Building block aspect ratio controls assembly, architecture, and mechanics of synthetic and natural protein networks.

Fibrous networks constructed from high aspect ratio protein building blocks are ubiquitous in nature. Despite this ubiquity, the functional advantage of such building blocks over globular proteins is not understood. To answer this question, we engineered hydrogel network building blocks with varying numbers of protein L domains to control the aspect ratio. The mechanical and structural properties of photochemically crosslinked protein L networks were then characterised using shear rheology and small angle neutron scattering. We show that aspect ratio is a crucial property that defines network architecture and mechanics, by shifting the formation from translationally diffusion dominated to rotationally diffusion dominated. Additionally, we demonstrate that a similar transition is observed in the model living system: fibrin blood clot networks. The functional advantages of this transition are increased mechanical strength and the rapid assembly of homogenous networks above a critical protein concentration, crucial for in vivo biological processes such as blood clotting. In addition, manipulating aspect ratio also provides a parameter in the design of future bio-mimetic and bio-inspired materials.

Modelling network formation in folded protein hydrogels by cluster aggregation kinetics.

Globular folded protein-based hydrogels are becoming increasingly attractive due to their specific biological functionality, as well as their responsiveness to stimuli. By modelling folded proteins as colloids, there are rich opportunities to explore network formation mechanisms in protein hydrogels that negate the need for computationally expensive simulations which capture the full complexity of proteins. Here we present a kinetic lattice-based model which simulates the formation of irreversibly chemically crosslinked, folded protein-based hydrogels. We identify the critical point of gel percolation, explore the range of network regimes covering diffusion-limited to reaction-limited cluster aggregation (DLCA and RLCA, respectively) network formation mechanisms and predict the final network structure, fractal dimensions and final gel porosity. We reveal a crossover between DLCA and RLCA mechanisms as a function of protein volume fraction and show how the final network structure is governed by the structure at the percolation point, regardless of the broad variation of non-percolating cluster masses observed across all systems. An analysis of the pore size distribution in the final network structures reveals that, approaching RLCA, gels have larger maximal pores than the DLCA counterparts for both volume fractions studied. This general kinetic model and the analysis tools generate predictions of network structure and concurrent porosity over a broad range of experimentally controllable parameters that are consistent with current expectations and understanding of experimental results.

Viscoelastic Scaling Regimes for Marginally Rigid Fractal Spring Networks.

A family of marginally rigid (isostatic) spring networks with fractal structure up to a controllable length was devised, and the viscoelastic spectra G^{*}(ω) calculated. Two nontrivial scaling regimes were observed, (i) G^{'}≈G^{''}∝ω^{Δ} at low frequencies, consistent with Δ=1/2, and (ii) G^{'}∝G^{''}∝ω^{Δ^{'}} for intermediate frequencies corresponding to fractal structure, consistent with a theoretical prediction Δ^{'}=(ln3-ln2)/(ln3+ln2). The crossover between these two regimes occurred at lower frequencies for larger fractals in a manner suggesting diffusivelike dispersion. Solid gels generated by introducing internal stresses exhibited similar behavior above a low-frequency cutoff, indicating the relevance of these findings to real-world applications.

NCCN Guidelines® Insights: Myelodysplastic Syndromes, Version 3.2022.

The NCCN Guidelines for Myelodysplastic Syndromes (MDS) provide recommendations for the evaluation, diagnosis, and management of patients with MDS based on a review of clinical evidence that has led to important advances in treatment or has yielded new information on biologic factors that may have prognostic significance in MDS. The multidisciplinary panel of MDS experts meets on an annual basis to update the recommendations. These NCCN Guidelines Insights focus on some of the updates for the 2022 version of the NCCN Guidelines, which include treatment recommendations both for lower-risk and higher-risk MDS, emerging therapies, supportive care recommendations, and genetic familial high-risk assessment for hereditary myeloid malignancy predisposition syndromes.

Reaction Rate Governs the Viscoelasticity and Nanostructure of Folded Protein Hydrogels.

Hydrogels constructed from folded protein domains are of increasing interest as resilient and responsive biomaterials, but their optimization for applications requires time-consuming and costly molecular design. Here, we explore a complementary approach to control their properties by examining the influence of crosslinking rate on the structure and viscoelastic response of a model hydrogel constructed from photochemically crosslinked bovine serum albumin (BSA). Gelation is observed to follow a heterogeneous nucleation pathway in which BSA monomers crosslink into compact nuclei that grow into fractal percolated networks. Both the viscoelastic response probed by shear rheology and the nanostructure probed by small-angle X-ray scattering (SAXS) are shown to depend on the photochemical crosslinking reaction rate, with increased reaction rates corresponding to higher viscoelastic moduli, lower fractal dimension, and higher fractal cluster size. Reaction rate-dependent changes are shown to be consistent with a transition between diffusion- and rate-limited assembly, and the corresponding changes to viscoelastic response are proposed to arise from the presence of nonfractal depletion regions, as confirmed by SAXS. This controllable nanostructure and viscoelasticity constitute a potential route for the precise control of hydrogel properties, without the need for molecular modification.

Pathologic Features of Down Syndrome Myelodysplastic Syndrome and Acute Myeloid Leukemia: A Report From the Children's Oncology Group Protocol AAML0431.

CONTEXT.­: Detailed diagnostic features of acute myeloid leukemia in Down syndrome are lacking, leading to potential misdiagnoses as standard acute myeloid leukemia occurring in patients with Down syndrome. OBJECTIVE.­: To evaluate diagnostic features of acute myeloid leukemia and myelodysplastic syndrome in patients with Down syndrome. DESIGN.­: Diagnostic bone marrow samples from 163 patients enrolled in the Children's Oncology Group study AAML0431 were evaluated by using central morphologic review and institutional immunophenotyping. Results were compared to overall survival, event-free survival, GATA1 mutation status, cytogenetics, and minimal residual disease results. RESULTS.­: Sixty myelodysplastic syndrome and 103 acute myeloid leukemia samples were reviewed. Both had distinctive features compared to those of patients without Down syndrome. They showed megakaryocytic and erythroid but little myeloid dysplasia, and marked megakaryocytic hyperplasia with unusual megakaryocyte morphology. In acute myeloid leukemia cases, megakaryoblastic differentiation of blasts was most common (54 of 103, 52%); other cases showed erythroblastic (11 of 103, 11%), mixed erythroid/megakaryoblastic (20 of 103, 19%), or no differentiation (10 of 103, 10%). Myelodysplastic syndrome and acute myeloid leukemia cases had similar event-free survival and overall survival. Leukemic subgroups showed interesting, but not statistically significant, trends for survival and minimal residual disease. Cases with institutional diagnoses of French American British M1-5 morphology showed typical features of Down syndrome disease, with survival approaching that of other cases. CONCLUSIONS.­: Myelodysplastic syndrome and acute myeloid leukemia in Down syndrome display features that allow discrimination from standard cases of disease. These distinctions are important for treatment decisions, and for understanding disease pathogenesis. We propose specific diagnostic criteria for Down syndrome-related subtypes of acute myeloid leukemia and myelodysplastic syndrome.

Nonaffinity and Fluid-Coupled Viscoelastic Plateau for Immersed Fiber Networks.

We employ a matrix-based solver for the linear rheology of fluid-immersed disordered spring networks to reveal four distinct dynamic response regimes. One regime-completely absent in the known vacuum response-exhibits coupled fluid flow and network deformation, with both components responding nonaffinely. This regime contains an additional plateau (peak) in the frequency-dependent storage (loss) modulus-features that vanish without full hydrodynamic interactions. The mechanical response of immersed networks such as biopolymers and hydrogels is thus richer than previously established and offers additional modalities for design and control through fluid interactions.

The hierarchical emergence of worm-like chain behaviour from globular domain polymer chains.

Biological organisms make use of hierarchically organised structures to modulate mechanical behaviour across multiple lengthscales, allowing microscopic objects to generate macroscopic effects. Within these structural hierarchies, the resultant physical behaviour of the entire system is determined not only by the intrinsic mechanical properties of constituent subunits, but also by their organisation in three-dimensional space. When these subunits are polyproteins, colloidal chains or other globular domain polymers, the Kratky-Porod model is often assumed for the individual subunits. Hence, it is implicitly asserted that the polymeric object has an intrinsic parameter, the persistence length, that defines its flexibility. However, the persistence lengths extracted from experiment vary, and are often relatively small. Through a series of simulations on polymer chains formed of globular subunits, we show that the persistence length itself is a hierarchical structural property, related not only to the intrinsic mechanical properties of the underlying monomeric subunits, but emerging due to the organisation of inhomogenous geometry along the polymer contour.

Genotypic and clinical heterogeneity within NCCN favorable-risk acute myeloid leukemia.

The National Comprehensive Cancer Network (NCCN) defines the following types of acute myeloid leukemia (AML) as favorable-risk: acute promyelocytic leukemia with t(15;17) (APL); AML with core-binding factor (CBF) rearrangements, including t(8;21) and inv(16) or t(16;16) without mutations in KIT (CBF-KITwt); and AML with normal cytogenetics and mutations in NPM1 (NPM1mut); or biallelic mutations in CEBPA (CEBPAmut/mut), without FLT3-ITD. Although these AMLs are categorized as favorable risk by NCCN, clinical experience suggests that there are differences in clinical outcome amongst these cytogenetically and molecularly distinct leukemias. This study compared clinical and genotypic characteristics of 60 patients with favorable-risk AML, excluding APL, and demonstrated significant differences between them. Patients with NPM1mut AML were significantly older than those in the other groups. Targeted next-generation sequencing on DNA from peripheral blood or bone marrow revealed significantly more mutations in NPM1mut AML than the other favorable-risk diseases, especially in genes related to DNA splicing and methylation. CEBPAmut/mut AMLs exhibited more mutations in transcription-related genes. Patients with NPM1mut AML and CEBPAmut/mut AML show significantly reduced overall survival in comparison with CBF-KITwt AML. These findings emphasize that favorable-risk AML patients have divergent outcomes and that differences in clinical and genotypic characteristics should be considered in their evaluation and management.

Acute autoimmune hemolytic anemia due to anti-Ena autoantibody successfully treated with rituximab.

BACKGROUND: Autoimmune hemolytic anemia (AIHA) due to anti-Ena has been previously reported in association with massive intravascular hemolysis, disseminated intravascular coagulation, and fatal outcomes. Here we report a case of successfully treated AIHA due to anti-Ena . CASE REPORT: A 69-year-old male with a past medical history of cirrhosis due to nonalcoholic steatohepatitis status post-orthotopic liver transplant presented with 1-month history of progressive anemia. At presentation, his hemoglobin (Hb) was 5.6 g/dL, hematocrit (Hct) 16%, reticulocytes 0.3%, direct bilirubin (bili) 4 g/dL, lactate dehydrogenase 533 units/L (reference, 125-220 units/L), and haptoglobin 254 mg/dL (reference, 40-273 mg/dL). Blood bank testing revealed an autoantibody present in his plasma and a direct antiglobulin test positive for immunoglobulin G (IgC) but negative for complement. He received 1 unit of an incompatible blood group O phenotypically matched red blood cell unit. RESULTS: Over the course of the next 5 days, the Hb and Hct decreased to 4.1 g/dL and 12%, respectively, direct bili increased to 12.3 mg/day, reticulocytes slightly increased to 0.9%, and haptoglobin decreased to less than 8 mg/dL. Marrow study showed a hypercellular marrow with erythroid hyperplasia. Additional workup performed at a reference laboratory identified an anti-Ena autoantibody. He received prednisone and weekly rituximab infusions and was monitored weekly. At the 2-month visit, Hb and Hct were 10 g/dL and 32%, respectively. CONCLUSION: Unlike two of the previously reported fatal cases of AIHA with anti-Ena specificity, this 69-year-old male treated with weekly rituximab infusion underwent clinical recovery and significant anemia improvement.

In silico modelling to differentiate the contribution of sugar frequency versus total amount in driving biofilm dysbiosis in dental caries.

Dental caries is the most prevalent infection globally and a substantial economic burden in developed countries. Dietary sugars are the main risk factor, and drive increased proportions of acid-producing and acid-tolerating (aciduric) bacterial species within dental biofilms. Recent longitudinal studies have suggested that caries is most strongly correlated with total sugar intake, contrasting with the prevailing view that intake frequency is the primary determinant. To explore this possibility, we employed a computational model for supragingival plaque to systematically sample combinations of sugar frequency and total amount, allowing their independent contributions on the ratio of aciduric (i.e. cariogenic) to non-aciduric bacteria to be unambiguously determined. Sugar frequency was found to be irrelevant for either very high or very low daily total amounts as the simulated biofilm was predicted to be always or never cariogenic, respectively. Frequency was a determining factor for intermediate total amounts of sugar, including the estimated average human consumption. An increased risk of caries (i.e. high prevalence of aciduric/non-aciduric species) was predicted for high intake frequencies. Thus, both total amount and frequency of sugar intake may combine to influence plaque cariogenicity. These findings could be employed to support public guidance for dietary change, leading to improved oral healthcare.

Improved outcomes for myeloid leukemia of Down syndrome: a report from the Children's Oncology Group AAML0431 trial.

Patients with myeloid leukemia of Down syndrome (ML-DS) have favorable event-free survival (EFS), but experience significant treatment-related morbidity and mortality. ML-DS blast cells ex vivo have increased sensitivity to cytarabine (araC) and daunorubicin, suggesting that optimizing drug dosing may improve outcomes while reducing toxicity. The Children's Oncology Group (COG) AAML0431 trial consisted of 4 cycles of induction and 2 cycles of intensification therapy based on the treatment schema of the previous COG A2971 trial with several modifications. High-dose araC (HD-araC) was used in the second induction cycle instead of the intensification cycle, and 1 of 4 daunorubicin-containing induction cycles was eliminated. For 204 eligible patients, 5-year EFS was 89.9% and overall survival (OS) was 93.0%. The 5-year OS for 17 patients with refractory/relapsed leukemia was 34.3%. We determined the clinical significance of minimal residual disease (MRD) levels as measured by flow cytometry on day 28 of induction I. MRD measurements, available for 146 of the 204 patients, were highly predictive of treatment outcome; 5-year disease-free survival for MRD-negative patients (n = 125) was 92.7% vs 76.2% for MRD-positive patients (n = 21) (log-rank P = .011). Our results indicated that earlier use of HD-araC led to better EFS and OS in AAML0431 than in past COG studies. A 25% reduction in the cumulative daunorubicin dose did not impact outcome. MRD, identified as a new prognostic factor for ML-DS patients, can be used for risk stratification in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00369317.

Myelodysplastic Syndromes, Version 2.2017, NCCN Clinical Practice Guidelines in Oncology.

The myelodysplastic syndromes (MDS) comprise a heterogenous group of myeloid disorders with a highly variable disease course. Diagnostic criteria to better stratify patients with MDS continue to evolve, based on morphology, cytogenetics, and the presence of cytopenias. More accurate classification of patients will allow for better treatment guidance. Treatment encompasses supportive care, treatment of anemia, low-intensity therapy, and high-intensity therapy. This portion of the guidelines focuses on diagnostic classification, molecular abnormalities, therapeutic options, and recommended treatment approaches.

Data-Driven Iterative Refinement of Bone Marrow Testing Protocols Leads to Progressive Improvement in Cytogenetic and Molecular Test Utilization.

OBJECTIVES: To determine the effect of iterative refinement of standard ordering protocols on test utilization and results for bone marrow biopsy specimens. METHODS: Eighteen months of test utilization and result data were used to revise the protocols that determine cytogenetic and molecular test selection on bone marrow specimens and then compared with data obtained following protocol revision. RESULTS: Revision of protocols resulted in reduction in total tests and associated charges, due to a decrease in tests both concordant and discordant with the protocols. These reductions only occurred in diseases for which revisions were made and were limited to cases in which reflex testing was performed. There was an increase in the fraction of positive tests, which was also limited to reflex testing. CONCLUSIONS: Data-driven iterative revision of protocols further improves test utilization and performance, while reducing cost. Analysis of testing data can be used to continuously improve test ordering decisions.

Biomechanical Analysis of Infectious Biofilms.

The removal of infectious biofilms from tissues or implanted devices and their transmission through fluid transport systems depends in part of the mechanical properties of their polymeric matrix. Linking the various physical and chemical microscopic interactions to macroscopic deformation and failure modes promises to unveil design principles for novel therapeutic strategies targeting biofilm eradication, and provide a predictive capability to accelerate the development of devices, water lines, etc, that minimise microbial dispersal. Here, our current understanding of biofilm mechanics is appraised from the perspective of biophysics , with an emphasis on constitutive modelling that has been highly successful in soft matter. Fitting rheometric data to viscoelastic models has quantified linear and nonlinear stress relaxation mechanisms, how they vary between species and environments, and how candidate chemical treatments alter the mechanical response. The rich interplay between growth, mechanics and hydrodynamics is just becoming amenable to computational modelling and promises to provide unprecedented characterisation of infectious biofilms in their native state.

In Silico Modeling of the Rheological Properties of Covalently Cross-Linked Collagen Triple Helices.

Biomimetic hydrogels based on natural polymers are a promising class of biomaterial, mimicking the natural extra-cellular matrix of biological tissues and providing cues for cell attachment, proliferation, and differentiation. With a view to providing an upstream method to guide subsequent experimental design, the aim of this study was to introduce a mathematical model that described the rheological properties of a hydrogel system based on covalently cross-linked collagen triple helices. In light of their organization, such gels exhibit limited collagen bundling that cannot be described by existing fibril network models. The model presented here treats collagen triple helices as discrete semiflexible polymers, permits full access to metrics for network microstructure, and should provide a comprehensive understanding of the parameter space associated with the development of such multifunctional materials. Triple helical hydrogel networks were experimentally obtained via the reaction of type I collagen with both aromatic and aliphatic diacids. The complex modulus G* was found from rheological testing in linear shear and quantitatively compared to model predictions. In silico data from the computational model successfully described the experimental trends in hydrogel storage modulus with either (i) the concentration of collagen triple helices during the cross-linking reaction or (ii) the type of cross-linking segment introduced in resulting hydrogel networks. This approach may pave the way to a step change in the rational design of biomimetic triple helical collagen systems with controlled multifunctionality.

Ecological approaches to oral biofilms: control without killing.

Humans have co-evolved with micro-organisms and have a symbiotic or mutualistic relationship with their resident microbiome. As at other body surfaces, the mouth has a diverse microbiota that grows on oral surfaces as structurally and functionally organised biofilms. The oral microbiota is natural and provides important benefits to the host, including immunological priming, down-regulation of excessive pro-inflammatory responses, regulation of gastrointestinal and cardiovascular systems, and colonisation by exogenous microbes. On occasions, this symbiotic relationship breaks down, and previously minor components of the microbiota outcompete beneficial bacteria, thereby increasing the risk of disease. Antimicrobial agents have been formulated into many oral care products to augment mechanical plaque control. A delicate balance is needed, however, to control the oral microbiota at levels compatible with health, without killing beneficial bacteria and losing the key benefits delivered by these resident microbes. These antimicrobial agents may achieve this by virtue of their recommended twice daily topical use, which results in pharmacokinetic profiles indicating that they are retained in the mouth for relatively long periods at sublethal levels. At these concentrations they are still able to inhibit bacterial traits implicated in disease (e.g. sugar transport/acid production; protease activity) and retard growth without eliminating beneficial species. In silico modelling studies have been performed which support the concept that either reducing the frequency of acid challenge and/or the terminal pH, or by merely slowing bacterial growth, results in maintaining a community of beneficial bacteria under conditions that might otherwise lead to disease (control without killing).

Myelodysplastic syndromes, version 2.2015.

The NCCN Guidelines for Myelodysplastic Syndromes (MDS) comprise a heterogeneous group of myeloid disorders with a highly variable disease course that depends largely on risk factors. Risk evaluation is therefore a critical component of decision-making in the treatment of MDS. The development of newer treatments and the refinement of current treatment modalities are designed to improve patient outcomes and reduce side effects. These NCCN Guidelines Insights focus on the recent updates to the guidelines, which include the incorporation of a revised prognostic scoring system, addition of molecular abnormalities associated with MDS, and refinement of treatment options involving a discussion of cost of care.

Prospects of oral disease control in the future - an opinion.

The mouth supports a diverse microbiota which provides major benefits to the host. On occasions, this symbiotic relationship breaks down (dysbiosis), and disease can be a consequence. We argue that progress in the control of oral diseases will depend on a paradigm shift away from approaches that have proved successful in medicine for many diseases with a specific microbial aetiology. Factors that drive dysbiosis in the mouth should be identified and, where possible, negated, reduced or removed, while antimicrobial agents delivered by oral care products may function effectively, even at sub-lethal concentrations, by modulating the activity and growth of potentially pathogenic bacteria. In this way, the beneficial activities of the resident oral microbiota will be retained and the risk of dysbiosis occurring will be reduced.