Variation in collagen expression by cloned periodontal ligament cells

Isolation in vitro of clonal populations of fibroblasts from enzyme digested porcine periodontal ligament (PL) has made possible the comparison of collagen synthesis between single colonies of cells. Despite low cloning efficiencies, two independent PL isolations yielded enough clones for detailed analysis. In the first group of clones, the amount of 14 C‐labelled collagen synthesized compared to the total protein synthesis varied from 32% to 47%, whereas the values from the second group, with one exception, ranged from 55% to 70%. Each clone synthesized types I, III, and V collagens. However, the relative amounts of these collagens varied from one clone to another in both groups: i. e. the type III collagen synthesis ranged from 10% to 32% of the total collagen in most clones. A single clonal population produced type I collagen almost exclusively and in another collagen synthesis was barely detectable. These results indicate that primary cultures of PL cells contain a heterogenous mixture of cells that not only synthesize different levels of collagen but produce distinctly different ratios of collagen types. These findings further suggest that the PL contains distinct populations of fibroblast‐like cells.