Rena Bizios

The effects of sustained hydrostatic pressure on select bladder smooth muscle cell functions

PURPOSEnNormal bladder development is believed to depend on the active work of the bladder for storing and expelling urine. When high urinary diversion is performed in infants and the bladder no longer undergoes normal filling, bladder development may be altered, ultimately resulting in bladder dysfunction. To help better understand this relationship of bladder function with growth at the cellular level we developed a novel laboratory method for applying hydrostatic pressure to cell cultures, and we characterized the response of neonatal bladder smooth muscle cells to physiological levels of sustained hydrostatic pressure.nnnMATERIALS AND METHODSnNeonatal 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 activity 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 treatments of heating, freezing, passing through a heparin-sepharose affinity chromatography column or after the addition of suramin, a nonspecific growth factor inhibitor. Statistical analysis was performed using Students t test with p <0.05 considered statistically significant.nnnRESULTSnExposure of bladder smooth muscle cells to sustained hydrostatic pressures of 4, 6 and 8.5 cm. water resulted in increased cell proliferation. Differences became statistically significant (p <0.05) by day 5. Also, conditioned media contained mitogenic activity that was ablated by heating, freezing, passage through a heparin-sepharose affinity chromatography column or with the addition of suramin.nnnCONCLUSIONSnWe have demonstrated a proliferative response of neonatal bladder smooth muscle after exposure to physiological levels of sustained hydrostatic pressure. This response is partially due to 1 or more transferable mitogenic factors. These data support the hypothesis that pressure associated with bladder filling is an important stimulus for detrusor development.

Biological Interactions on Materials Surfaces

Biological interactions at the tissue/implant material interface can be modulated by surface-linked cell-signalling biological molecules. Collagen type I, the main extracellular matrix protein of bone tissue, has been widely investigated in biomolecular surface modification of bone-contacting titanium implant devices. Literature reports on the biological effects of collagen-based coatings are, however, often contradictory. From a biomolecular surface-engineering perspective, a possible explanation is that the definition “collagen-coated surface” encompasses widely different molecular and supramolecular structures: adsorbed collagen, covalently linked collagen, crosslinked collagen, fibrillar versus monomeric collagen, and many other variation of this theme. Relevant details are not always described and proper surface characterization is often lacking. This chapter attempts to build up a rational frame of reference to describe surface modification of implant devices by collagen type I from a surface chemistry point of view, as well as to discuss relevant implications for process design.

A novel in-vitro system for the simultaneous exposure of bladder smooth muscle cells to mechanical strain and sustained hydrostatic pressure.

The novel hydrostrain system was designed in an effort to establish and maintain conditions that simulate the in-vivo mechanical environment of the bladder. In this laboratory system, ovine bladder smooth muscle cells on flexible, 10-cm-dia silastic membranes were exposed simultaneously to hydrostatic pressure (40 cm H2O, a pressure level currently associated with bladder pathologies) and mechanical strains (up to 25 percent) under standard cell culture conditions for 7 h. Under these conditions, Heparin Binding-Epidermal Growth Factor and Collagen Type III mRNA expression were significantly increased (p<0.01 and 0.1, respectively); however, no changes were observed in Collagen Type I mRNA expression. Decreases in the Collagen Type I:Type III ratio following simultaneous exposure of bladder smooth muscle cells to pathological levels of hydrostatic pressure and mechanical strain in vitro are in agreement with clinically observed increases in Collagen Type III with concomitant decreased human bladder compliance. The results of the present study, therefore, provide cellular/molecular level information relevant to bladder pathology that could have significant implications in the field of clinical urology.