Spermatogenesis and testicular tumours in ageing dogs

Abstract

Spermatogenesis was examined in testes from 74 dogs of various breeds without clinically detected testicular disease. A modified Johnsen score system was used to determine whether spermatogenesis deteriorates with ageing. The diameter of seminiferous tubules was measured in dogs without testicular disease to examine other possible effects of ageing on tubular performance. There appeared to be no relation between age and these variables. The influence of testicular tumours on spermatogenesis was also investigated in both affected and unaffected testes. The testes of 28 dogs with clinically palpable tumours and 21 dogs with clinically non-palpable tumours were investigated. In cases of unilateral occurrence of a tumour, impairment of spermatogenesis was observed only in the affected testis of dogs with clinically detected tumours. Bilateral occurrence of tumours, whether detected clinically or non-clinically, was associated with severe impairment of spermatogenesis. The prevalence of tumours increased during ageing. Eighty-six per cent of the clinically detected and 57% of the non-clinically detected tumours were found in old dogs. Multiple types of tumour and bilateral occurrence were very common. Seminomas and Leydig cell tumours were more frequent than Sertoli cell tumours. It was concluded that spermatogenesis per se did not decrease during ageing in dogs but the occurrence of testicular tumours increased with ageing and affected spermatogenesis significantly, as reflected by a lower Johnsen score.

Proliferative Activity In Vitro and DNA Repair Indicate that Adult Mouse and Human Sertoli Cells Are Not Terminally Differentiated, Quiescent Cells1

“…A balance seems to exist between cell cycle inhibitors and inducers that in the normal in vivo situation keeps the cells quiescent. The residual proliferation capacity of Sertoli cells in vivo is probably the underlying reason for Sertoli cell tumors seen rarely in humans [41] and more often in dogs [42]. Mitotically active Sertoli cells have been found in testis nodules of infertile humans [43].…”

Expression of Connexin 43 in normal canine testes and canine testicular tumors

“…This phenomenon is attributed to the secretion of excessive amounts of estrogen by the tumor cells (Nielsen and Kennedy 1990), leading to greater concentrations of estradiol in both testicular and peripheral venous blood (Peters et al 2000). It is known that gap junctions containing Cx43 in rodent myometrium can be altered by estrogen, through putative estrogen-responsive elements (Dahl and Berger 1978;Burghardt et al 1984;Yu et al 1994).…”

“…The dog has been proposed as a model for studies of the male reproductive system, for example, in the development of testicular tumors (Peters et al 2000). In adult dogs, 5-15% of all neoplasms are testicular tumors (Grootenhuis et al 1990) with Sertoli cell tumors, seminomas, and Leydig cell tumors occuring with an about equal frequency (Nielsen and Kennedy 1990).…”

Age‐related changes in interstitial fibrosis and germ cell degeneration of the canine testis

“…Similarly, decreases in the number of germ cells and reduced seminiferous epithelium have been documented in aged humans (Zitzmann, 2013) and dogs (Lowseth et al, 1990). However, a previous study showed no relationship between ageing and the quality of spermatogenesis in the dog, judged by cellular assessment of the seminiferous tubule (Peters, de Rooij, Teerds, van Der Gaag, & van Sluijs, 2000). The discrepancy between the findings may be due to different criteria of evaluation or age classification.…”