Chondroprotective supplemented injectable scaffold for nucleus pulposus tissue engineering

The nucleus pulposus (NP) plays an essential role in the mechanical properties of the intervertebral disc (IVD). As a result of intervertebral disc (IVD) degeneration, the nucleus pulposus (NP) is no longer able to withstand applied load leading to pain and disability. Current treatments can only alleviate associated symptoms of IVD degeneration and highly invasive surgeries do not preserve the biological function of the disc. This research employs a tissue engineering strategy to fabricate a NP scaffold as a minimally invasive means to restore biomechanical function to a degenerated disc. Firstly, a tissue-engineered injectable scaffold was prepared using different concentrations of alginate and calcium chloride and mechanically evaluated. Fabrication conditions were chosen based on structural and mechanical resemblance to the native NP. Chondroprotective supplementation, glucosamine (GCSN) and chondroitin sulfate (CS), were added to scaffolds at concentrations of 0:0 µg/mL (0:0-S), 125:100 µg/mL (125:100-S), 250:200 µg/mL (250:200-S), and 500:400 µg/mL (500:400-S), GCSN and CS, respectively. Scaffolds were used to fabricate tissue-engineered constructs through encapsulation of human nucleus pulposus cells (HNPCs). The tissue-engineered constructs were collected at days 1, 14, and 28 for biochemical and biomechanical evaluations. Confocal microscopy showed HNPC viability and rounded morphology over the 28 day period. MTT analysis resulted in significant increases in cell proliferation for each group. Collagen type II ELISA quantification and compressive moduli showed increasing trends for both 250:200-S and the 500:400-S groups on Day 28 with significantly greater compressive moduli compared to 0:0-S (control) group. Glycosaminoglycan and water content decreased for all groups. Results indicate the increased mechanical properties of the 250:200-S and the 500:400-S was due to production of a functional matrix. This study demonstrated potential for a chondroprotective supplemented injectable scaffold to restore biomechanical function of a degenerative disc through the production of a mechanically functional matrix.