Long-term production of human platelets in NOD/SCID mice after transplantation of CD34+ cells. (A) Representative flow cytometric analysis of PB cells from mice transplanted with no (i) or 3 × 106 CD34+ (ii-iii) cells at the indicated times after transplantation. Murine and human platelets are found in the bottom right and top left quadrant, respectively. Human platelets represented 32.2% (ii) and 8.9% (iii) of the total platelet population 2 and 8 weeks after transplantation, respectively. (B) Time course of human platelet production in NOD/SCID mice after transplantation of 3 × 106 (green), 1 × 106 (blue), 0.5 × 106 (black), or no (orange) CD34+ cells. Human platelets were detected from day 10 for 3 × 106 CD34+ cell-injected mice and week 2 onward for the other 2 transplanted mouse groups. Data show the average number of human platelets detected per microliter of PB ± SEM (n ≥ 3 at all time points assayed). Unpaired Student t test was used to determine statistical differences of human platelet production between mice transplanted with 3 × 106 versus 0.5 × 106 (green asterisks) or 1 × 106 (blue asterisk) CD34+ cells. ***P < .001; *P < .05. (C) Mouse platelet counts in NOD/SCID mice after sublethal whole body irradiation (300 cGy) and after transplantation of 3 × 106 (green), 1 × 106 (blue), 0.5 × 106 (black), or no (orange) CD34+ cells. Data represent mean ± SEM (n ≥ 3 at all time points assayed). Exact human and murine platelet counts are given in supplemental Table 1.
