Placental progesterone biosynthesis in preterm pregnancy

孕酮(P)在怀孕期间维持子宫静止，这一点可以通过观察大多数哺乳动物在母体P下降后开始分娩得到证明。尽管人类P没有随着分娩开始而明显下降，但最近的两项随机、双盲、安慰剂对照的临床试验表明，与安慰剂治疗的妊娠相比，补充P可以减少早产（PTB）的复发率33-50%。这些孕激素代表了第一个治疗，解决了早产的预防，而不是早产儿护理的优化。从胎盘中的胆固醇重新合成P需要胆固醇进入线粒体。P450侧链切割（P450scc）和3β -羟基类固醇脱氢酶I型（3bHSD-1）作用于将胆固醇转化为P. MLN64蛋白，这与胆固醇最初运输到胎盘线粒体以形成类固醇有关。我们假设胎盘中P合成的过早减少是PTB的一个促成因素，因此一些妇女需要额外的P来预防PTB。采用实时RT-PCR对胎盘P450scc和3bHSD-1 mRNA进行定量，并进行酶活性测定，检测胆固醇向孕烯醇酮和孕烯醇酮向黄体酮的转化，同时通过western分析和相对密度测定法评估蛋白质水平。测定胎盘孕烯醇酮和P的浓度。MLN64及其能促进类固醇生成的蛋白水解变体将在这些标本中进行western分析研究。PTB和17P治疗组将与胎龄匹配的对照组进行比较。我们期望在对17P有效预防复发性肺结核的妇女中可以看到P通路表达减少。确定17P的作用机制将允许对有患肺结核风险的特定妇女进行治疗，而不会对没有反应的妇女进行过度治疗。

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.