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Major differences between the testis and epididymis in the induction of granulomas in response to extravasated germ
1Department of Anatomy, Kagawa Medical University, Japan.
Abstract:
A spermatic granuloma is a chronic inflammatory lesion which surrounds extravasated spermatozoa. Clinically, the lesion develops in the interstitial spaces of the epididymis and vas deferens, and only exceptionally in the testis itself. In the present study, murine testes and epididymides were injured using a needle and the histological appearances of these organs was then compared. Traumatic injury induced extravasation of germ cells in both testes and epididymides. A few days later, spermatic granulomas consistently formed in the epididymides, however, such lesions were not induced in the testes. To examine the possibility that epididymal spermatozoa have inherently greater ability to form spermatic granulomas than do testicular germ cells, isolated epididymal spermatozoa or testicular germ cells were locally injected into the testes and epididymides of recipient mice. Spermatic granulomas readily formed in the epididymides after local injection of either epididymal spermatozoa or testicular germ cells. In contrast, such lesions did not form in the testes even when epididymal spermatozoa were injected. Therefore, this study suggests that the microenvironment of the testicular interstitium, rather than the extravasated components from the ruptured seminiferous tubules, is the main factor determining the limited formation of spermatic granulomas in the testis.
Insights
Spermatic granulomas, inflammatory lesions around sperm, consistently form in the epididymis but not the testis. This difference is due to the testicular microenvironment, not the sperm themselves.
Area of Science:
- Reproductive biology
- Immunology
- Histopathology
Background:
- Spermatic granulomas are inflammatory lesions surrounding extravasated spermatozoa.
- They typically develop in the epididymis and vas deferens, rarely in the testis.
Purpose of the Study:
- To investigate the reasons for the differential formation of spermatic granulomas in the epididymis versus the testis.
- To determine if the origin of extravasated germ cells or the local microenvironment influences granuloma formation.
Main Methods:
- Murine testes and epididymides were subjected to needle injury to induce germ cell extravasation.
- Histological analysis was performed to compare lesion development.
- Isolated epididymal spermatozoa and testicular germ cells were injected into recipient mice to assess granuloma formation capacity.
Main Results:
- Traumatic injury led to germ cell extravasation in both testes and epididymides.
- Spermatic granulomas consistently formed in the epididymis post-injury, but not in the testis.
- Injected epididymal spermatozoa or testicular germ cells readily formed granulomas in the epididymis, but not in the testis.
Conclusions:
- The testicular microenvironment is the primary factor limiting spermatic granuloma formation in the testis.
- Extravasated germ cells from ruptured seminiferous tubules do not inherently cause granulomas in the testicular interstitium.