Effects of insulin-like growth factor-1 on the proliferation and apoptosis of stallion testicular cells under normal and heat stress culture conditions.

The research investigates the impact of heat stress on the health of stallion testicular cells, and how insulin-like growth factor-1 can potentially enhance their viability and proliferation, and hinder apoptosis. This study can aid in understanding the base level of IGF-1 required for maintaining health of testicular cells during heat stress-induced degeneration.

Methods and Approach

• The investigators chose to use stallion testicular cells (TCs) for their research, assessing the effect of heat and insulin-like growth factor (IGF)-1 on these cells.
• The TCs were divided into control and treatment groups that were exposed to differing concentrations of recombinant human IGF-1 for 24 hours at either 34 degrees Celsius or 37 degrees Celsius.
• Quantitative PCR (RT-qPCR) was applied to measure the effects of IGF-1 on TC proliferation, viability, and apoptosis.
• The researchers used two proliferation markers, proliferating cell nuclear antigen (PCNA) and marker of proliferation Ki-67 (MKI-67), and the anti-apoptotic marker, Myeloid leukemia-1 (MCL-1), to gauge cell proliferation and survival. A pro-apoptotic marker, BCL2 antagonist/killer-1 (BAK-1), was used to measure cell death.
• They also used some gene tests to study progression of spermatogenesis: undifferentiated cell transcription factor 1 (UTF-1), protein gene product 9.5 (PGP9.5), and deleted in azoospermia-like (DAZL).

Results and Findings

• The study concluded that TCs treated with 1 ng/mL of IGF-1 at 34 degrees Celsius had the highest survival rate.
• A significant increase in the relative abundance of PCNA, MKI-67, and MCL-1 mRNA transcript was registered in the treated TCs when compared to the control group. On the other hand, BAK-1 was significantly downregulated in the treated group, indicating lower rate of apoptosis.
• TCs that were treated with 1 ng/mL IGF-1 showed the most substantial relative abundance of UTF-1 and DAZL. This indicates that IGF-1 treatment could aid in promoting spermatogenesis.
• Testicular cells exposed to 0.1 ng/mL IGF-1 exhibited the most pronounced PGP9.5 level, signifying the presence of spermatogonia and primary spermatocytes within these cells.
• The results confirmed that heat stress in stallions decreases the survival of their testicular cells.

Implications

• The data gathered from this research can be helpful in identifying the necessary base level of IGF-1 that would enhance proliferation and reduce apoptosis in TCs during heat stress-induced testicular degeneration in stallions.
• These findings may pave the way for treatments or interventions that can mitigate the adverse effects of heat stress on stallion fertility.