Adenosine promotes trophoblast proliferation without inducing differentiation or apoptosis

Abstract

Objective: Adenosine and other nucleosides are essential regulators of cellular processes, but their specific roles in trophoblast growth and regulation remain incompletely defined. This study investigated the effects of purine and pyrimidine nucleosides on trophoblast proliferation, and further examined whether adenosine influences apoptosis, differentiation, or the expression of its receptors, transporters, and metabolizing enzymes. Methods: Nucleoside-induced proliferation was assessed by measuring metabolic activity, DNA synthesis, total DNA content, and MKI-67 expression in BeWo and JEG-3 cell lines, and by PCNA protein levels in placental explants. Adenosine was further evaluated for its effects on apoptosis, cytotrophoblast differentiation, and gene expression. Apoptosis was assessed via caspase-3 and -8 activity, differentiation by human chorionic gonadotropin (hCG) secretion and ERVW-1 expression, and gene regulation by qPCR analysis of adenosine receptors, nucleoside transporters, and metabolizing enzymes. Results: All nucleosides promoted proliferation in BeWo and JEG-3 cells, as indicated by increased metabolic activity, DNA synthesis, and total DNA content. For adenosine, MKI-67 expression analysis further confirmed its pro-proliferative effect. In placental explants, only adenosine significantly increased PCNA levels. Furthermore, adenosine did not affect caspase activity, hCG secretion, ERVW-1 expression, or the gene and protein expression of adenosine receptors, transporters, and metabolizing enzymes. Conclusions: Nucleosides, particularly adenosine, promote trophoblast proliferation. Adenosine has no additional effects on differentiation, apoptosis, or transcriptional changes in genes regulating its signaling or metabolism. Given adenosine's diverse biological roles beyond proliferation, further research is warranted to explore its broader impact on placental function and adaptation, especially under pathological conditions.