All samples presented cells essentially at the scaffold��s surface at the initial time (data not shown). After 3 and 7 d, the fibrous and porous matrix of scaffolds facilitated cell migration and samples exhibited cell nuclei in the 100-��m superficial layers for all culture conditions (data Vandetanib not shown). From 7 to 21 d of culture, the nuclei distribution inside the scaffolds varied significantly with culture conditions. Under static conditions, STRO-1A cells proliferated mainly at the periphery of samples and a monolayer of cell nuclei could be visualized on the scaffold surface after 21 d (Fig. 4A). Few cell nuclei were observed in the samples submitted to low flow-rate conditions (Fig. 4B) although a successful scaffold colonization was noted inside samples submitted to high flow-rate (Fig.

4C). The application of a high flow-rate also permitted cell proliferation in the center of the material while under low flow-rate, the proliferation process was not homogeneous inside the scaffolds. Cells proliferated more easily in the peripheral regions (Fig. 4E) than in the central ones (Fig. 4D). In order to interpret this behavior, a scheme of the liquid flow in the bioreactor was drawn (Fig. 4F). Figure 4. HA-Col scaffold colonization under different culture conditions after 21 d (A, B and C). Heterogeneity of colonization at the central (D) and peripheral regions (E) of HA-Col scaffolds under low flow-rate conditions. Scheme of fluid … Cell viability Using the MTT assay, some significant differences in cell viability between the culture conditions were observed (Fig.

5A). Up to 7 d, an increase in the number of viable cells appeared in all conditions especially for both dynamic flow-rates. However, the cell viability decreased drastically from 7 d to 3 weeks under static and dynamic low-flow-rate culture conditions. Under high flow-rate conditions, the cells continued to proliferate and presented significantly higher cell viability at 14 and 21 d when compared with static and low flow-rate conditions (Fig. 5A). Figure 5. (A) Number of STRO-1A cells cultured on HA-Col scaffold under different conditions up to 21 d; (B) Number of STRO-1A cells cultured up to 21 d on HA-Col scaffold at different positions within the bioreactor under low and (C) high flow-rate. … The number of viable cells was also analyzed considering the sample position in the bioreactor (Figs.

5B,C). When cells were submitted to low flow-rate conditions, sample position was shown to have an important role in the initial culture times (Fig. 5B). A significantly higher viable cell number was measured at positions 1 and 3 than at position 2 after 1 d of Dacomitinib culture. After 3 d, only position 1 presented a higher viable cell number (Fig. 5B). No more differences between positions were observed from 7 to 21 d. In contrast, few significant differences between positions were observed under high flow-rate conditions (Fig. 5C).