Objective – To assess the efficiency of gravity filtration to enrich equine bone marrow for blood component recovery, stem cell recovery and replication, and progenitor cell differentiation.
Animal – 12 healthy adult horses
Procedures – Bone marrow aspirates were collected from the fifth sternebral body and filtered by gravitational flow to capture, and release, marrow elements. Raw, filtered, and harvested bone marrow were evaluated for white blood cell and platelet counts, automated and cytomorphologic cell differentials, bone marrow-derived mesenchymal stem cell colony forming units, cell viability by flow-cytometry, and differentiation capacity. Isolated marrow mesenchymal stromal cells were analyzed for CD90 and MHC class I and II antigens.
Results - Eleven of fourteen marrow aspirates (79%) successfully produced filtered marrow and 100% of filtered marrow produced a harvested marrow product. Mean cell viability of harvested marrow was 95.9%. Total white blood cells and platelets were efficiently captured by the filter (> 95%), but recovery in harvested marrow was a mean of 30%. Cytologic cell differentials indicated that neutrophils (%) were significantly less (P<0.05) and the progenitor cell population 1.56-fold greater in the harvested marrow compared to raw marrow. Flow cytometry and culture characterized harvested marrow cells as CD90+, MHCI-, and MHCII- indicating a stem cell phenotype that were multipotent and differentiated into chondrocytes, osteocytes, adipocytes, and tenocytes.
Conclusions and Clinical Relevance – Gravitational filtration of bone marrow efficiently captured platelets and cells and significantly enriched a viable progenitor/stem cell population while decreasing the neutrophil population. Filter modifications are anticipated to improve efficiency of cell harvest.