ORGANIZATION AND RELATIVE CONTENT OF SMOOTH MUSCLE CELLS, COLLAGEN AND ELASTIC FIBERS IN THE CORPUS CAVERNOSUM OF RAT PENIS:

The mouse as a model for the study of penile erection: moving towards a smaller animal

We evaluated erectile haemodynamics in mice and characterized the corpus cavernosum morphologically. Four-month-old male BALB/c mice and Sprague-Dawley rats were used. The following stimulation parameters were tested to achieve maximal erectile responses: voltage, 1-6 V; frequency, 6-24 Hz; pulse width, 1 msec; duration, 1 min (n = 7 per group). In a separate group of mice and rats (n = 10 per group), we measured systemic arterial pressure by use of either a 24-gauge angiocatheter or smaller calibre PE-10 tubing. Cavernous tissues from mice, rats or patients with psychogenic erectile dysfunction were stained for factor VIII, alpha-actin and Masson trichrome. Electrical stimulation of the cavernous nerve in mice produced voltage-dependent erectile responses of up to 5 V, with the highest response at a frequency of 12 Hz. The maximal intracavernous pressure recorded at this stimulation parameter was comparable with that in rats. A PE-10 catheter was more reliable for measuring systemic arterial pressure in mice than was a 24-gauge angiocatheter, and the values recorded were similar between mice and rats. The content of endothelial cells, smooth muscle cells and collagen was similar between mice and rats. However, the cavernous tissue of both animals contained lesser amounts of smooth muscle cells and greater amounts of collagen than that of humans (p < 0.01). These results suggest that the mouse is a useful and technically feasible model for the study of penile erection and has functional and structural properties similar to those of rats.

Comparative analysis of the penis corpora cavernosa in controls and patients with erectile dysfunction

OBJECTIVE

To evaluate the presence of structural disorders of the corpora cavernosa in patients with erectile dysfunction (ED), as despite new drugs being effective in many men with ED, some aspects of structural disorders of the corpora cavernosa remain unknown.

MATERIALS AND METHODS

Biopsy specimens were taken from the corpora cavernosa of seven patients (mean age 57.8 years, range 51-72) with severe ED who had a penile prosthesis implanted. The controls tissues were fragments of corpora cavernosa obtained from autopsies of six men (mean age 52.3 years, range 40-66) who died from causes unrelated to the urogenital system. For light microscopy, the specimens were processed routinely to paraffin wax, and by immunohistochemistry to evaluate elastic fibres, and by Masson's trichrome to analyse collagen and smooth muscle fibres. Stereological methods were used to quantitatively evaluate the different elements (as a percentage).

RESULTS

The percentages of the different elements in the human penis of controls and men with ED, respectively, were: elastic fibres 13.2% and 9.1%; collagen fibres 40.8% and 41.6%; and smooth muscle, 40.4% and 42%.

CONCLUSIONS

In patients with ED there was a statistically significant reduction in the percentage of elastic fibres, but no statistically significant difference in collagen and smooth muscle fibres, and no appreciable differences in collagen distribution between the groups.

Increased and localized accumulation of chondroitin sulphate proteoglycans in the hyperplastic human prostate

OBJECTIVE

To analyse by immunohistochemistry the expression of chondroitin sulphate (CS) (detected in the hyperplastic prostate and possibly affecting the proliferation of prostate cells) in benign prostatic hyperplasia (BPH) to determine its distribution and location.

MATERIALS AND METHODS

Samples of BPH were obtained from 11 patients (aged 58-83 years) and controls consisting of the transitional zone of five prostates from young men aged 19-27 years. Tissue sections were labelled with antibodies against CS, perlecan, type IV collagen, laminin, and smooth muscle cell (SMC) alpha-actin. The amount of CS immunostaining was estimated by semi-quantitative scoring and correlated with prostate-specific antigen (PSA) level and prostate size.

RESULTS

The anti-CS antibody faintly stained the stroma of normal prostates, but in BPH samples the staining was intense and concentrated around acini, including the periphery of adjacent SMCs. This staining pattern was totally absent in the normal samples. Type IV collagen, perlecan and laminin were homogeneously distributed in the whole stroma of both normal and BPH samples. There was no significant correlation between intensity of CS staining and either PSA or prostate size.

CONCLUSIONS

The expression of CS proteoglycans is increased in BPH, where they co-locate with basement membranes of the acinar epithelium and of peri-acinar SMCs. This enhanced expression is specific for these proteoglycans, as other basement membrane components are unaffected, and this may result from the regulatory effects of local factors that are active in BPH.