Brain-derived neurotrophic factor and neurotrophic tyrosine receptor kinase-2 in stallion testes: insights into seasonal changes and potential roles in spermatogenesis.
Abstract: Brain-derived neurotrophic factor (BDNF) and its receptor neurotrophic tyrosine receptor kinase-2 (NTRK2) have known important roles in the central nervous system for neurite growth, survival, and differentiation. Nevertheless, the significance of BDNF in spermatogenesis remains unclear in stallions. Therefore, the present study was designed 1) to investigate the expression of BDNF and its receptor NTRK2 and 2) the seasonal variation in the expression patterns of BDNF and NTRK2 in stallions' testes. We used testes from eight postpubertal Thoroughbred stallions collected after a field castration during two different seasons of the year (breeding season [BS] and nonbreeding season [NBS]). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Western blotting (WB), and immunofluorescence were performed. RT-qPCR results showed upregulation of mRNA levels of BDNF and NTRK2 in the testes collected during the NBS. The quantification of the protein bands obtained after WB displayed significantly higher relative intensity in NBS. The immunofluorescence assay identified the localization of BDNF in the cytoplasm of Sertoli and Leydig cells in BS. The cytoplasm of germs cells and Leydig cells were stained with BDNF in NBS. NTRK2 was observed in the cytoplasm of Leydig cells of BS and NBS. Moreover, different stages of germ cells including undifferentiated spermatogonia and spermatocytes were immune labeled with NTRK2 in the NBS. These findings provided the first evidence of the localization of BDNF and NTRK2 in the testicular cells of stallions, suggesting the potential role of BDNF signaling in testes development and spermatogenesis. Further investigation is necessary to explore the functional implications of BDNF signaling on spermatogenesis, focusing on the regulatory mechanisms that govern the seasonal expression patterns observed. This will help confirm the paracrine/autocrine importance of this neurotrophin in the stallions testes.
© Copyright 2025 Korean Society of Animal Science and Technology.
Publication Date: 2025-07-31 PubMed ID: 40874009PubMed Central: PMC12380027DOI: 10.5187/jast.2024.e52Google Scholar: Lookup
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Summary
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Overview
- This study examined the presence and seasonal variations of brain-derived neurotrophic factor (BDNF) and its receptor NTRK2 in stallion testes.
- Researchers explored how these proteins might contribute to spermatogenesis by comparing expression during breeding and nonbreeding seasons.
Background
- BDNF is well-known for its roles in the nervous system, including promoting neurite growth, cell survival, and differentiation.
- NTRK2 is the receptor that mediates BDNF’s effects.
- Their functions in the testes, particularly in regulating spermatogenesis in stallions, have not been clearly understood before.
- Spermatogenesis is a seasonal process in many animals, including stallions, with physiological changes occurring between breeding and nonbreeding seasons.
Study Objectives
- To investigate the expression patterns of BDNF and NTRK2 in stallion testes.
- To explore how these expression levels might change between the breeding season (BS) and nonbreeding season (NBS).
Methodology
- Testes samples were collected from eight postpubertal Thoroughbred stallions via field castration during both breeding and nonbreeding seasons.
- Analytical techniques used included:
- RT-qPCR to measure mRNA levels of BDNF and NTRK2 for gene expression analysis.
- Western blotting (WB) to detect and quantify the protein levels.
- Immunofluorescence to localize the proteins within various testicular cells.
Key Findings
- Gene expression analysis (RT-qPCR) showed increased mRNA levels of both BDNF and NTRK2 during the nonbreeding season compared to the breeding season.
- Western blot protein quantification supported these findings, showing higher relative protein intensities in the nonbreeding season samples.
- Immunofluorescence localization revealed:
- BDNF was found in the cytoplasm of Sertoli and Leydig cells during the breeding season.
- During the nonbreeding season, BDNF was present not only in Leydig cells but also in the cytoplasm of germ cells.
- NTRK2 localization was primarily in Leydig cells for both seasons.
- During the nonbreeding season, NTRK2 was additionally detected in several germ cell stages, including undifferentiated spermatogonia and spermatocytes.
Interpretation and Implications
- The study provides the first direct evidence of BDNF and NTRK2 presence in specific testicular cells of stallions.
- The seasonal variation in their expression suggests that BDNF signaling might play a regulatory role in testicular development and the spermatogenic process.
- The differential localization patterns, especially the presence in germ cells during the nonbreeding season, point to potentially important autocrine or paracrine roles of BDNF signaling in spermatogenesis.
- Higher expression during the nonbreeding season might indicate preparation or regulation mechanisms for spermatogenesis cycles aligned with reproductive seasonality.
Future Directions
- Further functional studies are required to clarify how BDNF and NTRK2 influence spermatogenesis at molecular and cellular levels.
- Investigating regulatory pathways controlling seasonal expression could illuminate hormone or environmental cues affecting testes physiology.
- Understanding precise paracrine/autocrine interactions will be key to determining therapeutic or reproductive management applications in stallions.
Cite This Article
APA
Shakeel M, Yoon M.
(2025).
Brain-derived neurotrophic factor and neurotrophic tyrosine receptor kinase-2 in stallion testes: insights into seasonal changes and potential roles in spermatogenesis.
J Anim Sci Technol, 67(4), 909-921.
https://doi.org/10.5187/jast.2024.e52 Publication
Researcher Affiliations
- Department of Animal Science and Biotechnology, Kyungpook National University, Sangju 37224, Korea.
- Department of Clinical Studies, Faculty of Veterinary and Animal Sciences, Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi 44000, Pakistan.
- Department of Animal Science and Biotechnology, Kyungpook National University, Sangju 37224, Korea.
- Department of Horse, Companion and Wild Animal Science, Kyungpook National University, Sangju 37224, Korea.
- Research Institute for Innovative Animal Science, Kyungpook National University, Sangju 37224, Korea.
Conflict of Interest Statement
No potential conflict of interest relevant to this article was reported.
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