Influence of Cell Morphology on Mesenchymal Stem Cell Transfection

Biofunctionalized patterned platform as microarray biochip to supervise delivery and expression of pDNA nanolipoplexes in stem cells via mechanotransduction

Biochips are widely applied to manipulate the geometrical morphology of stem cells in recent years. Patterned antenna-like pseudopodia are also probed to explore the influence of pseudopodia formation on gene delivery and expression on biochips. However, how the antenna-like pseudopodia affect gene transfection is unsettled and the underlying trafficking mechanism of exogenous genes in engineered single cells is not announced. Therefore, the engineered microarray biochips were conceptualized and prepared by the synthesized photointelligent biopolymer to precisely manage geometric topological structures (cell size and antenna-like protrusion) of stem cells on biochips. The cytoskeleton could be regulated in engineered cells and large cells with more antennas assembled well-organized actin filaments to affect cell tension distribution. The stiffness and adhesion force were measured by atomic force microscope to reveal cell nanomechanics on microarray biochips. Cytoskeleton-mediated nanomechanics could be adjusted by actin filaments. Gene transfection efficiency was enhanced with increasing cell nanomechanics, which was also confirmed by the evaluation of cell internalization capacity of nanoparticles and DNA synthesis ability. This work will provide a new strategy to study functional biomaterials, microarray chips and internal mechanism of gene transfection in patterned stem cells on biochips.

Noninvasive Assessment of hiPSC Differentiation toward Cardiomyocytes Using Pretrained Convolutional Neural Networks and the Channel Pruning Algorithm

Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs) offer versatile applications in tissue engineering and drug screening. To facilitate the monitoring of hiPSC cardiac differentiation, a noninvasive approach using convolutional neural networks (CNNs) was explored. HiPSCs were differentiated into cardiomyocytes and analyzed using the quantitative real-time polymerase chain reaction (qRT-PCR). The bright-field images of the cells at different time points were captured to create the dataset. Six pretrained models (AlexNet, GoogleNet, ResNet 18, ResNet 50, DenseNet 121, VGG 19-BN) were employed to identify different stages in differentiation. VGG 19-BN outperformed the other five CNNs and exhibited remarkable performance with 99.2% accuracy, recall, precision, and F1 score and 99.8% specificity. The pruning process was then applied to the optimal model, resulting in a significant reduction of model parameters while maintaining high accuracy. Finally, an automation application using the pruned VGG 19-BN model was developed, facilitating users in assessing the cell status during the myocardial differentiation of hiPSCs.

Revelation of adhesive proteins affecting cellular contractility through reference-free traction force microscopy

Over the past few decades, the critical role played by cellular contractility associated mechanotransduction in the regulation of cell functions has been revealed. In this case, numerous biomaterials have been chemically or structurally designed to manipulate cell behaviors through the regulation of cellular contractility. In particular, adhesive proteins including fibronectin, poly-L-lysine and collagen type I have been widely applied in various biomaterials to improve cell adhesion. Therefore, clarifying the effects of adhesive proteins on cellular contractility has been valuable for the development of biomaterial design. In this study, reference-free traction force microscopy with a well-organized microdot array was designed and prepared to investigate the relationship between adhesive proteins, cellular contractility, and mechanotransduction. The results showed that fibronectin and collagen type I were able to promote the assembly of focal adhesions and further enhance cellular contraction and YAP activity. In contrast, although poly-L-lysine supported cell spreading and elongation, it was inefficient at inducing cell contractility and activating YAP. Additionally, compared with cellular morphogenesis, cellular contraction was essential for YAP activation.

Stem cell-based ischemic stroke therapy: Novel modifications and clinical challenges

Ischemic stroke (IS) causes severe disability and high mortality worldwide. Stem cell (SC) therapy exhibits unique therapeutic potential for IS that differs from current treatments. SC's cell homing, differentiation and paracrine abilities give hope for neuroprotection. Recent studies on SC modification have enhanced therapeutic effects for IS, including gene transfection, nanoparticle modification, biomaterial modification and pretreatment. These methods improve survival rate, homing, neural differentiation, and paracrine abilities in ischemic areas. However, many problems must be resolved before SC therapy can be clinically applied. These issues include production quality and quantity, stability during transportation and storage, as well as usage regulations. Herein, we reviewed the brief pathogenesis of IS, the "multi-mechanism" advantages of SCs for treating IS, various SC modification methods, and SC therapy challenges. We aim to uncover the potential and overcome the challenges of using SCs for treating IS and convey innovative ideas for modifying SCs.

Fibrous topology promoted pBMP2-activated matrix on titanium implants boost osseointegration

Titanium (Ti) implants have been extensively used after surgical operations. Its surface bioactivity is of importance to facilitate integration with surrounding bone tissue, and ultimately ensure stability and long-term functionality of the implant. The plasmid DNA-activated matrix (DAM) coating on the surface could benefit osseointegration but is still trapped by poor transfection for further application, especially on the bone marrow mesenchymal stem cells (BMSCs) in vivo practical conditions. Herein, we constructed a DAM on the surface of fibrous-grained titanium (FG Ti) composed of phase-transition lysozyme (P) as adhesive, cationic arginine-rich lipid (RLS) as the transfection agent and plasmid DNA (pDNA) for bone morphology protein 2 (BMP2) expression. The cationic lipid RLS improved up to 30-fold higher transfection than that of commercial reagents (Lipofectamine 2000 and polyethyleneimine) on MSC. And importantly, Ti surface topology not only promotes the DAM to achieve high transfection efficiency (∼75.7% positive cells) on MSC due to the favorable combination but also reserves its contact induction effect for osteoblasts. Upon further exploration, the fibrous topology on FG Ti could boost pDNA uptake for gene transfection, and cell migration in MSC through cytoskeleton remodeling and induce contact guidance for enhanced osteointegration. At the same time, the cationic RLS together with adhesive P were both antibacterial, showing up to 90% inhibition rate against Escherichia coli and Staphylococcus aureus with reduced adherent microorganisms and disrupted bacteria. Finally, the FG Ti-P/pBMP2 implant achieved accelerated bone healing capacities through highly efficient gene delivery, aligned surface topological structure and increased antimicrobial properties in a rat femoral condylar defect model.

Hs27 fibroblast response to contact guidance cues

Contact guidance is the phenomena of how cells respond to the topography of their external environment. The morphological and dynamic cell responses are strongly influenced by topographic features such as lateral and vertical dimensions, namely, ridge and groove widths and groove depth ([Formula: see text], respectively). However, experimental studies that independently quantify the effect of the individual dimensions as well as their coupling on cellular function are still limited. In this work, we perform extensive parametric studies in the dimensional space-well beyond the previously studied range in the literature-to explore topographical effects on morphology and migration of Hs27 fibroblasts via static and dynamic analyses of live cell images. Our static analysis reveals that the [Formula: see text] is most significant, followed by the [Formula: see text]. The fibroblasts appear to be more elongated and aligned in the groove direction as the [Formula: see text] increases, but their trend changes after 725 nm. Interestingly, the cell shape and alignment show a very strong correlation regardless of [Formula: see text]. Our dynamic analysis confirms that directional cell migration is also strongly influenced by the [Formula: see text], while the effect of the [Formula: see text] and [Formula: see text] is statistically insignificant. Directional cell migration, as observed in the static cell behavior, shows the statistically significant transition when the [Formula: see text] is 725 nm, showing the intimate links between cell morphology and migration. We propose possible scenarios to offer mechanistic explanations of the observed cell behavior.

Dynamic Stiffening Hydrogel with Instructive Stiffening Timing Modulates Stem Cell Fate In Vitro and Enhances Bone Remodeling In Vivo

Biomechanical stimuli derived from the extracellular matrix (ECM) extremely tune stem cell fate through 3D and spatiotemporal changes in vivo. The matrix stiffness is a crucial factor during bone tissue development. However, most in vitro models to study the osteogenesis of mesenchymal stem cells (MSCs) are static or stiffening in a 2D environment. Here, a dynamic and controllable stiffening 3D biomimetic model is created to regulate the osteogenic differentiation of MSCs with a dual-functional gelatin macromer that can generate a double-network hydrogel by sequential enzymatic and light-triggered crosslinking reactions. The findings show that these dynamic hydrogels allowed cells to spread and expand prior to the secondary crosslinking and to sense high stiffness after stiffening. The MSCs in the dynamic hydrogels, especially the hydrogel stiffened at the late period, present significantly elevated osteogenic ECM secretion, gene expression, and nuclear localization of Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). In vivo evaluation of animal experiments further indicates that the enhancement of dynamic stiffening on osteogenesis of MSCs substantially promotes bone remodeling. Consequently, this work reveals that the 3D dynamic stiffening microenvironment as a critical biophysical cue not only mediates the stem cell fate in vitro, but also augments bone restoration in vivo.

Protective effect of curcumin on hepatolenticular degeneration through copper excretion and inhibition of ferroptosis

BACKGROUND

Hepatolenticular degeneration (HLD) is an autosomal recessive disorder concerning copper metabolism. Copper overload is also accompanied by iron overload in HLD patients, which can lead to ferroptosis. Curcumin, the active component in turmeric, has the potential to inhibit ferroptosis.

PURPOSE

The current study proposed a systematic investigation of the protective effects of curcumin against HLD and the underlying mechanisms.

METHODS

The protective effect of curcumin on toxic milk (TX) mice was studied. Liver tissue was observed via hematoxylin-eosin (H&E) staining and the ultrastructure of the liver tissue was observed through transmission electron microscopy. Copper levels in the tissues, serum, and metabolites were measured by atomic absorption spectrometry (AAS). In addition, serum and liver indicators were evaluated. In cellular experiments, the effect of curcumin on the viability of rat normal liver cells (BRL-3A) was determined via the 3-[4,5-dimethylthiazol-2-yl)]-2,5-diphenyltetrazolium bromide (MTT) assay. Cell and mitochondrial morphology were observed in curcumin-mediated HLD model cells. The intracellular copper ion fluorescence intensity was observed via fluorescence microscopy, and intracellular copper iron content was detected using AAS. Further, oxidative stress indicators were evaluated. Cellular reactive oxygen species (ROS) and cellular mitochondrial membrane potential were examined via flow cytometry. Furthermore, the expression levels of nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and glutathione peroxidase 4 (GPX4) were determined via western blotting (WB).

RESULTS

The histopathology of the liver confirmed the hepatoprotective effects of curcumin. Curcumin improved copper metabolism in TX mice. Both serum liver enzyme markers and antioxidant enzyme levels indicated the protective effect of curcumin against HLD-related liver injury. The MTT assay results showed that curcumin was protective against excess copper-induced injury. Curcumin improved the morphology of HLD model cells and their mitochondrial morphology. The Cu²⁺ fluorescent probe and the AAS results indicated that curcumin reduced Cu²⁺ content in HLD hepatocytes. In addition, curcumin improved oxidative stress levels and prevented the decline of mitochondrial membrane potential in HLD model cells. The ferroptosis inducer Erastin reversed these effects of curcumin. WB revealed that curcumin promoted Nrf2, HO-1, and GPX4 protein expression in HLD model cells, and the Nrf2 inhibitor ML385 reversed the effects of curcumin.

CONCLUSION

Curcumin demonstrates a protective role by expelling copper and inhibiting ferroptosis, activating the Nrf2/HO-1/GPX4 signaling pathway in HLD.

Regulation of micropatterned curvature-dependent FA heterogeneity on cytoskeleton tension and nuclear DNA synthesis of malignant breast cancer cells

Breast cancer is considered as a worldwide disease due to its high incidence and malignant metastasis. Although numerous techniques have been developed well to conduct breast cancer therapy, the influence of micropattern-induced interfacial heterogeneity on the molecular mechanism and nuclear signalling transduction of carcinogenesis is rarely announced. In this study, PDMS stencil-assisted micropatterns were fabricated on tissue culture plates to manage cell clustering colony by adjusting initial cell seeding density and the size of microholes. The curvature of each microholes was controlled to construct the interfacial heterogeneity of MDA-MB231 cancer cells at the periphery of micropatterned colony. The distinguished focal adhesion (FA) and cytoskeleton distribution at the central and peripheral regions of the cell colony were regulated by heterogeneous properties. The interfacial heterogeneity of FA and cytoskeleton would induce the biased tension force to encourage more ezrin expression at the periphery and further promote DNA synthesis, therefore disclosing a stem-like phenotype in heterogeneous cells. This study will provide a value source of information for the development of micropattern-induced heterogeneity and the interpretation of metastatic mechanism in malignant breast cancer cells.

Innovative nonviral gene delivery strategies for engineering human mesenchymal stem cell phenotypes toward clinical applications

Although human mesenchymal stem cells (hMSCs) have been used in many clinical trials, variable outcomes have resulted in no FDA-approved hMSC treatment. However, research into developing hMSC therapies for many diseases continues. An approach to manipulate hMSCs for therapeutic applications is gene delivery. Nonviral gene delivery is safer and more flexible than viral vectors, but much less efficient, especially in hMSCs. It is not understood why hMSCs are more difficult to transfect than cell lines, but innate features of hMSCs may present unique barriers to transfection. Recently, strategies to improve hMSC transfection have been developed by innovating nanocarriers, nucleic acid cargos, and by 'priming' hMSCs chemically and physically for more efficient transfection. These strategies aim to engineer hMSCs with new phenotypes mediated by transgenic secreted factors, receptors, transcription factors, and genome editing systems for clinical applications requiring enhanced immunomodulation and/or tissue regeneration, or for functions such as tumor-killing and tissue engineering.

Cellular nanomechanics derived from pattern-dependent focal adhesion and cytoskeleton to balance gene transfection of malignant osteosarcoma

Gene transfection was supposed to be the most promising technology to overcome the vast majority of diseases and it has been popularly reported in clinical applications of gene therapy. In spite of the rapid development of novel transfection materials and methods, the influence of morphology-dependent nanomechanics of malignant osteosarcoma on gene transfection is still unsettled. In this study, cell spreading and adhesion area was adjusted by the prepared micropatterns to regulate focal adhesion (FA) formation and cytoskeletal organization in osteosarcoma cells. The micropattern-dependent FA and cytoskeleton could induce different cellular nanomechanics to affect cell functions. Our results indicated that transfection efficiency was improved with enlarging FA area and cell nanomechanics in micropatterned osteosarcoma. The difference of gene transfection in micropatterned cells was vigorously supported by cellular internalization capacity, Ki67 proliferation ability and YAP mechanotranduction through the regulation of focal adhesion and cytoskeletal mechanics. This study is an attempt to disclose the relationship of cell nanomechanics and gene transfection for efficient gene delivery and develop multifunctional nanomedicine biomaterials for accurate gene therapy in osteosarcoma cells.

Promotion of Melanoma Cell Proliferation by Cyclic Straining through Regulatory Morphogenesis

The genotype and phenotype of acral melanoma are obviously different from UV-radiation-induced melanoma. Based on the clinical data, mechanical stimulation is believed to be a potential cause of acral melanoma. In this case, it is desirable to clarify the role of mechanical stimulation in the progression of acral melanoma. However, the pathological process of cyclic straining that stimulates acral melanoma is still unclear. In this study, the influence of cyclic straining on melanoma cell proliferation was analyzed by using a specifically designed cell culture system. In the results, cyclic straining could promote melanoma cell proliferation but was inefficient after the disruption of cytoskeleton organization. Therefore, the mechanotransduction mechanism of promoted proliferation was explored. Both myosin and actin polymerization were demonstrated to be related to cyclic straining and further influenced the morphogenesis of melanoma cells. Additionally, the activation of mechanosensing transcription factor YAP was related to regulatory morphogenesis. Furthermore, expression levels of melanoma-involved genes were regulated by cyclic straining and, finally, accelerated DNA synthesis. The results of this study will provide supplementary information for the understanding of acral melanoma.

Influence of Colonies’ Morphological Cues on Cellular Uptake Capacity of Nanoparticles

High transmembrane delivery efficiency of nanoparticles has attracted substantial interest for biomedical applications. It has been proved that the desired physicochemical properties of nanoparticles were efficient for obtaining a high cellular uptake capacity. On the other hand, biophysical stimuli from in situ microenvironment were also indicated as another essential factor in the regulation of cellular uptake capacity. Unfortunately, the influence of colony morphology on cellular uptake capacity was rarely analyzed. In this study, micropatterned PDMS stencils containing circular holes of 800/1,200 μm in diameter were applied to control colonies’ size. The amino-modified nanoparticles were cocultured with micropatterned colonies to analyze the influence of colonies’ morphology on the cellular uptake capacity of nanoparticles. Consequently, more endocytosed nanoparticles in larger colonies were related with a bigger dose of nanoparticles within a larger area. Additionally, the high cell density decreased the membrane–nanoparticles’ contacting probability but enhanced clathrin-mediated endocytosis. With these contrary effects, the cells with medium cell density or located in the peripheral region of the micropatterned colonies showed a higher cellular uptake capacity of nanoparticles.

Topography-Mediated Enhancement of Nonviral Gene Delivery in Stem Cells

Gene delivery holds great promise for bioengineering, biomedical applications, biosensors, diagnoses, and gene therapy. In particular, the influence of topography on gene delivery is considered to be an attractive approach due to low toxicity and localized delivery properties. Even though many gene vectors and transfection systems have been developed to enhance transfection potential and combining it with other forms of stimulations could even further enhance it. Topography is an interesting surface property that has been shown to stimulate differentiation, migration, cell morphology, and cell mechanics. Therefore, it is envisioned that topography might also be able to stimulate transfection. In this study, we tested the hypothesis “topography is able to regulate transfection efficiency”, for which we used nano- and microwave-like topographical substrates with wavelengths ranging from 500 nm to 25 µm and assessed the transfectability of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and myoblasts. For transfection, Lipofectamine 2000 and a gene encoding plasmid for red-fluorescent protein (m-Cherry) were used and topography-induced cell morphology and transfection efficiency was analyzed. As a result, topography directs cell spreading, elongation, and proliferation as well as the transfection efficiency, which were investigated but were found not to be correlated and dependent on the cell type. A 55% percent improvement of transfection efficiency was identified for hBM-MSCs grown on 2 µm wrinkles (24.3%) as compared to hBM-MSCs cultured on flat controls (15.7%). For myoblast cells, the highest gene-expression efficiency (46.1%) was observed on the 10 µm topography, which enhanced the transfection efficiency by 64% as compared to the flat control (28.1%). From a qualitative assessment, it was observed that the uptake capacity of cationic complexes of TAMRA-labeled oligodeoxynucleotides (ODNs) was not topography-dependent but that the intracellular release was faster, as indicated by the positively stained nuclei on 2 μm for hBM-MSCs and 10 μm for myoblasts. The presented results indicate that topography enhances the gene-delivery capacity and that the responses are dependent on cell type. This study demonstrates the important role of topography on cell stimulation for gene delivery as well as understanding the uptake capacity of lipoplexes and may be useful for developing advanced nonviral gene delivery strategies.

Phase field model for cell spreading dynamics

We suggest a 3D phase field model to describe 3D cell spreading on a flat substrate. The model is a simplified version of a minimal model that was developed in Winkler (Commun Phys 2:82, 2019). Our model couples the order parameter u with 3D polarization (orientation) vector field [Formula: see text] of the actin network. We derive a closed integro-differential equation governing the 3D cell spreading dynamics on a flat substrate, which includes the normal velocity of the membrane, curvature, volume relaxation rate, a function determined by the molecular effects of the subcell level, and the adhesion effect. This equation is easily solved numerically. The results are in agreement with the early fast phase observed experimentally in Dobereiner (Phys Rev Lett 93:108105, 2004). Also we find agreement with the universal power law (Cuvelier in Curr Biol 17:694-699, 2007) which suggest that cell adhesion or contact area versus time behave as [Formula: see text] in the early stage of cell spreading dynamics, and slow down at the next stages.

Magnetic nanocomposite hydrogel with tunable stiffness for probing cellular responses to matrix stiffening

As cells have the capacity to respond to their mechanical environment, cellular biological behaviors can be regulated by the stiffness of extracellular matrix. Moreover, biological processes are dynamic and accompanied by matrix stiffening. Herein, we developed a stiffening cell culture platform based on polyacrylamide-Fe₃O₄ magnetic nanocomposite hydrogel with tunable stiffness under the application of magnetic field. This platform provided a wide range of tunable stiffness (∼0.3-20 kPa) covering most of human tissue elasticity with a high biocompatibility. Overall, the increased magnetic interactions between magnetic nanoparticles reduced the pore size of the hydrogel and enhanced the hydrogel stiffness, thereby facilitating the adhesion and spreading of stem cells, which was attributed to the F-actin assembly and vinculin recruitment. Such stiffening cell culture platform provides dynamic mechanical environments for probing the cellular response to matrix stiffening, and benefits studies of dynamic biological processes. STATEMENT OF SIGNIFICANCE: Cellular biological behaviors can be regulated by the stiffness of extracellular matrix. Moreover, biological processes are dynamic and accompanied by matrix stiffening. Herein, we developed a stiffening cell culture platform based on polyacrylamide/Fe₃O₄ magnetic nanocomposite hydrogels with a wide tunable range of stiffness under the application of magnetic field, without adversely affecting cellular behaviors. Such matrix stiffening caused by enhanced magnetic interaction between magnetic nanoparticles under the application of the magnetic field could induce the morphological variations of stem cells cultured on the hydrogels. Overall, our stiffening cell culture platform can be used not only to probe the cellular response to matrix stiffening but also to benefit various biomedical studies.

Physical and mechanical cues affecting biomaterial-mediated plasmid DNA delivery: insights into non-viral delivery systems

BACKGROUND

Whilst traditional strategies to increase transfection efficiency of non-viral systems aimed at modifying the vector or the polyplexes/lipoplexes, biomaterial-mediated gene delivery has recently sparked increased interest. This review aims at discussing biomaterial properties and unravelling underlying mechanisms of action, for biomaterial-mediated gene delivery. DNA internalisation and cytoplasmic transport are initially discussed. DNA immobilisation, encapsulation and surface-mediated gene delivery (SMD), the role of extracellular matrix (ECM) and topographical cues, biomaterial stiffness and mechanical stimulation are finally outlined.

MAIN TEXT

Endocytic pathways and mechanisms to escape the lysosomal network are highly variable. They depend on cell and DNA complex types but can be diverted using appropriate biomaterials. 3D scaffolds are generally fabricated via DNA immobilisation or encapsulation. Degradation rate and interaction with the vector affect temporal patterns of DNA release and transgene expression. In SMD, DNA is instead coated on 2D surfaces. SMD allows the incorporation of topographical cues, which, by inducing cytoskeletal re-arrangements, modulate DNA endocytosis. Incorporation of ECM mimetics allows cell type-specific transfection, whereas in spite of discordances in terms of optimal loading regimens, it is recognised that mechanical loading facilitates gene transfection. Finally, stiffer 2D substrates enhance DNA internalisation, whereas in 3D scaffolds, the role of stiffness is still dubious.

CONCLUSION

Although it is recognised that biomaterials allow the creation of tailored non-viral gene delivery systems, there still are many outstanding questions. A better characterisation of endocytic pathways would allow the diversion of cell adhesion processes and cytoskeletal dynamics, in order to increase cellular transfection. Further research on optimal biomaterial mechanical properties, cell ligand density and loading regimens is limited by the fact that such parameters influence a plethora of other different processes (e.g. cellular adhesion, spreading, migration, infiltration, and proliferation, DNA diffusion and release) which may in turn modulate gene delivery. Only a better understanding of these processes may allow the creation of novel robust engineered systems, potentially opening up a whole new area of biomaterial-guided gene delivery for non-viral systems.

Continuous monitoring of cell transfection efficiency with micropatterned substrates

The effect of cell-cell contact on gene transfection is mainly unknown. Usually, transfection is carried out in batch cell cultures without control over cellular interactions, and efficiency analysis relies on complex and expensive protocols commonly involving flow cytometry as the final analytical step. Novel platforms and cell patterning are being studied to control cellular interactions and improve quantification methods. In this study, we report the use of surface patterning of fibronectin for the generation of two types of mesenchymal stromal cell patterns: single-cell patterns without cell-to-cell contact, and small cell-colony patterns. Both scenarios allowed the integration of the full transfection process and the continuous monitoring of thousands of individualized events by fluorescence microscopy. Our results showed that cell-to-cell contact clearly affected the transfection, as single cells presented a maximum transfection peak 6 h earlier and had a 10% higher transfection efficiency than cells with cell-to-cell contact.

The varied influences of cell adhesion and spreading on gene transfection of mesenchymal stem cells on a micropatterned substrate

Transmembrane transport of exogenous genes is widely investigated because of high demand for gene therapy. Both gene carriers and cellular conditions can affect gene transfection efficiency. Although cell morphology has been reported to affect cell functions, the influence of cell adhesion area and cell spreading area on the transfection of exogenous genes remains unclear because it is difficult to separate the individual influence of these areas during normal cell culture. In this study, micropatterns were prepared to separately control the adhesion and spreading areas of human bone marrow-derived mesenchymal stem cells (hMSCs). Transfection efficiency of the green fluorescent protein gene to hMSCs cultured on the micropatterns was compared. Cells with a larger adhesion area showed higher transfection efficiency, while cell spreading area hardly affected gene transfection efficiency. Cell adhesion area had dominant influence on gene transfection. Microparticle uptake and BrdU staining showed that the cellular uptake capacity and DNA synthesis activity increased with the increase in cell adhesion area, but were not affected by cell spreading area. The different influence of cell adhesion area and cell spreading area on gene transfection was correlated with their influence on cellular uptake capacity, DNA synthesis activity, focal adhesion formation, cytoskeletal mechanics, and mechanotransduction signal activation. The results suggest that cell adhesion area and cell spreading area had different influence on gene transfection; this finding should provide useful information for the manipulation of cell functions in gene therapy, protein modification, and cell reprogramming. STATEMENT OF SIGNIFICANCE: Cell adhesion and spreading are important morphological factors during the interaction of cells with biomaterial surfaces or interfaces. However, the predominant morphological factor that affects cellular functions such as gene transfection remains unclear. In the present study, special micropatterns were used to precisely control cell adhesion and spreading areas independently. Mesenchymal stem cells cultured on the micropatterns were transfected with the green fluorescent protein gene to compare the different influence of cell adhesion and spreading areas on gene transfection efficiency. Cell adhesion area showed dominant influence on gene transfection, while cell spreading area did not affect gene transfection. The dominant influence of cell adhesion area could be explained by cellular uptake capacity and DNA synthesis activity through the formation of FAs, cytoskeletal mechanics, and YAP/TAZ nuclear localization. The results provide new insights of correlation between cell morphology and cellular functions for designing functional biomaterials.

Micropattern-controlled chirality of focal adhesions regulates the cytoskeletal arrangement and gene transfection of mesenchymal stem cells

Cell chirality has been demonstrated to be important for controlling cell functions. However, it is not clear how the chirality of the extracellular microenvironment regulates cell adhesion and cytoskeletal structures and therefore affects gene transfection. In this study, the chirality of focal adhesions and the cytoskeleton of single human mesenchymal stem cells (hMSCs) was controlled by specially designed micropatterns, and its influence on gene transfection was investigated. Micropatterns with different cell adhesion areas and swirling stripe lines were prepared by micropatterning fibronectin on polystyrene surfaces. The chiral micropatterns induced the formation of chiral focal adhesions and chiral cytoskeletal structures. Gene transfection efficiency was enhanced with increasing adhesion area, while hMSCs on left-handed and right-handed swirling micropatterns showed the same level of gene transfection. When the swirling angle was changed from 0°, 30°, and 60° to 90°, the gene transfection efficiency at a swirling angle of 60° was the lowest. The influence of cell chirality on gene transfection was strongly associated with cellular uptake capacity, DNA synthesis and cytoskeletal mechanics. The results demonstrated that cytoskeletal swirling had a significant influence on gene transfection.

Regulation of gene transfection by cell size, shape and elongation on micropatterned surfaces

Gene transfection has been widely studied due to its potential applications in tissue repair and gene therapy. Many studies have focused on designing gene carriers and developing novel transfection techniques. However, the influence of cell size, shape and elongation on gene transfection has rarely been investigated. In this study, poly(vinyl alcohol)-micropatterned surfaces were prepared to precisely manipulate the size, shape and elongation of mesenchymal stem cells, and the influences of these factors on gene transfection were investigated. Cell size showed a significant influence on gene transfection. Elongation could affect the gene transfection of large cells but not small cells. Cells with a large spreading area and high aspect ratio showed high transfection with exogenous plasmid DNA. In particular, the transfection efficiency was the highest in micropatterned cells with a spreading area of 5024 μm2 and an aspect ratio of 8 : 1. In contrast, cell shape had no significant influence on gene transfection. The different influences of cell size, shape and elongation were correlated with their respective impacts on cytoskeletal structures, cellular nanoparticle uptake and DNA synthesis. Cells with a large size and elongated morphology showed well-organized actin filaments with a high cellular modulus, therefore promoting cellular nanoparticle uptake and DNA synthesis. Cells with different shapes showed similarities in actin filament organization, cellular modulus, uptake capacity and DNA synthesis. The results suggest the importance of cell size and elongation in exogenous gene transfection and should provide useful information for gene transfection and gene therapy.

Harnessing the perinuclear actin cap (pnAC) to influence nanocarrier trafficking and gene transfection efficiency in skeletal myoblasts using nanopillars

Gene transfection is important in biotechnology and is used to modify cells intrinsically. It can be conducted in cell suspension or after cell adhesion, where the efficiency is dependent on many factors such as the type of nanocarrier used and cell division processes. Anchor-dependent cells are sensitive to the substrate they are attached to and adapt their behavior accordingly, including plasmid trafficking during gene transfection. Previously, it was shown in our group that the cytoskeleton is an essential factor in influencing gene transfection in skeletal myoblasts using nanogrooves as a substrate. In this study, the effect of the cytoskeleton on gene transfection efficiency of skeletal myoblasts was studied using various nanopillars and nanocarriers. Nanopillars with different diameters (200-1000 nm) and depths (200 or 400 nm) were fabricated using colloidal self-assembly and reactive ion etching. All surfaces were treated with oxygen plasma or polydopamine (PD) to further control cell morphology. Plasmid DNA was delivered into cells using jetPRIME or Lipofectamine 3000 nanocarriers. After screening hundreds of images, two distinguishable F-actin distributions were found, i.e., cells with or without a perinuclear actin cap (pnAC). Cells attached to nanopillars, especially the deep pillars, had a smaller spreading area, shorter F-actin, more 3D-like cell nuclei, and a lower percentage of pnAC, which lead to a higher gene transfection efficiency using jetPRIME. On the other hand, cells attached to the shallow nanopillars or flat surfaces had a larger spreading area, longer F-actin, more 2D-like cell nuclei, and a higher percentage of pnAC that facilitates gene transfection using Lipofectamine. The effects of cell density, cytoskeleton (cytoD), and focal adhesions (RGD) on gene transfection were also studied, and the results were consistent with our hypothesis that F-actin distribution is one of the critical factors in gene transfection. In conclusion, pnAC plays a vital role in the intracellular trafficking of nanocarrier/plasmid complexes and this study provides new insights into gene transfection in anchor-dependent cells. STATEMENT OF SIGNIFICANCE: This study provides a new perspective in gene transfection using attached cells where perinuclear actin cap (pnAC) is an essential factor involved in transfection efficiency. A series of nanopillars were used to harness cell and cytoskeleton morphology. Two distinguishable cytoskeletal structures were found including cells with or without pnAC. 2D-like cells with pnAC facilitate gene delivery using liposome-based nanocarriers, while 3D-like cells without pnAC benefit gene delivery using cationic polymer-based nanocarriers. This study reveals the importance of the cytoskeleton during gene transfection that is beneficial in tissue transfection.

Mechanical Effect on Gene Transfection Based on Dielectric Elastomer Actuator

Gene transfection has been widely applied in genome function and gene therapy. Although many efforts have been focused on designing carrier materials and transfection methods, the influence of mechanical stimulation on gene transfection efficiency has rarely been studied. Herein, dielectric elastomer actuator (DEA)-based stimulation bioreactors are designed to generate tensile and contractile stress on cells simultaneously. With the example of the EGFP transfection, cells with high membrane tension in the stretching stimulation regions had lower transfection efficiency, while the transfection efficiency of cells in the compressing regions tended to increase. Besides, the duty cycle and loading frequency of the applied stress on cells were also important factors that affect gene transfection efficiency. Furthermore, the pathways of cell endocytosis with the effect of mechanical stimulation were explored on the mechanism for the change of EGFP transfection efficiency. This design of the DEA-based bioreactor, as a strategy to study gene transfection efficiency, could be helpful for developing efficient transfection methods.

Regulation of Stem Cell Functions by Micro-Patterned Structures

Micro-patterned surfaces have been broadly used to control the morphology of stem cells for investigation of the influence of physiochemical and biological cues on stem cell functions. Different structures of micro-patterned surfaces can be prepared by photolithography through designing the photomask features. Cell spreading area, geometry, aspect ratio, and alignment can be regulated by the micro-patterned structures. Their influences on adipogenic, osteogenic, and smooth muscle differentiation of the human bone marrow-derived mesenchymal stem cells are compared and investigated in details. Variation of cell morphology can trigger rearrangement of cytoskeleton, generating cytoskeletal mechanical stimulation and consequently inducing differentiation of mesenchymal stem cells into different lineages. This chapter summarizes the latest development of regulation of mesenchymal stem cell morphology by micro-patterns and the influence on the behaviors and differentiation of the mesenchymal stem cells.

Influence of Cell Spreading Area on the Osteogenic Commitment and Phenotype Maintenance of Mesenchymal Stem Cells

Osteogenic differentiation and commitment of mesenchymal stem cells (MSCs) is a complex process that is induced and regulated by various biological factors and biophysical cues. Although cell spreading area, as a biophysical cue, has been demonstrated to play a critical role in the regulation of osteogenic differentiation of MSCs, it is unclear how it affects the maintenance of the committed phenotype after osteogenic differentiation of MSCs. In this study, poly (vinyl alcohol) was micropatterned on a tissue culture polystyrene surface, and the micropatterns were used to culture MSCs to control their cell spreading area. The influence of cell spreading area on osteogenic differentiation and maintenance of the differentiated phenotype of MSCs was investigated. MSCs with a larger spreading area showed a higher degree of osteogenic differentiation, slower loss of differentiated phenotype and slower re-expression of stem cell markers compared with MSCs with a smaller spreading area. A large cell spreading area was beneficial for osteogenic differentiation of MSCs and maintenance of their differentiated phenotype.

Electroporation: A Sustainable and Cell Biology Preserving Cell Labeling Method for Adipogenous Mesenchymal Stem Cells

Human mesenchymal stem cells derived from adipose tissue (AD-hMSCs) represent a promising source for tissue engineering and are already widely used in cell therapeutic clinical trials. Until today, an efficient and sustainable cell labeling system for cell tracking does not exist. We evaluated transient transfection through electroporation for cell labeling and compared it with lentiviral transduction for AD-hMSCs. In addition, we tested whether nonsense DNA or a reporter gene such as enhanced green fluorescent protein (EGFP) is the more suitable label for AD-hMSCs. Using electroporation, the transfection efficiency reached a maximal level of 44.6 ± 1.1% EGFP-positive cells after selective and expansive cultivation of the mixed MSC population, and was 44.5 ± 1.4% after gene transfer with Cyanin3-marked nonsense-label DNA, which remained stable during 2 weeks of nonselective cultivation (37.2 ± 4.7% positive AD-hMSCs). Electroporation with both nonsense DNA and pEGFP-N1 led to a slight growth retardation of 45.2% and 59.1%, respectively. EGFP-transfected or transduced AD-hMSCs showed a limited adipogenic and osteogenic differentiation capacity, whereas it was almost unaffected in cells electroporated with the nonsense-label DNA. The nonsense DNA was detectable through quantitative real-time polymerase chain reaction for at least 5 weeks/10 passages and in differentiated AD-hMSCs. EGFP-labeled cells were trackable for 24 h in vitro and served as testing cells with new materials for dental implants for 7 days. In contrast, lentivirally transduced AD-hMSCs showed an altered natural immune phenotype of the AD-hMSCs with lowered expression of two cell type defining surface markers (CD44 and CD73) and a relevantly decreased cell growth by 71.8% as assessed by the number of colony-forming units. We suggest electroporation with nonsense DNA as an efficient and long-lasting labeling method for AD-hMSCs with the comparably lowest negative impact on the phenotype or the differentiation capacity of the cells, which may, therefore, be suitable for tissue engineering. In contrast, EGFP transfection by electroporation is efficient but may be more suitable for cell tracking within cell therapies without MSC differentiation procedures. Since current protocols of lentiviral gene transduction include the risk of cell biological alterations, electroporation seems advantageous and sustainable enough for hMSC labeling.