The "gold standard" for treatment of
intervertebral disc herniations and degenerated discs is still
spinal fusion, corresponding to the saying "no disc - no
pain". Mechanical
prostheses, which are currently implanted, do only have medium outcome success and have relatively high re-operation rates. Here, we discuss some of the
biological intervertebral disc replacement approaches, which can be subdivided into at least two classes in accordance to the two different tissue types, the nucleus pulposus (NP) and the annulus fibrosus (AF). On the side of NP replacement
hydrogels have been extensively tested in vitro and in vivo. However, these
gels are usually a trade-off between cell biocompatibility and load-bearing capacity,
hydrogels which fulfill both are still lacking. On the side of AF repair much less is known and the question of the anchoring of implants is still to be addressed. New hope for
cell therapy comes from developmental biology investigations on the existence of intervertebral disc progenitor cells, which would be an ideal cell source for
cell therapy. Also notochordal cells (remnants of the embryonic notochord) have been recently pushed back into focus since these cells have regenerative potential and can activate disc cells.
Growth factor treatment and molecular
therapies could be less problematic. The
biological solutions for NP and AF replacement are still more fiction than fact. However, tissue engineering just scratched the tip of the iceberg, more satisfying solutions are yet to be added to the biomedical pipeline.