Sustained release of GDF5 from a designed coacervate attenuates disc degeneration in a rat model.

Low back pain is often caused by intervertebral disc degeneration, which is characterized by nucleus pulposus (NP) and extracellular matrix (ECM) degeneration. Human adipose-derived stem cells (hADSCs) induced by growth and differentiation factor-5 (GDF5) can differentiate into an NP-like phenotype. Although stem cell-based therapy with prolonged exposure to growth factors is regarded as a promising treatment, the efficacy of this approach in attenuating the disc degeneration process is limited by the short lifespan of growth factors. In our study, a unique growth factor delivery vehicle composed of heparin and the synthetic polycation poly(ethylene argininylaspartate diglyceride) (PEAD) was used to sustain GDF5 release. The results showed that sustained release of GDF5 by the PEAD:heparin delivery system promoted hADSC differentiation to an NP-like phenotype in vitro. After injection of the PEAD:heparin:GDF5 delivery platform and hADSCs into intervertebral spaces of coccygeal (Co) vertebrae Co7/Co8 and Co8/Co9 of the rat, the disc height, water content, and structure of the NPs decreased more slowly than other treatment groups. This new strategy may be used as an alternative treatment for attenuating intervertebral disc degeneration with hADSCs without the need for gene therapy. STATEMENT OF SIGNIFICANCE: Low back pain is often caused by intervertebral disc degeneration, which is characterized by nucleus pulposus (NP) and extracellular matrix (ECM) degeneration. Human adipose-derived stem cells (hADSCs) induced by growth and differentiation factor-5 (GDF-5) can differentiate into an NP-like phenotype. Although stem cell-based therapy with prolonged exposure to growth factor is regarded as a promising treatment, the efficacy of this approach in the disc regeneration process is limited by the short life of growth factors. In our study, a unique growth factor delivery vehicle comprised of heparin and the synthetic polycation poly(ethylene argininylaspartate diglyceride) (PEAD) was used to sustain the release of GDF-5. Numerous groups have explored IDD regeneration methods in vitro and in vivo. Our study differs in that GDF5 was incorporated into a vehicle through charge attraction and exhibited a sustained release profile. Moreover, GDF-5 seeded coacervate combined with hADSC injection could be a minimally invasive approach for tissue engineering that is suitable for clinical application. We investigated the stimulatory effects of our GDF-5 seeded coacervate on the differentiation of ADSCs in vitro and the reparative effect of the delivery system on degenerated NP in vivo.

Dual release of dexamethasone and TGF-ß3 from polymeric microspheres for stem cell matrix accumulation in a rat disc degeneration model.

Low back pain is frequently caused by nucleus pulposus (NP) degeneration. Tissue engineering is a powerful therapeutic strategy which could restore the normal biomechanical motion of the human spine. Previously we reported that a new nanostructured three-dimensional poly(lactide-co-glycolide) (PLGA) microsphere, which is loaded with dexamethasone and growth factor embedded heparin/poly(l-lysine) nanoparticles via a layer-by-layer system, was an effective cell carrier in vitro for NP tissue engineering. This study aimed to investigate whether the implantation of adipose-derived stem cell (ADSC)-seeded PLGA microspheres into the rat intervertebral disc could regenerate the degenerated disc. Changes in disc height by plain radiograph, T2-weighted signal intensity in magnetic resonance imaging (MRI), histology, immunohistochemistry and matrix-associated gene expression were evaluated in normal controls (NCs) (without operations), a degeneration control (DC) group (with needle puncture, injected only with Dulbecco's modified Eagle's medium), a PLGA microspheres (PMs) treatment group (with needle puncture, PLGA microspheres only injection), and PLGA microspheres loaded with ADSCs treatment (PMA) group (with needle puncture, PLGA microspheres loaded with ADSC injection) for a 24-week period. The results showed that at 24 weeks post-transplantation, the PM and PMA groups regained disc height values of ∼63% and 76% and MRI signal intensities of ∼47% and 76%, respectively, compared to the NC group. Biochemistry, immunohistochemistry and gene expression analysis also indicated the restoration of proteoglycan accumulation in the discs of the PM and PMA groups. However, there was almost no restoration of proteoglycan accumulation in the discs of the DC group compared with the PM and PMA groups. Taken together, these data suggest that ADSC-seeded PLGA microspheres could partly regenerate the degenerated disc in vivo after implantation into the rat degenerative intervertebral disc.