Anti-inflammatory and Chondroprotective Effects of Platelet-derived Growth Factor-BB on Osteoarthritis Rat Models

Genetic insights into the causal linkage between systemic inflammatory regulators and frailty

OBJECTIVES

Previous studies have suggested the associations between systemic inflammation and the risk of frailty, but causal relationships between them remain not well established. We conducted a bi-directional Mendelian randomization (MR) analysis to investigate the causal links between systemic inflammatory regulators and frailty.

METHODS

Genetic variants associated with systemic inflammatory regulators were obtained from a comprehensive genetic study on 41 circulating cytokines, such as interleukin-4 (IL-4), eotaxin, and macrophage inflammatory protein-1β (MIP1β). We integrated summary-level data on frailty from two independent genetic studies on frailty index (FI) and Fried frailty score (FFS). The inverse-variance weighted method was used to assess the causal estimate. Sensitivity and heterogeneity analysis was performed to evaluate the stability of the estimates. The false discovery rate (FDR) method was used for P value adjustment of multiple comparisons.

RESULTS

Genetically elevated levels of MIP1β and decreased levels of eotaxin were suggestively associated with increased FI (MIP1β: β = 0.016, Praw = 0.006, PFDR = 0.083; eotaxin: β = -0.030, Praw = 0.007, PFDR = 0.083) and FFS (MIP1β: β = 0.008, Praw = 0.027, PFDR = 0.247; eotaxin: β = -0.015, Praw = 0.014, PFDR = 0.247). In contrast, genetically predicted FI was suggestively associated with decreased levels of IL-4 (β = -0.395, Praw = 0.040, PFDR = 0.638) and platelet-derived growth factor BB (PDGF-BB, β = -0.385, Praw = 0.047, PFDR = 0.638) and increased levels of stem cell factor (SCF, β = 0.527, Praw = 0.005, PFDR = 0.204). Similar results were obtained from different sensitivity analysis.

CONCLUSIONS

The present study demonstrates that increased MIP-1β levels and decreased eotaxin levels might lead to a higher risk of frailty, whereas frailty might reduce the levels of IL-4 and PDGF-BB and increase the levels of SCF.

Mechanisms and applications of the regenerative capacity of platelets-based therapy in knee osteoarthritis

Osteoarthritis (OA) is the most prevalent joint disease in the elderly population and its substantial morbidity and disability impose a heavy economic burden on patients and society. Knee osteoarthritis (KOA) is the most common subtype of OA, which is characterized by damage to progressive articular cartilage, synovitis, and subchondral bone sclerosis. Most current treatments for OA are palliative, primarily aim at symptom management, and do not prevent the progression of the disease or restore degraded cartilage. The activation of α-granules in platelets releases various growth factors that are involved in multiple stages of tissue repair, suggesting potential for disease modification. In recent years, platelet-based therapies, such as platelet-rich plasma, platelet-rich fibrin, and platelet lysates, have emerged as promising regenerative treatments for KOA, but their related effects and mechanisms are still unclear. Therefore, this review aims to summarize the biological characteristics and functions of platelets, classify the products of platelet-based therapy and related preparation methods. Moreover, we summarize the basic research of platelet-based regeneration strategies for KOA and discuss the cellular effects and molecular mechanisms. Further, we describe the general clinical application of platelet-based therapy in the treatment of KOA and the results of the meta-analysis of randomized controlled trials.

Crosstalk between bone and brain in Alzheimer's disease: Mechanisms, applications, and perspectives

Alzheimer's disease (AD) is a neurodegenerative disease that involves multiple systems in the body. Numerous recent studies have revealed bidirectional crosstalk between the brain and bone, but the interaction between bone and brain in AD remains unclear. In this review, we summarize human studies of the association between bone and brain and provide an overview of their interactions and the underlying mechanisms in AD. We review the effects of AD on bone from the aspects of AD pathogenic proteins, AD risk genes, neurohormones, neuropeptides, neurotransmitters, brain-derived extracellular vesicles (EVs), and the autonomic nervous system. Correspondingly, we elucidate the underlying mechanisms of the involvement of bone in the pathogenesis of AD, including bone-derived hormones, bone marrow-derived cells, bone-derived EVs, and inflammation. On the basis of the crosstalk between bone and the brain, we propose potential strategies for the management of AD with the hope of offering novel perspectives on its prevention and treatment. HIGHLIGHTS: The pathogenesis of AD, along with its consequent changes in the brain, may involve disturbing bone homeostasis. Degenerative bone disorders may influence the progression of AD through a series of pathophysiological mechanisms. Therefore, relevant bone intervention strategies may be beneficial for the comprehensive management of AD.

Circulating cytokines levels and osteoarthritis: A Mendelian randomization study

BACKGROUND

Previous traditional observational studies have suggested the contribution of several cytokines and growth factors to the development of osteoarthritis (OA). This study aimed to determine the association of circulating cytokine and growth factor levels with OA.

METHODS

We used two-sample Mendelian randomization (MR) to explore the causality between circulating cytokine and growth factor levels and OA [including knee or hip OA (K/HOA), knee OA (KOA), and hip OA (HOA)]. Summary level data for circulating cytokine and growth factor levels were sourced from a genome-wide association study (GWAS) involving 8,293 participants of Finnish ancestry. Single-nucleotide polymorphisms related to K/HOA (39,427 cases and 378,169 controls), KOA (24,955 cases and 378,169 controls), and HOA (15,704 cases and 378,169 controls) were obtained from a previous GWAS. The inverse variance weighted (IVW) method was primarily used for our MR analysis. For exposures to only one relevant SNP as IV, we used the Wald ratio as the major method to assess causal effects. We also conducted a series of sensitivity analyses to improve the robustness of the results.

RESULTS

Circulating vascular endothelial growth factor levels were suggestively associated with an increased risk of K/HOA (odds ratio (OR) = 1.034; 95 % confidence interval (CI) = 1.013-1.055; P = 0.001), KOA (OR = 1.034; 95 % CI = 1.014-1.065; P = 0.002), and HOA (OR = 1.039; 95 % CI = 1.003-1.067; P = 0.034). Circulating interleukin (IL)-12p70 levels was suggestively associated with K/HOA (OR = 1.047; 95 % CI = 1.018-1.077; P = 0.001), KOA (OR = 1.058; 95 % CI = 1.022-1.095; P = 0.001), and HOA (OR = 1.044; 95 % CI = 1.000-1.091; P = 0.048). Circulating IL-18 levels were suggestively associated with HOA (OR = 1.068; 95 % CI = 1.014-1.125; P = 0.012). However, limited evidence exists to support causal genetic relationships between other circulating cytokines, growth factor levels and K/HOA, KOA, and HOA.

CONCLUSIONS

Our MR analysis provides suggestive evidence of causal relationships between circulating cytokines and growth factors levels and OA, providing new insights into the etiology of OA.

Clinical Outcome of Multiple Platelet-Rich Plasma Injection and Correlation with PDGF-BB in the Treatment of Knee Osteoarthritis

(1) Background: Current treatments for knee osteoarthritis (KOA), such as intra-articular corticosteroids or hyaluronic acid (HA) injections, are controversial due to their ineffectiveness in preventing disease progression. Platelet-rich plasma (PRP) has become a promising and possible treatment for KOA. It is thought to enhance articular cartilage regeneration and reduce OA-related impairment. PRP contains growth factors such as PDGF-BB, which stimulates growth and inhibits joint damage. Based on numerous studies, after a certain amount of time, it was found that multiple PRP treatments reduced pain more than a single injection. This study evaluates the efficacy of multiple PRP (m-PRP) injections compared to multiple HA (m-HA) injections for KOA treatment, focusing on their correlation with PDGF-BB levels. (2) Methods: In this single-center, open-label, randomized, comparative clinical trial, 30 KOA patients received m-PRP and m-HA injections. VAS and WOMAC were used to evaluate clinical outcomes and PDGF-BB concentrations. (3) Results: The study analysis revealed a statistically significant reduction in pain indices. In both the m-PRP and m-HA groups after 12 weeks, m-PRP showed superior results. PDGF-BB concentrations also increased, with a strong negative correlation and statistical significance using Spearman's rho. (4) Conclusions: Multiple PRP injections are safe and associated with elevated PDGF-BB, reduced VAS and WOMAC scores, providing the potential for articular cartilage regeneration and inhibiting knee osteoarthritis progression.

Role of epigenetics and the transcription factor Sp1 in the expression of the D prostanoid receptor 1 in human cartilage

D prostanoid receptor 1 (DP1), a prostaglandin D2 receptor, plays a central role in the modulation of inflammation and cartilage metabolism. We have previously shown that activation of DP1 signaling downregulated catabolic responses in cultured chondrocytes and was protective in mouse osteoarthritis (OA). However, the mechanisms underlying its transcriptional regulation in cartilage remained poorly understood. In the present study, we aimed to characterize the human DP1 promoter and the role of DNA methylation in DP1 expression in chondrocytes. In addition, we analyzed the expression level and methylation status of the DP1 gene promoter in normal and OA cartilage. Deletion and site-directed mutagenesis analyses identified a minimal promoter region (-250/-120) containing three binding sites for specificity protein 1 (Sp1). Binding of Sp1 to the DP1 promoter was confirmed using electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays. Treatment with the Sp1 inhibitor mithramycin A reduced DP1 promoter activity and DP1 mRNA expression. Inhibition of DNA methylation by 5-Aza-2'-deoxycytidine upregulated DP1 expression, and in vitro methylation reduced the DP1 promoter activity. Neither the methylation status of the DP1 promoter nor the DP1 expression level were different between normal and OA cartilage. In conclusion, our results suggest that the transcription factor Sp1 and DNA methylation are important determinants of DP1 transcription regulation. They also suggest that the methylation status and expression level of DP1 are not altered in OA cartilage. These findings will improve our understanding of the regulatory mechanisms of DP1 transcription and may facilitate the development of intervention strategies involving DP1.

Effects and action mechanisms of individual cytokines contained in PRP on osteoarthritis

Osteoarthritis (OA) is defined as a degenerative joint disease that can affect all tissues of the joint, including the articular cartilage, subchondral bone, ligaments capsule, and synovial membrane. The conventional nonoperative treatments are ineffective for cartilage repair and induce only symptomatic relief. Platelet-rich plasma (PRP) is a platelet concentrate derived from autologous whole blood with a high concentration of platelets, which can exert anti-inflammatory and regenerative effects by releasing multiple growth factors and cytokines. Recent studies have shown that PRP exhibits clinical benefits in patients with OA. However, high operational and equipment requirements greatly limit the application of PRP to OA treatment. Past studies have indicated that high-concentration PRP growth factors and cytokines may be applied as a commercial replacement for PRP. We reviewed the relevant articles to summarize the feasibility and mechanisms of PRP-based growth factors in OA. The available evidence suggests that transforming growth factor-α and β, platelet-derived growth factors, epidermal growth factor, insulin-like growth factor-1, and connective tissue growth factors might benefit OA, while vascular endothelial growth factor, tumor necrosis factor-α, angiopoietin-1, and stromal cell derived factor-1α might induce negative effects on OA. The effects of fibroblast growth factor, hepatocyte growth factor, platelet factor 4, and keratinocyte growth factor on OA remain uncertain. Thus, it can be concluded that not all cytokines released by PRP are beneficial, although the therapeutic action of PRP has a valuable potential to improve.

Benzoylaconitine Alleviates Progression of Psoriasis via Suppressing STAT3 Phosphorylation in Keratinocytes

Psoriasis is a chronic and multifactorial skin disease which is caused by inflammatory infiltrates, keratinocyte hyperproliferation, and accumulation of immune cells. As part of the Aconitum species, Benzoylaconitine (BAC) shows potential antiviral, anti-tumor, and anti-inflammatory effects. In this study, we investigated the effects and mechanisms of BAC on tumor necrosis factor-alpha (TNF-α)/LPS-induced HaCaT keratinocytes in a imiquimod(IMQ)-induced mice model. The results showed that BAC could relieve the symptoms of psoriasis by inhibiting cell proliferation, the release of inflammatory factors, and the accumulation of Th17 cells, while no obvious effect on cell viability and safety was observed both in vitro and in vivo. Additionally, BAC can markedly inhibit the protein and mRNA levels of inflammatory cytokines in TNF-α/LPS-induced HaCaT keratinocytes by inhibiting the phosphorylation of STAT3. In brief, our data indicated that BAC could alleviate the progression of psoriasis and may be a potential therapeutic agent for treating psoriasis in clinical practice.

Potential of secretome of human fetal cartilage progenitor cells as disease modifying agent for osteoarthritis

AIMS

Osteoarthritis (OA) is caused by an imbalance in the synthesis and degradation of cartilage tissue by chondrocytes. Therefore, a therapeutic agent for OA patients that can positively affect both synthesis and degradation is needed. However, current nonsurgical treatments for OA can barely achieve satisfactory long-term outcomes in cartilage repair. Human fetal cartilage progenitor cells-secretome (ShFCPC) has shown potent anti-inflammatory and tissue-repair effects; however, its underlying mechanisms and effects on OA have rarely been systematically elucidated. This study aims to analyze and evaluate the potency of ShFCPC in modifying OA process.

MAIN METHODS

Herein, secreted proteins enriched in ShFCPC have been characterized, and their biological functions both in vitro and in vivo in an OA model are compared with those of human bone marrow-derived mesenchymal stem cells-secretome (ShBMSC) and hyaluronan (HA).

KEY FINDINGS

Secretome analysis has shown that ShFCPC is significantly enriched with extracellular matrix molecules involved in many effects of cellular processes required for homeostasis during OA progression. Biological validation in vitro has shown that ShFCPC protects chondrocyte apoptosis by suppressing the expression of inflammatory mediators and matrix-degrading proteases and promotes the secretion of pro-chondrogenic cytokines in lipopolysaccharide-induced coculture of human chondrocytes and SW982 synovial cells compared with ShBMSC. Moreover, in a rat OA model, ShFCPC protects articular cartilage by reducing inflammatory cell infiltration and M1/M2 macrophage ratio in the synovium, which directly contributes to an increase in immunomodulatory atmosphere and enhances cartilage repair compared to ShBMSC and HA.

SIGNIFICANCE

Our findings support clinical translations of ShFCPC as a novel agent for modifying OA process.