乳腺重构的过程及其调节因素

受到妊娠周期的影响,乳腺组织在雌性哺乳动物一生中经历着妊娠-哺乳-退化的周期性发育变化. 在乳腺退化到再次泌乳的过程中,乳腺细胞经历凋亡和更新,从而实现乳腺组织的自我更新和修复,即乳腺重构. 重构期间乳腺在组织结构和生理过程中发生显著变化,但该过程物种间差异较大. 乳用家畜为维持泌乳,妊娠期和干奶期重叠,展示出独特的再生性乳腺重构. 再生性乳腺重构对乳畜乳腺健康和下一周期的泌乳具有重要意义,研究此过程将为后续调控乳腺自我更新和改善乳腺健康提供思路. 本综述总结了近年来动物乳腺重构的研究进展,系统归纳了影响乳腺重构的因素,包括激素、蛋白酶、细胞因子、热应激、氧化应激、光照周期等,旨在解析乳腺重构的生理机制,为精准调控该过程提供科学依据.

Recent Advance in Mammary Gland Remodeling and Its Regulatory Factors

Affected by the pregnancy cycle, the mammary gland undergoes cyclical developmental changes of pregnancy-lactation-involution in the life of female mammals. In the transition of mammary gland from involution to lactation, the mammary gland cells undergo apoptosis and renewal to reach the self-renewal and self-repair of mammary gland, which is defined as mammary gland remodeling. The mammary gland undergoes significant changes in morphology during mammary gland remodeling, and this process varies across species. In rodents, the involution is divided into two phases based on the reversal of phase. The first phase (first 48 h after weaning) is characterized by milk stasis and lysosomal content release into the cytosol and extensive cell death. The second irreversible phase (after 48 h of weaning) facilitates the remodeling of mammary gland. Compared with rodents, the remodeling process of the mammary glands in dairy livestock exhibits a regenerative involution to maintain subsequent lactation. During the regenerative involution, the regress of mammary gland cells is not significant and the mammary alveolar structure remains basically intact. Alveolar structure is heterogeneous and only shows a few alveolar collapses, and the number of apoptotic bodies only slightly increases. The regenerative remodeling of mammary gland is of great significance to the mammary health and maintenance of the next cycle of lactation in dairy livestock. If the dry period of dairy cows is shortened, the milk production in the next cycle will be significantly reduced. The hormones level, proteases, cytokines and oxidative stress have influences on the remodeling of mammary gland through the various cellular signal pathways. Beyond the internal factors, dietary nutrition and various environmental factors, including heat stress and photoperiod, play important roles in regulating the process of remodeling of mammary gland. The current review summarizes the studies on mammary gland remodeling in recent years, and highlights the factors (including hormones, proteases, cytokines, etc.) regulating the regenerative involution in the mammary gland of dairy livestock. This review tries to uncover the internal mechanism of mammary gland remodeling and provides scientific basis to regulate it.