Interference with SPARC inhibits Benzophenone-3 induced ferroptosis in osteoarthritis: Evidence from bioinformatics analyses and biological experimentation.

The aim of this study is to conduct a thorough evaluation of the association between Benzophenone-3 (BP-3) exposure and OA, offering critical insights into the underlying mechanisms involved. The National Health and Nutrition Examination Survey (NHANES) database was utilized to investigate the correlation between BP-3 and osteoarthritis. Proteomic sequencing from clinical sample and the PharmMapper online tool were employed to predict the biological target of BP-3. Cellular molecular assays and transfection studies were performed to verify the prediction from bioinformatics analyses. Through cross-sectional analysis of the NHANES database, we identified BP-3 as a risk factor for OA development. The results of proteomic sequencing showed that Secreted Protein Acidic and Rich in Cysteine (SPARC) was significantly elevated in the area of damage compared to the undamaged area. SPARC was also among the potential biological targets of BP-3 predicted by the online program. Through in vitro cell experiments, we further determined that the toxicological effects of BP-3 may be due to SPARC, which elevates intracellular GPX4 levels, activates the glutathione system, and promotes lipid peroxidation to mitigate ferroptosis. Inhibiting SPARC expression has been shown to reduce inflammation and ferroptosis in OA contexts. This research provides an expansive understanding of BP-3's influence on osteoarthritis development. We have identified SPARC as a potent target for combating chondrocyte ferroptosis in BP-3-associated osteoarthritis.

Inhibition of SPARC signal by aerobic exercise to ameliorate atherosclerosis.

BACKGROUND AND AIMS: Inflammation and atherosclerosis (AS) are closely associated to Secreted Protein Acidic and Rich in Cysteine (SPARC) and its related factors. This study attempted to define the role and the potential mechanism of SPARC and its related factors in ameliorating hyperlipidemia and AS by aerobic exercise intervention. METHODS: The AS rat model was established with a high-fat diet plus vitamin D3 intraperitoneal injection. Treadmill exercises training (5 days/week at 14 m/min for 60 min/day) for 6 weeks was carried out for AS rat intervention method. Western blotting and qRT-PCR were used to analyze the mRNA and protein expression of SPARC and its related factors, respectively. H&E staining was applied to evaluate the morphological changes and inflammation damage. Von Kossa staining was used to measure the degree of vascular calcification. Fluorescence immunohistochemistry staining was used to detect the expression and distribution of SPARC signal molecules. RESULTS: SPARC was highly expressed and co-localization with the smooth muscle marker α-SMC in the AS rat. And its downstream factors, NF-κB, Caspase-1, IL-1ß and IL-18 were upregulated (P < 0.05 or P < 0.01), FNDC5 expression was downregulated in AS rat model. However, slight declined body weight, delayed AS progression, decreased hyperlipidemia and favorable morphology of skeletal muscle and blood vessels have been detected in AS rat with aerobic exercise intervention. Moreover, the expression of SPARC and its downstream factors were decreased (P < 0.05 or P < 0.01), while elevated the expression of FNDC5 (P < 0.01) was observed after aerobic exercise intervention. CONCLUSIONS: This study suggested that aerobic exercise ameliorated hyperlipidemia and AS by effectively inhibiting SPARC signal, and vascular smooth muscle cells may contribute greatly to the protection of AS.

SPARC Stabilizes ApoE to Induce Cholesterol-Dependent Invasion and Sorafenib Resistance in Hepatocellular Carcinoma.

Dysregulation of cholesterol homeostasis is implicated in the development and progression of hepatocellular carcinoma (HCC) that is characterized by intrahepatic and early extrahepatic metastases. A better understanding of the underlying mechanisms regulating cholesterol metabolism in HCC could help identify strategies to circumvent the aggressive phenotype. Here, we found that high expression of intracellular SPARC (secreted protein acidic and rich in cysteine) was significantly associated with elevated cholesterol levels and an enhanced invasive phenotype in HCC. SPARC potentiated cholesterol accumulation in HCC cells during tumor progression by stabilizing the ApoE protein. Mechanistically, SPARC competitively bound to ApoE, impairing its interaction with the E3 ligase tripartite motif containing 21 (TRIM21) and preventing its ubiquitylation and subsequent degradation. ApoE accumulation led to cholesterol enrichment in HCC cells, stimulating PI3K-AKT signaling and inducing epithelial-mesenchymal transition (EMT). Importantly, sorafenib-resistant HCC cells were characterized by increased expression of intracellular SPARC, elevated cholesterol levels, and enhanced invasive capacity. Inhibiting SPARC expression or reducing cholesterol levels enhanced the sensitivity of HCC cells to sorafenib treatment. Together, these findings unveil interplay between SPARC and cholesterol homeostasis. Targeting SPARC-triggered cholesterol-dependent oncogenic signaling is a potential therapeutic strategy for advanced HCC. SIGNIFICANCE: Intracellular SPARC boosts cholesterol availability to fuel invasion and drug resistance in hepatocellular carcinoma, providing a rational approach to improve the treatment of advanced liver cancer.

Citric acid promotes SPARC release in pancreatic cancer cells and inhibits the progression of pancreatic tumors in mice on a high-fat diet.

Over the years, pancreatic cancer has experienced a global surge in incidence and mortality rates, largely attributed to the influence of obesity and diabetes mellitus on disease initiation and progression. In this study, we investigated the pathogenesis of pancreatic cancer in mice subjected to a high-fat diet (HFD) and observed an increase in citric acid expenditure. Notably, citrate treatment demonstrates significant efficacy in promoting tumor cell apoptosis, suppressing cell proliferation, and inhibiting tumor growth in vivo. Our investigations revealed that citrate achieved these effects by releasing secreted protein acidic and rich in cysteine (SPARC) proteins, repolarizing M2 macrophages into M1 macrophages, and facilitating tumor cell apoptosis. Overall, our research highlights the critical role of citric acid as a pivotal metabolite in the intricate relationship between obesity and pancreatic cancer. Furthermore, we uncovered the significant metabolic and immune checkpoint function of SPARC in pancreatic cancer, suggesting its potential as both a biomarker and therapeutic target in treating this patient population.

Osteonectin (SPARC) prognostic value in prostate cancer.

BACKGROUND: Prostate cancer (PCa) is common malignancy among men worldwide. To date only few molecular markers are available to predict its course and outcome. SPARC is considered to be promising prognostic marker of PCa due to its involvement in various cancer processes. MATERIALS AND METHODS: study was conducted on PCa surgical primary tumor samples, obtained from 84 patients. Level of SPARC mRNA expression was estimated using RT-qPCR. To identify SPARC protein (osteonectin) in prostate tissue, immunohistochemical analysis was conducted. Bioinformatical analysis was performed on UALCAN and TNMplot resources. RESULTS: bioinformatical analysis demonstrated that SPARC mRNA levels are decreased in PCa samples, in comparison to normal tissue. In patients with lymph node metastases its levels are 1.26 times higher; p = 4.66E-02, than in N0 category. Ex vivo study demonstrated that SPARC expression was elevated on both mRNA and protein levels in PCa patients with lymph node metastases (by 2.34 and 1.91, respectively, p < 0.05). We established higher levels of SPARC mRNA and protein in PCa patients with T3 tumors, as well as high Gleason score. Estimation of survival rates demonstrated that PCa patients with a high level of SPARC mRNA and protein have decreased overall 2-year survival. CONCLUSIONS: SPARC protein was overexpressed on mRNA and protein levels in patients with presence of lymph node metastases and higher Gleason score of tumors. Also, both mRNA and protein upregulation were associated with worse survival rates. The current study has therefore provided further evidence that SPARC is indeed linked to the prognosis and aggressiveness of human PCa.

Effect of Sparc knockout on the extracellular matrix of mouse periodontal ligament cells.

The periodontal ligament (PDL) is a critical component in maintaining tooth stability. It is composed of cells and an extracellular matrix (ECM), each with unique roles in tissue function and homeostasis. Secreted protein acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, plays a crucial role in regulating ECM assembly and turnover, alongside facilitating cellular-ECM interactions. In the present study, mass spectrometry-based proteomics was used to assess the impacts of Sparc-knockout (KO) on PDL-derived cells. Results demonstrated that Sparc-KO significantly reduces ECM production and alters its composition with increased levels of type I collagen. Despite this increase in Sparc-KO, type I collagen was not likely to be effectively integrated into the fibrils due to collagen cross-linking impairment. Furthermore, the pathway and process enrichment analyses suggested that SPARC plays a protective role against ECM degradation by antagonistically interacting with cell-surface collagen receptors. These findings provide detailed insights into the multifaceted role of SPARC in ECM organization, including its impact on ECM production, collagen regulation, and interactions with various cellular compartments. A better understanding of these complex mechanisms is crucial for comprehending the causes of periodontal disease and tissue regeneration, where precise control of ECM organization is necessary.

Peritumoral SPARC expression induced by exosomes from nasopharyngeal carcinoma infected Epstein-Barr virus: A poor prognostic marker.

Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) cells have high metastatic potential. Recent research has revealed that the interaction of between tumor cells and the surrounding stroma plays an important role in tumor invasion and metastasis. In this study, we showed the prognostic value of expression of SPARC, an extracellular matrix protein with multiple cellular functions, in normal adjacent tissues (NAT) surrounding NPC. In the immunohistochemical analysis of 51 NPC biopsy specimens, SPARC expression levels were significantly elevated in the NAT of EBER (EBV-encoded small RNA)-positive NPC compared to that in the NAT of EBER-negative NPC. Moreover, increased SPARC expression in NAT was associated with a worsening of overall survival. The enrichment analysis of RNA-seq of publicly available NPC and NAT surrounding NPC data showed that high SPARC expression in NPC was associated with epithelial mesenchymal transition promotion, and there was a dynamic change in the gene expression profile associated with interference of cellular proliferation in NAT, including SPARC expression. Furthermore, EBV-positive NPC cells induce SPARC expression in normal nasopharyngeal cells via exosomes. Induction of SPARC in cancer-surrounding NAT cells reduced intercellular adhesion in normal nasopharyngeal structures and promoted cell competition between cancer cells and normal epithelial cells. These results suggest that epithelial cells loosen their own binding with the extracellular matrix as well as stromal cells, facilitating the invasion of tumor cells into the adjacent stroma by activating cell competition. Our findings reveal a new mechanism by which EBV creates a pro-metastatic microenvironment by upregulating SPARC expression in NPC.

The association of SPARC with hypertension and its function in endothelial-dependent relaxation.

BACKGROUND AND AIMS: Secreted protein acidic and rich in cysteine (SPARC) is involved in the pathological processes of many metabolic diseases. However, studies on the relevance of SPARC to hypertension and its involvement in endothelial function are scarce. In this study, we aim to explore the relevance of SPARC to hypertension and investigate its role in endothelium-dependent relaxation (EDR). METHODS: 110 patients who met the criteria were recruited as participants. Serum SPARC concentrations were determined by Luminex assay. The correlation between SPARC levels and hypertension was analyzed. After treatment with SPARC ex vivo or in vivo, endothelial-dependent relaxation (EDR) was measured by wire myography. Western blotting was performed to detect the expression of proteins relevant to endothelial function. RESULTS: Our results showed that serum SPARC levels were significantly higher in the hypertensive group and were positively associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP). Functional results demonstrated that SPARC dramatically impaired EDR and induced the excess production of reactive oxygen species (ROS) in endothelial cells. Further experimental results confirmed that SPARC reduced angiotensin-converting enzyme 2 (ACE2) expression and ACE2 overexpression or activation completely abolished the impairing effect of SPARC on endothelial function. CONCLUSIONS: The present study reveals the correlation between elevated SPARC and hypertension and confirms its adverse effect on endothelial function, helping establish a comprehensive understanding of hypertension-related endothelial dysfunction in a new scope.

Targeting NADPH Oxidase and Integrin α5ß1 to Inhibit Neutrophil Extracellular Traps-Mediated Metastasis in Colorectal Cancer.

Metastasis leads to a high mortality rate in colorectal cancer (CRC). Increased neutrophil extracellular traps (NETs) formation is one of the main causes of metastasis. However, the mechanism of NETs-mediated metastasis remains unclear and effective treatments are lacking. In this study, we found neutrophils from CRC patients have enhanced NETs formation capacity and increased NETs positively correlate with CRC progression. By quantitative proteomic analysis of clinical samples and cell lines, we found that decreased secreted protein acidic and rich in cysteine (SPARC) results in massive NETs formation and integrin α5ß1 is the hub protein of NETs-tumor cell interaction. Mechanistically, SPARC regulates the activation of the nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) pathway by interacting with the receptor for activated C kinase 1 (RACK1). Over-activated NADPH oxidase generates more reactive oxygen species (ROS), leading to the release of NETs. Then, NETs upregulate the expression of integrin α5ß1 in tumor cells, which enhances adhesion and activates the downstream signaling pathways to promote proliferation and migration. The combination of NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI) and integrin α5ß1 inhibitor ATN-161 (Ac-PHSCN-NH2) effectively suppresses tumor progression in vivo. Our work reveals the mechanistic link between NETs and tumor progression and suggests a combination therapy against NETs-mediated metastasis for CRC.

The role of SPARC (secreted protein acidic and rich in cysteine) in the pathogenesis of obesity, type 2 diabetes, and non-alcoholic fatty liver disease

Secreted protein acidic and rich in cysteine (SPARC) is an extracellular matrix glycoprotein with pleiotropic functions, which is expressed in adipose, hepatic, muscular, and pancreatic tissue. Particularly, several studies demonstrated that SPARC is an important player in the context of obesity, diabetes, and fatty liver disease including advanced hepatic fibrosis and hepatocellular carcinoma. Evidence in murine and human samples indicates that SPARC is involved in adipogenesis, cellular metabolism, extracellular matrix modulation, glucose and lipid metabolism, among others. Furthermore, studies in SPARC knockout mouse model showed that SPARC contributes to adipose tissue formation, non-alcoholic fatty liver disease (NAFLD), and diabetes. Hence, SPARC may represent a novel and interesting target protein for future therapeutic interventions or a biomarker of disease progression. This review summarizes the role of SPARC in the pathophysiology of obesity, and extensively revised SPARC functions in physiological and pathological adipose tissue deposition, muscle metabolism, liver, and diabetes-related pathways. (AU)

Reduction of SPARC protects mice against NLRP3 inflammasome activation and obesity.

The comprehensive assessment of long-term effects of reducing intake of energy (CALERIE-II; NCT00427193) clinical trial established that caloric restriction (CR) in humans lowers inflammation. The identity and mechanism of endogenous CR-mimetics that can be deployed to control obesity-associated inflammation and diseases are not well understood. Our studies have found that 2 years of 14% sustained CR in humans inhibits the expression of the matricellular protein, secreted protein acidic and rich in cysteine (SPARC), in adipose tissue. In mice, adipose tissue remodeling caused by weight loss through CR and low-protein diet feeding decreased, while high-fat diet-induced (HFD-induced) obesity increased SPARC expression in adipose tissue. Inducible SPARC downregulation in adult mice mimicked CR's effects on lowering adiposity by regulating energy expenditure. Deletion of SPARC in adipocytes was sufficient to protect mice against HFD-induced adiposity, chronic inflammation, and metabolic dysfunction. Mechanistically, SPARC activates the NLRP3 inflammasome at the priming step and downregulation of SPARC lowers macrophage inflammation in adipose tissue, while excess SPARC activated macrophages via JNK signaling. Collectively, reduction of adipocyte-derived SPARC confers CR-like metabolic and antiinflammatory benefits in obesity by serving as an immunometabolic checkpoint of inflammation.

Role of Albumin as a Targeted Drug Carrier in the Management of Rheumatoid Arthritis: A Comprehensive Review.

An endogenous transporter protein called albumin interacts with the Fc receptor to provide it with multiple substrate-binding domains, cell membrane receptor activation, and an extended circulating half-life. Albumin has the remarkable ability to bind with receptors viz. secreted protein acidic and rich in cysteine (SPARC) and scavenger protein-A (SR-A) that are overexpressed during rheumatoid arthritis (RA), enabling active targeting of the disease site instead of requiring specialized substrates to be added to the nanocarrier. RA, a chronic autoimmune illness, is characterized by the presence of a severe inflammatory response. RA patients have low serum albumin concentration, which signifies the high uptake of albumin at the inflammatory sites, giving a rationale to use albumin as a drug carrier for RA therapy. Albumin has the capacity for both passive and active targeting. It is an abundantly available protein in the bloodstream showing excellent cellular compatibility, degradability in biological tissues, nonantigenicity, and safety. There are three strategies of albumin mediated drug delivery as encapsulating therapeutics in albumin nanoparticles, chemically conjugating drugs with functional proteins, and albumin itself which is used as a targeting ligand to deliver drugs specifically to cells or tissues that express albumin-binding receptors. In the current review, an attempt has been made to highlight the significant evidence of albumin as a drug delivery carrier for the safe and effective management of RA. Evidence has been provided in the form of recent research advances, clinical trials, and patents. Additionally, this review will outline the prospective for the potential utilization of albumin as a drug vehicle for RA and suggest possible future avenues to provide the perspective for subsequent studies.

Hepatic SPARC Expression Is Associated with Inflammasome Activation during the Progression of Non-Alcoholic Fatty Liver Disease in Both Mice and Morbidly Obese Patients.

The severity of non-alcoholic fatty liver disease (NAFLD) ranges from simple steatosis to steatohepatitis, and it is not yet clearly understood which patients will progress to liver fibrosis or cirrhosis. SPARC (Secreted Protein Acidic and Rich in Cysteine) has been involved in NAFLD pathogenesis in mice and humans. The aim of this study was to investigate the role of SPARC in inflammasome activation, and to evaluate the relationship between the hepatic expression of inflammasome genes and the biochemical and histological characteristics of NAFLD in obese patients. In vitro studies were conducted in a macrophage cell line and primary hepatocyte cultures to assess the effect of SPARC on inflammasome. A NAFLD model was established in SPARC knockout (SPARC-/-) and SPARC+/+ mice to explore inflammasome activation. A hepatic RNAseq database from NAFLD patients was analyzed to identify genes associated with SPARC expression. The results were validated in a prospective cohort of 59 morbidly obese patients with NAFLD undergoing bariatric surgery. Our results reveal that SPARC alone or in combination with saturated fatty acids promoted IL-1ß expression in cell cultures. SPARC-/- mice had reduced hepatic inflammasome activation during the progression of NAFLD. NAFLD patients showed increased expression of SPARC, NLRP3, CASP1, and IL-1ß. Gene ontology analysis revealed that genes positively correlated with SPARC are linked to inflammasome-related pathways during the progression of the disease, enabling the differentiation of patients between steatosis and steatohepatitis. In conclusion, SPARC may play a role in hepatic inflammasome activation in NAFLD.

SPARC Is Highly Expressed in Young Skin and Promotes Extracellular Matrix Integrity in Fibroblasts via the TGF-ß Signaling Pathway.

The matricellular secreted protein acidic and rich in cysteine (SPARC; also known as osteonectin), is involved in the regulation of extracellular matrix (ECM) synthesis, cell-ECM interactions, and bone mineralization. We found decreased SPARC expression in aged skin. Incubating foreskin fibroblasts with recombinant human SPARC led to increased type I collagen production and decreased matrix metalloproteinase-1 (MMP-1) secretion at the protein and mRNA levels. In a three-dimensional culture of foreskin fibroblasts mimicking the dermis, SPARC significantly increased the synthesis of type I collagen and decreased its degradation. In addition, SPARC also induced receptor-regulated SMAD (R-SMAD) phosphorylation. An inhibitor of transforming growth factor-beta (TGF-ß) receptor type 1 reversed the SPARC-induced increase in type I collagen and decrease in MMP-1, and decreased SPARC-induced R-SMAD phosphorylation. Transcriptome analysis revealed that SPARC modulated expression of genes involved in ECM synthesis and regulation in fibroblasts. RT-qPCR confirmed that a subset of differentially expressed genes is induced by SPARC. These results indicated that SPARC enhanced ECM integrity by activating the TGF-ß signaling pathway in fibroblasts. We inferred that the decline in SPARC expression in aged skin contributes to process of skin aging by negatively affecting ECM integrity in fibroblasts.

Omics Overview of the SPARC Gene in Mesothelioma.

The SPARC gene plays multiple roles in extracellular matrix synthesis and cell shaping, associated with tumor cell migration, invasion, and metastasis. The SPARC gene is also involved in the epithelial-mesenchymal transition (EMT) process, which is a critical phenomenon leading to a more aggressive cancer cell phenotype. SPARC gene overexpression has shown to be associated with poor survival in the mesothelioma (MESO) cohort from the TCGA database, indicating that this gene may be a powerful prognostic factor in MESO. Its overexpression is correlated with the immunosuppressive tumor microenvironment. Here, we summarize the omics advances of the SPARC gene, including the summary of SPARC gene expression associated with prognosis in pancancer and MESO, the immunosuppressive microenvironment, and cancer cell stemness. In addition, SPARC might be targeted by microRNAs. Notably, despite the controversial functions on angiogenesis, SPARC may directly or indirectly contribute to tumor angiogenesis in MESO. In conclusion, SPARC is involved in tumor invasion, metastasis, immunosuppression, cancer cell stemness, and tumor angiogenesis, eventually impacting patient survival. Strategies targeting this gene may provide novel therapeutic approaches to the treatment of MESO.

SPARC-YAP/TAZ inhibition prevents the fibroblasts-myofibroblasts transformation.

BACKGROUND: Fibrotic scar is a severe side effect of trabeculectomy, resulting in unsatisfactory outcomes for glaucoma surgery. Accumulating evidence showed human Tenon's fibroblasts (HTFs) play an important role in fibrosis formation. We previously reported that the aqueous level of secreted protein acidic and rich in cysteine (SPARC) was higher in the patients with primary angle closure glaucoma, which was associated with the failure of trabeculectomy. In this study, the potential effect and mechanism of SPARC in promoting fibrosis were explored by using HTFs. METHODS: HTFs were employed in this study and examined under a phase-contrast microscope. Cell viability was determined by CCK-8. The expressions of SPARC-YAP/TAZ signaling and the fibrosis-related markers were examined with reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), Western blot, and immunofluorescence, subcellular fractionation was conducted to further determined the variation of YAP and phosphorylated YAP. The differential gene expressions were analyzed with RNA sequencing (RNAseq), followed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. RESULTS: Exogenous SPARC induced HTFs-myofibroblast transformation, as evidenced by the increased expression of α-SMA, collagen I and fibronectin in both protein and mRNA levels. SPARC knockdown decreased the expressions of the above genes in TGF-ß2-treated HTFs. KEGG analysis showed that the Hippo signaling pathway was mostly enriched. SPARC treatment increased the expressions of YAP, TAZ, CTGF and CYR61 as well as enhanced YAP translocation from cytoplasm to nucleus, and decreased the phosphorylation of YAP and LAST1/2, which was reversed by SPARC knockdown. Knockdown of YAP1 decreased the fibrosis-related markers, such as α-SMA, collagen I and Fibronectin, in SPARC-treated HTFs. CONCLUSIONS: SPARC induced HTFs-myofibroblast transformation via activating YAP/TAZ signaling. Targeting SPARC-YAP/TAZ axis in HTFs might provide a novel strategy for inhibiting fibrosis formation after trabeculectomy.

Diosgenin restores memory function via SPARC-driven axonal growth from the hippocampus to the PFC in Alzheimer's disease model mice.

Central nervous system axons have minimal capacity to regenerate in adult brains, hindering memory recovery in Alzheimer's disease (AD). Although recent studies have shown that damaged axons sprouted in adult and AD mouse brains, long-distance axonal re-innervation to their targets has not been achieved. We selectively visualized axon-growing neurons in the neural circuit for memory formation, from the hippocampus to the prefrontal cortex, and showed that damaged axons successfully extended to their native projecting area in mouse models of AD (5XFAD) by administration of an axonal regenerative agent, diosgenin. In vivo transcriptome analysis detected the expression profile of axon-growing neurons directly isolated from the hippocampus of 5XFAD mice. Secreted protein acidic and rich in cysteine (SPARC) was the most expressed gene in axon-growing neurons. Neuron-specific overexpression of SPARC via adeno-associated virus serotype 9 delivery in the hippocampus recovered memory deficits and axonal projection to the prefrontal cortex in 5XFAD mice. DREADDs (Designer receptors exclusively activated by designer drugs) analyses revealed that SPARC overexpression-induced axonal growth in the 5XFAD mouse brain directly contributes to memory recovery. Elevated levels of SPARC on axonal membranes interact with extracellular rail-like collagen type I to promote axonal remodeling along their original tracings in primary cultured hippocampal neurons. These findings suggest that SPARC-driven axonal growth in the brain may be a promising therapeutic strategy for AD and other neurodegenerative diseases.

The impact of mild hypoxia exposure on myokine secretion in human obesity.

BACKGROUND/OBJECTIVE: Compelling evidence indicates that myokines act in an autocrine, paracrine and endocrine manner to alter metabolic homeostasis. The mechanisms underlying exercise-induced changes in myokine secretion remain to be elucidated. Since exercise acutely decreases oxygen partial pressure (pO2) in skeletal muscle (SM), the present study was designed to test the hypothesis that (1) hypoxia exposure impacts myokine secretion in primary human myotubes and (2) exposure to mild hypoxia in vivo alters fasting and postprandial plasma myokine concentrations in humans. METHODS: Differentiated primary human myotubes were exposed to different physiological pO2 levels for 24 h, and cell culture medium was harvested to determine myokine secretion. Furthermore, we performed a randomized single-blind crossover trial to investigate the impact of mild intermittent hypoxia exposure (MIH: 7-day exposure to 15% O2, 3x2h/day vs. normoxia: 21% O2) on in vivo SM pO2 and plasma myokine concentrations in 12 individuals with overweight and obesity (body-mass index ≥ 28 kg/m2). RESULTS: Hypoxia exposure (1% O2) increased secreted protein acidic and rich in cysteine (SPARC, p = 0.043) and follistatin like 1 (FSTL1, p = 0.021), and reduced leukemia inhibitory factor (LIF) secretion (p = 0.009) compared to 3% O2 in primary human myotubes. In addition, 1% O2 exposure increased interleukin-6 (IL-6, p = 0.004) and SPARC secretion (p = 0.021), whilst reducing fatty acid binding protein 3 (FABP3) secretion (p = 0.021) compared to 21% O2. MIH exposure in vivo markedly decreased SM pO2 (≈40%, p = 0.002) but did not alter plasma myokine concentrations. CONCLUSIONS: Hypoxia exposure altered the secretion of several myokines in primary human myotubes, revealing hypoxia as a novel modulator of myokine secretion. However, both acute and 7-day MIH exposure did not induce alterations in plasma myokine concentrations in individuals with overweight and obesity. CLINICAL TRIALS IDENTIFIER: This study is registered at the Netherlands Trial Register (NL7120/NTR7325).

An in vitro study into three different PRF preparations for osteogenesis potential.

OBJECTIVE: To investigate the effect of Advanced Platelet-Rich Fibrin (A-PRF+), Leukocyte Platelet-Rich Fibrin (L-PRF), and injectable Platelet-Rich Fibrin (i-PRF) on osteogenesis of a human osteoblast-like cell line in vitro. BACKGROUND: Different PRF protocols are used in clinical dentistry in the last years. Recent literature documented the positive impact of PRF derivatives in vivo and in vitro, on different types of cells. However, hardly any literature comparing the new protocols for PRF (the A-PRF+ and i-PRF) with the original protocol of PRF (L-PRF) is present for osteoblast-like cells. MATERIALS AND METHODS: A-PRF+, L-PRF, and i-PRF were prepared from six male donors and pre-cultured with 10 mL culture medium for 6 days. 5 x 103  cells/ml osteoblasts from the osteoblast cell line (U2OS) were seeded and cultured either with conditioned medium derived from the different PRF conditions or with regular culture medium. At five different time points (0, 7, 14, 21, 28 days), the osteogenic capacity of the cells was assessed with Alizarin Red S to visualize mineralization. Also in these cells, the calcium concentration and alkaline phosphatase activity were investigated. Using qPCR, the expression of alkaline phosphatase, osteocalcin, osteonectin, ICAM-1, RUNX-2, and collagen 1a was assessed. RESULTS: In osteoblast-like cells cultured with conditioned medium, the A-PRF+ conditioned medium induced more mineralization and calcium production after 28 days of culturing compared with the control (p < .05). No significant differences were found in the extent of cell proliferation between the different conditions. RUNX-2 and osteonectin mRNA expression in the cells were lower in all PRF-stimulated cultures compared with control at different time points. The i-PRF-conditioned medium induced more ALP activity (p < .05) compared with control and osteoblasts-like cells differentiated more compared with osteoblasts cultured with L-PRF. CONCLUSIONS: The three PRF preparations seem to have the capacity to increase the osteogenic potential of osteoblast-like cells. A-PRF+ seems to have the highest potential for mineralization, while i-PRF seems to have the potential to enhance early cell differentiation.

Glucagon-like peptide-1 receptor promotes osteoblast differentiation of dental pulp stem cells and bone formation in a zebrafish scale regeneration model.

Bone cells express the glucagon-like peptide 1 receptor (GLP-1R). However, its presence and role in human dental pulp derived stem cells (hDPSCs) remains elusive. Hence, in the current study, we isolated hDPSCs and differentiated them into osteoblasts, where GLP-1R expression was found to be upregulated during osteoblast differentiation. GLP-1 receptor agonist, liraglutide peptide treatment, increased osteoblast differentiation in hDPSCs by increasing calcium deposition, ALP activity, and osteoblast marker genes, Runx2, type 1 col, osteonectin, and osteocalcin. Furthermore, activation of long non-coding RNA (LncRNA) LINC00968 and microRNA-3658 signalling increased Runx2 expression. Specifically, liraglutide increased LncRNA-LINC00968 expression while decreasing miR-3658 expression. LINC00968 targets miR-3658, and miR-3658 targets Runx2. Additionally, in an in-vivo study, zebrafish scale regeneration model, liraglutide promoted calcium deposition, osteoblastic cell count, collagen 1α, osteonectin, osteocalcin, runx2a MASNA isoform expression (transcribed from promoter P1), and Ca/P ratio in scales. Overall, GLP-1R activation promotes osteoblast differentiation via Runx2/LncRNA-LINC00968/miR-3658 signalling in hDPSCs and promotes bone formation in zebrafish scale regeneration.