Mesenchymal-epithelial interactions in bladder smooth muscle development: epithelial specificity.

PURPOSE: We previously showed that mesenchymal-epithelial interactions are necessary for the development of bladder smooth muscle. Specifically without bladder epithelium embryonic bladder mesenchyme does not differentiate into smooth muscle. We determine whether this process is specific to bladder epithelium or whether epithelial cells from other organ systems induce bladder mesenchyme to differentiate into smooth muscle, as well as whether epithelial age is an important variable. MATERIALS AND METHODS: We recombined 14-day bladder mesenchyme before smooth muscle differentiation with rat epithelium from 14-day, 19-day, newborn and adult bladder, ureter, colon, ileum, stomach, cornea and epidermis. In addition, bladder epithelium was recombined with 14-day embryonic small intestinal, 14-day embryonic gastric and newborn seminal vesicle mesenchyme. All tissue recombinants were grafted under the renal capsule of an adult rat syngeneic host for 3 weeks. RESULTS: Immunohistochemical analysis with antibodies directed against smooth muscle alpha-actin revealed that all epithelial types studied induced bladder mesenchyme to differentiate into smooth muscle, although to different degrees. Induction of smooth muscle was independent of urothelial age. In addition, bladder epithelium induced intestinal, gastric and seminal vesicle mesenchyme to differentiate into smooth muscle and express an overall morphological pattern indicative of the bladder fibromuscular wall. CONCLUSIONS: The mechanism whereby urothelium induces bladder mesenchyme to differentiate into smooth muscle is not specific to embryonic urothelium. Older urothelium and heterotypic epithelium also induce smooth muscle differentiation. With the common use of bowel, stomach and ureteral segments for bladder augmentation it is important to understand the interaction of different types of epithelium with the native bladder.

Neonatal management. Role for early intervention.

Although performing pyeloplasty on an infant with a relatively healthy kidney prior to the onset of renal damage is not as well-accepted as "aggressive observation," the authors argue that early intervention is the more "conservative" or safe method of treatment for infants with ureteropelvic junction (UPJ) obstruction. Using experimental and clinical data, the authors demonstrate that prolonged partial UPJ obstruction in the developing kidney causes significant renal morbidity with time.

Development and regenerative ability of bladder in the transgenic epidermal growth factor receptor gene knockout mouse.

PURPOSE: During embryogenesis we have previously shown that urothelium is essential for normal bladder growth and development. Urothelial growth may be mediated by peptides of the epidermal growth factor family, since the epidermal growth factor receptor is expressed in bladder urothelium and epidermal growth factor has been shown to induce deoxyribonucleic acid synthesis and migration of urothelial cells in vitro. Bladders from transgenic mice in which the epidermal growth factor receptor gene has been knocked out were used to examine the possible role of epidermal growth factor in bladder growth and development, detrusor neoformation and bladder regeneration. MATERIALS AND METHODS: Whole bladders from transgenic knockout mice 0 to 10 days old were surgically implanted into the "subdetrusor" space of adult athymic nude rat hosts. After 10 days the dome of the host rat bladder was resected with the distal half of the transplanted knockout mouse bladder. Augmentation cystoplasty was then performed on the host rat bladder using acellular tissue matrix with a portion of the acellular matrix sutured directly to the transplanted knockout mouse bladder. The animals were sacrificed 2 or 3 weeks postoperatively. To test the ability of knockout bladder tissue to regenerate into the transplanted matrix species specific Hoechst dye was used to determine whether the cells within the acellular matrix were of host (rat) or transplant (knockout mouse) origin. Immunocytochemical analysis was used to assess muscle neoformation. Controls consisted of wild-type mouse bladders from the same litter. Since epidermal growth factor receptor knockout mice usually die in the neonatal period, the role of the epidermal growth factor receptor signaling pathway in long-term muscle development was evaluated by transplanting knockout and wild-type control bladders under the renal capsule of athymic nude mouse hosts. These mice were sacrificed 30 days later and muscle development was assessed using immunocytochemical analysis. RESULTS: Histologically the transplanted acellular tissue matrix in the experimental and control animals appeared the same, containing well differentiated urothelial and smooth muscle cells that had migrated into the transplanted matrix. Staining with species specific Hoechst dye revealed that urothelial and smooth muscle cells transplanted from the knockout and wild-type mouse bladders invaded and regenerated in the transplanted matrix. There was no apparent difference in the amount of knockout or control mouse tissue in the transplanted matrix. Also, the long-term renal capsule transplants revealed no difference in the amount of smooth muscle in the epidermal growth factor receptor knockout and wild-type bladders. CONCLUSIONS: Signaling through the epidermal growth factor receptor pathway is not necessary for normal bladder development or bladder regeneration after injury.

The effect of testosterone on androgen receptors and human penile growth.

PURPOSE: Recent rat studies suggest that early exposure to exogenous testosterone accelerates the loss of androgen receptors and compromises eventual penile length. In humans we hypothesize that down regulation of the androgen receptor is not the mechanism that stops penile growth. To test this hypothesis we investigated the effects of androgen deprivation and supplementation on the developing human penis. MATERIALS AND METHODS: A total of 15 normal human fetal penises at 7 to 19 weeks of gestation (mean plus or minus standard deviation 12 +/- 4.5) was divided in half sagittally. Specimens were grafted beneath the renal capsule of male athymic nude mice or nude rats. Three groups of host animals were prepared, including 10 with no testosterone that were castrated at grafting, 15 with testosterone and 5 with super testosterone in which 50 mg. testosterone propionate pellets were implanted subcutaneously at grafting. Each fetal penile specimen was its own control, since half was implanted into an intact animal and the other into a castrated or super testosterone host. Six weeks after grafting the specimens were analyzed for gross size (length), histology and expression of androgen receptors. RESULTS: All human fetal penile specimens grew from the nadir size and appeared as white exophytic growths on the surface of the host kidneys. Normal grafts were larger than castrate specimens (mean 6.9 +/- 2.1 versus 3.9 +/- 2.1 mm., p = 0.014). Mean length of the super testosterone specimens (7.3 +/- 2.3 mm.) was not significantly greater than that of normal specimens (p = 0.797). Histological analysis revealed that all specimens were composed of viable penile tissue. Cellular density of the castrate penises was approximately 2 times greater than that of the normal and super testosterone specimens (40.6 +/- 5.9 versus 25.1 +/- 2.8 cells per cm.2, p > 0.001), as calculated on enlarged micrographs. Supraphysiological doses of testosterone did not change the histology compared to controls. Immunohistochemical localization revealed androgen receptors expressed throughout the corporeal bodies, surrounding stroma and penile skin with intracellular localization to nucleus. The mean proportion of cells expressing androgen receptors was higher in the castrate (29.4 +/- 5.2 cells per cm.2) than in the normal (24.0 +/- 3.7) and super testosterone (24.7 +/- 4.5) grafts (p = 0.005). However, in regard to growth there was no change in the proportion of androgen receptor positive cells among the groups. CONCLUSIONS: Testosterone influences penile growth, possibly as a result of extracellular stromal expansion. The number of androgen receptor positive cells in the human fetal penis did not change among the castrate, normal and super testosterone hosts. These experiments support the hypothesis that penile growth cessation is mediated by mechanisms other than down regulation of the androgen receptor. Furthermore, these data support the hypothesis that early administration of androgen to prepubertal male individuals does not result in a shorter phallus in adulthood.

Mesenchymal-epithelial interactions in the bladder.

During bladder development, undifferentiated mesenchymal and epithelial cells undergo an orderly sequence of differentiation defined by the expression of smooth-muscle (alpha-actin, myosin, vinculin, desmin, vimentin, and laminin) and epithelial (cytokeratins 5, 7, 8, 14, 18 and 19) protein markers. This process requires mesenchymal-epithelial interactions with bladder epithelium (urothelium) necessary for the differentiation of bladder smooth muscle. Peptide growth factors such as keratinocyte growth factor (KGF) and transforming growth factors (TGF) alpha and beta are likely candidates as mediators of these mesenchymal-epithelial interactions. Transcripts for KGF, TGF alpha, and TGF beta are regulated during bladder development and during smooth-muscle hypertrophy secondary to bladder-outlet obstruction. Finally, two experimental bladder models--(1) partial outlet obstruction and (2) regeneration of bladder smooth muscle into an acellular tissue matrix--are described in the context of mesenchymal-epithelial interactions in the bladder.