Open Access Publications

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Open access publications by faculty, postdocs, and graduate students in the Department of Biomedical Engineering.

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Quantitative effects of off-resonance related distortion on brain mechanical property estimation with magnetic resonance elastography
(NMR in Biomedicine, 2021-09-20) McIlvain, Grace; McGarry, Matthew D. J.; Johnson, Curtis L.
Off-resonance related geometric distortion can impact quantitative MRI techniques, such as magnetic resonance elastography (MRE), and result in errors to these otherwise sensitive metrics of brain health. MRE is a phase contrast technique to determine the mechanical properties of tissue by imaging shear wave displacements and estimating tissue stiffness through inverse solution of Navier's equation. In this study, we systematically examined the quantitative effects of distortion and corresponding correction approaches on MRE measurements through a series of simulations, phantom models, and in vivo brain experiments. We studied two different k-space trajectories, echo-planar imaging and spiral, and we determined that readout time, off-resonance gradient strength, and the combination of readout direction and off-resonance gradient direction, impact the estimated mechanical properties. Images were also processed through traditional distortion correction pipelines, and we found that each of the correction mechanisms works well for reducing stiffness errors, but are limited in cases of very large distortion. The ability of MRE to detect subtle changes to neural tissue health relies on accurate, artifact-free imaging, and thus off-resonance related geometric distortion must be considered when designing sequences and protocols by limiting readout time and applying correction where appropriate.
Correlated noise in brain magnetic resonance elastography
(Magnetic Resonance in Medicine, 2021-10-22) Hannum, Ariel J.; McIlvain, Grace; Sowinski, Damian; McGarry, Matthew D. J.; Johnson, Curtis L.
Purpose: Magnetic resonance elastography (MRE) uses phase-contrast MRI to generate mechanical property maps of the in vivo brain through imaging of tissue deformation from induced mechanical vibration. The mechanical property estimation process in MRE can be susceptible to noise from physiological and mechanical sources encoded in the phase, which is expected to be highly correlated. This correlated noise has yet to be characterized in brain MRE, and its effects on mechanical property estimates computed using inversion algorithms are undetermined. Methods: To characterize the effects of signal noise in MRE, we conducted 3 experiments quantifying (1) physiomechanical sources of signal noise, (2) physiological noise because of cardiac-induced movement, and (3) impact of correlated noise on mechanical property estimates. We use a correlation length metric to estimate the extent that correlated signal persists in MRE images and demonstrate the effect of correlated noise on property estimates through simulations. Results: We found that both physiological noise and vibration noise were greater than image noise and were spatially correlated across all subjects. Added physiological and vibration noise to simulated data resulted in property maps with higher error than equivalent levels of Gaussian noise. Conclusion: Our work provides the foundation to understand contributors to brain MRE data quality and provides recommendations for future work to correct for signal noise in MRE.
Knee joint biomechanics during gait improve from 3 to 6 months after anterior cruciate ligament reconstruction
(Journal of Orthopaedic Research, 2022-01-06) Neal, Kelsey; Williams, Jack R.; Alfayyadh, Abdulmajeed; Capin, Jacob J.; Khandha, Ashutosh; Manal, Kurt; Snyder‐Mackler, Lynn; Buchanan, Thomas S.
Gait alterations after anterior cruciate ligament reconstruction (ACLR) are commonly reported and have been linked to posttraumatic osteoarthritis development. While knee gait alterations have been studied at several time points after ACLR, little is known about how these biomechanical variables change earlier than 6 months after surgery, nor is much known about how they differ over the entire stance phase of gait. The purpose of this study was to examine knee gait biomechanical variables over their entire movement pattern through stance at both 3 and 6 months after ACLR and to study the progression of interlimb asymmetry between the two postoperative time points. Thirty-five individuals underwent motion analysis during overground walking 3 (3.2 ± 0.5) and 6 (6.4 ± 0.7) months after ACLR. Knee biomechanical variables were compared between limbs and across time points through 100% of stance using statistical parametric mapping; this included a 2 × 2 (Limb × Time) repeated measures analysis of variance and two-tailed t-tests. Smaller knee joint angles, moments, extensor forces, and medial compartment forces were present in the involved versus uninvolved limb. Interlimb asymmetries were present at both time points but were less prevalent at 6 months. The uninvolved limb's biomechanical variables stayed relatively consistent over time, while the involved limb's trended toward that of the uninvolved limb. Statement of Clinical Significance: Interventions to correct asymmetrical gait patterns after ACLR may need to occur early after surgery and may need to focus on multiple parts of stance phase.
Tuning Hydrogel Adhesivity and Degradability to Model the Influence of Premetastatic Niche Matrix Properties on Breast Cancer Dormancy and Reactivation
(Advanced Biology, 2022-03-11) Farino Reyes, Cindy J.; Slater, John H.
Dormant, disseminated tumor cells (DTCs) can persist for decades in secondary tissues before being reactivated to form tumors. The properties of the premetastatic niche can influence the DTC phenotype. To better understand how matrix properties of premetastatic niches influence DTC behavior, three hydrogel formulations are implemented to model a permissive niche and two nonpermissive niches. Poly(ethylene glycol) (PEG)-based hydrogels with varying adhesivity ([RGDS]) and degradability ([N-vinyl pyrrolidinone]) are implemented to mimic a permissive niche with high adhesivity and degradability and two nonpermissive niches, one with moderate adhesivity and degradability and one with no adhesivity and high degradability. The influence of matrix properties on estrogen receptor positive (ER+) breast cancer cells (MCF7s) is determined via a multimetric analysis. MCF7s cultured in the permissive niche adopted a growth state, while those in the nonpermissive niche with reduced adhesivity and degradability underwent tumor mass dormancy. Complete removal of adhesivity while maintaining high degradability induced single cell dormancy. The ability to mimic reactivation of dormant cells through a dynamic increase in [RGDS] is also demonstrated. This platform provides the capability of inducing growth, dormancy, and reactivation of ER+ breast cancer and can be useful in understanding how premetastatic niche properties influence cancer cell fate.
Relationships between aggression, sensation seeking, brain stiffness, and head impact exposure: Implications for head impact prevention in ice hockey
(Brain and Behavior, 2022-04-23) DiFabio, Melissa S.; Smith, Daniel R.; Breedlove, Katherine M.; Buckley, Thomas A.; Johnson, Curtis L.
Objectives: The objectives of this study were to (1) examine the relationship between the number of head impacts sustained in a season of men's collegiate club ice hockey and behavioral traits of aggression and sensation seeking, and (2) explore the neural correlates of these behaviors using neuroimaging. Design: Retrospective cohort study. Methods: Participants (n = 18) completed baseline surveys to quantify self-reported aggression and sensation-seeking tendencies. Aggression related to playing style was quantified through penalty minutes accrued during a season. Participants wore head impact sensors throughout a season to quantify the number of head impacts sustained. Participants (n = 15) also completed baseline anatomical and magnetic elastography neuroimaging scans to measure brain volumetric and viscoelastic properties. Pearson correlation analyses were performed to examine relationships between (1) impacts, aggression, and sensation seeking, and (2) impacts, aggression, and sensation seeking and brain volume, stiffness, and damping ratio, as an exploratory analysis. Results: Number of head impacts sustained was significantly related to the number of penalty minutes accrued, normalized to number of games played (r = .62, p < .01). Our secondary, exploratory analysis revealed that number of impacts, sensation seeking, and aggression were related to stiffness or damping ratio of the thalamus, amygdala, hippocampus, and frontal cortex, but not volume. Conclusions: A more aggressive playing style was related to an increased number of head impacts sustained, which may provide evidence for future studies of head impact prevention. Further, magnetic resonance elastography may aid to monitor behavior or head impact exposure. Researchers should continue to examine this relationship and consider targeting behavioral modification programs of aggression to decrease head impact exposure in ice hockey.
Altered brain functional connectivity in the frontoparietal network following an ice hockey season
(European Journal of Sport Science, 2022-05-08) DiFabio, Melissa S.; Smith, Daniel R.; Breedlove, Katherine M.; Pohlig, Ryan T.; Buckley, Thomas A.; Johnson, Curtis L.
Sustaining sports-related head impacts has been reported to result in neurological changes that potentially lead to later-life neurological disease. Advanced neuroimaging techniques have been used to detect subtle neurological effects resulting from head impacts, even after a single competitive season. The current study used resting-state functional magnetic resonance imaging to assess changes in functional connectivity of the frontoparietal network, a brain network responsible for executive functioning, in collegiate club ice hockey players over one season. Each player was scanned before and after the season and wore accelerometers to measure head impacts at practices and home games throughout the season. We examined pre- to post-season differences in connectivity within the frontoparietal and default mode networks, as well as the relationship between the total number of head impacts sustained and changes in connectivity. We found a significant interaction between network region of interest and time point (p = .016), in which connectivity between the left and right posterior parietal cortex seed regions increased over the season (p < .01). Number of impacts had a significant effect on frontoparietal network connectivity, such that more impacts were related to greater connectivity differences over the season (p = .042). Overall, functional connectivity increased in ice hockey athletes over a season between regions involved in executive functioning, and sensory integration, in particular. Furthermore, those who sustained more impacts had the greatest changes in connectivity. Consistent with prior findings in resting-state sports-related head impact literature, these findings have been suggested to represent brain injury. Highlights: Functional connectivity of the frontoparietal network significantly increased between the pre- and post-season, which may be a compensatory mechanism driven by neural tissue injury caused by repetitive head impacts. Changes in frontoparietal network connectivity are related to head impact exposure, measured as the number of head impacts sustained in a single season. Functional connectivity of the default mode network did not change over an ice hockey season.
Membrane-wrapped nanoparticles for nucleic acid delivery
(Biomaterials Science, 2022-06-29) Scully, Mackenzie A.; Sterin, Eric H.; Day, Emily S.
There is an unmet need for carriers that can deliver nucleic acids (NAs) to cancer cells and tumors to perpetuate gene regulation and manage disease progression. Membrane-wrapped nanoparticles (NPs) can be loaded with exogenously designed nucleic acid cargoes, such as plasmid deoxyribonucleic acid (pDNA), messenger ribonucleic acid (mRNA), small interfering RNA (siRNA), microRNA (miRNA), and immunostimulatory CpG oligodeoxynucleotides (CpG ODNs), to mitigate challenges presented by NAs’ undesirable negative charge, hydrophilicity, and relatively large size. By conjugating or encapsulating NAs within membrane-wrapped NPs, various physiological barriers can be overcome so that NAs experience increased blood circulation half-lives and enhanced accumulation in intended sites. This review discusses the status of membrane-wrapped NPs as NA delivery vehicles and their advancement in gene regulation for cancer management in vitro and in vivo. With continued development, membrane-wrapped NPs have great potential as future clinical tools to treat cancer and other diseases with a known genetic basis.
Secretion of the disulphide bond generating catalyst QSOX1 from pancreatic tumour cells into the extracellular matrix: Association with extracellular vesicles and matrix proteins
(Journal of Extracellular Biology, 2022-07-02) Millar-Haskell, Catherine S.; Sperduto, John L.; Slater, John H.; Thorpe, Colin; Gleghorn, Jason P.
Quiescin sulfhydryl oxidase 1 (QSOX1) is a disulphide bond generating catalyst that is overexpressed in solid tumours. Expression of QSOX1 is linked to cancer cell invasion, tumour grade, and aberrant extracellular matrix (ECM) protein deposition. While the secreted version of QSOX1 is known to be present in various fluids and secretory tissues, its presence in the ECM of cancer is less understood. To characterize secreted QSOX1, we isolated extracellular vesicles (and particles) (EV(P)s) from conditioned media using ultracentrifugation and separated the supernatant using tangential flow filtration. We discovered that most of the secreted QSOX1 resides in the EVP-depleted supernatant and in the soluble protein fraction. Very little QSOX1 could be detected in the EVP fraction. We used immunofluorescence to image subpopulations of EVs and found QSOX1 in Golgi-derived vesicles and medium/large vesicles, but in general, most extracellular QSOX1 was not attributed to these vesicles. Next, we quantified QSOX1 co-localization with the EV marker Alix. For the medium/large EVs, ∼98% contained QSOX1 when fibronectin was used as a coating. However, on collagen coatings, only ∼60% of these vesicles contained QSOX1, suggesting differences in EV cargo based on ECM coated surfaces. About 10% of small EVs co-localized with QSOX1 on every ECM protein surface except for collagen (0.64%). We next investigated adhesion of QSOX1 to ECM proteins in vitro and in situ and found that QSOX1 preferentially adheres to fibronectin, laminins, and Matrigel compared to gelatin and collagen. This mechanism was found to be, in part, mediated by the formation of mixed disulphides between QSOX1 and cysteine-rich ECM proteins. In summary, we found that QSOX1 (1) is in subpopulations of medium/large EVs, (2) seems to interact with small Alix+ EVs, and (3) adheres to cysteine-rich ECM proteins, potentially through the formation of intermediate disulphides. These observations offer significant insight into how enzymes, such as QSOX1, can facilitate matrix remodelling events in solid tumour progression.
Isocorrole-Loaded Polymer Nanoparticles for Photothermal Therapy under 980 nm Light Excitation
(ACS Omega, 2022-10-18) Marek, Maximilian R. J.; Pham, Trong-Nhan; Wang, Jianxin; Cai, Qiuqi; Yap, Glenn P. A.; Day, Emily S.; Rosenthal, Joel
Photothermal therapy (PTT) is a promising treatment option for diseases, including cancer, arthritis, and periodontitis. Typical photothermal agents (PTAs) absorb light in the near-infrared (NIR)-I region of 650–900 nm with a predominant focus around 800 nm, as these wavelengths are minimally absorbed by water and blood in the tissue. Recently, interest has grown in developing nanomaterials that offer more efficient photothermal conversion and that can be excited by light close to or within the NIR-II window of 1000–1700 nm, which offers less absorption by melanin. Herein, we report on the development of 5,5-diphenyl isocorrole (5-DPIC) complexes containing either Zn(II) or Pd(II) (Zn[5-DPIC] and Pd[5-DPIC], respectively) that absorb strongly across the 850–1000 nm window. We also show that poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with these designer isocorroles exhibit low toxicity toward triple-negative breast cancer (TNBC) cells in the dark but enable efficient heat production and photothermal cell ablation upon excitation with 980 nm light. These materials represent an exciting new platform for 980 nm activated PTT and demonstrate the potential for designer isocorroles to serve as effective PTAs.
Stress deprivation of tendon explants or Tpm3.1 inhibition in tendon cells reduces F-actin to promote a tendinosis-like phenotype
(Molecular Biology of the Cell, 2022-12-01) Inguito, Kameron L.; Schofield, Mandy M.; Faghri, Arya D.; Bloom, Ellen T.; Heino, Marissa; West, Valerie C.; Ebron, Karl Matthew M.; Elliot, Dawn M.; Parreno, Justin
Actin is a central mediator between mechanical force and cellular phenotype. In tendons, it is speculated that mechanical stress deprivation regulates gene expression by reducing filamentous (F)-actin. However, the mechanisms regulating tenocyte F-actin remain unclear. Tropomyosins (Tpms) are master regulators of F-actin. There are more than 40 Tpm isoforms, each having the unique capability to stabilize F-actin subpopulations. We investigated F-actin polymerization in stress-deprived tendons and tested the hypothesis that stress fiber–associated Tpm(s) stabilize F-actin to regulate cellular phenotype. Stress deprivation of mouse tail tendon down-regulated tenogenic and up-regulated protease (matrix metalloproteinase-3) mRNA levels. Concomitant with mRNA modulation were increases in G/F-actin, confirming reduced F-actin by tendon stress deprivation. To investigate the molecular regulation of F-actin, we identified that tail, Achilles, and plantaris tendons express three isoforms in common: Tpm1.6, 3.1, and 4.2. Tpm3.1 associates with F-actin in native and primary tenocytes. Tpm3.1 inhibition reduces F-actin, leading to decreases in tenogenic expression, increases in chondrogenic expression, and enhancement of protease expression in mouse and human tenocytes. These expression changes by Tpm3.1 inhibition are consistent with tendinosis progression. A further understanding of F-actin regulation in musculoskeletal cells could lead to new therapeutic interventions to prevent alterations in cellular phenotype during disease progression.
MRI-based measurement of in vivo disc mechanics in a young population due to flexion, extension, and diurnal loading
(JOR Spine, 2023-01-09) Meadows, Kyle D.; Peloquin, John M.; Newman, Harrah R.; Cauchy, Peter J. K.; Vresilovic, Edward J.; Elliott, Dawn M.
Background: Intervertebral disc degeneration is often implicated in low back pain; however, discs with structural degeneration often do not cause pain. It may be that disc mechanics can provide better diagnosis and identification of the pain source. In cadaveric testing, the degenerated disc has altered mechanics, but in vivo, disc mechanics remain unknown. To measure in vivo disc mechanics, noninvasive methods must be developed to apply and measure physiological deformations. Aim: Thus, this study aimed to develop methods to measure disc mechanical function via noninvasive MRI during flexion and extension and after diurnal loading in a young population. This data will serve as baseline disc mechanics to later compare across ages and in patients. Materials & Methods: To accomplish this, subjects were imaged in the morning in a reference supine position, in flexion, in extension, and at the end of the day in a supine position. Disc deformations and vertebral motions were used to quantify disc axial strain, changes in wedge angle, and anterior–posterior (A-P) shear displacement. T2 weighted MRI was also used to evaluate disc degeneration via Pfirrmann grading and T2 time. All measures were then tested for effect of sex and disc level. Results: We found that flexion and extension caused level-dependent strains in the anterior and posterior of the disc, changes in wedge angle, and A-P shear displacements. Flexion had higher magnitude changes overall. Diurnal loading did not cause level-dependent strains but did cause small level-dependent changes in wedge angle and A-P shear displacements. Discussion: Correlations between disc degeneration and mechanics were largest in flexion, likely due to the smaller contribution of the facet joints in this condition. Conclusion: In summary, this study established methods to measure in vivo disc mechanical function via noninvasive MRI and established a baseline in a young population that may be compared to older subjects and clinical disorders in the future.
E-Selectin Targeted Gold Nanoshells to Inhibit Breast Cancer Cell Binding to Lung Endothelial Cells
(ACS Applied Nano Material, 2023-01-27) Fereshteh, Z.; Dang, M. N.; Wenck, C.; Day, E. S.; Slater, J. H.
Extravasation of circulating tumor cells (CTCs) from the vasculature is a key step in cancer metastasis. CTCs bind to cell adhesion molecules (CAMs) expressed by endothelial cells (ECs) for flow arrest prior to extravasation. While a number of EC-expressed CAMs have been implicated in facilitating CTC binding, this work investigated the efficacy of inhibiting cancer cell binding to human lung microvascular ECs via antibody blocking of E-selectin using antibody-functionalized gold nanoshells (NS). The antibody-functionalized gold NS were synthesized using both directional and non-directional antibody conjugation techniques with variations in synthesis parameters (linker length, amount of passivating agents, and ratio of antibodies to NS) to gain a better understanding of these properties on the resultant hydrodynamic diameter, zeta potential, and antibody loading density. We quantified the ability of E-selectin antibody-functionalized NS to bind human lung microvascular endothelial cells (HMVEC-Ls) under non-inflamed and inflamed (TNF-α) conditions to inhibit binding of triple-negative MDA-MB-231s. E-selectin-targeted NS prepared using non-directional conjugation had higher antibody loading than those prepared via directional conjugation, resulting in the conjugates having similar overall binding to HMVEC-Ls at a given antibody concentration. E-selectin-targeted NS reduced MDA-MB-231 binding to HMVEC-Ls by up to 41% as determined using an in vitro binding assay. These results provide useful insights into the characteristics of antibody-functionalized NS prepared under different conditions while also demonstrating proof of concept that these conjugates hold potential to inhibit CTC binding to ECs, a critical step in extravasation during metastasis.
In vivo estimation of anisotropic mechanical properties of the gastrocnemius during functional loading with MR elastography
(Physics in Medicine & Biology, 2023-02-06) Smith, Daniel R.; Caban-Rivera, Diego A.; Williams, L. Tyler; Van Houten, Elijah E. W.; Bayly, Phil V.; Paulsen, Keith D.; McGarry, Matthew D. J.; Johnson, Curtis L.
Objective. In vivo imaging assessments of skeletal muscle structure and function allow for longitudinal quantification of tissue health. Magnetic resonance elastography (MRE) non-invasively quantifies tissue mechanical properties, allowing for evaluation of skeletal muscle biomechanics in response to loading, creating a better understanding of muscle functional health. Approach. In this study, we analyze the anisotropic mechanical response of calf muscles using MRE with a transversely isotropic, nonlinear inversion algorithm (TI-NLI) to investigate the role of muscle fiber stiffening under load. We estimate anisotropic material parameters including fiber shear stiffness (${\mu }_{1}$), substrate shear stiffness (${\mu }_{2}$), shear anisotropy ($\phi $), and tensile anisotropy ($\zeta $) of the gastrocnemius muscle in response to both passive and active tension. Main results. In passive tension, we found a significant increase in ${\mu }_{1},$ $\phi ,$ and $\zeta $ with increasing muscle length. While in active tension, we observed increasing ${\mu }_{2}$ and decreasing $\phi $ and $\zeta $ during active dorsiflexion and plantarflexion—indicating less anisotropy—with greater effects when the muscles act as agonist. Significance. The study demonstrates the ability of this anisotropic MRE method to capture the multifaceted mechanical response of skeletal muscle to tissue loading from muscle lengthening and contraction.
Biomimetic Substrate to Probe Dynamic Interplay of Topography and Stiffness on Cardiac Fibroblast Activation
(ACS Omega, 2023-02-14) Cao, Zheng; Ball, Jacob K.; Lateef, Ali H.; Virgile, Connor P.; Corbin, Elise A.
Materials with the ability to change properties can expand the capabilities of in vitro models of biological processes and diseases as it has become increasingly clear that static, stiff materials with smooth surfaces fall short in recapitulating the in vivo cellular microenvironment. Here, we introduce a patterned material that can be rapidly stiffened and softened in situ in response to an external magnetic field through the addition of magnetic inclusions into a soft silicone elastomer with topographic surface patterning. This substrate can be used for cell culture to investigate short-term cellular responses to dynamic stiffening or softening and the interaction with topography that encourages cells to assume a specific morphology. We investigated short-term cellular responses to dynamic stiffening or softening in human ventricular cardiac fibroblasts. Our results indicate that the combination of dynamic changes in stiffness with and without topographic cues induces different effects on the alignment and activation or deactivation of myofibroblasts. Cells cultured on patterned substrates exhibited a more aligned morphology than cells cultured on flat material; moreover, cell alignment was not dependent on substrate stiffness. On a patterned substrate, there was no significant change in the number of activated myofibroblasts when the material was temporally stiffened, but temporal softening caused a significant decrease in myofibroblast activation (50% to 38%), indicating a competing interaction of these characteristics on cell behavior. This material provides a unique in vitro platform to observe the time-dependent dynamics of cells by better mimicking more complex behaviors and realistic microenvironments for investigating biological processes, such as the development of fibrosis.
Reverberant magnetic resonance elastographic imaging using a single mechanical driver
(Physics in Medicine & Biology, 2023-02-27) Kabir, Irteza Enan; Caban-Rivera, Diego A.; Ormachea, Juvenal; Parker, Kevin J.; Johnson, Curtis L.; Doyley, Marvin M.
Reverberant elastography provides fast and robust estimates of shear modulus; however, its reliance on multiple mechanical drivers hampers clinical utility. In this work, we hypothesize that for constrained organs such as the brain, reverberant elastography can produce accurate magnetic resonance elastograms with a single mechanical driver. To corroborate this hypothesis, we performed studies on healthy volunteers (n = 3); and a constrained calibrated brain phantom containing spherical inclusions with diameters ranging from 4–18 mm. In both studies (i.e. phantom and clinical), imaging was performed at frequencies of 50 and 70 Hz. We used the accuracy and contrast-to-noise ratio performance metrics to evaluate reverberant elastograms relative to those computed using the established subzone inversion method. Errors incurred in reverberant elastograms varied from 1.3% to 16.6% when imaging at 50 Hz and 3.1% and 16.8% when imaging at 70 Hz. In contrast, errors incurred in subzone elastograms ranged from 1.9% to 13% at 50 Hz and 3.6% to 14.9% at 70 Hz. The contrast-to-noise ratio of reverberant elastograms ranged from 63.1 to 73 dB compared to 65 to 66.2 dB for subzone elastograms. The average global brain shear modulus estimated from reverberant and subzone elastograms was 2.36 ± 0.07 kPa and 2.38 ± 0.11 kPa, respectively, when imaging at 50 Hz and 2.70 ± 0.20 kPa and 2.89 ± 0.60 kPa respectively, when imaging at 70 Hz. The results of this investigation demonstrate that reverberant elastography can produce accurate, high-quality elastograms of the brain with a single mechanical driver.
The Sensorimotor System Modulates Muscular Co-Contraction Relative to Visuomotor Feedback Responses to Regulate Movement Variability
(Journal of Neurophysiology, 2023-04-01) Calalo, Jan A.; Roth, Adam M.; Lokesh, Rakshith; Sullivan, Seth R.; Wong, Jeremy D.; Semrau, Jennifer A.; Cashaback, Joshua G. A.
The naturally occurring variability in our movements often poses a significant challenge when attempting to produce precise and accurate actions, which is readily evident when playing a game of darts. Two differing, yet potentially complementary, control strategies that the sensorimotor system may use to regulate movement variability are impedance control and feedback control. Greater muscular co-contraction leads to greater impedance that acts to stabilize the hand, while visuomotor feedback responses can be used to rapidly correct for unexpected deviations when reaching toward a target. Here, we examined the independent roles and potential interplay of impedance control and visuomotor feedback control when regulating movement variability. Participants were instructed to perform a precise reaching task by moving a cursor through a narrow visual channel. We manipulated cursor feedback by visually amplifying movement variability and/or delaying the visual feedback of the cursor. We found that participants decreased movement variability by increasing muscular co-contraction, aligned with an impedance control strategy. Participants displayed visuomotor feedback responses during the task but, unexpectedly, there was no modulation between conditions. However, we did find a relationship between muscular co-contraction and visuomotor feedback responses, suggesting that participants modulated impedance control relative to feedback control. Taken together, our results highlight that the sensorimotor system modulates muscular co-contraction, relative to visuomotor feedback responses, to regulate movement variability and produce accurate actions. NEW & NOTEWORTHY: The sensorimotor system has the constant challenge of dealing with the naturally occurring variability in our movements. Here, we investigated the potential roles of muscular co-contraction and visuomotor feedback responses to regulate movement variability. When we visually amplified movements, we found that the sensorimotor system primarily uses muscular co-contraction to regulate movement variability. Interestingly, we found that muscular co-contraction was modulated relative to inherent visuomotor feedback responses, suggesting an interplay between impedance and feedback control.
Connecting clinical, environmental, and genetic factors point to an essential role for vitamin A signaling in the pathogenesis of congenital diaphragmatic hernia
(American Journal of Physiology - Lung Cellular and Molecular Physiology, 2023-04-01) Gilbert, Rachel M.; Gleghorn, and Jason P.
Congenital diaphragmatic hernia (CDH) is a developmental disorder that results in incomplete diaphragm formation, pulmonary hypoplasia, and pulmonary hypertension. Although a variety of genes have been linked to its etiology, CDH is not a monogenetic disease, and the cause of the condition is still unclear in the vast majority of clinical cases. By comparing human clinical data and experimental rodent data from the literature, we present clear support demonstrating the importance of vitamin A (vitA) during the early window of pregnancy when the diaphragm and lung are forming. Alteration of vitA signaling via dietary and genetic perturbations can create diaphragmatic defects. Unfortunately, vitA deficiency is chronic among people of child-bearing age, and this early window of diaphragm development occurs before many might be aware of pregnancy. Furthermore, there is an increased demand for vitA during this critical period, which exacerbates the likelihood of deficiency. It would be beneficial for the field to further investigate the connections between maternal vitA and CDH incidence, with the goal of determining vitA status as a CDH risk factor. Regular clinical monitoring of vitA levels in child-bearing years is a tractable method by which CDH outcomes could be prevented or improved.
Orthopaedics and Biomedical Engineering Design: An Innovative Duet toward a Better Tomorrow
(Journal of the Pediatric Orthopaedic Society of North America, 2023-05-01) Su, Alvin W.; Khandha, Ashutosh; Bansal, Sonia; Ty, Jennifer M.; Baldys, Andrew; French, Zachary P.; Puccinelli, John P.
The main purpose of this article is to explore the benefits and dynamics of collaborations between orthopaedic surgeons and biomedical engineering (BME) undergraduates and faculties in the context of engineering design programs as well as clinical immersion programs. An outline of strategies to navigate the seemingly complex landscape of hospitals and universities is presented through models of orthopedic-BME collaborations at two distinct academic practice settings in the United States. In addition to (four) examples of BME design projects sponsored by the clinicians, funding and intellectual property (IP), priority of time management, as well as the positive impact on student education are also discussed. Design collaborations can provide unique educational and research opportunities for the development of undergraduate engineering students to become future leaders; at the same time, this simultaneously facilitates innovative solutions fulfilling unmet clinical needs for orthopedic clinicians. Overall, we hope to provide references and resources for those who are interested in developing similar orthopedic-BME design framework for future innovation and student education in real-life orthopedic research translation.
Transcriptional regulation of Sis1 promotes fitness but not feedback in the heat shock response
(eLife, 2023-05-17) Grade, Rania; Singh, Abhyudai; Ali, Asif; Pincus, David
The heat shock response (HSR) controls expression of molecular chaperones to maintain protein homeostasis. Previously, we proposed a feedback loop model of the HSR in which heat-denatured proteins sequester the chaperone Hsp70 to activate the HSR, and subsequent induction of Hsp70 deactivates the HSR (Krakowiak et al., 2018; Zheng et al., 2016). However, recent work has implicated newly synthesized proteins (NSPs) – rather than unfolded mature proteins – and the Hsp70 co-chaperone Sis1 in HSR regulation, yet their contributions to HSR dynamics have not been determined. Here, we generate a new mathematical model that incorporates NSPs and Sis1 into the HSR activation mechanism, and we perform genetic decoupling and pulse-labeling experiments to demonstrate that Sis1 induction is dispensable for HSR deactivation. Rather than providing negative feedback to the HSR, transcriptional regulation of Sis1 by Hsf1 promotes fitness by coordinating stress granules and carbon metabolism. These results support an overall model in which NSPs signal the HSR by sequestering Sis1 and Hsp70, while induction of Hsp70 – but not Sis1 – attenuates the response.
Cholesterol-substituted 3,4-ethylenedioxythiophene (EDOT-MA-cholesterol) and Poly(3,4-ethylenedioxythiophene) (PEDOT-MA-cholesterol)
(Giant, 2023-05-23) Wu, Yuhang; Nagane, Samadhan S.; Baugh, Quintin; Lo, Chun-Yuan; Chhatre, Shrirang S.; Lee, Junghyun; Sitarik, Peter; Kayser, Laure V.; Martin, David C.
Cholesterol is a rigid, crystalline, non-polar natural substance that exists in animal blood and cell membranes. Some of its derivatives are known to form ordered liquid crystalline mesophases under suitable conditions. In this work, we carefully examined the influence of cholesterol substitution on the characteristics of 3,4-ethylenedioxythiophene (EDOT-MA-cholesterol) and its corresponding polymer poly(3,4-ethylenedioxythiophene) (PEDOT-MA-cholesterol) synthesized by both chemical and electrochemical polymerization. We found evidence for an ordered lamellar (smectic-like) structure in the EDOT-MA-cholesterol monomer by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction techniques. The ordered phase was observed to form on cooling from the isotropic melt at about 80 °C. Due to the insulating and bulky cholesterol side group on the EDOT monomer, we found that there was a maximum charge density for electrodeposition at ∼ 0.155 C.cm−2. A series of electrodepositions were performed from 0 to 0.155 C.cm−2 for probing the change of the charge transport with more charges used for the electrodeposition. We found that the impedance increased in the high-frequency range (above 104 Hz) and decreased in the low-frequency range (below 102 Hz). Three equivalent circuit models were proposed for fitting impedance data at different charge densities for a better understanding of the film growth process. The suppressed cyclic voltammogram (CV) of PEDOT-MA-cholesterol showed that the charge storage capability was essentially eliminated in the thickest films. The limited doping of the films was corroborated by their diminished electrochromic behavior, polaron-dominating absorption in UV-vis, overoxidized S 2p X-ray Photoelectron Spectroscopy (XPS) signal of electrodeposited films, and proton Nuclear Magnetic Resonance (1H NMR) of chemically polymerized samples. Dense film morphologies were confirmed by scanning electron microscopy (SEM). Grazing incident X-ray diffraction (GIWAXS) indicated the disrupted stacking of conjugated chains, which correlated with the decreased conductivity of the PEDOT-MA-cholesterol films. The measurement of the electrical conductivity gave a value of around 3.30 × 10−6 S.cm−1 which is about six orders of magnitude lower than has been seen in PEDOT (∼3 S.cm-1). Graphical abstract available at: https://doi.org/10.1016/j.giant.2023.100163

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