The FoLu cell line was established from the lung tissue of an adult female grey fox (Urocyon cinereoargenteus). The cells are primarily used in virus studies and exhibit the typical characteristics associated with fibroblasts.

The FoLu line is susceptible to vesicular stomatitis, herpes simplex, and vaccinia viruses, but is resistant to poliovirus. FoLu cells are negative for reverse transcriptase, indicating their lack of integral retrovirus genomes. In culture the cells typically form monolayers that adhere to glass or plastic surfaces.

Traditionally scientists viewed fibroblasts in relatively narrow terms, often considering them to be akin to scaffolding for more important cells. However, most modern studies suggest that many of these cells, which are primarily found in connective tissue, can function in very specialized and important ways. Indeed, according to recent research, depending on the specific surface markers they possess, most fibroblasts can transform into either scar-producing myofibroblasts or into a variety of fat cells known as lipofibroblasts. A group of scientists at the University of Rochester Medical Center have identified the protein Thy-1 as a key marker of the cells' potential for development, those fibroblasts that express the protein possessing the capability of becoming myofibroblasts while those with no Thy-1 have the potential to become lipofibroblasts. Such research may eventually help lead to the development of pharmaceuticals that can impede the detrimental buildup of scar or adipose tissue.

The culture of fox lung fibroblast cells presented in the digital image above was labeled for the mitochondrial and filamentous actin networks with MitoTracker Deep Red 633 and Alexa Fluor 568 (red fluorescence) conjugated to phalloidin, respectively. DNA in the cell nucleus was counterstained with SYTOX Green. Images were recorded in grayscale with a 12-bit digital camera coupled to either a Nikon E-600 or Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles with the exception of MitoTracker Deep Red 633, which was pseudocolored yellow.

Fox Lung Cells with MitoTracker Deep Red 633, Alexa Fluor 488, and SYTOX Orange - A triplet of fluorophores was utilized to label the culture of FoLu cells illustrated in this section. Alexa Fluor 488 conjugated to phalloidin, MitoTracker Deep Red 633, and SYTOX Orange, enabled the visualization of F-actin, mitochondria, and cell nuclei, respectively.