This study investigated the effect of heat stress on stallion testicular cells (TCs) and the effect of insulin-like growth factor (IGF)-1 on TC viability, proliferation, and apoptosis, including different stages of germ cells. TCs were divided into control or treatment groups with 0.01, 0.1, 1, 10, and 100 ng/mL of recombinant human IGF-1 (rhIGF-1) for 24 h at 34 °C and 37 °C. The population and viability were measured before and after treatment. The effects of rhIGF-1 on TC viability, proliferation, and apoptosis were determined using RT-qPCR. Proliferating cell nuclear antigen (PCNA) and marker of proliferation Ki-67 (MKI-67) were used as proliferation markers. Myeloid leukemia-1 (MCL-1) was used as an antiapoptotic marker. BCL2 antagonist/killer-1 (BAK-1) was used as a proapoptotic marker. The relative abundance of mRNA transcript of undifferentiated cell transcription factor 1 (UTF-1), protein gene product 9.5 (PGP9.5), and deleted in azoospermia-like (DAZL), was measured for spermatogenesis progression. TCs treated with 1 ng/mL rhIGF-1 at 34 °C exhibited the highest viability. Significant upregulation of the relative abundance of mRNA transcript of PCNA, MKI-67, and MCL-1 was observed in treated TCs compared with untreated TCs; however, BAK-1 was significantly downregulated in treated TCs. Germ cells treated with 1 ng/mL rhIGF-1 exhibited the highest relative abundance of mRNA transcript of UTF-1 and DAZL, whereas TCs exposed to 0.1 ng/mL showed the highest PGP9.5 level. These data confirm that heat stress in stallions decreases TC viability. These findings may help identify a basal IGF-1 level for TC proliferation and apoptosis during heat stress-induced testicular degeneration in stallions.
Keywords: Germ cell viability; Germ cells molecular markers; Spermatogenesis; Testicular degeneration.
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