Potent inhibition of cartilage biosynthesis by coincubation with joint capsule through an IL-1-independent pathway

The reason for the increased risk for development of osteoarthritis (OA) after acute joint trauma is not well understood, but the mechanically injured cartilage may be more susceptible to degradative mediators secreted by other tissues in the joint. To establish a model for such interactions, we coincubated bovine cartilage tissue explants together with normal joint capsule and found a profound (∼70%) reduction in cartilage proteoglycan biosynthesis. This reduction is due to release by the joint capsule of a heat-labile and non-toxic factor. Surprisingly, while cultured synovium is a canonical source of interleukin-1 (IL-1), blockade either by soluble IL-1 type II receptor (sIL-1r) or IL-1 receptor antagonist (IL-1RA) had no effect. Combined blockade of IL-1 and tumor necrosis factor α (TNF-α) also had no effect. To support the clinical relevance of the findings, we harvested joint capsule from post-mortem human knees. Human joint capsule from a normal adult knee also released a substance that caused an ∼40% decrease in cartilage proteoglycan biosynthesis. Furthermore, this inhibition was not affected by IL-1 blockade with either sIL-1r or IL-1RA. These results suggest that joint capsule tissue from a normal knee joint can release an uncharacterized cytokine that potently inhibits cartilage biosynthetic activity by an IL-1- and TNF-independent pathway.Whitaker FoundationGlaxoSmithKlineNational Institutes of Health (U.S.) (grant AR-45779)National Institutes of Health (U.S.). Specialized Centers Of Interdisciplinary Research (grant ARP50-39239

Intra-articular Injection of HB-IGF-1 Sustains Delivery of IGF-1 to Cartilage through Binding to Chondroitin Sulfate

Objective: Insulin-like growth factor 1 (IGF-1) stimulates cartilage repair but is not a practical therapy due to its short half-life. We have previously modified IGF-1 by adding a heparin-binding domain and have shown that this fusion protein (HB-IGF-1) stimulates sustained proteoglycan synthesis in cartilage. This study was undertaken to examine the mechanism by which HB-IGF-1 is retained in cartilage and to test whether HB-IGF-1 provides sustained growth factor delivery to cartilage in vivo and to human cartilage explants. Methods: Retention of HB-IGF-1 and IGF-1 was analyzed by Western blotting. The necessity of heparan sulfate (HS) or chondroitin sulfate (CS) glycosaminoglycans (GAGs) for binding was tested using enzymatic removal and cells with genetic deficiency of HS. Binding affinities of HB-IGF-1 and IGF-1 proteins for isolated GAGs were examined by surface plasmon resonance and enzyme-linked immunosorbent assay. Results: In cartilage explants, chondroitinase treatment decreased binding of HB-IGF-1, whereas heparitinase had no effect. Furthermore, HS was not necessary for HB-IGF-1 retention on cell monolayers. Binding assays showed that HB-IGF-1 bound both CS and HS, whereas IGF-1 did not bind either. After intraarticular injection in rat knees, HB-IGF-1 was retained in articular and meniscal cartilage, but not in tendon, consistent with enhanced delivery to CS-rich cartilage. Finally, HB-IGF-1 was retained in human cartilage explants but IGF-1 was not. Conclusion: Our findings indicate that after intraarticular injection in rats, HB-IGF-1 is specifically retained in cartilage through its high abundance of CS. Modification of growth factors with heparin-binding domains may be a new strategy for sustained and specific local delivery to cartilage.National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant EB-003805)National Institute of Arthritis and Musculoskeletal and Skin Diseases (U.S.) (Grant AR-045779

Delivering Heparin-Binding Insulin-Like Growth Factor 1 with Self-Assembling Peptide Hydrogels

Heparin-binding insulin-like growth factor 1 (HB-IGF-1) is a fusion protein of IGF-1 with the HB domain of heparin-binding epidermal growth factor-like growth factor. A single dose of HB-IGF-1 has been shown to bind specifically to cartilage and to promote sustained upregulation of proteoglycan synthesis in cartilage explants. Achieving strong integration between native cartilage and tissue-engineered cartilage remains challenging. We hypothesize that if a growth factor delivered by the tissue engineering scaffold could stimulate enhanced matrix synthesis by both the cells within the scaffold and the adjacent native cartilage, integration could be enhanced. In this work, we investigated methods for adsorbing HB-IGF-1 to self-assembling peptide hydrogels to deliver the growth factor to encapsulated chondrocytes and cartilage explants cultured with growth factor-loaded hydrogels. We tested multiple methods for adsorbing HB-IGF-1 in self-assembling peptide hydrogels, including adsorption prior to peptide assembly, following peptide assembly, and with/without heparan sulfate (HS, a potential linker between peptide molecules and HB-IGF-1). We found that HB-IGF-1 and HS were retained in the peptide for all tested conditions. A subset of these conditions was then studied for their ability to stimulate increased matrix production by gel-encapsulated chondrocytes and by chondrocytes within adjacent native cartilage. Adsorbing HB-IGF-1 or IGF-1 prior to peptide assembly was found to stimulate increased sulfated glycosaminoglycan per DNA and hydroxyproline content of chondrocyte-seeded hydrogels compared with basal controls at day 10. Cartilage explants cultured adjacent to functionalized hydrogels had increased proteoglycan synthesis at day 10 when HB-IGF-1 was adsorbed, but not IGF-1. We conclude that delivery of HB-IGF-1 to focal defects in cartilage using self-assembling peptide hydrogels is a promising technique that could aid cartilage repair via enhanced matrix production and integration with native tissue.National Science Foundation (U.S.). Graduate Research Fellowship ProgramNational Institutes of Health (U.S.) (Grant EB003805)National Institutes of Health (U.S.) (Grant AR060331)Whitaker Health Sciences Fund FellowshipMassachusetts Life Sciences CenterBiomeasure, Inc

A practical approach for outdoors distributed target localization in wireless sensor networks

Wireless sensor networks are posed as the new communication paradigm where the use of small, low-complexity, and low-power devices is preferred over costly centralized systems. The spectra of potential applications of sensor networks is very wide, ranging from monitoring, surveillance, and localization, among others. Localization is a key application in sensor networks and the use of simple, efficient, and distributed algorithms is of paramount practical importance. Combining convex optimization tools with consensus algorithms we propose a distributed localization algorithm for scenarios where received signal strength indicator readings are used. We approach the localization problem by formulating an alternative problem that uses distance estimates locally computed at each node. The formulated problem is solved by a relaxed version using semidefinite relaxation technique. Conditions under which the relaxed problem yields to the same solution as the original problem are given and a distributed consensusbased implementation of the algorithm is proposed based on an augmented Lagrangian approach and primaldual decomposition methods. Although suboptimal, the proposed approach is very suitable for its implementation in real sensor networks, i.e., it is scalable, robust against node failures and requires only local communication among neighboring nodes. Simulation results show that running an additional local search around the found solution can yield performance close to the maximum likelihood estimate

Progress of children with severe acute malnutrition in the malnutrition treatment centre rehabilitation program: evidence from a prospective study in Jharkhand, India

Background In Jharkhand, Malnutrition Treatment Centres (MTCs) have been established to provide care to children with severe acute malnutrition (SAM). The study examined the effects of facility- and community based care provided as part the MTC program on children with severe acute malnutrition. Method A cohort of 150 children were enrolled and interviewed by trained investigators at admission, discharge, and after two months on the completion of the community-based phase of the MTC program. Trained investigators collected data on diet, morbidity, anthropometry, and utilization of health and nutrition services. Results We found no deaths among children attending the MTC program. Recovery was poor, and the majority of children demonstrated poor weight gain, with severe wasting and underweight reported in 52 and 83% of the children respectively at the completion of the community-based phase of the MTC program. The average weight gain in the MTC facility (3.8 ± 5.9 g/kg body weight/d) and after discharge (0.6 ± 2.1 g/kg body weight/d) was below recommended standards. 67% of the children consumed food that met less than 50% of the recommended energy and protein requirement. Children experienced high number of illness episodes after discharge: 68% children had coughs and cold, 40% had fever and 35% had diarrhoea. Multiple morbidities were common: 50% of children had two or more episodes of illness. Caregiver’s exposure to MTC’s health and nutrition education sessions and meetings with frontline workers did not improve feeding practices at home. The take-home ration amount distributed to children through the supplementary food program was inadequate to achieve growth benefits. Conclusions Recovery of children during and after the MTC program was suboptimal. This highlights the need for additional support to strengthen MTC program so that effective care to children can be provided

AMP-Activated Protein Kinase (AMPK) Mediates Nutrient Regulation of Thioredoxin-Interacting Protein (TXNIP) in Pancreatic Beta-Cells

Thioredoxin-interacting protein (TXNIP) regulates critical biological processes including inflammation, stress and apoptosis. TXNIP is upregulated by glucose and is a critical mediator of hyperglycemia-induced beta-cell apoptosis in diabetes. In contrast, the saturated long-chain fatty acid palmitate, although toxic to the beta-cell, inhibits TXNIP expression. The mechanisms involved in the opposing effects of glucose and fatty acids on TXNIP expression are unknown. We found that both palmitate and oleate inhibited TXNIP in a rat beta-cell line and islets. Palmitate inhibition of TXNIP was independent of fatty acid beta-oxidation or esterification. AMP-activated protein kinase (AMPK) has an important role in cellular energy sensing and control of metabolic homeostasis; therefore we investigated its involvement in nutrient regulation of TXNIP. As expected, glucose inhibited whereas palmitate stimulated AMPK. Pharmacologic activators of AMPK mimicked fatty acids by inhibiting TXNIP. AMPK knockdown increased TXNIP expression in presence of high glucose with and without palmitate, indicating that nutrient (glucose and fatty acids) effects on TXNIP are mediated in part via modulation of AMPK activity. TXNIP is transcriptionally regulated by carbohydrate response element-binding protein (ChREBP). Palmitate inhibited glucose-stimulated ChREBP nuclear entry and recruitment to the Txnip promoter, thereby inhibiting Txnip transcription. We conclude that AMPK is an important regulator of Txnip transcription via modulation of ChREBP activity. The divergent effects of glucose and fatty acids on TXNIP expression result in part from their opposing effects on AMPK activity. In light of the important role of TXNIP in beta-cell apoptosis, its inhibition by fatty acids can be regarded as an adaptive/protective response to glucolipotoxicity. The finding that AMPK mediates nutrient regulation of TXNIP may have important implications for the pathophysiology and treatment of diabetes

Transport and binding of tumor necrosis factor-α in articular cartilage depend on its quaternary structure

The effect of tumor necrosis factor-α (TNFα) on cartilage matrix degradation is mediated by its transport and binding within the extracellular matrix (ECM) of the tissue, which mediates availability to cell receptors. Since the bioactive form of TNFα is a homotrimer of monomeric subunits, conversion between trimeric and monomeric forms during intratissue transport may affect binding to ECM and, thereby, bioactivity within cartilage. We studied the transport and binding of TNFα in cartilage, considering the quaternary structure of this cytokine. Competitive binding assays showed significant binding of TNFα in cartilage tissue, leading to an enhanced uptake. However, studies in which TNFα was cross-linked to remain in the trimeric form revealed that the binding of trimeric TNFα was negligible. Thus, binding of TNFα to ECM was associated with the monomeric form. Binding of TNFα was not disrupted by pre-treating cartilage tissue with trypsin, which removes proteoglycans and glycoproteins but leaves the collagen network intact. Therefore, proteoglycan loss during osteoarthritis should only alter the passive diffusion of TNFα but not its binding interaction with the remaining matrix. Our results suggest that matrix binding and trimer–monomer conversion of TNFα both play crucial roles in regulating the accessibility of bioactive TNFα within cartilage.National Institute of Arthritis and Musculoskeletal and Skin Diseases (U.S.) (Grant AR45779)National Institute of Arthritis and Musculoskeletal and Skin Diseases (U.S.) (Grant AR60331