Intervertebral disc degeneration (IVDD) is one of the key predisposing factors for low back pain. Although the exact mechanism remains unclear, inflammatory response and nucleus pulposus (NP) apoptosis are known to play important roles in this process. Prolactin protects against inflammation-associated chondrocyte apoptosis in arthritis. Based on prior studies, we hypothesized that prolactin might have therapeutic effects on IVDD by inhibiting the apoptosis of degenerative human disc NP cells. An experimental model of IVDD was established in 3-month-old Sprague-Dawley rats by submitting them to percutaneous disc puncture with a 20-gauge needle on levels 7–8 and 8–9 of the coccygeal vertebrae. Then the rats were injected with 20 or 200 ng prolactin on a weekly basis. Radiologic and histologic analyses were performed on days 4, 7, 14, and 28. The expression of prolactin and its receptor was analyzed in human tissue obtained from symptomatic patients undergoing microencoscopy discectomy, or from scoliosis patients undergoing deformity correction surgery. The results showed that intradiscal injection of prolactin maintained disc height and the mean signal intensity of the punctured disc. Histological analysis indicated that prolactin treatment significantly retained the complete structure of the NP and annulus fibrosus compared with the vehicle group. In addition, more collagen II, but fewer collagen I-containing tissues were detected in the prolactin treatment groups compared to the vehicle group. Moreover, low levels of tumor necrosis factor-α, interleukin-1β, cleaved-caspase 3, and TUNEL staining were observed in the prolactin treatment groups. We also demonstrated that prolactin impaired puncture-induced inflammation and cell apoptosis by downregulating activation of the NF-κB pathway. The degenerated NP tissues from patients had decreased expression of prolactin and its receptor, whereas expression was increased in the NP tissues removed from scoliosis patients. These results suggest that prolactin may be a novel therapeutic target for the treatment of IVDD.

Intervertebral disc (IVD) degeneration (IDD) is a major cause of low back pain. The pathogenesis of IDD is associated with the disturbance of reactive oxygen species (ROS) equilibrium, inflammation, and matrix loss. Aspirin is a nonsteroidal anti-inflammatory drug that effectively inhibits inflammation and oxidative stress and has been widely used for the treatment of back pain. Therefore, we hypothesize that aspirin reverses the IDD process via antioxidative and anti-inflammatory effects on the AMPK signaling pathway. In vitro, aspirin diminished cellular oxygen free radicals (ROS, nitric oxide (NO)) and inflammatory cytokines (interleukin- (IL-) 1β and IL-6 and tumor necrosis factor alpha (TNF-α)) induced by lipopolysaccharides (LPS) in nucleus pulposus cells (NPCs). We found that aspirin preserved the extracellular matrix (ECM) content of collagen type II (COL2) and aggrecan while inhibiting the expression of matrix-degenerating enzymes, including matrix metalloproteinase 3 and 13 (MMP-3 and MMP-13) and A disintegrin and metalloproteinase with thrombospondin motifs 4 and 5 (ADAMTS-4, ADAMTS-5). Aspirin significantly promoted the ratios of p-AMPK to AMPK and p-ACC to ACC expression in NPCs. Furthermore, pretreatment with the AMPK inhibitor compound C abrogated the antioxidant effects of aspirin. In vivo, an IDD model was established in Sprague-Dawley rats via percutaneous disc puncture with the 20-gauge needle on levels 8-9 and 9-10 of the coccygeal vertebrae. Imaging assessment showed that after aspirin treatment, improvements in disc height index (DHI) ranged from 1.22-fold to 1.54-fold and nucleus pulposus signal strength improved from 1.26-fold to 1.33-fold. Histological analysis showed that aspirin treatment prevented the loss of COL2 and decreased MMP-3 and MMP-13, inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), IL-1β, and TNF-α expression in the IVD tissues. These results suggest that treatment with aspirin could reverse the IDD process via the AMPK signaling pathway, which provides new insights into the potential clinical applications of aspirin, particularly for IDD treatment.

Senescence of nucleus pulposus (NP) cells (NPC) is a major cause of intervertebral disc degeneration (IVDD), so delay NPC senescence may be beneficial for mitigating IVDD. We studied the effect and mechanism of silent information regulator 2 homolog 3 (SIRT3) on NPC senescence in vivo and in vitro. First, we observed SIRT3 expression in normal and degenerated NPC with immunohistochemical and immunofluorescence staining. Second, using SIRT3 lentivirus transfection, reactive oxygen species probe, senescence-associated β-galactosidase staining, polymerase chain reaction, and western blot to observe the oxidative stress, senescence, and degeneration degree among groups. Subsequently, pretreatment with adenosine monophosphate-activated protein kinase (AMPK) agonists and inhibitors, observing oxidative stress, senescence, and degeneration degree among groups. Finally, the IVDD model was constructed and divided into Ctrl, Vehicle, LV-shSIRT3, and LV-SIRT3 groups. X-ray and magnetic resonance imaging scans were performed on rat's tails after 1 week; hematoxylin and eosin and safranin-O staining were used to evaluate the degree of IVDD; immunofluorescence staining was used to observe SIRT3 expression; immunohistochemical staining was used to observe oxidative stress, senescence, and degeneration degree of NP. We found that SIRT3 expression is reduced in degenerated NP tissues but increased in H 2 O 2 -induced NPC. Moreover, SIRT3 upregulation decreased oxidative stress, delayed senescence, and degeneration of NPC. In addition, activation of the AMPK/PGC-1α pathway can partially mitigate the NPC oxidative stress, senescence, and degeneration caused by SIRT3 knockdown. The study in vivo revealed that local SIRT3 overexpression can significantly reduce oxidative stress and ECM degradation of NPC, delay NPC senescence, thereby mitigating IVDD. In summary, SIRT3 mediated by the AMPK/PGC-1α pathway mitigates IVDD by delaying oxidative stress-induced NPC senescence.

Surgery is the final choice for most patients with intervertebral disc degeneration (IDD). Operation-caused trauma will cause inflammation in the intervertebral disc. Serious inflammation will cause tissue defects and induce tissue degeneration, IDD recurrence and the occurrence of other diseases. Therefore, we proposed a scheme to treat recurrence after discectomy by inhibiting inflammation with an aspirin (ASP)-loaded hydrogel to restore the mechanical stability of the spine and relieve local inflammation. ASP-liposomes (ASP-Lips) were incorporated into a photocrosslinkable gelatin-methacryloyl (GelMA) via mixing. This material can effectively alleviate inflammation by inhibiting the release of high mobility group box 1 (HMGB1) from the nucleus to the cytoplasm. We further assessed the expression of inflammatory cytokines, such as interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α), and degeneration-related factors, such as type II collagen (COL-2), Aggrecan, matrix metallopeptidases-3 (MMP-3), MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4) and ADAMTS-5 in rat nucleus pulpous cells. The level of IDD was analyzed through H&E, safranin-O staining and immunohistochemistry in rabbit samples. In vitro , we found that ASP-Lip@GelMA treatment significantly decreased inflammatory cytokines, MMP-3 and -13, and ADAMTS-4 and -5 and up-regulated COL-2 and Aggrecan via the inhibited release of HMGB-1 from the nucleus. In vivo, ASP-Lip@GelMA can effectively inhibit inflammation of local tissue after disc surgery and fill local tissue defects. This composite hydrogel system is a promising way to treat the recurrence of IDD after surgery without persistent complications.

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Wear particle-induced inflammation is a major factor contributing to aseptic loosening in peri-prosthetic tissue. The effects of cannabinoid receptor 2 (CB(2)) on wear particle-induced inflammation remain unclear. Reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay were used to assess the effects of a CB(2)-selective antagonist, AM630, on regulation of the inflammatory reaction and production of pro-inflammatory cytokines in response to in vitro and in vivo stimulation with titanium particles. In vitro studies, in a model for pre-osteoclast-like cells, demonstrated that AM630 inactivation of CB(2) profoundly inhibited interleukin (IL)-1β and tumour necrosis factor (TNF)-α production by RAW264.7 cells stimulated with titanium particles. In vivo findings in a murine air-pouch model of titanium-induced inflammatory osteolysis indicated that AM630 reduced titanium-induced tissue inflammation, seen as a reduction in pouch membrane thickness, inflammatory infiltration and levels of the pro-inflammatory cytokines IL-1β and TNF-α. Thus, inactivation of CB(2) by AM630 inhibited the titanium particle-induced inflammatory reaction by reducing pro-inflammatory cytokines in vitro and in vivo.

The presence of previous or concomitant VFs leads to further imaging examination, which helps identify the occult VFs. Preoperative MRI examination especially T1 and STIR sequences plays a vital role in the early diagnosis of occult VFs. Except for significant pain relief and functional improvement, VP and KP can effectively prevent delayed vertebral collapse of occult VFs comparing to previous reported data.

Wear particle-induced osteoclastogenesis is the most common cause of aseptic loosening in total joint arthroplasty. Although cyclooxygenase (COX)-2, an inducible regulator of prostaglandin E2 (PGE2) synthesis, is known to be involved in osteoclast differentiation, its effect on osteoclastogenesis in response to wear particles remains unclear. In this study, we investigated the role of COX-2 in the regulation of osteoclast differentiation in the osteoclast precursor cell line RAW264.7 stimulated with titanium (Ti) particles. The results showed COX-2 expression in the early stages of RAW264.7 differentiation when stimulated with receptor activator of nuclear factor kappa B ligand (RANKL) and Ti particles. Blockade of COX-2 by celecoxib, a COX-2 selective inhibitor, effectively reduced the expression of PGE2 and inhibited differentiation of RAW264.7 cells into tartrate-resistant acid phosphatase-positive (TRAP+) osteoclastic cells. Quantitative real-time polymerase chain reaction revealed that celecoxib inhibited mRNA expression of RANK, cathepsin K (CPK), TRAP, and the nuclear factor of activated T cells c1 (NFATc1) in RAW264.7 cells stimulated by Ti particles and RANKL. Moreover, exogenous PGE2 reversed the inhibitory effects of celecoxib. These results provide direct evidence that COX-2 dependent PGE2 induced by RANKL and Ti particles is required for osteoclastogenesis and suggests that reduced production of PGE2 by inactivation of COX-2 would provide a promising therapeutic target for the treatment of osteoclastogenesis induced by wear particles.