Structural organization of fibrous connective tissue in the periacinar region of the transitional zone from normal human prostates as revealed by scanning electron microscopy.

OBJECTIVE: To analyse, using scanning electron microscopy (SEM), the organization of stromal fibrous components in the transitional zone (TZ) from normal human prostates; because of its association with disease, greater emphasis was placed upon the periacinar region of the stroma.
MATERIALS AND METHODS: TZ specimens were obtained from normal prostates during autopsy of six men, aged 18-30 years, who had died from accidents. Tissue was fixed for SEM in a modified Karnovsky solution for 48 h at 4 degrees C, and to visualize the three-dimensional organization of the stroma, samples were treated to remove cells.
RESULTS: In acellular preparations, narrow fibrous septa formed a dense and supportive scaffold for ducts and acini, and a smooth and homogeneous fibrous sheet, herein identified as pars fibroreticularis, lined the acinar lumen. More internally, fibrous septa had a spongy organization with dense lamellae. Higher magnification showed that the smooth luminal sheet is made of 115-154-nm thick fibrils in a tight parallel arrangement. Just under this layer there was a meshwork of fibrils 77-115 nm thick that were orientated in less defined directions.
CONCLUSION: In the TZ of the human prostate, dense stromal fibrous components around acini act as a barrier that might enhance local cellular responses and events that occur in disorders such as benign prostatic hyperplasia. The periacinar pars fibroreticularis supports the notion of high structural variability in this region of basement membranes.