title: Establishment and characterization of a spontaneously immortalized trophoblast cell line (HPT-8) and its hepatitis B virus-expressing clone.
abstract: BACKGROUND
  Most trophoblast cell lines currently available to study vertical transmission of hepatitis B virus (HBV) are immortalized by viral transformation. Our goal was to establish and characterize a spontaneously immortalized human first-trimester trophoblast cell line and its HBV-expressing clone.
  
  
  METHODS
  Chorionic villi of Asian human first-trimester placentae were digested with trypsin and collagenase I to obtain the primary trophoblast cell culture. A spontaneously immortalized trophoblast cell line (HPT-8) was analyzed by scanning and transmission electron microscopy, cell cycle analysis, immunohistochemistry and immunofluorescence. HPT-8 cells were stably transfected with the adr subtype of HBV (HPT-8-HBV) and characterized by PCR and enzyme-linked immunosorbent assay.
  
  
  RESULTS
  We obtained a clonal derivative of a spontaneously immortalized primary cell clone (HPT-8). HPT-8 cells were epithelioid and polygonal, and formed multinucleate, giant cells. They exhibited microvilli, distinct desmosomes between adjacent cells, abundant endoplasm, lipid inclusions and glycogen granules, which are all characteristic of cytotrophoblasts. HPT-8 cells expressed cytokeratin 7, cytokeratin 18, vimentin, cluster of differentiation antigen 9, epidermal growth factor receptor, stromal cell-derived factor 1 and placental alkaline phosphatase. They secreted prolactin, estradiol, progesterone and hCG, and were positive for HLA-G, a marker of extravillous trophoblasts. HPT-8-HBV cells were positive for HBV relaxed-circular, covalently closed circular DNA and pre-S sequence. HPT-8-HBV cells also produced and secreted HBV surface antigen and HBV e antigen.
  
  
  CONCLUSIONS
  We established a trophoblast cell line, HPT-8 and its HBV-expressing clone which could be valuable in exploring the mechanism of HBV viral integration in human trophoblasts during intrauterine infection.
authors: Department of Epidemiology, Fourth Military Medical University, Xi'an 710032, Shanxi, People's Republic of China.
authors: Lei
authors: L
authors: Zhang
authors: Weilu
authors: W
authors: Zhang
authors: Chen
authors: C
authors: Shao
authors: Jingxia
authors: J
authors: Zhang
authors: Ke
authors: K
authors: Men
authors: Zhongjun
authors: Z
authors: Shao
authors: Yongping
authors: Y
authors: Yan
authors: Dezhong
authors: D
authors: Xu