The Biodistribution of 99mTc Labelled Equine Peripheral Blood Mesenchymal Stem Cells in Healthy and Chronic Gingivostomatitis Cats

Feline chronic gingivostomatitis (FCGS) is a chronic inflammatory disease of the oral mucosa. Mesenchymal stem cell (MSC) treatments have been investigated as a potential treatment for this condition; however, the biodistribution profile of MSCs remains poorly understood. The goal of this study was to assess the relative pharmacokinetics of MSCs by comparing their biodistribution in healthy cats to that in cats suffering from FCGS. Two studies were performed to evaluate the biodistribution of radiolabelled equine peripheral blood-derived mesenchymal stem cells (ePB-MSCs) following intravenous and subcutaneous administration in healthy cats (n = 3) and in cats with FCGS (n = 4). Total body scintigraphic scans were obtained using a gamma camera. Free 99mTechnetium accumulation was primarily observed in the heart, lungs, stomach, bladder, thyroid, and salivary glands. Following intravenous administration of radiolabelled ePB-MSCs, increased radiopharmaceutical uptake (IRU) was mainly detected in the lungs, liver, kidneys, and bladder. After subcutaneous administration, IRU was predominantly observed at the injection site. In cats affected by FCGS, a higher radiotracer signal was observed in the rostral oral region following intravenous administration, with a mean 3.4-fold increase compared with healthy cats. The biodistribution pattern of radiolabelled ePB-MSCs differed from that of free 99mTechnetium. These findings provide preliminary information regarding the biodistribution of radiolabelled ePB-MSCs in cats.