In this investigation, we administered oxidative stress to nucleus pulposus cells (NPCs), recognized DNA-damage-inducible transcript 4 (DDIT4) as a component in intervertebral disc degeneration (IVDD), and devised a hydrogel capable of conveying small interfering RNA (siRNA) to IVDD. An in vitro model for oxidative stress-induced injury in NPCs was developed to elucidate the mechanisms underlying the upregulation of DDIT4 expression, activation of the reactive oxygen species (ROS)-thioredoxin-interacting protein (TXNIP)-NLRP3 signalling pathway, and nucleus pulposus pyroptosis. Furthermore, the mechanism of action of small interfering DDIT4 (siDDIT4) on NPCs in vitro was validated. A triplex hydrogel named siDDIT4@G5-P-HA was created by adsorbing siDDIT4 onto fifth-generation polyamidoamine (PAMAM) dendrimer using van der Waals interactions, and then coating it with hyaluronic acid (HA). In addition, we established a rat puncture IVDD model to decipher the hydrogel’s mechanism in IVDD.Aims
Methods
The aim of this study is to compare the release of titanium (Ti) and zirconium (Zr) into the tissue surrounding Ti- and ZrO2-implants. Methyl methacrylate embedded mini pig maxillae with 6 Ti-implants and 4 ZrO2-implants were analysed after 12-weeks of implantation. The spatial distribution of elemental Ti and Zr in maxillae near implants was assessed with laser ablation (LA)-inductively coupled plasma (ICP)-mass spectrometry (MS). From each maxilla two bone slices adjacent to the implants were measured. The contents of Ti and Zr in these bone slices were determined by ICP-MS and ICP-optical emission spectrometry. Increased intensity of Ti and Zr could be detected in bone tissues at a distance of 891±398 µm (mean ± SD) from Ti-implants and 927±404 µm from ZrO2-implants. The increased intensity was mainly detected near implant screw threads. The average Ti content detected in 11 bone slices from samples with Ti-implants was 1.67 mg/kg, which is significantly higher than the Ti content detected in 8 slices from samples with ZrO2-implants. The highest Ti content detected was 2.17 mg/kg. The average Zr content in 4 bone slices from samples with ZrO2-implants is 0.59 mg/Kg, the other 4 bone slices showed Zr contents below the detection limit ( After 12-weeks of implantation, increased intensity of Ti and Zr can be detected in bone tissues near Ti- and ZrO2-implants. The results show that Ti content released from Ti-implants is higher than the Zr content released from ZrO2-implants.
