Keratin Hydrogel EnhancesIn VivoSkeletal Muscle Function in a Rat Model of Volumetric Muscle Loss

Abstract

Volumetric muscle loss (VML) injuries exceed the considerable intrinsic regenerative capacity of skeletal muscle, resulting in permanent functional and cosmetic deficits. VML and VML-like injuries occur in military and civilian populations, due to trauma and surgery as well as due to a host of congenital and acquired diseases/syndromes. Current therapeutic options are limited, and new approaches are needed for a more complete functional regeneration of muscle. A potential solution is human hair-derived keratin (KN) biomaterials that may have significant potential for regenerative therapy. The goal of these studies was to evaluate the utility of keratin hydrogel formulations as a cell and/or growth factor delivery vehicle for functional muscle regeneration in a surgically created VML injury in the rat tibialis anterior (TA) muscle. VML injuries were treated with KN hydrogels in the absence and presence of skeletal muscle progenitor cells (MPCs), and/or insulin-like growth factor 1 (IGF-1), and/or basic fibroblast growth factor (bFGF). Controls included VML injuries with no repair (NR), and implantation of bladder acellular matrix (BAM, without cells). Initial studies conducted 8 weeks post-VML injury indicated that application of keratin hydrogels with growth factors (KN, KN+IGF-1, KN+bFGF, and KN+IGF-1+bFGF, n = 8 each) enabled a significantly greater functional recovery than NR (n = 7), BAM (n = 8), or the addition of MPCs to the keratin hydrogel (KN+MPC, KN+MPC+IGF-1, KN+MPC+bFGF, and KN+MPC+IGF-1+bFGF, n = 8 each) (p < 0.05). A second series of studies examined functional recovery for as many as 12 weeks post-VML injury after application of keratin hydrogels in the absence of cells. A significant time-dependent increase in functional recovery of the KN, KN+bFGF, and KN+IGF+bFGF groups was observed, relative to NR and BAM implantation, achieving as much as 90% of the maximum possible functional recovery. Histological findings from harvested tissue at 12 weeks post-VML injury documented significant increases in neo-muscle tissue formation in all keratin treatment groups as well as diminished fibrosis, in comparison to both BAM and NR. In conclusion, keratin hydrogel implantation promoted statistically significant and physiologically relevant improvements in functional outcomes post-VML injury to the rodent TA muscle.

Biomimetic sponges improve muscle structure and function following volumetric muscle loss

“…To the best of our knowledge, a significant increase in myofiber number and muscle function has never been reported with the implantation of an acellular ECM scaffold in a full-thickness VML model. The use of decellularized scaffolds in VML injuries have shown conflicting results with studies reporting either no improvement [15,29,30], exacerbated force deficits [31], or modest improvements in force production [32].…”

In Vivo Evaluation of Three-Dimensional Printed, Keratin-Based Hydrogels in a Porcine Thermal Burn Model

“…38 Sterilization methods have been widely studied to determine their effects on hydrogel networks. Gamma radiation has been used before to sterilize keratin-based constructs 15,16,28,31,32 ; other methods include UV irradiation, ethanol, or sterile water rinsing. 8,25,38 Gamma radiation is generally accepted as a safe method to reduce bacterial proliferation without inducing cytotoxic side effects.…”

“…Keratin-based biomaterials have been successfully used for the delivery of growth factors (e.g., insulin-like growth factor-1, basic fibroblast growth factor [bFGF]), 30,31 progenitor cells (e.g., skeletal muscle myoblasts), 16 and antimicrobial agents (ciprofloxacin), 32 among other molecules. In this study, we studied Halofuginone-laden keratin scaffolds for the in vivo treatment of burn, particularly the development of an individualized keratin-based dressing capable of encouraging quick wound healing with the release of Halofuginone.…”

Therapeutic Approaches for Volumetric Muscle Loss Injury: A Systematic Review and Meta-Analysis

“…The adjusted overall ES was still highly significant and its magnitude would be considered moderate. Potential conflicts of interest were evaluated by involvement of the company developing the treatment tested, noted in one study 35 that disclosed funding, support, or gift in kind for the treatment tested (this study had two independent injury models) directly, and four studies [52][53][54][55] noted authors with roles in various corporations. Five collaborative research groups were identified across the included studies.…”