Mechanisms and impact of pregnancy-induced adaptations in pelvic floor muscles

项目摘要 产妇分娩损伤是导致盆底肌功能障碍的主要危险因素， 骨盆底疾病尽管如此，目前不可能在分娩前进行个性化风险评估， PFM产伤对功能相关肌肉成分的影响还没有很好的定义。因此，在本发明中， 除了剖腹产外，没有其他预防措施，可用的治疗方法也非常有限。 利用大鼠模型，我们最近发现在PFMs中存在妊娠诱导的适应， 特别是通过连续增加肌节或肌节发生的纤维伸长，以及 细胞外基质（ECM）含量和肌肉硬度。这些重要的发现导致了我们的整体 假设：1）妊娠诱导的适应性使PFMs能够承受机械需求 与分娩有关，2）当这些适应不足或过度时， PFMs封装。我们将使用大鼠模型在3个独立但相互关联的目的中检验这些假设。目的 1将集中于确定PFM妊娠诱导的适应对机械损伤的保护作用。 产伤对产后肌肉恢复的影响。使用晚期妊娠、非妊娠和 中期妊娠大鼠，我们将确定PFMs对菌株的急性和长期反应，当 妊娠引起的适应性变化要么存在，要么不存在，要么不完全。目标2将侧重于机制 这驱动了PFMs中妊娠诱导的适应性，假设更大的机械负荷 增大的子宫，结合妊娠的激素环境，导致肉瘤发生，ECM增加 内容和更高的肌肉硬度。为了确定机械和动力学的独立和综合影响， 内分泌提示与妊娠有关的PFM可塑性，我们将使用单侧妊娠大鼠和一种新的 单侧子宫角负重的非妊娠大鼠模型。目标3将测试松弛素，一种关键的 妊娠激素，推测可调节肌角化和肌内ECM 重构，是必要的妊娠诱导的适应性PFMs。我们会中和内源性的 松弛素在妊娠大鼠和评估松弛素剥夺对收缩，ECM，和细胞的影响， PFMs的组成部分。然后，我们将管理松弛素非妊娠动物和不重 加载子宫角，以测试松弛素是否足以单独驱动PFM适应或与 增加机械负荷。总之，这些目标将阐明怀孕和分娩对PFM的影响 机械、自适应和再生性能。这些创新实验的结果将作为 最大限度地提高保护性适应和再生的新战略的发展框架， 骨盆底肌肉如果成功的话，这些策略可以将目前的临床模式转向预防 骨盆底肌肉产伤和治疗，保留和恢复产后功能的受伤 肌肉，这两个都是必要的有意义的进展发生在女性盆腔医学。

PROJECT SUMMARY Maternal childbirth injury is the leading risk factor for pelvic floor muscle (PFM) dysfunction and the resultant pelvic floor disorders. Despite this, individualized risk assessment prior to delivery is currently not possible and the impact of PFM birth injury on the functionally relevant muscle components is not well defined. As a result, there are no preventative strategies beyond Cesarean section and available treatments are severely limited. Using the rat model, we recently discovered the existence of pregnancy-induced adaptations in the PFMs, specifically fiber elongation via serial addition of sarcomeres, or sarcomerogenesis, and changes in extracellular matrix (ECM) content and muscle stiffness. These important discoveries led to our overall hypotheses that 1) pregnancy-induced adaptations prepare PFMs to withstand the mechanical demands associated with parturition, and 2) when these adaptations are either deficient or are exceeded, injury to the PFMs ensues. We will test these hypotheses in 3 independent but interrelated Aims, using the rat model. Aim 1 will focus on determining the protective effect of PFM pregnancy-induced adaptations against mechanical injury and the impact of birth injury on postpartum muscle recovery. Using late-pregnant, non-pregnant, and mid-pregnant rats, we will determine the acute and long-term response of the PFMs to strains, when pregnancy-induced adaptations are either present, absent, or incomplete. Aim 2 will focus on the mechanisms that drive pregnancy-induced adaptations in the PFMs, with the hypothesis that greater mechanical load from the enlarged uterus, combined with hormonal milieu of pregnancy, lead to sarcomerogenesis, increased ECM content, and higher muscle stiffness. To determine the independent and combined effects of mechanical and endocrine cues associated with pregnancy on PFM plasticity, we will use unilaterally pregnant rats and a novel non-pregnant rat model with unilaterally weight-loaded uterine horns. Aim 3 will test whether relaxin, a critical pregnancy hormone that has been speculated to regulate sarcomerogenesis and intramuscular ECM remodeling, is necessary for pregnancy-induced adaptations in the PFMs. We will neutralize endogenous relaxin in pregnant rats and assess the influence of relaxin deprivation on the contractile, ECM, and cellular components of the PFMs. We will then administer relaxin to non-pregnant animals with and without weight loaded uterine horns, to test whether relaxin is sufficient to drive PFM adaptations alone or in conjunction with increased mechanical load. Together, these Aims will elucidate the impact of pregnancy and delivery on PFM mechanical, adaptive and regenerative properties. The results of these innovative experiments will serve as a framework for the development of novel strategies for maximizing protective adaptations and regeneration in pelvic floor muscles. If successful, such strategies could shift the current clinical paradigm towards prevention of pelvic floor muscle birth trauma and treatments that preserve and restore postpartum function of injured muscles, both of which are essential for meaningful advances to occur in female pelvic medicine.