516 - Multipotential Stromal Cell Numbers and Potency in Cellular Allograft...

#516 Multipotential Stromal Cell Numbers and Potency in Cellular Allograft Bone: Comparison with Fresh Age-matched Autograft Bone and Bone Marrow Aspirate

Stem Cell Technologies

Poster Presented by: T.A. Moseley

Author(s):

S.A. Boxall (1)
T. Baboolal (1)
T.A. Moseley (2)
R. Cuthbert (1)
P.V. Giannoudis (1)
D. McGonagle (1)
E. Jones (1)

(1) Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, United Kingdom
(2) NuVasive, Inc., Biologics Research & Development, San Diego, CA, United States

Abstract

Background: Spinal arthrodeses rely on the use of autograft bone or bone graft substitutes to bridge vertebrae. The aim of this study was to investigate the presence of pre-osteoblast, multipotential stromal cells (MSCs) in a clinically-used bone allograft material (Osteocel Plus) and to compare their abundance with freshly collected, bone marrow aspirates (BMA) and autograft bone.

Methods: Scanning electron microscopy was used to visualise cells in situ. A novel flow cytometric technique was developed to enumerate MSCs and hematopoietic-lineage cells (HLCs) following their enzymatic removal from bone. Whole genome microarrays were utilized to characterize the allograft-resident cells in comparison with osteoblasts and fibroblasts.

Results: The surface of the allograft contained viable stromal cells capable of growing on-bone and migrating out to form plastic-adherent cultures. Compared to BMA or autograft bone, in which CD271bright MSC frequency was only 0.023% and 0.25% of total live cells, respectively, the cellular component of the allograft was highly enriched for MSCs (average CD271bright MSC frequency 37%). Cell lysates freshly-extracted from the allograft had a molecular signature consistent with MSCs and osteoblasts including the expression of osteogenic transcription factors, bone matrix proteins and bone morphogenetic proteins. The MSC identity of cellular allograft-resident stromal cells was confirmed following standard culture-expansion and differentiation.

Conclusions: The presence of highly-pure, bone-anchored and living MSCs represents a unique feature of the Osteocel Plus allograft material. Viable cellular allografts may be suitable for broad use in spinal surgery and bone defect reconstruction instead of autograft bone.

Clinical relevance: This study provides the first direct evaluation of MSCs in viable cellular bone allograft and comparative analysis with BM aspirates and autograft bone. This has implications for understanding MSC biology in the pre-clinical and clinical setting and for developing novel bone repair strategies using MSCs.