Clusterin (Apo J) regulates vascular smooth muscle cell differentiation invitro

Previously we reported a significant and substantial increase in the synthe sis and secretion of clusterin in cultured porcine vascular smooth muscle c ells (VSMC) during the time when the VSMC culture modulates from a prolifer ating monolayer morphology to a nodular cell culture morphology. That in vi tro process appears to recapitulate some aspects of in vivo Vascular remode ling in response to injury and is facilitated by the presence of a well-dev eloped extracellular matrix. To directly test the hypothesis that clusterin regulates VSMC phenotypic modulation, cultured VSMC were stably transfecte d With an expression plasmid containing the full-length murine clusterin se quence in antisense orientation. Twenty-four clones were selected on the ba sis of neomycin resistance and characterized for clusterin expression and c ulture morphology. In contrast to clone SM-CLU18AS, which expresses a high level of clusterin and forms multicellular nodules, clone SM-CLU13AS expres ses a low level of clusterin and does not form nodules even in the presence of a preformed collagen gel. Importantly, clusterin-negative SM-CLU13AS re tains the ability to form nodules in an environment containing exogenous cl usterin. SM-CLU13AS forms nodules when cultured in Matrigel (Wh ich contain s clusterin) and in the presence of clusterin-containing conditioned media prepared from nodular SMC cultures or SM-CLU18AS cultures. These results de monstrate that clusterin is required for VSMC nodule formation and suggest that it may play a role in smooth muscle cell reorganization in the vascula r wall. (C) 1999 Wiley-Liss, Inc.