Tissue engineering and regenerative medicine techniques offer long-term tissue repairing options with the possibility to restore intervertebral disc function. Stem cells have the potential to repopulate and regenerate the IVD. There are several potential sources of stem cells, including adipose tissue, bone marrow, and other tissues such as embryonic and fetal stem cells. Embryonic and fetal stem cells are pluripotent cells with a potential to differentiate into any body tissue. These cells are highly flexible since they can differentiate into any type of tissue, but both the procurement of embryonic stem cells and research are limited, given the related ethical issues. Embryonic cells are not used clinically in the treatment of pets.
Figure 4
Adult stem cells can be used to treat intervertebral disc disease. Many studies have shown that IVDD can be treated or repaired with the injection of Mesenchymal Stem Cells (MSCs), multipotent cells able to differentiate into tissues of mesenchymal origin, including bone, cartilage, fat, muscle, and fibrous tissues, depending on the biological environment.
These cells can be obtained from multiple adult tissues, including bone marrow, trabecular bone, articular cartilage, muscle, and adipose tissue, which represent a variant of the adult stem cell,
Figure 5
While a variety of cell sources in the field of stem cell research have been proposed for clinical application, Autologous Adipose Stem Cells (ASCs) as a cell source in bone and cartilage repair have gained significant attention. In fact, adipose tissue is considered a suitable source of stem cells for clinical use, given the ease of the procedure to retrieve adipose tissue. This procedure is minimally invasive and large numbers of cells are obtained. Treatment of IVDD can occur with an injection of autologous adipose stem cells (ASCs). The adipose derived cells can be mixed with Platelet Rich Plasma to add growth factors and increase potency. Hyaluronic acid can also be used to provide a support matrix for the stem cells.
Adipose derived stem cells injected into collapsed, degenerated discs act to regenerate the disc. The stem cells produce a collagen, proteoglycan, and macromolecule matrix that is indistinguishable from a normal disc. This chemical structure attracts water, causing the collapsed disc to re-inflate and expand the disc space between the vertebrae. This flattens out the previously folded ligaments on the floor of the spinal canal, thereby reducing pressure on the spinal cord. The extruded disc material pressing against the spinal cord now has more space and less pressure on it. The anti-inflammatory effects of the ASCs and stromal vascular fraction of cells reduces damaging effects of the previously extruded disc material on the spinal cord. Disc regeneration is rapid, occurring within two weeks of treatment and continuing for at least six months after therapy. Disc regeneration can also be given to patients before complete degeneration and collapse of the disc space to prevent disease associated with compression of the spinal cord.
ASCs injected into damaged spinal cord, aid in healing by reducing the glial scar formation and promoting neurogenesis. Studies have shown that in dogs with no deep pain perception prior to surgical decompression with hemilaminectomy that received a single injection of ASCs into the spinal cord had better clinical outcomes than dogs with surgery alone. Improved clinical signs after transplantation of ASCs are primarily attributed to a modified inflammatory environment and increased survival of endogenous nerve cells. Moreover, transplanted ASCs reduce regulatory signal molecules related to glial scar formation and can partially differentiate into neural cells.
