Introduction: Adipose tissue has been known for some time to contain regenerative cells. These regenerative cells are able to differentiate into a nucleus pulposus-like phenotype when exposed to environmental factors similar to disc. In an effort to develop a clinical option for cell placement and assess the response of the cells to the post-surgical milieu, adipose-derived cells were collected, concentrated, and transplanted under fluoroscopic guidance directly into a surgically damaged disc in a dog model.
Methods: After IACUC approval 12 dogs, 2 years of age, were obtained. Adipose cells were harvested from the super-scapular region of the neck (scruff) and adherent cells separated, collected, and labeled with DAPI. Three lumbar intervertebral disc levels in each dog underwent a partial nucleotomy; other levels served as non-operated controls. Levels of intervention as well as the regimen of treatment were dually randomized. Three interventions were used in this study; adipose-derived cells in hyaluronic acid (HA) carrier, HA alone, or no intervention. All deliveries were guided by fluoroscopy. The dogs were radiographed, received MRI scans and then euthanized by 12 months. The disc tissue was harvested from the lumbar spine in each dog. Cells labeled with DAPI prior to implantation were evident in the tissue. Matrix composition was assessed for aggrecan, Types I and II collagen by both RT-PCR (Table I) and ELISA (Table II) to assess and compare matrix regeneration. mRNA and protein from each level are presented with respect to normal values defined as the 100 percent expression.
Results: The results can be summarized as:
the regenerative cells are viable following implantation.
supplementing adipose cells following injury supports regeneration.
morphology was maintained.
intervertebral disc height was not lost.
MRI signal remained similar to native control.
hyaluronic acid was insufficient to prevent disc degeneration or desiccation.
lack of intervention resulted in progressive degeneration.
Discussion: This study provides evidence that adipose derived cells might offer a reliable source of regenerative potential capable of bio-restitution. The span of this study was sufficient to show that freshly isolated adipose-derived cells can be transplanted percutaneously and will survive the trauma associated with post-surgical inflammation to remain viable and produce appropriate, tissue-specific matrix.
