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Comparison of Amniotic Membrane and Collagen Nerve Wraps Around Sciatic Nerve Reverse Autografts in a Rat Model
Erin M. Wolfe, BS1, Sydney A. Mathis, BS1, Natalia de la Oliva Muñoz, PhD2, Daisy Gonzalez, BS1, Steven Ovadia, MD1, Prakash J. Mathew, MD1, Damien D. Pearse, PhD2, Martin Oudega, PhD1 and Zubin J. Panthaki, MD1, (1)University of Miami Miller School of Medicine, Miami, FL, (2)University of Miami Miller School of Medicine, Miami Project to Cure Paralysis, Miami, FL

Introduction: Clinically, repair of peripheral nerve injuries is problematic due to the slow rate of axon regeneration, irreversible muscle fibrosis, and axonal misrouting. Nerve wraps provide a protective encasement around peripheral nerves following neurorrhaphy, which mitigates epineual scarring and adhesions, facilitates axonal regeneration, and improves functional recovery. Various types of nerve wraps are available for use in clinical practice. Human amniotic membrane (hAM) and collagen matrix are easily obtainable FDA approved biomaterials with no donor site morbidity and minimal inflammatory response. However, their efficacy has not been compared. Collagen nerve wraps are semi-permeable and allow for diffusion of neurotrophic factors. hAM nerve wraps provide a neurotrophic effect, containing mesenchymal stem cells (MSCs) which can secrete neurotrophic factors, differentiate into neural phenotypes and enhance Schwann cell proliferation. Here we compared the efficacy of collagen and hAM nerve wraps in a rodent sciatic nerve reverse autograft model, with the hypothesis that the use of hAM nerve wraps would result in improved nerve regeneration and functional recovery compared to collagen or control groups.

Materials & Methods: Lewis rats (n = 29) underwent sciatic nerve injury and repair in which a 10-mm gap was bridged with reverse autograft combined with either no nerve wrap (control), collagen nerve wrap or hAM nerve wrap. Behavioral analyses were performed at baseline, 4, 8 and 12 weeks. Electrophysiological studies were conducted at 8, 10 and 12 weeks. Gastrocnemius muscle weights were evaluated at 12 weeks, and fibrosis, inflammation and axonal regeneration were investigated via histological and immunohistochemical analyses.

Results: Application of hAM nerve wraps in a rodent sciatic nerve reverse autograft model results in improved functional and histological outcomes compared to control and collagen groups at 12 weeks. We identified significantly greater numbers of axons and reduced adhesions in hAM-treated rats compared to collagen-treated rats and controls at 12 weeks (p< 0.05). This correlated with significantly improved functional outcomes and ratios of experimental to control gastrocnemius muscle weights in the hAM group compared to the collagen and control groups (p< 0.05).

Conclusions: Comparative analysis of controls and collagen and hAM-treated groups suggests that the use of hAM nerve wraps results in improved nerve regeneration and functional recovery following peripheral nerve injury and repair. The superior outcomes of hAM-treated groups indicate that hAM mitigates fibrosis and may enhance nerve regeneration due to its anti-inflammatory and pro-regenerative effects, making it a promising biomaterial for clinical applications in peripheral nerve repair.

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