Unconjugated
Extracellular ATP and its hydrolysis product, adenosine, acting through specific receptors collectively named purinergic receptors, regulate female fertility by influencing the endometrial fluid microenvironment. There are four major groups of ecto-nucleotidases that control the levels of extracellular ATP and adenosine and thus their availability at purinergic receptors: ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases), ecto-nucleotide pyrophosphatase/phospho-diesterases (E-NPPs), ecto-5'-nucleotidase (5'NT), and alkaline phosphatases (APs). The aim of the present work is to characterize the expression and distribution of ecto-nucleotidases in human endometrium along the menstrual cycle and after menopause, to evaluate their potential utility as fertility markers. We examined proliferative, secretory and atrophic endometria from women without endometrial pathology undergoing hysterectomy. We show that the ecto-nucleotidases are mainly present at endometrial epithelia, both luminal and glandular, and that their expression fluctuates along the cycle and also changes after menopause. An important result was identifying NPP3 as a new biological marker of tubal metaplasia. Our results emphasize the relevance of the study of purinergic signaling in human fertility.
