Nanofibrous Scaffolds Help Regenerate Nucleus Pulposus in Intervertebral Discs
Introduction: The authors developed biodegradable 3D scaffolds with interconnected macropores and a nanofibrous matrix that mimicked the extracellular matrix of healthy discs. This animal study was designed to determine whether the nanofibrous scaffolds—when seeded with nucleus pulposus cells—could improve cell viability, promote nucleus pulposus cell proliferation, and tissue regeneration.
Methods: The nanofibrous scaffolds were compared with control solid-walled scaffolds that were made from the same material with the same macropore structure but lacked the nanofibrous feature. The scaffolds were tested in three models:
- In vitro nucleus pulposus tissue engineering
- Subcutaneous implantation for ectopic nucleus pulposus tissue formation in a mouse model
- Athymic rat caudal disc repair
In all models, the nanofibrous scaffolds were seeded with rabbit nucleus pulposus cells and cultured for 3 weeks in an attempt to promote cell regeneration.
Results: In the in vitro model, significantly more cells were found in the nanofibrous scaffolds than in the control scaffolds at 3 weeks (P<0.05). The subcutanous implants in mouse models showed significantly greater production of glycosaminoglycan and type II collagen (ie, the primary components of extracellular matrix of the nucleus pulposus) in the nanofibrous scaffolds than in the control scaffolds.
In the rat caudal disc repair model, the tissue-engineered nucleus pulposus survived, regenerated, remained in place, and maintained a disc height similar to that of normal control discs at 12 weeks. In the solid-walled scaffold group, the disc space narrowed and growth of fibrous tissue was found.
Conclusion: Tissue-engineered nucleus pulposus developed using nanofibrous scaffolds appear to be a promising option for enhancing nucleus pulposus cell proliferation and achieving physiological function in animal models of intervertebral disc degradation.
This interesting paper reports on the use of a biodegradable nanoparticle scaffold as a substrate for growing nucleus pulposus cells. Most of the research on disc regeneration has focused on cellular and/or protein as a way to rejuvenate the damaged disc. This paper provides a proof of concept that a biodegradable nanofibrous scaffold could be used to regenerate an intravertebral disc.
The scaffold, which had large pores for cell ingrowth, was engineered to replicate the construct of the extracellular matrix in a healthy disc. The comparison scaffold was a solid-state scaffold made of the same material as the nanofibrous matrix. In all three settings, this nanofibrous scaffold performed better than the solid-state scaffold.
The paper makes the point that a nanofibrous matrix would aid in disc regeneration by supplying a substrate and environment for cellular regeneration of the damaged disc. This is especially exciting since the authors were able to demonstrate this in vitro, which would indicate the possibility of actually growing/regenerating the nucleus pulposus of an intervertebral disc in vitro for later implantation.