Immunohistochemical labeling of the inhibin/activin betaC subunit in normal human placental tissue and chorionic carcinoma cell lines

Abstract

Inhibins and activins are important regulators of the female reproductive system. A novel inhibin subunit, named betaC, has been identified and demonstrated to be expressed in several human tissues. We demonstrate here that inhibin betaC is expressed in human placenta. Expression of the inhibin betaC subunit was demonstrated at the protein level by means of immunohistochemical evaluation and at the transcriptional level by an inhibin betaC-specific RT-PCR analysis. Expression of inhibin betaC was detected in the human chorionic carcinoma cell lines JEG and BeWo. Although the precise role of this novel inhibin subunit in human placenta development and homeostasis is unclear, analogies with other inhibin subunits and the strong expression of betaC in normal human trophoblast cells and chorionic carcinoma cells suggest that betaC may be involved in autocrine/paracrine signaling pathways, angiogenesis, decidualization, and tissue remodeling under normal and malignant conditions. Additionally, JEG and BeWo express betaC and, therefore, can be used as a cell culture model for further functional analysis of this subunit in the human placenta.

Figure 1

Immunohistochemical staining reaction of inhibin βC in normal human liver tissue. Normal human liver tissue was used as a positive control for inhibin βC immunolabeling. Negative controls were performed by replacing the primary antibody with normal goat IgG as an isotype control. (A) No staining was detected in the negative control. (B) The inhibin βC subunit was detected in hepatocytes of normal human liver tissue, but not in erythrocytes.

Figure 2

Immunohistochemical staining reaction of inhibin βC in normal human placenta tissue. No staining was detected in the negative controls for trophoblast cells (A) or syncytiotrophoblast cells (B). (C) Invasive trophoblast cells were strongly stained for inhibin βC. (D) Additionally, syncytiotrophoblast cells also showed cytoplasmic staining for the novel inhibin βC subunit.

Figure 3

Localization of inhibin βC in BeWo and JEG. The carcinoma cell lines were analyzed by immunofluorescence for expression of inhibin βC. Positive cytoplasmic staining was detected in BeWo (A) and JEG (B) cells.

Figure 4

Inhibin βC expression in normal placental tissue and chorionic carcinoma cell lines. Normal placental tissue and BeWo and JEG cells were analyzed by RT-PCR for the expression of the inhibin βC subunit. PCR products from inhibin βC mRNA were detected in each sample. Interestingly, the inhibin βC mRNA level was less intense in JEG cells compared with BeWo cells and placental tissue. Furthermore, the water control to demonstrate any PCR contamination was negative.