447: Amniochorion apoptosis and autophagy: novel insights into the mechanisms of PPROM after fetoscopic laser surgery (FLS) for twin twin transfusion syndrome (TTTS)

Abstract

into the mechanisms of PPROM after fetoscopic laser surgery (FLS) for twin twin transfusion syndrome (TTTS) Ramesha Papanna, Lovepreet Mann, Kenneth Moise, Themis Kyriakides, Guomao Zhao, Pedro Argoti, Catalin Buhimschi, Irina Buhimschi Yale University, Ob/Gyn & Reprod. Sci., New Haven, CT, University of Texas Medical School at Houston, Obstetrics, Gynecology and Reproductive Sciences, Houston, TX, Yale University, Biomedical Engineering & Pathology, New Haven, CT OBJECTIVE: Laser photocoagulation of chorionic plate vessels has emerged as an effective treatment of TTTS. This therapy poses major post-intervention challenges such as PPROM. Traditionally, this complication is interpreted as an iatrogenic mechanic event. We tested the hypothesis that following FLS, fetal membranes become susceptible to PPROM through activation of apoptosis and autophagy pathways in the amniochorion cells. STUDY DESIGN: Extra-placental membranes from 31 pregnancies that underwent FLS for TTTS (GA procedure: 20 3w, GA birth: 30 4w, PPROM n 9) were prospectively collected at birth. Trocar insertion site (recipient sac), fetal membranes of the recipient and donor sacs, and the inter-twin membrane were evaluated for tissue morphology and connective tissue constituents using Masson’s trichrome and Movat’s staining. Collagen histochemistry was assessed with Sirius red and quantified by image analysis. Amniochorion sections were stained using various markers of proliferation (Ki67), mesenchymal and epithelial features (vimentin, cytokeratin), autophagy (beclin-1, LC3) and apoptosis (DNA fragmentation). CRL tissues came from monochorionic/diamniotic twin (idiopathic PTB, n 4) and healthy term singleton (elective CS, n 8) gestations. RESULTS: Histological hallmarks of healing (angiogenesis, collagen deposition, granulation) or cellular proliferation (Ki67 staining) were absent at the trocar insertion site. Compared to CRLs, there was global loss of physiologic collagen organization in both amnion and chorion of the recipient and the inter-twin membrane, but not the donor sac (P .001). The recipient amniochorion showed features of autophagy (beclin-1 & LC3 in clusters) and higher apoptotic index (highest at the trocar insertion site) compared to the donor sac (P .03). CONCLUSION: FLS for TTTS is associated with generalized alteration of structural integrity and amniochorion cellular damage of the recipient’s sac that likely contribute to PPROM.