Time-dependent migration of CD34⁺ cells into spheroids.

<p>At defined intervals, cells in the supernatant were collected and spheroids were harvested and trypsinized. (A) The proportion of CD34⁺ cells (R2) was determined by flow cytometry, and calculated as percentages of CD34⁺ cells inside the spheroids in relation to the total plated. (B) Dot plot of control spheroids without hematopoietic cells. (C) To distinguish migration from proliferation of cells inside the spheroids, hematopoietic cells were removed after 24 hours of co-culture, and the spheroids were maintained in culture for up to 48 hours. The number of CD34⁺ events inside the washed spheroids (closed symbols) was compared to the number of CD34⁺ events inside no washed spheroids (open symbols). (D) Time-dependent migration of CB CD34⁺ cells into simple non-induced (full line, dots), simple osteo-induced (dotted line, triangles), and mixed (dotted line, circles) spheroids. (E) The migratory profile of BM (closed squares) and CB (open squares) CD34⁺ cells in mixed spheroids is shown. Data are mean ± SEM.