Temporal and site-specific expression of transforming growth factor-beta4 in human endometrium

We recently identified a novel member of the transforming growth factor (TGF)-beta superfamily and showed that this gene, designated as endometrial bleeding associated factor (ebaf), or TGFbeta4, has a unique expression pattern in human endometrium. By Northern blot analysis, we showed that this gene was expressed in human endometrium during the late secretory and menstrual phases and was absent in proliferative, early and mid-secretory endometria. In this report, we show by in-situ hybridization that the mRNA of the TGF-beta4 is not expressed in the proliferative endometria. On the other hand, focal expression of the TGFbeta4 mRNA first appears in some endometrial glands in the mid-secretory phase. The TGFbeta4 mRNA is strongly expressed in the endometrial stroma during the late secretory and menstrual phases of the cycle. We raised a polyclonal rabbit antiserum against a peptide at the C terminal of the protein. Western blot analysis using affinity purified antiserum shows that the TGFbeta4 precursor detected in the endometrium as well as placenta is 41 kDa. Bands in the range of 45-51 kDa are also present in human endometrium, more predominantly during the late secretory phase. Immunohistochemical staining shows a low level of immunoreactivity for TGFbeta4 in the early, mid- and late proliferative and early and mid-secretory endometria. A strong immunoreactivity for TGFbeta4 is present in the stroma and to lesser extent in the endometrial glands in late secretory and menstrual endometria. The specificity of staining was shown by neutralizing the activity of the antibody with the synthetic peptide used for raising the antibody and by omitting the antibody. The findings show that TGFbeta4, both at the mRNA and protein levels, exhibits temporal and site specific expression in human endometrium.