Fibroblasts are mesenchymal cells derived from the embryonic mesoderm. They have been extensively used for a wide range of cellular and molecular studies as they are one of easiest types of cells to grow in culture. Their durability also makes them amenable to a variety of manipulations ranging from studies employing gene transfection to microinjection. In general, fibroblasts secrete a non-rigid extracellular matrix which is rich in type I and/or type III collagen. There is evidence showing that fibroblasts in different organs are intrinsically different. Dermal fibroblasts switch from a proliferative, migratory phase to a contractile, matrix-remodeling phase during wound healing. In addition, they secrete large quantities of hyaluronan in response to inflammatory stimuli. RDF-a from ScienCell Research Laboratories are isolated from adult rat skin. RDF-a are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 10^5 cells in 1 ml volume. RDF-a are characterized by immunofluorescence with antibody specific to fibronectin. RDF-a are negative for mycoplasma, bacteria, yeast, and fungi. RDF-a are guaranteed to further expand for 5 population doublings under the conditions provided by ScienCell Research Laboratories. Recommended medium: It is recommended to use Fibroblast Medium-2 (FM-2, Cat. #2331) for culturing RDF-a in vitro.