Aligned nanofibers of decellularized muscle extracellular matrix for volumetric muscle loss

Abstract

Volumetric muscle loss (VML) is a traumatic loss of muscle tissue that results in chronic functional impairment. When injured, skeletal muscle is capable of small‐scale repair; however, regenerative capacities are lost with VML due to a critical loss stem cells and extracellular matrix (ECM). Consequences of VML include either long‐term disability or delayed amputations of the affected limb. While the prevalence of VML is substantial, currently a successful clinical therapy has not been identified. In a previous study, an electrospun composed of polycaprolactone (PCL) and decellularized‐ECM (D‐ECM) supported satellite cell‐mediated myogenic activity in vitro. In this study, we investigate the extent to which this electrospun scaffold can support functional muscle regeneration in a murine model of VML. Experimental groups included no treatment, pure PCL treated, and PCL:D‐ECM (50:50 blend) treated VML defects. The PCL:D‐ECM scaffold treated VML muscles supported increased activity of anti‐inflammatory M2 macrophages (arginase+) at Day 28, compared to other experimental groups. Increased myofiber (MHC+) regeneration was observed histologically at both Days 7 and 28 post‐trauma in blend scaffold treated group compared to PCL treated and untreated groups. However, improvements in muscle weights and force production were not observed. Future studies would evaluate muscle function at longer time‐points post‐VML injury to allow sufficient time for reinnervation of regenerated muscle fibers.

Advances in biomaterials for skeletal muscle engineering and obstacles still to overcome

“…Because reduced force production is a hallmark of VML, isometric torque production is often evaluated to assess muscle regeneration. This analysis often entails securing the animal's foot to a force plate and inserting sterile electrodes to stimulate the peroneal nerve [ 61 , 63 , 65 , 85 , 91 , 98 ]. By comparing isometric torque before injury and at set time points, often 4- and 8-weeks after treatment, information can be gathered on the extent of muscle repair and regeneration of NMJs.…”

“…From there, histology and IF staining can be performed. Hematoxylin and eosin (H&E) paired with Masson's trichrome histological stain can be used to identify the types of cells that have infiltrated the explant and assess the extent of muscle fiber formation versus fibrosis at the defect site [ 61 , 63 , 70 , 91 , 98 ]. IF labeling can be used to evaluate myogenic, angiogenic, and neurogenic differentiation within the defect site.…”

“…IF labeling can be used to evaluate myogenic, angiogenic, and neurogenic differentiation within the defect site. Similar to in vitro assessment of myogenesis using IF, MHC [ 61 , 63 , 70 , 85 , 91 , 98 ], desmin [ 65 ], and dystrophin [ 68 ] can be utilized. Pax7 has also been utilized to evaluate the restoration of muscle satellite cells within newly formed tissue [ 110 , 111 ].…”

“…Pax7 has also been utilized to evaluate the restoration of muscle satellite cells within newly formed tissue [ 110 , 111 ]. To assess angiogenesis, CD31 [ 63 , 91 ], von Willebrand factor (vWF) [ 70 , 85 ], α-smooth muscle actin [ 70 , 85 ], and isolectin [ 70 ] can be utilized. In addition, α-bungarotoxin (AChR) [ 85 , 98 ] and β III tubulin [ 65 , 98 ] can be utilized to assess neurogenesis, whereas F4/80 [ 70 , 91 ] and Mac-3 [ 70 ] immunogenic markers can determine if inflammation is occurring in the defect site because of the presence of macrophages.…”

“…Patel et al. utilized an electrospun blend of PCL and muscle dECM for the regeneration of muscle in a mouse VML model [ 91 ]. The authors compared this treatment to electrospun PCL alone and found that the addition of dECM promoted the presence of M2 macrophages and increased myogenic differentiation.…”