Treatment of volumetric muscle loss in mice using nanofibrillar scaffolds enhances vascular organization and integration

Karina H Nakayama,Ngan F Huang,Victor Garcia,Ioannis Karakikes,Oscar J Abilez,Nicholas S Calvo,Chelsey S Simmons,Cynthia Alcazar,Patrick Paine,Thomas A Rando,Marco Quarta

doi:10.1038/s42003-019-0416-4

Abstract

Traumatic skeletal muscle injuries cause irreversible tissue damage and impaired revascularization. Engineered muscle is promising for enhancing tissue revascularization and regeneration in injured muscle. Here we fabricated engineered skeletal muscle composed of myotubes interspersed with vascular endothelial cells using spatially patterned scaffolds that induce aligned cellular organization, and then assessed their therapeutic benefit for treatment of murine volumetric muscle loss. Murine skeletal myoblasts co-cultured with endothelial cells in aligned nanofibrillar scaffolds form endothelialized and aligned muscle with longer myotubes, more synchronized contractility, and more abundant secretion of angiogenic cytokines, compared to endothelialized engineered muscle formed from randomly-oriented scaffolds. Treatment of traumatically injured muscle with endothelialized and aligned skeletal muscle promotes the formation of highly organized myofibers and microvasculature, along with greater vascular perfusion, compared to treatment of muscle derived from randomly-oriented scaffolds. This work demonstrates the potential of endothelialized and aligned engineered skeletal muscle to promote vascular regeneration following transplantation.

Highlights

Traumatic skeletal muscle injuries cause irreversible tissue damage and impaired revascularization
Based on immunofluorescence staining of myosin heavy chain (MHC), the myotubes in engineered skeletal muscle formed from aligned scaffolds were highly organized along the direction of the nanofibrils (Fig. 1e, f)
The degree of alignment was quantified in which an orientation perfectly parallel to the nanofibers corresponded to an angle of 0°, whereas myotubes organized perpendicular to the axis of the nanofibrils would have an angle of 90°

Summary

Introduction

Traumatic skeletal muscle injuries cause irreversible tissue damage and impaired revascularization. Experimental approaches to induce muscle and vascular regeneration by the delivery of myogenic or angiogenic growth factors[7,8,9,10,11] or other biomolecules[12,13] have shown therapeutic potential in preclinical models of muscle injury[7,12] Other experimental approaches such as the transplantation of therapeutic cells or minced tissues[14,15,16,17,18,19] are limited by the ability to control the structural organization of newly formed muscle and associated vasculature. We have previously shown that cells seeded on aligned nanofibrillar scaffolds promote cytoskeletal organization along the direction of nanofibrillar alignment[27,28,29] These studies highlight the utility of spatial patterning in generating highly ordered tissues such as skeletal muscle and vessels. In the absence of instructive cues from the extracellular matrix (ECM), the newly formed myofibers and vasculature may not assemble into the organized structure of native muscle and microvasculature

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Conclusion