Abstract
Simple SummaryBody temperature has detrimental effects on sperm quality in mammalian species, including pigs. However, the molecular mechanism of this is not yet well understood. Cryptorchidism is when one or both testes fail to descend into the scrotum, which leads the testes to be exposed to the body temperature. The aims of present study were to investigate the effect of body temperature on the histomorphometry, apoptosis and the expression of the proliferation-associated protein PCNA and the autophagy-associated protein LC3 in spontaneous unilateral cryptorchid boar testes. Our findings showed that cryptorchidism had no evident influence on the number of Sertoli cells in boars. In cryptorchid testes, spermatogonia markedly decreased and the seminiferous tubule contained only a few spermatogonia, but did not contain post-meiotic germ cells. The altered seminiferous epithelium of the cryptorchid testis showed a low proliferation of its spermatogonia, with apoptosis and autophagy like that of scrotal testis, which probably entailed a gradual degeneration of the epithelium and the impossibility of its recovery. Although the number of Sertoli cells did not change, it was likely that their functionality was altered and that this affected the proliferation capacity of spermatogonia, causing the arrest of spermatogenesis.Spontaneous unilateral cryptorchid boars have one testis in the abdomen or inguinal canal, causing its temperature to be at or near the body temperature, which impairs spermatogenesis, although the histomorphometry and molecular mechanisms underlying this process remain unclear. The aim of the present study was to determine the histomorphometry, proliferation, apoptosis, and autophagy alterations in spermatogonia and Sertoli cells in unilateral cryptorchid, scrotal (contrascrotal), and preweaning piglet (preweaning) testes. Histomorphometrical analysis of cryptorchid testes showed that the seminiferous tubules contained only Sertoli cells and a few spermatogonia, but did not contain post-meiotic germ cells. The number of spermatogonia markedly decreased, and the number of Sertoli cells did not change remarkably in cryptorchid testes. TUNEL assay results showed that apoptosis signals were predominantly observed in spermatogonia. In cryptorchid and contrascrotal testes, proliferating cell nuclear antigen (PCNA) and LC3 were located in spermatogonia. The number of PCNA-positive, TUNEL-positive, and LC3-positive germ cells was low, and the protein and mRNA levels of PCNA and LC3 were significantly decreased in cryptorchid testes. Taken together, the number of Sertoli cells did not change remarkably, whereas the number of germ cells decreased in the cryptorchid testes, compared with that in the contrascrotal testes. Insufficient proliferation, excessive apoptosis, and autophagy were involved in the regulation of the decrease in spermatogonia in cryptorchid boar testes.
Highlights
The establishment and maintenance of germ cells are critical for ensuring the survival of a species [1]
We previously found that the spermatogenic epithelium of unilateral cryptorchid boar testes was severely degenerated and comprised only Sertoli cells and several spermatogonia [24]
Contrascrotal boar testes showed normal histology, multiple typestypes of germ cells, cells, including spermatogonia, spermatocytes, roundround spermatids, and multiple of germ including spermatogonia, spermatocytes, sperand elongated spermatids, and Sertoli cells werecells observed the spermatogenic epithelium matids, and elongated spermatids, and Sertoli werein observed in the spermatogenic (Figure 1D).(Figure 1D)
Summary
The establishment and maintenance of germ cells are critical for ensuring the survival of a species [1]. The seminiferous tubules were found to be markedly degenerated and contained spermatogonia and Sertoli cells almost exclusively [8]. In spontaneous and surgicallyinduced unilateral cryptorchidism in humans [9,10], rats [11], monkeys [12], rabbits [8], and rams [13], the number of germ cells was markedly decreased, whereas the number of Sertoli cells remained constant, with a slight morphological change [14]. In vivo detection of proliferating cell nuclear antigen (PCNA) or Ki-67 (a marker for mitosis) showed that the proliferative activity of germ cells decreased in unilateral cryptorchid rabbits [8], dogs [16], and boars [17]. As an alternative death pathway to apoptosis [20], autophagy is involved in the regulation of the degeneration of the seminiferous epithelium in cryptorchidism in rats [21], mice [22], and humans [23]
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