The localisation and expression of 5 alpha-reductase types I and II mRNAs in human hyperplastic prostate and in prostate primary cultures

Abstract

The expression and localisation of mRNAs for 5 reductase Type I (5 R-I) and Type II (5 R-II) isoenzymes in human benign prostatic hyperplasia (BPH) were investigated by RT-PCR and by in situ hybridisation (ISH) using digoxigenin labelled riboprobes. In addition, we also examined the isoenzymes mRNA expression in primary BPH cultures of separated stroma/fibroblast and epithelial cells to determine whether primary cultures are appropriate models in which to investigate 5 R activity and regulation. The results demonstrated conclusively the presence of mRNA encoding both isoenzymes in all specimens so far examined. Additionally, the presence of a functional 5 R-I and -II activity in BPH was confirmed by enzyme assays. ISH studies localised the mRNA expression to both the fibroblast/stromal component as well as the epithelial cells of the hyperplastic tissue. In the glandular regions the expression for both isoenzymes was particularly strong in the basal layers of the epithelium whereas mRNA expression in the secretory cells was less pronounced. Expression of 5 R-I and -II mRNAs in fibroblast was on the other hand variable with high expression in some areas and little in others. These findings were supported by our primary culture experiments which demonstrated that both the fibroblast and epithelial cells maintain a capacity to express both isoenzymes in vitro. In the case of the fibroblast, the capacity to express the isoenzymes was maintained following the sequential passaging of the cells up to passage 6, after which the cells no longer expressed either isoenzyme.

Selective Interactions between Prostate Fibroblast and Epithelial Cells in Co-Culture Maintain the BPH Phenotype

“…This is distinctive from earlier models where 5·-reductase activity was either absent or depleted and no previous system ever expressed both iso-enzymes simultaneously [11,21,22]. The properties of 5·-reductase activity in the coculture model resemble those which have previously been detected in the human tissue [22] and we have no reason to believe that these are any different.…”

“…This is distinctive from earlier models where 5·-reductase activity was either absent or depleted and no previous system ever expressed both iso-enzymes simultaneously [11,21,22]. The properties of 5·-reductase activity in the coculture model resemble those which have previously been detected in the human tissue [22] and we have no reason to believe that these are any different. Whilst earlier studies had indicated that only the 5·-RII iso-enzyme was present in the human prostate gland, there is now sufficient evidence derived from biochemical analysis at the mRNA and protein levels of tissues from BPH and cancer patients to demonstrate that both iso-enzymes are present in prostate tissue; these have been localised in both the fibroblast and epithelial components of the glands [22] and this is now confirmed by our co-culture system.…”

Dihydrotestosterone and the Concept of 5α–Reductase Inhibition in Human Benign Prostatic Hyperplasia

“…The remaining DHT in the prostate is likely to be the result of type 1 5α–reductase, either coming from the 30% of DHT remaining in the serum of men given finasteride or from intraprostatic type 1 5α–reductase. Although initial studies did not demonstrate type 1 protein in human prostate, more recent studies indicate that both type 1 and type 2 mRNA, protein, and enzyme activity are indeed present in prostate tissue [64, 65, 66, 67, 68, 69, 70]. …”

Isoenzyme type 1 of 5alpha-reductase is abundantly transcribed in normal human genital skin fibroblasts and may play an important role in masculinization of 5alpha-reductase type 2 deficient males

“…5RI is transcribed in different androgen-dependent organs like the epididymis (18), the testis (19) and the prostate (20,21). The localisation of 5RI in the cell nucleus of human prostate cells (22) and the close spatial relationship to the androgen receptor in prostate, epididymidis and testis reported by Aumü ller et al, also suggest a functional connection between this isoenzyme and cellular androgen metabolism (19).…”