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PSVI-6 Effects of progesterone and matrix metalloproteinase inhibition on milk component synthesis in bovine mammary epithelial cells.

Year: 2025
Type: article
Abstract: Mammary gland development and milk production are regulated by multiple factors, including hormonal regulation, cell-cell, and cell-extracellular matrix (ECM) interactions. Progesterone (PG), a major ovarian hormone, promotes cell proliferation and alveolar structure formation during pregnancy. It also activates metalloproteinase (MMP)-2 and MMP-9 to facilitate ductal branching through ECM degradation. Prolactin (PRL), a key lactation hormone, is essential for inducing milk-secretory differentiation in mammary epithelial cells (MECs). Following parturition, PRL inhibits MMP-2 and MMP-9 (MMP-2/9) activity and enhances blood-milk barrier function in MECs to prevent the leakage of milk components. Milk synthesis has been known to exclusively occur in MECs differentiated by PRL. However, a recent study suggested that PG might also contribute to milk synthesis by enhancing the expression of E-74 like factor 5 (Elf5), a key regulator of lactogenic differentiation in MECs. This study aimed to investigate the effects of PG and MMP-2/9 inhibition on milk component synthesis in primary bovine mammary epithelial cells (BMECs). BMECs were cultured in control cell culture media (CM) consisting of DMEM/F12 supplemented with 10% fetal bovine serum and 1% penicillin/streptocmycin. For two-dimensional (2D) and three-dimensional (3D) cell cultures, BMECs were seeded onto standard and Matrigel-coated cell culture plates, respectively. After reaching approximately 80% confluency, 2D and 3D BMECs were differentiated for 5 days using PRL-differentiation media (PRLM) or PG-differentiation media (PGM). While PGM increased the protein expression of Elf5 in BMECs (P < 0.05), it failed to induce milk component synthesis and reduced claudin-3 expression (P < 0.05). Cell culture supernatant collected from PGM showed enhanced MMP-2/9 activity (P < 0.05), leading to the laminin degradation. However, supplementation of PGM with 400 ng/mL MMP-2/9 inhibitor significantly decreased MMP-2/9 activity (P < 0.05). Additionally, MMP-2/9 inhibition and PGM treatment upregulated milk component (α-casein, β-casein, β-lactoglobulin, α-lactalbumin, and milk fats) production in BMECs (P < 0.05), reaching levels similar to PRLM. Claudin-3 expression also increased in PGM/MMP-2/9 inhibitor-treated cells (PGM+MMPi) (P < 0.05). Collectively, there findings demonstrated that PGM supplemented with MMP-2/9 inhibitor induces milk component production in 3D BMECs, to levels similar to those observed in PRLM. The key distinction between PRL and PG lies on their differential regulation of MMP-2/9 activity during differentiation, indicating that MMP-2/9 inactivation is a pivotal process for facilitating milk production in 3D BMECs. This study provides novel insights into the hormonal regulation of lactation, contributing to a deeper understanding of milk production mechanisms.
DOI: 10.1093/jas/skaf300.487
Institution: Konkuk University
Language: English
Open Access status: bronze
OpenAlex ID: W4414830726
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