Bioactive peptide amphiphile nanofiber gels enhance burn wound healing.

BACKGROUND: Burns are physically debilitating and potentially fatal injuries. The standard-of-care for burn wounds is the coverage with gauze dressings designed to minimize trauma to the regenerating epidermis and dermis during dressing changes. However, deep partial- and full-thickness burns always heal slowly when standard wound care alone is performed. We have previously reported that peptide amphiphile (PA) gels, pH-induced self-assembling nanostructured fibrous scaffolds, promote cell proliferation and have great potential in regenerative medicine for rapid repair of tissues. In this study, we hypothesized that the PA gels are capable of accelerating wound healing in burn injury. METHODS: Artificially generated thermally damaged fibroblasts and human umbilical vein endothelial cells were seeded onto the various PA nanofiber gels including bioactive and nonbioactive peptide sequences. Cell proliferation was assessed at different time points, and thermally damaged fibroblasts and HUVECs manifested increased proliferation with time when cultured with various PA gels. To determine in vivo effects, burn wounds of rats were treated with the bioactive Arg-Gly-Asp-Ser (RGDS)-modified gel that showed greater cell proliferation in vitro. The wound closure was observed, and skin samples were harvested for histologic evaluation. RESULTS: Cell proliferation using the RGDS-PA gel was significantly higher than that observed in other gels. The RGDS-PA gel significantly enhanced re-epithelialization during the burn wound healing process between days 7 and 28. Application of PA gels accelerates the recovery of deep partial-thickness burn wounds by stimulation of fibroblasts and the creation of an environment conducive to epithelial cell proliferation and wound closure. CONCLUSIONS: This biomaterial represents a new therapeutic strategy to overcome current clinical challenges in the treatment of injuries resulting from burns.

Application of Hydroxycholesterols for Alveolar Cleft Osteoplasty in a Rodent Model.

BACKGROUND: Bone morphogenetic proteins (BMPs) have played a central role in the regenerative therapies for bone reconstruction, including alveolar cleft and craniofacial surgery. However, the high cost and significant adverse effect of BMPs limit their broad application. Hydroxycholesterols, naturally occurring products of cholesterol oxidation, are a promising alternative to BMPs. The authors studied the osteogenic capability of hydroxycholesterols on human mesenchymal stem cells and the impact of hydroxycholesterols on a rodent alveolar cleft model. METHODS: Human mesenchymal stem cells were treated with control medium or osteogenic medium with or without hydroxycholesterols. Evaluation of cellular osteogenic activity was performed. A critical-size alveolar cleft was created and one of the following treatment options was assigned randomly to each defect: collagen sponge incorporated with hydroxycholesterols, BMP-2, or no treatment. Bone regeneration was assessed by means of radiologic and histologic analyses and local inflammation in the cleft evaluated. Moreover, the role of the hedgehog signaling pathway in hydroxycholesterol-mediated osteogenesis was examined. RESULTS: All cellular osteogenic activities were significantly increased on human mesenchymal stem cells treated with hydroxycholesterols relative to others. The alveolar cleft treated with collagen sponge with hydroxycholesterols and BMP-2 demonstrated robust bone regeneration. The hydroxycholesterol group revealed histologically complete bridging of the alveolar defect with architecturally mature new bone. The inflammatory responses were less in the hydroxycholesterol group compared with the BMP-2 group. Induction of hydroxycholesterol-mediated in vitro osteogenesis and in vivo bone regeneration were attenuated by hedgehog signaling inhibitor, implicating involvement of the hedgehog signaling pathway. CONCLUSION: Hydroxycholesterols may represent a viable alternative to BMP-2 in bone tissue engineering for alveolar cleft.

Oxy133, a novel osteogenic agent, promotes bone regeneration in an intramembranous bone-healing model.

Current reconstructive techniques for complex craniofacial osseous defects are challenging and are associated with significant morbidity. Oxysterols are naturally occurring cholesterol oxidation products with osteogenic potential. In this study, we investigated the effects of a novel semi-synthetic oxysterol, Oxy133, on in vitro osteogenesis and an in vivo intramembranous bone-healing model. Rabbit bone marrow stromal cells (BMSCs) were treated with either Oxy133 or BMP-2. Alkaline phosphatase (ALP) activity, expression of osteogenic gene markers and in vitro mineralization were all examined. Next, collagen sponges carrying either Oxy133 or BMP-2 were used to reconstruct critical-sized cranial defects in mature rabbits and bone regeneration was assessed. To determine the mechanism of action of Oxy133 both in vitro and in vivo, rabbit BMSCs cultures and collagen sponge/Oxy133 implants were treated with the Hedgehog signalling pathway inhibitor, cyclopamine, and similar outcomes were measured. ALP activity in rabbit BMSCs treated with 1 µm Oxy133 was induced and was significantly higher than in control cells. These results were mitigated in cultures treated with cyclopamine. Expression of osteogenic gene markers and mineralization in BMSCs treated with 1 µm Oxy133 was significantly higher than in control groups. Complete bone regeneration was noted in vivo when cranial defects were treated with Oxy133; healing was incomplete, however, when cyclopamine was added. Collectively, these results demonstrate that Oxy133 has the ability to induce osteogenic differentiation in vitro in rabbit BMSCs and to promote robust bone regeneration in vivo in an animal model of intramembranous bone healing. Copyright © 2015 John Wiley & Sons, Ltd.

Natural Killer Cells Differentiate Human Adipose-Derived Stem Cells and Modulate Their Adipogenic Potential.

BACKGROUND: Natural killer cells are thought to represent more than 30 percent of all lymphocytes within the stromal vascular fraction of lipoaspirates. However, their physiologic interaction with adipocytes and their precursors has never been specifically examined. The authors hypothesized that natural killer cells, by means of cytokine secretion, are capable of promoting the differentiation of adipose-derived stem cells. METHODS: Human natural killer cells purified from healthy donors' peripheral blood mononuclear cells were activated with a combination of interleukin-2 and anti-CD16 monoclonal antibody; natural killer cell supernatant was collected. Adipose-derived stem cells isolated from raw human lipoaspirates from healthy patients were treated with growth media, growth media with natural killer cell supernatant, adipogenic media, and adipogenic media with natural killer cells supernatant. Flow cytometric analysis was performed on cells using antibodies against B7H1, CD36, CD44, CD34, CD29, and MHC-1. Adipogenic-related gene expression (PPAR-γ, LPL, GPD-1, and aP2) was assessed. Oil Red O staining was performed as a functional assay of adipocyte differentiation and adipogenesis. RESULTS: Adipose-derived stem cells maintained in growth media with natural killer cell supernatant lost markers of "stemness," including CD44, CD34, and CD29; and expressed markers of differentiation, including B7H1 and MHC-1. Adipose-derived stem cells treated with natural killer cell supernatant accumulated small amounts of lipid after 10 days of natural killer cell supernatant treatment. Adipose-derived stem cells treated with natural killer cell supernatant showed altered expression of adipogenesis-associated genes compared with cells maintained in growth media. Adipose-derived stem cells maintained in adipogenic media with natural killer cell supernatant accumulated less lipid than those cells in adipogenic media alone. CONCLUSIONS: The authors demonstrate that, through secreted factors, natural killer cells are capable of differentiating adipose-derived stem cells. In cells maintained in adipogenic media, treatment with natural killer cell supernatant modulated adipogenic potential.