Efficacy of Mesenchymal Stem Cell Enriched Grafts in an Ovine Posterolateral Lumbar Spine Model

Abstract

Four groups of 6 animals underwent single-level noninstrumented posterolateral lumbar fusion (PLF) with one of the following grafts: 1) autograft, 2) cell-enriched beta-tricalcium phosphate (TCP), 3) TCP with whole bone marrow, and 4) TCP alone. Plain radiographs were taken after surgery and at death, 6 months after surgery. Explanted spine segments were analyzed by manual palpation, micro-CT, and histology. A sheep spine fusion study was undertaken to evaluate the healing performance of a TCP graft enriched with osteoprogenitor cells using Selective Cell Retention technology (SCR), compared with autograft, TCP with whole bone marrow, and TCP alone. Improved bone healing with previously demonstrated using grafts enriched in osteoprogenitor cells. Cell-enriched grafts were obtained by processing 30 mL of bone marrow through 10 mL of TCP. TCP was also used either saturated with bone marrow or alone. At 6 months, 33% of the SCR-enriched TCP and 25% of the autograft sites were fused, compared with 8% of the TCP plus whole bone marrow and 0% of the TCP alone. Histology of fused samples showed denser bone formation in the SCR-enriched TCP grafts than in the autograft sites. The use of SCR-enriched TCP and autograft resulted in similar fusion rates in an ovine posterolateral noninstrumented lumbar spine fusion model.