"Off-the-Shelf" Nerve Matrix Preservation

Decellularized human nerves overcome the limitations of the current treatments for large peripheral nerve injuries. However, the use of decellularized nerves requires an "off-the-shelf" availability for useful and actual clinical application. In this study, we addressed the preservation of the native and decellularized human nerve matrix in an integrative approach for tissue scaffold production. For native nerve matrix preservation analysis, we used histological examination and immunofluorescence to examine the structure, biomechanical assays to evaluate the tensile strength and Young's modulus, and analyzed the extracellular matrix (ECM) composition using enzyme-linked immunosorbent assay (ELISA) and biochemical assays for laminin, collagen and sulfated glycosaminoglycans (sGAG). After decellularization, nuclear remnants and DNA content were evaluated using 4',6-diamidino-2-phenylindole (DAPI) staining and the picogreen quantification assay, as well as immunofluorescence or ELISA for cell rests (S100 protein and myelin staining) evaluation. Decellularized cryopreserved scaffolds were assayed for biomechanics, ECM composition, and structural maintenance. Cytotoxicity assays were performed to evaluate the biocompatibility of the nerve matrix extracts after cryopreservation. We compared different strategies for native nerve storage and found that preservation up to 7 days at 4°C in Roswell Park Memorial Institute medium maintained biomechanical properties, such as Young's modulus and tensile strength, along with the structure and ECM composition, regarding laminin, collagen, and sGAG. After a successful decellularization process, that eliminated cell remnants, nerve scaffolds were frozen in an "in house" formulated cryoprotectant, using an automatic controlled rate freezer. Nerve structure, ECM composition, and biomechanical properties were maintained before and after the freezing process in comparison with native nerves. The extracts of the nerve scaffolds after thawing were not cytotoxic and the freezing process sustained good viability in 3T3 cells (graphical abstract). Since our approach facilitates transport, storage, and provide a ready-to-use alternative, it could be used in a clinical application for the treatment of long-gap peripheral nerve injuries in regenerative medicine.