Placental progesterone biosynthesis in preterm pregnancy

孕酮(P)在妊娠期间维持子宫静止，观察到大多数哺乳动物的分娩发生在母体P下降之后。虽然人类P没有随着分娩的开始而显著下降，但最近的两项随机、双盲、安慰剂对照临床试验表明，与安慰剂治疗组相比，补充P可以减少早产(PTB)的复发率33-50%。这些孕激素代表了预防早产的第一种疗法，而不是优化对早产儿的护理。从胎盘中的胆固醇从头合成P需要胆固醇进入线粒体。P450侧链裂解(P450scc)和3β-羟基类固醇脱氢酶I型(3bHSD-1)参与胆固醇向P的转化。MLN64蛋白参与了胆固醇转运至胎盘线粒体的类固醇合成过程。我们假设胎盘中磷合成的过早减少是肺结核的一个促成因素，因此一些妇女需要额外的磷来预防肺结核。胎盘P450scc和3bHSD-1mRNA将用实时RT-PCR定量，酶活性分析将检测胆固醇到孕烯醇酮和孕烯醇酮到孕酮的转化，而蛋白质水平将通过蛋白质分析和相对密度研究进行评估。将测量胎盘孕烯醇酮和磷的浓度。MLN64及其可促进类固醇合成的蛋白水解体将在这些标本中通过Western分析进行研究。PTB和17P处理组将与胎龄匹配的对照组进行比较。我们期望在成功应用17P预防复发肺结核的妇女中，P途径的表达将会减少。确定17P的机制将允许对有肺结核风险的特定女性进行治疗，而不会过度治疗那些没有反应的女性。

Progesterone (P) maintains uterine quiescence in pregnancy, as evidenced by the observation that the onset of labor in most mammals occurs following a drop in maternal P. Though no measurable decrease in human P is noted with the onset of labor, two recent randomized, double-blind, placebo-controlled clinical trials demonstrated that P supplementation can reduce the reoccurrence of preterm birth (PTB) by 33-50% compared to placebo-treated pregnancies. These progestational agents represent the first therapy that addresses prevention of prematurity rather than optimization of care for the premature infant. The de novo synthesis of P from cholesterol in the placenta requires that cholesterol enter the mitochondria. P450 side chain cleavage (P450scc) and 3beta-hydroxysteroid dehydrogenase type I (3bHSD-1) act to convert cholesterol to P. MLN64 protein has been implicated in the initial cholesterol transport into the placental mitochondria for steroidogenesis. We hypothesize that a premature decrease in P synthesis in the placenta is a contributing factor in PTB, such that some women will need extra P to prevent PTB. Placental P450scc and 3bHSD-1 mRNA will be quantified using real-time RT-PCR and enzyme activity assays will be performed examining the conversion of cholesterol to pregnenolone and pregnenolone to progesterone, while protein levels will be assessed by western analysis and relative densitometry studies. Placental pregnenolone and P concentrations will be measured. MLN64 and its proteolytic variants which can enhance steroidogenesis will be studied in these same specimens by western analysis.The PTB and the 17P treated groups will be compared to gestationally age matched controls. We expect that decreased expression of the P pathway will be seen in women who respond successfully to 17P in preventing recurrent PTB. Determining the mechanism of 17P will allow therapy to specific women who are at risk for PTB without overtreatment of women who cannot respond.