WST-1 proliferation assay. Cumulative population doubling was analyzed in different culture conditions, in FBS- and HS-containing medium, as well as in XF/SF medium with Coating Matrix Kit and with CELLstart™ coating at time points 1, 4, 7, and 11 day in two passages 2 (A) and 5 (B). The data in the diagrams are presented as mean ± SD. Significantly higher cumulative population doubling was observed in XF/SF conditions compared with HS/FBS cultures in passage 2 at 4-, 7-, and 11-day time points. Furthermore, statistically significant difference in population doubling were seen in passage 5 at 7- and 11-day time points between cells grown in XF/SF CM medium and FBS-containing medium.