2.5. Lactate Dehydrogenase (LDH) Assay

The viral cytotoxicity in cAdMSCs was quantitatively assessed by LDH viability (Pierce LDH cytotoxicity Assay kit, Thermo Scientific, Dreieich, Germany) which is based on detecting lactate dehydrogenase released from damaged cells. For this purpose, cAdMSCs seeded in 24–well plates were infected with C1-opt1, W1-opt1, or L3-opt1 vaccinia virus strains at a MOI of 0.5. After one hour of incubation at 37 °C, the infection medium was removed and replaced by fresh growth medium. After 3 h, 24 h, 48 h, 72 h, and 96 h, cell-free supernatant aliquots were collected from each experimental sample and LDH in the culture supernatants was measured using the Pierce LDH Cytotoxicity Assay Kit, following the manufacturer’s instructions. These measurements were performed with Tecan Sunrise Remote microplate reader (Tecan, Maennedorf, Switzerland) at wavelengths of 490 nm and 680 nm. The results were shown as fractions of LDH release. Data were presented as mean standard deviation (SD), n = 3.