A double-label immunofluorescence technique was used to determine whether all normal fibroblast-like cells cultured from porcine connective tissues simultaneously express both type I collagen and fibronectin (FN). Cells surrounding explants in primary cultures from gingival and periodontal ligament (PL) tissue were heterogeneous in the expression of collagen and FN. Mass population cells at first and second subculture after primary explanting of gingival tissue were also heterogeneous in the expression of collagen and FN. When clonal populations were analyzed, four distinct phenotypes were observed: Coll+/FN+;Coll+/FN-;Coll-/FN+;Coll-/FN-. Mass populations of PL cells were more homogeneous than gingival fibroblasts and when clones were analyzed only two phenotypes were observed. These data suggest that normal fibroblast-like cells in vitro are capable of expressing collagen and FN independently and that FN-negative cells may utilize a FN-independent attachment mechanism in culture.

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