Apoptotic Mechanisms in Seasonal Testicular Dynamics

Seasonal breeders exhibit profound testicular remodelling across the year, alternating between active spermatogenesis and regression. Central to this cyclical change is apoptosis, the programmed cell death that selectively eliminates germ cells and modifies the seminiferous epithelium. In the non-breeding season, reduced gonadotrophin stimulation and declining testosterone levels trigger apoptotic pathways in spermatogonia, spermatocytes and, in some species, Sertoli cells. This controlled cell loss leads to testis involution, conserving energy during unfavourable periods. Conversely, recrudescence in the breeding season involves downregulation of apoptotic signals and re-activation of proliferation, often coordinated with autophagy and cellular de-differentiation to repopulate the seminiferous tubules. Environmental cues—principally photoperiod and nutritional status—act via the hypothalamic–pituitary–gonadal axis to modulate the balance between survival and death signals, notably the BCL2 family and caspase cascades. The interplay between apoptosis and other mechanisms, such as germ-cell desquamation or autophagy-mediated cell survival, underpins species-specific patterns of testicular regression and recrudescence, ensuring reproductive success in changing environments.

Research from Nature Portfolio

Studies in plateau pikas have revealed a striking de-differentiation phenomenon in regressed testes. During the non-breeding season, adult spermatogonia and Sertoli cells adopt a juvenile-like state, expressing markers typically restricted to early development such as AP-2γ and anti-Müllerian hormone. Concurrently, autophagy-related proteins LC3 and BECN1 accumulate in the seminiferous tubules, suggesting that autophagy supports cell survival when nutrient availability is low. The loss of autophagic activity in fully regressed testes coincides with massive germ-cell depletion, implicating a tightly regulated switch between autophagy and apoptosis in seasonal testis dynamics. These findings highlight cellular plasticity as a key feature of testicular involution and regeneration in a photoperiodic mammal.

Apoptotic Mechanisms in Seasonal Testicular Dynamics publication trend

The graph below shows the total number of articles in apoptotic mechanisms in seasonal testicular dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Apoptosis: Programmed cell death involving caspases, essential for removal of superfluous or damaged germ cells during testis regression.

Autophagy: A lysosome-mediated degradation process that can promote cell survival under stress and delay apoptosis in the seminiferous epithelium.

Sertoli cell: Somatic cell in the seminiferous tubule that supports germ-cell development and regulates apoptotic signalling.

Seminiferous epithelium: The germinal lining of the testis where spermatogenesis occurs, subject to seasonal involution and regeneration.

Photoperiod: Environmental light–dark cycle that synchronises reproductive activity by modulating hormonal signals.

Spermatogonia: Mitotically active germ cells at the basal compartment of the seminiferous tubule, sensitive to apoptosis during regression.

De-differentiation: Process whereby differentiated cells revert to a more juvenile state, contributing to testicular recrudescence.

References

1. Cellular Modifications in Spermatogenesis during Seasonal Testicular Regression: An Update Review in Mammals. Animals (2022).
2. The balance between apoptosis and autophagy regulates testis regression and recrudescence in the seasonal-breeding South American plains vizcacha, Lagostomus maximus. PLOS ONE (2018).
3. Changes in the morphology and protein expression of germ cells and Sertoli cells in plateau pikas testes during non-breeding season. Scientific Reports (2016).
4. Proliferation and Apoptosis of Cat (Felis catus) Male Germ Cells during Breeding and Non-Breeding Seasons. Veterinary Sciences (2022).