(C-87) Porous Granular Hydrogels Improve Cell Invasion and Muscle Remodeling after Volumetric Muscle Loss in Mice

Friday, October 13, 2023

9:30 AM – 10:30 AM PDT

Location: Exhibit Hall - Row C - Poster # 87

Presenting Author(s)

Gabrielle I. Tanner

Undergraduate Researcher
Purdue University
Columbus, Ohio, United States

Co-Author(s)

LS

Leia Schiltz

Undergraduate Researcher
Purdue University, United States
MF

Marxa Figueiredo

Associate Professor
Purdue University, United States

Primary Investigator(s)

Taimoor H. Qazi

Assistant Professor
Purdue University, United States

Introduction:: Volumetric muscle loss (VML) is marked by excessive scar tissue deposition and functional disability following severe muscle trauma wherein the volume of tissue lost exceeds the body’s regenerative capacity [1]. There is currently no effective treatment for VML, but bioengineering interventions such as biomaterials that fill the VML defect to support tissue repair are a promising strategy [2]. However, traditional biomaterials used for this purpose are either non-porous or have rigid form, making them challenging to implant and impenetrable to endogenous cells. In the present study, we tested the effects of granular hydrogels — an emerging class of injectable and porous biomaterials — on muscle repair, hypothesizing that their porosity will support native cell invasion and their flowability will permit conformable defect filling, leading to more effective repair compared to bulk hydrogels.

Materials and Methods:: Norbornene-modified hyaluronic acid (Nor-HA) was combined with DTT and LAP, loaded into a syringe, and photocrosslinked under UV light (Fig.1a). Microgel fragments (Fig.2b) were produced by extruding the bulk hydrogels through a series of syringe needles with decreasing inner diameter, as previously described [3]. Fragmented microgels were then sorted via 100 μm strainer to remove particles less than 100 μm, and vacuum filtered to obtain microporous granular hydrogels (Fig.1c). Bilateral VML injuries were then created in the tibialis anterior (TA) muscles of 12-14 week old C57BL/6 mice using a 2.5 mm biopsy punch, into which granular or bulk hydrogels were implanted (Fig.1d). At 1 week after injury and implantation, the mice were euthanized and muscles were harvested, fixed in 4% PFA, embedded in OCT Tissue-Tek, and cryosectioned into 15 μm cross-sections that were stained with Hoechst (nuclei) and either F-actin (myofibers), Pax7 (satellite cells), or embryonic myosin heavy chain (newly regenerated myofibers). Images were obtained on an inverted fluorescence microscope and analyzed using ImageJ.

Results, Conclusions, and Discussions:: Nor-HA crosslinked hydrogels with a stiffness of ~12 kPa mimicking native muscle stiffness were used to prepare fragmented microgels with equivalent diameter in the range 80-250 μm. Microgels were vacuum filtered to obtain granular hydrogels with an average porosity of 10%. At 1 week after implantation into a VML defect, invasion of non-myogenic and myogenic cells, and newly regenerated myofibers into the defect region were found to be significantly greater in the granular hydrogel group compared to the bulk hydrogel group (Fig.1e-f), providing the first evidence of the efficacy of granular hydrogels in the effective treatment of VML injuries.

Acknowledgements (Optional): :

References (Optional): :

Carnes, M. E., & Pins, G. D. (2020). Skeletal Muscle Tissue Engineering: Biomaterials-Based Strategies for the Treatment of Volumetric Muscle Loss. 7(3), 85–85. https://doi.org/10.3390/bioengineering7030085

Corona, B. T., Wenke, J. C., & Ward, C. L. (2016). Pathophysiology of Volumetric Muscle Loss Injury. 202(3-4), 180–188. https://doi.org/10.1159/000443925

Muir, V. J., Prendergast, M. E., & Burdick, J. A. (2022). Fragmenting Bulk Hydrogels and Processing into Granular Hydrogels for Biomedical Applications. 183. https://doi.org/10.3791/63867