American Society for Peripheral Nerve

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Restoration of Long Nerve Defects using Laminin Rich Epineural Sheath Conduit in a Sheep Model
Maria Siemionow, MD PhD DSc1,2; Joanna Cwykiel, MSc1,2; Halil Safak Uygur, MD2; Adam Bobkiewicz, MD2; Maria Madajka, PhD1; Grzegorz Kwiecien, MD1; Can Ozturk, MD1; Miroslaw Lukaszuk, MD1; Jacek Szopinski, MD, PhD2
1University of Illinois at Chicago, Chicago, IL, 2Cleveland Clinic, Cleveland, OH

Background: Repair of long nerve defects (>3cm) in patients suffering from multiple-site traumas is challenging due to the limited availability of autologous tissue. Moreover, autologous nerve grafting causes pain, neuroma formation, and infections at the harvest site. There has been a focus on development of nerve conduits as "off-the-shelf" products. Currently available conduits for restoration of long nerve defects require immunosuppression and show poor functional outcomes. The study’s aim was to test the feasibility of Epineural Sheath Conduit (ESC) on restoration of 6-cm long nerve defect in a sheep model.
Methods: Eight outbred ewes were divided into three groups: Group 1 – 6-cm long median nerve defect was created and left without repair(n=4 limbs/group), Group 2 – 6-cm median nerve autograft repair controls (n=6 limbs/group), and Group 3 – 6 cm autologous ESC filled with saline (n=6 limbs/group). To spare animals, both forelimbs of each sheep were utilized. ESC was created under operative microscope by fascicles removal from the dissected 6-cm long sheep median nerve. Prior to median nerve repair, ESC was tested for the presence of GFAP, NGF, S-100, HLA I, CD31, collagen I, vimentin and laminin B2 using immunofluorescent staining. At 6 months after nerve repair, neurosensory recovery was assessed by nerve conduction velocity (NCV) and somatosensory evoked potential (SSEP) measurements. Histomorphometry (Toluidine blue) and immunostaining were performed to confirm nerve regeneration and axonal growth.
Results: The anatomical course of sheep median nerve was examined. ESC showed high expression of collagen I and laminin B responsible for guidance of growing axons. At 6 months after repair, the shape and integrity of the ESC was preserved. ESC was well vascularized and the tissue adhesion was comparable to the autograft controls. The NCV and SSEP assessments confirmed the presence of neurosensory responses in saline filled ESC and smaller diameter fascicles were observed in comparison to autograft controls. Immunofluorescent staining at 6 months showed presence of fascicle-like structure in the middle, and distal parts in saline filled ESC conduit. Toluidine blue staining revealed the presence of myelinated axons.
Conclusion: The feasibility of ESC to restore 6-cm long nerve defects and support axonal regeneration in a sheep model was confirmed by immunohistochemical assays and neurosensory assessments. ESC is a novel bioconstruct of naturally occurring epineural sheath, having a potential for successful regeneration of long nerve defects. In the future ESC can be included into the armamentarium of reconstructive and regenerative medicine.


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