Anisa Yalom

A subcranial Le Fort III advancement with distraction osteogenesis as a clinical strategy to approach pycnodysostosis with midface retrusion and exorbitism.

Pycnodysostosis is a rare autosomal recessive skeletal disorder involving a constellation of craniofacial manifestations including midface retrusion. We report the case of a 13-year-old girl with pycnodysostosis who presented with exorbitism, midface retrusion, malocclusion, and obstructive sleep apnea. Here, we describe the successful use of subcranial Le Fort III advancement using distraction osteogenesis with internal Kawamoto distracters. After a latency of 5 days, distraction for 10 days, and consolidation for 12 weeks, her midface was advanced by 10 mm with slight overcorrection at the occlusion level. At 2 years postoperatively, the patient had complete remission of her sleep apnea, resolution of her exorbitism, and amelioration of her class III malocclusion to class I. To the best of our knowledge, this is the first report of a successful subcranial Le Fort III midface advancement with distraction osteogenesis for craniofacial reconstruction of a pycnodysostosis. Our report highlights the surgical options that have been described for this craniofacial deformity and presents a novel and expedient approach for patients with pycnodysostosis presenting with exorbitism, midface retrusion, and/or sleep apnea.

A novel oxysterol promotes bone regeneration in rabbit cranial bone defects

Bone morphogenetic proteins (BMPs) have played a central role in the development of regenerative therapies for bone reconstruction. However, the high cost and side‐effect profile of BMPs limits their broad application. Oxysterols, naturally occurring products of cholesterol oxidation, are promising osteogenic agents alternative to BMPs. The osteogenic capacity of these non‐toxic and relatively inexpensive molecules has been documented in rodent models. We studied the impact of Oxy49, a novel oxysterol analogue, on the osteogenic differentiation of rabbit bone marrow stromal cells (BMSCs). Moreover, we evaluated the capacity for in vivo bone regeneration with Oxy49 in rabbit cranial bone defects. We found that rabbit BMSCs treated with Oxy49 demonstrated differentiation along osteogenic pathways, and that complete bone regeneration occurred when cranial defects were treated with Oxy49. Collectively, these results demonstrate that Oxy49 has the ability to induce osteogenic differentiation in rabbit BMSCs with an efficacy comparable to that of BMP‐2 and to promote significant bone regeneration in cranial defects. Oxysterols may be a viable novel agent in bone tissue engineering. Copyright

In vitro study of a novel oxysterol for osteogenic differentiation on rabbit bone marrow stromal cells.

Background: Bone morphogenetic proteins (BMPs) are powerful osteoinductive growth factors but are associated with exorbitant costs and undesirable side effects. Oxysterols are biocompatible cholesterol oxidation products with osteoinductive properties that may represent an alternative to BMP. In this study, the authors examine the osteogenic potential and mechanisms of actions of oxysterol 49, a novel oxysterol analogue, in primary rabbit bone marrow stromal cells. Methods: Bone marrow stromal cells were isolated from the iliac crests of New Zealand White rabbits and then treated with various concentrations of oxysterol 49 or BMP-2, either alone or in combination. Alkaline phosphatase activity and expression of osteocalcin and osteopontin were evaluated. The effect of treatment of cells with cyclopamine, a known hedgehog signaling pathway inhibitor, was also assessed. Results: Alkaline phosphatase activity was increased in cells treated with 1 µM oxysterol 49 relative to cells treated with BMP-2. Expression of osteocalcin and osteopontin in cells treated with oxysterol 49 and BMP-2 was equivalent. Alkaline phosphatase activity was decreased with the addition of cyclopamine. Combined treatment with oxysterol 49 and BMP-2 resulted in additive increases in alkaline phosphatase activity and osteocalcin and osteopontin expression. Conclusions: Oxysterol 49 has osteoinductive properties that are similar to those of BMP-2 in rabbit bone marrow stromal cells. The mechanism of this activity is at least in part related to the hedgehog signaling pathway. The two growth factors demonstrate additive effects when used in combination. Further study is required to examine the potential role of oxysterol 49 as a complement or alternative to BMP-2 in bone tissue engineering.

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

Development of chemotactic smart scaffold for use in tissue regeneration.

Background: Regenerative medicine aims to obviate the need for autologous grafting through the use of bioengineered constructs that combine stem cells, growth factors, and biocompatible vehicles. Human mesenchymal stem cells and vascular endothelial growth factor (VEGF) have both shown promise for use in this context, the former because of their pluripotent capacity and the latter because of its chemotactic activity. The authors harnessed the regenerative potential of human mesenchymal stem cells and VEGF to develop a chemotactic scaffold for use in tissue engineering. Methods: Human mesenchymal stem cells were transduced with human VEGF via lentivirus particles to secrete VEGF. The chemotactic activity of the VEGF-transduced stem cells was evaluated via a trans-well assay. Migration through semipermeable membranes was significantly greater in chambers filled with medium conditioned by VEGF-transduced cells. VEGF-transduced cells were then seeded on apatite-coated poly(lactic-co-glycolic acid) scaffolds, thereby creating the Smart Scaffold. To determine in vivo angiogenesis, the Smart Scaffolds were implanted into subcutaneous pockets in the backs of nude mice. Results: Significantly larger numbers of capillaries were observed in the Smart Scaffold compared with control implants on immunohistologic studies. For the chemotactic in vivo study, human mesenchymal stem cells tagged with a fluorescent dye (1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide) were injected intravenously via tail vein after the subcutaneous implantation of the Smart Scaffolds. In vivo fluorescent imaging revealed that fluorescent dye–tagged human mesenchymal stem cells successfully accumulated within the Smart Scaffolds. Conclusion: These observations suggest that VEGF may play a vital role in the design of clinically relevant tissue regeneration graft substitutes through its angiogenic effects and ability to chemoattract mesenchymal stem cells.

Abstract P19: Peripheral Nerve Repair Using a Novel Peptide Amphiphile Nanofibers

PurPose: Traumatic peripheral nerve injuries can result in lifelong disability. Primary nerve repair is used for short nerve defects. Autologous nerve can be used in longer defects but creates donor site morbidity. Nerve conduits lack an aligned internal scaffold to support and guide axonal regeneration. Peptide amphiphiles (PA) can self-assemble into aligned nanofibers and promote peripheral nerve regeneration in vivo. There are no studies to date that examine the ability of PA nanofibers to support the regeneration of injured nerves that supply the musculoskeletal system. In this preliminary study, we investigate the viability of rat Schwann cells after incorporation into PA gels.

A Novel Scaffold for the Repair of Peripheral Nerve Injury

INTRODUCTION: TPeripheral nerve injuries can result in lifelong disability. Primary nerve repair is used for short nerve defects. Though autologous nerve can bridge longer defects, the harvesting procedure creates donor site morbidity. Nerve conduits lack an aligned internal scaffold to support and guide axonal regeneration. E2 peptide amphiphiles (PA) can selfassemble into aligned nanofi bers, and can potentially mimic the native internal architecture of peripheral nerve. Bioactive epitopes IKVAV (Ile-Lys-Val-Ala-Val) and RGDS (Arg-GlyAsp-Ser) can be incorporated into E2PA nanofi bers and have been shown to promote neuronal cell adhesion, growth, and migration. There are no studies to date that examine the ability of E2PA nanofi bers to support the proliferation of Schwann cells, key components in peripheral nerve healing. In this preliminary study, we investigate the proliferation of rat Schwann cells after incorporation into aligned E2PA gels combined with bioactive epitopes.

Abstract 178: HUMAN MESENCHYMAL STEM CELLS REGENERATE MATURE BONE AND MITIGATE INFLAMMATION IN A XENOTRANSPLANTATION MODEL

Background: Tissue engineering relies on the ability to isolate, expand, and deliver populations of pluripotent cells that have regenerative capacity. Complex defects and recalcitrant wounds are characterized by presence of in ammatory tissue, which can hinder the regenerative potential of stem cells. The intricate relationship between in ammation and regenerative repair is poorly understood, but its understanding is crucial to the development of clinically relevant solutions in regenerative transplant medicine. The purpose of this study is to elucidate some of the characteristics of that relationship.