title: Tissue microarray: an effective high-throughput method to study the placenta for clinical and research purposes.
abstract: OBJECTIVE
  Tissue microarray (TMA) technology allows simultaneous examination of the expression of many molecular markers (protein, mRNA, DNA, etc.) with high-throughput. The application of this technology, to date, has been largely confined to the study of cancer. Placental pathology poses unique challenges because of the size of the organ, its complex anatomy, as well as its histological heterogeneity. The objective of this study was to assess the feasibility and efficiency of TMAs for immunohistochemistry and in situ hybridization of placental tissues.
  
  
  METHODS
  TMAs were constructed using an automated tissue arrayer. Standard 0.6-mm or 1-mm microarray needles were used. Villous parenchyma, basal plate, and chorioamniotic membranes were targeted in each block. Five mum-thick TMA sections underwent immunohistochemical analysis of both cytoplasmic and nuclear antigens using a panel of antibodies against a variety of cytoplasmic [cytokeratin-7, vascular endothelial growth factor (VEGF), and protein Z], membranous (endoglin), and nuclear (c-fos and c-jun) antigens. mRNA in situ hybridization for surfactant protein A (SP-A) and chromogenic in situ hybridization for the Y chromosome (DYZ1) were also performed.
  
  
  RESULTS
  Validation of TMA immunoreactivity demonstrated comparable results with corresponding whole sections. When a two-tiered scoring system (positive/negative) was employed, there was agreement between two and three cores and whole tissue sections (kappa>0.7). When a three-tiered scoring system (negative, weak-positive, or strong-positive) was used, the data from three cores showed the highest agreement with whole tissue sections (kappa >0.7). In situ hybridization experiments for mRNA and DNA were also successful in that the signals were readily detectable. Successful transfer from the donor block to the recipient block differed according to the anatomical compartment. The transfer efficiency of villous parenchyma, basal plate, and chorioamniotic membranes were 96.9% (875/903), 76.7% (115/150), and 75.4% (224/297), respectively.
  
  
  CONCLUSIONS
  TMA is a practical and effective tool for high-throughput molecular analysis of the human placenta. Duplicate and triplicate cores offer agreement with whole tissue sections for two-category distinction immunostaining. TMA also affords relevant results from in situ hybridization experiments for mRNA and DNA. The major advantages are the conservation of tissues and reagents, simultaneous comparison of molecular markers in different anatomical compartments of the placenta, and reduction of experimental error.
authors.affiliation: Perinatology Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA.
authors.forename: Karina
authors.initials: K
authors.lastname: Richani
authors.forename: Roberto
authors.initials: R
authors.lastname: Romero
authors.forename: Yeon Mee
authors.initials: YM
authors.lastname: Kim
authors.forename: Enola
authors.initials: E
authors.lastname: Cushenberry
authors.forename: Eleazar
authors.initials: E
authors.lastname: Soto
authors.forename: Yu Mi
authors.initials: YM
authors.lastname: Han
authors.forename: Jimmy
authors.initials: J
authors.lastname: Espinoza
authors.forename: Chong Jai
authors.initials: CJ
authors.lastname: Kim
mesh_terms: D015415:Biomarkers / Q000032:analysis; D035843:Biomedical Research / Q000379:methods; D004247:DNA / Q000032:analysis; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D046228:Microarray Analysis / Q000295:instrumentation / Q000379:methods*; D010920:Placenta / Q000166:cytology* / Q000473:pathology*; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D012333:RNA, Messenger; D004247:DNA