Ultimately Adaptive Fluid Interfacial Phospholipid Membranes Unveiled Unanticipated High Cellular Mechanical Work

Living cells actively interact biochemically and mechanically with the surrounding extracellular matrices (ECMs) and undergo dramatic morphological and dimensional transitions, concomitantly remodeling ECMs. However, there is no suitable method to quantitatively discuss the contribution of mechanical interactions in such mutually adaptive processes. Herein, a highly deformable "living" cellular scaffold is developed to evaluate overall mechanical energy transfer between cell and ECMs. It is based on the water-perfluorocarbon interface decorated with phospholipids bearing a cell-adhesive ligand and fluorescent tag. The bioinert nature of the phospholipid membranes prevents the formation of solid-like protein nanofilms at the fluid interface, enabling to visualize and quantify cellular mechanical work against the ultimately adaptive model ECM. A new cellular wetting regime is identified, wherein interface deformation proceeds to cell flattening, followed by its eventual restoration. The cellular mechanical work during this adaptive wetting process is one order of magnitude higher than those reported with conventional elastic platforms. The behavior of viscous liquid drops at the air-water interface can simulate cellular adaptive wetting, suggesting that overall viscoelasticity of the cell body predominates the emergent wetting regime and regulates mechanical output. Cellular-force-driven high-energy states on the adaptive platform can be useful for cell fate manipulation.

Opposing genetic polymorphisms of two ABC transporters contribute to the variation of nukacin resistance in Streptococcus mutans

Streptococcus mutans is a cariogenic bacterium that produces a variety of bacteriocins and retains resistance to these bacteriocins. In this study, we investigated the susceptibility of 127 S. mutans strains to nukacins produced by Staphylococcus spp., which are commensal bacteria in humans. We detected diverse susceptibilities among strains. Nineteen strains had a disrupted LctF (type I), which is responsible for nukacin susceptibility, whereas the remaining 108 strains had an intact LctF (type II) and displayed resistance to nukacins. However, the type I strains still showed resistance to nukacins to some extent. Interestingly, 18/19 (94.7%) type I strains carried a mukA-T locus, which is related to the synthesis of mutacin K8, and mukFEG, an ABC transporter. In contrast, among type II strains, only 6/108 strains (5.6%) had both the mukA-T locus and mukFEG, 19/108 strains (17.6%) carried only mukFEG, and 83/108 strains (76.9%) harbored neither mukA-T nor mukFEG. We also found that MukF had two variants: 305 amino acids (type α) and 302 amino acids (type β). All type I strains showed a type α (MukFα), whereas most type II strains with mukFEG (22/25 strains) had a type β (MukFβ). Then, we constructed a mukFEG-deletion mutant complemented with MukFαEG or MukFβEG and found that only MukFαEG was involved in nukacin resistance. The nukacin resistance capability of type II-LctFEG was stronger than that of MukFαEG. In conclusion, we identified a novel nukacin resistance factor, MukFEG, and either LctFEG or MukFEG was active in most strains via genetic polymorphisms depending on mukA-T genes.

IMPORTANCE

Streptococcus mutans is an important pathogenic bacterium not only for dental caries but also for systemic diseases. S. mutans is known to produce a variety of bacteriocins and to retain resistance these bacteriocins. In this study, two ABC transporters, LctFEG and MukFEG, were implicated in nukacin resistance and each ABC transporter has two subtypes, active and inactive. Of the two ABC transporters, only one ABC transporter was always resistant, while the other ABC transporter was inactivated by genetic mutation. Interestingly, this phenomenon was defined by the presence or absence of the mutacin K8 synthesis gene region, one of the bacteriocins of S. mutans. This suggests that the resistance acquisition is tightly controlled in each strain. This study provides important evidence that the insertion of bacteriocin synthesis genes is involved in the induction of genetic polymorphisms and suggests that bacteriocin synthesis genes may play an important role in bacterial evolution.

Ionic Liquid Interface as a Cell Scaffold

In sharp contrast to conventional solid/hydrogel platforms, water-immiscible liquids, such as perfluorocarbons and silicones, allow the adhesion of mammalian cells via protein nanolayers (PNLs) formed at the interface. However, fluorocarbons and silicones, which are typically used for liquid cell culture, possess only narrow ranges of physicochemical parameters and have not allowed for a wide variety of cell culturing environments. In this paper, it is proposed that water-immiscible ionic liquids (ILs) are a new family of liquid substrates with tunable physicochemical properties and high solvation capabilities. Tetraalkylphosphonium-based ILs are identified as non-cytotoxic ILs, whereon human mesenchymal stem cells are successfully cultured. By reducing the cation charge distribution, or ionicity, via alkyl chain elongation, the interface allows cell spreading with matured focal contacts. High-speed atomic force microscopy observations of the PNL formation process suggest that the cation charge distribution significantly altered the protein adsorption dynamics, which are associated with the degree of protein denaturation and the PNL mechanics. Moreover, by exploiting dissolution capability of ILs, an ion-gel cell scaffold is fabricated. This enables to further identify the significant contribution of bulk subphase mechanics to cellular mechanosensing in liquid-based culture scaffolds.

Freeze-dried noncoagulating platelet-derived factor concentrate is a safe and effective treatment for early knee osteoarthritis

PURPOSE

While a wide variety of platelet-rich plasma (PRP) solutions has been developed, innovation continues. In this case, the freeze-dried platelet factor concentrate (PFC-FD) represents another step in PRP refinement. The preparation of PFC-FD at a central laboratory with freeze drying for shelf stabilization should provide additional quality improvements if clinical effectiveness can be demonstrated. Therefore, this study was undertaken to assess the safety and effectiveness of PFC-FD in a prospective open-label trial of patients suffering from knee osteoarthritis (OA).

METHODS

312 consecutive knee OA patients (67% female, mean age 63 ± 10 years), were prospectively recruited in an outpatient knee clinic in Japan. Of these, 10 (3.2%) were lost to follow-up at < 12 months and 17 (5.5%) sought additional knee therapy during the follow-up period. The primary outcome of interest was achievement of the OMERACT-OARSI responder criteria with secondary outcomes of adverse events and PROMs scores 1, 3, 6, 12 months following a single PFC-FD injection.

RESULTS

285 patients (91%) completed 12 month PROMs. The 17 who sought additional therapy were considered failures leaving an effective sample size of 302 for our primary outcome in which 62% of patients achieved OMERACT-OARSI responder status by 12 months. This varied by OA class with Kellgren-Lawrence grade 4 patients 3.6 times less likely to be responders than grade 1-2 patients. 6% of patients experienced a non-serious adverse event, primarily pain or swelling at the injection site.

CONCLUSIONS

PFC-FD provides an observable clinical improvement in 62% of knee OA patients at 12 months post-injection with very little risk of any clinically relevant adverse event. Of course, nearly 40% of patients did not experience an observable clinical improvement, primarily among those with worse KL grades.

LEVEL OF EVIDENCE

Therapeutic, Level II.

Relationship between CD4+ T-cell counts at baseline and initial periodontal treatment efficacy in patients undergoing treatment for HIV infection: A retrospective observational study

AIM

To retrospectively investigate the relationship between the CD4+ T-cell counts at baseline and the efficacy of the initial periodontal treatment of patients undergoing treatment for human immunodeficiency virus (HIV) infection using the periodontal inflamed surface area (PISA).

MATERIALS AND METHODS

Thirty-three patients with chronic periodontitis who had undergone periodontal examination at baseline and after the initial periodontal treatment were enrolled. PISA was calculated from the periodontal probing depth and bleeding on probing, and the ratio of PISA after treatment to that at baseline (PISA response ratio) was calculated. Groups with a response ratio of <1 and ≥1 were defined as the improvement and the non-improvement groups, respectively.

RESULTS

PISA after the initial periodontal treatment significantly decreased compared with that at baseline (p < .05). A weak negative correlation was found between the PISA response ratio and CD4+ T-cell counts at baseline (p < .05). The CD4+ T-cell counts at baseline were significantly higher in the improvement group than in the non-improvement group (p < .05). Multivariate analysis revealed that the CD4+ T-cell counts at baseline was an independent factor that affects the PISA (p < .05).

CONCLUSIONS

The higher the CD4+ T-cell counts at baseline in patients undergoing treatment for HIV infection, the more effective the initial periodontal treatment.

Mapping stress inside living cells by atomic force microscopy in response to environmental stimuli

The response of cells to environmental stimuli, under either physiological or pathological conditions, plays a key role in determining cell fate toward either adaptive survival or controlled death. The efficiency of such a feedback mechanism is closely related to the most challenging human diseases, including cancer. Since cellular responses are implemented through physical forces exerted on intracellular components, more detailed knowledge of force distribution through modern imaging techniques is needed to ensure a mechanistic understanding of these forces. In this work, we mapped these intracellular forces at a whole-cell scale and with submicron resolution to correlate intracellular force distribution to the cytoskeletal structures. Furthermore, we visualized dynamic mechanical responses of the cells adapting to environmental modulations in situ. Such task was achieved by using an informatics-assisted atomic force microscope (AFM) indentation technique where a key step was Markov-chain Monte Carlo optimization to search for both the models used to fit indentation force-displacement curves and probe geometry descriptors. We demonstrated force dynamics within cytoskeleton, as well as nucleoskeleton in living cells which were subjected to mechanical state modulation: myosin motor inhibition, micro-compression stimulation and geometrical confinement manipulation. Our results highlight the alteration in the intracellular prestress to attenuate environmental stimuli; to involve in cellular survival against mechanical signal-initiated death during cancer growth and metastasis; and to initiate cell migration.

Manipulating the Dynamic Adaptivity of a Fluid Interface to Maintain the Multipotency of Mesenchymal Stromal Cells

The native extracellular matrix is highly dynamic with continuous mutual feedback between cells being responsible for many important cell function regulators. However, establishing bidirectional interaction between complex adaptive microenvironments and cells remains elusive. Herein an adaptive biomaterial based on lysozyme monolayers self-assembled at a perfluorocarbon FC40-water interface is reported. The dynamic adaptivity of interfacially assembled protein nanosheets is modulated independently of bulk mechanical properties by covalent crosslinking. This provides a scenario to establish bidirectional interactions of cells with liquid interfaces of varying dynamic adaptivity. This is found that growth and multipotency of human mesenchymal stromal cells (hMSCs) are enhanced at the highly adaptive fluid interface. The multipotency retention of hMSCs is mediated by low cell contractility and metabolomic activity involving the continuous mutual feedback between the cells and materials. Consequently, an understanding of the cells' response to dynamic adaptivity has substantial implications for regenerative medicine and tissue engineering.

Growth and Migration Blocking Effect of Nanaomycin K, a Compound Produced by Streptomyces sp., on Prostate Cancer Cell Lines In Vitro and In Vivo

Since castration-resistant prostate cancer (CRPC) acquires resistance to molecularly targeted drugs, discovering a class of drugs with different mechanisms of action is needed for more efficient treatment. In this study, we investigated the anti-tumor effects of nanaomycin K, derived from "Streptomyces rosa subsp. notoensis" OS-3966. The cell lines used were LNCaP (non-CRPC), PC-3 (CRPC), and TRAMP-C2 (CRPC). Experiments included cell proliferation analysis, wound healing analysis, and Western blotting. In addition, nanaomycin K was administered intratumorally to TRAMP-C2 carcinoma-bearing mice to assess effects on tumor growth. Furthermore, immuno-histochemistry staining was performed on excised tissues. Nanaomycin K suppressed cell proliferation in all cell lines (p < 0.001) and suppressed wound healing in TRAMP-C2 (p = 0.008). Nanaomycin K suppressed or showed a tendency to suppress the expression of N-cadherin, Vimentin, Slug, and Ras in all cell lines, and suppressed the phosphorylation of p38, SAPK/JNK, and Erk1/2 in LNCaP and TRAMP-C2. In vivo, nanaomycin K safely inhibited tumor growth (p = 0.001). In addition, suppression of phospho-Erk1/2 and increased expression of E-cadherin and cleaved-Caspase3 were observed in excised tumors. Nanaomycin K inhibits tumor growth and suppresses migration by inhibiting epithelial-mesenchymal transition in prostate cancer. Its mechanism of action is related to the inhibition of phosphorylation of the MAPK signaling pathway.

Polarity Does Not Matter: Molecular Weight Reverses the Photoisomerization-Induced Phase Separation of an Azobenzene-Bearing Polymer

We find the non-canonical photoisomerization-induced phase separation of an azobenzene-bearing polymer. The polymer composed of acrylate-based azobenzene (AzoAA) and N,N-dimethylacrylamide (DMA), namely poly(AzoAA-r-DMA), phase separates under visible light-induced cis-to-trans isomerization at high molecular weight, whereas the phase separation is realized under ultraviolet light-induced trans-to-cis isomerization at low molecular weight. Conventionally, the origin of photoisomerization-induced phase separation is believed to arise from the difference in polarity between the apolar trans and polar cis states; thereby the direction of phase changes, either to separate or dissolute, is uniquely determined by the polarity changes during the isomerization of azobenzene. Contrary to this common perception, the poly(AzoAA-r-DMA) in this study phase separates through both trans and cis isomerization, depending on the molecular weight. The non-canonical phase separation of poly(AzoAA-r-DMA) reported herein suggest that molecular weight plays a significant role in determining the phase behavior of azobenzene-bearing polymers. This study provides a platform for the development of spatial temporally controlled delivery vehicles and microreactors. This article is protected by copyright. All rights reserved.

Photoactivatable surfaces resolve the impact of gravity vector on collective cell migratory characteristics

Despite considerable interest in the impact of space travel on human health, the influence of the gravity vector on collective cell migration remains unclear. This is primarily because of the difficulty in inducing collective migration, where cell clusters appear in an inverted position against gravity, without cellular damage. In this study, photoactivatable surfaces were used to overcome this challenge. Photoactivatable surfaces enable the formation of geometry-controlled cellular clusters and the remote induction of cellular migration via photoirradiation, thereby maintaining the cells in the inverted position. Substrate inversion preserved the circularity of cellular clusters compared to cells in the normal upright position, with less leader cell appearance. Furthermore, the inversion of cells against the gravity vector resulted in the remodeling of the cytoskeletal system via the strengthening of external actin bundles. Within the 3D cluster architecture, enhanced accumulation of active myosin was observed in the upper cell-cell junction, with a flattened apical surface. Depending on the gravity vector, attenuating actomyosin activity correlates with an increase in the number of leader cells, indicating the importance of cell contractility in collective migration phenotypes and cytoskeletal remodeling.

Oxidative stress impairs the calcification ability of human dental pulp cells

Background

The relationship between internal root resorption and oxidative stress has not yet been reported. This study aimed to add molecular insight into internal root resorption. The present study was conducted to investigate the effect of hydrogen peroxide (H₂O₂) as an inducer of oxidative stress on the calcification ability of human dental pulp cells (hDPCs) and the involvement of inositol 1, 4, 5-trisphosphate (IP3).

Material and methods

hDPCs (Lonza, Basel, Switzerland) were exposed to H₂O₂. Cell viability and reactive oxygen species (ROS) production were then evaluated. To investigate the effect of H₂O₂ on the calcification ability of hDPCs, real-time PCR for alkaline phosphatase (ALP) mRNA expression, ALP staining, and Alizarin red staining were performed. Data were compared with those of hDPCs pretreated with 2-aminoethyldiphenylborate (2-APB), which is an IP3 receptor inhibitor.

Results

H₂O₂ at concentrations above 250 µM significantly reduced cell viability (P < 0.01). More ROS production occurred in 100 µM H₂O₂-treated hDPCs than in control cells (P < 0.01). 2-APB significantly decreased the production (P < 0.05). H₂O₂-treated hDPCs showed significant reductions in ALP mRNA expression (P < 0.01), ALP activity (P < 0.01), and mineralized nodule deposition compared with negative control cells (P < 0.01). 2-APB significantly inhibited these reductions (P < 0.01, P < 0.05 and P < 0.01, respectively). Data are representative of three independent experiments with three replicates for each treatment and values are expressed as means ± SD.

Conclusion

To the best of our knowledge, this is the first study documenting the involvement of IP₃ signaling in the calcification ability of human dental pulp cells impaired by H₂O₂.

Static and photoresponsive dynamic materials to dissect physical regulation of cellular functions

Recent progress in mechanobiology has highlighted the importance of physical cues, such as mechanics, geometry (size), topography, and porosity, in the determination of cellular activities and fates, in addition to biochemical factors derived from their surroundings. In this review, we will first provide an overview of how such fundamental insights are identified by synchronizing the hierarchical nature of biological systems and static materials with tunable physical cues. Thereafter, we will explain the photoresponsive dynamic biomaterials to dissect the spatiotemporal aspects of the dependence of biological functions on physical cues.

Adaptive liquid interfaces induce neuronal differentiation of mesenchymal stem cells through lipid raft assembly

Stem cells and their microenvironment interact cooperatively to dictate their fates. Biomaterials are dynamically remodeled by stem cells, and stem cells sense and translate the changes into cell fate decisions. We have previously reported that adaptive biomaterials composed of fibronectin inserted into protein nanosheets at a liquid interface enhance neuronal differentiation of human mesenchymal stem cells (hMSCs). However, we could not decouple clearly the effect of ligand density from that of fibrillary structure on cellular function and fate. Here we present an adaptive biomaterial based on two-dimensional networks of protein nanofibrils at a liquid–liquid interface. Compared with flat protein nanosheets, this biomaterial enhances neuronal differentiation of hMSCs through a signaling mechanism involving focal adhesion kinase. Lipid raft microdomains in plasma membrane are found to play a central role in which hMSCs rapidly adapt to the dynamic microenvironment at the fluid interface. Our finding has substantial implications for regenerative medicine and tissue engineering.

In this work the authors report how human mesenchymal stem cells rapidly adapt to dynamic microenvironment through lipid raft in membrane microdomains that direct neurogenesis.

Precise Tuning and Characterization of Viscoelastic Interfaces for the Study of Early Epithelial-Mesenchymal Transition Behaviors

There is growing evidence that cellular functions are regulated by the viscoelastic nature of surrounding matrices. This study aimed to investigate the impact of interfacial viscoelasticity on adhesion and epithelial-mesenchymal transition (EMT) behaviors of epithelial cells. The interfacial viscoelasticity was manipulated using spin-coated thin films composed of copolymers of ε-caprolactone and d,l-lactide photo-cross-linked with benzophenone, whose mechanical properties were characterized using atomic force microscopy and a rheometer. The critical range for the morphological transition of epithelial Madin-Darby canine kidney (MDCK) cells was of the order of 10² ms relaxation time, which was 1-2 orders of magnitude smaller than the relaxation times reported (10-10² s). An analysis of strain rate-dependent viscoelastic properties revealed that the difference was caused by the different strain rate/frequency used for the mechanical characterization of the interface and bulk. Furthermore, decoupling of the interfacial viscous and elastic terms demonstrated that E/N-cadherin expression levels were regulated differently by interfacial relaxation and elasticity. These results confirm the significance of precise manipulation and characterization of interfacial viscoelasticity in mechanobiology studies on EMT progression.

Design of azobenzene-bearing hydrogel with photoswitchable mechanics driven by photo-induced phase transition for in vitro disease modeling

Mechanics of the extracellular matrix (ECM) exhibit changes during many biological events. During disease progression, such as cancer, matrix stiffening or softening occurs due to crosslinking of the collagen matrix or matrix degradation through cell-secreted enzymes. Engineered hydrogels have emerged as a prime in vitro model to mimic such dynamic mechanics during disease progression. Although there have been a variety of engineered hydrogels, few can offer both stiffening and softening properties under the same working principle. In addition, to model individual disease progression, it is desirable to control the kinetics of mechanical changes. To this end, we describe a photoresponsive hydrogel that undergoes stiffness changes by the photo-induced phase transition. The hydrogel was composed of a copolymer of azobenzene acrylate monomer (AzoAA) and N,N-dimethyl acrylamide (DMA). By tuning the amount of azobenzene, the phase transition behavior of this polymer occurs solely by light irradiation, because of the photoisomerization of azobenzene. This phase behavior was confirmed at 37 ^°C by turbidity measurements. In addition, the crosslinked poly(AzoAA-r-DMA) gel undergoes reversible swelling-deswelling upon photoisomerization by ultraviolet or visible light. Furthermore, the poly(AzoAA-r-DMA) sheet gels exhibited modulus changes at different isomerization states of azobenzene. When MCF-7 cells were cultured on the gels, stiffening at different timepoints induced varied responses in the gene expression levels of E-cadherin. Not only did this suggest an adaptive behavior of the cells against changes in mechanics during disease progression, this also demonstrated our material's potential towards in vitro disease modeling. STATEMENT OF SIGNIFICANCE: During disease progression such as cancer, cellular microenvironment called extracellular matrix (ECM) undergoes stiffness changes. Hydrogels, which are swollen network of crosslinked polymers, have been used to model such dynamic mechanical environment of the ECM. However, few could offer both stiffening and softening properties under the same working principle. Herein, we fabricated a novel photoresponsive hydrogel with switchable mechanics, activated by photo-induced structural change of the polymer chains within the hydrogel. When breast cancer cells were cultured on our dynamic hydrogels, gene expression and morphological observation suggested that cells react to changes in stiffness by a transient response, as opposed to a sustained one. The photoresponsive hydrogel offers possibility for use as a patient-specific model of diseases.

Epidermal Growth Factor-gold Nanoparticle Conjugates-induced Cellular Responses: Effect of Interfacial Parameters between Cell and Nanoparticle

The original activity of epidermal growth factor (EGF) is to promote cell growth or block their apoptosis. However, its activity changes to proapoptotic, completely opposite to the original one, upon conjugation to nanoparticles. We have recently identified that this unique activity conversion was mediated by the confinement of EGF receptor (EGFR) within membrane rafts and signal condensation therein. In this study, we investigated the effect of interfacial parameters between the EGF molecule immobilized at the nanoparticle surface and the cell-surface membrane receptors and analyzed how their interactions were transduced to downstream signaling leading to apoptotic responses. We also studied the cell-type selective apoptotic responses and compared them with EGFR expression level to demonstrate the potential of the nanoparticle conjugate as a new type of anti-cancer drug activating EGFR rather than conventional blocking approaches.

Viscoelastically tunable substrates elucidate the interface-relaxation-dependent adhesion and assembly behaviors of epithelial cells

Recent progress in mechanobiology sheds light on the regulation of cellular phenotypes by dissipative property of matrices, i.e., viscosity, fluidity, and stress relaxation, in addition to extensively studied elasticity. However, most researches have focused on bulk mechanics, despite cells in 2D culture can only interact with matrix interface directly. Here, we studied the impact of interfacial viscosity as well as elasticity of substrates on the early stage of adhesion behaviors of epithelial cells through new material design and mechanical characterization. The materials are copolymers of ε-caprolactone and d,l-lactide photocrosslinked by benzophenone. The substrate viscoelasticity changes depending on the polymer molecular weight and irradiation time. The interfacial elasticity and relaxation were determined by atomic force microscopy with modes of nanoindentation and tip-dwelling, respectively. MDCK cells changed morphologically, ranging from loose beaded assembly to more compact spheroids and eventual spread monolayer clusters, in response to the interfacial viscoelasticity change. Such morphological changes were mainly determined by substrate interfacial relaxation, rather than interfacial elasticity. Single-cell tracking identified biphasic motility with the minimum speed at intermediate relaxation time (~350 ms), where cells showed transitional morphologies between epithelial and mesenchymal traits. In that relaxation level, partially deformed cells moved around to coalesce with surrounding cells, eventually assembling into compact cellular aggregates. These results highlight, unlike the conventional hanging-drop technique, an appropriate level of interfacial relaxation is critical for efficient cell aggregate maturation on adhesive viscoelastic matrices. This work not only elucidates that the interfacial relaxation as the essential mechanical parameter for epithelial cell adhesion and migration, but also gives useful tips for creating physiologically relevant drug screening platform.

Improved anti-cancer effect of epidermal growth factor-gold nanoparticle conjugates by protein orientation through site-specific mutagenesis

Epidermal growth factor (EGF)-nanoparticle conjugates have the potential for cancer therapeutics due to the unique cytotoxic activity in cancer cells with EGF receptor (EGFR) overexpression. To gain its maximum activity, the EGF molecule should be immobilized on the nanoparticle surface in a defined orientation so as the bulky nanoparticle will not interfere EGF-EGFR interaction. Herein, we demonstrate successful enhancement of the anti-cancer activity of EGF-gold nanoparticle conjugates (EGF-GNPs) by controlling the EGF orientation on the surface of the nanoparticle through site-specific mutagenesis. Three lysine-free EGF variants (RR, RS, and SR) were designed, where two endogenous lysine residues were replaced with either arginine (R) or serine (S). The EGF mutants can be conjugated to the GNPs in a controlled orientation through the single amino group at the N-terminus. The ability of the mutants to induce extracellular signal-regulated kinase (ERK) phosphorylation was no different from wild type EGF (WT) in soluble form, rather lowered for one mutant (RR). However, after conjugated to GNPs, the SR mutants exhibited an enhanced biological activity than WT, in terms of ERK phosphorylation and growth inhibition of cancer cells. Further analysis of the binding constant of each mutant indicated the emergent enhanced activity of the GNP conjugates of the SR mutant was not solely contributed to the orientation, but to its higher binding activity to EGFR. These results validate the present genetic recombination strategy to improve the anticancer efficiency of EGF-GNPs.

A Facile Assay of Epithelial-mesenchymal Transition Based on Cooperativity Quantification of Cellular Autonomous Motions

Epithelial-mesenchymal transition (EMT), a qualitative change in cell migration behavior during cancer invasion and metastasis, is becoming a new target for anticancer drugs. Therefore, it is crucial to develop in vitro assays for the evaluation of the abilities of drug candidates to control EMT progression. We herein report on a method for the quantification of the EMT based on particle image velocimetry and correlation functions. The exponential fitting of the correlation curve gives an index (λ), which represents transforming growth factor (TGF)-β1-induced EMT progression and its suppression by inhibitors. Moreover, real-time monitoring of the λ value illustrates a time-dependent EMT progressing process, which occurs earlier than the bio-chemical changes in an EMT marker protein expression. The results demonstrate the usefulness of the present method for kinetic studies of EMT progression as well as EMT inhibitor screening.

Adaptive Liquid Interfacially Assembled Protein Nanosheets for Guiding Mesenchymal Stem Cell Fate

There is a growing interest in the development of dynamic adaptive biomaterials for regulation of cellular functions. However, existing materials are limited to two-state switching of the presentation and removal of cell-adhesive bioactive motifs that cannot emulate the native extracellular matrix (ECM) in vivo with continuously adjustable characteristics. Here, tunable adaptive materials composed of a protein monolayer assembled at a liquid-liquid interface are demonstrated, which adapt dynamically to cell traction forces. An ultrastructure transition from protein monolayer to hierarchical fiber occurs through interfacial jamming. Elongated fibronectin fibers promote formation of elongated focal adhesion structures, increase focal adhesion kinase activation, and enhance neuronal differentiation of stem cells. Cell traction force results in spatial rearrangement of ECM proteins, which feeds back to alter stem cell fate. The reported biomimetic adaptive liquid interface enables dynamic control of stem cell behavior and has potential translational applications.

Dentin phosphoprotein inhibits lipopolysaccharide-induced macrophage activation independent of its serine/aspartic acid-rich repeats

OBJECTIVE

The objective of this study was to investigate the effects of dentin phosphoprotein (DPP) on lipopolysaccharide-induced inflammatory responses of macrophages in vitro.

DESIGN

Wildtype and mutant recombinant dentin phosphoprotein (rDPP) proteins were generated using a mammalian expression system. Macrophages, phorbol 12-myristate 13-acetate-differentiated THP-1 cells, were stimulated with lipopolysaccharide in the absence or presence of rDPP proteins. After the 24-hr incubation, the inflammatory gene expression levels were examined by quantitative reverse-transcription polymerase chain reaction and the amount of secreted TNF-α protein was evaluated by enzyme-linked immunosorbent assay. Furthermore, the subcellular localization of exogenously added rDPP was examined by immunocytochemistry, and the direct binding of rDPP to lipopolysaccharide was quantified by solid-phase binding assay.

RESULTS

rDPP dose-dependently reduced the expression of lipopolysaccharide-induced inflammatory genes, such as TNFα, IL-1β, and IL-8, and TNF-α protein secretion from the macrophages. Furthermore, mutant rDPP having a shortened serine/aspartic acid-rich repeats (SDrr) was also able to inhibit lipopolysaccharide-induced inflammatory responses of macrophages. rDPP was localized adjacent to the cellular membrane rather than in the cytoplasm, and rDPP was able to bind to lipopolysaccharide. These results suggested that rDPP inhibited lipopolysaccharide-induced inflammatory responses by binding to lipopolysaccharide.

CONCLUSIONS

In addition to the well-known functions of DPP for dentin mineralization that depend on the SDrr, we demonstrated that DPP possesses anti-inflammatory effects on lipopolysaccharide-stimulated macrophages that are independent of the SDrr.

Nanaomycin K, a new epithelial-mesenchymal transition inhibitor produced by the actinomycete "Streptomyces rosa subsp. notoensis" OS-3966

A new nanaomycin analog, nanaomycin K, was isolated from a cultured broth of actinomycete strain "Streptomyces rosa subsp. notoensis" OS-3966. Nuclear magnetic resonance (NMR) analyses revealed that the planar structure of nanaomycin K had an ergothioneine moiety. To determine the absolute configuration, nanaomycin K was semisynthesized using standards of nanaomycin E and l-ergothioneine. The natural and semisynthetic nanaomycin K were identified as the same compounds based on retention time, mass spectrometry, ¹H NMR, and optical rotation data. Nanaomycin K showed cytotoxicity against Madin-Darby canine kidney (MDCK) cells undergoing transforming growth factor (TGF) β1-induced epithelial-mesenchymal transition.

Synthesis of Poly(N-vinylpyrrolidone)-Based Polymer Bottlebrushes by ATRPA and RAFT Polymerization: Toward Drug Delivery Application

Atom transfer radical polyaddition (ATRPA) was utilized herein to synthesize a specific functional polyester. We conducted ATRPA of 4-vinylbenzyl 2-bromo-2-phenylacetate (VBBPA) inimer and successfully obtained a linear type poly(VBBPA) (PVBBPA) polyester with benzylic bromides along the backbone. To obtain a novel amphiphilic polymer bottlebrush, however, the lateral ATRP chain extension of PVBBPA with N-vinyl pyrrolidone (NVP) met the problem of quantitative dimerization. By replacing the bromides to xanthate moieties efficiently, we thus observed a pseudo linear first order reversible addition-fragmentation chain transfer (RAFT) polymerization to obtain novel poly(4-vinylbenzyl-2-phenylacetate)-g-poly(NVP) (PVBPA-g-PNVP) amphiphilic polymer bottlebrushes. The critical micelle concentration (CMC) and particle size of the amphiphilic polymer bottlebrushes were characterized by fluorescence spectroscopy, dynamic light scattering (DLS), and scanning electron microscopy (SEM) (CMCs < 0.5 mg/mL; particle sizes = ca. 100 nm). Toward drug delivery application, we examined release profiles using a model drug of Nile red at different pH environments (3, 5, and 7). Eventually, low cytotoxicity and well cell uptake of the Madin-Darby Canine Kidney Epithelial (MDCK) for the polymer bottlebrush micelles were demonstrated.

Photoactivatable Hydrogel Interfaces for Resolving the Interplay of Chemical, Mechanical, and Geometrical Regulation of Collective Cell Migration

Collective migration is the mechanobiological interplay within migrating cell clusters and against extracellular matrixes (ECMs) underneath, mediating various physiological and pathological processes. Therefore, it is crucial to develop a robust platform on which collective migration can be studied under standardized conditions to understand how cells migrate differently between normal and disease states. We herein demonstrated phtotoactivatable hydrogel interfaces as suitable candidates for such applications. The substrate was composed of a poly(acrylamide) (PAAm) hydrogel whose surface was sequentially functionalized with poly-d-lysine (PDL) and photocleavable poly(ethylene glycol) (PEG). On the surface of the gel substrates, cell clusters with any given geometries can be prepared by controlling the irradiation patterns (geometrical cue), and their collective migration can be induced by the subsequent irradiation of the surrounding regions. Moreover, the substrate mechanical properties can be controlled by changing the composition of the PAAm hydrogel (mechanical cue), and the chemical properties were controlled by changing the amount of immobilized PDL, thereby altering the adsorbed amount of ECM proteins (chemical cue). The photoactivatable gel substrates were characterized by fluorescence microscopy, ζ-potential measurements, and the protein adsorption test. Through the study of the interplay of chemical, mechanical, and geometrical cues in the regulation of collective characteristics, we found additive effects of chemical and mechanical cues on the suppression of circular expansion by up-regulating the epithelial morphology. Also, the impact of geometrical cues became more significant by decreasing the chemical cue. We believe the present platform will be a useful research tool for the comprehensive mechanobiological analysis of collective cell migration.

Heparin-LL37 complexes are less cytotoxic for human dental pulp cells and have undiminished antimicrobial and LPS-neutralizing abilities

AIM

To investigate whether glycosaminoglycans (GAGs) binding to high-dose LL37 eliminates its cytotoxicity to dental pulp cells (hDPCs) whilst retaining undiminished antimicrobial and LPS-neutralizing abilities.

METHODOLOGY

hDPCs were stimulated with varying concentrations of LL37, and their cell viability was analysed by MTT. Then, high-dose LL37 (10 μmol L^-1 ) was bound to varying concentrations of three GAGs, heparin, chondroitin sulphate and hyaluronic acid, and their cytotoxic effects on hDPCs and antimicrobial effects were evaluated and compared. Furthermore, the LPS-neutralizing ability of heparin (5 μg mL^-1 )-LL37 (10 μmol L^-1 ) complexes, which were found to be less cytotoxic for hDPCs with undiminished antimicrobial ability, was investigated. Statistical analysis was performed using one-way analysis of variance (anova), followed by Dunnett's test. P values below 0.05 were considered significant.

RESULTS

LL37 significantly reduced the cell viability of hDPCs in a dose-dependent manner (P < 0.01). LL37 (10 μmol L^-1 ) binding to heparin within a limited concentration range (2~6 μg mL^-1 ) eliminated the cytotoxicity for hDPCs (P < 0.01) whilst exerting potent antimicrobial effects against Streptococcus mutans, Streptococcus sobrinus, Streptococcus salivarius, Aggegatibacter actinomycetemcomitans and Escherichia coli. LL37 (10 μmol L^-1 ) binding to chondroitin sulphate exhibited similar functions (P < 0.01); however, the effective chondroitin sulphate concentration was highly restricted (3 μg mL^-1 ). LL37 (10 μmol L^-1 ) binding to hyaluronic acid was unable to abrogate the cytotoxicity of LL37 even at higher concentrations (10 and 100 μg mL^-1 ). Moreover, exogenous addition of LPS dose-dependently reduced the amount of LL37 precipitated with the heparin-LL37 agarose beads (P < 0.01), and the released LL37 simultaneously neutralized the pro-inflammatory ability of LPS in macrophages (P < 0.01).

CONCLUSIONS

Heparin-LL37 complexes generated at suitable concentration ratios are easy to make, are less cytotoxic and are broad-range antimicrobial materials that can neutralize LPS by providing LL37 in accordance with the amount of free LPS. They may be a potential treatment to save dental pulp tissue from the acute inflammation exacerbated by invading bacteria and the LPS they release.

Modulation of Mesenchymal Stem Cells Mechanosensing at Fluid Interfaces by Tailored Self-Assembled Protein Monolayers

Mechanical cues of cellular microenvironments can modulate cell functions including cell spreading and differentiation. Most studies of cellular functions are performed using a solid substrate, and it is thought that cells cannot spread on fluid substrates because of rapid relaxation, which cannot resist against actomyosin-based cell contractility. Here, the spreading and growth of anchorage-dependent cells such as human mesenchymal stem cells at the liquid interface between a perfluorocarbon fluid and the culture medium are observed. It is demonstrated that a monomolecular protein nanosheet self-assembled at a fluid interface is sufficiently rigid to support cell spreading without additional treatment. Fine tuning of the packing of these proteins at the liquid interface permits tailoring of the mechanics of the protein layer, ultimately allowing for the regulation of cell spreading. The greater stiffness of the protein nanosheets triggers cell spreading, adhesion growth, and yes-associated protein nuclear translocation. Cell behavior at the fluid interface is explained within the framework of the molecular clutch model. In addition, the freestanding ultrathin protein nanosheets are extremely flexible, easily deformed, and perceived by cells as being much softer. The findings are expected to provide a new perspective for insights into cell-material interactions.

Nanaomycin I and J: New nanaomycins generated by mycothiol-mediated compounds from "Streptomyces rosa subsp. notoensis" OS-3966

Two new nanaomycin analogs, nanaomycin I and J, were isolated from a cultured broth of an actinomycete strain, "Streptomyces rosa subsp. notoensis" OS-3966. In our previous study, we have confirmed the occurrence of nanaomycin I (m/z = 482 [M + H]⁺) that lacks a pseudo-disaccharide from the mycothiol of nanaomycin H under same culture condition. In this study, to confirm the structure of nanaomycin I, the strain "S. rosa subsp. notoensis" OS-3966 was re-cultured and the target compound with m/z = 482 [M + H]⁺ was isolated. Furthermore, we discovered another new analog, designated as nanaomycin J in isolating nanaomycin I. The NMR analyses revealed that the structures of nanaomycin I and J are N-acetylcysteine S-conjugates without a pseudo-disaccharide and N-acetylcysteine S-conjugates without a myo-inositol of nanaomycin H, respectively. The relative configurations of the tetrahydropyrane moiety of nanaomycin I and J were determined by rotating-frame overhauser effect spectroscopy (ROESY) analysis. Absolute configurations of the N-acetylcysteine moiety of nanaomycin I and J were determined by advanced Marfey's analyses for acid hydrolysis of de-sulfurized nanaomycin I and J with Raney nickel. Nanaomycin I and J showed moderate cytotoxicity against several human tumor cell lines.

An Application of Photoactivatable Substrate for the Evaluation of Epithelial-mesenchymal Transition Inhibitors

Epithelial-mesenchymal transition (EMT), phenotypic changes in cell adhesion and migration, is involved in cancer invasion and metastasis, hence becoming a target for anti-cancer drugs. In this study, we report a method for the evaluation of EMT inhibitors by using a photoactivatable gold substrate, which changes from non-cell-adhesive to cell-adhesive in response to light. The method is based on the geometrical confinement of cell clusters and the subsequent migration induction by controlled photoirradiation of the substrate. As a proof-of-concept experiment, a known EMT inhibitor was successfully evaluated in terms of the changes in cluster area or leader cell appearance, in response to biochemically and mechanically induced EMT. Furthermore, an application of the present method for microbial secondary metabolites identified nanaomycin H as an EMT inhibitor, potentially killing EMTed cells in disseminated conditions. These results demonstrate the potential of the present method for screening new EMT inhibitors.

Genome-wide identification of chromatin-enriched RNA reveals that unspliced dentin matrix protein-1 mRNA regulates cell proliferation in squamous cell carcinoma

Chromatin-enriched noncoding RNAs (ncRNAs) have emerged as key molecules in epigenetic processes by interacting with chromatin-associated proteins. Recently, protein-coding mRNA genes have been reported to be chromatin-tethered, similar with ncRNA. However, very little is known about whether chromatin-enriched mRNA is involved in the chromatin modification process. Here, we comprehensively examined chromatin-enriched RNA in squamous cell carcinoma (SQCC) cells by RNA subcellular localization analysis, which was a combination of RNA fractionation and RNA-seq. We identified 11 mRNAs as highly chromatin-enriched RNAs. Among these, we focused on the dentin matrix protein-1 (DMP-1) gene because its expression in SQCC cells has not been reported. Furthermore, we clarified that DMP-1 mRNA was retained in chromatin in its unspliced form in SQCC in vitro and in vivo. As the inhibition of the unspliced DMP-1 mRNA (unspDMP-1) expression resulted in decreased cellular proliferation in SQCC cells, we performed ChIP-qPCR to identify cell cycle-related genes whose expression was epigenetically modified by unspDMP-1, and found that the CDKN1B promoter became active in SQCC cells by inhibiting unspDMP-1 expression. This result was further validated by the increased CDKN1B gene expression in the cells treated with siRNA for unspDMP-1 and by restoration of the decreased cellular proliferation rate by simultaneously inhibiting CDKN1B expression in SQCC cells. Further, to examine whether unspDMP-1 was able to associate with the CDKN1B promoter region, SQCC cells stably expressing PP7-mCherry fusion protein were transiently transfected with the unspDMP-1 fused to 24 repeats of the PP7 RNA stem loop (unspDMP-1-24xPP7) and we found that unspDMP-1-24xPP7 was efficiently precipitated with the antibody against mCherry and was significantly enriched in the CDKN1B promoter region. Thus, unspDMP-1 is a novel chromatin-enriched RNA that epigenetically regulates cellular proliferation of SQCC.

Suppression of Myogenic Differentiation of Mammalian Cells Caused by Fluidity of a Liquid-Liquid Interface

There is growing evidence to suggest that the prevailing physical microenvironment and mechanical stress regulate cellular functions, including adhesion, proliferation, and differentiation. Moreover, the physical microenvironment determines the stem-cell lineage depending on stiffness of the substrate relative to biological tissues as well as the stress relaxation properties of the viscoelastic substrates used for cell culture. However, there is little known regarding the biological effects of a fluid substrate, where viscoelastic stress is essentially absent. Here, we demonstrate the regulation of myogenic differentiation on fluid substrates by using a liquid-liquid interface as a scaffold. C2C12 myoblast cells were cultured using water-perfluorocarbon (PFC) interfaces as the fluid microenvironment. We found that, for controlled in vitro culture at water-PFC interfaces, expression of myogenin, myogenic regulatory factors (MRF) family gene, is remarkably attenuated even when myogenic differentiation was induced by reducing levels of growth factors, although MyoD was expressed at the usual level (MyoD up-regulates myogenin under an elastic and/or viscoelastic environment). These results strongly suggest that this unique regulation of myogenic differentiation can be attributed to the fluid microenvironment of the interfacial culture medium. This interfacial culture system represents a powerful tool for investigation of the mechanisms by which physical properties regulate cellular adhesion and proliferation as well as their differentiation. Furthermore, we successfully transferred the cells cultured at such interfaces using Langmuir-Blodgett (LB) techniques. The combination of the interfacial culture system with the LB approach enables investigation of the effects of mechanical compression on cell functions.

Estradiol-tethered micropatterned surfaces for the study of estrogenic non-genomic pathways

Besides its well-known hormonal effects initiated in the nucleus, estradiol (E2) also activates non-nuclear pathways through interactions with receptors located on the cell plasma membrane. Micropatterned substrates consisting of gold dots bearing tethered E2 distributed on a cell-adhesive substrate were prepared and shown to trigger specifically E2 non-genomic effects in cells grown on the substrates.

Reduced adhesive ligand density in engineered extracellular matrices induces an epithelial-mesenchymal-like transition

A synergistic effect of biochemical and mechanical cues emanating from the extracellular matrix (ECM) on inducing malignant transformation of epithelial cells has been observed recently. However, the effect of quantitative changes in biochemical stimuli on cell phenotype, without changes in ECM component and rigidity, remains unknown. To determine this effect, we grew Madin-Darby canine kidney epithelial cells (MDCK) on gold surfaces immobilized with varying densities of cyclic arginine-glycine-aspartate (cRGD) peptide and analyzed cell morphology, cell migration, cytoskeletal organization, and protein expression. Cells grown on a surface presenting a higher density of cRGD displayed an epithelial morphology and grew in clusters, while those grown on a diluted cRGD surface transformed into an elongated, fibroblast-like form with extensive scattering. Time-lapse imaging of cell clusters grown on the concentrated cRGD surface revealed collective migration with intact cell-cell contacts accompanied by the development of cortical actin. In contrast, cells migrated individually and formed stress fibers on the substrate with sparse cRGD. These data point towards transdifferentiation of epithelial cells to mesenchymal-like cells when plated on a diluted cRGD surface. Supporting this hypothesis, immunofluorescence microscopy and western blot analysis revealed increased membrane localization and total expression of N-cadherin and vimentin in cells undergoing mesenchymal-like transition. Taken together, these results suggest a possible role of decreased biochemical stimuli from the ECM in regulating epithelial phenotype switching.

STATEMENT OF SIGNIFICANCE

Epithelial-mesenchymal transition (EMT) is a process where adherent epithelial cells convert into individual migratory mesenchymal phenotype. It plays an important role both in physiological and pathological processes. Recent studies demonstrate that the program is not only governed by soluble factors and gene expressions, but also modulated by biochemical and mechanical cues in ECMs. In this study, we developed chemically defined surfaces presenting controlled ECM ligand densities and studied their impact on the EMT progression. Morphological and biochemical analyses of epithelial cells cultured on the surfaces indicate the cells undergo an EMT-like transition on the diluted cRGD surface while retaining epithelial characteristics on the cRGD-rich substrate, suggesting an important role of the ECM ligand density in epithelial phenotype switching.

Dynamic control of cell adhesion on a stiffness-tunable substrate for analyzing the mechanobiology of collective cell migration

A photoactivatable gel substrate with defined mechanical properties was developed to study the mechanobiology of collective cell migration.

Facile preparation of a photoactivatable surface on a 96-well plate: a versatile and multiplex cell migration assay platform

A novel photoactivatable 96-well plate based on photocleavable PEG and poly-d-lysine serves as a useful high-throughput cell migration assay platform.

Colorimetric microchip assay using our own whole blood collected by a painless needle for home medical care

We have developed a colorimetric measurement chip that measures triglycerides, total cholesterol, and high-density lipoprotein in 6 μL of whole blood collected with a painless needle. The chip can be used by patients to self-monitor certain health conditions at home. This chip contains a sharp 150 μm diameter stainless steel (SUS) needle that collects blood painlessly. The chip consists of three layers of injection-molded poly(methyl methacrylate) bonded together with two double-sided tapes. Two commercial reagents are used, and the volume ratio of plasma to reagent is doubled from the reagent specification to reduce the optical absorption length (and chip mass) by half. Centrifugal force separates the plasma from the blood, and then weighs out and mixes the plasma and reagents. A zigzag channel allows mixing of the plasma with the reagents mainly by vortex motion due to the centrifugal force generated at the corners of the channel. The measured values correlated well with conventionally tested values.

Hippo pathway effectors control cardiac progenitor cell fate by acting as dynamic sensors of substrate mechanics and nanostructure

Stem cell responsiveness to extracellular matrix (ECM) composition and mechanical cues has been the subject of a number of investigations so far, yet the molecular mechanisms underlying stem cell mechano-biology still need full clarification. Here we demonstrate that the paralog proteins YAP and TAZ exert a crucial role in adult cardiac progenitor cell mechano-sensing and fate decision. Cardiac progenitors respond to dynamic modifications in substrate rigidity and nanopattern by promptly changing YAP/TAZ intracellular localization. We identify a novel activity of YAP and TAZ in the regulation of tubulogenesis in 3D environments and highlight a role for YAP/TAZ in cardiac progenitor proliferation and differentiation. Furthermore, we show that YAP/TAZ expression is triggered in the heart cells located at the infarct border zone. Our results suggest a fundamental role for the YAP/TAZ axis in the response of resident progenitor cells to the modifications in microenvironment nanostructure and mechanics, thereby contributing to the maintenance of myocardial homeostasis in the adult heart. These proteins are indicated as potential targets to control cardiac progenitor cell fate by materials design.