Extracellular matrix-specific induction of elastogenic differentiation and maintenance of phenotypic stability in bovine ligament fibroblasts.

Abstract

We studied the process of elastogenic differentiation in the bovine ligamentum nuchae to assess the mechanisms that regulate elastin gene expression during development . Undifferentiated (nonelastin-producing) ligament cells from early gestation animals initiate elastin synthesis when grown on an extracellular matrix (ECM) substratum prepared from late gestation ligamentum nuchae . ECM from ligaments of fetal calves younger than the time when elastin production occurs spontaneously in situ (i.e., beginning the last developmental trimester at -180 d of gestation) does not stimulate elastin production in undifferentiated cells . Matrixinduced differentiation requires direct cell matrix interaction, is dependent upon cell proliferation after cell-matrix contact, and can be blocked selectively by incorporation of bromodeoxyuridine into the DNA of undifferentiated cells before (but not after) contact with inducing matrix . Quantitative analysis of elastin synthesis in young cells after matrix-induced differentiation indicates that the entire cell population is competent to respond to the matrix inducer, and continued synthesis of elastin after young cells are removed from the ECM substratum indicates that the phenotypic transition to elastin synthesis is stable and heritable . Although ligament cells do not require continuous contact with ECM to express the elastin phenotype, elastin synthesis is increased substantially when elastin-producing cells are grown on ligament matrix, suggesting that elastogenic differentiation is stabilized by ECM . The matrix substratum was also found to alter the distribution of tropoelastin between the medium and matrix cell layer . When grown on tissue culture plastic, ligament cells secrete >80% of newly synthesized tropoelastin into the culture medium . When cultured on ECM, however, 50-70% of the newly synthesized tropoelastin remains associated with the cell layer and is cross-linked to form insoluble elastin as shown by the incorporation of radiolabeled lysine into desmosine .

Interaction of Tropoelastin with the Amino-terminal Domains of Fibrillin-1 and Fibrillin-2 Suggests a Role for the Fibrillins in Elastic Fiber Assembly

“…Immunoprecipitation studies found that tropoelastin in the medium did not co-precipitate with fibrillin, although both proteins were secreted at high levels (32). When the FCL cells were grown on a slice of elastic ligament, tropoelastin readily associated with the matrix and was incorporated into the existing fibers (33). These findings suggest that the presence of an insoluble matrix "surface" containing assembled elastic fiber proteins was sufficient to reinitiate the assembly process, perhaps through the mechanism described above.…”

Cell-Cell Communication in the Tumor Microenvironment, Carcinogenesis, and Anticancer Treatment

“…It has long been known that the ECM is essential for cellular differentiation [176]. The ECM directly influences the differentiation of many cell types, as well as stabilizing ligament fibroblasts [177]. Moreover, only about 50% of patients with disseminated tumor cells and circulating tumor cells (CTCs) develop clinically evident metastatic cancer; only 0.01% of those with disseminated cells and CTCs develop metastasis [178,179].…”

Inducible adhesion of mesenchymal cells to elastic fibers: elastonectin.

“…Elastin peptides were also shown to be able to interact with several other cell types (9, 10). Mecham et al (11) studied the acquisition of chemotactic responsiveness to elastin peptides and the expression of the elastin phenotype by fetal bovine ligamentum fibroblasts during cell differentiation and showed that they were closely related events. Therefore, the investigation of whether specific protein(s) could mediate the adhesion of mesenchymal cells to elastic fibers was undertaken.…”