Recombinant human proteoglycan 4 lowers inflammation and atherosclerosis susceptibility in female low-density lipoprotein receptor knockout mice.

Recombinant human proteoglycan 4 (rhPRG4) is a macromolecular mucin-like glycoprotein that is classically studied as a lubricant within eyes and joints. Given that endogenously produced PRG4 is present within atherosclerotic lesions and genetic PRG4 deficiency increases atherosclerosis susceptibility in mice, in the current study we investigated the anti-atherogenic potential of chronic rhPRG4 treatment. Female low-density lipoprotein receptor knockout mice were fed an atherogenic Western-type diet for 6 weeks and injected three times per week intraperitoneally with 0.5 mg rhPRG4 or PBS as control. Treatment with rhPRG4 was associated with a small decrease in plasma-free cholesterol levels, without a change in cholesteryl ester levels. A marked increase in the number of peritoneal foam cells was detected in response to the peritoneal rhPRG4 administration, which could be attributed to elevated peritoneal leukocyte MSR1 expression levels. However, rhPRG4-treated mice exhibited significantly smaller aortic root lesions of 278 ± 21 × 103 µm2 compared with 339 ± 15 × 103 µm2 in the aortic root of control mice. The overall decreased atherosclerosis susceptibility coincided with a shift in the monocyte and macrophage polarization states towards the patrolling and anti-inflammatory M2-like phenotypes, respectively. Furthermore, rhPRG4 treatment significantly reduced macrophage gene expression levels as well as plasma protein levels of the pro-inflammatory/pro-atherogenic cytokine TNF-alpha. In conclusion, we have shown that peritoneal administration and subsequent systemic exposure to rhPRG4 beneficially impacts the inflammatory state and reduces atherosclerosis susceptibility in mice. Our findings highlight that PRG4 is not only a lubricant but also acts as an anti-inflammatory agent. KEY POINTS: Endogenously produced proteoglycan 4 is found in atherosclerotic lesions and its genetic deficiency in mice is associated with enhanced atherosclerosis susceptibility. In this study we investigated the anti-atherogenic potential of chronic treatment with recombinant human PRG4 in hypercholesterolaemic female low-density lipoprotein receptor knockout mice. We show that recombinant human PRG4 stimulates macrophage foam cell formation, but also dampens the pro-inflammatory state of monocyte/macrophages, eventually leading to a significant reduction in plasma TNF-alpha levels and a lowered atherosclerosis susceptibility. Our findings highlight that peritoneal recombinant human PRG4 treatment can execute effects both locally and systemically and suggest that it will be of interest to study whether rhPRG4 treatment is also able to inhibit the progression and/or induce regression of previously established atherosclerotic lesions.

Astrocyte-like subpopulation of NG2 glia in the adult mouse cortex exhibits characteristics of neural progenitor cells.

Glial cells expressing neuron-glial antigen 2 (NG2), also known as oligodendrocyte progenitor cells (OPCs), play a critical role in maintaining brain health. However, their ability to differentiate after ischemic injury is poorly understood. The aim of this study was to investigate the properties and functions of NG2 glia in the ischemic brain. Using transgenic mice, we selectively labeled NG2-expressing cells and their progeny in both healthy brain and after focal cerebral ischemia (FCI). Using single-cell RNA sequencing, we classified the labeled glial cells into five distinct subpopulations based on their gene expression patterns. Additionally, we examined the membrane properties of these cells using the patch-clamp technique. Of the identified subpopulations, three were identified as OPCs, whereas the fourth subpopulation had characteristics indicative of cells likely to develop into oligodendrocytes. The fifth subpopulation of NG2 glia showed astrocytic markers and had similarities to neural progenitor cells. Interestingly, this subpopulation was present in both healthy and post-ischemic tissue; however, its gene expression profile changed after ischemia, with increased numbers of genes related to neurogenesis. Immunohistochemical analysis confirmed the temporal expression of neurogenic genes and showed an increased presence of NG2 cells positive for Purkinje cell protein-4 at the periphery of the ischemic lesion 12 days after FCI, as well as NeuN-positive NG2 cells 28 and 60 days after injury. These results suggest the potential development of neuron-like cells arising from NG2 glia in the ischemic tissue. Our study provides insights into the plasticity of NG2 glia and their capacity for neurogenesis after stroke.

Scale-Dependent Rheology of Synovial Fluid Lubricating Macromolecules.

Synovial fluid (SF) is the complex biofluid that facilitates the exceptional lubrication of articular cartilage in joints. Its primary lubricating macromolecules, the linear polysaccharide hyaluronic acid (HA) and the mucin-like glycoprotein proteoglycan 4 (PRG4 or lubricin), interact synergistically to reduce boundary friction. However, the precise manner in which these molecules influence the rheological properties of SF remains unclear. This study aimed to elucidate this by employing confocal microscopy and multiscale rheometry to examine the microstructure and rheology of solutions containing recombinant human PRG4 (rhPRG4) and HA. Contrary to previous assumptions of an extensive HA-rhPRG4 network, it is discovered that rhPRG4 primarily forms stiff, gel-like aggregates. The properties of these aggregates, including their size and stiffness, are found to be influenced by the viscoelastic characteristics of the surrounding HA matrix. Consequently, the rheology of this system is not governed by a single length scale, but instead responds as a disordered, hierarchical network with solid-like rhPRG4 aggregates distributed throughout the continuous HA phase. These findings provide new insights into the biomechanical function of PRG4 in cartilage lubrication and may have implications in the development of HA-based therapies for joint diseases like osteoarthritis.

Chondroitin sulfate proteoglycan 4: An attractive target for antibody-based immunotherapy.

Multifunctional molecules involved in tumor progression and metastasis have been identified as valuable targets for immunotherapy. Among these, chondroitin sulfate proteoglycan 4 (CSPG4), a significant tumor cell membrane-bound proteoglycan, has emerged as a promising target, especially in light of advances in chimeric antigen receptor (CAR) T-cell therapy. The profound bioactivity of CSPG4 and its role in pivotal processes such as tumor proliferation, migration, and neoangiogenesis underline its therapeutic potential. We reviewed the molecular intricacies of CSPG4, its functional attributes within tumor cells, and the latest clinical-translational advances targeting it. Strategies such as blocking monoclonal antibodies, conjugate therapies, bispecific antibodies, small-molecule inhibitors, CAR T-cell therapies, trispecific killer engagers, and ribonucleic acid vaccines against CSPG4 were assessed. CSPG4 overexpression in diverse tumors and its correlation with adverse prognostic outcomes emphasize its significance in cancer biology. These findings suggest that targeting CSPG4 offers a promising avenue for future cancer therapy, with potential synergistic effects when combined with existing treatments.

PRG4 represses the genesis and metastasis of osteosarcoma by inhibiting PDL1 expression.

BACKGROUND: Osteosarcoma is originated from skeletal system. Recombinant human proteoglycan 4 (rhPRG4) can inhibit cell proliferation and migration in multiple cancers. This research is designed to dig out the role and mechanism of PRG4 in osteosarcoma. METHODS: Human osteosarcoma cell lines, MG63 and 143B, were transfected with programmed death 1 (PD-L1) overexpression vectors and/or treated with 20, 50, and 100 µg/mL rhPRG4, followed by the determination of cell viability, colony formation, sphere formation, invasion, migration, apoptosis, and the expressions of matrix metalloproteinases (MMPs), PD-L1 and apoptosis-related proteins. Tumor-bearing mouse models were constructed by injection of 143B cells and treatment of anti-PD-L1 antibody and/or adenovirus PRG4 (AdPRG4). Tumor volume was monitored, and immunohistochemical location of Ki67 was performed. Expressions of MMPs, transforming growth factor-ß (TGF-ß), PD-L1, and epithelial mesenchymal transition (EMT)-related proteins were measured in tumors. RESULTS: RhPRG4 (20, 50, and 100 µg/mL) inhibited the viability, colony formation, sphere formation, invasion, migration, and the expressions of MMP2, MMP9 and Bcl2 in osteosarcoma cells, while promoting cell apoptosis as well as Bax and c-caspase3 expressions, at a dose-dependent manner; by contrast, PD-L1 overexpression reversed the above effects of 100 µg/mL rhPRG4. AdPRG4 or anti-PD-L1 antibody decreased tumor volume, number of pulmonary metastasis nodule, Ki67 location, and expressions of TGF-ß, PD-L1, MMP2, MMP9, Vimentin, and Snail, but increased E-cadherin expression in tumor cells. Moreover, anti-PD-L1 antibody and AdPRG4 together functioned more effectively than them alone in reducing tumor burden. CONCLUSION: PRG4 represses the genesis and metastasis of osteosarcoma via inhibiting PD-L1 expression, and AdPRG4 enhances the effectiveness of anti-PD-L1 therapy.

The Actin Cytoskeleton as a Regulator of Proteoglycan 4.

OBJECTIVE: The superficial zone (SZ) of articular cartilage is responsible for distributing shear forces for optimal cartilage loading and contributes to joint lubrication through the production of proteoglycan 4 (PRG4). PRG4 plays a critical role in joint homeostasis and is chondroprotective. Normal PRG4 production is affected by inflammation and irregular mechanical loading in post-traumatic osteoarthritis (PTOA). THe SZ chondrocyte (SZC) phenotype, including PRG4 expression, is regulated by the actin cytoskeleton in vitro. There remains a limited understanding of the regulation of PRG4 by the actin cytoskeleton in native articular chondrocytes. The filamentous (F)-actin cytoskeleton is a potential node in crosstalk between mechanical stimulation and cytokine activation and the regulation of PRG4 in SZCs, therefore developing insights in the regulation of PRG4 by actin may identify molecular targets for novel PTOA therapies. MATERIALS AND METHODS: A comprehensive literature search on PRG4 and the regulation of the SZC phenotype by actin organization was performed. RESULTS: PRG4 is strongly regulated by the actin cytoskeleton in isolated SZCs in vitro. Biochemical and mechanical stimuli have been characterized to regulate PRG4 and may converge upon actin cytoskeleton signaling. CONCLUSION: Actin-based regulation of PRG4 in native SZCs is not fully understood and requires further elucidation. Understanding the regulation of PRG4 by actin in SZCs requires an in vivo context to further potential of leveraging actin arrangement to arthritic therapeutics.

Shotgun Proteomics Links Proteoglycan-4+ Extracellular Vesicles to Cognitive Protection in Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder lacking reliable biomarkers for early diagnosis and disease progression monitoring. This study aimed to identify the novel biomarkers in plasmatic extracellular vesicles (EVs) isolated from ALS patients and healthy controls (HCs). A total of 61 ALS patients and 30 age-matched HCs were enrolled in the study and the protein content of circulating EVs was analyzed by shotgun proteomics. The study was divided into a discovery phase (involving 12 ALS and 12 HC patients) and a validation one (involving 49 ALS and 20 HC patients). In the discovery phase, more than 300 proteins were identified, with 32 proteins showing differential regulation in ALS patients compared to HCs. In the validation phase, over 400 proteins were identified, with 20 demonstrating differential regulation in ALS patients compared to HCs. Notably, seven proteins were found to be common to both phases, all of which were significantly upregulated in EVs from ALS patients. Most of them have previously been linked to ALS since they have been detected in the serum or cerebrospinal fluid of ALS patients. Among them, proteoglycan (PRG)-4, also known as lubricin, was of particular interest since it was significantly increased in ALS patients with normal cognitive and motor functions. This study highlights the significance of EVs as a promising avenue for biomarker discovery in ALS. Moreover, it sheds light on the unexpected role of PRG-4 in relation to cognitive status in ALS patients.

Study on the Relationship between CLDN10 and CSPG4 Levels Expression of Tissue and Clinicopathological Characteristics and Prognosis in Non-small Cell Lung Cancer / 现代检验医学杂志

Objective To investigate the relationship between the expression of claudin 10(CLDN10)and chondroitin sulfate proteoglycan 4(CSPG4)of tissue and clinicopathologic characteristics and prognosis in non-small cell lung cancer(NSCLC).Methods A total of 136 NSCLC patients who underwent surgery in Taizhou People's Hospital,Nanjing Medical University from January 2017 to April 2018 were randomly selected as the study subjects,and these subjects were grouped into survival group(n=63)and death group(n=69)based on follow-up outcomes(survival or death).Specimens of cancer tissue and adjacent tissues excised during surgery were collected from 136 patients.Real-time fluorescence quantitative PCR(RT-qPCR)was applied to detect the expression levels of CLDN10 and CSPG4 in cancer tissue and adjacent tissues.Based on the average expression levels of CLDN10 and CSPG4 in cancer tissues of NSCLC patients,they were grouped into CLDN10 high expression group(n=66),CLDN10 low expression group(n=70)and CSPG4 high expression group(n=71),CSPG4 low expression group(n=65).Multivariate COX regression analysis was used to determine the prognostic factors of NSCLC patients.Kaplan-Meier survival curve was applied to analyze the relationship between the expression levels of CLDN10 and CSPG4 in NSCLC patients and their prognosis.Results The expression level of CLDN10(0.96±0.25)in NSCLC tissues was lower than that in adjacent tissue(1.73±0.42),and the expression level of CSPG4 in NSCLC tissues(1.80±0.46)was higher than that in adjacent tissues(1.04±0.27),with statistical significance(t=18.372,16.617,all P<0.05).Compared with the survival group,the proportion of low undifferentiated,lymph node metastasis and CSPG4 expression of cancer tissues in the death group were higher,and the CLDN10 expression level of cancer tissues in the death group was lower,with statistical significance(t/χ2=8.463,7.423,11.696,6.426,all P<0.05).The five-year survival rate of the high expression group of CLDN10(58.46%)was higher than that of the low expression group(37.31%),and the five-year survival rate of the low expression group of CSPG4(55.56%)was higher than that of the high expression group(40.58%),and the differences were statistically significant(χ2=7.848,4.018,all P<0.05).Multivariate COX analysis results showed that low expression of CLDN10,high expression of CSPG4,low differentiation degree,and lymph node metastasis were all risk factors affecting the prognosis of NSCLC patients(HR=1.362,1.368,1.335,1.314,all P<0.05).Conclusion The expression level of CLDN10 was low and CSPG4 was high in cancer tissues of NSCLC patients,which was closely related to the development and prognosis of NSCLC.

Effects of miR-515-5p on the proliferation and metastasis of ovarian cancer cell A2780 by regulating the expression of chondroitin sulfate proteoglycan 4 and its mechanism / 解剖学报

Objective To investigate the targeted regulation of miR-515-5p on chondroitin sulfate proteoglycan 4 (CSPG4) and its effect on the proliferation and metastasis of ovarian cancer cell A2780. Methods The target genes of miR-515-5p were predicted by bioinformatics tools. Real-time PCR and Western blotting were used to detect the expression of miR-515-5p and CSPG4 in 65 cases ovarian cancer tissues and adjacent tissues. Ovarian cancer cells A2780 were divided into miR-NC group, miR-515-5p group, si-NC group, si-CSPG4 group, miR-515-5p + pcDNA group, miR-515-5p + pcDNA-CSPG4 group. MTT assay was used to detect cell proliferation. Transell was applied to detect cell migration and invasion, and Western blotting was selected to detect cyclinD1, P21, matrix metalloproteinase (MMP)-2 and MMP-9 protein expression. The double luciferase reporter gene experiment and Western blotting confirmed the regulation effect of miR-515-5p on CSPG4 gene. Results Bioinformatics analysis showed that CSPG4 was one of the potential target genes of miR-515-5p. Compared with the adjacent tissues, the expression of miR-515-5p was lower in ovarian cancer tissues, and the expression of CSPG4 was higher (P< 0. 05). Compared with the miR-NC group, the expression of cyclinD1, MMP-2 and MMP-9 protein was lower in A2780 cells of miR-515-5p group, the expression of P21 protein was higher, the cell viability was lower, and the number of cell migration and invasion was lower (P<0. 05). Compared with the si-NC group, the expression of cyclinD1, MMP-2 and MMP-9 proteins were lower in A2780 cells in si-CSPG4 group, P21 protein was higher, cell viability was lower, and the number of cell migration and invasion was lower (P<0. 05). Compared with the miR-515-5p + pcDNA group, the expression of cyclinD1, MMP-2 and MMP-9 proteins was higher in A2780 cells of miR-515-5p + pcDNA-CSPG4 group, the expression of P21 protein was lower, and the cell viability was higher, the number of cell migration and invasion was higher (P<0. 05). MiR-515-5p targeted and negatively regulated CSPG4 expression. Conclusion MiR-515-5p could inhibit the proliferation and metastasis of ovarian cancer cell A2780 by targeting CSPG4.