Overexpression of growth and differentiation factor-5 inhibits inflammatory factors released by intervertebral disc cells

Low back pain (LBP) is one of the most common musculoskeletal diseases in the world. The incidence is ~70% in adults and many of them suffer from disability. Recently, intervertebral disc degeneration (IDD) has been deemed as a main cause of LBP. The present study aimed to investigate the potentials of growth and differentiation factor-5 (GDF-5) in IDD. The protein levels of prostaglandin-E2 (PGE2), tumor necrosis factor (TNF)-α and interleukin (IL)-1β in culture medium were evaluated by ELISA. mRNA and protein expression levels in nucleus pulposus (NP) cells were evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting, respectively. Griess reaction was applied to test the nitric oxide (NO) concentration in the culture supernatant. The expression levels of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in NP cells were measured by RT-qPCR. Collagen-II, aggrecan, IκBα and phosphorylated (p)-p65 expression levels were detected by western blotting. Compared with the control group, protein expression levels of TNF-α, IL-1β and PGE2, and NO concentration in culture medium were upregulated by LPS, which were significantly repressed by GDF-5 overexpression (P<0.05). Additionally, GDF-5 overexpression reduced lipopolysaccharide-induced upregulation of TNF-α, IL-1β, iNOS, COX-2, collagen-II, aggrecan, IκBα and p-p65 expression levels in NP cells.

Preparation and Evaluation of Dexamethasone (DEX)/Growth and Differentiation Factor-5 (GDF-5) Surface-Modified Titanium Using β-Cyclodextrin-Conjugated Heparin (CD-Hep) for Enhanced Osteogenic Activity In Vitro and In Vivo

The most ideal implant models in the dental and orthopedic fields to minimize the failure rate of implantation involve the improvement of osseointegration with host bone. Therefore, a focus of this study is the preparation of surface-modified titanium (Ti) samples of disc and screw types using dexamethasone (DEX) and/or growth and differentiation factor-5 (GDF-5), as well as the evaluation of their efficacies on bone formation in vitro and in vivo. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle measurement were used to evaluate the surface chemical composition, surface morphology and wettability, respectively. The results showed that implant surfaces were successfully modified with DEX and/or GDF-5, and had rough surfaces along with hydrophilicity. DEX, GDF-5 or DEX/GDF-5 on the surface-modified samples were rapidly released within one day and released for 28 days in a sustained manner. The proliferation and bone formation of MC3T3-E1 cells cultured on pristine and surface-modified implants in vitro were examined by cell counting kit-8 (CCK-8) assay, as well as the measurements of alkaline phosphatase (ALP) activity and calcium deposition, respectively. MC3T3-E1 cells cultured on DEX/GDF-5–Ti showed noticeable ALP activity and calcium deposition in vitro. Active bone formation and strong osseointegration occurred at the interface between DEX/GDF-5–Ti and host bone, as evaluated by micro computed-tomography (micro CT) analysis. Surface modification using DEX/GDF-5 could be a good method for advanced implants for orthopaedic and dental applications.