Fibroblasts are the principal cells of connective tissue, which is distributed widely throughout the body and functions chiefly in providing structural support and protection. Similar to other connective tissue cells, fibroblasts develop in embryos from the mesenchyme, a network of loosely packed, unspecialized cells that have the potential to differentiate in several different ways. Fibroblasts are extremely important for wound healing since they produce tropocollagen, the precursor of collagen. The cells also typically produce glycosaminoglycans, fibers, and glycoproteins, which together comprise the extracellular matrix of connective tissue. Large and flat, fibroblasts usually exhibit branched cytoplasm and an elliptical, flat nucleus with one or more nucleoli.

The UMNSAH/DF-1 cell culture presented in the digital image above was labeled for mitochondria and the cytoskeletal filamentous actin network with MitoTracker Red CMXRos and Alexa Fluor 488 conjugated to phalloidin, respectively. In addition, the ultraviolet-absorbing probe DAPI was utilized to target nuclear DNA. Images were recorded in grayscale with a QImaging Retiga Fast-EXi camera system coupled to an Olympus BX-51 microscope equipped with bandpass emission fluorescence filter optical blocks provided by Omega Optical. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.