Innate immune protein surfactant protein-A (SP-A) in preterm and term placenta

Abstract

TERM PLACENTA COLIN MACNEILL, SARA KENNEDY, TOM LIN, ZHENWU LIN, DEBRA SHEARER, JUDITH WEISZ, Pennsylvania State University College of Medicine, Obstetrics and Gynecology, Hershey, Pennsylvania, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, Pennsylvania State University College of Medicine, Cellular & Molecular Physiology, Hershey, Pennsylvania OBJECTIVE: We sought to determine the presence, localization and concentration of SP-A in preterm and term placentae. STUDY DESIGN: We conducted an immunohistochemical, immunoblot, RT-PCR and converted-RFLP analysis of 17 placentae delivered before 36 weeks and 15 delivered after 37 weeks. Chorion and decidua were disected, and proteins separated on a 1-D gel. Immunoblot densitometry values were analyzed for an association between SP-A levels, preterm/term delivery and presence of chorioamnionitis. Converted RFLP, from RT-PCR products, was used to determine if messages were transcribed from the SP-A1 or SP-A2 gene. RESULTS: SP-A was identified by immunohistology in the subchorionic plate and villous and extravillous trophoblasts. Immunostaining appeared more intense in the subchorionic plate of placentae with chorioamnionitis. Immunoblot analysis demonstrated that SP-A was increased in the chorionic plate in term placentae (p = 0.001). One-way ANOVA was used to determine if chorioamnionitis had an effect on the increase in SP-A concentration at term. In placentae with chorioamnionitis, SP-A concentration in the chorionic plate was greater in those delivered at term (p = 0.002). Similarly, in placentae without chorioamnionitis, SP-A was increased in the subgroup delivered at term (p = 0.02). SP-A transcripts were identified by RT-PCR from RNA isolated from chorionic and decidual plate. Notably, both SP-A1 and SP-A2 genes are transcribed in term placentae whereas only SP-A2 is transcribed in preterm placentae. CONCLUSION: This study demonstrates that SP-A is present in preterm and term placentae, and is increased in the chorionic plate in term placentae. The increase in SP-A in term placenta may be associated with gestational age and unrelated to preterm birth. Alternatively, given that SP-A2 has been shown to have greater inflammatory activity in vitro, another feature of placental SP-A, such as the ballance of SP-A2/SP-A1, may be associated with preterm birth.