nanoparticles, which inhibited FBGC formation in a biomaterial implant model. Our results identify miR-223 as a negative regulator of fusion and demonstrate miR-223 mimic-loaded nanoparticles as a therapeutic inhibitor of macrophage fusion. [ABSTRACT FROM AUTHOR]

The implantation of non-biological materials, including scaffolds for tissue engineering, ubiquitously leads to a foreign body response (FBR). We recently reported that this response negatively impacts fibroblasts encapsulated within a synthetic hydrogel and in turn leads to a more severe FBR, suggesting a cross-talk between encapsulated cells and inflammatory cells. Given the promise of mesenchymal stem cells (MSCs) in tissue engineering and recent evidence of their immunomodulatory properties, we hypothesized that MSCs encapsulated within poly(ethylene glycol) (PEG) hydrogels will attenuate the FBR. In vitro , murine MSCs encapsulated within PEG hydrogels attenuated classically activated primary murine macrophages by reducing gene expression and protein secretion of pro-inflammatory cytokines, most notably tumor necrosis factor-α. Using a COX2 inhibitor, prostaglandin E2 (PGE2) was identified as a mediator of MSC immunomodulation of macrophages. In vivo , hydrogels laden with MSCs, osteogenically differentiating MSCs, or no cells were implanted subcutaneously into C57BL/6 mice for 28 days to assess the impact of MSCs on the fibrotic response of the FBR. The presence of encapsulated MSCs reduced fibrous capsule thickness compared to acellular hydrogels, but this effect diminished with osteogenic differentiation. The use of MSCs prior to differentiation in tissue engineering may therefore serve as a dynamic approach, through continuous cross-talk between MSCs and the inflammatory cells, to modulate macrophage activation and attenuate the FBR to implanted synthetic scaffolds thus improving the long-term tissue engineering outcome. [ABSTRACT FROM AUTHOR]

Vascular remodeling is essential for tissue repair and is regulated by multiple factors, including thrombospondin-2 (TSP2) and hypoxia/VEGF-induced activation of Akt. In contrast to TSP2 knock-out (KO) mice, Akt1 KO mice have elevated TSP2 expression and delayed tissue repair. To investigate the contribution of increased TSP2 to Akt1 KO mice phenotypes, we generated Akt1/TSP2 double KO (DKO) mice. Full-thickness excisional wounds in DKO mice healed at an accelerated rate when compared with Akt1 KO mice. Isolated dermal Akt1 KO fibroblasts expressed increased TSP2 and displayed altered morphology and defects in migration and adhesion. These defects were rescued in DKO fibroblasts or after TSP2 knockdown. Conversely, the addition of exogenous TSP2 toWTcells induced cell morphology and migration rates that were similar to those of Akt1 KO cells. Akt1 KO fibroblasts displayed reduced adhesion to fibronectin with manganese stimulation when compared with WT and DKO cells, revealing an Akt1-dependent role for TSP2 in regulating integrin-mediated adhesions; however, this effect was not due to changes in β1 integrin surface expression or activation. Consistent with these results, Akt1 KO fibroblasts displayed reduced Rac1 activation that was dependent upon expression of TSP2 and could be rescued by a constitutively active Rac mutant. Our observations show that repression of TSP2 expression is a critical aspect of Akt1 function in tissue repair. [ABSTRACT FROM AUTHOR]

The PI3K/Akt pathway is necessary for several key endothelial cell (EC) functions, including cell growth, migration, survival, and vascular tone. However, existing literature supports the idea that Akt can be either pro- or antiangiogenic, possibly due to compensation by multiple isoforms in the EC when a single isoform is deleted. Thus, biochemical, genetic, and proteomic studies were conducted to examine isoform-substrate specificity for Akt1 vs. Akt2. In vitro, Akt1 preferentially phosphorylates endothelial nitric oxide synthase (eNOS) and promotes NO release, whereas non-physiological overexpression of Akt2 can bypass the loss of Akt1. Conditional deletion of Akt1 in the EC, in the absence or presence of Akt2, retards retinal angiogenesis, implying that Akt1 exerts a nonredundant function during physiological angiogenesis. Finally, proteomic analysis of Akt substrates isolated from Akt1- or Akt2-deficient ECs documents that phosphorylation of multiple Akt substrates regulating angiogenic signaling is reduced in Akfl-deficient, but not Akt2-deficient, ECs, including eNOS and Fork-head box proteins. Therefore, Akt1 promotes angiogenesis largely due to phosphorylation and regulation of important downstream effectors that promote aspects of angiogenic signaling. [ABSTRACT FROM AUTHOR]

Abstract: Intracranial implants elicit neurodegeneration via the foreign body response (FBR) that includes BBB leakage, macrophage/microglia accumulation, and reactive astrogliosis, in addition to neuronal degradation that limit their useful lifespan. Previously, monocyte chemoattractant protein 1 (MCP-1, also CCL2), which plays an important role in monocyte recruitment and propagation of inflammation, was shown to be critical for various aspects of the FBR in a tissue-specific manner. However, participation of MCP-1 in the brain FBR has not been evaluated. Here we examined the FBR to intracortical silicon implants in MCP-1 KO mice at 1, 2, and 8 weeks after implantation. MCP-1 KO mice had a diminished FBR compared to WT mice, characterized by reductions in BBB leakage, macrophage/microglia accumulation, and astrogliosis, and an increased neuronal density. Moreover, pharmacological inhibition of MCP-1 in implant-bearing WT mice maintained the increased neuronal density. To elucidate the relative contribution of microglia and macrophages, bone marrow chimeras were generated between MCP-1 KO and WT mice. Increased neuronal density was observed only in MCP-1 knockout mice transplanted with MCP-1 knockout marrow, which indicates that resident cells in the brain are major contributors. We hypothesized that these improvements are the result of a phenotypic switch of the macrophages/microglia polarization state, which we confirmed using PCR for common activation markers. Our observations suggest that MCP-1 influences neuronal loss, which is integral to the progression of neurological disorders like Alzheimer's and Parkinson disease, via BBB leakage and macrophage polarization. [Copyright &y& Elsevier]

Abstract: Management of skin wound infections presents a serious problem in the clinic, in the community, and in both civilian and military clinical treatment centers. Staphylococcus aureus is one of the most common microbial pathogens in cutaneous wounds. Peptide-morpholino oligomer (PMO) conjugates targeted to S. aureus gyrase A mRNA have shown the ability to reduce bacterial viability by direct site-specific mRNA cleavage via RNase P. As a treatment, these conjugates have the added advantages of not being susceptible to resistance due to genetic mutations and are effective against drug resistant strains. While this strategy has proven effective in liquid culture, it has yet to be evaluated in an animal model of infected surface wounds. In the present study, we combined PMO conjugates with a thermoresponsive gel delivery system to treat full-thickness mouse cutaneous wounds infected with S. aureus. Wounds treated with a single dose of PMO conjugate displayed improved healing that was associated with increased epithelialization, reduced bacterial load, and increased matrix deposition. Taken together, our findings demonstrate the efficacy and flexibility of the PMO conjugate drug delivery system and make it an attractive and novel topical antimicrobial agent. [Copyright &y& Elsevier]

Abstract: We developed a multi-functional construct capable of controlled delivery of bioactive substances that can improve wound repair by supporting the intrinsic ability of the skin to heal. We synthesized electrospun scaffolds—composed of a blend of the degradable polymers poly(l-lactide) (PLA) or polycaprolactone (PCL)—that produce highly efficient non-viral in vivo gene delivery to cells in the wound bed, provide a protective barrier during early wound healing, and support cell migration and growth. This multi-functional material was tested for its influence on wound healing: scaffolds were loaded with plasmids encoding keratinocyte growth factor (KGF) and applied to full-thickness wounds in mice. Compared to scaffolds with control plasmids, animals receiving the KGF plasmid-loaded scaffold produced significant enhancements in wound healing, which was quantified by improvements in the rate of wound re-epithelialization, keratinocyte proliferation, and granulation response. Further, we quantified the expression level of endogenous and plasmid-derived KGF in wound samples: qRT-PCR on wound sections revealed a correlation between the levels of plasmid-derived protein expression and histological analysis of wound healing, revealing an inverse relationship between the expression level of exogenous KGF and the size of the unhealed epithelial layer in wounds. Our findings suggest that engineered nanofiber PLA/PCL scaffolds are capable of highly efficient controlled DNA delivery and are promising materials for treatment of cutaneous wounds. [Copyright &y& Elsevier]

Abstract: Poly(ethylene glycol) (PEG)-based hydrogels are promising in situ cell carriers for tissue engineering. However, their success in vivo will in part depend upon the foreign body reaction (FBR). This study tests the hypothesis that the FBR affects cells encapsulated within PEG hydrogels, and in turn influences the severity of the FBR. Fibroblasts were encapsulated within PEG hydrogels containing RGD to support cell attachment. Macrophages were seeded on top of cell-laden hydrogels to mimic in vivo macrophage interrogation and treated with lipopolysaccharide to induce an inflammatory phenotype. The presence of activated macrophages reduced fibroblast gene expression for extracellular matrix molecules and remodeling, but stimulated VEGF and IL-1β gene expression. Fibroblasts impacted macrophage phenotype leading to increased iNOS, IL-1β and TNF-α expressions. Syngeneic cell-laden and acellular hydrogels were also implanted subcutaneously into C57bl/6 mice for 2, 7 and 28 days. Encapsulated fibroblasts secreted collagen type I during the first week, but tissue deposition and cellularity decreased by 28 days. The presence of encapsulated fibroblasts led to greater acute inflammation, but did not influence the fibrotic response. In summary, this work emphasizes the importance of the host response in tissue engineering, and the potentially deleterious impact it may have on cell-laden synthetic scaffolds. [Copyright &y& Elsevier]

Implantation of biomaterials and devices into soft tissues leads to the development of the foreign body response (FBR), which can interfere with implant function and eventually lead to failure. The FBR consists of overlapping acute and persistent inflammatory phases coupled with collagenous encapsulation and currently there are no therapeutic options. Initiation of the FBR involves macrophage activation, proceeding to giant cell formation, fibroblast activation, and collagen matrix deposition. Despite the recognition of this sequence of events, the molecular pathways required for the FBR have not been elucidated. We have identified that the acute inflammatory response to biomaterials requires nucleotide-binding domain and leucine-rich repeat-containing 3 (Nlrp3), apoptosis-associated speck-like protein containing CARD (Asc), and caspase-1, as well as plasma membrane cholesterol, and Syk signaling. Full development of the FBR is dependent on Asc and caspase-1, but not Nlrp3. The common antiinflammatory drug aspirin can reduce inflammasome activation and significantly reduce the FBR. Taken together, these findings expand the role of the inflammasome from one of sensing damage associated molecular patterns (DAMPs) to sensing all particulate matter irrespective of size. In addition, implication of the inflammasome in biomaterial recognition identifies key pathways, which can be targeted to limit the FBR. [ABSTRACT FROM AUTHOR]

Abstract: Poly(ω-pentadecalactone-co-p-dioxanone) [poly(PDL-co-DO)] copolyesters are copolymers of an isodimorphic system, which remain semicrystalline over the whole range of compositions. Here, we evaluated enzymatically synthesized poly(PDL-co-DO) copolymers as new materials for biomedical applications. In vivo experiments using mice, showed that the copolyesters are well tolerated, with tissue responses that are comparable to poly(p-dioxanone). In addition, the copolymers were found to degrade hydrolytically at controlled rates over a period of several months under physiological conditions. The poly(PDL-co-DO) copolymers with up to 69 mol% DO units were successfully transformed to free-standing nanoparticles that are capable of encapsulating an anticancer drug, doxorubicin, or a polynucleotide, siRNA. Drug- or siRNA-loaded nanoparticles exhibited controlled and continuous release of agent over many weeks. In addition, siLUC-encapsulated poly(PDL-co-DO) nanoparticles were active in inhibiting luciferase gene expression in LUC-RKO cells. Because of substantial differences in structure and hydrophobicity between PDL and DO units, poly(PDL-co-DO) biodegradation rate and physical properties can be tuned over a wide range depending on the copolymer composition. Our results demonstrate that the semicrystalline and biodegradable poly(PDL-co-DO) copolyesters are promising biomaterials to serve as drug carriers, as well as potential raw materials for constructing bioabsorbable sutures and other medical devices. [Copyright &y& Elsevier]

Abstract: Transplantation of endothelial cells (EC) for therapeutic vascularization is a promising approach in tissue engineering but has yet to be proven effective in clinical trials. This cell-based therapy is hindered by significant apoptosis of EC upon transplantation as well as poor recruitment of host mural cells to stabilize nascent vessels. Here, we address these deficiencies by augmenting endothelial cell transplantation with dual delivery of vascular endothelial growth factor (VEGF) – to improve survival of transplanted EC – and monocyte chemotactic protein-1 (MCP-1) – to induce mural cell recruitment. We produced alginate microparticles that deliver VEGF and MCP-1 with distinct release kinetics and that can be integrated into a collagen/fibronectin (protein) gel construct for delivery of EC. Combined delivery of VEGF and MCP-1 increased functional vessel formation from transplanted EC and also led to a higher number of smooth muscle cell-invested vessels than did EC therapy alone. Despite the well-known role of MCP-1 in inflammation, these beneficial effects were accomplished without a long-term increase in monocyte/macrophage recruitment or a shift to a pro-inflammatory (M1) macrophage phenotype. Overall, these data suggest a potential benefit of combined delivery of MCP-1 and VEGF from EC-containing hydrogels as a strategy for therapeutic vascularization. [Copyright &y& Elsevier]

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are the earliest tissue-engineered vascular grafts (TEVGs) to be used clinically. These TEVGs transform into living blood vessels in vivo, with an endothelial cell (EC) lining invested by smooth muscle cells (SMCs); however, the process by which this occurs is unclear. To test if the seeded BMCs differentiate into the mature vascular cells of the neovessel, we implanted an immuno- deficient mouse recipient with human BMC (hBMC)-seeded scaffolds. As in humans. TEVGs implanted in a mouse host as venous interposition grafts gradually transformed into living blood vessels over a 6-month time course. Seeded hBMCs, however, were no longer detectable within a few days of implantation. Instead, scaffolds were initially repopulated by mouse monocytes and subsequently repopulated by mouse SMCs and ECs. Seeded BMCs secreted significant amounts of monocyte chemoattractant protein-1 and increased early monocyte recruitment. These findings suggest TEVGs transform into functional neovessels via an inflammatory process of vascular remodeling. [ABSTRACT FROM AUTHOR]

Blood vessel formation during ischemia and wound healing requires coordination of the inflammatory response with genes that regulate blood vessel assembly. Here we show that the reticulon family member 4B, aka Nogo-B. is upregulated in response to ischemia and is necessary for blood flow recovery secondary to ischemia and wound healing. Mice lacking Nogo-B exhibit reduced arteriogenesis and angiogenesis that are linked to a decrease in macrophage infiltration and inflammatory gene expression in vivo. Bone marrow-derived macrophages isolated from Nogo knock-out mice have reduced spreading and chemotaxis due to impaired Rac activation. Bone marrow reconstitution experiments show that Nogo in myeloid cells is necessary to promote macrophage homing and functional recovery after limb ischemia. Thus. endogenous Nogo coordinates macrophage-mediated inflammation with arteriogenesis, wound healing, and blood flow control. [ABSTRACT FROM AUTHOR]

Scleroderma is a chronic disease characterized by excessive tissue fibrosis. Recent studies indicate that cultured dermal fibroblasts isolated from patients produce excessive amounts of collagen and other extracellular matrix components. In this study, we investigated the mechanism(s) of abnormal extracellular matrix accumulation in the scleroderma biopsies and the healing wounds of Tsk1/+ mice. Full-thickness excisional wounds were made in Tsk1/+ and wild-type mice and were subsequently harvested at days 7, 10, and 14 postinjury. The levels of pro-fibrotic cytokine, transforming growth factor were elevated in the wounds of Tsk1/+ mice. Interestingly, the levels of matrix metalloproteinase were significantly reduced in the granulation tissue of Tsk1/+ mice in comparison with wild-type. Furthermore, immunohistochemical analysis of the wounds indicated that the levels of γ-glutamyl-ℇ-lysine cross-links were elevated in the granulation tissue of Tsk1/+ mice as well as the fibrotic lesions of scleroderma specimens. Collectively, these findings indicate that elevated collagen synthesis and decreased matrix metalloproteinase levels, in combination with increased isopeptide bond cross-links, contribute to abnormal collagen synthesis and assembly in granulation tissue of Tsk1/+ mice and the fibrotic lesions of scleroderma patients. [ABSTRACT FROM AUTHOR]

Abstract: The development of neotissue in tissue engineered vascular grafts remains poorly understood. Advances in mouse genetic models have been highly informative in the study of vascular biology, but have been inaccessible to vascular tissue engineers due to technical limitations on the use of mouse recipients. To this end, we have developed a method for constructing sub-1mm internal diameter (ID) biodegradable scaffolds utilizing a dual cylinder chamber molding system and a hybrid polyester sealant scaled for use in a mouse model. Scaffolds constructed from either polyglycolic acid or poly-l-lactic acid nonwoven felts demonstrated sufficient porosity, biomechanical profile, and biocompatibility to function as vascular grafts. The scaffolds implanted as either inferior vena cava or aortic interposition grafts in SCID/bg mice demonstrated excellent patency without evidence of thromboembolic complications or aneurysm formation. A foreign body immune response was observed with marked macrophage infiltration and giant cell formation by post-operative week 3. Organized vascular neotissue, consisting of endothelialization, medial generation, and collagen deposition, was evident within the internal lumen of the scaffolds by post-operative week 6. These results present the ability to create sub-1mm ID biodegradable tubular scaffolds that are functional as vascular grafts, and provide an experimental approach for the study of vascular tissue engineering using mouse models. [Copyright &y& Elsevier]

Abstract: The ability of poly(anhydride-esters) composed of non-steroidal anti-inflammatory drugs that biodegrade to salicylic acid (SA) and adipic acid to prevent colonization by Pseudomonas aeruginosa and their effects on the foreign-body response were studied in vitro and in vivo, respectively. Soluble SA in bacterial medium at concentrations up to 300mg/L did not affect the growth rate or viability of P. aeruginosa, indicating that SA does not exhibit a direct toxicity effect on the bacterium. Batch degradation rates of the salicylate-based polymer in the presence of an actively growing bacterial culture only marginally (14%) increased relative to polymer degradation rates in sterile medium. Short-term (3h) bacterial adhesion studies in agitated batch systems indicated a 47% reduction in the rate of P. aeruginosa adhesion relative to a control polymer that does not release SA upon biodegradation. Long-term (3-day) biofilm accumulation studies indicated a dramatic reduction in biofilm formation on salicylate-based polymer versus controls. A recombinant P. aeruginosa pMHLAS, containing a fluorescent reporter gene prior to the las regulon, was employed to determine whether salicylate-based polymer prevents biofilm formation by the released SA inhibiting quorum sensing pathways. Long-term biofilm accumulation studies with P. aeruginosa pMHLAS insinuate that salicylate-based polymer prevents biofilm accumulation by inhibiting the las quorum sensing system. Furthermore, unlike control polymer, salicylate-based polymer implanted subcutaneously for a period of 4 weeks-resisted cell-mediated degradation and remained intact. Histological and immunohistochemical analysis indicated a reduction in overall encapsulation and paucity of macrophages in the area of the salicylate-based polymer implant. [Copyright &y& Elsevier]

The angiogenic switch during tumorigenesis is thought to be induced by a change in the balance of proangiogenic and anti-angiogenic factors. To elucidate the biological role of the endogenous angiogenesis inhibitor thrombospondin-2 (TSP-2) during multistep carcinogenesis, we subjected TSP-2-deficient and wildtype mice to a chemical skin carcinogenesis regimen. Surprisingly, TSP-2 expression was strongly upregulated in the mesenchymal stroma of wild-type mice throughout the consecutive stages of tumorigenesis whereas the angiogenesis factor, vascular endothelial growth factor, was induced predominantly in tumor cells. TSP-2 deficiency dramatically enhanced susceptibility to skin carcinogenesis and resulted in accelerated and increased tumor formation. The angiogenic switch occurred in early stages of pre-malignant tumor formation, and tumor angiogenesis was significantly enhanced in TSP-2-deficient mice. While TSP-2 deficiency did not affect tumor differentiation or proliferation, tumor cell apoptosis was significantly reduced. These results reveal upregulation of an endogenous angiogenesis inhibitor during multistep tumorigenesis and identify enhanced stromal TSP-2 expression as a novel host anti-tumor defense mechanism. [ABSTRACT FROM AUTHOR]

Extracellular matrix (ECM) derived components are emerging sources for the engineering of biomaterials that are capable of inducing desirable cell-specific responses. This review explores the use of biomaterials derived from naturally occurring ECM proteins and their derivatives in approaches that aim to regulate cell function. Biomaterials addressed are grouped into six categories: purified single ECM proteins, combinations of purified ECM proteins, cell-derived ECM, tissue-derived ECM, diseased and modified ECM, and ECM-polymer coupled biomaterials. Purified ECM proteins serve as a material coating for enhanced cell adhesion and biocompatibility. Cell-derived and tissue-derived ECM, generated by cell isolation and decellularization technologies, can capture the native state of the ECM environment and guide cell migration and alignment patterns as well as stem cell differentiation. We focus primarily on recent advances in the fields of soft tissue, cardiac, and dermal repair, and explore the utilization of ECM proteins as biomaterials to engineer cell responses. [ABSTRACT FROM AUTHOR]

The article presents a study which describes how the endothelial nitric oxide synthase regulates the expression of the angiogenesis inhibitor thrombospondin 2. The researchers have demonstrated the importance of nitric oxide in cardiovascular function in a mice model with multiple vascular defects. It also reveals that nitric oxide is critical in the recovery from hind limb ischemia and dermal would healing processes.