Mechanical impact of parturition‐related strains on rat pelvic striated sphincters
Year: 2019
Type: article
Abstract: Aims To define the operational resting sarcomere length (Ls) of the female rat external urethral sphincter (EUS) and external anal sphincter (EAS) and to determine the mechanism of parturition‐related injury of EUS and EAS using a simulated birth injury (SBI) vaginal distention model. Methods EUS and EAS of 3‐month‐old Sprague‐Dawley control and injured rats were fixed in situ, harvested, and microdissected for Ls measurements and assessment of ultrastructure. EUS and EAS function was determined at baseline, and immediately and 4 weeks after SBI, using leak point pressure (LPP) and anorectal manometry (ARM), respectively. Operational L s was compared to species‐specific optimal L s using one sample Student's t test. Data (mean ± SD) were compared between groups and time points using repeated measures one‐way analysis of variance, followed by Tukey's post hoc pairwise comparisons, with significance set to 0.05. Results The operational resting Ls of both sphincters (EUS: 2.09 ± 0.07 µm, EAS: 2.02 ± 0.03 µm) was significantly shorter than optimal rat Ls of 2.4 µm. Strains imposed on EUS and EAS during SBI resulted in significant sarcomere elongation and disruption, compared with the controls (EUS: 3.09 ± 0.11 µm, EAS: 3.37 ± 0.09 µm). Paralleling structural changes, LPP and ARM measures were significantly lower immediately (LPP: 21.5 ± 1.0 cmH2O, ARM: 5.1 ± 2.31 cmH2O) and 4 weeks (LPP: 27.7 ± 1.3cmH2O, ARM: 2.5 ± 1.0 cmH2O) after SBI relative to the baseline (LPP: 43.4 ± 8.5 cmH2O, ARM: 8.2 ± 2.0 cmH2O); P < 0.05. Conclusions Analogous to humans, the short resting Ls of rat EUS and EAS favors their sphincteric function. The insult experienced by these muscles during parturition leads to sarcomere hyperelongation, myofibrillar disruption, and dysfunction of the sphincters long‐term.
Source: Neurourology and Urodynamics
DOI: 10.1002/nau.23946
Language: English
Subfield: Rheumatology
Field: Medicine
Domain: Health Sciences
Open Access status: green
Funders: Foundation for the National Institutes of Health, National Institutes of Health, National Institute on Aging, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institute of Child Health and Human Development, National Center for Advancing Translational Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development
Awards: Predoctoral Training in Translational Musculoskeletal Research, Pathways underlying recovery of injured urethral sphincter and a novel regenerative biomaterial intervention, Impact of Aging on Structure and Function of Pelvic Floor Muscles, Injectable Tissue-Specific Extracellular Matrix Hydrogel for Pelvic Skeletal Muscle Regeneration Following Birth Injury, G8611548638, UC San Diego Clinical and Translational Research Institute, Mechanisms and Impact of Pregnancy-Induced Adaptations in Pelvic Floor Muscles, UC San Diego Womens Reproductive Health Research Program
OpenAlex ID: W2917400245