Caspase signalling pathways in human spermatogenesis

Abstract

Purpose: Little is known about the apoptotic mechanisms involved in abnormal spermatogenesis. In order to describe the significance of apoptosis in azoospermia, testicular tissue from abnormal spermatogenesis was analysed.

Methods: Testicular treatment biopsies were obtained from 27 men. Five presented oligozoospermia, 9 obstructive azoospermia (4 congenital bilateral absence of the vas deferens; 5 secondary azoospermia) and 13 non-obstructive azoospermia (5 hypospermatogenis; 3 maturation arrest; 5 Sertoli-cell-only syndrome). Immunohistochemical staining was performed for active caspases-3, -8 and -9. The presence of active caspases in Sertoli cells and germ cells was analyzed using stereological tools.

Results: Increased active caspase-3 was found in Sertoli-cell-only syndrome. No significant differences were found in maturation arrest. In hypospermatogenesis, primary spermatocytes were the germ cells with higher active caspases. Oligozoospermia and secondary obstruction showed significant differences among germ cells for the presence of all active caspases. In oligozoospermia, spermatogonia presented significant increased active caspase-9 in relation to active caspase-8. In primary obstruction and hypospermatogenesis, germ cells presented significant increased active caspases-3 and -9.

Conclusions: Results suggest that increased active caspase-3 might be involved in Sertoli-cell-only syndrome etiology. In cases of hypospermatogenesis, intrinsic lesions at the meiotic stage seem to be related to the pathology. In secondary obstruction apoptosis is suggested to be initiated due to extrinsic and intrinsic lesions, whereas in primary obstruction only the intrinsic apoptotic pathway seems to be present. Finally, in oligozoospermic patients spermatogonia death by mitochondrial damage additionally to meiosis malfunctioning, might be on the origin of the decreased sperm output.

Fig. 1

Grill systems used for the stereological analysis performed. a Howard and Reed multi-scale system placed over a seminiferous tubule image on the computer (100×) in order to estimate the relative volume (Vv) occupied per cell per seminiferous tubule; b Grill inserted in the left microscope ocular (10×) in order to estimate the volume (V) occupied per cell in the testis (Integrationsplatte II, 100/25, Carl Zeiss)

Fig. 2

Active caspases-8, −9 and −3 immunohistochemical analysis for the testicular groups analyzed. OZ—Oligozoospermia; CBAVD—congenital bilateral absence of the vas deferens; sOAZ—secondary obstructive azoospermia; HP—hypospermatogenesis; MA—maturation arrest; SCOS—Sertoli-cell-only syndrome. SC—Sertoli-cell; SG—spermatogonia; ST1—primary spermatocyte; ST2—secondary spermatocte; Sa—round spermatid; Bar = 50 μm

Fig. 3

Median values for relative volume (Vv) and volume (V) occupied by Sertoli cells and germ cells with active caspases-8, −9 and −3, in the seminiferous tubules and testis, respectively. OZ—Oligozoospermia; CBAVD—congenital bilateral absence of the vas deferens; sOAZ—secondary obstructive azoospermia; HP—hypospermatogenesis; MA—maturation arrest; SCOS—Sertoli-cell-only syndrome