A Comparison of Native Decellularized Muscle Matrix with Commercially-Available Acellular Dermal Matrices for Muscle Regeneration in a Surgical Rat Model
Hari Iyer, M.D.C.M Candidate1,2, Steven Lanier, MD1, Emily Friedrich, PhD1, Robert Galiano, MD1.
1Northwestern University, Feinberg School of Medicine, Chicago, IL, USA, 2McGill University, Montreal, QC, Canada.
PURPOSE: Service men and women commonly suffer extensive high-energy soft tissue damage to the face and limbs. Associated volumetric muscle loss can lead to devastating functional deficits. While existing therapies can help restore cosmesis, reconstructive options to restore function remain significantly limited. The use of decellularized extracellular matrix (ECM) has yielded promise in regenerative medicine, but no successful strategies yet exist that induce in situ regeneration of functional skeletal muscle. This study aimed to compare the myogenic capacity of commercially available acellular dermal matrices (ADM) to native dermal and muscular decellularized ECM.
METHODS: 41 Sprague-Dawley rats underwent surgery to create bilateral 10 mm circular latissimus dorsi defects. Defects were assigned to defect alone, or implantation of AlloDerm®, Strattice™, decellularized rat muscle (DCM) or decellularized rat dermis (DCD). 30 and 60-day timepoints were analyzed. Decellularized native matrices were prepared from fresh tissues using a novel SDS protocol optimized to reduce encapsulation. Specimens were analyzed for gross appearance and stimulated prior to animal sacrifice to assess contraction. Histologic specimens were evaluated for integration and encapsulation. Immunofluorescence analysis was used to characterize neovascularisation and myogenesis. A comparative analysis of inflammation and fibrosis was performed by qPCR.
RESULTS: DCM showed markedly better gross incorporation than all other groups at 30 and 60 days, and were the only implants to contract upon direct electrical stimulation. Histologically, the commercially available ADM’s demonstrated encapsulation at both 30 and 60 days, and Strattice™ showed peripheral hypercellularity and central acellularity, whereas native decellularized matrices showed integration. DCM CD-31 immunofluorescence revealed a developed microvascular network at 60 days, whereas AlloDerm®, DCD and defect demonstrated less neovasculature. Strattice™ showed no vascular ingrowth whatsoever. Native matrices showed evidence of MHC-positive myocytes within the peripheral regions of the implants at 30 and 60 days in a chronologically increasing fashion. Defect alone, AlloDerm® and Strattice™ demonstrated no such MHC signal at any time point. At 30 days, it was impossible to isolate enough RNA from our Strattice™ implants for qPCR analysis. Equally at 30 days, DCM showed no significant difference to control in terms of COX-2 expression, whereas AlloDerm® and DCD showed a significant increase from control (p≤0.05) and also expressed significantly more TNF-α than DCM (p≤0.01). At 60 days, DCM expression of COX-2 and TNF-α was significantly inferior to all other implants. There was significantly less collagen-1a gene expression in DCM as compared to AlloDerm® at 30 days, and at 60 days significantly less than in Strattice™ (p≤0.05) and DCD (p≤0.01). Alpha-smooth muscle actin expression was significantly elevated in AlloDerm® at 60 days compared to DCM, and connective tissue growth factor was more highly expressed in all matrices when compared to DCM. MyoD expression was significantly higher than control in DCM at both 30 and 60 days.
CONCLUSION: Our decellularised muscle matrix showed superiority in terms of integration, neovasculogenesis and myogenesis when compared to ADM’s, both xenogeneic and native, in a muscle defect model. It also showed a trend towards less inflammation and fibrosis at both 30 and 60 days.
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