Overexpression of TIMP3 inhibits discogenic pain by suppressing angiogenesis and the expression of substance P in nucleus pulposus

The pathogenesis and targeted therapies of intervertebral disc degeneration induced by cartilage endplate inflammation

Intervertebral disc degeneration (IVDD) is the leading cause of low back pain, where degeneration and death of nucleus pulposus cells within the intervertebral disc (IVD) can be obviously revealed. This degeneration can result in an imbalance in the extracellular matrix due to the loss of proteoglycans and water content, which can further lead to catabolic and anabolic dysfunction of the IVD. Recently, the dysfunction of cartilage endplate (CEP) during aging has drawn large attention due to its essential functions in contributing nutrient exchange and maintaining IVD homeostasis. Furthermore, the inflammation and disturbed homeostasis of CEP not only accelerate the degradation of nucleus pulposus extracellular matrix, but also exacerbate IVDD by causing nucleus pulposus cell death through other pathological factors. Here in this review, we summarized the possible pathological factors and the underlying mechanisms of the CEP inflammation-induced IVDD, including exosomes degeneration, CEP calcification, ferroptosis, mechanical changes, and cell senescence. Besides, changes of miRNAs, pain-related neural reflex arc and pathways associated with CEP inflammation-induced IVDD are also reviewed. In addition, new strategies specifically designed for CEP inflammation-induced IVDD are also discussed in the last section. We hope this paper can not only offer some new insights for advancing novel strategies for treating IVDD, but also serve as a valuable reference for researchers in this field.

Screening and identification of key biomarkers associated with endometriosis using bioinformatics and next-generation sequencing data analysis

Background

Endometriosis is a common cause of endometrial-type mucosa outside the uterine cavity with symptoms such as painful periods, chronic pelvic pain, pain with intercourse and infertility. However, the early diagnosis of endometriosis is still restricted. The purpose of this investigation is to identify and validate the key biomarkers of endometriosis.

Methods

Next-generation sequencing dataset GSE243039 was obtained from the Gene Expression Omnibus database, and differentially expressed genes (DEGs) between endometriosis and normal control samples were identified. After screening of DEGs, gene ontology (GO) and REACTOME pathway enrichment analyses were performed. Furthermore, a protein–protein interaction (PPI) network was constructed and modules were analyzed using the Human Integrated Protein–Protein Interaction rEference database and Cytoscape software, and hub genes were identified. Subsequently, a network between miRNAs and hub genes, and network between TFs and hub genes were constructed using the miRNet and NetworkAnalyst tool, and possible key miRNAs and TFs were predicted. Finally, receiver operating characteristic curve analysis was used to validate the hub genes.

Results

A total of 958 DEGs, including 479 upregulated genes and 479 downregulated genes, were screened between endometriosis and normal control samples. GO and REACTOME pathway enrichment analyses of the 958 DEGs showed that they were mainly involved in multicellular organismal process, developmental process, signaling by GPCR and muscle contraction. Further analysis of the PPI network and modules identified 10 hub genes, including vcam1, snca, prkcb, adrb2, foxq1, mdfi, actbl2, prkd1, dapk1 and actc1. Possible target miRNAs, including hsa-mir-3143 and hsa-mir-2110, and target TFs, including tcf3 (transcription factor 3) and clock (clock circadian regulator), were predicted by constructing a miRNA-hub gene regulatory network and TF-hub gene regulatory network.

Conclusions

This investigation used bioinformatics techniques to explore the potential and novel biomarkers. These biomarkers might provide new ideas and methods for the early diagnosis, treatment and monitoring of endometriosis.

Anti-degenerative effect of melatonin on intervertebral disc: protective contribution against inflammation, oxidative stress, apoptosis, and autophagy

Intervertebral disc (IVD) degeneration is a leading cause of lower back pain. Although the etiology of IVD degeneration (IVDD) is unclear, excessive oxidative stress, inflammation and apoptosis and disruption of autophagy play important role in the pathogenesis of IVDD. Therefore, finding a solution to mitigate these processes could stop or reduce the development of IVDD. Melatonin, a powerful antioxidant, plays an important role in regulating cartilage tissue hemostasis. Melatonin inhibits destruction of extracellular matrix (ECM) of disc. Melatonin preserves ECM contents including sox-9, aggrecan, and collagen II through inhibiting matrix degeneration enzymes such as MMP-13. These protective effects may be mediated by the inhibition of oxidative stress, inflammation and apoptosis, and regulation of autophagy in IVD cells.

Reactive Oxygen Species Mediate Low Back Pain by Upregulating Substance P in Intervertebral Disc Degeneration

Reactive oxygen species (ROS) are thought to have a strong correlation with a number of intervertebral disc (IVD) diseases. Here, we aimed to determine whether ROS represent an etiology of low back pain (LBP) during IVD degeneration. Thirty degenerated intervertebral disc samples were obtained from patients, and ROS levels were quantified using dihydroethidium (DHE) staining. The results suggested a significant correlation between the ROS level and the severity of LBP. Subsequently, a puncture-induced LBP model was established in rats, and ROS levels significantly increased compared with those in the sham surgery group, accompanied with severe puncture-induced IVD degeneration. In addition, when ROS levels were increased by H₂O₂ administration or decreased by NAC treatment, the rats showed increased or decreased LBP, respectively. Based on this evidence, we further determined that stimulation with H₂O₂ in nucleus pulposus cells (NPCs) in vivo or in vitro resulted in upregulation of substance P (SP), a peptide thought to be involved in the synaptic transmission of pain, and that the severity of LBP decreased when SP levels were increased by exogenous SP administration or neutralized via aprepitant treatment in the IVDs of rats. In conclusion, ROS are primary inducers of LBP based on clinical and animal data, and the mechanism involves ROS stimulation of NPCs to secrete SP, which is a critical neurotransmitter peptide, to promote LBP in IVDs. Therefore, reducing the level of ROS with specific drugs and inhibiting SP may be alternative methods to treat LBP in the clinic.

Melatonin prevents the binding of vascular endothelial growth factor to its receptor and promotes the expression of extracellular matrix-associated genes in nucleus pulposus cells

The mechanisms of intervertebral disc degeneration (IDD) involve numerous factors, including loss of the extracellular matrix (ECM) and vascular ingrowth. Melatonin has been reported to protect intervertebral discs (IVDs) from degeneration and to exert a potential anti-angiogenic effect. The aim of the present study was to investigate the anti-angiogenic and anabolic effects of melatonin in IVDs. Human nucleus pulposus (NP) and degenerative nucleus pulposus (DNP) cells were isolated and treated with melatonin. The results indicated that melatonin promoted ECM synthesis and NP cell proliferation. In addition, an NP/DNP and human umbilical vein endothelial cell (HUVEC) co-culture model was used to investigate the anti-angiogenesis effect of melatonin. Melatonin was indicated to suppress tube formation and migration of HUVECs in culture with NP cell-conditioned medium, as well as in an NP cell co-culture model. Fluorescence-labeled vascular endothelial growth factor (VEGF) was used to study the binding between VEGF and its receptor. The results of the present study indicated that melatonin exerts an angiogenic effect via inhibition of the binding of VEGF to its receptor in HUVECs. Taken together, these results suggest that melatonin is a potential agent to prevent IDD.

Novel Analgesics with Peripheral Targets

A limited number of peripheral targets generate pain. Inflammatory mediators can sensitize these. The review addresses targets acting exclusively or predominantly on sensory neurons, mediators involved in inflammation targeting sensory neurons, and mediators involved in a more general inflammatory process, of which an analgesic effect secondary to an anti-inflammatory effect can be expected. Different approaches to address these systems are discussed, including scavenging proinflammatory mediators, applying anti-inflammatory mediators, and inhibiting proinflammatory or facilitating anti-inflammatory receptors. New approaches are contrasted to established ones; the current stage of progress is mentioned, in particular considering whether there is data from a molecular and cellular level, from animals, or from human trials, including an early stage after a market release. An overview of publication activity is presented, considering a IuPhar/BPS-curated list of targets with restriction to pain-related publications, which was also used to identify topics.

Sensory neurons directly promote angiogenesis in response to inflammation via substance P signaling

Blood vessels and nerves travel together to supply most tissues in the body. However, there is a knowledge gap in the mechanisms underlying the direct regulation of angiogenesis by nerves. In the current study, we examined the regulation of angiogenesis by sensory nerves in response to inflammation using the cornea, a normally avascular and densely innervated ocular tissue, as a model. We used desiccating stress as an inflammatory stimulus in vivo and found that sub-basal and epithelial nerve densities in the cornea were reduced in dry eye disease (DED). We established a co-culture system of trigeminal ganglion sensory neurons and vascular endothelial cells (VEC) and found that neurons isolated from mice with DED directly promoted VEC proliferation and tube formation compared with normal controls. In addition, these neurons expressed and secreted higher levels of substance P (SP), a proinflammatory neuropeptide. SP potently promoted VEC activation in vitro and blockade of SP signaling with spantide I, an antagonist of SP receptor Neurokinin-1, significantly reduced corneal neovascularization in vivo. Spantide I and siRNA knockdown of SP abolished the promotion of VEC activation by DED neurons in vitro. Taken together, our data suggested that sensory neurons directly promote angiogenesis via SP signaling in response to inflammation in the cornea.