Fibroblast progenitor cells of the embryonic chick limb.

A population of mesenchymal cells derived from the stage-25 chick wing tip gives rise to progeny of a similar morphology and to authentic fibroblasts when grown in low density culture. Mixed clones containing both cell types are often observed. As the more rapidly proliferating fibroblasts begin to predominate in these cultures, collagen biosynthesis rises from the basal mesenchymal level to a level characteristic of mature fibroblasts. The fibroblast progenitor is discussed relative to the other cell types of the mesodermal lineage of the developing limb.