Clinical expression of programmed maxillary buccal expansion and buccolingual crown inclination with Invisalign EX30 and SmartTrack aligners and the effect of 1-week vs. 2-week aligner change regimes: A retrospective cohort study.

Objective: : This retrospective cohort study aimed to assess and compare the accuracy of 3 different Invisalign® treatment regimens in terms of variations of aligner change frequency and type of aligner material in achieving maxillary dental buccal expansion. Methods: : Altogether, 120 adult patients whose treatment involved maxillary dental expansion with Invisalign® were included. The patients were divided into 3 groups, with each group comprising 40 patients as follows: SmartTrack® 1-week changes (ST1), SmartTrack® 2-week changes (ST2), and EX30® 2-week changes (EX2). The groups were assessed by comparing actual changes achieved with those prescribed by ClinCheck®. The rates of clinically significant inaccuracies (CSI) observed for buccal expansion (≥ 0.5 mm) and buccolingual inclination (≥ 2°) during expansion were then determined. Results: : In terms of expansion, the ST1 group demonstrated the highest CSI rate at all tooth levels, whereas the ST2 group had the lowest rate of CSI and the lowest mean inaccuracy for each tooth level. In terms of buccolingual inclination, the ST1 group had the highest CSI rate across all tooth levels, whereas the EX2 group had the lowest CSI rate at all tooth levels except for the canine level where the ST2 group had the lowest CSI rate. A tendency toward overexpression of buccal crown inclination, and underexpression of buccal expansion was observed at all tooth levels. Conclusions: : Two-week aligner change regimens offer improved accuracy compared with 1-week aligner changes. SmartTrack® 2-week changes were the most accurate for buccal expansion, whereas EX30® 2-week changes were the most accurate for buccolingual inclination.

Mutation of highly conserved residues in loop 2 of the coronavirus macrodomain demonstrates that enhanced ADP-ribose binding is detrimental to infection.

All coronaviruses (CoVs) encode for a conserved macrodomain (Mac1) located in nonstructural protein 3 (nsp3). Mac1 is an ADP-ribosylhydrolase that binds and hydrolyzes mono-ADP-ribose from target proteins. Previous work has shown that Mac1 is important for virus replication and pathogenesis. Within Mac1, there are several regions that are highly conserved across CoVs, including the GIF (glycine-isoleucine-phenylalanine) motif. To determine how the biochemical activities of these residues impact CoV replication, the isoleucine and the phenylalanine residues were mutated to alanine (I-A/F-A) in both recombinant Mac1 proteins and recombinant CoVs, including murine hepatitis virus (MHV), Middle East respiratory syndrome coronavirus (MERS-CoV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The F-A mutant proteins had ADP-ribose binding and/or hydrolysis defects that led to attenuated replication and pathogenesis in cell culture and mice. In contrast, the I-A mutations had normal enzyme activity and enhanced ADP-ribose binding. Despite increased ADP-ribose binding, I-A mutant MERS-CoV and SARS-CoV-2 were highly attenuated in both cell culture and mice, indicating that this isoleucine residue acts as a gate that controls ADP-ribose binding for efficient virus replication. These results highlight the function of this highly conserved residue and provide unique insight into how macrodomains control ADP-ribose binding and hydrolysis to promote viral replication and pathogenesis.

An Update on the Current State of SARS-CoV-2 Mac1 Inhibitors.

Non-structural protein 3 (nsp3) from all coronaviruses (CoVs) contains a conserved macrodomain, known as Mac1, that has been proposed as a potential therapeutic target for CoVs due to its critical role in viral pathogenesis. Mac1 is an ADP-ribose binding protein and ADP-ribosylhydrolase that promotes replication and blocks IFN responses, though the precise mechanisms it uses to carry out these functions remain unknown. Over the past 3 years following the onset of COVID-19, several groups have used high-throughput screening with multiple assays and chemical modifications to create unique chemical inhibitors of the SARS-CoV-2 Mac1 protein. Here, we summarize the current efforts to identify selective and potent inhibitors of SARS-CoV-2 Mac1.

PARP12 is required to repress the replication of a Mac1 mutant coronavirus in a cell- and tissue-specific manner.

ADP-ribosyltransferases (ARTs) mediate the transfer of ADP-ribose from NAD+ to protein or nucleic acid substrates. This modification can be removed by several different types of proteins, including macrodomains. Several ARTs, also known as PARPs, are stimulated by interferon indicating ADP-ribosylation is an important aspect of the innate immune response. All coronaviruses (CoVs) encode for a highly conserved macrodomain (Mac1) that is critical for CoVs to replicate and cause disease, indicating that ADP-ribosylation can effectively control coronavirus infection. Our siRNA screen indicated that PARP12 might inhibit the replication of a murine hepatitis virus (MHV) Mac1 mutant virus in bone-marrow-derived macrophages (BMDMs). To conclusively demonstrate that PARP12 is a key mediator of the antiviral response to CoVs both in cell culture and in vivo, we produced PARP12-/-mice and tested the ability of MHV A59 (hepatotropic/neurotropic) and JHM (neurotropic) Mac1 mutant viruses to replicate and cause disease in these mice. Notably, in the absence of PARP12, Mac1 mutant replication was increased in BMDMs and mice. In addition, liver pathology was also increased in A59-infected mice. However, the PARP12 knockout did not restore Mac1 mutant virus replication to WT virus levels in all cell or tissue types and did not significantly increase the lethality of Mac1 mutant viruses. These results demonstrate that while PARP12 inhibits MHV Mac1 mutant virus infection, additional PARPs or innate immune factors must contribute to the extreme attenuation of this virus in mice. IMPORTANCE Over the last decade, the importance of ADP-ribosyltransferases (ARTs), also known as PARPs, in the antiviral response has gained increased significance as several were shown to either restrict virus replication or impact innate immune responses. However, there are few studies showing ART-mediated inhibition of virus replication or pathogenesis in animal models. We found that the CoV macrodomain (Mac1) was required to prevent ART-mediated inhibition of virus replication in cell culture. Using knockout mice, we found that PARP12, an interferon-stimulated ART, was required to repress the replication of a Mac1 mutant CoV both in cell culture and in mice, demonstrating that PARP12 represses coronavirus replication. However, the deletion of PARP12 did not fully rescue Mac1 mutant virus replication or pathogenesis, indicating that multiple PARPs function to counter coronavirus infection.

Two Commercially Available Blood-Stabilization Reagents Serve as Potent Inactivators of Coronaviruses.

The continued circulation of SARS-CoV-2 and the increasing frequency of coronavirus (CoV) outbreaks over the decades demonstrates the enduring threat that the CoV family poses. There remains a significant need to develop tools to monitor and prevent the spread of these viruses. We tested blood-stabilization reagents from two commercially available blood collection tubes (BCTs) for their ability to inactivate three different coronaviruses (MHV, OC-43, and SARS-CoV-2) and stabilize their RNA. Both Cell-Free DNA BCT® (cfDNA) and Cyto-Chex® BCT (CytoChex) reagents reduced infectious virus in the buffer to below the limit of detection within 18 h of treatment, with some conditions showing this effect in as little as 3 h. CytoChex had more potent activity than cfDNA as in all cases it more rapidly reduced the actively replicating virus to the limit of detection. Despite the rapid inactivation of the virus, both reagents effectively preserved viral RNA for 7 days. Finally, both reagents accelerated viral inactivation in blood compared to the control samples. These results indicate that cfDNA and CytoChex could be used to inactivate and preserve CoV RNA for detection and further testing.

SARS-CoV-2 Mac1 is required for IFN antagonism and efficient virus replication in cell culture and in mice.

Several coronavirus (CoV) encoded proteins are being evaluated as targets for antiviral therapies for COVID-19. Included in these drug targets is the conserved macrodomain, or Mac1, an ADP-ribosylhydrolase and ADP-ribose binding protein encoded as a small domain at the N terminus of nonstructural protein 3. Utilizing point mutant recombinant viruses, Mac1 was shown to be critical for both murine hepatitis virus (MHV) and severe acute respiratory syndrome (SARS)-CoV virulence. However, as a potential drug target, it is imperative to understand how a complete Mac1 deletion impacts the replication and pathogenesis of different CoVs. To this end, we created recombinant bacterial artificial chromosomes (BACs) containing complete Mac1 deletions (ΔMac1) in MHV, MERS-CoV, and SARS-CoV-2. While we were unable to recover infectious virus from MHV or MERS-CoV ΔMac1 BACs, SARS-CoV-2 ΔMac1 was readily recovered from BAC transfection, indicating a stark difference in the requirement for Mac1 between different CoVs. Furthermore, SARS-CoV-2 ΔMac1 replicated at or near wild-type levels in multiple cell lines susceptible to infection. However, in a mouse model of severe infection, ΔMac1 was quickly cleared causing minimal pathology without any morbidity. ΔMac1 SARS-CoV-2 induced increased levels of interferon (IFN) and IFN-stimulated gene expression in cell culture and mice, indicating that Mac1 blocks IFN responses which may contribute to its attenuation. ΔMac1 infection also led to a stark reduction in inflammatory monocytes and neutrophils. These results demonstrate that Mac1 only minimally impacts SARS-CoV-2 replication, unlike MHV and MERS-CoV, but is required for SARS-CoV-2 pathogenesis and is a unique antiviral drug target.

PARP12 is required to repress the replication of a Mac1 mutant coronavirus in a cell and tissue specific manner.

ADP-ribosyltransferases (ARTs) mediate the transfer of ADP-ribose from NAD + to protein or nucleic acid substrates. This modification can be removed by several different types of proteins, including macrodomains. Several ARTs, also known as PARPs, are stimulated by interferon, indicating ADP-ribosylation is an important aspect of the innate immune response. All coronaviruses (CoVs) encode for a highly conserved macrodomain (Mac1) that is critical for CoVs to replicate and cause disease, indicating that ADP-ribosylation can effectively control coronavirus infection. Our siRNA screen indicated that PARP12 might inhibit the replication of a MHV Mac1 mutant virus in bone-marrow derived macrophages (BMDMs). To conclusively demonstrate that PARP12 is a key mediator of the antiviral response to CoVs both in cell culture and in vivo , we produced PARP12 -/- mice and tested the ability of MHV A59 (hepatotropic/neurotropic) and JHM (neurotropic) Mac1 mutant viruses to replicate and cause disease in these mice. Notably, in the absence of PARP12, Mac1 mutant replication was increased in BMDMs and in mice. In addition, liver pathology was also increased in A59 infected mice. However, the PARP12 knockout did not restore Mac1 mutant virus replication to WT virus levels in all cell or tissue types and did not significantly increase the lethality of Mac1 mutant viruses. These results demonstrate that while PARP12 inhibits MHV Mac1 mutant virus infection, additional PARPs or innate immune factors must contribute to the extreme attenuation of this virus in mice. IMPORTANCE: Over the last decade, the importance of ADP-ribosyltransferases (ARTs), also known as PARPs, in the antiviral response has gained increased significance as several were shown to either restrict virus replication or impact innate immune responses. However, there are few studies showing ART-mediated inhibition of virus replication or pathogenesis in animal models. We found that the CoV macrodomain (Mac1) was required to prevent ART-mediated inhibition of virus replication in cell culture. Here, using knockout mice, we found that PARP12, an interferon-stimulated ART, was required to repress the replication of a Mac1 mutant CoV both in cell culture and in mice, demonstrating that PARP12 represses coronavirus replication. However, the deletion of PARP12 did not fully rescue Mac1 mutant virus replication or pathogenesis, indicating that multiple PARPs function to counter coronavirus infection.

SARS-CoV-2 Mac1 is required for IFN antagonism and efficient virus replication in mice.

Several coronavirus (CoV) encoded proteins are being evaluated as targets for antiviral therapies for COVID-19. Included in this set of proteins is the conserved macrodomain, or Mac1, an ADP-ribosylhydrolase and ADP-ribose binding protein. Utilizing point mutant recombinant viruses, Mac1 was shown to be critical for both murine hepatitis virus (MHV) and severe acute respiratory syndrome (SARS)-CoV virulence. However, as a potential drug target, it is imperative to understand how a complete Mac1 deletion impacts the replication and pathogenesis of different CoVs. To this end, we created recombinant bacterial artificial chromosomes (BACs) containing complete Mac1 deletions (ΔMac1) in MHV, MERS-CoV, and SARS-CoV-2. While we were unable to recover infectious virus from MHV or MERS-CoV ΔMac1 BACs, SARS-CoV-2 ΔMac1 was readily recovered from BAC transfection, indicating a stark difference in the requirement for Mac1 between different CoVs. Furthermore, SARS-CoV-2 ΔMac1 replicated at or near wild-type levels in multiple cell lines susceptible to infection. However, in a mouse model of severe infection, ΔMac1 was quickly cleared causing minimal pathology without any morbidity. ΔMac1 SARS-CoV-2 induced increased levels of interferon (IFN) and interferon-stimulated gene (ISG) expression in cell culture and mice, indicating that Mac1 blocks IFN responses which may contribute to its attenuation. ΔMac1 infection also led to a stark reduction in inflammatory monocytes and neutrophils. These results demonstrate that Mac1 only minimally impacts SARS-CoV-2 replication, unlike MHV and MERS-CoV, but is required for SARS-CoV-2 pathogenesis and is a unique antiviral drug target. SIGNIFICANCE: All CoVs, including SARS-CoV-2, encode for a conserved macrodomain (Mac1) that counters host ADP-ribosylation. Prior studies with SARS-CoV-1 and MHV found that Mac1 blocks IFN production and promotes CoV pathogenesis, which has prompted the development of SARS-CoV-2 Mac1 inhibitors. However, development of these compounds into antivirals requires that we understand how SARS-CoV-2 lacking Mac1 replicates and causes disease in vitro and in vivo . Here we found that SARS-CoV-2 containing a complete Mac1 deletion replicates normally in cell culture but induces an elevated IFN response, has reduced viral loads in vivo , and does not cause significant disease in mice. These results will provide a roadmap for testing Mac1 inhibitors, help identify Mac1 functions, and open additional avenues for coronavirus therapies.

Crosstalk between ERK and MRTF-A signaling regulates TGFß1-induced epithelial-mesenchymal transition.

Epithelial-mesenchymal transition (EMT) is a physiological process that is essential during embryogenesis and wound healing and also contributes to pathologies including fibrosis and cancer. EMT is characterized by marked gene expression changes, loss of cell-cell contacts, remodeling of the cytoskeleton, and acquisition of enhanced motility. In the late stages of EMT, cells can exhibit myofibroblast-like properties with enhanced expression of the mesenchymal protein marker α-smooth muscle actin and contractile activity. Transforming growth factor (TGF)-ß1 is a well-known inducer of EMT and it activates a plethora of signaling cascades including extracellular signal-regulated kinase (ERK). Previous reports have demonstrated a role for ERK signaling in the early stages of EMT, but the molecular impacts of ERK signaling on the late stages of EMT are still unknown. Here, we found that inhibition of the phosphorylation of ERK enhances focal adhesions, stress fiber formation, cell contractility, and gene expression changes associated with TGFß1-induced EMT in mammary epithelial cells. These effects are mediated in part by the phosphorylation state and subcellular localization of myocardin-related transcription factor-A. These findings indicate that the intricate crosstalk between signaling cascades plays an important role in regulating the progression of EMT and suggests new approaches to control EMT processes.

Unique Mutations in the Murine Hepatitis Virus Macrodomain Differentially Attenuate Virus Replication, Indicating Multiple Roles for the Macrodomain in Coronavirus Replication.

All coronaviruses (CoVs) contain a macrodomain, also termed Mac1, in nonstructural protein 3 (nsp3) that binds and hydrolyzes mono-ADP-ribose (MAR) covalently attached to proteins. Despite several reports demonstrating that Mac1 is a prominent virulence factor, there is still a limited understanding of its cellular roles during infection. Currently, most of the information regarding the role of CoV Mac1 during infection is based on a single point mutation of a highly conserved asparagine residue, which makes contact with the distal ribose of ADP-ribose. To determine if additional Mac1 activities contribute to CoV replication, we compared the replication of murine hepatitis virus (MHV) Mac1 mutants, D1329A and N1465A, to the previously mentioned asparagine mutant, N1347A. These residues contact the adenine and proximal ribose in ADP-ribose, respectively. N1465A had no effect on MHV replication or pathogenesis, while D1329A and N1347A both replicated poorly in bone marrow-derived macrophages (BMDMs), were inhibited by PARP enzymes, and were highly attenuated in vivo. Interestingly, D1329A was also significantly more attenuated than N1347A in all cell lines tested. Conversely, D1329A retained some ability to block beta interferon (IFN-ß) transcript accumulation compared to N1347A, indicating that these mutations have different effects on Mac1 functions. Combining these two mutations resulted in a virus that was unrecoverable, suggesting that the combined activities of Mac1 are essential for MHV replication. We conclude that Mac1 has multiple functions that promote the replication of MHV, and that these results provide further evidence that Mac1 is a prominent target for anti-CoV therapeutics. IMPORTANCE In the wake of the COVID-19 epidemic, there has been a surge to better understand how CoVs replicate and to identify potential therapeutic targets that could mitigate disease caused by SARS-CoV-2 and other prominent CoVs. The highly conserved macrodomain, also termed Mac1, is a small domain within nonstructural protein 3. It has received significant attention as a potential drug target, as previous studies demonstrated that it is essential for CoV pathogenesis in multiple animal models of infection. However, the functions of Mac1 during infection remain largely unknown. Here, using targeted mutations in different regions of Mac1, we found that Mac1 has multiple functions that promote the replication of MHV, a model CoV, and, therefore, is more important for MHV replication than previously appreciated. These results will help guide the discovery of these novel functions of Mac1 and the development of inhibitory compounds targeting this domain.

An MHV macrodomain mutant predicted to lack ADP-ribose binding activity is severely attenuated, indicating multiple roles for the macrodomain in coronavirus replication.

All coronaviruses (CoVs) contain a macrodomain, also termed Mac1, in non-structural protein 3 (nsp3) which binds and hydrolyzes ADP-ribose covalently attached to proteins. Despite several reports demonstrating that Mac1 is a prominent virulence factor, there is still a limited understanding of its cellular roles during infection. Currently, most of the information regarding the role of CoV Mac1 during infection is based on a single point mutant of a highly conserved asparagine-to-alanine mutation, which is known to largely eliminate Mac1 ADP-ribosylhydrolase activity. To determine if Mac1 ADP-ribose binding separately contributes to CoV replication, we compared the replication of a murine hepatitis virus (MHV) Mac1 mutant predicted to dramatically reduce ADP-ribose binding, D1329A, to the previously mentioned asparagine mutant, N1347A. D1329A and N1347A both replicated poorly in bone-marrow derived macrophages (BMDMs), were inhibited by PARP enzymes, and were highly attenuated in vivo . However, D1329A was significantly more attenuated than N1347A in all cell lines tested that were susceptible to MHV infection. In addition, D1329A retained some ability to block IFN-ß transcript accumulation compared to N1347A, indicating that these two mutants impacted distinct Mac1 functions. Mac1 mutants predicted to eliminate both binding and hydrolysis activities were unrecoverable, suggesting that the combined activities of Mac1 may be essential for MHV replication. We conclude that Mac1 has multiple roles in promoting the replication of MHV, and that these results provide further evidence that Mac1 could be a prominent target for anti-CoV therapeutics. IMPORTANCE: In the wake of the COVID-19 epidemic, there has been a surge to better understand how CoVs replicate, and to identify potential therapeutic targets that could mitigate disease caused by SARS-CoV-2 and other prominent CoVs. The highly conserved macrodomain, also termed Mac1, is a small domain within non-structural protein 3. It has received significant attention as a potential drug target as previous studies demonstrated that it is essential for CoV pathogenesis in multiple animal models of infection. However, the various roles and functions of Mac1 during infection remain largely unknown. Here, utilizing recombinant Mac1 mutant viruses, we have determined that different biochemical functions of Mac1 have distinct roles in the replication of MHV, a model CoV. These results indicate that Mac1 is more important for CoV replication than previously appreciated, and could help guide the development of inhibitory compounds that target unique regions of this protein domain.

Transition-Metal Catalysis of Triene 6π Electrocyclization: The π-Complexation Strategy Realized.

Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal-alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5 H5 )Ru(NCMe)3 ]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition-metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations.

Acid-Induced Liberation of Polysubstituted Cyclopentadiene Ligands from Cyclopentadienyl Cobalt: A [2 + 2 + 1] Cycloaddition Route toward 1,2,4-Trisubstituted Cyclopentadienes.

Here, we report that trifluoroacetic acid (TFAH) induces demetallation and protodesilylation of the cyclopentadiene ligand in cobalt-η4-cyclopentadiene complexes of general formula [(η5-C5H5)Co(η4-exo-C(TMS)═C(SO2Ph)CH═CRCH(CO2Et))] (1-Ph, R = Ph; 1-ArtBu, R = p-C6H4tBu; 1-ArNMe2, R = p-C6H4NMe2; and 1-Me, R = Me). The trisubstituted cyclopentadiene products are isolated as a mixture of two tautomers, [(CH2C(SO2Ph)═CHC(CO2Et)═CR)] (8-R-A) and [(CH═C(SO2Ph)CH2C(CO2Et)═CR)] (8-R-B). The endo isomer, [(η5-C5H5)Co(η4-endo-C(TMS)═C(SO2Ph)CH═CPhCH(CO2Et))] (1-Ph-endo), also undergoes demetallation and protodesilylation to give 8-Ph-A and 8-Ph-B in excellent yield. The cobalt-cyclopentadiene complex, [(η5-C5H5)Co(η4-exo-C(TMS)═C(SO2Ph)CH═C(CO2Me)CH(CO2Et))] (1-CO2Me), undergoes demetallation and protodesilylation upon treatment with TFAH to give a hydrogen-bonded fulvenol (8-CO2Me). Liberation of the ethoxy-substituted cyclopentadiene ligand of [(η5-C5H5)Co(η4-exo-C(TMS)═C(SO2Ph)CH═C(OEt)CH(CO2Et))] (1-OEt) leads to formation of a cyclopentenone derivative (11). Thermolysis of 8-Ph-A/8-Ph-B in the presence of maleimide leads to a highly functionalized Diels-Alder adduct, whereas 8-Ph-A/8-Ph-B serves as precursors to trisubstituted ruthenocenes by in situ deprotonation and reaction with [(η5-C5R5)Ru(NCMe)3]PF6 (16-H, R = H; 16-Me, R = Me).

TGFß1-induced expression of caldesmon mediates epithelial-mesenchymal transition.

Epithelial-mesenchymal transition (EMT) is an important process that mediates organ development and wound healing, and in pathological contexts, it can contribute to the progression of fibrosis and cancer. During EMT, cells exhibit marked changes in cytoskeletal organization and increased expression of a variety of actin associated proteins. Here, we sought to determine the role of caldesmon in mediating EMT in response to transforming growth factor (TGF)-ß1. We find that the expression level and phosphorylation state of caldesmon increase as a function of time following induction of EMT by TGFß1 and these changes in caldesmon correlate with increased focal adhesion number and size and increased cell contractility. Knockdown and forced expression of caldesmon in epithelial cells reveals that caldesmon expression plays an important role in regulating the expression of the myofibroblast marker alpha smooth muscle actin. Results from these studies provide insight into the role of cytoskeletal associated proteins in the regulation of EMT and may suggest ways to target the cell cytoskeleton for regulating EMT processes.

The PELskin project: part II-investigating the physical coupling between flexible filaments in an oscillating flow.

The fluid-structure interaction mechanisms of a coating composed of flexible flaps immersed in a periodically oscillating channel flow is here studied by means of numerical simulation, employing the Euler-Bernoulli equations to account for the flexibility of the structures. A set of passively actuated flaps have previously been demonstrated to deliver favourable aerodynamic impact when attached to a bluff body undergoing periodic vortex shedding. As such, the present configuration is identified to provide a useful test-bed to better understand this mechanism, thought to be linked to experimentally observed travelling waves. Having previously validated and elucidated the flow mechanism in Paper 1 of this series, we hereby undertake a more detailed analysis of spectra obtained for different natural frequency of structures and different configurations, in order to better characterize the mechanisms involved in the organized motion of the structures. Herein, this wave-like behaviour, observed at the tips of flexible structures via interaction with the fluid flow, is characterized by examining the time history of the filaments motion and the corresponding effects on the fluid flow, in terms of dynamics and frequency of the fluid velocity. Results indicate that the wave motion behaviour is associated with the formation of vortices in the gaps between the flaps, which itself are a function of the structural resistance to the cross flow. In addition, formation of vortices upstream of the leading and downstream of the trailing flap is seen, which interact with the formation of the shear-layer on top of the row. This leads to a phase shift in the wave-type motion along the row that resembles the observation in the cylinder case.

Cell-cell contact and matrix adhesion promote αSMA expression during TGFß1-induced epithelial-myofibroblast transition via Notch and MRTF-A.

During epithelial-mesenchymal transition (EMT) epithelial cells lose cell-cell adhesion, exhibit morphological changes, and upregulate the expression of cytoskeletal proteins. Previous studies have demonstrated that complete disruption of cell-cell contact can promote transforming growth factor (TGF)-ß1-induced EMT and the expression of the myofibroblast marker alpha smooth muscle actin (αSMA). Furthermore, increased cell spreading mediates TGFß1-induced αSMA expression during EMT. Here, we sought to examine how the presence of partial cell-cell contacts impacts EMT. A microfabrication approach was employed to decouple the effects of cell-cell contact and cell-matrix adhesion in TGFß1-induced EMT. When cell spreading is controlled, the presence of partial cell-cell contacts enhances expression of αSMA. Moreover, cell spreading and intercellular contacts together control the subcellular localization of activated Notch1 and myocardin related transcription factor (MRTF)-A. Knockdown of Notch1 or MRTF-A as well as pharmacological inhibition of these pathways abates the cell-cell contact mediated expression of αSMA. These data suggest that the interplay between cell-matrix adhesion and intercellular adhesion is an important determinant for some aspects of TGFß1-induced EMT.

Computational fluid dynamics in the microcirculation and microfluidics: what role can the lattice Boltzmann method play?

Patient-specific simulations, efficient parametric analyses, and the study of complex processes that are otherwise experimentally intractable are facilitated through the use of Computational Fluid Dynamics (CFD) to study biological flows. This review discusses various CFD methodologies that have been applied across different biological scales, from cell to organ level. Through this discussion the lattice Boltzmann method (LBM) is highlighted as an emerging technique capable of efficiently simulating fluid problems across the midrange of scales; providing a practical analytical tool compared to methods more attuned to the extremities of scale. Furthermore, the merits of the LBM are highlighted through examples of previous applications and suggestions for future research are made. The review focusses on applications in the midrange bracket, such as cell-cell interactions, the microcirculation, and microfluidic devices; wherein the inherent mesoscale nature of the LBM renders it well suited to the incorporation of fluid-structure interaction effects, molecular/particle interactions and interfacial dynamics. The review demonstrates that the LBM has the potential to become a valuable tool across a range of emerging areas in bio-CFD, such as understanding and predicting disease, designing lab-on-a-chip devices, and elucidating complex biological processes.

Application of a lattice Boltzmann-immersed boundary method for fluid-filament dynamics and flow sensing.

Complex fluid-structure interactions between elastic filaments, or cilia, immersed in viscous flows are commonplace in nature and bear important roles. Some biological systems have evolved to interpret flow-induced motion into signals for the purpose of feedback response. Given the challenges associated with extracting meaningful experimental data at this scale, there has been particular focus on the numerical study of these effects. Porous models have proven useful where cilia arrangements are relatively dense, but for more sparse configurations the dynamic interactions of individual structures play a greater role and direct modelling becomes increasingly necessary. The present study reports efforts towards explicit modelling of regularly spaced wall-mounted cilia using a lattice Boltzmann-immersed boundary method. Both steady and forced unsteady 2D channel flows at different Reynolds numbers are investigated, with and without the presence of a periodic array of elastic inextensible filaments. It is demonstrated that the structure response depends significantly on Reynolds number. For low Reynolds flow, the recirculation vortex aft of successive filaments is small relative to the cilia spacing and does not fully bridge the gap, in which case the structure lags the flow. At higher Reynolds number, when this gap is fully bridged the structure and flow move in phase. The trapping of vortices between cilia is associated with relatively lower wall shear stress. At low to intermediate Reynolds, vortex bridging is incomplete and large deflection is still possible, which is reflected in the tip dynamics and wall shear stress profiles.

Cytoskeletal signaling in TGFß-induced epithelial-mesenchymal transition.

Epithelial-mesenchymal transition (EMT) is a physiological process that plays an important role in embryonic development and wound healing and is appropriated during pathological conditions including fibrosis and cancer metastasis. EMT can be initiated by a variety of factors, including transforming growth factor (TGF)-ß, and is characterized by loss of epithelial features including cell-cell contacts and apicobasal polarity and acquisition of a motile, mesenchymal phenotype. A key feature of EMT is reorganization of the cytoskeleton and recent studies have elucidated regulation mechanisms governing this process. This review describes changes in gene expression patterns of cytoskeletal associated proteins during TGFß-induced EMT. It further reports TGFß-induced intracellular signaling cascades that regulate cytoskeletal reorganization during EMT. Finally, it highlights how changes in cytoskeletal architecture during EMT can regulate gene expression, thus further promoting EMT progression.

Matrix Rigidity Mediates TGFß1-Induced Epithelial-Myofibroblast Transition by Controlling Cytoskeletal Organization and MRTF-A Localization.

Myofibroblasts mediate normal wound healing and upon chronic activation can contribute to the development of pathological conditions including organ fibrosis and cancer. Myofibroblasts can develop from epithelial cells through an epithelial-mesenchymal transition (EMT) during which epithelial cells exhibit drastic morphological changes and upregulate cytoskeletal associated proteins that enable exertion of large contractile forces and remodeling of the surrounding microenvironment. Increased matrix rigidity is a hallmark of fibrosis and tumor progression and mechanical tension has been identified as a regulator of EMT; however, the mechanisms governing the mechanical regulation of EMT are not completely understood. Here, we find that matrix rigidity regulates transforming growth factor (TGF)-ß1-induced EMT, with rigid substrata enabling increased myofibroblast marker expression, cell morphology changes, and cytoskeletal reorganization while soft matrices block these changes. Furthermore, we find that matrix rigidity controls the subcellular localization of myocardin related transcription factor (MRTF)-A, a regulator of cytoskeletal protein expression that contributes to the acquisition of myogenic features during EMT. Results from these studies provide insight into how biophysical cues contribute to myofibroblast development from epithelial cells and may suggest ways to enhance wound healing or to engineer therapeutic solutions for fibrosis and cancer.