The results of an animal study, presented at the SIR 2012 Annual Scientific Meeting by J David Prologo, University Hospitals Case Medical Center, Cleveland, USA, and colleagues, showed that human mesenchymal stem cells delivered percutaneously under imaging guidance to porcine models of degenerated intervertebral discs were present and imageable on the day of and three days following transplantation.
The researchers told delegates that degenerated intervertebral discs are a significant contributor to low back pain, and effective therapies to treat this condition are lacking. “Stem cell therapies are new and have shown great promise for the regeneration and biological repair of degenerated intervertebral discs, and may represent a promising alternative to ablation, replacement, or immobilisation,” they said.
The investigators set out to establish the feasibility of percutaneously transplanting human mesenchymal stem cells under image guidance into porcine models of degenerated intervertebral discs. They obtained human bone marrow from patients undergoing hip or knee arthroplasty (following Institutional Review Board-approved informed consent) and then isolated, expanded and stored the mesenchymal stem cells.
The researchers induced intervertebral disc degeneration as per established methods at L1/L2 and L2/L3 in 28–35kg pigs. Two weeks following injury, they injected the stem cells using a 25-gauge needle into the middle one-third of the discs using a 22-gauge coaxial system under fluoroscopic guidance and delivered approximately 100,000 mesenchymal stem cells that were radiolabeled. They also obtained PET-CT imaging immediately following transplant and at three days post-procedure. “At 10 days post-transplant, treated and non-treated discs were harvested from one animal for immunohistochemical staining to detect sequences specific to human chromatin,” the authors wrote.
“After attaching an imaging agent to the injected cells, we were able to prove accurate delivery and containment of those cells at the desired site of action. And, we are now performing the first in human trials of this technique,” he added.
The same day PET-CT images showed radiopharmaceutical activity in the centre of the discs that corresponded to the transplanted levels. The authors also wrote that similar scans performed three days later confirmed the containment of these cells to their site of delivery. The staining results that were obtained 10 days after the transplantation procedure identified cells staining positive for sequences specific to human chromatin within the cellular matrix of the transplanted disc, and not in the control discs.
The results of the study led the authors to conclude that immunohistochemical staining of human specific sequences provided tissue validation of successful xenotransplant, and correlated with the post-transplant imaging.