Altered Biomechanical Properties Research Articles

Structure-function of cartilage in osteoarthritis: An ex-vivo correlation analysis between its structural, viscoelastic and frictional properties

Healthy articular cartilage is characterized by extremely low friction and high compressive stiffness. This dual-functionality is tailored by its biphasic structure, whereby a fluid phase interacts with the extracellular matrix. Osteoarthritis (OA) causes structural changes, thereby altering the biomechanical and frictional properties. How the structural and functional properties of human cartilage are associated with OA remain unknown. To address this, we identified relationships between structural parameters, viscoelastic and frictional properties of degenerated human cartilage through correlation analyses. We found that cartilage friction was mainly influenced by its microscopic structure, while the viscoelastic properties were also related to the macroscopic structure. The viscoelastic and frictional properties displayed a weak correlation. These findings provide insights into the interplay between cartilage structure and its functional properties in OA, which might provide a basis for advancements in diagnosing and treating degenerated human cartilage. Statement of significanceOsteoarthritis causes changes in the cartilages biphasic structure, thereby affecting functionality by altered biomechanical and frictional properties. Currently a cartilage-preserving therapeutic option remains lacking, because the disease is not fully understood. In our correlation analyses, we investigated relationships between the structural, the viscoelastic and frictional properties of degenerated human cartilage. We found that cartilage friction was particularly dependent on the microscopic structure, while the viscoelastic properties also correlated with the macroscopic structure. The frictional properties displayed only a weak dependency with the viscoelastic properties. These new insights into the structure-function and inter-functional relationships may provide new options to advance the diagnosis and treatment of degenerated cartilage.

T1ρ relaxation mapping in osteochondral lesions of the talus: a non-invasive biomarker for altered biomechanical properties of hyaline cartilage?

BackgroundTo evaluate T1ρ relaxation mapping in patients with symptomatic talar osteochondral lesions (OLT) and healthy controls (HC) at rest, with axial loading and traction.MethodsParticipants underwent 3-T ankle magnetic resonance imaging at rest and with 500 N loading and 120 N traction, without axial traction for a subcohort of 17/29 HC. We used a fast low-angle shot sequence with variable spin-lock intervals for monoexponential T1ρ fitting. Cartilage was manually segmented to extract T1ρ values.ResultsWe studied 29 OLT patients (age 31.7 ± 7.5 years, 15 females, body mass index [BMI] 25.0 ± 3.4 kg/m2) and 29 HC (age 25.2 ± 4.3 years, 17 females, BMI 22.5 ± 2.3 kg/m2. T1ρ values of OLT (50.4 ± 3.4 ms) were higher than those of intact cartilage regions of OLT patients (47.2 ± 3.4 ms; p = 0.003) and matched HC cartilage (48.1 ± 3.3 ms; p = 0.030). Axial loading and traction induced significant T1ρ changes in the intact cartilage regions of patients (loading, mean difference -1.1 ms; traction, mean difference 1.4 ms; p = 0.030 for both) and matched HC cartilage (-2.2 ms, p = 0.003; 2.3 ms, p = 0.030; respectively), but not in the OLT itself (-1.3 ms; p = 0.150; +1.9 ms; p = 0.150; respectively).ConclusionIncreased T1ρ values may serve as a biomarker of cartilage degeneration in OLT. The absence of load- and traction-induced T1ρ changes in OLT compared to intact cartilage suggests that T1ρ may reflect altered biomechanical properties of hyaline cartilage.Trial registrationDRKS, DRKS00024010. Registered 11 January 2021, https://drks.de/search/de/trial/DRKS00024010.Relevance statementT1ρ mapping has the potential to evaluate compositional and biomechanical properties of the talar cartilage and may improve therapeutic decision-making in patients with osteochondral lesions.Key PointsT1ρ values in osteochondral lesions increased compared to intact cartilage.Significant load- and traction-induced T1ρ changes were observed in visually intact regions and in healthy controls but not in osteochondral lesions.T1ρ may serve as an imaging biomarker for biomechanical properties of cartilage.Graphical

Birefringence-induced phase delay enables Brillouin mechanical imaging in turbid media

Acoustic vibrations of matter convey fundamental viscoelastic information that can be optically retrieved by hyperfine spectral analysis of the inelastic Brillouin scattered light. Increasing evidence of the central role of the viscoelastic properties in biological processes has stimulated the rise of non-contact Brillouin microscopy, yet this method faces challenges in turbid samples due to overwhelming elastic background light. Here, we introduce a common-path Birefringence-Induced Phase Delay (BIPD) filter to disentangle the polarization states of the Brillouin and Rayleigh signals, enabling the rejection of the background light using a polarizer. We demonstrate a 65 dB extinction ratio in a single optical pass collecting Brillouin spectra in extremely scattering environments and across highly reflective interfaces. We further employ the BIPD filter to image bone tissues from a mouse model of osteopetrosis, highlighting altered biomechanical properties compared to the healthy control. Results herald new opportunities in mechanobiology where turbid biological samples remain poorly characterized.

High-viscosity driven modulation of biomechanical properties of human mesenchymal stem cells promotes osteogenic lineage

Biomechanical cues could effectively govern cell gene expression to direct the differentiation of specific stem cell lineage. Recently, the medium viscosity has emerged as a significant mechanical stimulator that regulates the cellular mechanical properties and various physiological functions. However, whether the medium viscosity can regulate the mechanical properties of human mesenchymal stem cells (hMSCs) to effectively trigger osteogenic differentiation remains uncertain. The mechanism by which cells sense and respond to changes in medium viscosity, and regulate cell mechanical properties to promote osteogenic lineage, remains elusive. In this study, we demonstrated that hMSCs, cultured in a high-viscosity medium, exhibited larger cell spreading area and higher intracellular tension, correlated with elevated formation of actin stress fibers and focal adhesion maturation. Furthermore, these changes observed in hMSCs were associated with activation of TRPV4 (transient receptor potential vanilloid sub-type 4) channels on the cell membrane. This feedback loop among TRPV4 activation, cell spreading and intracellular tension results in calcium influx, which subsequently promotes the nuclear localization of NFATc1 (nuclear factor of activated T cells 1). Concomitantly, the elevated intracellular tension induced nuclear deformation and promoted the nuclear localization of YAP (YES‐associated protein). The concurrent activation of NFATc1 and YAP significantly enhanced alkaline phosphatase (ALP) for pre-osteogenic activity. Taken together, these findings provide a more comprehensive view of how viscosity-induced alterations in biomechanical properties of MSCs impact the expression of osteogenesis-related genes, and ultimately promote osteogenic lineage.

Modulatory interactions of T-2 and deoxynivalenol mycotoxins on murine femoral development and osteological integrity

In this study, we conducted a systematic assessment of the effectsof deoxynivalenol (DON) and T-2 mycotoxins (T-2) on the developmental processes and structural integrity of murine femurs, considering both the isolated and synergistic effects of these toxins. To this end, we divided 72 male mice into nine groups, each subjected to varying dosages of T-2, DON, or their combinations. Over a four-week experimental period, meticulous monitoring was undertaken regarding the mice's body weight, biochemical markers of bone formation and resorption, and the activity of relevant cells. To comprehensively evaluate alterations in bone structure, we employed biomechanical analysis, micro-computed tomography (micro-CT), and transmission electron microscopy.Our findings unveiled a significant revelation: the mice exhibited a dose-dependent decrease in body weight upon exposure to individual mycotoxins, while the combined use of these toxins manifested an atypical antagonistic effect. Furthermore, we observed variations in the levels of calcium, phosphorus, and vitamin D, as well as adjustments in the activities of osteoblasts and osteoclasts, all intricately linked to the dosage and ratio of the toxins. Alterations in biomechanical properties were also noted to correlate with the dosage and combination of toxins. Analyses via micro-CT and transmission electron microscopy further corroborated the substantial impact of toxin dosage and combinations on both cortical and trabecular bone structures.In summation, our research unequivocally demonstrates the dose- and ratio-dependent detrimental effects of DON and T-2 mycotoxins on the growth and structural integrity of murine femurs. These insights accentuate the importance of a profound understanding of the potential risks these toxins pose to bone health, offering pivotal guidance for future toxicological research and public health preventative strategies.

Advanced glycation end products promote meniscal calcification by activating the mTOR-ATF4 positive feedback loop

The meniscus is vital for maintaining knee homeostasis and function. Meniscal calcification is one of the earliest radiological indicators of knee osteoarthritis (KOA), and meniscal calcification is associated with alterations in biomechanical properties. Meniscal calcification originates from a biochemical process similar to vascular calcification. Advanced glycation end products (AGEs) and their receptors (RAGEs) reportedly play critical roles in vascular calcification. Herein, we investigated whether targeting AGE-RAGE is a potential treatment for meniscal calcification. In our study, we demonstrated that AGE-RAGE promotes the osteogenesis of meniscal cells and exacerbates meniscal calcification. Mechanistically, AGE-RAGE activates mTOR and simultaneously promotes ATF4 accumulation, thereby facilitating the ATF4-mTOR positive feedback loop that enhances the osteogenic capacity of meniscal cells. In this regard, mTOR inhibits ATF4 degradation by reducing its ubiquitination, while ATF4 activates mTOR by increasing arginine uptake. Our findings substantiate the unique role of AGE-RAGE in the meniscus and reveal the role of the ATF4-mTOR positive feedback loop during the osteogenesis of meniscal cells; these results provide potential therapeutic targets for KOA.

The relationship between cancer and biomechanics.

The onset, development, diagnosis, and treatment of cancer involve intricate interactions among various factors, spanning the realms of mechanics, physics, chemistry, and biology. Within our bodies, cells are subject to a variety of forces such as gravity, magnetism, tension, compression, shear stress, and biological static force/hydrostatic pressure. These forces are perceived by mechanoreceptors as mechanical signals, which are then transmitted to cells through a process known as mechanical transduction. During tumor development, invasion and metastasis, there are significant biomechanical influences on various aspects such as tumor angiogenesis, interactions between tumor cells and the extracellular matrix (ECM), interactions between tumor cells and other cells, and interactions between tumor cells and the circulatory system and vasculature. The tumor microenvironment comprises a complex interplay of cells, ECM and vasculature, with the ECM, comprising collagen, fibronectins, integrins, laminins and matrix metalloproteinases, acting as a critical mediator of mechanical properties and a key component within the mechanical signaling pathway. The vasculature exerts appropriate shear forces on tumor cells, enabling their escape from immune surveillance, facilitating their dissemination in the bloodstream, dictating the trajectory of circulating tumor cells (CTCs) and playing a pivotal role in regulating adhesion to the vessel wall. Tumor biomechanics plays a critical role in tumor progression and metastasis, as alterations in biomechanical properties throughout the malignant transformation process trigger a cascade of changes in cellular behavior and the tumor microenvironment, ultimately culminating in the malignant biological behavior of the tumor.

"Floppy brain" in congenital hydrocephalus.

Hydrocephalus is classically considered to be a disorder of altered cerebrospinal fluid (CSF) circulation, leading to the dilation of cerebral ventricles. Here, we report a clinical case of a patient who presented with fetal-onset hydrocephalus with diffusely reduced cortical and white matter volumes resulting from a genetic mutation in L1CAM, a well-known hydrocephalus disease gene involved in neuronal cell adhesion and axon development. After CSF was drained from the ventricle intraoperatively, the patient's cortical mantle collapsed and exhibited a "floppy" appearance on neuroimaging, suggesting an inability of the hydrocephalic brain to maintain its structural integrity. The case provides clinical support for altered brain biomechanical properties in human hydrocephalus and adds to the emerging hypothesis that altered brain development with secondary impact on brain structural stability may contribute to ventricular enlargement in some subsets of hydrocephalus.

Moisturizing at a molecular level - The basis of Corneocare.

This review covers the last 20 years of research we and our collaborators have conducted on ethnic differences in facial skin moisturization placed in historical context with previous research. We have focussed particularly on the biochemical and cellular gradients of the stratum corneum (SC) with the aim of discovering new skin moisturization and SC maturation mechanisms, identifying new technologies and/or providing conceptual innovations for ingredients that will improve our understanding and treatment of dry skin. Specifically, we discuss gradients for corneodesmosomes and proteases, corneocyte phenotype-inducing enzymes, filaggrin and natural moisturizing factor (NMF), and barrier lipids. These gradients are interdependent and influence greatly corneocyte maturation. The interrelationship between corneodesmolysis and the covalent attachment of ω-hydroxy ceramides and ω-hydroxy fatty acids to the corneocyte protein envelope forming the corneocyte lipid envelope is especially relevant in our new understanding of mechanisms leading to dry skin. This process is initiated by a linoleoyl-ω-acyl ceramide transforming enzyme cascade including 12R lipoxygenase (12R-LOX), epidermal lipoxygenase-3 (eLOX3), epoxide hydrolase 3 (EPHX3), short-chain dehydrogenase/reductase family 9C member 7 (SDR9C7), ceramidase and transglutaminase 1. Our research has opened the opportunity of using novel treatment systems for dry skin based on lipids, humectants, niacinamide and inhibitors of the plasminogen system. It is clear that skin moisturization is a more complex mechanism than simple skin hydration.

The Pyruvate Kinase Activator Mitapivat Improves Red Blood Cell Deformability and Sickling Kinetics in Adult Patients with Sickle Cell Disease

Background: A hallmark of sickle cell disease (SCD) is compromised red blood cell (RBC) deformability. Polymerization of hemoglobin S (HbS) underlies this "sickling" which results in altered biomechanical properties that impact rheology and hemodynamics (Barabino et al, 2010). There have been exciting clinical developments in anti-sickling therapies - including enhancement of red cell pyruvate kinase (PKR) modality. Importantly, deformability measurements of RBCs via ektacytometry are increasingly used to aid the assessment of their therapeutic efficacy. Here we employed the Laser assisted Optical Rotational Red Cell Analyzer (LORRCA, RR Mechatronics), which permits the evaluation of RBC deformability as a function of shear stress, osmotic pressure, and oxygen tension, to evaluate the changes in RBC deformability in subjects undergoing treatment with mitapivat (AG-348), a PKR activator under clinical development for sickle cell disease. We analyzed changes in deformability measurements of RBCs in HbSS subjects after 4 weeks and 12 weeks of mitapivat therapy and compared them to t50 - a single parameter measure of sickling kinetics (Dunkelberger et al, 2018). Methods: We studied subjects currently enrolled under IRB approved clinical trial NCT04610866 that evaluates the long-term safety and tolerability of mitapivat in SCD patients. Fifteen subjects (aged 25 - 57 years; 5 females, 10 males; African/African-American) were evaluated, though not all endpoints were available for every patient across all assays. Fresh whole blood (collected in EDTA tubes) was obtained at baseline (prior to drug initiation), after 4 weeks and after 12 weeks of therapy. Cells were counted and diluted in polyvinylpyrrolidone (PVP) solution before undergoing same-day LORRCA assays. The Elongation Index (EI) is a measure of the cells' ability to undergo deformation at different physiologically relevant conditions. EI was assessed at increasing shear stresses of .3 Pascals (Pa), .95 Pa, 3 Pa, 9.49 Pa, and 30 Pa (elongation assay). Parameters derived under continuous osmotic changes (0-600mOsm/kg - osmoscan) include O min which informs on RBC fragility, O Hyper which informs on hydration state and corresponds to 50% of the maximum deformability in the hypertonic region, EI max (osmo) which reveals maximum deformability and informs on RBC cytoskeletal mechanics, and O Max which gives the osmolality at which EI Max is achieved. Point of Sickling (POS) gives the oxygen tension at which the cells start to sickle during nitrogen facilitated deoxygenation of the sample (oxyscan). These parameters of deformability are generated by LORRCA software. For all assays, we analyzed the % change from baseline after 4 weeks and 12 weeks of therapy (Wilcoxon signed rank test, R v1.4.1106) and compared these changes to those in t50 (Spearman correlation test, Prism v9) (Figure 1). Results: Mitapivat therapy resulted in increased elongation indices across all shear stress levels, with significance reached at shears of .3 Pa, .95 Pa, and 3 Pa (respective mean % changes of 78.5, 181.8, and 23.0 (4 weeks) and 101.2, 212.9, and 30.1 (12 weeks)) suggesting improved deformability of RBCs. Likewise, significant increases in O hyper (mean % changes of 2.8 and 3.4) and osmo EI Max (mean % changes 7.9 and 9.5) respectively, indicate improvements in RBC hydration and cytoskeletal dynamics in response to changing osmotic pressures. Furthermore, a significant decrease in the average point of sickling was noted at both 4 weeks and 12 weeks (-20.15% and -16.8%, respectively), suggesting RBCs were susceptible to sickling at partial pressures of oxygen lower than those observed before therapy. Conclusion: Altogether, these findings indicate that mitapivat therapy results in improved ability of RBCs to withstand deformational changes in response to shear stress, osmotic pressure, and decreasing oxygen tension, likely via bolstered membrane integrity. Interestingly, when compared to t50 values, significant correlation was observed at all levels of shear stress and at the maximal deformability (EI max) achieved during both the osmoscan and oxyscan assays. Acknowledgement: This study is part of a Cooperative Research and Development Agreement (CRADA) with AGIOS Pharmaceuticals, Inc., Cambridge, MA, United States Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Changes in nanomechanical properties of single neuroblastoma cells as a model for oxygen and glucose deprivation (OGD)

Although complex, the biological processes underlying ischemic stroke are better known than those related to biomechanical alterations of single cells. Mechanisms of biomechanical changes and their relations to the molecular processes are crucial for understanding the function and dysfunction of the brain. In our study, we applied atomic force microscopy (AFM) to quantify the alterations in biomechanical properties in neuroblastoma SH-SY5Y cells subjected to oxygen and glucose deprivation (OGD) and reoxygenation (RO). Obtained results reveal several characteristics. Cell viability remained at the same level, regardless of the OGD and RO conditions, but, in parallel, the metabolic activity of cells decreased with OGD duration. 24 h RO did not recover the metabolic activity fully. Cells subjected to OGD appeared softer than control cells. Cell softening was strongly present in cells after 1 h of OGD and with longer OGD duration, and in RO conditions, cells recovered their mechanical properties. Changes in the nanomechanical properties of cells were attributed to the remodelling of actin filaments, which was related to cofilin-based regulation and impaired metabolic activity of cells. The presented study shows the importance of nanomechanics in research on ischemic-related pathological processes such as stroke.

Dysfunctional paraspinal muscles in adult spinal deformity patients lead to increased spinal loading.

PurposeDecreased spinal extensor muscle strength in adult spinal deformity (ASD) patients is well-known but poorly understood; thus, this study aimed to investigate the biomechanical and histopathological properties of paraspinal muscles from ASD patients and predict the effect of altered biomechanical properties on spine loading.Methods68 muscle biopsies were collected from nine ASD patients at L4–L5 (bilateral multifidus and longissimus sampled). The biopsies were tested for muscle fiber and fiber bundle biomechanical properties and histopathology. The small sample size (due to COVID-19) precluded formal statistical analysis, but the properties were compared to literature data. Changes in spinal loading due to the measured properties were predicted by a lumbar spine musculoskeletal model.ResultsSingle fiber passive elastic moduli were similar to literature values, but in contrast, the fiber bundle moduli exhibited a wide range beyond literature values, with 22% of 171 fiber bundles exhibiting very high elastic moduli, up to 20 times greater. Active contractile specific force was consistently less than literature, with notably 24% of samples exhibiting no contractile ability. Histological analysis of 28 biopsies revealed frequent fibro-fatty replacement with a range of muscle fiber abnormalities. Biomechanical modelling predicted that high muscle stiffness could increase the compressive loads in the spine by over 500%, particularly in flexed postures.DiscussionThe histopathological observations suggest diverse mechanisms of potential functional impairment. The large variations observed in muscle biomechanical properties can have a dramatic influence on spinal forces. These early findings highlight the potential key role of the paraspinal muscle in ASD.

Elastin integrity in bicuspid valve-associated aortopathy is associated with altered biomechanical properties and influenced by age.

BackgroundAortic wall remodelling in bicuspid aortic valve (BAV) patients is heterogeneous and characterized by elastin fiber breakdown alongside impaired biomechanics. However, the relationship between aortic histopathological changes and biomechanics are incompletely understood. We clarify the influence of elastin fiber integrity on ex vivo aortic wall mechanical properties in BAV patients, and explore the influence of patient age.MethodsAortic tissue samples (N=66) from 19 BAV patients undergoing prophylactic ascending aortic resection surgery were analyzed. Semi-quantitative histopathological analysis was conducted to assess elastin fiber integrity including elastin content and elastic fiber fragmentation. Ex vivo biaxial mechanical testing generated stress-strain curves from which physiological [low-strain tangential modulus (LTM), transition zone onset stress (TZo)] and supraphysiological [transition zone end stress (TZe) and high-strain tangential modulus (HTM)] mechanical properties were obtained. Relationships between histopathology and mechanical properties were determined using a linear mixed effect model. BAV patients were subdivided according to ‘younger’ and ‘older’ age groups (i.e., 51–60 and 61–70 years old, respectively).ResultsNo statistically significant differences in elastin content were observed between younger and older BAV patients. Older patients showed greater elastin fiber fragmentation compared to their younger cohort (74% versus 61%). Elastin fiber histopathology was associated with differences in physiological mechanical properties: elastin fragmentation corresponded with lower LTM (P=0.005) and TZo (P=0.044) in younger BAV patients and higher LTM (P=0.049) and TZo (P=0.001) in older BAV patients. Histopathology changes were significantly associated with supraphysiological mechanical properties only in older BAV patients: decreased elastin integrity was associated with increased TZe (P=0.049) and HTM (P<0.001).ConclusionsElastin histopathologic changes in BAV aortopathy correspond with differences in mechanical properties and this relationship is influenced by patient age. These novel findings provide additional mechanistic insights into aortic wall remodeling and support a more nuanced stratification of BAV patients by age.

Biomechanical Effects of Chronic Ankle Instability on the Talar Cartilage Matrix: The Value of T1ρ Relaxation Mapping Without and With Mechanical Loading.

T1ρ mapping has been proposed for the detection of early cartilage degeneration associated with chronic ankle instability (CAI). However, there are limited data surrounding the influence of ankle loading on T1ρ relaxation. To evaluate T1ρ relaxation times of talar cartilage, as an indicator of early degenerative changes, associated with CAI and to investigate the influence of acute axial in situ loading on T1ρ values in CAI patients and healthy controls. Prospective. A total of 9 patients (age=21.8 ± 2.5 years, male/female=2/7) with chronic ankle instability and 18 healthy control subjects (age=22.8 ± 3.6 years, male/female=5/13). 3 T. 3D gradient echo fast low-angle shot (FLASH) sequence augmented with a variable spin-lock preparation period. Ankle T1ρ mapping was performed without and with axial loading of 500 N. The talar cartilage was segmented in five coronal slices covering the central talocrural joint. Median talar T1ρ values were separately calculated for the medial and lateral facets. Mann-Whitney U and Wilcoxon signed-rank tests, significance level: P < 0.05. For the combined cohorts, the statistical analysis yielded significantly lower T1ρ values with loading compared to the no-load measurement for both the lateral (no load: [51.0 ± 4.0] msec, load: [49.5 ± 5.4] msec) as well as the medial compartment (no load: [50.0 ± 5.4] msec, load: [47.8 ± 6.8] msec). In the unloaded scans, the CAI patients showed significantly increased talar T1ρ values ([53.0 ± 7.4] mse ) compared to the healthy control subjects ([48.8 ± 4.1] msec) in the medial compartment. Increased talar T1ρ relaxation times in CAI patients compared to healthy controls suggest that T1ρ relaxation is a sensitive biomarker for CAI-induced early-stage cartilage degeneration. However, the load-induced T1ρ change did not prove to be a viable marker for the altered biomechanical properties of the hyaline talar cartilage. 2 LEVEL OF EFFICACY: Stage 2.

INTRA-ARTICULAR MINERALIZATION ON KNEE CT AND RISK OF CARTILAGE LOSS: THE MULTICENTER OSTEOARTHRITIS STUDY

Purpose: Intra-articular (IA) mineralization due to crystal deposition may contribute to OA pathology through inflammation, release of pro-catabolic factors, or altered cartilage biomechanical properties. Prior conflicting studies regarding whether chondrocalcinosis (from IA mineralization) is associated with OA structural progression were limited by the use of insensitive radiographs for visualizing IA mineralization. We studied the relation of IA mineralization on CT (a more sensitive modality) to cartilage loss on knee MRI in older adults, with particular attention to potential joint location- and tissue-specific effects of mineralization on cartilage pathology.

Label-free quantitative proteomics reveals molecular correlates of altered biomechanical properties in molar incisor hypomineralization (MIH): an in vitro study.

Molar-incisor hypomineralization (MIH) is a qualitative developmental defect of enamel that affects first permanent molars with or without affecting permanent incisors. We aimed to carry out a quantitative proteomics-based study to compare and evaluate proteins in sound and MIH-affected enamel. Ten blocks each of the MIH-affected enamel and sound enamel were processed and prepared for LC-MS/MS analysis. Label-free quantitation was carried out to evaluate the differentially expressed proteins in the two groups of samples. A significant increase in the number of proteins in MIH-affected enamel (50.3 ± 29.6) was observed compared to the sound enamel (21.4 ± 3.2). While proteins like collagens, α1-anti-trypsin, kallikrein-4 (KLK4), matrix metalloprotease-20 (MMP-20), alpha-2-macroglobulin, and alpha-2-HS-glycoprotein were upregulated in sound enamel, there was over-expression of albumin, calcium-binding proteins, anti-thrombin III, and dentin sialophosphoprotein (DSPP), along with proteins implicated in stress response and inflammatory processes in MIH. We propose that altered biomechanical properties of the enamel in MIH samples arise due to (i) down-regulation of proteins contributing to collagen biosynthesis and fibril formation; (ii) an overall imbalance in required levels of proteases (KLK4 and MMP-20) and anti-proteases (anti-thrombin-III which inhibits KLK-4), essential for optimal mineralization; (iii) very low levels of alpha-2-macroglobulin with important consequences in enamel mineralization and amelogenesis; and (iv) increased albumin in MIH, preventing proper growth of hydroxyapatite crystals. Increased inflammatory component was also seen in MIH; however, whether inflammation is a cause or consequence of the poor mineralization process needs to be assessed.

Nanoscale Extracellular Vesicles Carry the Mechanobiology Signatures of Breast Cancer Cells

Breast cancer cells secrete abundant nanometer-sized vesicles. Small extracellular vesicle (or sEV) cargos are known to have similar biomolecular signatures to their secreting parental breast cancer cells. However, whether malignant transformation modulates the physical and biomechanical profiles of secreted nanosized sEVs (40–120 nm) has not been established. Here, using multiparametric atomic force microscopy imaging, we directly compared the structure–mechanical properties (including topographic height, Young’s modulus, and adhesion) of breast cancer cell-derived sEVs and secreting cells. Our findings reveal that sEVs show reduced Young’s modulus concomitant with a decrease in cell stiffness as cells progress from nontumor to noninvasive to invasive breast cancer phenotypes across different probing forces, isolation techniques, and particle sizes. Further, single sEV structure–mechanical analysis of actual patient plasma samples showed alterations in biomechanical properties of sEVs in breast cancer patients compared to sEVs from benign healthy controls. Our study demonstrates that precise biomechanical fingerprinting of single nanoscale sEVs provides an attractive label-free, cell-free, and orthogonal approach to detect changes in parental cells, such as during malignant transformation.

Biomechanics of the optic nerve head and sclera in canine glaucoma: A brief review.

Glaucoma is a leading cause of irreversible blindness, a progressive optic neuropathy with retinal ganglion cell (RGC) death beginning in the optic nerve head (ONH). A primary risk factor for developing glaucoma is elevated intraocular pressure (IOP). Reducing IOP is the only treatment proven to be effective at delaying disease progression. Nevertheless, even when patients have their IOP reduced, the majority of them continue to lose vision. There are, in both humans and dogs, significant interindividual variabilities in susceptibilities to IOP-induced optic nerve damage. Vision loss progresses much more slowly in Beagles with open-angle glaucoma (OAG) caused by ADAMTS10mutation. This can be attributed to the mutation-related altered ocular biomechanical properties. The principal site of optic nerve (ON) damage in glaucoma is the ONH. It is suggested that the biomechanical properties of the ONH and the surrounding peripapillary sclera (PPS) contribute to glaucoma development and progression. As far as the beneficial biomechanical properties of the ONH and PPS for a decreased susceptibility and slow progression of glaucoma, data are inconsistent and conflicting. Recent biomechanical studies on beagles with ADAMTS10mutation demonstrated that the mutant dogs have mechanically weak posterior sclera. This weakness was associated with a reduced collagen density and a lower proportion of insoluble collagen. These changes, observed before glaucoma development, were considered intrinsic characteristics caused by the mutation rather than a secondary effect of IOP elevation. Further studies of ADAMTS10-OAG may elucidate the effects of altered biomechanical properties of ONH and PPS in determining the glaucoma progression.

Effects of emodin, a plant-derived anthraquinone, on TGF-β1-induced cardiac fibroblast activation and function.

Cardiac fibrosis accompanies a number of pathological conditions and results in altered myocardial structure, biomechanical properties and function. The signaling networks leading to fibrosis are complex, contributing to the general lack of progress in identifying effective therapeutic approaches to prevent or reverse this condition. Several studies have shown protective effects of emodin, a plant-derived anthraquinone, in animal models of fibrosis. A number of questions remain regarding the mechanisms whereby emodin impacts fibrosis. Transforming growth factor beta 1 (TGF-β1) is a potent stimulus of fibrosis and fibroblast activation. In the present study, experiments were performed to evaluate the effects of emodin on activation and function of cardiac fibroblasts following treatment with TGF-β1. We demonstrate that emodin attenuates TGF-β1-induced fibroblast activation and collagen accumulation in vitro. Emodin also inhibits activation of several canonical (SMAD2/3) and noncanonical (Erk1/2) TGF-β signaling pathways, while activating the p38 pathway. These results suggest that emodin may provide an effective therapeutic agent for fibrosis that functions via specific TGF-β signaling pathways.

Estimating Arterial Wall Deformations from Automatic Key-Point Detection and Matching

Assessing arterial-wall motion and deformations may reveal pathologic alterations in biomechanical properties of the parietal tissues and, thus, contribute to the detection of vascular disease onset. Ultrasound image sequences allow the observation of this motion and many methods have been developed to estimate temporal changes in artery diameter and wall thickness and to track 2-D displacements of selected points. Some methods enable the assessment of shearing or stretching within the wall, but none of them can estimate all these deformations simultaneously. The method herein proposed was devised to simultaneously estimate translation, compression, stretching and shearing of the arterial wall in ultrasound B-mode image sequences representing the carotid artery longitudinal section. Salient blob-like patterns, called key points, are automatically detected in each frame and matched between successive frames. A robust estimator based on an affine transformation model is then used to assess frame-to-frame motion explaining at best the key-point matches and to reject outliers. Realistic simulated image sequences were used to evaluate the accuracy and robustness of the method against ground truth. The method was also visually assessed on clinical image sequences, for which true deformations are unknown.