Feline chronic gingivostomatitis (FCGS) is a poorly defined disease characterized by severe inflammation of the mouth and gum that is painful and debilitating. Treatment involves a combination of antibiotics, anti-inflammatory drugs (corticosteroids), pain medications and full‐mouth tooth extractions and such treatments are not always 100% effective. Subsequently, there are significant potential complications that can affect the cat’s quality of life. Stem cell therapy has been used in both human and veterinary medicine for a variety of inflammatory diseases. One form of stem cell therapy uses stem cells called fat-derived mesenchymal stem cells (adMSC). The researchers have used this therapy to decrease inflammation and effectively cure FCGS in cats. However, 60-75% of older cats are infected with feline syncytium forming virus (FeSFV). While this virus does not directly cause disease or impact the quality of life for infected cats, this virus inhibits culture of adMSCs. Two cats enrolled in their previous study were unable to be treated with their own adMSCs due to the inability to culture FeSFV+ cells. In this proposal, they will use adMSCs generated from a small amount of fat collected from healthy FeSFV- donor cats to treat FeSFV+ cats with FCGS. Further, the goal will be to determine the safety and efficacy of donor-derived adMSCs to treat cats with FCGS. If the proposed stem cell treatment proves to be beneficial, it will revolutionize the treatment options for cats with FCGS.