Effect of testicular degeneration on expression of sperm protein at 22 kDa in stallions

Lynda M.J. Miller, Elizabeth M. Woodward, Juliana R. Campos, Edward L. Squires, Mats H.T. Troedsson

Research output: Contribution to journalArticlepeer-review


Background: Sperm protein at 22 kDa has been associated with fertility. Objectives: The objectives of this study were to determine (1) the localization pattern of SP22 on ejaculated and caudal epididymal equine spermatozoa and in epididymal fluid, and to (2) characterize SP22 protein and mRNA expression in testicular and epididymal tissues in response to heat-induced testicular degeneration. Materials and methods: Semen was collected before and after hemi-castration, as well as prior to and following insulation of the remaining testes, and tissue specimens were collected for analysis. Results: Histopathology confirmed degeneration in insulated testes. Ejaculated and epididymal spermatozoa from samples collected prior to insulation of the testicles had a predominant staining pattern of SP22 over the equatorial region. However, the equatorial pattern in the pre-insulation epididymal semen samples was significantly lower than in the pre-insulation ejaculated semen samples (68 ± 3, 81 ± 2.6, respectively). Ejaculated and epididymal samples collected after insulation of the testicles showed a complete loss of staining as the predominant pattern. Western blot analysis verified the presence of SP22 on fresh ejaculated spermatozoa prior to and following heat-induced degeneration, on epididymal spermatozoa after testicular insulation, and in testicular and epididymal tissues. Heat insulation significantly reduced messenger RNA expression in the head of the epididymis and testicular tissues. Immunohistochemistry of the testicular and epididymal tissues pre-heating showed considerably weaker staining than the same tissues post-heating. Discussion and conclusion: It was concluded that heat-induced testicular damage causes both loss and relocation of SP22 on the sperm membrane. Future studies are warranted to determine the diagnostic value of these findings.

Original languageEnglish
Pages (from-to)211-221
Number of pages11
Issue number1
StatePublished - Jan 2024

Bibliographical note

Publisher Copyright:
© 2023 American Society of Andrology and European Academy of Andrology.


  • SP22
  • fertility
  • sperm protein at 22 kDa
  • stallion
  • stallion
  • testicular degeneration

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Reproductive Medicine
  • Endocrinology
  • Urology


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