Best Approach for Harvesting Bone Marrow to Maximize TNC and CD34+ Cell Counts

Background: Bone marrow (BM) has been utilized as a source of stem cells for transplantation for many years. Although the use of BM has decreased with the advent of mobilized stem cells, utilization is increasing once again due to the lower rate of chronic GVHD associated with BM as a stem cell source. There is no generally accepted technique for harvesting BM. Protocols vary both in relation to the volume of each aspirate, the number of aspirates performed at each puncture site and the total volume of harvests.

Method: BM was collected from the posterior iliac crests (PIC) in 2 separate bags: 10ml aspirates from the left and 20 ml aspirates from the right. Samples taken at the start and after 100, 150, 200, 250, & 500 ml were analyzed for TNC, CD34⁺ and CD3⁺ cell counts.

Results: The following table shows cell number (mean ± SEM ×10⁶) for the parameters indicated.

There is a rapid fall in the yield of CD34⁺ cells obtained with increasing harvest volume (19 and 25% of the initial number after 250 ml for 10 and 20 ml aspirates respectively; 14 and 11% respectively after 500 ml). In contrast the CD3⁺ cell numbers fall more slowly (43 and 50% after 250 ml, 45 and 38% after 500 ml). By the time 500 ml has been aspirated, there is no difference in the total number of CD34⁺ cells obtained from a 10 ml versus a 20 ml aspirate of bone marrow.

Conclusion: CD34⁺ cell yields fall rapidly when BM is harvested along the PIC. Using additional areas such as the anterior iliac crests may be preferable to a large volume PIC harvest for optimizing CD34⁺ stem cell collection. After 500 ml of BM has been harvested, 20 ml BM aspirates do not increase CD34⁺ cell numbers and 10 ml aspirates should be taken to minimize unnecessary blood loss and reduce T cell contamination.