Km. Haberstroh et al., The effects of sustained hydrostatic-pressure on select bladder smooth muscle cell functions, J UROL, 162(6), 1999, pp. 2114-2118
Purpose: Normal bladder development is believed to depend on the active wor
k of the bladder for storing and expelling urine. When high urinary diversi
on is performed in infants and the bladder no longer undergoes normal filli
ng, bladder development may be altered, ultimately resulting in bladder dys
function. To help better understand this relationship of bladder function w
ith growth at the cellular level we developed a novel laboratory method for
applying hydrostatic pressure to cell cultures, and we characterized the r
esponse of neonatal bladder smooth muscle cells to physiological levels of
sustained hydrostatic pressure.
Materials and Methods: Neonatal ovine smooth muscle cells staining positive
for desmin and alpha-smooth muscle actin were exposed to pressures of 0.3
(controls), 2, 4, 6 and 8.5 cm. water for 1, 3, 5 and 7 days. At the end of
the experiments the cells were fixed, stained and counted. Mitogenic activ
ity of the supernatant media from bladder smooth muscle cells exposed to 8.
5 cm. water for 5 days (conditioned media) was tested before and after trea
tments of-heating, freezing, passing through a heparin-sepharose affinity c
hromatography column or after the addition of suramin, a nonspecific growth
factor inhibitor. Statistical analysis was performed using Student's t tes
t with p <0.05 considered. statistically significant.
Results: Exposure of bladder smooth muscle cells to sustained hydrostatic p
ressures of 4, 6 and 8.5 cm. water resulted in increased cell proliferation
. Differences became statistically significant (p <0.05)by day 5. Also, con
ditioned media contained mitogenic activity that was ablated by heating, fr
eezing, passage through a. heparin-sepharose affinity chromatography column
or with the addition of suramin.
Conclusions: We have demonstrated a proliferative response of neonatal blad
der smooth muscle after exposure to physiological levels of sustained hydro
static pressure. This response is partially due to 1 or more transferable m
itogenic factors. These data support the hypothesis that pressure associate
d with bladder filling is an important stimulus for detrusor development.