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 the 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 various 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. HDF-f from ScienCell Research Laboratories are isolated from fetal human skin. HDF-f are cryopreserved at passage one and delivered frozen. Each vial contains > 5 x 105 cells in 1 ml volume. HDF-f are characterized by their spindle morphology and immunofluorescence with antibody specific to fibronectin. HDF-f are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast, and fungi. HDF-f are guaranteed to further expand for 15 population doublings under the conditions provided by ScienCell Research Laboratories Recommended Medium It is recommended to use Fibroblast Medium (FM, Cat. #2301) for culturing HDF-f in vitro.