Abstract: Human Perivascular Stem Cells Induce Bone Regeneration In A Rat Spinal Fusion Model (2013 AAAS Annual Meeting (14-18 February 2013))

Saturday, February 16, 2013

Auditorium/Exhibit Hall C (Hynes Convention Center)

Le Chang , Dental and Craniofacial Research Institute, School of Dentistry, University of California, Los Angeles, Los Angeles, CA

Greg Astrian , Dental and Craniofacial Research Institute, School of Dentistry, University of California, Los Angeles, Los Angeles, CA

Choon Chung , Dental and Craniofacial Research Institute, School of Dentistry, University of California, Los Angeles, Los Angeles, CA

Aaron James , Department of Pathology & Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA

Autologous bone grafting, the current gold standard for orthopedic spinal fusion procedures, is impeded by donor site mortality, limited bone supply and complications associated with extended surgical time. Recently, the search for a novel source to engineer bone and soft tissue has led to increased interest in stem cell therapies. Human Perivascular Stem Cells (hPSCs) have been identified by our laboratory and show promise as osteoprogenitor cells. hPSCs are abundantly found in pericytes and adventitial cells of microvessels and large blood vessels from human lipoaspirate. In this study, we analyzed rat spines samples after spinal fusion to evaluate the osteogenic potential of hPSCs.

We obtained PSCs that were sorted from cosmetic liposuction by FACS (Fluorescent-activated cell sorting), based on differential expression of CD45, CD34, and CD146. Our rat spine samples were derived from postereolateral lumbar spinal fusion that was performed on 22 athymic rodents, randomly assigned to treatment groups of varying hPSC dosages (0, 0.15 million, 0.50 million, and 1.5 million hPSCs) using a scaffold of demineralized bone matrix (DBX). Animals were sacrificed at 4 weeks postoperative and spine samples were harvested, fixed in formalin and imaged using high-resolution micro Computed Tomography (MicroCT). Images were analyzed in CTAn to determine bone volume and trabecular number. Samples were decalcified in 19% EDTA, embedded in paraffin, sectioned, and stained for histological analysis. In addition, dynamic biomechanical analyses were performed to calculate torsional strength and stability of the spines.

Manual palpation by application of flexion and extension forces revealed 20% fusion in DBX-only treated animals, while hPSC-treatments obtained 80-100% fusion. MicroCT reconstructions exhibited evidence of non-fusion between DBX-only treated animals, whereas significant bilateral bony bridges were found in all hPSC-treated spines. MicroCT data analysis showed 138-140% increase in bone volume and 119-126% increase in trabecular number when PSC treatment was compared to acellular DBX. Histology revealed increased osteoblast expression, bone volume and evidence of endochondral bone formation in hPSC treated groups. Finally, finite element analysis of hPSC treated groups demonstrated increased biomechanical stability, lower strain energy and less stress strained elements.

In summary, hPSCs exhibit high availability and improved osteogenic potential in the rat spinal fusion model. With the aging US population, bone graft substitutes are needed to increase the standard of care and a surgeon’s armamentarium in spinal fusion procedures. Although further investigation is necessary, the present study shows promise for hPSC-based products as an alternative for bone-graft procedures.