Feline Mesenchymal Stem Cells

FCoV, FHV-1, and FPV Exhibit Sustained Proliferation and Replication within Fad-Mscs

Feline mesenchymal stem cells (fMSCs) have strong differentiation potential and have been widely used in feline immune-related disease studies. However, whether fMSCs are vulnerable to virus infection remains unknown. Ma et al. evaluated the susceptibility of feline adipose-derived (fAD-MSCs) and umbilical cord-derived mesenchymal stem cells (fUC-MSCs) to the common feline virus feline coronavirus (FCoV), feline herpesvirus type 1 (FHV-1), and feline panleukopenia virus (FPV).

FCoV, FPV, and FHV-1 were inoculated in fAD-MSCs and fUC-MSCs, with CRFK and F-81 as controls. FCoV and FHV-1 showed typical cytopathic effects (CPEs) in each cell line. After 48 h postinfection (hpi), the cells were observed under a microscope and presented grape-like changes, and the virus suspension was subjected to freeze‒thaw, filtration, and reinoculation up to the 10th generation with stable CPEs (Fig. 1a). FPV had no significant CPE in fUC-MSCs (Fig. 1b). The titers of the fifth-generation virus suspension were determined by the Reed-Muench method. The strains were named FCoV-YBYJ-2024, FPV-YBYJ-2024, and FHV-1-YBYJ-2024. They used IFA to analyze the FCoV, FHV-1, and FPV staining in fAD-MSCs, fUC-MSCs, CRFK, and F-81. After 48 h, the cells infected with FCoV and FHV-1 showed strong immunofluorescence signals, and cell morphology was well defined in fAD-MSCs, CRFK, and F-81 (Fig. 2a, c). FPV-infected fAD-MSCs, CRFK, and F-81 induced fluorescence, but fUC-MSCs did not, suggesting that FPV could not proliferate in fUC-MSCs (Fig. 2b).

Effect of bFGF on the Proliferation and Morphology of Feline MSC

Fujimoto et al. experiment demonstrated that bFGF could enhance the proliferative potential and change the cell shape of cat adipose-derived MSCs. Cat subcutaneous adipose tissue-derived MSCs were cultured in the presence or absence of bFGF.

Fig. 3 depicts an increase in the number of MSCs and alteration in the cell shape by bFGF. The cells maintained in the absence of bFGF were shown to increase in number with the passage. After a culture period of 5 days, the cells grew in size and transformed into a flat structure. On the other hand, MSCs in the presence of 100 ng/ml bFGF proliferated more and assumed various small elongated or round shapes. In contrast, they had flattened shapes in the absence of bFGF. This shape change in MSCs was maintained for about 4 days, and their shapes partly recovered to those of MSCs without bFGF by day 5 (Fig. 3). Fig. 4 illustrates that the proliferative potential of MSCs was dependent on the concentration of bFGF. The number of MSCs was significantly higher at 100 and 1000 ng/ml bFGF than in the absence of bFGF. However, at 1000 ng/ml bFGF, the growth of MSCs was unstable. It was shown to be retarded initially, and dead cells were present, but it accelerated after 3 days.