Dynamic Seeding versus Microinjection of Adipose-Derived Mesenchymal Stem Cells to Acellular Nerve Allograft Reconstructions

Abstract

Background: Functional recovery following acellular nerve allograft (ANA) reconstructions remains inferior to autologous nerve grafting, but have demonstrated improved outcomes with the addition of adipose-derived mesenchymal stem cells (MSC). Controversy exists regarding the optimal cell delivery method to enhance ANA reconstructions. We investigated the functional recovery of ANAs after dynamic seeding versus microinjection of MSCs. Methods: Forty Lewis rats underwent reconstruction of a 10-mm sciatic nerve defect. Animals were divided into four groups: reversed autograft, ANA alone, ANA dynamically seeded, or ANA injected with MSCs. During the survival period, ultrasound measurements of the tibialis anterior (TA) muscle cross-sectional area were performed. At 12 weeks, functional recovery was evaluated using measurements of ankle contracture, compound muscle action potential (CMAP), maximum isometric tetanic force (ITF), muscle mass, histomorphometry, and immunofluorescence. Results: The dynamic seeding and microinjection groups demonstrated higher cross-sectional TA muscle area recovery than autografts and ANAs alone at week 8 and week 4 and 8, respectively. The ankle contracture and CMAP amplitude recovery were superior in autografts and both seeding methods compared to ANAs alone. The microinjection group demonstrated significantly higher ITF, muscle mass, and number of axons compared to ANAs alone. Both seeding methods showed higher CD34 densities compared to ANAs alone. No significant differences between dynamic seeding and microinjection were observed for both functional and histological outcomes. Conclusions: The addition of MSCs to ANAs demonstrated earlier motor regeneration compared to autografts and ANAs alone. Both seeding methods improved functional outcomes in the rat sciatic nerve defect model. Clinical Relevance Statement: Future clinical applications of stem cell-based nerve reconstructions are dependent on determining optimum delivery methods, which are technically feasible, reproducible, cost-efficient, and timely.