Found in the extracellular matrix component of blood vessel walls and in the cytoplasm of cultured human aortic smooth muscle. Highly expressed in lymph node, jejunum, pancreas, stomach, trachea, testis, uterus and placenta; moderately expressed in brain, colon, lung, prostate, spinal cord, salivary gland and vascular smooth-muscle cells and very weakly expressed in heart, liver, kidney, bone marrow, spleen, thymus, skeletal muscle, adrenal gland and peripheral leukocytes. Expression in heart was higher in the right ventricle and atrium than in the left ventricle and atrium. Highest expression observed at the fetal stage. Expressed by smooth-muscle cells in the artery wall in a PDGF-dependent way. Stimulated by PDGF/platelet-derived growth factor. Belongs to the fibril-associated collagens with interrupted helices (FACIT) family.