I. A subpopulation of human urothelial cells is stimulated to proliferate by treatment in vitro with lipoteichoic acid, a cell wall component of Streptococcus faecalis

Abstract

Urinary tract infection with gram-positive bacteria is common. Avenues for ingress of bacteria into the bladder include luminal and suburothelial infection. Terminally differentiated superficial urothelial cells lining the lumen of the bladder are often shed in response to infection. In contrast, infection-induced altered function of progenitors of urothelial cells residing in the basal layer of the urothelium is likely to have long lasting effects on the structure and function of the urothelium. The main objective of the present studies was to investigate in vitro the possibility that exposure to lipoteichoic acid, a cell wall component of the gram-positive Streptococcus faecalis (LT-2), stimulates basal urothelial cells to proliferate. To simulate conditions that restrict proliferation and inhibit terminal differentiation of urothelial cells in the basal layer, secondary cultures of urothelial cells (UT) were grown on collagen or fibronectin coated substrate in medium containing low levels of Ca2+ (0.2 mM) and growth factors (0.005% bovine pituitary extract [BPE]). Under these conditions, UT cultures displayed a highly reproducible colony size distribution, possibly due to the fact that colonies were progeny of basal cells with various proliferative potentials, retained in vitro. In cultures grown under growth-restricting conditions the majority of progenitors appeared to be quiescent, just like stem cells in the basal layer of the urothelium. Thus, the population of large colonies (more than six cells/colony), was small when a steady state of growth was achieved, 3-7 days after seeding. Growth factors (0.005-0.5% BPE) caused a dose-dependent increase in this population of large colonies. Moreover, treatment of UT grown under growth-restricting conditions (0.005% BPE) with LT-2 increased steady-state levels of the population of large colonies to levels obtained in cultures growing under optimal conditions with respect to growth factors. These results indicated that the subpopulation of progenitors, quiescent under normal conditions, could be stimulated to proliferate. Two lines of evidence were consistent with the possibility that treatment with LT-2 stimulated proliferation of the subpopulation of progenitors and that large colonies were the progeny of this subpopulation of single cells: (1) treatment with LT-2 increased the percentage of single cells that incorporated bromodeoxyuridine (i.e., proliferated) in a time-dependent manner. (2) An increase in the percentage of large colonies was found following LT-2-triggered proliferation of single cells. We propose that, under normal conditions, cells produced in response to LT-2-triggered proliferation of stem cells are removed from the system due to an increased rate of differentiation followed by apoptosis. Recurrent infection and inflammation may not allow these processes to proceed effectively, resulting in chronic injury to the bladder. Moreover, under conditions in which stem cells accumulate mutations that incapacitate their progeny to undergo apoptosis, L...

II. Long-term treatment with lipoteichoic acid fromStreptococcus Faecalis affects differentiation and expression and cellular distribution of β1 integrins in human urothelial cells

“…In conclusion, taken together, our studies in vitro are consistent with the possibility that exposure to LT-2 stimulates a subpopulation of quiescent progenitors of urothelial cells in the basal layer to begin proliferating rapidly, within 8 h after exposure to this agent (Fig. 12) (Elgavish et al, 1996). The rate of differentiation of their progeny is markedly stimulated within 24-72 h after being exposed to LT-2 ( Fig.…”

Bacterial Wall Components such as Lipothecoid Acid, Peptidoglycan, Liposaccharide and Lipid A Stimulate Cell Proliferation in Intestinal Epithelial Cells

“…The LTA of Streptococcus faecalis stimulates cell proliferation in our intestinal cell lines which is in agreement with a similar mitogenic action reported on human urothelial cells (17). No other reports are available about actions on cell division in ×itro, al- though LTAs of S. faecalis releases TNF-a, IFN-a and IL-1 in ×i×o and exert antitumour activity in mice brosarcoma (18).…”

III. Nitric oxide mediates the action of lipoteichoic acid on the function of human urothelial cells

“…bladder infection with gram-positive bacteria (Elliott et al, 1985). Our studies in vitro, showing that LT stimulate proliferation of a subpopulation of cells with high proliferative potential (Wille et al, 1992;Elgavish et al, 1996a), possibly stem cells (Potten and Morris, 1988), and subsequent differentiation of their progeny (Elgavish et al, 1996131, support this possibility. Moreover, as expected of more differentiated epithelial cells (Watt, 1989;Hertle et al, 1991), long-term exposure to LT inhibits the expression of PI subunit of integrins and some of the remaining integrins redistribute to cell-cell contacts (Elgavish et al, 1996b), resulting in inhibition of cell/ECM interactions (Elgavish et al, 1994).…”

“…The sthulatory effect of LT-2 on proliferation of a UT subpopulation with high proliferative potential and the subsequent differentiation of resulting large colonies requires NO Our previous studies have shown that exposure to LT-2 stimulated the proliferation of a subpopulation of poorly differentiated urothelial cells with high proliferative potential (Wille et al, 1992;Elgavish et al, 1996a), resulting in large colonies (>6 cells/colony) that differentiated more rapidly than those in untreated cultures (Elgavish et al, 1996b).…”

“…The possibility that NO may mediate the effect of LT-2 on proliferation was tested first. Cells grown under growth restricting conditions that simulated those in the basal layer (Elgavish et al, 1996a), were treated for 24 hr with 25 pg/ml LT-2, in the presence or absence of 1 mh4 L-NAME. Some UT were treated with both agents.…”