EXPRESSION OF TRANSFORMING GROWTH-FACTOR-BETA (TGF-BETA) ISOFORMS ANDTGF-BETA TYPE-II RECEPTOR MESSENGER-RIBONUCLEIC-ACID AND PROTEIN, ANDTHE EFFECT OF TGF-BETA-S ON ENDOMETRIAL STROMAL CELL-GROWTH AND PROTEIN-DEGRADATION IN-VITRO

Reverse transcription-polymerase chain reaction analysis of total RNA and immunocytochemical observations revealed that human endometrial gl andular epithelial and stromal cells in primary culture express messen ger RNAs and proteins for transforming growth factor-beta 1 (TGF beta 1), TGF beta 2, and TGF beta 3 as well as TGF beta type II receptor. T he epithelial and stromal cells synthesize and secrete into their cult ure-conditioned medium 2.6 +/- 0.3 and 1.4 +/- 0.2 ng TGF beta 1/10(6) cells, respectively; after transient acidification of the medium, the TGF beta 1 levels were 18.1 +/- 0.4 and 7.8 +/- 0.7 ng/10(6) cells. T hese cells also contain specific binding sites for [I-125]TGF beta 1, indicated by light microscope autoradiography. TGF beta s at 0.01-10 n g/ml neither stimulated or inhibited subconfluent quiescent stromal ce lls under serum-free condition nor altered the mitogenic action of 10% fetal bovine serum. However, in the presence of 2% fetal bovine serum , which induced half-maximal stimulation of [H-3]thymidine incorporati on, TGF beta 1 and TGF beta 2 at 0.1-0.5 ng/ml and TGF beta 3 at 0.1-2 .5 ng/ml significantly stimulated the rate of [H-3]thymidine incorpora tion into quiescent stromal cells (P < 0.005); they were ineffective a t higher concentrations. TGF beta s did not have any effect on cell pr oliferation, as determined by cell counting; however, at 0.1 ng/ml and higher concentrations, TGF beta s significantly reduced the metabolic activity of stromal cells, as determined by colorimetric -(4,5-dimeth ylthiazol-2-yl)2,5-diphenyltetrazolium bromide assay (P < 0.05). The s timulatory and inhibitory actions of TGF beta s in both assays were re versible using 5-10 mu g/ml TGF beta 1- and TGF beta 2- and 3-6 mu g/m l TGF beta 3-specific neutralizing antibodies. TGF beta 1 at 1 ng/ml h ad no significant effect on long-lived protein degradation, assayed by incorporation of [C-14]valine into newly synthesized protein by strom al cells, and was similar to the effect of epidermal growth factor or platelet-derived growth factor-BB (10 ng/ml). The data suggest that th e TGF beta expression by various endometrial cell types in an autocrin e/paracrine manner acts as a negative regulator essential for restrain ing endometrial growth and transition from proliferation to differenti ation stages during the secretory phase after mitogenic stimulation du ring the proliferative phase of the menstrual cycle.