Neuropeptides: important regulators of joint homeostasis

Confirmation of pain-related neuromodulation mechanism of Bushen Zhuangjin Decoction on knee osteoarthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Bushen Zhuangjin Decoction (BZD) are an herbal compound commonly used to treat osteoarthritis (OA) in China.

AIM OF THE STUDY

This study aimed to verify the mechanism of Bushen Zhuangjin Decoction in relieving the pain of knee osteoarthritis.

MATERIALS AND METHODS

Network pharmacology evaluation was used to discover the potential targets of BZD to relieve pain in KOA. The therapeutic effects of BZD treatment on KOA pain using histomorphology, behavioral assessments, suspension chip analysis, and ultra-high performance liquid chromatography/tandem mass spectrometry (UHPLC-MS/MS) assays. The functional magnetic resonance imaging was used to explore the effects of BZD treatment on brain function associated to KOA.

RESULTS

Network pharmacological analysis revealed the association between the analgesic effect of BZD on KOA and the pain signaling neurotransmitter 5-HT. Subsequently, we conducted experiments to verify the therapeutic effect of BZD on pain in KOA animal models. Behavioral tests demonstrated that the pain threshold of knee osteoarthritis rats decreased in PWT and PWL, but BZD was able to increase the pain threshold. Histopathological staining indicated thinning of the cartilage layer and sparse trabeculae in the subchondral bone. Suspension chip analysis revealed a significant increase in pro-inflammatory factors of IL-1α, IL-5, IL-12, IL-17A, RANTES, TNF-α and M-CSF in KOA, along with a significant decrease in anti-inflammatory factor of IL-13. However, BZD treatment decreased the expression of pro-inflammatory factors and increased the content of anti-inflammatory factor. UHPLC-MS/MS analysis showed a significant decrease in the serum levels of GABA, E, GSH, Kyn, Met, and VMA in KOA, which were significantly increased by BZD. Conversely, the serum levels of TrpA, TyrA, Spd, and BALa were significantly increased in KOA and significantly decreased by BZD. ELISA and Western blot analysis showed increased expression of subchondral bone pain-related neuropeptides SP, CGRP, TH, NPY, VEGFA, 5-HT3 in KOA, which were decreased in BZD. Functional magnetic resonance imaging demonstrated that BZD exerts its therapeutic effect on KOA by modulating the activity and functional connections of the cortex, hypothalamus, and hippocampus.

CONCLUSIONS

This study confirmed the significant role of pain-related neuromodulation mechanisms in the analgesic therapy of BZD and provides a theoretical foundation for using BZD as a traditional Chinese medical treatment for KOA pain.

Treatment of knee cartilage lesions in 2024: From hyaluronic acid to regenerative medicine

Abstract

Intact articular cartilage plays a vital role in joint homeostasis. Local cartilage repairs, where defects in the cartilage matrix are filled in and sealed to congruity, are therefore important treatments to restore a joint equilibrium. The base for all cartilage repairs is the cells; either chondrocytes or chondrogeneic cells from bone, synovia and fat tissue. The surgical options include bone marrow stimulation techniques alone or augmented with scaffolds, chondrogeneic cell implantations and osteochondral auto- or allografts. The current trend is to choose one-stage procedures being easier to use from a regulatory point of view. This narrative review provides an overview of the current nonoperative and surgical options available for the repair of various cartilage lesions.

Level of Evidence

Level IV.

Face and Predictive Validity of MI-RAT (Montreal Induction of Rat Arthritis Testing), a Surgical Model of Osteoarthritis Pain in Rodents Combined with Calibrated Exercise

Validating animal pain models is crucial to enhancing translational research and response to pharmacological treatment. This study investigated the effects of a calibrated slight exercise protocol alone or combined with multimodal analgesia on sensory sensitivity, neuroproteomics, and joint structural components in the MI-RAT model. Joint instability was induced surgically on day (D) 0 in female rats (N = 48) distributed into sedentary-placebo, exercise-placebo, sedentary-positive analgesic (PA), and exercise-PA groups. Daily analgesic treatment (D3-D56) included pregabalin and carprofen. Quantitative sensory testing was achieved temporally (D-1, D7, D21, D56), while cartilage alteration (modified Mankin's score (mMs)) and targeted spinal pain neuropeptide were quantified upon sacrifice. Compared with the sedentary-placebo (presenting allodynia from D7), the exercise-placebo group showed an increase in sensitivity threshold (p < 0.04 on D7, D21, and D56). PA treatment was efficient on D56 (p = 0.001) and presented a synergic anti-allodynic effect with exercise from D21 to D56 (p < 0.0001). Histological assessment demonstrated a detrimental influence of exercise (mMs = 33.3%) compared with sedentary counterparts (mMs = 12.0%; p < 0.001), with more mature transformations. Spinal neuropeptide concentration was correlated with sensory sensitization and modulation sites (inflammation and endogenous inhibitory control) of the forced mobility effect. The surgical MI-RAT OA model coupled with calibrated slight exercise demonstrated face and predictive validity, an assurance of higher clinical translatability.

Rehmannia alcohol extract inhibits neuropeptide secretion and alleviates osteoarthritis pain through cartilage protection

Osteoarthritis (OA) is a common joint disease characterized by chronic pain, and the perception of pain is closely associated with brain function and neuropeptide regulation. Rehmannia is common plant herb with anti-inflammatory and analgesic properties that is used to treat OA. However, it is unclear whether Rehmannia alleviates OA-related pain via regulation of neuropeptides and brain function. We examined the pain relief regulatory pathway in OA after treatment with Rehmannia by verifying the therapeutic effect of Rehmannia alcohol extract in vivo and vitro and exploring of the potential mechanism underlying the analgesic effect of Rahmanian using functional magnetic resonance imaging and measuring neuropeptide secretion. Our results showed that Rehmannia alcohol extract and the related active ingredient, Rehmannioside D, can delay cartilage degradation and alleviate inflammation in OA rats. The Rehmannia alcohol extract can also relieve OA pain, reduce the secretion of calcitonin gene-related peptide (CGRP) and substance P (SP), and reverse the pathological changes in the cerebral cortex and hippocampus. Our research results demonstrate that Rehmannia alleviates OA pain by protecting cartilage, preventing the stimulation of inflammatory factors on neuropeptide secretion, and influencing the relevant functional areas of the brain.

Expression of Apelin in Rotator Cuff Tears and Examination of Its Regulatory Mechanism: A Translational Study

OBJECTIVES

Inflammatory mediators play important roles in the pain associated with rotator cuff tears (RCTs), but their underlying mechanisms are unclear. Apelin, a neuropeptide, is upregulated under inflammatory conditions and possibly contributes to pain induced by rotator cuff tears. This translational study aimed to examine apelin expression and regulation by tumor necrosis factor alpha (TNF-α) in patients with RCT and in rat RCT models.

METHODS

Synovial tissues were harvested from the glenohumeral joints of the shoulders in 46 patients who underwent arthroscopic Bankart repair for recurrent shoulder dislocations (RSDs) or arthroscopic rotator cuff repair for RCTs. The harvested tissues were extracted and processed by reverse transcriptase-polymerase chain reaction (RT-PCR). Rats underwent sham or RCT surgery; the rotator cuff tissues were extracted 1, 7, 14, 28, and 56 days after surgery and analyzed for mRNA expression levels of the TNF-α and apelin using RT-PCR. The cultured rotator cuff cells (RCCs) were stimulated with TNF-α to examine their role in the regulation of apelin expression.

RESULTS

Apelin expression was higher in the RCT group than in the RSD group and significantly correlated with pain intensity. In rats, the expression was also higher in RCT. Apelin expression significantly increased during the acute and chronic phases in rats.

CONCLUSIONS

In cultured RCCs, apelin mRNA levels significantly increased after TNF-α stimulation. Apelin levels were regulated by TNF-α and were highly expressed in patients with RCT and rats in RCT models. Thus, apelin may be a new pain management target for RCTs.

Extracellular Vesicle-Mediated miR-150-3p Delivery in Joint Homeostasis: A Potential Treatment for Osteoarthritis?

Background: The disruption of joint homeostasis is a critical event during the process of joint injury in osteoarthritis (OA). As regulatory molecules, microRNAs (miRNAs) can be released from secretory cells and delivered to recipient cells through extracellular vesicles (EVs), thereby playing an important role in regulating joint homeostasis. We hypothesized that the fibroblast-like synoviocytes (FLSs) in healthy joints could release EVs enriched in miRNAs that can maintain joint homeostasis by regulating the signal transduction pathways in the joints, whereby the articular cartilage (AC) is protected from degeneration, and OA progression is delayed. Methods: Via high-throughput sequencing and qPCR, we found that miR-150-3p was enriched in the circulating EVs in healthy rats. Next, we established an in vitro cell model in which chondrocytes were cultured with (i) FLSs transfected with miR-150-3p mimics or (ii) EVs released by FLSs (FLS–EVs) inside the healthy synovial membrane (SM). The transportation mechanism from FLSs to chondrocytes was studied using the EV inhibitor GW4869, and the FLSs were transfected with a miR-150-3p mimic or inhibitor. To assess the therapeutic effect of miR-150-3p-carrying EVs (EVs-150) in vivo, healthy FLS-derived EVs (H-FLS–EVs) were injected into the tail vein of rats with OA at various stages of the pathogenesis and evaluated for the progression of OA. Results: The chondrocytes could uptake fluorescent-labeled miR-150-3p mimics and FLS–EVs, and GW4869 suppressed this uptake. The overexpression of miR-150-3p could significantly reduce the concentrations of pro-inflammatory cytokines in the cell culture medium and the expression of the miR-150-3p target T cell receptor-interacting molecule 14 (Trim14), as well as the innate immune-related factors, including nuclear factor kappa B (NF-κB) and interferon-β (IFN-β). Similarly to the in vitro findings, the miR-150-3p level in the serum EVs was significantly upregulated among the EV-treated rats. In the AC of the OA rat model injected with H-FLS–EVs, the joint degeneration was suppressed, and Type II collagen (COLII) and aggrecan (ACAN) were significantly upregulated, whereas the innate immune-related factors Trim14, NF-κB, and IFN-β were downregulated compared with the levels in the untreated OA rats. Notably, the suppression of joint degeneration was more significant when H-FLS–EVs were administered at the early stages of OA rather than the late stages. Conclusion: H-FLS–EVs protect chondrocyte function and maintain joint homeostasis by modulating the innate immune response by suppressing the Trim14/NF-κB/IFNβ axis. These effects are achieved through the EV-mediated transport of miR-150-3p from the FLSs to the chondrocytes. Our findings show that EV-mediated miR-150-3p can be used to suppress OA, thus providing a novel therapeutic strategy. Additionally, the EV-mediated miR-150-3p transport may also serve as a potential biomarker in the diagnosis, treatment, and prognosis of OA.

Treadmill exercise facilitated rotator cuff healing is coupled with regulating periphery neuropeptides expression in a murine model

Postoperative exercise has been found able to accelerate bone-tendon (B-T) healing. In this study, we systematically compared tendon-to-bone healing in mice subjected to postoperative treadmill exercise and free cage recovery in a murine rotator cuff repair model. Specifically, C57BL/6 mice underwent unilateral supraspinatus tendon (SST) detachment and repair were randomly allocated into treadmill group and control group. Treadmill group received daily treadmill running initiated from postoperative day 7 while the control group was allowed free cage activity. Mice were euthanized at postoperative 4 and 8 weeks for synchrotron radiation micro-computed tomography (SR-μCT), histology and biomechanical tests to investigate the effect of treadmill running on B-T healing. The results indicated that treadmill running initiated at day 7 postoperatively was able to accelerate B-T healing, as evidenced by better tendon-to-bone maturation and increased mechanical property. Recent studies show that peripheral neuropeptides are closely associated with musculoskeletal tissue repair. We furtherly conducted quantitative reverse transcription-polymerase chain reaction and immunofluorescence staining to investigate the temporal-spatial expression of calcitonin gene-related peptide (CGRP), substance P (SP), and peripheral neuropeptide Y (NPY) to verify whether they are related to rotator cuff healing. Our results show increased expression of CGRP, SP, and NPY at the healing site under the effect of mechanical stimulation. In conclusion, delayed postoperative exercise with moderate strength appears to accelerate the early phase of B-T healing, a process that may prove to be linked to increased expression of periphery neuropeptides known to play a role in tissue healing.

Interaction of pain and chronic inflammation

Rheumatic diseases are characterized by chronic inflammation of synovial joints and are often associated with persistent pain and increased pain sensitivity. The inflammatory process is a complex cascade of events involving several mediators, which can lead to a chronic condition of pain. Inflammation can stimulate angiogenesis, and angiogenesis can facilitate inflammation. Inflammatory pain arises from tissue damage via the sensitization of pain receptors (nociceptors). The main peripheral mechanism underlying nociceptive pain is a change in the activity of the nociceptors located in the affected anatomical structures (joints, tendons, and ligaments), which renders them more sensitive to normally painful stimuli (hyperalgesia) or normally non-painful stimuli (allodynia). Neuroimmune interaction has been considered to play an essential role in rheumatic disease. Neurogenic inflammation, which influences normal central nervous system signaling, leads to insufficient signaling/bioavailability of various cytokines. These central mechanisms play an important role in the increased pain sensitivity following inflammation and are responsible for the development of secondary hyperalgesia in regions beyond the injured tissue. Reduction of pain in rheumatic disease requires familiarity with various pain mechanisms.

Mechanisms of action of neuropeptide Y on stem cells and its potential applications in orthopaedic disorders

Musculoskeletal disorders are the leading causes of disability and result in reduced quality of life. The neuro-osteogenic network is one of the most promising fields in orthopaedic research. Neuropeptide Y (NPY) system has been reported to be involved in the regulations of bone metabolism and homeostasis, which also provide feedback to the central NPY system via NPY receptors. Currently, potential roles of peripheral NPY in bone metabolism remain unclear. Growing evidence suggests that NPY can regulate biological actions of bone marrow mesenchymal stem cells, hematopoietic stem cells, endothelial cells, and chondrocytes via a local autocrine or paracrine manner by different NPY receptors. The regulative activities of NPY may be achieved through the plasticity of NPY receptors, and interactions among the targeted cells as well. In general, NPY can influence proliferation, apoptosis, differentiation, migration, mobilization, and cytokine secretion of different types of cells, and play crucial roles in the development of bone delayed/non-union, osteoporosis, and osteoarthritis. Further basic research should clarify detailed mechanisms of action of NPY on stem cells, and clinical investigations are also necessary to comprehensively evaluate potential applications of NPY and its receptor-targeted drugs in management of musculoskeletal disorders.

Targeting Local Osteogenic and Ancillary Cells by Mechanobiologically Optimized Magnesium Scaffolds for Orbital Bone Reconstruction in Canines

Large-sized orbital bone defects have serious consequences that destroy orbital integrity and result in maxillofacial deformities and vision loss. The treatment of orbital bone defects is currently palliative and not reparative, suggesting an urgent demand for biomaterials that regenerate orbital bones. In this study, via alloying, extrusion and surface modification, we developed mechanobiologically optimized magnesium (Mg) scaffolds (Ca-P-coated Mg-Zn-Gd scaffolds, referred to as Ca-P-Mg) for the orthotopic reconstruction of large-sized orbital bone defects. At 6 months after transplanting the scaffolds to a clinically relevant canine large animal model, large-sized defects were successfully bridged by an abundance of new bone with normal mechanical properties that corresponded to gradual degradation of the implants. The osteogenic and ancillary cells, including vascular endothelial cells and trigeminal neurons, played important roles in this process. The scaffolds robustly enhanced bone marrow mesenchymal stem cell (BMSC) osteogenic differentiation. In addition, the increased angiogenesis including increased ratio of the specific endothelial subtype CD31^hi endomucin^hi (CD31^hiEmcn^hi) endothelial cells can facilitate osteogenesis. Furthermore, the scaffolds trigger trigeminal neurons via transient receptor potential vanilloid subtype 1 (Trpv1) to produce the neuropeptide calcitonin gene-related peptide (CGRP), which promotes angiogenesis and osteogenesis. Overall, our investigations revealed the efficacy of Ca-P-Mg scaffolds in healing orbital bone defects and warrant further exploration of these scaffolds for clinical applications.