Processing of equine bone marrow using the automated MarrowXpress System: RBC depletion, volume reduction, and mononuclear cell recovery

Background The therapeutic use of bone marrow-derived mononuclear cells (MNCs) and mesenchymal stem cells for the treatment of soft tissue and orthopedic injuries in equine patients is expanding. After collection, bone marrow must be reduced in volume and depleted of RBCs for immediate therapeutic use or to prepare cells for culture or cryopreservation and storage. The MarrowXpress (MXP) System is an automated, closed, sterile system designed to process human bone marrow samples. Objectives The purpose of this study was to evaluate the capacity of the MXP System to process equine bone marrow to reduce volume, deplete RBCs, and enhance recovery of MNCs. Methods Bone marrow was collected from 47 horses into 2 60-mL syringes containing heparin and processed using the MXP System. HCT, total nucleated cell (TNC) count, and MNC count were obtained for each sample before and after processing using an Advia 120 hematology analyzer. Volume reduction, RBC depletion, and recovery of TNCs and MNCs were calculated. Results For equine bone marrow samples, mean values were 73.2% for RBC depletion and 78.0% for volume reduction. TNC count before processing was 2.5 ± 1.2 × 107 and after processing was significantly higher at 7.8 ± 3.3 × 107 (P < .0001), with a recovery of 68.5 ± 24.5% (mean ± SD). MNC count before processing was 1.1 ± 0.9 × 107 and after processing was significantly higher at 3.8 ± 1.9 × 107 (P < .0001), with a recovery 73.0 ± 31.5%. Conclusions The MXP System can reliably reduce volume and deplete RBCs from aspirates of equine bone marrow aspirates. MNCs can be recovered in a reproducible and sterile manner. Further studies evaluating the effects of the MXP System on cell viability, identification of mesenchymal stem cells (MSCs), and the efficacy of MSC expansion are warranted.