Rapid onset of apoptosis in vitro follows disruption of β1- integrin/matrix interactions in human colonic crypt cells

Abstract

Background and Aims: Apoptosis by loss of adherence is a recently described phenomenon termed 'anoikis.' β1 integrins are heterodimeric surface molecules mediating adhesion to the extracellular matrix. The aim of this study was to address whether anoikis accounts for the elimination of senescent enterocytes and, if so, whether β1 integrins are involved. Methods: Whole crypts were isolated from normal human colonic mucosa and examined in vitro. Results: The vast majority of cells in resuspended crypts rapidly underwent apoptosis within 4 hours. Apoptosis was partially inhibited when cells had contact with collagen I-coated membranes or when whole crypts were embedded in a collagen gel. Preincubation of crypts with an inhibiting anti-β1 antibody before readhesion caused a much higher apoptotic rate. Confocal microscopy of embedded crypts revealed two critical zones of high sensitivity to temporary loss of adherence: the base of the crypts where stem cells are supposed to reside and the crypt mouth including the surface epithelium. Conclusions: Survival of colonic epithelia crucially depends on matrix adhesion and is likely to be guaranteed by β1-integrin/matrix interaction. The data strongly suggest that anoikis is the way senescent colon cells die.