Volume 52 (7): 885-892, 2004 Copyright ©The Histochemical Society, Inc. The Serine Protease HtrA1 Is Upregulated in the Human Placenta During Pregnancy
Department of Medicine and Public Health, Section of Clinical Anatomy, Second University of Naples, Naples, Italy (ADL,AM,DG); Department of Evolutive and Comparative Biology, University of Naples "Federico II," Naples, Italy (MDF,VF,VL); Department of Obstetrics and Gynecology, Second University of Naples, Naples, Italy (LC); Laboratory "C," Department for the Development of Therapeutic Programs, Center for Experimental Research, Regina Elena Institute, Rome, Italy (ILT,MC,MCP); and Department of Biochemistry and Biophysics "F. Cedrangolo," Section of Pathologic Anatomy, Second University of Naples, Naples, Italy (AB) Correspondence to: Dr. Alfonso Baldi and Dr. Marco G. Paggi, Center for Experimental Research, Regina Elena Cancer Institute, Via delle Messi d'Oro 156, 00158 Rome, Italy. E-mail: alfonsobaldi{at}tiscali.it The placenta has a dynamic and continuous capacity for self-renewal. The molecular mechanisms responsible for controlling trophoblast proliferation are still unclear. It is generally accepted that the simultaneous activity of proteins involved in cell proliferation, apoptosis, and extracellular matrix degradation plays an important role in correct placental development. We investigated in depth the expression of the serine protease HtrA1 during pregnancy in human placenta by in situ hybridization and immunohistochemistry, we demonstrated that HtrA1 displayed a low level of expression in the first trimester of gestation and a strong increase of HtrA1 expression in the third trimester. Finally, by electron microscopy, we demonstrated that HtrA1 was localized either in the cytoplasm of placental cells, especially close to microvilli that characterized the plasma membrane of syncytiotrophoblast cells, or in the extracytoplasmic space of the stroma of placental villi, particularly in the spaces between collagen fibers and on collagen fibers themselves. The expression pattern of HtrA1 in human placentas strongly suggests a role for this protein in placental development and function. Moreover, on the basis of its subcellular distribution it can be postulated that HtrA1 acts on different targets, such as intracellular growth factors or extracellular matrix proteins, to favor the correct formation/function of the placenta. (J Histochem Cytochem 52:885892, 2004)
Key Words: HtrA1 serine protease placenta in situ hybridization immunohistochemistry electron microscopy
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