ABSTRACT
INTRODUCTION: A detailed three-dimensional (3D) evaluation of microvasculature is evolving to be a powerful tool, providing mechanistic understanding of angiomodulating strategies. The aim of this study was to evaluate the microvascular architecture of nerve allografts after combined stem cell delivery and surgical angiogenesis in a rat sciatic nerve defect model. MATERIALS AND METHODS: In 25 Lewis rats, sciatic nerve gaps were repaired with (i) autografts, (ii) allografts, (iii) allografts wrapped in a pedicled superficial inferior epigastric artery fascia (SIEF) flap to provide surgical angiogenesis, combined with (iv) undifferentiated mesenchymal stem cells (MSC) and (v) MSCs differentiated into Schwann cell-like cells. At two weeks, vascular volume was measured using microcomputed tomography, and percentage and volume of vessels at different diameters were evaluated and compared with controls. RESULTS: The vascular volume was significantly greatest in allografts treated with undifferentiated MSCs and surgical angiogenesis combined as compared to all experimental groups (P<0.01 as compared to autografts, P<0.0001 to allografts, and P<0.05 to SIEF and SIEF combined with differentiated MSCs, respectively). Volume and diameters of vessel segments in nerve allografts were enhanced by surgical angiogenesis. These distributions were further improved when surgical angiogenesis was combined with stem cells, with greatest increase found when combined with undifferentiated MSCs. CONCLUSIONS: The interaction between vascularity and stem cells remains complex, however, this study provides some insight into its synergistic mechanisms. The combination of surgical angiogenesis with undifferentiated MSCs specifically, results in the greatest increase in revascularization, size of vessels, and stimulation of vessels to reach the middle longitudinal third of the nerve allograft.
Subject(s)
Neovascularization, Physiologic , Sciatic Nerve/surgery , Stem Cell Transplantation , Allografts , Animals , Autografts , Cell Differentiation , Male , Microcirculation , Models, Animal , Nerve Regeneration , Nerve Transfer , Rats , Rats, Inbred Lew , Surgical Flaps/blood supply , X-Ray MicrotomographyABSTRACT
Introduction: The clinical use of tacrolimus is characterized by many side effects which include neurotoxicity. In contrast, tacrolimus has also shown to have neuroregenerative properties. On a molecular level, the mechanisms of action could provide us more insight into understanding the neurobiological effects. The aim of this article is to review current evidence regarding the use of tacrolimus in peripheral nerve injuries.Areas covered: Available data on tacrolimus' indications were summarized and molecular mechanisms were elucidated to possibly understand the conflicting neurotoxic and neuroregenerative effects. The potential clinical applications of tacrolimus, as immunosuppressant and enhancer of nerve regeneration in peripheral nerve injuries, are discussed. Finally, concepts of delivery are explored.Expert opinion: It is unclear what the exact neurobiological effects of tacrolimus are. Besides its known calcineurin inhibiting properties, the mechanism of action of tacrolimus is mediated by its binding to FK506-binding protein-52, resulting in a bimodal dose response. Experimental models found that tacrolimus administration is preferred up to three days prior to or within 10 days post-nerve reconstruction. Moreover, the indication for the use of tacrolimus has been expanding to fields of dermatology, ophthalmology, orthopedic surgery and rheumatology to improve outcomes after various indications.
