Thy-1 Differentiation Protein and Monocyte-Derived Cells During Regeneration and Aging of Human Placental Villi


  • Presented in parts at the 18th Annual Meeting of the American Society for Reproductive Immunology. Chicago, Illinois. May 9–12, 1998 (Abstract #8) and 16th World Congress on Fertility and Sterility and 54th Annual Meeting of the American Society for Reproductive Medicine, San Francisco, California. October 4–9, 1998 (Abstract # P-838).

  • Acknowledgements: We would like to thank Dr. Rosemarie Dalchau of the Institute of Child Health, University of London, London, England, for the gift of F15–42–01 anti-human Thy-1 monoclonal antibody. The MEM-12 anti-HLA-DR monoclonal antibody was kindly supplied by Dr. Ivan Hilgert of the Academy of Sciences, Prague, Czech Republic. Participation of Eva Bukovska in prompt and appropriate collection of placental samples is highly appreciated.

Department of Obstetrics and Gynecology, The University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, TN 37920.


PROBLEM: The classification of placental villi was reviewed, and regeneration of villous trees in mature human placentae was examined.

METHOD OF STUDY: Expression of Thy-1 by placental fibroblasts and pericytes, and markers of endothelial cells and monocyte-derived cells were studied by immuno-histochemistry and image analysis.

RESULTS: Villous regeneration consists of: (i) dedifferentiation of mature ramuli into young stem villi producing mesenchymal villi; (ii) differentiation of mesenchymal villi into immature intermediate villi; and (iii) differentiation of immature intermediate villi into transitory intermediate villi, branching into the precursors of mature intermediate and terminal villi. These processes are associated with dedifferentiation and redifferentiation of placental monocyte-derived cells. Significant changes of Thy-1 expression by fibroblasts and pericytes accompany aging and degeneration, as well as regeneration of placental villi.

CONCLUSIONS: Villous aging and degeneration in normal mature human placenta is compensated by regeneration of villous trees. Lack of villous regeneration may cause chronic fetal distress, due to the increasing demands of the growing fetus on the remaining terminal villi.