Cell-Derived Extracellular Matrix Fiber Scaffolds Improve Recovery from Volumetric Muscle Loss.

There are currently no surgical procedures that effectively address the treatment of volumetric muscle loss (VML) injuries that has motivated the development of implantable scaffolding. In this study, the effectiveness of an allogenic scaffold fabricated using fibers built from the extracellular matrix (ECM) collected from muscle fibroblast cells during growth in culture was explored using a hindlimb VML injury (tibialis anterior muscle) in a rat model. Recovery outcomes (8 weeks) were explored in comparison with unrepaired controls as well previously examined allogenic scaffolds prepared from decellularized skeletal muscle (DSM) tissue (n = 9/sample group). At 8-week follow-up, we found that the repair of VML injuries using ECM fiber scaffolds in combination with an autogenic mince muscle (MM) paste significantly improved the recovery of peak contractile torque (79% ± 13% of uninjured contralateral muscle) when compared with unrepaired VML controls (57% ± 13%). Similar significant improvements were measured for muscle mass restoration (93% ± 10%) in response to ECM fiber+MM repair when compared with unrepaired VML controls (73% ± 13%). Of note, mass and contractile strength recovery outcomes for ECM fiber scaffolds were not significantly different from DSM+MM repair controls. These in vivo findings support the further exploration of cell-derived ECM fiber scaffolds as a promising strategy for the repair of VML injury with recovery outcomes that compare favorably with current tissue-sourced ECM scaffolds. Furthermore, although the therapeutic potential of ECM fibers as a treatment strategy for muscle injury was explored in this study, they could be adapted for high-throughput fabrication methods developed and routinely used by the textile industry to create a broad range of woven implants (e.g., hernia meshes) for even greater clinical impact.

Local IL-10 delivery modulates the immune response and enhances repair of volumetric muscle loss muscle injury.

This study was designed to test the hypothesis that in addition to repairing the architectural and cellular cues via regenerative medicine, the delivery of immune cues (immunotherapy) may be needed to enhance regeneration following volumetric muscle loss (VML) injury. We identified IL-10 signaling as a promising immunotherapeutic target. To explore the impact of targeting IL-10 signaling, tibialis anterior (TA) VML injuries were created and then treated in rats using autologous minced muscle (MM). Animals received either recombinant rat IL-10 or phosphate buffered saline (PBS) controls injections at the site of VML repair beginning 7 days post injury (DPI) and continuing every other day (4 injections total) until 14 DPI. At 56 DPI (study endpoint), significant improvements to TA contractile torque (82% of uninjured values & 170% of PBS values), TA mass, and myofiber size in response to IL-10 treatment were detected. Whole transcriptome analysis at 14 DPI revealed activation of IL-10 signaling, muscle hypertrophy, and lymphocytes signaling pathways. Expression of ST2, a regulatory T (Treg) cell receptor, was dramatically increased at the VML repair site in response to IL-10 treatment when compared to PBS controls. The findings suggest that the positive effect of delayed IL-10 delivery might be due to immuno-suppressive Treg cell recruitment.

Differences in colonic crypt morphology of spontaneous and colitis-associated murine models via second harmonic generation imaging to quantify colon cancer development.

BACKGROUND: Colorectal cancer remains the second leading cause of cancer death in the United States, and increased risk in patients with ulcerative colitis (a subset of inflammatory bowel disease) has motivated studies into early markers of dysplasia. The development of clinically translatable multiphoton imaging systems has allowed for the potential of in vivo label-free imaging of epithelial crypt structures via autofluorescence and/or second harmonic generation (SHG). SHG has been used to investigate collagen structures in various types of cancer, though the changes that colorectal epithelial collagen structures undergo during tumor development, specifically colitis-associated tumors, have not been fully investigated. METHODS: This study used two murine models, using A/J mice, one for spontaneous carcinoma and one for colitis-associated carcinoma, to investigate and quantify SHG image features that could potentially inform future study designs of endoscopic multiphoton imaging systems. The spontaneous tumor model comprised a series of six weekly injections of azoxymethane (AOM model). The colitis-associated tumor model comprised a single injection of AOM, followed by cycles of drinking water with dissolved dextran sodium sulfate salt (AOM-DSS model). SHG images of freshly resected murine colon were acquired with a multiphoton imaging system, and image features, such as crypt size, shape and distribution, were quantified using an automated algorithm. RESULTS: The comparison of quantified features of crypt morphology demonstrated the ability of our quantitative image feature algorithms to detect differences between spontaneous (AOM model) and colitis-associated (AOM-DSS model) murine colorectal tissue specimens. There were statistically significant differences in the mean and standard deviation of nearest neighbor (distance between crypts) and circularity between the Control cohort, AOM and AOM-DSS cohorts. We also saw significance between AOM and AOM-DSS cohorts when calculating nearest neighbor in images acquired at fixed depths. CONCLUSION: The results provide insight into the ability of SHG imaging to yield relevant data about the crypt microstructure in colorectal epithelium, specifically the potential to distinguish between spontaneous and colitis-associated murine models using quantification of crypt shape and distribution, informing future design of translational multiphoton imaging systems and protocols.