Figure 3: Proliferation behavior of SC subpopulations.

(a) Light microscopy of proliferating SC isolated from SM muscles. Scale bar represents 50 μm. At day 4 of cultivation, slightly elongated, well-defined cells (◄) are found in P40/50 and P50/70 cultures. Additionally, in P40/50 cultures, slightly flattened cells can be seen (*). At day 8 of cultivation, the P40/50 subpopulation clearly shows a higher cell density reflecting an increased proliferation rate. After 14 days, morphology and density show greater similarity between the two subpopulations. (b) Proliferation rate of SC isolated from LD muscles was calculated by using cell numbers determined after passaging. Proliferation of P50/70 cells was considerably lower compared with that of P40/50 cells during the first 8 days of culture but achieved a comparable level after 14 days of cultivation. Bars represent mean ± SD, n = 3. For statistical analysis, Students t-test was performed, *p ≤ 0.05. (c) SC from LD muscles of 4-day-old piglets were isolated, and the growth kinetics of P40/50 (grey) and P50/70 (black) cells were monitored starting 4 days after isolation by using the xCELLigence system. Shown original growth curves represent mean of quadruplicates of one representative experiment ± SD, results were reproducible. Proliferation assay (5,000 cells/well) was performed and the medium was exchanged at given time point (←). The doubling time (DT) obtained during the logarithmic growth phase is presented. Cells of the P40/50 population exhibit superior growth kinetics showing faster proliferation.