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 wide variety of manipulations ranging from studies employing gene transfection to microinjection. Fibroblasts within tissues are exposed to a dynamic mechnical environment, which influences the structural integrity of both healthy and healing soft tissue. 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 parts of the body are intrinsically different and display different regulatory functions on surrounding cells. For example, splenic fibroblasts have been shown to regulate the development of NK cells from blood progenitors through the expression of bioactive IL-15. HSF from ScienCell Research Laboratories are isolated from human spleen tissue. HSF are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 105 cells in 1 ml volume. HSF are characterized by their spindle morphology and immunofluorescence with antibodies specific to fibronectin. HSF are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HSF 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 the culturing of HSF in vitro.