Closing The Gap On Clinical Translation Of Cell-Based Therapies: Efficacious Stem Cell Therapy Without The Need For Cell Culture
Alexandra O. Luby, MS, Jessie M. Hoxie, BS, Gina N. Sacks, MD, Lauren Buchman, Lauren Patrick, Kevin M. Urlaub, BS, Jeremy V. Lynn, BS, Noah S. Nelson, MPH, Alexis Donneys, MD, Steven R. Buchman, MD.
University of Michigan, Ann Arbor, MI, USA.
PURPOSE: Adipose-derived stems cells (ASCs) have demonstrated promise across many areas of regenerative medicine, including bone tissue engineering. One major barrier to clinical translation and broad application of these therapeutics is current protocols which require the use of laboratory cell culture and onerous enzymatic digestion to produce stem cell rich product. A process of minimal manipulation by which stem cells can be used clinically without the intermediate step of cell culture has been the holy grail of bench to bedside tissue engineers. Therefore, the purpose of this study was to develop a clinically translatable technique for intra-operative harvest, isolation, and implantation of ASCs with the primary aim of enhancing bone healing at irradiated fracture sites.
METHODS: Male Lewis rats (n=36) were divided into groups: Fracture (Control), Radiation with Fracture (XRT), and Radiation with Fracture and ASC implantation (ASC). Experimental groups received 35Gy of radiation, and all groups underwent mandibular osteotomy and external fixation. Adipose tissue was harvested from the inguinal fat pads of donor animals. Tissue was minced, loaded into syringes, and serially processed using Tulip Sizing Transfers (2.4 mm, 1.4 mm, 1.2 mm). Serial filtration (800 micron, 400 micron) and centrifugation was performed. While the resultant oil and aqueous layers were discarded, the cell pellet was collected for immediate implantation at the osteotomy site. Animals were sacrificed on post-operative day 40. Gross pathology and MicroCT analysis were utilized to determine union rates and the quality of the bone formed at the osteotomy site.
RESULTS: Immediate implantation of mechanically processed ASCs significantly increased union rates compared to XRT alone (79% vs. 20%). Additionally, MicroCT analysis demonstrated high quality new bone formation in irradiated fractures treated with ASCs compared to the control based on bone mineral density (666.2 ± 32.0 vs. 312.2 ± 51.7; p=0.000) and bone volume fraction (0.744 ± 0.072 vs. 0.350 ± 0.041; p=0.000). In fact, implantation of ASCs into irradiated fracture sites resulted in bone quality similar to the bone formed at non-irradiated fracture sites, as there was no significant difference found between groups (BMD: 666.2 ± 32.0 vs. 710.3 ± 38.0; p=0.39, BVF: 0.744 ± 0.072 vs. 0.803 ± 0.04; p=0.30).
CONCLUSION: Adipose-derived stem cells demonstrate great potential in bone tissue engineering, including use in irradiated fracture healing. Clinical translation of these cell-based therapeutics remains limited, however, due to current protocols requiring separate laboratory processing and cell culture. In this study, we developed a novel approach that eliminates laboratory dependent techniques and instead, utilizes mechanical methods that would enable intra-operative ASC harvest, isolation, and immediate implantation. The results of this study are incredibly promising for the long-awaited translation of cell-based therapeutics into the clinical arena.
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