Pro-regenerative Extracellular Matrix Hydrogel Prevents and Mitigates Pathological Alterations of Pelvic Muscles Following Birth Injury

Abstract

Pelvic floor disorders, which include pelvic organ prolapse, and urinary and fecal incontinence, affect millions of women globally and represent a major public health concern. Pelvic floor muscle (PFM) dysfunction has been identified as one of the leading risk factors for the development of these morbid conditions. Even though childbirth, specifically vaginal delivery, has been long recognized as the most important potentially modifiable risk factor for PFM injury, the precise mechanisms of PFM dysfunction following childbirth remain elusive. In this study we demonstrate that PFMs undergo atrophy and severe fibrosis in parous women with symptomatic pelvic organ prolapse compared to age-matched nulliparous cadaveric donors without history of pelvic floor disorders. These pathological alterations are recapitulated in the pre-clinical rat model of simulated birth injury. The transcriptional signature of PFMs post-injury demonstrates a sustained inflammatory response, impairment in muscle anabolism, and persistent expression of extracellular matrix (ECM) remodeling genes. Next, we evaluated the administration of acellular injectable skeletal muscle extracellular matrix hydrogel for the prevention and mitigation of these pathological alterations. Treatment of PFMs with the biomaterial either at the time of birth injury or 4 weeks post-injury reduced muscle atrophy and mitigated fibrotic degeneration. By evaluating gene expression, we demonstrate that these changes are mainly driven by the hydrogel-induced modulation of the immune response and intramuscular fibrosis, as well as enhancement of the endogenous myogenesis. This work furthers our understanding of PFM birth injury and demonstrates proof-of-concept for a new pragmatic pro-regenerative biomaterial approach for treating injured PFMs.

Repeated birth injuries lead to pelvic floor muscle dysfunction and impairment in regeneration

“…For histological outcomes, Cohen's d effect size of 5.2, obtained from our previous study comparing morphological outcomes between animals subjected to a single SBI and unperturbed controls 7 , was used to determine sample size. Power calculation yielded 3 animals/time point to achieve 80% power at a significance level of 0.05.…”

“…For the primary mechanical outcome of interest, the specific peak force, sample size calculation (G*power software) yielded 7 animals/time point based on Cohen’s d effect size of 1.7 obtained from the preliminary experiments, to achieve 80% power at a significance level of 0.05. For histological outcomes, Cohen’s d effect size of 5.2, obtained from our previous study comparing morphological outcomes between animals subjected to a single SBI and unperturbed controls 7 , was used to determine sample size. Power calculation yielded 3 animals/time point to achieve 80% power at a significance level of 0.05.…”

“…To investigate potential mechanisms behind the profound reduction in fiber size, impairment in regeneration and muscle fibrosis after repeated injuries, we then performed a gene expression study capitalizing on a customized Nanostring panel previously utilized 7 . PCa was harvested at acute, subacute and long-term time points as with a single SBI to analyze pathways essential for muscle regeneration after an injury [23][24][25] .…”

Future Challenges and Opportunities of Extracellular Matrix Hydrogels in Female Reproductive Medicine

“…Duran et al patented a porcine skeletal muscle ECM hydrogel (SKM) to treat pelvic floor disorders (WO 2018/213375 A1). This biomaterial was applied in a rat model of simulated birth injury (SBI) to assess its efficacy as a pro-regenerative scaffold [ 118 ]. Briefly, after inducing and validating the SBI model, SKM or saline was either injected immediately or four weeks later after birth, with the latter injection designed to mimic the timing of a routine post-partum visit.…”

“…On the right, in vivo models where ECM hydrogels have been applied. References are indicated adjacent to each application [ 40 , 52 , 106 , 107 , 108 , 109 , 110 , 111 , 117 , 118 ]. Created with .…”