Musculoskeletal Research Center, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
Ann Biomed Eng. 2011 Jan;39(1):549-58. doi: 10.1007/s10439-010-0153-9. Epub 2010 Sep 8.
Remodeling of vaginal extracellular matrix and smooth muscle likely plays a critical role in reducing the risk of maternal injury during vaginal delivery by altering the mechanical properties to increase distension and reduce stress. Long-Evans rats were divided into five groups to examine the passive mechanical and active contractile properties throughout pregnancy and postpartum: virgin (n=17), mid-pregnant (Day 14-16, n=12), late-pregnant (Day 20-22, n=14), immediate postpartum (0-2 h after delivery, n=14), and 4 week postpartum (n=15). Longitudinal sections of vaginal tissue were loaded to failure uniaxially for passive mechanical or active contractile properties were examined. For passive mechanics, the tangent modulus decreased 45% by mid-pregnancy and immediately postpartum (p<0.001). The ultimate strain continuously increased up to 43% higher than virgin animals (p=0.007) in the immediate postpartum group. For active mechanics, the maximal contractile force was 36-56% lower through immediate postpartum animals, and was significantly more sensitive to K+ throughout pregnancy and postpartum (p=0.003). The changes observed in the passive and active properties of the rat vagina are consistent with what would be expected from a tissue that is remodeling to maximize its ability to distend at the time of vaginal delivery to facilitate passage of the fetus with minimal injury.
阴道细胞外基质和平滑肌的重塑可能在降低阴道分娩时产妇损伤的风险方面发挥着关键作用，其通过改变机械性能来增加扩张度和降低压力。将长耳大白鼠分为五组，以研究在整个妊娠和产后期间的被动机械和主动收缩特性：处女组（n=17）、妊娠中期组（第 14-16 天，n=12）、妊娠晚期组（第 20-22 天，n=14）、产后即刻组（分娩后 0-2 小时，n=14）和产后 4 周组（n=15）。对阴道组织的纵向切片进行单轴加载至失效，以检查被动机械或主动收缩特性。对于被动力学，妊娠中期和产后即刻，切线模量降低了 45%（p<0.001）。即刻产后组的最终应变持续增加，比处女组高 43%（p=0.007）。对于主动力学，产后即刻的最大收缩力降低了 36-56%，并且在整个妊娠和产后期间对 K+的敏感性显著增加（p=0.003）。在大鼠阴道的被动和主动特性中观察到的变化与在阴道分娩时最大限度地扩张组织以促进胎儿通过而最小化损伤的组织的重塑相一致。
