Navigating the microbial maze: unraveling the connection between gut microbiome and pediatric kidney and urinary tract disease.

The gut microbiome is made up of trillions of bacteria, viruses, archaea, and microbes that play a significant role in the maintenance of normal physiology in humans. Recent research has highlighted the effects of the microbiome and its dysbiosis in the pathogenesis and maintenance of kidney disease, especially chronic kidney disease (CKD) and its associated cardiovascular disease. While studies have addressed the kidney-microbiome axis in adults, how dysbiosis may uniquely impact pediatric kidney disease patients is not well-established. This narrative review highlights all relevant studies focusing on the microbiome and pediatric kidney disease that were published between 7/2015 and 7/2023. This review highlights pediatric-specific considerations including growth and bone health as well as emphasizing the need for increased pediatric research. Understanding microbiome-kidney interactions may allow for novel, less invasive interventions such as dietary changes and the use of probiotics to improve preventive care and ameliorate long-term morbidity and mortality in this vulnerable population.

Ethnic Variations in the Levels of Bone Biomarkers (Osteoprostegerin, Receptor Activator of Nuclear Factor Kappa-Β Ligand and Glycoprotein Non-Metastatic Melanoma Protein B) in People with Type 2 Diabetes.

The global incidence of Type 2 diabetes (T2D) is on the rise, fueled by factors such as obesity, sedentary lifestyles, socio-economic factors, and ethnic backgrounds. T2D is a multifaceted condition often associated with various health complications, including adverse effects on bone health. This study aims to assess key biomarkers linked to bone health and remodeling-Osteoprotegerin (OPG), Receptor Activator of Nuclear Factor Kappa-Β Ligand (RANKL), and Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB)-among individuals with diabetes while exploring the impact of ethnicity on these biomarkers. A cross-sectional analysis was conducted on a cohort of 2083 individuals from diverse ethnic backgrounds residing in Kuwait. The results indicate significantly elevated levels of these markers in individuals with T2D compared to non-diabetic counterparts, with OPG at 826.47 (405.8) pg/mL, RANKL at 9.25 (17.3) pg/mL, and GPNMB at 21.44 (7) ng/mL versus 653.75 (231.7) pg/mL, 0.21 (9.94) pg/mL, and 18.65 (5) ng/mL in non-diabetic individuals, respectively. Notably, this elevation was consistent across Arab and Asian populations, except for lower levels of RANKL observed in Arabs with T2D. Furthermore, a positive and significant correlation between OPG and GPNMB was observed regardless of ethnicity or diabetes status, with the strongest correlation (r = 0.473, p < 0.001) found among Arab individuals with T2D. Similarly, a positive and significant correlation between GPNMB and RANKL was noted among Asian individuals with T2D (r = 0.401, p = 0.001). Interestingly, a significant inverse correlation was detected between OPG and RANKL in non-diabetic Arab individuals. These findings highlight dysregulation in bone remodeling markers among individuals with T2D and emphasize the importance of considering ethnic variations in T2D-related complications. The performance of further studies is warranted to understand the underlying mechanisms and develop interventions based on ethnicity for personalized treatment approaches.

Evaluating the correlation of sclerostin levels with obesity and type 2 diabetes in a multiethnic population living in Kuwait.

Obesity and Type 2 Diabetes Mellitus (T2DM) are intricate metabolic disorders with a multifactorial etiology, often leading to a spectrum of complications. Recent research has highlighted the impact of these conditions on bone health, with a particular focus on the role of sclerostin (SOST), a protein molecule integral to bone metabolism. Elevated circulating levels of SOST have been observed in patients with T2DM compared to healthy individuals. This study aims to examine the circulating levels of SOST in a multiethnic population living in Kuwait and to elucidate the relationship between SOST levels, obesity, T2DM, and ethnic background. The study is a cross-sectional analysis of a large cohort of 2083 individuals living in Kuwait. The plasma level of SOST was measured using a bone panel multiplex assay. The study found a significant increase in SOST levels in individuals with T2DM (1008.3 pg/mL, IQR-648) compared to non-diabetic individuals (710.6 pg/mL, IQR-479). There was a significant gender difference in median SOST levels, with males exhibiting higher levels than females across various covariates (diabetes, IR, age, weight, and ethnicity). Notably, SOST levels varied significantly with ethnicity: Arabs (677.4 pg/mL, IQR-481.7), South Asians (914.6 pg/mL, IQR-515), and Southeast Asians (695.2 pg/mL, IQR-436.8). Furthermore, SOST levels showed a significant positive correlation with gender, age, waist circumference, systolic and diastolic blood pressure, fasting blood glucose, HbA1c, insulin, total cholesterol, triglycerides, HDL, LDL, ALT, and AST (p-Value ≥0.05). South Asian participants, who exhibited the highest SOST levels, demonstrated the most pronounced associations, even after adjusting for age, gender, BMI, and diabetes status (p-Value ≥0.05). The observed correlations of SOST with various clinical parameters suggest its significant role in the diabetic milieu, particularly pronounced in the South Asian population compared to other ethnic groups.

The Lymphatic Endothelial Cell Secretome Inhibits Osteoblast Differentiation and Bone Formation.

Complex lymphatic anomalies (CLAs) are a set of rare diseases with unique osteopathic profiles. Recent efforts have identified how lymphatic-specific somatic activating mutations can induce abnormal lymphatic formations that are capable of invading bone and inducing bone resorption. The abnormal bone resorption in CLA patients has been linked to overactive osteoclasts in areas with lymphatic invasions. Despite these findings, the mechanism associated with progressive bone loss in CLAs remains to be elucidated. In order to determine the role of osteoblasts in CLAs, we sought to assess osteoblast differentiation and bone formation when exposed to the lymphatic endothelial cell secretome. When treated with lymphatic endothelial cell conditioned medium (L-CM), osteoblasts exhibited a significant decrease in proliferation, differentiation, and function. Additionally, L-CM treatment also inhibited bone formation through a neonatal calvaria explant culture. These findings are the first to reveal how osteoblasts may be actively suppressed during bone lymphatic invasion in CLAs.

A Pre-clinical Standard Operating Procedure for Evaluating Orthobiologics in an In Vivo Rat Spinal Fusion Model.

The rat animal model is a cost effective and reliable model used in spinal pre-clinical research. Complications from various surgical procedures in humans often arise that were based on these pre-clinical animal models. Therefore safe and efficacious pre-clinical animal models are needed to establish continuity into clinical trials. A Standard Operating Procedure (SOP) is a validated method that allows researchers to safely and carefully replicate previously successful surgical techniques. Thus, the aim of this study is to describe in detail the procedures involved in a common rat bilateral posterolateral intertransverse spinal fusion SOP used to test the efficacy and safety different orthobiologics using a collagen-soaked sponge as an orthobiologic carrier. Only two orthobiologics are currently FDA approved for spinal fusion surgery which include recombinant bone morphogenetic protein 2 (rhBMP-2), and I-FACTOR. While there are many additional orthobiologics currently being tested, one way to show their safety profile and gain FDA approval, is to use well established pre-clinical animal models. A preoperative, intraoperative, and postoperative surgical setup including specific anesthesia and euthanasia protocols are outlined. Furthermore, we describe different postoperative methods used to validate the spinal fusion SOP, which include µCT analysis, histopathology, biomechanical testing, and blood analysis. This SOP can help increase validity, transparency, efficacy, and reproducibly in future rat spinal fusion surgery procedures.

Osteopathy in Complex Lymphatic Anomalies.

Complex Lymphatic Anomalies (CLA) are lymphatic malformations with idiopathic bone and soft tissue involvement. The extent of the abnormal lymphatic presentation and boney invasion varies between subtypes of CLA. The etiology of these diseases has proven to be extremely elusive due to their rarity and irregular progression. In this review, we compiled literature on each of the four primary CLA subtypes and discuss their clinical presentation, lymphatic invasion, osseous profile, and regulatory pathways associated with abnormal bone loss caused by the lymphatic invasion. We highlight key proliferation and differentiation pathways shared between lymphatics and bone and how these systems may interact with each other to stimulate lymphangiogenesis and cause bone loss.

Epigenetic Regulation of Chondrocytes and Subchondral Bone in Osteoarthritis.

The aim of this review is to provide an updated review of the epigenetic factors involved in the onset and development of osteoarthritis (OA). OA is a prevalent degenerative joint disease characterized by chronic inflammation, ectopic bone formation within the joint, and physical and proteolytic cartilage degradation which result in chronic pain and loss of mobility. At present, no disease-modifying therapeutics exist for the prevention or treatment of the disease. Research has identified several OA risk factors including mechanical stressors, physical activity, obesity, traumatic joint injury, genetic predisposition, and age. Recently, there has been increased interest in identifying epigenetic factors involved in the pathogenesis of OA. In this review, we detail several of these epigenetic modifications with known functions in the onset and progression of the disease. We also review current therapeutics targeting aberrant epigenetic regulation as potential options for preventive or therapeutic treatment.

The role of miR-150 regulates bone cell differentiation and function.

BACKGROUND: mir-RNAs play a role in regulating bone homeostasis. In this study we assessed the functional role of mir-RNA 150 in bone homeostasis. We also assess the effects of miR-150 deficiency on osteoblast and osteoclast differentiation and function using in vivo and in vitro approaches. METHODS: Wild type (WT) (C57BL/6J) and miR-150 KO mice were compared for a variety of parameters. Micro-CT imaging was conducted to quantify trabecular bone mass inferior to the distal growth plate of the femur. Von Kossa staining was performed for osteoblast culture mineralization. RT-qPCR, biochemical analysis and bone histomorphometry were utilized for quantification of relevant genes and serum protein measurements. Differentiation and function of osteoblasts and osteoclasts was performed using primarily cultures and assessed the cell autonomous response of mir-RNA-150 on cell differentiation and function. RESULTS: Mir-150 exhibited expression in a variety of tissues and increases progressively with age. Through micro-CT imaging, we found that KO mice presented reduced bone mass at 4, 8, and 16 weeks of age compared to WT mice. Furthermore, histomorphometric analysis revealed increased trabecular separation, decreased bone thickness, and decreased osteoblast number in KO compared to WT mice. Mir-150 deficiency also correlated with higher bone resorption, accompanied with significant increases in CTX-1 serum levels, and a decrease in cell apoptotic rate ex vivo. Additionally, miR-150 KO mice showed increased osteoblast differentiation and decreased osteoclastogenesis ex vivo. Luciferase assay showed increased Osteoactivin/GPNMB expression in miR-150 KO osteoblasts compared to WT cells. CONCLUSION: Our data suggests that miR-150 influences osteoblast and osteoclast functionality and differentiation; specifically, miR-150 serves as a negative regulator for osteoblasts and a positive regulator for osteoclasts by regulating, at least in part, Osteoactivin/GPNMB expression.

Linking gene expression and phenotypic changes in the developmental and evolutionary origins of osteosclerosis in the ribs of bowhead whales (Balaena mysticetus).

Bowhead whales are among the longest-lived mammals with an extreme lifespan of about 211 years. During the first 25 years of their lives, rib bones increase in mineral density and the medulla transitions from compact to trabecular bone. Molecular drivers associated with these phenotypic changes in bone remain unknown. This study assessed expression levels of osteogenic genes from samples of rib bones of bowheads. Samples were harvested from prenatal to 86-year-old whales, representing the first third of the bowhead lifespan. Fetal to 2-year-old bowheads showed expression levels consistent with the rapid deposition of the bone extracellular matrix. Sexually mature animals showed expression levels associated with low rates of osteogenesis and increased osteoclastogenesis. After the first 25 years of life, declines in osteogenesis corresponded with increased expression of EZH2, an epigenetic regulator of osteogenesis. These findings suggest EZH2 may be at least one epigenetic modifier that contributes to the age-related changes in the rib bone phenotype along with the transition from compact to trabecular bone. Ancient cetaceans and their fossil relatives also display these phenotypes, suggesting EZH2 may have shaped the skeleton of whales in evolutionary history.

An Overview of Rickets in Children.

Rickets is a common bone disease worldwide that is associated with disturbances in calcium and phosphate homeostasis and can lead to short stature and joint deformities. Rickets can be diagnosed based on history and physical examination, radiological features, and biochemical tests. It can be classified into 2 major groups based on phosphate or calcium levels: phosphopenic and calcipenic. Knowledge of categorization of the type of rickets is essential for prompt diagnosis and proper management. Nutritional rickets is a preventable disease through adequate intake of vitamin D through both dietary and sunlight exposure. There are other subtypes of rickets, such as vitamin D-dependent type 1 rickets and vitamin D-dependent type 2 rickets (due to defects in vitamin D metabolism), renal rickets (due to poor kidney function), and hypophosphatemic rickets (vitamin D-resistant rickets secondary to renal phosphate wasting wherein fibroblast growth factor-23 (FGF-23) often plays a major role), which requires closer monitoring and supplementation with activated vitamin D with or without phosphate supplements. An important development has been the introduction of burosumab, a human monoclonal antibody to FGF-23, which is approved for the treatment of X-linked hypophosphatemia among children 1 year and older.

Aberrant epigenetic silencing of neuronatin is a frequent event in human osteosarcoma.

The paternally imprinted neuronatin (NNAT) gene has been identified as a target of aberrant epigenetic silencing in diverse cancers, but no association with pediatric bone cancers has been reported to date. In screening childhood cancers, we identified aberrant CpG island hypermethylation in a majority of osteosarcoma (OS) samples and in 5 of 6 human OS cell lines studied but not in normal bone-derived tissue samples. CpG island hypermethylation was associated with transcriptional silencing in human OS cells, and silencing was reversible upon treatment with 5-aza-2'-deoxycytidine. Expression of NNAT was detectable in osteoblasts and chondrocytes of human bone, supporting a potential role in bone homeostasis. Enforced expression of NNAT in human OS cells lacking endogenous expression resulted in significant reduction in colony formation and in vitro migration compared to nonexpressor control cells. We next analyzed the effect of NNAT expression on intracellular calcium homeostasis and found that was associated with an attenuated decay of calcium levels to baseline following ATP-induced release of calcium from endoplasmic reticulum (ER) stores. Furthermore, NNAT expression was associated with increased cytotoxicity in OS cells from thapsigargin, an inhibitor of calcium reuptake into ER and an inducer of the ER stress response. These results suggest a possible tumor suppressor role for NNAT in human osteosarcoma. Additional study is needed ascertain sensitization to ER stress-associated apoptosis as a mechanism of NNAT-dependent cytotoxicity. In that case, epigenetic modification therapy to effect NNAT transcriptional derepression may represent a therapeutic strategy potentially of benefit to a majority of osteosarcoma patients.

Transgenic Overexpression of GPNMB Protects Against MPTP-Induced Neurodegeneration.

Parkinson's disease (PD) is a progressive neurodegenerative disease highlighted by a marked loss of dopaminergic cell loss and motor disturbances. Currently, there are no drugs that slow the progression of the disease. A myriad of factors have been implicated in the pathogenesis and progression of PD including neuroinflammation. Although anti-inflammatory agents are being evaluated as potential disease-modifying therapies for PD, none has proven effective to date, suggesting that new and novel targets are needed. Glycoprotein nonmetastatic melanoma protein B (GPNMB) is a transmembrane glycoprotein that has recently been shown to reduce inflammation in astrocytes and to be increased in post-mortem PD brain samples. Here we show that transgenic overexpression of GPNMB protects against dopaminergic neurodegeneration in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropridine mouse model of Parkinson's disease. Furthermore, GPNMB overexpression reduces gliosis and prevented microglial morphological changes following MPTP treatment compared with wild-type MPTP-treated mice. Additionally, recombinant GPNMB attenuates LPS-induced inflammation in primary mouse microglia. These results suggest a neuroprotective and anti-inflammatory role for GPNMB and warrant further investigation for GPNMB as a novel therapy for PD.

Bone mineral density in adolescent urinary stone formers: is sex important?

Urinary stone disease (USD) is affecting a greater number of children and low bone mineral density (BMD) and increased skeletal fractures have been demonstrated in stone patients; however, the mechanism(s) driving bone disease remain unclear. This pilot study was undertaken to assess an adolescent kidney stone cohort's BMD and evaluate for an inverse correlation between BMD and urine concentration of lithogenic minerals and/or inflammatory levels. Prospective case-control study was carried out at a large pediatric center. 15 participants with USD (12-18 years of age, 8 female) were matched by age, sex, and body mass index to 15 controls. Lumbar and total body BMD z-score did not differ between groups. When stone formers were separated by sex, there was a significant difference between male stone formers vs. controls total body BMD z-score (Fig. 1). BMD z-score did not significantly correlate with urine calcium, oxalate, citrate or magnesium. Higher urine IL-13 did significantly correlate with higher total body BMD z-score (r = 0.677, p = 0.018). Total body BMD z-score did significantly correlate with body mass index (BMI) as expected for the control group (r = 0.6321, p = 0.0133). However, this relationship was not present in the USD group (r = - 0.1629, p = 0.5619). This is a small but hypothesis-generating study which demonstrates novel evidence of male-specific low BMD in adolescent stone formers. Furthermore, we demonstrated a positive association between urine IL-13 and total body BMD z-score USD patients as well as a lack of a positive BMD and BMI correlations in stone formers.

A novel regulatory role of TRAPPC9 in L-plastin-mediated osteoclast actin ring formation.

Trafficking protein particle complex 9 (TRAPPC9) is a major subunit of the TRAPPII complex. TRAPPC9 has been reported to bind nuclear factor κB kinase subunit ß (IKKß) and NF-kB-inducing kinase (NIK) where it plays a role in the canonical and noncanonical of nuclear factor-κB (NF-kB) signaling pathways, receptively. The role of TRAPPC9 in protein trafficking and cytoskeleton organization in osteoclast (OC) has not been studied yet. In this study, we examined the mRNA expression of TRAPPC9 during OC differentiation. Next, we examined the colocalization of TRAPPC9 with cathepsin-K, known to mediate OC resorption suggesting that TRAPPC9 mediates the trafficking pathway within OC. To identify TRAPPC9 protein partners important for OC-mediated cytoskeleton re-organization, we conducted immunoprecipitation of TRAPPC9 in mature OCs followed by mass spectrometry analysis. Our data showed that TRAPPC9 binds various protein partners. One protein with high recovery rate is L-plastin (LPL). LPL localizes at the podosomes and reported to play a crucial role in actin aggregation thereby actin ring formation and OC function. Although the role of LPL in OC-mediated bone resorption has not fully reported in detail. Here, first, we confirmed the binding of LPL to TRAPPC9 and, then, we investigated the potential regulatory role of TRAPPC9 in LPL-mediated OC cytoskeleton reorganization. We assessed the localization of TRAPPC9 and LPL in OC and found that TRAPPC9 is colocalized with LPL at the periphery of OC. Next, we determined the effect of TRAPPC9 overexpression on LPL recruitment to the actin ring using a viral system. Interestingly, our data showed that TRAPPC9 overexpression promotes the recruitment of LPL to the actin ring when compared with control cultures. In addition, we observed that TRAPPC9 overexpression reorganizes actin clusters/aggregates and regulates vinculin recruitment into the OC periphery to initiate podosome formation.

Adolescents with urinary stones have elevated urine levels of inflammatory mediators.

Urinary stones are increasing in children, primarily during adolescence. Although urinary stones are often viewed in the context of intermittent stone events, increasing evidence indicates that stones are a metabolic process associated with chronic kidney disease and cardiovascular disease. These aforementioned stone-associated conditions may have pediatric origins. To compare urine inflammatory markers in otherwise healthy stone forming children versus matched controls. Urine samples were collected from 12 adolescents with urinary stones along with 15 controls. The levels of 30 urine cytokines were measured using a Mesoscale 30-Plex Human Cytokine panel and normalized to urine creatinine levels. Macrophage inflammatory protein 1ß and interleukin 13 levels were significantly elevated in the urine of the stone forming adolescents compared to controls. Interleukin 17A was elevated in the urine of controls. This study indicates that urine levels of cytokines involved in chronic inflammation and fibrosis are elevated in urinary stone formers as early as adolescence. Because stone formers are at risk for chronic kidney disease, macrophage inflammatory protein 1ß and interleukin 13 represent investigative targets.

Autophagy plays an essential role in bone homeostasis.

Autophagy is very critical for multiple cellular processes. Autophagy plays a critical role in bone cell differentiation and function.

Comparison of Risk Factors for Pediatric Kidney Stone Formation: The Effects of Sex.

Background: Urinary stones are affecting more children, and pediatric stone formers have unique pathophysiology compared to adults. While adult stone formers are most frequently male, children have an age dependent sex prevalence. Under 10 years, a majority of stone formers are boys; adolescent stone formers are mostly female. Previous adult studies have shown that stone composition is influenced by the sex and age of the stone former. Thus, we hypothesize that female and male stone forming children will also have sex and age specific stone phenotypes. Methods: Retrospective chart review of a large pediatric center's stone forming children 6/1/2009 to 6/1/2016. Patients were identified by ICD 9 codes: N20, N20.1, and N20.9. Charts were reviewed for radiographic evidence of stones or documented visualized stone passage. Results: One hundred and thirty six subjects: 54 males and 82 females. Females were older, median age 14 years [interquartile range (IQR): 11, 15] vs. males' median age 12 years (IQR: 11, 14) (p < 0.01). Females had lower height z-scores, median 0.2 (IQR: -0.8, 0.8) vs. males' median 0.8 (IQR: -0.2, 1.8) (p < 0.01). Presenting symptoms were similar except flank pain affecting 39% of females vs. 22% of males (p = 0.04). Leukocyte esterase was positive in more females than males (33 vs. 4%) (p < 0.001). Males had a higher BUN/Cr ratio, mean ± standard deviation of 19.8 ± 6.3 vs. 16.6 ± 6.5 in females (p = 0.01). Glomerular hyperfiltration was present in 9% of patients while 35% of patients had estimated glomerular filtration rate (eGFR) < 90 ml/min/1.73 m2. Treatment strategies and clinical course were similar except females were told to increase dietary citrate more frequently than males (21 vs. 4%) (p < 0.01). Conclusion: We have provided a novel analysis and demonstrated that low height z-score and pyuria are more common in female stone formers. We have also shown that 9% of pediatric stone formers have labs consistent with hyperfiltration. Whether high protein intake and/or chronic dehydration are associated with hyperfiltration and long-term renal function in children with kidney stones will be an area for future research.

TRAPPC9: Novel insights into its trafficking and signaling pathways in health and disease (Review).

Trafficking protein particle complex 9 (TRAPPC9) is a protein subunit of the transport protein particle II (TRAPPII), which has been reported to be important in the trafficking of cargo from the endoplasmic reticulum (ER) to the Golgi, and in intra­Golgi and endosome­to­Golgi transport in yeast cells. In mammalian cells, TRAPPII has been shown to be important in Golgi vesicle tethering and intra­Golgi transport. TRAPPC9 is considered to be a novel molecule capable of modulating the activation of nuclear factor­κB (NF­κB). Mutations in TRAPPC9 have been linked to a rare consanguineous hereditary form of mental retardation, as part of the NF­κB pathways. In addition, TRAPPC9 has been reported to be involved in breast and colon cancer and liver diseases. The present review highlights the most recent publications on the structure, expression and function of TRAPPC9, and its association with various human diseases.

The glycoprotein GPNMB attenuates astrocyte inflammatory responses through the CD44 receptor.

BACKGROUND: Neuroinflammation is one of the hallmarks of neurodegenerative diseases, such as Parkinson's disease (PD). Activation of glial cells, including microglia and astrocytes, is a characteristic of the inflammatory response. Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane glycoprotein that releases a soluble signaling peptide when cleaved by ADAM10 or other extracellular proteases. GPNMB has demonstrated a neuroprotective role in animal models of ALS and ischemia. However, the mechanism of this protection has not been well established. CD44 is a receptor expressed on astrocytes that can bind GPNMB, and CD44 activation has been demonstrated to reduce NFκB activation and subsequent inflammatory responses in macrophages. GPNMB signaling has not been investigated in models of PD or specifically in astrocytes. More recently, genetic studies have linked polymorphisms in GPNMB with risk for PD. Therefore, it is important to understand the role this signaling protein plays in PD. METHODS: We used data mining techniques to evaluate mRNA expression of GPNMB and its receptor CD44 in the substantia nigra of PD and control brains. Immunofluorescence and qPCR techniques were used to assess GPNMB and CD44 levels in mice treated with MPTP. In vitro experiments utilized the immortalized mouse astrocyte cell line IMA2.1 and purified primary mouse astrocytes. The effects of recombinant GPNMB on cytokine-induced astrocyte activation was determined by qPCR, immunofluorescence, and measurement of nitric oxide and reactive oxygen production. RESULTS: Increased GPNMB and CD44 expression was observed in the substantia nigra of human PD brains and in GFAP-positive astrocytes in an animal model of PD. GPNMB treatment attenuated cytokine-induced levels of inducible nitric oxide synthase, nitric oxide, reactive oxygen species, and the inflammatory cytokine IL-6 in an astrocyte cell line and primary mouse astrocytes. Using primary mouse astrocytes from CD44 knockout mice, we found that the anti-inflammatory effects of GPNMB are CD44-mediated. CONCLUSIONS: These results demonstrate that GPNMB may exert its neuroprotective effect through reducing astrocyte-mediated neuroinflammation in a CD44-dependent manner, providing novel mechanistic insight into the neuroprotective properties of GPNMB.

Osteoactivin regulates head and neck squamous cell carcinoma invasion by modulating matrix metalloproteases.

Nearly 60% of patients with head and neck squamous cell carcinoma (HNSCC) die of metastases or locoregional recurrence. Metastasis is mediated by cancer cell migration and invasion, which are in part dependent on extracellular matrix degradation by matrix metalloproteinases. Osteoactivin (OA) overexpression plays a role in metastases in several malignancies, and has been shown to upregulate matrix metalloproteinase (MMP) expression and activity. To determine how OA modulates MMP expression and activity in HNSCC, and to investigate OA effects on cell invasion, we assessed effects of OA treatment on MMP mRNA and protein expression, as well as gelatinase and caseinolytic activity in HNSCC cell lines. We assessed the effects of OA gene silencing on MMP expression, gelatinase and caseinolytic activity, and cell invasion. OA treatment had differential effects on MMP mRNA expression. OA treatment upregulated MMP-10 expression in UMSCC14a (p = 0.0431) and SCC15 (p < 0.0001) cells, but decreased MMP-9 expression in UMSCC14a cells (p = 0.0002). OA gene silencing decreased MMP-10 expression in UMSCC12 cells (p = 0.0001), and MMP-3 (p = 0.0005) and -9 (p = 0.0036) expression in SCC25 cells. In SCC15 and SCC25 cells, OA treatment increased MMP-2 (p = 0.0408) and MMP-9 gelatinase activity (p < 0.0001), respectively. OA depletion decreased MMP-2 (p = 0.0023) and -9 (p < 0.0001) activity in SCC25 cells. OA treatment increased 70 kDa caseinolytic activity in UMSCC12 cells consistent with tissue type plasminogen activator (p = 0.0078). OA depletion decreased invasive capacity of UMSCC12 cells (p < 0.0001). OA's effects on MMP expression in HNSCC are variable, and may promote cancer cell invasion.