LONG-TERM TREATMENT WITH LIPOTEICHOIC ACID FROM STREPTOCOCCUS-FAECALIS AFFECTS DIFFERENTIATION AND EXPRESSION AND CELLULAR-DISTRIBUTION OF BETA(1) INTEGRINS IN HUMAN UROTHELIAL CELLS .2.

Gram-positive bacteria are recognized pathogens in urinary tract infec tions. Cellular mechanisms triggered by lipoteichoic acids (LTs), cell wall components of gram-positive bacteria, have not been completely d efined. We have postulated that infection-induced altered function of progenitors of urothelial cells residing in the basal layer is likely to have long lasting effects on the architecture and function of the u rothelium. Our recent studies in vitro showed that treatment of poorly differentiated urothelial cells of basal type with LT from Streptococ cus faecalis (LT-2) stimulated rapid proliferation of a subpopulation of progenitors of urothelial cells, supporting this possibility (Elgav ish et al., 1996, J. Cell. Physiol., 169: 42-51). The hypothesis under lying the present studies was that, following LT-triggered increase in proliferation of progenitors, the rate of differentiation of the resu lting progeny was also stimulated. We proposed that this mechanism may allow rapid removal of cells from the injured area and replacement by cells that have not been exposed to infection. To simulate in vitro c onditions in the basal layer that inhibit terminal differentiation, ce lls grew on fibronectin or collagen-coated substrate, in medium contai ning law Ca2+ (0.2 mM) and low levels of growth factors (0.005% bovine pituitary extract [BPE]). During the last 3 days in culture, cells gr ew in the same low Ca2+ (0.2 mM) medium, but without BPE, with or with out LT-2. In a positive control group, cells grew during their last 3 days in culture in medium without BPE and LT-2 but in which levels of CA(2+) were higher (2 mM), a condition known to stimulate differentiat ion in other cell types. Several lines of evidence supported the possi bility that long-term treatment with LT-2 stimulated progression of la rge colonies (i.e., the progeny resulting from LT-triggered proliferat ion) to a more differentiated state: (1) the rate of their differentia tion, determined by criterion of intense cytokeratin 8 expression, was increased; (2) steady-stale levels of beta(1) mRNA and expression of beta(1) subunit of integrins at the protein level were inhibited; (3) in contrast to large colonies in control cultures, the entire populati on of LT-2-treated large colonies contained beta(1) integrins distribu ted at cell-cell contacts. Raising extracellular Ca2+ concentration to 2 mM induced similar effects, suggesting that LT-2 may act by stimula ting an increase in intracellular levels of CA(2+). However, further s tudies will be needed to elucidate the molecular mechanisms underlying the stimulatory effect of LT-2 on proliferation of progenitors of uro thelial cells in the basal layer of the urothelium and subsequent diff erentiation of their progeny. We propose that these processes may have a causative role in the pathological changes that occur in the afterm ath of chronic or recurrent suburothelial infection in the urinary bla dder. (C) 1996 Wiley-Liss, Inc.