Implementation of point-of-care molecular testing for respiratory viruses in congregate living settings

OBJECTIVE

To implement and evaluate a point-of-care (POC) molecular testing platform for respiratory viruses in congregate living settings (CLS).

DESIGN

Prospective quality improvement study.

SETTING

Seven CLS, including three nursing homes and four independent-living facilities.

PARTICIPANTS

Residents of CLS.

METHODS

A POC platform for COVID-19, influenza A and B, and respiratory syncytial virus was implemented at participating CLS from December 1, 2022 to April 15, 2023. Residents with respiratory symptoms underwent paired testing, with respiratory specimens tested first with the POC platform and then delivered to an off-site laboratory for multiplex respiratory virus panel (MRVP) polymerase chain reaction (PCR) as per standard protocol. Turn-around time and diagnostic accuracy of the POC platform were compared against MRVP PCR. In an exploratory analysis, time to outbreak declaration among participating CLS was compared against a convenience sample of 19 CLS that did not use the POC platform.

RESULTS

A total of 290 specimens that underwent paired testing were included. Turn-around time to result was significantly shorter with the POC platform compared to MRVP PCR, with median difference of 36.2 hours (interquartile range 21.8-46.4 hours). The POC platform had excellent diagnostic accuracy compared to MRVP PCR, with area under the curve statistic of .96. Time to outbreak declaration was shorter in CLS that used the POC platform compared to CLS that did not.

CONCLUSION

Rapid POC testing platforms for respiratory viruses can be implemented in CLS, with high diagnostic accuracy, expedited turn-around times, and shorter time to outbreak declaration.

Predictors of SARS-CoV-2 transmission in congregate living settings: a multicenter prospective study

BACKGROUND

Older adults residing in congregate living settings (CLS) such as nursing homes and independent living facilities remain at increased risk of morbidity and mortality from coronavirus disease 2019. We performed a prospective multicenter study of consecutive severe acute respiratory coronavirus virus 2 (SARS-CoV-2) exposures to identify predictors of transmission in this setting.

METHODS

Consecutive resident SARS-CoV-2 exposures across 17 CLS were prospectively characterized from 1 September 2022 to 1 March 2023, including factors related to environment, source, and exposed resident. Room size, humidity, and ventilation were measured in locations where exposures occurred. Predictors were incorporated in a generalized estimating equation model adjusting for the correlation within CLS.

RESULTS

Among 670 consecutive exposures to SARS-CoV-2 across 17 CLS, transmission occurred among 328 (49.0%). Increased risk was associated with nursing homes (odds ratio (OR) = 90.8; 95% CI, 7.8-1047.4), Jack and Jill rooms (OR = 2.2; 95% CI, 1.3-3.6), from source who was pre-symptomatic (OR = 11.2; 95% CI, 4.1-30.9), symptomatic (OR = 6.5; 95% CI, 1.4-29.9), or rapid antigen test positive (OR = 35.6; 95% CI, 5.6-225.6), and in the presence of secondary exposure (OR = 6.3; 95% CI, 1.6-24.0). Exposure in dining room was associated with reduced risk (OR = 0.02; 95% CI, 0.005-0.08) as was medium room size (OR = 0.3; 95% CI, 0.2-0.6). Recent vaccination of exposed resident (OR = 0.5; 95% CI, 0.3-1.0) and increased ventilation of room (OR = 0.9; 95% CI, 0.8-1.0) were marginally associated with reduced risk.

CONCLUSION

Prospective assessment of SARS-CoV-2 exposures in CLS suggests that source characteristics and location of exposure are most predictive of resident transmission. These findings can inform risk assessment and further opportunities to prevent transmission in CLS.

Regulation of Versican Expression in Macrophages is Mediated by Canonical Type I Interferon Signaling via ISGF3

Growing evidence supports a role for versican as an important component of the inflammatory response, with both pro- and anti-inflammatory roles depending on the specific context of the system or disease under investigation. Our goal is to understand the regulation of macrophage-derived versican and the role it plays in innate immunity. In previous work, we showed that LPS triggers a signaling cascade involving TLR4, the Trif adaptor, type I interferons, and the type I interferon receptor, leading to increased versican expression by macrophages. In the present study, we used a combination of chromatin immunoprecipitation, siRNA, chemical inhibitors, and mouse model approaches to investigate the regulatory events downstream of the type I interferon receptor to better define the mechanism controlling versican expression. Results indicate that transcriptional regulation by canonical type I interferon signaling via the heterotrimeric transcription factor, ISGF3, controls versican expression in macrophages exposed to LPS. This pathway is not dependent on MAPK signaling, which has been shown to regulate versican expression in other cell types. The stability of versican mRNA may also contribute to prolonged versican expression in macrophages. These findings strongly support a role for macrophage-derived versican as a type I interferon-stimulated gene and further our understanding of versican's role in regulating inflammation.

Inter-alpha-trypsin inhibitor (IαI) and hyaluronan modifications enhance the innate immune response to influenza virus in the lung

The inter-alpha-trypsin inhibitor (IαI) complex is composed of the bikunin core protein with a single chondroitin sulfate (CS) attached and one or two heavy chains (HCs) covalently linked to the CS chain. The HCs from IαI can be transferred to hyaluronan (HA) through a TNFα-stimulated gene-6 (TSG-6) dependent process to form an HC•HA matrix. Previous studies reported increased IαI, HA, and HC•HA complexes in mouse bronchoalveolar lavage fluid (BALF) post-influenza infection. However, the expression and incorporation of HCs into the HA matrix of the lungs during the clinical course of influenza A virus (IAV) infection and the biological significance of the HC•HA matrix are poorly understood. The present study aimed to better understand the composition of HC•HA matrices in mice infected with IAV and how these matrices regulate the host pulmonary immune response. In IAV infected mice bikunin, HC1-3, TSG-6, and HAS1-3 all show increased gene expression at various times during a 12-day clinical course. The increased accumulation of IαI and HA was confirmed in the lungs of infected mice using immunohistochemistry and quantitative digital pathology. Western blots confirmed increases in the IαI components in BALF and lung tissue at 6 days post-infection (dpi). Interestingly, HCs and bikunin recovered from BALF and plasma from mice 6 dpi with IAV, displayed differences in the HC composition by Western blot analysis and differences in bikunin's CS chain sulfation patterns by mass spectrometry analysis. This strongly suggests that the IαI components were synthesized in the lungs rather than translocated from the vascular compartment. HA was significantly increased in BALF at 6 dpi, and the HA recovered in BALF and lung tissues were modified with HCs indicating the presence of an HC•HA matrix. In vitro experiments using polyinosinic-polycytidylic acid (poly(I:C)) treated mouse lung fibroblasts (MLF) showed that modification of HA with HCs increased cell-associated HA, and that this increase was due to the retention of HA in the MLF glycocalyx. In vitro studies of leukocyte adhesion showed differential binding of lymphoid (Hut78), monocyte (U937), and neutrophil (dHL60) cell lines to HA and HC•HA matrices. Hut78 cells adhered to immobilized HA in a size and concentration-dependent manner. In contrast, the binding of dHL60 and U937 cells depended on generating a HC•HA matrix by MLF. Our in vivo findings, using multiple bronchoalveolar lavages, correlated with our in vitro findings in that lymphoid cells bound more tightly to the HA-glycocalyx in the lungs of influenza-infected mice than neutrophils and mononuclear phagocytes (MNPs). The neutrophils and MNPs were associated with a HC•HA matrix and were more readily lavaged from the lungs. In conclusion, this work shows increased IαI and HA accumulation and the formation of a HC•HA matrix in mouse lungs post-IAV infection. The formation of HA and HC•HA matrices could potentially create specific microenvironments in the lungs for immune cell recruitment and activation during IAV infection.

Influenza outbreak management tabletop exercise for congregate living settings

We conducted a tabletop exercise on influenza outbreak preparedness that engaged a large group of congregate living settings (CLS), with improvements in self-reported knowledge and readiness. This proactive approach to responding to communicable disease threats has potential to build infection prevention and control capacity beyond COVID-19 in the CLS sector.

Cross-cultural translation into Chinese and psychometric evaluation of a screening tool for nocturia: the Targeting the individual's Aetiology of Nocturia to Guide Outcomes (TANGO) questionnaire

INTRODUCTION

We conducted translation and psychometric validation of a self-administered, 22-item dichotomous response-based questionnaire to identify nocturia aetiologies and co-morbidities in adult patients.

METHODS

The Targeting the individual's Aetiology of Nocturia to Guide Outcomes (TANGO) questionnaire was forward- and backward-translated, then finalised using a standardised methodology. The resulting version, a Chinese version of the TANGO [TANGO (CV)], was evaluated for internal consistency, test-retest reliability, content validity, convergent validity, criterion validity, and discriminant validity via responses from 65 participants (46 men and 19 women; mean age, 67 years, range, 50-88), in comparison with other validated questionnaires and a 4-day bladder/sleep diary.

RESULTS

Only 0.4% of responses were missing; 3% of participants required assistance with comprehension. The Kuder-Richardson Formula 20 (KR-20) coefficient for the whole tool was 0.711. Kappa values for individual domains and the whole tool varied from 0.871 to 0.866, indicating satisfactory test-retest reliability. There was strong agreement between the sum of positive responses to each domain and the whole tool (intra-class correlation coefficient=0.878-1.000). Modest correlations (ρ=0.4-0.6) were detected between the tool and bladder/sleep diary-based parameters for convergent validity. Criterion validity was confirmed for each domain and the whole tool [ρ=0.287-0.687]. In receiver operating characteristic analysis, the tool could distinguish patients (≥2 nocturia episodes/night) from controls (≤1 nocturia episode/night) [Youden's J statistic=0.453, area under the curve=0.818, 95% confidence interval (CI)=0.683-0.953] and patients with significant nocturia distress from patients with mild nocturia distress (Youden's J statistic=0.398, area under the curve=0.729, 95% CI=0.581-0.878).

CONCLUSION

The TANGO (CV) was formally crossculturally adapted and translated. Its psychometric properties (except sensitivity to change) were validated.

Recommendations for the management of advanced and metastatic renal cell carcinoma: joint consensus statements from the Hong Kong Urological Association and the Hong Kong Society of Uro-Oncology

INTRODUCTION

Kidney cancer, primarily renal cell carcinoma (RCC), ranks among the top 10 most common malignancies in the male population of Hong Kong. In 2019, members of two medical societies in Hong Kong formed an expert panel to establish a set of consensus statements for the management of metastatic RCC. On 22 June 2021, the same panel met to review recent evidence and reassess their positions regarding the management of advanced and metastatic RCC, with the aim of providing recommendations for physicians in Hong Kong.

PARTICIPANTS

The panel included 12 experts (6 clinical oncologists and 6 urologists) who had extensive experience managing patients with RCC in Hong Kong.

EVIDENCE

The panel reviewed randomised controlled trials, observational studies, systematic reviews/meta-analyses, and international clinical guidelines to address key clinical questions that were identified before the meeting.

CONSENSUS PROCESS

In total, 15 key clinical questions were identified before the meeting, covering the surgical and systemic treatment of advanced or metastatic clear cell, sarcomatoid, and non-clear cell RCCs. At the meeting, the panellists voted on these questions, then discussed relevant evidence and practical considerations.

CONCLUSIONS

The treatment landscape for advanced and metastatic RCC continues to evolve. More immune checkpoint inhibitor (ICI)-based combination regimens will be indicated for the treatment of metastatic clear cell RCC. There is increasing evidence concerning the benefit of adjuvant ICI treatment for resected advanced RCC. This article summarises recent evidence and expert insights regarding a series of key clinical questions about the management of advanced and metastatic RCC.

Revealing directed effective connectivity of cortical neuronal networks from measurements

In the study of biological networks, one of the major challenges is to understand the relationships between network structure and dynamics. In this paper, we model in vitro cortical neuronal cultures as stochastic dynamical systems and apply a method that reconstructs directed networks from dynamics [Ching and Tam, Phys. Rev. E 95, 010301(R) (2017)2470-004510.1103/PhysRevE.95.010301] to reveal directed effective connectivity, namely, the directed links and synaptic weights, of the neuronal cultures from voltage measurements recorded by a multielectrode array. The effective connectivity so obtained reproduces several features of cortical regions in rats and monkeys and has similar network properties as the synaptic network of the nematode Caenorhabditis elegans, whose entire nervous system has been mapped out. The distribution of the incoming degree is bimodal and the distributions of the average incoming and outgoing synaptic strength are non-Gaussian with long tails. The effective connectivity captures different information from the commonly studied functional connectivity, estimated using statistical correlation between spiking activities. The average synaptic strengths of excitatory incoming and outgoing links are found to increase with the spiking activity in the estimated effective connectivity but not in the functional connectivity estimated using the same sets of voltage measurements. These results thus demonstrate that the reconstructed effective connectivity can capture the general properties of synaptic connections and better reveal relationships between network structure and dynamics.

Detection of Glycosaminoglycans in Pancreatic Islets and Lymphoid Tissues

In this chapter, we describe the detection of the glycosaminoglycans hyaluronan and heparan sulfate in pancreatic islets and lymphoid tissues. The identification of hyaluronan in tissues is achieved by utilizing a highly specific hyaluronan binding protein (HABP) probe that interacts with hyaluronan in tissue sections. The HABP probe is prepared by enzymatic digestion of the chondroitin sulfate proteoglycan aggrecan which is present in bovine nasal cartilage and is then biotinylated in the presence of bound hyaluronan and the link protein. Hyaluronan is then removed by gel filtration chromatography. The biotinylated HABP-link protein complex is applied to tissue sections, and binding of the complex to tissue hyaluronan is visualized by enzymatic precipitation of chromogenic substrates.To determine hyaluronan content in tissues, tissues are first proteolytically digested to release hyaluronan from the macromolecular complexes that this molecule forms with other extracellular matrix constituents. Digested tissue is then incubated with HABP . The hyaluronan-HABP complexes are extracted, and the hyaluronan concentration in the tissue is determined using an ELISA-like assay.Historically, heparan sulfate was identified in tissue sections using the cationic dye Alcian blue and histochemistry based on the critical electrolyte concentration principle of differential staining of glycosaminoglycans using salt solutions. For both human and mouse pancreas sections, the current optimal method for detecting heparan sulfate is by indirect immunohistochemistry using a specific anti-heparan sulfate monoclonal antibody. A peroxidase-conjugated secondary antibody is then applied, and its binding to the anti-heparan sulfate antibody is visualized by oxidation and precipitation of a chromogenic substrate.

Information synergy in the anticipatory dynamics of a retina

Anticipation is the phenomenon in which the response of a system is predictive of the stimulation. The encoding of stochastic light intensity (x) into spikes is investigated in an experiment with retinas from bullfrogs to understand the mechanism of anticipation of a retina. Partial information decomposition of the mutual information between the spike rates and the joint state {x,x[over ̇]} is found to be consistent with the encoding by the linear combination of x and x[over ̇] where x[over ̇] is the rate of change of x. This spike rate encoding form indicates that a retina is capable of anticipation based on the synergistic information generation between x and x[over ̇]. Our results suggest that illusions such as the anticipation studied here during retinal perception can originate from the recombination of information extracted in the retinal network.

Autocrine Hyaluronan Influences Sprouting and Lumen Formation During HUVEC Tubulogenesis In Vitro

Although many studies have focused on a role for hyaluronan (HA) of interstitial extracellular matrix (presumably produced by non-vascular "stromal" cells) in regulating vascular growth, we herein examine the influence of "autocrine HA" produced by vascular endothelial cells themselves on tubulogenesis, using human umbilical vein endothelial cells (HUVECs) in angiogenic and vasculogenic three-dimensional collagen gel cultures. Relative to unstimulated controls, tubulogenic HUVECs upregulated HAS2 mRNA and increased the synthesis of cell-associated HA (but not HA secreted into media). Confocal microscopy/immunofluorescence on cultures fixed with neutral-buffered 10% formalin (NBF) revealed cytoplasmic HAS2 in HUVEC cords and tubes. Cultures fixed with NBF (with cetylpyridinium chloride added to retain HA), stained for HA using "affinity fluorescence" (biotinylated HA-binding protein with streptavidin-fluor), and viewed by confocal microscopy showed HA throughout tube lumens, but little/no HA on the abluminal sides of the tubes or in the surrounding collagen gel. Lumen formation in angiogenic and vasculogenic cultures was strongly suppressed by metabolic inhibitors of HA synthesis (mannose and 4-methylumbelliferone). Hyaluronidase strongly inhibited lumen formation in angiogenic cultures, but not in vasculogenic cultures (where developing lumens are not open to culture medium). Collectively, our results point to a role for autocrine, luminal HA in microvascular sprouting and lumen development. (J Histochem Cytochem 69: 415-428, 2021).

Adipocyte-Derived Versican and Macrophage-Derived Biglycan Control Adipose Tissue Inflammation in Obesity

Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammation, here we investigate their role in adipose tissue inflammation in obesity. We find that adipose tissue versican and biglycan increase in obesity. Versican is produced mainly by adipocytes and biglycan by adipose tissue macrophages. Both proteoglycans are also present in adipose tissue from obese human subjects undergoing gastric bypass surgery. Deletion of adipocyte-specific versican or macrophage-specific biglycan in mice reduces macrophage accumulation and chemokine and cytokine expression, although only adipocyte-specific versican deletion leads to sustained improvement in glucose tolerance. Macrophage-derived biglycan activates inflammatory genes in adipocytes. Versican expression increases in cultured adipocytes exposed to excess glucose, and adipocyte-conditioned medium stimulates inflammation in resident peritoneal macrophages, in part because of a versican breakdown product, versikine. These findings provide insights into the role of adipocyte- and macrophage-derived proteoglycans in adipose tissue inflammation in obesity.

Anticipation and negative group delay in a retina

The mechanism of negative group delay (NGD) is used to understand the anticipatory capability of a retina. Experiments with retinas from bullfrogs are performed to compare with the predictions of the NGD model. In particular, whole field stochastic stimulations with various autocorrelation times are used to probe anticipatory responses from the retina. We find that the NGD model can reproduce essential features of experimental observations characterized by the cross correlations between the stimulation and the retinal responses. Experiments with dark light pulse stimulations further support the NGD mechanism, with the retina producing time-advanced pulse responses. However, no time-advanced pulse responses are produced by bright pulses. Counterintuitively, the NGD model shows that it is the delay in the system which gives rise to anticipation because of the negative feedback adaptation mechanism.

A Role for HAPLN1 During Phenotypic Modulation of Human Lung Fibroblasts In Vitro

Hyaluronan and proteoglycan link protein 1 (HAPLN1) stabilizes interactions between two important extracellular matrix (ECM) macromolecules, versican and hyaluronan, which facilitate proliferation of fibroblasts and their conversion to myofibroblasts. However, the role of HAPLN1 in these events has not been studied. Using immunocytochemistry, cellular and ECM locations of HAPLN1 were evaluated in cultured human lung fibroblasts during proliferation and conversion to myofibroblasts. HAPLN1 localized to pericellular matrices, associating with both versican and hyaluronan in the ECM and on the cell surface. Nuclear and total HAPLN1 immunostaining increased after myofibroblast induction. Confocal microscopy showed HAPLN1 predominant in the ECM under cells while versican predominated above cells. Versican and HAPLN1 were also juxtaposed in columnar inclusions in the cytoplasm and nucleus. Nuclear HAPLN1 staining in interphase cells redistributed to the cytosol during mitosis. In the absence of TGF-β1, addition of exogenous bovine HAPLN1 (together with aggrecan G1) facilitated myofibroblast formation, as seen by significant upregulation of α-smooth muscle actin (SMA) staining, while adding full-length bovine versican had no effect. Increased compaction of hyaluronan-rich ECM suggests that HAPLN1 plus G1 addition affects hyaluronan networks and myofibroblast formation. These observations demonstrate changes in both extracellular and intracellular localization of HAPLN1 during fibroblast proliferation and myofibroblast conversion suggesting a possible role in fibrotic remodeling.

Hypothalamic perineuronal net assembly is required for sustained diabetes remission induced by fibroblast growth factor 1 in rats

We recently showed that perineuronal nets (PNNs) enmesh glucoregulatory neurons in the arcuate nucleus (Arc) of the mediobasal hypothalamus (MBH)¹, but whether these PNNs play a role in either the pathogenesis of type 2 diabetes (T2D) or its treatment remains unclear. Here we show that PNN abundance within the Arc is markedly reduced in the Zucker diabetic fatty (ZDF) rat model of T2D, compared with normoglycaemic rats, correlating with altered PNN-associated sulfation patterns of chondroitin sulfate glycosaminoglycans in the MBH. Each of these PNN-associated changes is reversed following a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1) at a dose that induces sustained diabetes remission in male ZDF rats. Combined with previous work localizing this FGF1 effect to the Arc area^2-4, our finding that enzymatic digestion of Arc PNNs markedly shortens the duration of diabetes remission following icv FGF1 injection in these animals identifies these extracellular matrix structures as previously unrecognized participants in the mechanism underlying diabetes remission induced by the central action of FGF1.

Femoral Neck Non-Union - A Biomechanical Solution with Valgus Sliding Subtrochanteric Osteotomy: A Case Report

Avascular necrosis and non-union are two most dreaded complications of femoral neck fracture fixations. Hip replacement seems to be a simple solution for this complex problem. However, the long-term efficacy of prosthetic replacement in the young population with higher functional demand is still questionable. Femoral head preserving valgus subtrochanteric osteotomies in properly selected cases have strong support from literature. The conventional technique of valgus subtrochanteric osteotomy involves lateral based wedge resection. Alternatively, a simpler sliding oblique subtrochanteric osteotomy without any wedge removal can also be performed. We hereby describe a successful case of sliding subtrochanteric osteotomy with 135° dynamic hip screw (DHS) plate fixation in treating non-union neck of femur fracture in a young gentleman.

The synthesis and secretion of versican isoform V3 by mammalian cells: A role for N-linked glycosylation

Versican is a large extracellular matrix (ECM) chondroitin sulfate (CS) proteoglycan found in most soft tissues, which is encoded by the VCAN gene. At least four major isoforms (V0, V1, V2, and V3) are generated via alternative splicing. The isoforms of versican are expressed and accumulate in various tissues during development and disease, where they contribute to ECM structure, cell growth and migration, and immune regulation, among their many functions. While several studies have identified the mRNA transcript for the V3 isoform in a number of tissues, little is known about the synthesis, secretion, and targeting of the V3 protein. In this study, we used lentiviral generation of doxycycline-inducible rat V3 with a C-terminal tag in stable NIH 3T3 cell lines and demonstrated that V3 is processed through the classical secretory pathway. We further show that N-linked glycosylation is required for efficient secretion and solubility of the protein. By site-directed mutagenesis, we identified amino acids 57 and 330 as the active N-linked glycosylation sites on V3 when expressed in this cell type. Furthermore, exon deletion constructs of V3 revealed that exons 11-13, which code for portions of the carboxy region of the protein (G3 domain), are essential for V3 processing and secretion. Once secreted, the V3 protein associates with hyaluronan along the cell surface and within the surrounding ECM. These results establish critical parameters for the processing, solubility, and targeting of the V3 isoform by mammalian cells and establishes a role for V3 in the organization of hyaluronan.

High-molecular weight hyaluronan attenuates tubulointerstitial scarring in kidney injury

Renal fibrosis features exaggerated inflammation, extracellular matrix (ECM) deposition, and peritubular capillary loss. We previously showed that IL-10 stimulates high-molecular weight hyaluronan (HMW-HA) expression by fibroblasts, and we hypothesize that HMW-HA attenuates renal fibrosis by reducing inflammation and ECM remodeling. We studied the effects of IL-10 overexpression on HA production and scarring in mouse models of unilateral ureteral obstruction (UUO) and ischemia/reperfusion (I/R) to investigate whether IL-10 antifibrotic effects are HA dependent. C57BL/6J mice were fed with the HA synthesis inhibitor, 4-methylumbelliferone (4-MU), before UUO. We observed that in vivo injury increased intratubular spaces, ECM deposition, and HA expression at day 7 and onward. IL-10 overexpression reduced renal fibrosis in both models, promoted HMW-HA synthesis and stability in UUO, and regulated cell proliferation in I/R. 4-MU inhibited IL-10-driven antifibrotic effects, indicating that HMW-HA is necessary for cytokine-mediated reduction of fibrosis. We also found that IL-10 induces in vitro HMW-HA production by renal fibroblasts via STAT3-dependent upregulation of HA synthase 2. We propose that IL-10-induced HMW-HA synthesis plays cytoprotective and antifibrotic roles in kidney injury, thereby revealing an effective strategy to attenuate renal fibrosis in obstructive and ischemic pathologies.

Dynamics of beating cardiac tissue under slow periodic drives

Effects of mechanical coupling on cardiac dynamics are studied by monitoring the beating dynamics of a cardiac tissue which is being pulled periodically at a pace slower than its intrinsic beating rate. The tissue is taken from the heart of a bullfrog that includes pacemaker cells. The cardiac tissue beats spontaneously with an almost constant interbeat interval (IBI) when there is no external forcing. On the other hand, the IBI is observed to vary significantly under an external periodic drive. Interestingly, when the period of the external drive is about two times the intrinsic IBI of the tissue without pulling, the IBI as a function of time exhibits a wave packet structure. Our experimental results can be understood theoretically by a phase-coupled model under external driving. In particular, the theoretical prediction of the wave-packet period as a function of the normalized driving period agrees excellently with the observations. Furthermore, the cardiac mechanical coupling constant can be extracted from the experimental data from our model and is found to be insensitive to the external driving period. Implications of our results on cardiac physiology are also discussed.

Respiratory Syncytial Virus Infection of Human Lung Fibroblasts Induces a Hyaluronan-Enriched Extracellular Matrix That Binds Mast Cells and Enhances Expression of Mast Cell Proteases

Human lung fibroblasts (HLFs) treated with the viral mimetic polyinosine-polycytidylic acid (poly I:C) form an extracellular matrix (ECM) enriched in hyaluronan (HA) that avidly binds monocytes and lymphocytes. Mast cells are important innate immune cells in both asthma and acute respiratory infections including respiratory syncytial virus (RSV); however, the effect of RSV on HA dependent mast cell adhesion and/or function is unknown. To determine if RSV infection of HLFs leads to the formation of a HA-enriched ECM that binds and enhances mast cell activity primary HLFs were infected with RSV for 48 h prior to leukocyte binding studies using a fluorescently labeled human mast cell line (LUVA). Parallel HLFs were harvested for characterization of HA production by ELISA and size exclusion chromatography. In separate experiments, HLFs were infected as above for 48 h prior to adding LUVA cells to HLF wells. Co-cultures were incubated for 48 h at which point media and cell pellets were collected for analysis. The role of the hyaladherin tumor necrosis factor-stimulated gene 6 (TSG-6) was also assessed using siRNA knockdown. RSV infection of primary HLFs for 48 h enhanced HA-dependent LUVA binding assessed by quantitative fluorescent microscopy. This coincided with increased HLF HA synthase (HAS) 2 and HAS3 expression and decreased hyaluronidase (HYAL) 2 expression leading to increased HA accumulation in the HLF cell layer and the presence of larger HA fragments. Separately, LUVAs co-cultured with RSV-infected HLFs for 48 h displayed enhanced production of the mast cell proteases, chymase, and tryptase. Pre-treatment with the HA inhibitor 4-methylumbelliferone (4-MU) and neutralizing antibodies to CD44 (HA receptor) decreased mast cell protease expression in co-cultured LUVAs implicating a direct role for HA. TSG-6 expression was increased over the 48-h infection. Inhibition of HLF TSG-6 expression by siRNA knockdown led to decreased LUVA binding suggesting an important role for this hyaladherin for LUVA adhesion in the setting of RSV infection. In summary, RSV infection of HLFs contributes to inflammation via HA-dependent mechanisms that enhance mast cell binding as well as mast cell protease expression via direct interactions with the ECM.

Elevated plasma and synovial fluid interleukin-8 and interleukin-18 may be associated with the pathogenesis of knee osteoarthritis

PURPOSE

Osteoarthritis (OA) of the knee is a multifactorial degenerative disease typically defined as the 'wear and tear' of articular joint cartilage. However, recent studies suggest that OA is a disease arising from chronic low-grade inflammation. We conducted a study to investigate the relationship between chronic inflammatory mediators present in both the systemic peripheral blood system and localised inflammation in synovial fluid (SF) of OA and non-OA knees; and subsequently made direct comparative analyses to understand the mechanisms that may underpin the processes involved in OA.

METHODS

20-Plex proteins were quantified using Human Magnetic Luminex® assay (R&D Systems, USA) from plasma and SF of OA (n = 14) and non-OA (n = 14) patients. Ingenuity Pathway Analysis (IPA) software was used to predict the relationship and possible interaction of molecules pertaining to OA.

RESULTS

There were significant differences in plasma level for matrix metalloproteinase (MMP)-3, interleukin (IL)-27, IL-8, IL-4, tumour necrosis factor-alpha, MMP-1, IL-15, IL-21, IL-10, and IL-1 beta between the groups, as well as significant differences in SF level for IL-15, IL-8, vascular endothelial growth factor (VEGF), MMP-1, and IL-18. Our predictive OA model demonstrated that toll-like receptor (TLR) 2, macrophage migration inhibitory factor (MIF), TLR4 and IL-1 were the main regulators of IL-1B, IL-4, IL-8, IL-10, IL-15, IL-21, IL-27, MMP-1 and MMP-3 in the plasma system; whilst IL-1B, TLR4, IL-1, and basigin (BSG) were the regulators of IL-4, IL-8, IL-10, IL-15, IL-18, IL-21, IL-27, MMP-1, and MMP-3 in the SF system.

CONCLUSION

The elevated plasma IL-8 and SF IL-18 may be associated with the pathogenesis of OA via the activation of MMP-3.