Role of autophagy in porcine spermatogonia

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Spermatogonial stem cells (SSCs) sustain spermatogenesis through tightly controlled self renewal and differentiation processes. A long-term culture for porcine spermatogonia has not been established yet. To thrive in culture conditions, a cell requires to adapt to the environment. One of the tools that cells have developed to manage stress is autophagy. Autophagy is induced by cellular stress, which results in lysosomal degradation and recycling of the degradation product to generate energy for cellular homeostasis. Therefore, the main objective of this thesis is to elucidate the role autophagy plays in porcine germ cells. Initially, we identified that autophagy is active at basal levels in situ; upon isolation from the testis, the levels of autophagy increase significantly. Autophagic levels were then analyzed in testis tissue formed de novo. After 6 weeks, autophagic levels were at basal levels, which indicated that re-introduction to the microenvironment decreases germ cell stress. Considering that in vitro conditions upregulate autophagy, germ cells were cultured in two different media, and found that levels of autophagy are lower in nutrient rich medium. Levels of reactive oxygen species (ROS) were measured and were found to decrease germ cell viability; upon autophagy stimulation, viability increased. Conversely, upon autophagic inhibition, ROS increased, and germ cell viability decreased. These results suggested that autophagy is a cytoprotective mechanism for germ cells and can be used as an indicator for stress in vitro. To investigate the role of autophagy in germ cells in the presence of toxicants, we evaluated the levels of autophagy in primate testis tissue xenografted to mice exposed to phthalates. It was found that germ cells exposed to this toxicant had higher levels of autophagy than the controls. To evaluate the effects of toxicants in vitro, germ cells were treated with another phthalate, which caused germ cell viability to decrease. Upon autophagy induction, germ cell viability increased accordingly. These results show that autophagy is a cell protective mechanism for germ cells exposed to a toxicant. Overall, the work in this thesis identifies autophagy as an essential process for germ cell homeostasis.
spermatogonial stem cells, autophagy, phthalates, germ cells, Testis
Valenzuela-Leon, P. (2018). Role of autophagy in porcine spermatogonia (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from doi:10.11575/PRISM/32798