doi:10.1369/jhc.5A6692.2005
Volume 53 (10): 1257-1271, 2005 Copyright ©The Histochemical Society, Inc. Localization of Type 8 17ß-hydroxysteroid Dehydrogenase mRNA in Mouse Tissues as Studied by In Situ Hybridization
Oncology and Molecular Endocrinology Research Center, Laval University Medical Center (CHUL) and Laval University, Québec, Canada Correspondence to: Dr. Georges Pelletier, Oncology and Molecular Endocrinology Research Center, Laval University Hospital (CHUL), 2705 Laurier Boulevard, Québec, Québec, G1V 4G2, Canada. E-mail: georges.pelletier{at}crchul.ulaval.ca
The enzyme type 8 17ß-hydroxysteroid dehydrogenase (17ß-HSD) selectively catalyzes the conversion of estradiol (E2) to estrone (E1). To obtain detailed information on the sites of action of type 8 17ß-HSD, we have studied the cellular localization of type 8 17ß-HSD mRNA in mouse tissues using in situ hybridization. In the ovary, hybridization signal was detected in granulosa cells of growing follicles and luteal cells. In the uterus, type 8 17ß-HSD mRNA was found in the epithelial (luminal and glandular) and stromal cells. In the female mammary gland, the enzyme mRNA was seen in ductal epithelial cells and stromal cells. In the testis, hybridization signal was observed in the seminiferous tubule. In the prostate, type 8 17ß-HSD was detected in the epithelial cells of the acini and stromal cells. In the clitoral and preputial glands, labeling was detected in the epithelial cells of acini and small ducts. The three lobes of the pituitary gland were labeled. In the adrenal gland, hybridization signal was observed in the three zones of the cortex, the medulla being unlabeled. In the kidney, the enzyme mRNA was found to be expressed in the epithelial cells of proximal convoluted tubules. In the liver, all the hepatocytes exhibited a positive signal. In the lung, type 8 17ß-HSD mRNA was detected in bronchial epithelial cells and walls of pulmonary arteries. The present data suggest that type 8 17ß-HSD can exert its action to downregulate E2 levels in a large variety of tissues. (J Histochem Cytochem 53:12571271, 2005)
Key Words: type 8 17ß-hydroxysteroid dehydrogenase estradiol inactivation estrone mouse tissues in situ hybridization
THE 17ß-HYDROXYSTEROID DEHYDROGENASE (17ß-HSD) are enzymes responsible for the formation and inactivation of active androgens and estrogens. Multiple types of 17ß-HSDs (named types 112) have been cloned and have been shown to be expressed in several human and animal tissues (Peltoketo et al. 1999 25% of that of E2 to E1. Peltoketo et al. (1999)
By Northern blot analysis, the mouse type 8 17ß-HSD mRNA was found to be expressed in the ovary, testis, kidney, and liver (Fomitcheva et al. 1998
Animals Four adult male (2630 g) and female (2427 g) C57BL6 mice were housed under constant temperature (21 ± 1C) and light (lights on from 0600 to 2000 hr) regimen. The animals received Purina Chow (Ralston-Purina, St Louis, MO) and tap water ad libitum. The experiment was conducted in an animal facility approved by the Canadian Council on Animal Care and the Association for Assessment and Accreditation of Laboratory Animal Care. The study was performed in accordance with the Canadian Council on Animal Care Guide for Care and Use of Experimental Animals. The animals were all perfused between 9 and 10 hr for histological procedures as described in the following section. The females were on proestrus.
Histological Procedures
In Situ Hybridization After hybridization, cover slips were removed and slides were rinsed in 2x SSC at room temperature for 30 min. Sections were digested by RNase A (20 µg/ml in 2x SSC) at 37C for 30 min, rinsed in decreasing concentrations of SSC (2x SSC and 1x SSC) for 30 min at room temperature, washed in 0.5x SSC for 30 min at 37C, followed by 90 min at room temperature in 0.5x SSC, at 60C in 0.1x SSC and finally for 30 min at room temperature in 0.1x SSC. The sections where then dehydrated and exposed to Kodak Biomax Mr films for 38 d before being coated with liquid photographic emulsion (Kodak-NTB2; diluted 1:1 with water). Slides were exposed for 745 d, developed in Dektol developer (Kodak) for 2 min, and fixed in rapid fixer (Kodak) for 4 min. Thereafter, tissues were rinsed in running water for 30 min, counterstained with hematoxylin and rapidly dehydrated through graded concentrations of ethanol, cleared in toluene, and cover-slipped with Permount (Fisher Scientific, Montreal, Canada).
After 3 to 8 days of exposure of the films, specific hybridization signal could be detected in the following tissues: ovary, oviduct, uterus, mammary gland, vagina, testis, prostate, clitoral gland, preputial gland, pituitary gland, adrenal gland, kidney, dorsal skin, and lung. No specific labeling have been observed in seminal vesicles, epididymis, jejunum, and colon. From photographic emulsion-coated sections, precise information could be obtained about the cell types expressing type 8 17ß-HSD mRNA in the different tissues. In the ovary, specific labeling could be observed in granulosa cells in growing follicles at all stages of development and in luteal cells of corpora lutea (Figure 1). In the uterus, the hybridization signal was detected on epithelial cells (both luminal and glandular) and stromal cells, whereas the myometrial smooth muscle cells were unlabeled (Figure 2). In the vagina, both epithelial and stromal cells exhibited mRNA expression (Figure 3). In the female mammary gland, specific labeling was seen in periductal stromal cells and in ductal epithelial cells (Figure 4). In the clitoral gland, type 8 17ß-HSD mRNA was detected in epithelial cells of both acini and small ducts. The large excreting ducts were devoid of any specific reaction (Figure 5).
In the testis, a specific hybridization signal was observed over seminiferous tubules, Leydig cells being devoid of any specific labeling (Figure 6). Because we used frozen sections, a procedure that does not totally preserve the integrity of the tissues, it was not possible to identify the cell types expressing type 8 17ß-HSD mRNA in the tubules. In the prostate, in situ hybridization signal was observed in both the epithelial cells bordering the acinar lumen and the stromal cells (Figure 7). In the preputial gland, which is homologous to the clitoral gland, specific labeling was similarly observed over the sebaceous cells forming the acini and the epithelium of the ducts.
In the pituitary gland, adrenal glands, kidney, liver, dorsal skin, and lung, the expression of type 8 17ß-HSD was similar in both sexes. In the pituitary gland, specific autoradiographic reactions were detected over the cells of the three lobes (Figure 8). In the anterior and intermediate lobes, the vast majority of cells if not all the cells were labeled, whereas, in the posterior lobe, the silver grains were mostly detected over the pituicytes. In the adrenal glands, the three zonae of the cortexnamely glomerulosa, fasciculata, and reticularis zonawere specifically labeled (Figure 9). No specific reaction could be found in the adrenal medulla. In the kidney, hybridization signal was found in the epithelial cells of proximal convoluted tubules (Figure 10). In the liver, all the hepatocytes were expressing the enzyme mRNA (Figure 11). In the lung, type 8 17ß-HSD mRNA was found to be expressed in bronchial epithelial cells and walls of pulmonary arteries (not shown). In the dorsal skin, specific labeling was detected in the stroma (not shown).
In all the tissues expressing type 8 17ß-HSD mRNA, hybridization with the radiolabeled sense probe generated only a light uniform background (Figures 111).
The present data obtained by in situ hybridization clearly demonstrate that type 8 17ß-HSD mRNA is expressed in reproduction organs and in several peripheral tissues in male and female mouse. This appears as the first report on the cellular localization of type 8 17ß-HSD mRNA.
By Northern blot analysis, Fomitcheva et al. (1998)
We report for the first time that type 8 17ß-HSD mRNA is expressed in the oviduct and uterus, the hybridization signal being found in the epithelial and stromal cells, but not in the myometrium. The enzyme might contribute to the fine regulation of estrogen levels in the endometrium, which is very sensitive to estrogen variations during the ovarian cycle. In human, the loss of estrogen inactivating enzyme (e.g., types 2 and 8 17ß-HSD) expression has been proposed as a mechanism involved in the pathogenesis of endometriosis (Bulun et al. 2002
In the testis, type 8 17ß-HSD mRNA was expressed in germ cells, but not in Leydig cells, thus suggesting that the enzyme may contribute to the local metabolism of E2 and then protect germinal cells against exposure to high levels of estrogens. By Northern blot analysis, type 8 17ß-HSD mRNA has already been detected in the mouse testis, but there was no indication about the cell types involved in the expression of the enzyme mRNA (Fomitcheva et al. 1998
In the pituitary of animals of both sexes, the hybridization signal is diffusely located in the anterior and intermediate lobes, whereas in the posterior lobe, the labeling appears mostly associated with the pituicytes. In the female, type 8 17ß-HSD is likely involved in the local regulation of estrogens coming from the general circulation and locally produced estrogens. In the male, the enzyme might regulate the estrogens locally produced through the action of type 1 17ß-HSD and aromatase (Sharpe 1998
In the kidney, we observed that the expression of type 8 17ß-HSD mRNA was confined to proximal tubules. This finding is in agreement with previous reports indicating that Ke 6 or type 7 17ß-HSD protein could be localized by immunofluorescence to the proximal tubules and collecting tubules (Aziz et al. 1996
In the liver, it appears that all the hepatocytes express the enzyme mRNA and might be involved in the conversion of E2 to E1. Type 7 17ß-HSD, the enzyme that converts E1 to E2, has also been found to be expressed in all the hepatocytes (Pelletier et al. 2005 In summary, we report for the first time the histological identification of the cell types expressing type 8 17ß-HSD mRNA in several tissues including gonads in the adult mouse. In those tissues, the role of the enzyme is likely related to the local regulation of estradiol levels coming from the general circulation or locally produced.
Received for publication March 18, 2005; accepted March 23, 2005
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