Abstract 1002: Perinatal Mortality Following Smooth Muscle Cell-Restricted Deletion of Integrin-Linked Kinase
Integrin-linked kinase (ILK) is a serine/threonine protein kinase that interacts with β integrins. While ILK has been implicated in cell-matrix interactions and cell survival in several cell types, its role in smooth muscle cell (SMC) biology remains poorly understood. Here we used Cre-loxP technology to elucidate the function of ILK in vascular SMCs in vivo. Conditionally targeted ILKflox/flox mice were intercrossed with SM22-Cre mice expressing Cre-recombinase under the transcriptional control of the smooth muscle-restricted 2.8-kb SM22-α promoter, which is also transiently expressed in cardiac myocytes. SM22-Cre+/ILKflox/flox embryos were present at expected frequencies at E18.5, but these pups die within 1–2 hours after parturition, and no SM22-Cre+/ILKflox/flox mice were present among 127 viable offspring (p<0.001 by X2). Preliminary analyses have revealed no gross defects in cardiac or pulmonary morphogenesis, suggesting the possibility of SMC-dependent vascular defects as the cause of perinatal mortality. To begin to elucidate the mechanisms responsible, we isolated primary aortic smooth muscle cells from ILKflox/flox mice and transduced them with a recombinant adenovirus encoding Cre recombinase (AdCre). In striking contrast to prior studies in other cell types, targeted ex vivo deletion of ILK by AdCre had no effect on overall SMC morphology or focal adhesions, and SMC chemotaxis in a Boyden chamber was unaffected by ILK deletion. Transduction of SMC from ILKflox/flox mice with AdCre also had no effect on apoptosis, as assessed by both cell death ELISA and western blotting for activated caspase- 3. Thus, deletion of ILK in SMC ex-vivo does not appear to cause changes in cell-matrix interactions or cell survival, which is in marked contrast to findings in endothelial cells and leukocytes. Further investigation into the function of ILK, both in SMC and in cardiac myocytes, promises to yield important insights into the molecular mechanisms regulating late cardiovascular development.