Bone marrow characterization in sickle cell disease: inflammation and stress erythropoiesis lead to suboptimal CD34 recovery.

Stress erythropoiesis and chronic inflammation in subjects with sickle cell disease (SCD) may have an impact on the bone marrow (BM) haematopoietic stem and progenitor cell (HSPC) quality and yield necessary for effective autologous, ex vivo HSPC gene therapy. BM from 19 subjects with SCD and five volunteers without SCD (non-SCD) was collected in different anticoagulants and processed immediately (day 0) or the following day (day 1). Inflammatory, contamination and aggregation markers within the mononuclear layer, and CD34, CD45 and Glycophorin-A (GPA) expression on HSPCs after CD34 selection were analysed by conventional and imaging flow cytometry. Compared to non-SCD BM, multiple markers of inflammation, contamination (red cells, P < 0·01; platelets, P < 0·01) and aggregates (platelet/granulocytes, P < 0·01; mononuclear/red cells, P < 0·01) were higher in SCD BM. Total CD34 cell count was lower in SCD BM (P < 0·05), however CD34 count was higher in SCD BM when collected in acid citrate dextrose-A (ACDA) versus heparin (P < 0·05). Greater than 50% of CD34 HSPCs from SCD BM are CD34 due to higher erythroid lineage expression (P < 0·01) as single cell CD34 CD45 GPA (P < 0·01) and CD34 CD45 GPA (P < 0·01) HSPCs. SCD BM is characterized by increased inflammation, aggregation and contamination contributing to significant differences in HSPC quality and yield compared to non-SCD BM.