Proliferation and apoptotic rates and increased frequency of p63-positive cells in the prostate acinar epithelium of alloxan-induced diabetic rats

Abstract

The effects of experimental type 1 diabetes were investigated in the acinar epithelium of rat ventral prostate, focusing on the rates of cell proliferation and the frequency of apoptosis and p63-positive cells. Type 1 diabetes was induced in adult male Wistar rats by a single alloxan administration (42 mg/kg b.w.) and its effects were analysed for 1 week and 3 months after the establishment of the disease. A group of diabetic rats was treated daily with 5 IU of insulin during 1 week after diabetes had been diagnosed. Immunocytochemical methods for the localization of cell proliferation antigen (PCNA), androgen receptor (AR) and p63 protein were carried out, and apoptotic cells were identified by TUNEL essay. In diabetic rats, testosterone levels reduced drastically after 1 week and in a lower degree after 3 months. In short-term diabetic rats, cell proliferation decreased, and in medium-term, epithelial apoptotic rates increased. In both periods after the onset of diabetes, the frequency of p63-positive cells doubled. Insulin treatment was effective in preventing testosterone decrease, p63-positive cell increase and apoptotic rates, but did not interfere in cell proliferation. This investigation shows that, soon after diabetes onset, there are important modifications in cell proliferation within the acinar prostatic epithelium, and in longer term, there is a marked impact on kinetics of differentiation and cell death, which may initially be attributable to an androgenic fall, but is probably also because of other factors related to diabetes, as changes are considerably different from those resulting from castration.

Figure 1

Histological sections in historresin stained with H&E showing general aspect (small images) and details of acinar epithelium (large images) of the ventral prostate in control, C1 (a) and C2 (e), 1 week diabetic insulin-treated (b), 1 week diabetic without treatment (c and d) and 3 months diabetic rats (f). In control groups, the acinar epithelium shows columnar luminal cells and large luminal area (a, e). After 1 week of diabetes, there is a slight reduction in epithelial height (c) and intense acinar disorganization in some glandular regions (d). In medium-term diabetic group, epithelial cells appear cubic or flattened, indicating the intense epithelial atrophy (f). Arrows: areas of Golgi complex. E: Prostatic acinar epithelium; L: acinar lumen; S: Stroma. Scale bars are the same for all small and large images in the figure: 100 and 20 μm respectively.

Figure 2

PCNA Immunocytochemistry (a–e) and TUNEL method (f–j) in the ventral prostate of 1 week control (a and f), 1 week diabetic (b and g), 1 week diabetic insulin-treated (c and h), 3 months control (d and i) and 3 months diabetic rats (e and j). Note that proliferation in prostate epithelium decreases significantly in older group (d) and also in diabetic groups, especially in short-term (b). The levels of apoptosis increased in prostate after diabetes (g and j), mainly in long-term rats (j). Insulin treatment completely reverses apoptotic levels but not cell proliferation in prostatic epithelium. Scale bar: 20 μm.

Figure 4

(A) Relative frequency (%) of immunoreactions for androgen receptor (black bars) and p63-positive cells (grey bars). (B) Relative frequency (%) of immunoreactions for cell proliferation (black bars) and apoptotic cells (grey bars). (a) Significantly different from respective control, (b) Significantly different between ages, (c) Significantly different from short-term diabetic group (D1). P < 0.05.

Figure 3

Immunocytochemistry for androgen receptor AR (a–e) and p63 (f–j) in the ventral prostate of 1 week control (a and f), 1 week diabetic (b and g), 1 week diabetic insulin-treated (c and h), 3 months control (d and i) and 3 months diabetic rats (e and j). The frequency of AR significantly decreased because of ageing (d), but not because of diabetes (b and e), although a lower intensity of immunoreaction could be observed in short-term diabetic group (b). The number of p63-positive cells is significantly greater in diabetic rats (g and j) and insulin treatment reduced its expression levels close to those observed in control group (h). Scale Bar: 20 μm.