Cells obtained through LTC-IC are the most primitive cells that can be analyzed by in vitro functional assays.
LTC-IC absolute counts with LDA were evaluated as described previously (10-12).
Only 60% of the MethoCult GF+ cultures obtained from CAFC of LTC-IC gave rise to HPP-Q (High Proliferative Potential-Quiescent) colonies, while all cultures had BFU-E, GM and GEMM colonies by day 14, as shown in Figure 2.
LTC-IC counts from CD34+ selected cord blood cells (range: 1261-2906, mean: 1966[+ or -]808) Samples LTC-IC/CD34+ cells 1 2705 2 2906 3 2580 4 1649 5 1781 6 1280 1649 8 2499 9 1350 10 1261 Mean Value 1966 [+ or -] 808
Although the number of articles on cord blood LTC-IC are somewhat limited, our LTC-IC/CD34+ cell numbers were lower compared to some of the published studies (13), (14), but results of several studies were consistent with ours (15).
LTC-IC assay with limiting dilution is relatively easier than the other LTC-IC assays, since the preprepared murine bone marrow stromal cell line plates can be used in five weeks, and counting CFUs is easier than counting CAFCs.
The role of LTC-IC in long-term engraftment is unknown; however, they are the most primitive progenitors that can be detected in an in vitro assay.
A recent study reported that type of stromal feeder layer used in LTC-IC LDA affects the determination of LTC-IC frequencies in uncultured cells and also has a significant effect on cultures.
The temperature of the LTC-IC was kept at 35[degrees]C in our study.
Even though there has been some progress in the standardization of the LTC-IC culture methods, a more standardized approach will help us to achieve better results for ex vivo expansion of hematopoietic cells.