A tissue adaptation model based on strain-dependent collagen degradation and contact-guided cell traction

Soft biological tissues adapt their collagen network to the mechanical environment. Collagen remodeling and cell traction are both involved in this process. The present study presents a collagen adaptation model which includes strain-dependent collagen degradation and contact-guided cell traction. Cell traction is determined by the prevailing collagen structure and is assumed to strive for tensional homeostasis. In addition, collagen is assumed to mechanically fail if it is over-strained. Care is taken to use principally measurable and physiologically meaningful relationships. This model is implemented in a fibril-reinforced biphasic finite element model for soft hydrated tissues. The versatility and limitations of the model are demonstrated by corroborating the predicted transient and equilibrium collagen adaptation under distinct mechanical constraints against experimental observations from the literature. These experiments include overloading of pericardium explants until failure, static uniaxial and biaxial loading of cell-seeded gels in vitro and shortening of periosteum explants. In addition, remodeling under hypothetical conditions is explored to demonstrate how collagen might adapt to small differences in constraints. Typical aspects of all essentially different experimental conditions are captured quantitatively or qualitatively. Differences between predictions and experiments as well as new insights that emerge from the present simulations are discussed. This model is anticipated to evolve into a mechanistic description of collagen adaptation, which may assist in developing load-regimes for functional tissue engineered constructs, or may be employed to improve our understanding of the mechanisms behind physiological and pathological collagen remodeling.

The effects of cardiovascular disease on the clinical outcome of elderly patients with diffuse large B-cell lymphoma

We identified 3910 elderly (>65 yrs) patients with diffuse large B-cell lymphoma (DLBCL) who received doxorubicin-based (+/-rituximab) therapy and 77 347 cancer-free controls, and assessed cardiovascular events and survival in relation to preexisting cardiovascular comorbidities. Compared to controls, patients with DLBCL had a 3.4-fold (95%CI 3.0-3.9) and 2.5-fold (95%CI 2.3-2.7) increased risk of congestive heart failure (CHF)/cardiomyopathy (CM) within 6 months and 3 years of diagnosis, respectively. Risk of acute myocardial infarction (AMI) was similarly increased. The risk of CHF/CM and AMI was significantly higher in those patients with DLBCL (vs. controls) who did not report preexisting cardiovascular disease, compared to those who had preexisting cardiovascular disease; this was due to dose reductions of doxorubicin among patients with preexisting cardiovascular disease. Rituximab improved survival in patients with stage III-IV (but not I-II) disease (p-interaction = 0.0003). Our novel findings emphasize the need to reduce cardiac toxicity of doxorubicin in elderly DLBCL patients.

Should a native depth-dependent distribution of human meniscus constitutive components be considered in FEA-models of the knee joint?

The depth-dependent matrix composition of articular cartilage is important for its mechanical behavior. It is unknown whether the depth-dependent matrix composition of a meniscus is similarly important for its load-bearing function. The present objective was to determine whether it is necessary to account for the native distribution of matrix components in the cross-sectional plane of the meniscus, when studying its mechanical behavior in numerical models. To address this objective, measured depth-dependent distribution of matrix contents in the human meniscus, and fitted visco-elastic mechanical properties of the collagen were used as input in FEA simulations of a knee joint. The importance of including the depth-dependent matrix component constitution in the meniscus was determined by comparing simulations with an axisymmetric representation of the knee joint, which incorporated either the depth-dependent matrix composition or homogenized matrix. Depth-dependent differences in water, collagen and proteoglycan contents were observed, but these were not significantly different. The anterior region, with significantly higher collagen content, was statistically stiffer than the posterior region. However, depth wise, stiffness did not correlate to the constitution of the tissue. GAG content was significantly higher in the posterior than in the anterior region. Visco-elastic properties of meniscus collagen were fitted against tensile test data. Simulations show that the distribution of stresses and strains in the cartilage is slightly low when the meniscus contains a depth-dependent constitution, but this difference is only modest. Therefore, this study suggests that knee joint mechanics is rather insensitive to the distribution of constitutive components in the cross section of the meniscus, and that the depth-dependent matrix distribution of the meniscus is not essential to be included in axisymmetric computational models of the knee joint.

A numerical model to study mechanically induced initiation and progression of damage in articular cartilage

OBJECTIVE

Proteoglycan (PG) loss and surface roughening, early signs of osteoarthritis (OA), are likely preceded by softening of the ground substance and the collagen network. Insight in their relative importance to progression of OA may assist the development of treatment strategies for early OA. To support interpretation of experimental data, a numerical model is proposed that can predict damage progression in cartilage over time, as a consequence of excessive mechanical loading. The objective is to assess the interaction between ground substance softening and collagen fiber damage using this model.

DESIGN

An established cartilage mechanics model is extended with the assumption that excessive strains may damage the ground substance or the collagen network, resulting in softening of the overstrained constituent. During subsequent loading cycles the strain may or may not cross a threshold, resulting in damage to stabilize or to progress. To evaluate how softening of the ground substance and collagen may interact, damage progression is computed when either one of them, or both together are allowed to occur during stepwise increased loading.

RESULTS

Softening in the ground substance was predicted to localize in the superficial and transitional zone and resulted in cartilage softening. Collagen damage was most prominent in the superficial zone, with more diffuse damage penetrating deeper into the tissue, resulting in adverse strain gradients. Effects were more pronounced if both constituents developed damage in parallel.

CONCLUSION

Ground substance softening and collagen damage have distinct effects on cartilage mechanopathology, and damage in either one of them may promote each other.

Cladribine with immediate rituximab for the treatment of patients with variant hairy cell leukemia

PURPOSE

In contrast with the classic form, variant hairy cell leukemia (HCLv) responds poorly to single-agent purine analogs, expresses unmutated BRAF, has shorter overall survival, and lacks effective standard therapy. No treatment has achieved a high complete remission (CR) rate even in small series, and of 39 reported cases from six studies, overall response rate after cladribine was 44% with 8% CRs. Rituximab has been found to increase the sensitivity of malignant cells to cladribine, suggesting that combination with cladribine might improve response in HCLv. To test this hypothesis, patients with HCLv were treated with simultaneous cladribine and rituximab.

EXPERIMENTAL DESIGN

Patients with HCLv with 0 to 1 prior courses of cladribine received cladribine 0.15 mg/kg for days 1 to 5, with eight weekly doses of rituximab 375 mg/m(2) beginning day 1. Restaging was performed, and minimal residual disease (MRD) in blood and marrow was quantified using PCR, immunohistochemistry, and flow cytometry.

RESULTS

By 6 months, 9 (90%) of 10 patients achieved CR, compared with 3 (8%) of 39 reported cases treated with cladribine alone (P < 0.0001). Of the 9 CRs, 8 remain free of MRD at 12 to 48 (median 27) months of follow-up. No dose-limiting toxicities were observed when beginning cladribine and rituximab on the same day, although most patients required short-term steroids to prevent and treat rituximab infusion reactions. Cytopenias in CRs resolved in 7 to 211 (median 34) days without major infections.

CONCLUSION

Although cladribine alone lacks effectiveness for early or relapsed HCLv, cladribine with immediate rituximab achieves CRs without MRD and is feasible to administer.

Bendamustine and rituximab in relapsed and refractory hairy cell leukemia

PURPOSE

To determine tolerability and for the first time explore efficacy of bendamustine-rituximab (BR) in multiply relapsed/refractory hairy cell leukemia (HCL), using two different dose levels of bendamustine.

EXPERIMENTAL DESIGN

Patients with HCL with ≥2 prior therapies requiring treatment received rituximab 375 mg/m(2) days 1 and 15 plus bendamustine 70 (n = 6) or 90 (n = 6) mg/m(2), days 1 and 2, for six cycles at 4-week intervals.

RESULTS

At 70 and 90 mg/m(2)/dose of bendamustine, overall response rate was 100%, with three (50%) and four (67%) complete remissions (CR) in each respective group. Minimal residual disease (MRD) was absent in 67% and 100% of CRs, respectively. All six without MRD remain in CR at 30 to 35 (median, 31) months of follow-up. Soluble CD22 and CD25 levels decreased with all responses, with median values decreasing from 17.7 and 42 ng/mL at baseline to undetectable and 2 ng/mL after CR, respectively (P < 0.001). Of 12 patients receiving 72 cycles of BR, the most common toxicities were hematologic, including thrombocytopenia (83%), lymphopenia (75%), leukopenia (58%), and neutropenia (42%). Grade III and IV hematologic toxicity included lymphopenia and thrombocytopenia (each 75%), leukopenia (58%), and neutropenia (25%). No significant dose-related differences were detected in response or toxicity.

CONCLUSION

BR has significant activity in HCL. Bendamustine at either 70 or 90 mg/m(2)/dose was highly effective in multiply relapsed/refractory HCL and could be considered for achieving durable CRs without MRD in patients after failure of standard therapies. As it was not dose-limiting, 90 mg/m(2)/dose was chosen for future testing.

Intervertebral disc creep behavior assessment through an open source finite element solver

Degenerative Disc Disease (DDD) is one of the largest health problems faced worldwide, based on lost working time and associated costs. By means of this motivation, this work aims to evaluate a biomimetic Finite Element (FE) model of the Intervertebral Disc (IVD). Recent studies have emphasized the importance of an accurate biomechanical modeling of the IVD, as it is a highly complex multiphasic medium. Poroelastic models of the disc are mostly implemented in commercial finite element packages with limited access to the algorithms. Therefore, a novel poroelastic formulation implemented on a home-developed open source FE solver is briefly addressed throughout this paper. The combination of this formulation with biphasic osmotic swelling behavior is also taken into account. Numerical simulations were devoted to the analysis of the non-degenerated human lumbar IVD time-dependent behavior. The results of the tests performed for creep assessment were inside the scope of the experimental data, with a remarkable improvement of the numerical accuracy when compared with previously published results obtained with ABAQUS(®). In brief, this in-development open-source FE solver was validated with literature experimental data and aims to be a valuable tool to study the IVD biomechanics and DDD mechanisms.

Abstract 64: Interleukin-10 Decreases HDL: A Novel Cause of Disappearing HDL Syndrome

Introduction

“Disappearing HDL Syndrome” refers to cases of acquired severe HDL deficiency in non-critically ill patients. Except for rare idiosyncratic drug reactions, the physiological basis of Disappearing HDL Syndrome is not understood.

Hypothesis

“Disappearing HDL” in patients with B-cell disorders may be due to increased levels of cytokines, particularly IL-10, in plasma.

Methods

We investigated cytokine levels in a patient with intravascular large B-cell lymphoma (IVLBCL) who presented with undetectable or very low HDL-C, low LDL-C and markedly elevated triglycerides. IL-10 levels were investigated in additional patients with B-cell disorders (IVLBCL, large B-cell lymphoma, and ALPS) who presented with similar lipid profiles. A direct causal role for IL-10 in modulating HDL-C was investigated with a randomized, placebo-controlled study of recombinant IL-10 infusion into psoriatic arthritis patients.

Results

All cases (IVLBCL, large B-cell lymphoma and ALPS) had highly elevated serum IL-10 levels that normalized after chemotherapy concomitant with normalization of HDL-C, LDL-C and TG. In a survey of 93 ALPS patients, IL-10 showed a strong inverse correlation with HDL-C (R 2 = 0.3720, p<0.0001). In a randomized, placebo-controlled study of recombinant IL-10 infusion into psoriatic arthritis patients HDL-C precipitously decreased to near-undetectable levels shortly after IL-10 injection. Furthermore, IL-10 treatment also decreased LDL-C by 51% or more during IL-10 administration (p < 0.005) and increased TG by up to 2-fold.

Conclusions

Our study has identified increased IL10 as a potential cause of Disappearing HDL Syndrome and demonstrated that in addition to HDL-C, IL-10 can also modulated levels of LDL-C and TG, thus identifying a new link between inflammation and lipid metabolism.

Molecular subsets of mantle cell lymphoma defined by the IGHV mutational status and SOX11 expression have distinct biologic and clinical features

Mantle cell lymphoma (MCL) is a heterogeneous disease with most patients following an aggressive clinical course, whereas others having an indolent behavior. We conducted an integrative and multidisciplinary analysis of 177 MCL to determine whether the immunogenetic features of the clonotypic B-cell receptors (BcR) may identify different subsets of tumors. Truly unmutated (100% identity) IGHV genes were found in 24% cases, 40% were minimally/borderline mutated (99.9%-97%), 19% significantly mutated (96.9%-95%), and 17% hypermutated (<95%). Tumors with high or low mutational load used different IGHV genes, and their gene expression profiles were also different for several gene pathways. A gene set enrichment analysis showed that MCL with high and low IGHV mutations were enriched in memory and naive B-cell signatures, respectively. Furthermore, the highly mutated tumors had less genomic complexity, were preferentially SOX11-negative, and showed more frequent nonnodal disease. The best cut-off of germline identity of IGHV genes to predict survival was 97%. Patients with high and low mutational load had significant different outcome with 5-year overall survival (OS) of 59% and 40%, respectively (P = 0.004). Nodal presentation and SOX11 expression also predicted for poor OS. In a multivariate analysis, IGHV gene status and SOX11 expression were independent risk factors. In conclusion, these observations suggest the idea that MCL with mutated IGHV, SOX11-negativity, and nonnodal presentation correspond to a subtype of the disease with more indolent behavior.

Burkitt lymphoma pathogenesis and therapeutic targets from structural and functional genomics

Burkitt's lymphoma (BL) can often be cured by intensive chemotherapy, but the toxicity of such therapy precludes its use in the elderly and in patients with endemic BL in developing countries, necessitating new strategies. The normal germinal centre B cell is the presumed cell of origin for both BL and diffuse large B-cell lymphoma (DLBCL), yet gene expression analysis suggests that these malignancies may use different oncogenic pathways. BL is subdivided into a sporadic subtype that is diagnosed in developed countries, the Epstein-Barr-virus-associated endemic subtype, and an HIV-associated subtype, but it is unclear whether these subtypes use similar or divergent oncogenic mechanisms. Here we used high-throughput RNA sequencing and RNA interference screening to discover essential regulatory pathways in BL that cooperate with MYC, the defining oncogene of this cancer. In 70% of sporadic BL cases, mutations affecting the transcription factor TCF3 (E2A) or its negative regulator ID3 fostered TCF3 dependency. TCF3 activated the pro-survival phosphatidylinositol-3-OH kinase pathway in BL, in part by augmenting tonic B-cell receptor signalling. In 38% of sporadic BL cases, oncogenic CCND3 mutations produced highly stable cyclin D3 isoforms that drive cell cycle progression. These findings suggest opportunities to improve therapy for patients with BL.

Synergistic effects of nelfinavir and bortezomib on proteotoxic death of NSCLC and multiple myeloma cells

Exploiting protein homeostasis is a new therapeutic approach in cancer. Nelfinavir (NFV) is an HIV protease inhibitor that induces endoplasmic reticulum (ER) stress in cancer cells. Under conditions of ER stress, misfolded proteins are transported from the ER back to the cytosol for subsequent degradation by the ubiquitin–proteasome system. Bortezomib (BZ) is a proteasome inhibitor and interferes with degradation of misfolded proteins. Here, we show that NFV and BZ enhance proteotoxicity in non-small cell lung cancer (NSCLC) and multiple myeloma (MM) cells. The combination synergistically inhibited cell proliferation and induced cell death. Activating transcription factor (ATF)3 and CCAAT-enhancer binding protein homologous protein (CHOP), markers of ER stress, were rapidly increased, and their siRNA-mediated knockdown inhibited cell death. Knockdown of double-stranded RNA activated protein kinase-like ER kinase, a signal transducer in ER stress, significantly decreased apoptosis. Pretreatment with the protein synthesis inhibitor, cycloheximide, decreased levels of ubiquitinated proteins, ATF3, CHOP, and the overall total cell death, suggesting that inhibition of protein synthesis increases cell survival by relieving proteotoxic stress. The NFV/BZ combination inhibited the growth of NSCLC xenografts, which correlated with the induction of markers of ER stress and apoptosis. Collectively, these data show that NFV and BZ enhance proteotoxicity in NSCLC and MM cells, and suggest that this combination could tip the precarious balance of protein homeostasis in cancer cells for therapeutic gain.

Activation of CD44, a receptor for extracellular matrix components, protects chronic lymphocytic leukemia cells from spontaneous and drug induced apoptosis through MCL-1

Survival of chronic lymphocytic leukemia (CLL) cells in vivo is supported by the tissue microenvironment, which includes components of the extracellular matrix. Interactions between tumor cells and the extracellular matrix are in part mediated by CD44, whose principal ligand is hyaluronic acid. Here, we show that CD44 is more highly expressed on CLL cells of the clinically more progressive immunglobulin heavy chain variable gene (IGHV)-unmutated subtype than on cells of the IGHV-mutated type. Engagement of CD44 activated the phosphatidylinositol 3-kinase (PI3K)/AKT and mitogen activated protein kinase (MAPK)/ERK pathways and increased myeloid cell leukemia sequence 1 (MCL-1) protein expression. Consistent with the induction of these anti-apoptotic mechanisms, CD44 protected CLL cells from spontaneous and fludarabine-induced apoptosis. Obatoclax, an antagonist of MCL-1, blocked the pro-survival effect of CD44. In addition, obatoclax synergized with fludarabine to induce apoptosis of CLL cells. In conclusion, components of the extracellular matrix may provide survival signals to CLL cells through engagement of CD44. Inhibition of MCL-1 is a promising strategy to reduce the anti-apoptotic effect of the microenvironment on CLL cells.

Epizootic heamorragic disease

Epizootic haemorrhagic disease (EHD) is an infectious non-contagious viral disease transmitted by insects of the genus Culicoides which affects wild and domestic ruminants. The causative agent, the epizootic haemorrhagic disease virus (EHDV), belongs to the family Reoviridae, genus Orbivirus and shares many morphological and structural characteristics with the other members of the genus such as bluetongue, African horse sickness and equine encephalosis viruses. In recent years EHD outbreaks have been reported in countries bordering the European Union. They caused disease in cattle and severe repercussion on the livestock industry of the affected countries. In the light of recent European bluetongue epizootic these events pose an increasing threat to the European Union. This review includes the most recent information regarding the virus and the disease as well as tools for its diagnosis and control. It is our conviction that more attention should be drawn to both EHDV and the disease itself in order to fulfil all these gaps and not to be unprepared in case future possible incursions.