Histological changes of testes in growth hormone transgenic mice with high plasma level of GH and insulin-like growth factor-1

Abstract

Introduction: Overexpression of growth hormone (GH) leads to increase in insulin-like growth factor-1 (IGF-1) plasma level, stimulation of growth and increase in body size, organomegaly and reduced body fat. The action of GH affects all the organs and transgenic mice that overexpress bovine GH (bGH mice) serve as convenient model to study somatotropic axis. Male mice overexpressing GH are fertile, however, they show reduced overall lifespan as well as reproductive life span. The aim of the study was to evaluate the morphology and expression of androgen receptor (AR) and luteinizing hormone receptor (LHR) of bGH mice testes.

Material and methods: The experiment was performed on 6 and 12 month-old bGH male mice and 6 and 12 month-old wild type (WT) littermates (8 animals in each group). The morphology of testes was evaluated on deparaffinized sections stained by the periodic acid-Schiff (PAS) method. Expression of AR and LHR was investigated by immunohistochemistry and diameters of seminiferous tubules (ST) were measured on round cross sections of ST.

Results: We noted larger testes in 6-month bGH mice as compared to normal WT littermates. The morpho-logical observations revealed essentially normal structure of Leydig cells, seminiferous epithelium and other morphological structures. However, some changes like tubules containing only Sertoli cells, tubules with arrested spermatogenesis or vacuoles in seminiferous epithelium could be attributed to the overexpression of GH. In contrast to WT mice, 12 month-old bGH mice displayed first symptoms of testicular aging. The immunoexpres-sion of AR and LHR was decreased in 12 month-old bGH males as compared to 12 month-old WT mice and younger animals.

Conclusion: Chronic exposure to elevated GH level accelerates testicular aging and thus potentially may change response of Leydig cells to LH and Sertoli and germ cells to testosterone.

Keywords: GH transgenic mice; IHC; LHR; androgen receptor; testis histology.

Figure 1. Morphology of a testis of 6-month-old WT (A,C,E) and bGH mice (B,D,F)

Red arrows – tubules with only Sertoli cells, yellow arrow - vacuole, black arrows - Leydig cells, asterix – lipofuscin-storing cell. PAS staining. Magnifications: 20× (A,B), 40× (C,D), 60× (E,F). Only representative microphotographs are presented.

Figure 2. Morphology of testes of 12-mont-old WT (A,C,E) and bGH mice (B,D,F)

Yellow arrow - vacuole, black arrows - Leydig cells, asterix – lipofuscin-storing cell. Inserts: tubules with missing generations of germ cells (B) and premature sloughed germ cells (D).PAS staining. Magnifications: 20× (A,B), 40× (C,D), 60× (E,F). Only representative microphotographs are presented.

Figure 3. Immunoexpression of androgen receptors in testes of 6-month-old WT (A) and bGH (B) and 12-month-old WT (C) and bGH (D) mice

Brown arrows – Sertoli cells, magenta arrows – Leydig cells, blue arrows – peritubular cells. Magnification: 40×. Upper insert on panel A – negative control (20×).

Figure 4. Immunoexpression of LH receptors in testes of 6-month-old WT (A) and bGH (B) and 12-month-old WT (C) and bGH (D) mice

Magenta arrows – Leydig cells. Magnification: 40×. Insert on panel A– negative control (40×).