In healthy intervertebral discs (IVDs), nerves and blood vessels are present only in the outer annulus fibrosus, while in degenerative IVDs, a large amount of nerve and blood vessel tissue grows inward. Evidence supports that neurogenic inflammation produced by neuropeptides such as substance P and calcitonin gene related peptide released by the nociceptive nerve fibers innervating the IVDs plays a crucial role in the process of IVD degeneration. Recently, non-neuronal cells, including IVD cells and infiltrating immune cells, have emerged as important players in neurogenic inflammation. IVD cells and infiltrating immune cells express functional receptors for neuropeptides through which they receive signals from the nervous system. In return, IVD cells and immune cells produce neuropeptides and nerve growth factor, which stimulate nerve fibers. This communication generates a positive bidirectional feedback loop that can enhance the inflammatory response of the IVD. Recently emerging transient receptor potential channels have been recognized as contributors to neurogenic inflammation in the degenerative IVDs. These findings suggest that neurogenic inflammation involves complex pathophysiological interactions between sensory nerves and multiple cell types in the degenerative IVDs. Clarifying the mechanism of neurogenic inflammation in IVD degeneration may provide in-depth understanding of the pathology of discogenic low back pain.

Intervertebral disc degeneration (IVDD) stands as a primary pathophysiological driver of low back pain, yet no therapeutic intervention effectively arrests its progression. Evidence shows that certain Sirt1 agonists may confer protective effects on intervertebral discs, but the underlying mechanisms remain unclear. This study aims to delineate the interaction between Sirt1 and the inflammatory microenvironment, offering potential novel avenues for IVDD prevention and treatment.

In vitro IL-1β-induced nucleus pulposus cells (NPCs) degenerative model and in vivo a mouse annulus fibrosus needle puncture model in Sirt1 transgenic (Sirt1TG) and the same litter WT mice were used to investigate the role of Sirt1 in homeostasis and inflammation. Mechanistic insights were obtained through RNA sequencing, co-immunoprecipitation (Co-IP), luciferase assays, and chromatin immunoprecipitation-(ChIP)-PCR. A co-culture system of Raw264.7 and NPCs was employed to assess the involvement of Lipocalin 2.

Our study demonstrated reduced Sirt1 expression in degenerating human nucleus pulposus (NP) tissue. Both in vitro and in vivo data revealed that NP-specific overexpression of Sirt1 inhibited extracellular matrix degradation and inflammation. Mechanistically, Sirt1 suppressed the acetylation of RelA/p65 at lysine 310 and phosphorylation at serine 536, with the C-terminus of Sirt1 and the RHD-NLS domain of RelA mediating to their interaction. Furthermore, NPCs-derived Lipocalin 2 was identified as a cytokine involved in macrophage chemotaxis and M1 polarization to exacerbate inflammation.

Our work revealed that Sirt1 negatively regulates Lipocalin 2, thereby ameliorating the inflammatory milieu and blocking NPCs and macrophages crosstalk.

This study illuminates the crucial role and molecular mechanisms of Sirt1 in regulating the NP microenvironment. These insights shed light on strategies for the prevention and treatment of IVDD-related herniation and low back pain. By pinpointing specific biological targets, the screening of smallmolecule compounds with significant clinical implications can be facilitated. This translational innovation promises to optimize cells communication within intervertebral disc microenvironment via localized drug delivery, potentially improving patient outcomes and satisfaction following spinal fusion or discectomy surgeries.

Microvascular changes are considered key factors in the process of intervertebral disk degeneration (IDD). Microvascular invasion and growth into the nucleus pulposus (NP) and cartilaginous endplates are unfavorable factors that trigger IDD. In contrast, the rich distribution of microvessels in the bony endplates and outer layers of the annulus fibrosus is an important safeguard for the nutrient supply and metabolism of the intervertebral disk (IVD). In particular, the adequate supply of microvessels in the bony endplates is the main source of the nutritional supply for the entire IVD. Microvessels can affect the progression of IDD through a variety of pathways. Many studies have explored the effects of microvessel alterations in the NP, annulus fibrosus, cartilaginous endplates, and bony endplates on the local microenvironment through inflammation, apoptosis, and senescence. Studies also elucidated the important roles of microvessel alterations in the process of IDD, as well as conducted in-depth explorations of cytokines and biologics that can inhibit or promote the ingrowth of microvessels. Therefore, the present manuscript reviews the published literature on the effects of microvascular changes on IVD to summarize the roles of microvessels in IVD and elaborate on the mechanisms of action that promote or inhibit de novo microvessel formation in IVD.

Oxidative stress and inflammation have pivotal roles in gastric ulcer development caused by alcohol consumption. Trace element boric acid taken into the human and animal body from dietary sources displays strong antioxidant and anti-inflammatory functions. However, the mechanisms underlying these actions of boric acid remain unclear, and its effectiveness in preventing gastric lesions is unknown. Therefore, the present study was undertaken to evaluate the protective effects of boric acid in alcohol-induced gastric ulcer and elucidate its potential mechanisms. Gastric ulcer was induced by 75% oral ethanol administration in rats, and the effectiveness of prophylactic boric acid treatment at 100 mg/kg concentration was assessed by histopathological examination, ELISA assay and qRT-PCR. Gross macroscopic and histopathological evaluations revealed that boric acid alleviated gastric mucosal lesions. Boric acid decreased reactive oxygen species (ROS) and malondialdehyde (MDA) concentration and the overall oxidation state of the body while improving antioxidant status. It reduced the concentration of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). The mRNA expression of JAK2 and STAT3 was decreased while the expression of AMPK was increased with boric acid pretreatment. Moreover, Sema3A and PlexinA1 levels were elevated upon boric acid pretreatment, and homocysteine levels were reduced. Our results demonstrated that boric acid protects gastric mucosa from ethanol-induced damage by regulating oxidative and inflammatory responses. In addition, our findings suggested that the gastroprotective activity of boric acid could be attributed to its regulatory function in the IL-6/JAK2/STAT3 signaling modulated by AMPK and that Sema3A/PlxnA1 axis and homocysteine are potentially involved in this process.

Intervertebral disk degeneration (IVDD) can be effectively treated using platelet-rich plasma (PRP). While the exact process is fully understood, it is believed that using pure PRP (P-PRP) without leukocytes is a better option for preventing IVDD. Semaphorin-3A (Sema3A), an inhibitor of angiogenesis and innervation, is essential for preserving IVDD's homeostasis. Whether PRP prevents IVDD by modifying Sema3A has yet to receive much research. This work aims to clarify how P-PRP affects Sema3A when IVDD develops in vitro.

Nucleus pulposus cells (NPCs) isolated from 8-week-old male Sprague-Dawley rats were exposed to 10 ng/ml IL-1β and then treated with P-PRP or leukocyte platelet-rich plasma (L-PRP) in vitro, followed by measuring cell proliferation, apoptosis and microstructures, inflammatory gene and Sema3A expression, as well as anabolic and catabolic protein expression by immunostaining, quantitative real-time polymerase chain reaction (qPCR), western blot, and enzyme-linked immunosorbent assay (ELISA).

In comparison with L-PRP, P-PRP had a higher concentration of growth factors but a lower concentration of inflammatory substances. P-PRP increased the proliferation of NPCs, while IL-1 relieved the amount of apoptosis due to its intervention. Anabolic genes, aggrecan, and collagen II had higher expression levels. MMP-3 and ADAMTS-4, two catabolic or inflammatory genes, showed lower expression levels. Sema3A activity was enhanced after P-PRP injection, whereas CD31 and NF200 expression levels were suppressed.

P-PRP enhanced the performance of NPCs in IVDD by modifying the NF-κB signaling pathway and encouraging Sema3A expression, which may offer new therapy options for IVDD.

The findings provide a new therapeutic target for the treatment of IVDD and show a novel light on the probable mechanism of PRP and the function of Sema3A in the progression of IVDD.

Bone morphogenetic protein (BMP) gene delivery to Lewis rat lumbar intervertebral discs (IVDs) drives bone formation anterior and external to the IVD, suggesting the IVD is inhospitable to osteogenesis. This study was designed to determine if IVD destruction with a proteoglycanase, and/or generating an IVD blood supply by gene delivery of an angiogenic growth factor, could render the IVD permissive to intra-discal BMP-driven osteogenesis and fusion. Surgical intra-discal delivery of naïve or gene-programmed cells (BMP2/BMP7 co-expressing or VEGF165 expressing) +/- purified chondroitinase-ABC (chABC) in all permutations was performed between lumbar 4/5 and L5/6 vertebrae, and radiographic, histology, and biomechanics endpoints were collected. Follow-up anti-sFlt Western blotting was performed. BMP and VEGF/BMP treatments had the highest stiffness, bone production and fusion. Bone was induced anterior to the IVD, and was not intra-discal from any treatment. chABC impaired BMP-driven osteogenesis, decreased histological staining for IVD proteoglycans, and made the IVD permissive to angiogenesis. A soluble fragment of VEGF Receptor-1 (sFlt) was liberated from the IVD matrix by incubation with chABC, suggesting dysregulation of the sFlt matrix attachment is a possible mechanism for the chABC-mediated IVD angiogenesis we observed. Based on these results, the IVD can be manipulated to foster vascular invasion, and by extension, possibly osteogenesis.

Intervertebral disc degeneration (IVDD) has been the major contributor to chronic lower back pain (LBP). Abnormal apoptosis, senescence, and pyroptosis of IVD cells, extracellular matrix (ECM) degradation, and infiltration of immune cells are the major molecular alternations during IVDD. Changes at tissue level frequently occur at advanced IVD tissue. Ectopic ingrowth of nerves within inner annulus fibrosus (AF) and nucleus pulposus (NP) tissue has been considered as the primary cause for LBP. Innervation at IVD tissue mainly included sensory and sympathetic nerves, and many markers for these two types of nerves have been detected since 1940. In fact, in osteoarthritis (OA), beyond pain transmission, the direct regulation of neuropeptides on functions of chondrocytes have attracted researchers' great attention recently. Many physical and pathological similarities between joint and IVD have shed us the light on the neurogenic mechanism involved in IVDD. Here, an overview of the advances in the nervous system within IVD tissue will be performed, with a discussion on in the role of nerve fibers and their neurotransmitters in regulating IVDD. We hope this review can attract more research interest to address neuromodulation and IVDD itself, which will enhance our understanding of the contribution of neuromodulation to the structural changes within IVD tissue and inflammatory responses and will help identify novel therapeutic targets and enable the effective treatment of IVDD disease.

Hyaluronic acid (HA) is widely recognized as a therapeutic target and currently used in medicine. However, HA metabolism during intervertebral disc degeneration (IVDD) has not been completely elucidated. This study aimed to evaluate the efficacy of HA on intervertebral disc (IVD) inflammation and identify the main molecules modulating HA degradation in IVDs. To assess HA function in IVD cells in vitro, we treated human disc cells and U-CH1-N cells, a notochordal nucleus pulposus cell line, with HA or hyaluronidase. Real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis showed that tumor necrosis factor alpha (TNF-α)-mediated induction of the expression of TNF-α and cyclooxygenase-2 (COX2) was clearly neutralized by HA treatment, and the expression of TNF-α and COX2 was significantly induced by hyaluronidase treatment in both cell types. Additionally, Western blot analysis showed that hyaluronidase-induced phosphorylation of p38 and Erk1/2, and that TNF-α-mediated phosphorylation of p38 and Erk1/2 was clearly reduced by HA addition. In degenerating human IVD samples, immunohistochemistry for hyaluronidase showed that the expression of hyaluronidases including HYAL1, HYAL2, and cell migration-inducing protein (CEMIP) tended to increase in accordance with IVDD. In particular, HYAL1 showed statistically significant differences. In vitro study also confirmed a similar phenomenon that TNF-α treatment increased both messenger RNA and protein expression in both cell types. Our results demonstrated that HA could potentially suppress IVDD by regulating p38 and Erk1/2 pathways, and that the expression of HYAL1 was correlated with IVDD progression. These findings indicated that HYAL1 would be a potential molecular target for suppressing IVDD by controlling HA metabolism.

Human dental pulp cells (HDPCs) play an important role in pulpitis. Semaphorin3A (Sema3A), which is an axon guidance molecule, is a member of the secretory semaphorin family. Recently, Sema3A has been reported to be an osteoprotective factor and to be involved in the immune response. However, the role of Sema3A in dental pulp inflammation remains unknown. The aim of this study was to reveal the existence of Sema3A in human dental pulp tissue and the effect of Sema3A which is released from tumor necrosis factor (TNF)-α-stimulated HDPCs on production of proinflammatory cytokines, such as interleukin (IL)-6 and CXC chemokine ligand 10 (CXCL10), from HDPCs stimulated with TNF-α. Sema3A was detected in inflamed pulp as compared to normal pulp. HDPCs expressed Neuropilin-1(Nrp1) which is Sema3A receptor. TNF-α increased the levels of IL-6 and CXCL10 in HDPCs in time-dependent manner. Sema3A inhibited production of these two cytokines from TNF-α-stimulated HDPCs. TNF-α induced soluble Sema3A production from HDPCs. Moreover, antibody-based neutralization of Sema3A further promoted production of IL-6 and CXCL10 from TNF-α-stimulated HDPCs. Sema3A inhibited nuclear factor (NF)-κB P65 phosphorylation and inhibitor κBα degradation in TNF-α-stimulated HDPCs. These results indicated that Sema3A is induced in human dental pulp, and TNF-α acts on HDPCs to produce Sema3A, which partially inhibits the increase in IL-6 and CXCL10 production induced by TNF-α, and that the inhibition leads to suppression of NF-κB activation. Therefore, it is suggested that Sema3A may regulate inflammation in dental pulp and be novel antiinflammatory target molecule for pulpitis.