Regenerative Potential of Mesenchymal Stem Cells for Enhancing Uterine Health and Fertility in Repeat Breeder Dairy Cows

The suboptimal reproductive performance of repeat‐breeding (RB) cows is a major challenge for the dairy industry, leading to higher costs, prolonged calving intervals, and reduced productivity, negatively impacting herd productivity and economic viability. Among the associated factors, endometrial degeneration stands out, characterized by the replacement of functional tissue with fibrotic tissue, compromising uterine receptivity. In this context, regenerative therapy using mesenchymal stem cells (MSCs) has emerged as a promising alternative. This study evaluated the effects of intrauterine MSC inoculation in RB cows diagnosed with endometrial degeneration. Nine crossbred cows (Gyr × Holstein) were included and underwent clinical, cytological, microbiological, histopathological, ultrasonographic, and molecular evaluations on day 0 (pre‐treatment) and day 30 (post‐treatment). The results demonstrated endometrial remodeling, with fibrotic tissue replaced by loose connective tissue, increased vascularization, and the presence of new groups of endometrial glands. Doppler ultrasonography revealed enhanced blood flow of the endometrial mucosa and thickening of the uterine wall after therapy. qRT‐PCR analysis indicated reduced expression of pro‐inflammatory cytokines (IL‐1 β and IL‐8), suggesting modulation of the uterine environment. Despite the observed tissue improvement and absence of adverse effects on ovarian function, none of the inseminated cows conceived. In conclusion, MSC therapy promoted favorable changes in the endometrium and uterine environment, although it did not result in pregnancy, highlighting the need for further studies to optimize dosage, administration route, and therapeutic response time.