Dynamic Expression of alf 13 and a 2 f 31 Integrin Receptors by Human Vascular Smooth Muscle Cells a 2 1 Integrin Is Required for Chemotaxis Across Type I Collagen-Coated Membranes

Vascularsmooth muscle ceUs (SMCs) in the media ofnormal arteries express at (31 integrin with no detectable cv2.(1 as determined by immunocytochemistry. In contrast, immunoprecipitation of integrins expressed by human SMCs cultured from medial explants shows strong expression of v2j13 and no expression of al (31. the apparent reciprocal expression of these two collagen and laminin receptors was confirmedbyflow cytomettic analysis offluorescent labeled cells. Freshly isolated SMCs had detectable ail, a3, a5, and av subunits with low levels of detectable 183 and no detectable a2. Cultured SMCs expressed a2, cw3, a5 and oa subunits with little or no a) or (33. Neither a4 nor a6 were detectable infreshly isolated or cultured ceUs. Expression of cr2811 receptors by cultured SMCs appears to be requiredfor the migration ofthese ceUs on type IcoUagenL Migration ofcultured SMCs across a type I coUagen-coated membrane toward two different chemotactic stimuli, platelet-derived growth factor-BB (1 nmol/L) and insulin-like growth factor-(1 nmol/ L), was Mg2" dependent and inhibited by preincubation of ceUs with an affinity-purified polyclonal anti-aO)(1 antibody or by monoclonal antibodies directed against the individual a2 or (31 subunits. Attachment to type I coUagen membranes was not affected by antibodies under conditions where migration was significantly impeded. The combined data show that SMC expression of al (31 and a2.31 integrin receptors for collagen and laminin is dynamic and reciprocal and may be important with respect to SMC migration on type I coUagen. Thesefindings are potentialy important in understanding thepathophysiology of vascular diseases, for example, atherosclerosis and restenosisfolowing balloon angioplasty, where SMC migration is a contributingfactor. (AmJPathol 1994, 145:1070-1081)