Contraction-Dependent Apoptosis of Normal Dermal Fibroblasts

Abstract

The mechanisms underlying the contraction-dependent apoptosis of primary fibroblasts are of prime importance in understanding anchorage-dependent survival/apoptosis of dermal fibroblasts. As integrins are essential extracellular matrix receptors in fibroblasts, their role in anchorage-dependent apoptosis/survival of fibroblasts was analyzed. Primary human fibroblasts displayed a marked reduction of apoptosis in mechanically relaxed collagen matrices in the presence of adhesion-blocking antibodies against alpha1beta1 or alpha2beta1. Anti-alphavbeta3 antibodies had a considerably weaker effect. In additional experiments RD cells, which lack alpha2 integrin, displayed no apoptosis in mechanically relaxed collagen matrices. Their susceptibility to apoptosis was restored after transfection with functional alpha2 integrin, and it could be blocked again by adhesion-blocking antibodies against alpha2beta1 integrin. Therefore we conclude that apoptosis of human primary fibroblasts in contractile collagen matrices is - at least in part - inhibited by adhesion-blocking anti-integrin antibodies, suggesting that the mode of apoptosis in this case is different from anoikis. Further, apoptosis in a mechanically relaxed collagen matrix could be abrogated by depolymerization of F-actin using cytochalasin D and also by disturbing actin-myosin interaction using 2,3-butanedione monoxime, indicating a possible dependence of apoptosis on mechanical forces and/or cell shape.

Collagen matrix as a tool in studying fibroblastic cell behavior

“…Antibodies to a2b1 integrins prevent the contraction and reduce apoptosis. [97][98][99] Integrin a11 mRNA and protein are up-regulated in attached collagen gel and down-regulated in fibroblasts grown in floating gel. 100 Rat liver MFB utilize a1b1 integrin for collagen matrix contraction as a2 subunit is not expressed in HSC, their precursors in vivo.…”

Mechanical control of tissue morphogenesis during embryological development

“…In fact, studies carried out with various types of cultured cells have confirmed that changes in the balance of mechanical forces between cells and the ECM control all of the key cell behaviors that are responsible for tissue development. For example, cells make entirely different fate decisions, such as whether to grow, differentiate or die (i.e., undergo programmed cell death or "apoptosis"), depending on the adhesivity or mechanical compliance of their ECM substrate and thus, the degree to which they physically extend (Folkman and Moscona, 1978, Ben-Ze'ev et al, 1980, Glowacki et al, 1983, Li et al, 1987, Ben-Ze'ev et al, 1988, Ingber and Folkman, 1989, Opas, 1989, Ingber, 1990, Mooney et al, 1992, Singhvi et al, 1994, Dike et al, 1999, Niland et al, 2001. This can be accomplished by varying the density of immobilized ECM molecules on otherwise non-adhesive dishes; changing the flexibility of ECM gels; or creating planar ECM islands with defined size and shape on the micrometer scale using microfabrication techniques (Fig.…”

Magnetic approaches to study collective three-dimensional cell mechanics in long-term cultures (invited)

“…For example, it has been found that increases in cell contractility and ECM stiffness promote cell proliferation 1,2 and assembly of focal adhesions, 3,4 whereas reduction in cell contractility and ECM stiffness induces cytoskeleton depolymerization 3 and apoptosis. 5,6 Several technical developments have enabled these recent insights into the role of mechanics in biology. These include the advent of two-dimensional (2D) substrates for cell culture that spans a range of physiologic stiffnesses 3,7 that can be used to apply force to cells, and whose deformations can be used to report cellular forces.…”