Deficiency of mastl, a mitotic regulator, results in cell detachment from developing tissues of zebrafish embryos

To form tissues with unique functions and structures, it is important that the cells that comprise them maintain physical contact. On the other hand, with each mitosis, drastic changes in cell shapes, cell adhesion, and cytoskeletal architecture may cause such contacts to be temporarily weakened, risking improper development and maintenance of tissues. Despite such risks, tissues form properly during normal development. However, it is not well understood whether mitotic abnormalities affect tissue formation. Here, analysis of zebrafish embryos with aberrant mitosis shows that proper progression of mitosis is important to maintain cell contact in developing tissues. By screening mutants with abnormal trunk and tail development, we obtained a mutant with perturbed expression of some tissue-specific genes in embryonic caudal regions. The responsible gene is mastl/gwl, which is involved in progression of mitosis. Analysis focusing on the chordo-neural hinge (CNH), the primordium of axial tissues, shows that cell detachment from the CNH is increased in mastl mutant embryos. Time-lapse imaging reveals that this cell detachment occurs during mitosis. These results suggest that cells are unable to maintain contact due to abnormalities in progression of mitosis in mastl mutants.

Fluid and Bubble Flow Detach Adherent Cancer Cells to Form Spheroids on a Random Positioning Machine

In preparing space and microgravity experiments, the utilization of ground-based facilities is common for initial experiments and feasibility studies. One approach to simulating microgravity conditions on Earth is to employ a random positioning machine (RPM) as a rotary bioreactor. Combined with a suitable low-mass model system, such as cell cultures, these devices simulating microgravity have been shown to produce results similar to those obtained in a space experiment under real microgravity conditions. One of these effects observed under real and simulated microgravity is the formation of spheroids from 2D adherent cancer cell cultures. Since real microgravity cannot be generated in a laboratory on Earth, we aimed to determine which forces lead to the detachment of individual FTC-133 thyroid cancer cells and the formation of tumor spheroids during culture with exposure to random positioning modes. To this end, we subdivided the RPM motion into different static and dynamic orientations of cell culture flasks. We focused on the molecular activation of the mechanosignaling pathways previously associated with spheroid formation in microgravity. Our results suggest that RPM-induced spheroid formation is a two-step process. First, the cells need to be detached, induced by the cell culture flask's rotation and the subsequent fluid flow, as well as the presence of air bubbles. Once the cells are detached and in suspension, random positioning prevents sedimentation, allowing 3D aggregates to form. In a comparative shear stress experiment using defined fluid flow paradigms, transcriptional responses were triggered comparable to exposure of FTC-133 cells to the RPM. In summary, the RPM serves as a simulator of microgravity by randomizing the impact of Earth's gravity vector especially for suspension (i.e., detached) cells. Simultaneously, it simulates physiological shear forces on the adherent cell layer. The RPM thus offers a unique combination of environmental conditions for in vitro cancer research.

Supramolecular Responsive Chitosan Microcarriers for Cell Detachment Triggered by Adamantane

Supramolecular responsive microcarriers based on chitosan microspheres were prepared and applied for nonenzymatic cell detachment. Briefly, chitosan microspheres (CSMs) were first prepared by an emulsion crosslinking approach, the surface of which was then modified with β-cyclodextrin (β-CD) by chemical grafting. Subsequently, gelatin was attached onto the surface of the CSMs via the host-guest interaction between β-CD groups and aromatic residues in gelatin. The resultant microspheres were denoted CSM-g-CD-Gel. Due to their superior biocompatibility and gelatin niches, CSM-g-CD-Gel microspheres can be used as effective microcarriers for cell attachment and expansion. L-02, a human fetal hepatocyte line, was used to evaluate cell attachment and expansion with these microcarriers. After incubation for 48 h, the cells attached and expanded to cover the entire surface of microcarriers. Moreover, with the addition of adamantane (AD), cells can be detached from the microcarriers together with gelatin because of the competitive binding between β-CD and AD. Overall, these supramolecular responsive microcarriers could effectively support cell expansion and achieve nonenzymatic cell detachment and may be potentially reusable with a new cycle of gelatin attachment and detachment.

An improved method for intracellular DNA (iDNA) recovery from terrestrial environments

The simultaneous extraction of intracellular DNA (iDNA) and extracellular DNA (eDNA) can help to separate the living in situ community (represented by iDNA) from background DNA that originated both from past communities and from allochthonous sources. As iDNA and eDNA extraction protocols require separating cells from the sample matrix, their DNA yields are generally lower than direct methods that lyse the cells within the sample matrix. We, therefore, tested different buffers with and without adding a detergent mix (DM) in the extraction protocol to improve the recovery of iDNA from surface and subsurface samples that covered a variety of terrestrial environments. The combination of a highly concentrated sodium phosphate buffer plus DM significantly improved iDNA recovery for almost all tested samples. Additionally, the combination of sodium phosphate and EDTA improved iDNA recovery in most of the samples and even allowed the successful extraction of iDNA from extremely low-biomass iron-bearing rock samples taken from the deep biosphere. Based on our results, we recommend using a protocol with sodium phosphate in combination with either a DM (NaP 300 mM + DM) or EDTA (NaP + EDTA 300 mM). Furthermore, for studies that rely on the eDNA pool, we recommend using buffers solely based on sodium phosphate because the addition of EDTA or a DM resulted in a decrease in eDNA for most of the tested samples. These improvements can help reduce community bias in environmental studies and contribute to better characterizations of both modern and past ecosystems.

Rosavin Ameliorates Hepatic Inflammation and Fibrosis in the NASH Rat Model via Targeting Hepatic Cell Death

Background: Non-alcoholic fatty liver disease (NAFLD) represents the most common form of chronic liver disease that urgently needs effective therapy. Rosavin, a major constituent of the Rhodiola Rosea plant of the family Crassulaceae, is believed to exhibit multiple pharmacological effects on diverse diseases. However, its effect on non-alcoholic steatohepatitis (NASH), the progressive form of NAFLD, and the underlying mechanisms are not fully illustrated. Aim: Investigate the pharmacological activity and potential mechanism of rosavin treatment on NASH management via targeting hepatic cell death-related (HSPD1/TNF/MMP14/ITGB1) mRNAs and their upstream noncoding RNA regulators (miRNA-6881-5P and lnc-SPARCL1-1:2) in NASH rats. Results: High sucrose high fat (HSHF) diet-induced NASH rats were treated with different concentrations of rosavin (10, 20, and 30 mg/kg/day) for the last four weeks of dietary manipulation. The data revealed that rosavin had the ability to modulate the expression of the hepatic cell death-related RNA panel through the upregulation of both (HSPD1/TNF/MMP14/ITGB1) mRNAs and their epigenetic regulators (miRNA-6881-5P and lnc-SPARCL1-1:2). Moreover, rosavin ameliorated the deterioration in both liver functions and lipid profile, and thereby improved the hepatic inflammation, fibrosis, and apoptosis, as evidenced by the decreased protein levels of IL6, TNF-α, and caspase-3 in liver sections of treated animals compared to the untreated NASH rats. Conclusion: Rosavin has demonstrated a potential ability to attenuate disease progression and inhibit hepatic cell death in the NASH animal model. The produced effect was correlated with upregulation of the hepatic cell death-related (HSPD1, TNF, MMP14, and ITGB1) mRNAs—(miRNA-6881-5P—(lnc-SPARCL1-1:2) RNA panel.

SRC plays a specific role in the cross-talk between apoptosis and autophagy via phosphorylation of a novel regulatory site on AMPK

Cell detachment from the extracellular matrix (ECM) typically promotes cell death via a form of apoptosis known as anoikis. However, in tumor cells, detachment can also induce cell survival, utilizing a process known as macroautophagy/autophagy, which involves degradation and removal of apoptotic proteins as well as rewiring of metabolic pathways so that cells can survive under stress. The crosstalk between the competing processes of anoikis and autophagy is only partially understood but may be critical for the design of multi-drug therapeutic strategies. Here, we summarize our recent studies, which reveal a direct regulatory link between a major mediator of cell survival in adherent cells, the ECM-integrin-activated dual tyrosine kinase complex of SRC and PTK2/FAK, and a major regulator of cell metabolism and autophagy, AMP-activated protein kinase (AMPK). We identify a novel SRC phosphorylation site on AMPK and demonstrate that this phosphorylation event plays key roles in AMPK regulation, autophagy induction, and cell survival.

Dysregulation of Cytoskeleton Remodeling Drives Invasive Leading Cells Detachment

Simple Summary

Detachment of cancer cells is the first step in tumor metastasis and malignancy. Our results showed that the TGF-β1/vimentin/focal adhesion protein assembly axis was involved in the control of the dynamics of initial tumor detachment under adequate nutrition, based on the Boyden chamber and 3D in-gel spheroid analysis.

Abstract

Detachment of cancer cells is the first step in tumor metastasis and malignancy. However, studies on the balance of initial tumor anchoring and detachment are limited. Herein, we revealed that the regulation of cytoskeleton proteins potentiates tumor detachment. The blockage of TGF-β1 using neutralizing antibodies induced cancer cell detachment in the Boyden chamber and 3D in-gel spheroid models. Moreover, treatment with latrunculin B, an actin polymerization inhibitor, enhanced cell dissociation by abolishing actin fibers, indicating that TGF-β1 mediates the formation of actin stress fibers, and is likely responsible for the dynamics of anchoring and detachment. Indeed, latrunculin B disrupted the formation of external TGF-β1-induced actin fibers and translocation of intracellular vinculin, a focal adhesion protein, resulting in the suppression of cell adhesion. Moreover, the silencing of vimentin substantially reduced cell adhesion and enhanced cell detachment, revealing that cell adhesion and focal adhesion protein translocation stimulated by TGF-β1 require vimentin. Using the 3D in-gel spheroid model, we found that latrunculin B suppressed the cell adhesion promoted by external TGF-β1, increasing the number of cells that penetrated the Matrigel and detached from the tumor spheres. Thus, cytoskeleton remodeling maintained the balance of cell anchoring and detachment, and the TGF-β1/vimentin/focal adhesion protein assembly axis was involved in the control dynamics of initial tumor detachment.

Inhibition of Matrix Metalloproteinases and Cancer Cell Detachment by Ru(II) Polypyridyl Complexes Containing 4,7-Diphenyl-1,10-phenanthroline Ligands-New Candidates for Antimetastatic Agents

Primary tumor targeting is the dominant approach in drug development, while metastasis is the leading cause of cancer death. Therefore, in addition to the cytotoxic activity of a series of Ru(II) polypyridyl complexes of the type [Ru(dip)₂L]²⁺ (dip: 4,7-diphenyl-1,10-phenanthroline while L = dip; bpy: 2,2′-bipyridine; bpy-SC: bipyridine derivative bearing a semicarbazone 2-formylopyridine moiety; dpq, dpq(CH₃)₂, dpb: quinoxaline derivatives) their ability to inhibit cell detachment was investigated. In vitro studies performed on lung cancer A549 cells showed that they accumulate in cells very well and exhibit moderate cytotoxicity with IC₅₀ ranging from 4 to 13 µM. Three of the studied compounds that have dip, bpy-SC, or dpb ligands after treatment of the cells with a non-toxic dose (<¹/₂IC₅₀) enhanced their adhesion properties demonstrated by lower detachment in the trypsin resistance assay. The same complexes inhibited both MMP-2 and MMP-9 enzyme activities with IC₅₀ ranging from 2 to 12 µM; however, the MMP-9 inhibition was stronger. More detailed studies for [Ru(dip)₂(bpy-SC)]²⁺, which induced the greatest increase in cell adhesion, revealed that it is predominately accumulated in the cytoskeletal fraction of A549 cells. Moreover, cells treated with this compound showed the localization of MMP-9 to a greater extent also in the cytoskeleton. Taken together, our results indicate the possibility of a reduction of metastatic cells escaping from the primary lesion to the surrounding tissue by prevention of their detachment and by influencing the activity of MMP-2 and MMP-9.

[Construction of tissue engineered cell sheet]

Scaffold-free tissue engineered cell sheet is an emerging technology in biomedical field. It can avoid the adverse effects of scaffold materials, and can be further assembled to form more complex three-dimensional functional tissues. The construction of cell sheet is mainly based on the culture substrate composed of sensitive materials. By changing the stimulation factors such as temperature, enzyme, light, ion, redox, pH and sugar, the adhesion behavior of the substrate to the cells could be changed to make the cells detach naturally, thus generating the cell sheet. Recent years have seen the development of various simple and efficient construction technologies of cell sheet due to the development of a variety of novel sensitive culture substrates. The resulted cell sheets with excellent performance have greatly expanded their applications. This review summarized the construction methods of tissue engineered cell sheet and discussed the challenges and future perspectives in this field.

Escherichia coli Alpha-Hemolysin HlyA Induces Host Cell Polarity Changes, Epithelial Barrier Dysfunction and Cell Detachment in Human Colon Carcinoma Caco-2 Cell Model via PTEN-Dependent Dysregulation of Cell Junctions

Escherichia coli (E. coli) of the B2 phylotype reside in human and animal intestines. The bacteria possess pathogenicity factors such as α-hemolysin (HlyA) that can induce intestinal epithelial leaks. We addressed the questions which host cell processes were dysregulated by E. coli HlyA that can potentiate intestinal diseases. The colon carcinoma cell line Caco-2 was infected by HlyA⁺ E. coli. Cell polarity regulation was analyzed by live cell imaging for the phosphatidylinositol-4,5-bisphosphate (PIP2) abundance. In Caco-2 monolayers, transepithelial electrical resistance was measured for characterization of barrier function. Cell proliferation and separation were assessed microscopically. Epithelial regulation and cell signaling were analyzed by RNA-Seq and Ingenuity Pathway Analysis (IPA). Our main findings from E. coli HlyA toxinogenicity in the colon carcinoma cell line are that (i) PIP2 at the membrane decrease, (ii) PTEN (phosphatase and tensin homolog) inhibition leads to cell polarity changes, (iii) epithelial leakiness follows these polarity changes by disruption of cell junctions and (iv) epithelial cell detachment increases. HlyA affected pathways, e.g., the PTEN and metastasis signaling, were identified by RNA-Seq bioinformatics calculations in IPA. In conclusion, HlyA affects cell polarity, thereby inducing epithelial barrier dysfunction due to defective tight junctions and focal leak induction as an exemplary mechanism for leaky gut.

Spontaneous Cell Detachment and Reattachment in Cancer Cell Lines: An In Vitro Model of Metastasis and Malignancy

There is an unmet need for simplified in vitro models of malignancy and metastasis that facilitate fast, affordable and scalable gene and compound analysis. "Adherent" cancer cell lines frequently release "free-floating" cells into suspension that are viable and can reattach. This, in a simplistic way, mimics the metastatic process. We compared the gene expression profiles of naturally co-existing populations of floating and adherent cells in SW620 (colon), C33a (cervix) and HeLa (cervix) cancer cells. We found that 1227, 1367 and 1333 genes were at least 2-fold differentially expressed in the respective cell lines, of which 122 were shared among the three cell lines. As proof of principle, we focused on the anti-metastatic gene NM23-H1, which was downregulated both at the RNA and protein level in the floating cell populations of all three cell lines. Knockdown of NM23-H1 significantly increased the number of floating (and viable) cells, whereas overexpression of NM23-H1 significantly reduced the proportion of floating cells. Other potential regulators of these cellular states were identified through pathway analysis, including hypoxia, mTOR (mechanistic target of rapamycin), cell adhesion and cell polarity signal transduction pathways. Hypoxia, a condition linked to malignancy and metastasis, reduced NM23-H1 expression and significantly increased the number of free-floating cells. Inhibition of mTOR or Rho-associated protein kinase (ROCK) significantly increased cell death specifically in the floating and not the adherent cell population. In conclusion, our study suggests that dynamic subpopulations of free-floating and adherent cells is a useful model to screen and identify genes, drugs and pathways that regulate the process of cancer metastasis, such as cell detachment and anoikis.

Microcarrier-based stem cell bioprocessing: GMP-grade culture challenges and future trends for regenerative medicine

Recently, stem cell-based therapies have been proposed as an alternative for the treatment of many diseases. Stem cells (SCs) are well known for their capacity to preserve themselves, proliferate, and differentiate into multiple lineages. These characteristics allow stem cells to be a viable option for the treatment of diverse diseases. Traditional methodologies based on 2-dimensional culture techniques (T-flasks and Petri dishes) are simple and well standardized; however, they present disadvantages that limit the production of the cell yield required for regenerative medicine applications. Lately, microcarrier (MC)-based culture techniques have emerged as an attractive platform for expanding stem cells in suspension systems. Although the use of stem cell expansion on MCs has recently shown significant increase, their implementation for medical purposes is been hampered by bottlenecks in upstream and downstream processing. Therefore, there is an urgent need in the development of bioprocesses that simplify stem cell cultures under xeno-free conditions and detachment from MCs without diminishing their pluripotency and viability. A critical analysis of the factors that impact the up and downstream bioprocessing on MC-based stem cell cultures is presented in this review. This analysis aims to raise the awareness of the current drawbacks that limit MC-based stem cell bioprocessing in regenerative medicine and propose alternatives to overcome them.

QCM-D Study of Time-Resolved Cell Adhesion and Detachment: Effect of Surface Free Energy on Eukaryotes and Prokaryotes

Cell-material interactions are crucial for many biomedical applications, including medical implants, tissue engineering, and biosensors. For implants, while the adhesion of eukaryotic host cells is desirable, bacterial adhesion often leads to infections. Surface free energy (SFE) is an important parameter that controls short- and long-term eukaryotic and prokaryotic cell adhesion. Understanding its effect at a fundamental level is essential for designing materials that minimize bacterial adhesion. Most cell adhesion studies for implants have focused on correlating surface wettability with mammalian cell adhesion and are restricted to short-term time scales. In this work, we used quartz crystal microbalance with dissipation monitoring (QCM-D) and electrical impedance analysis to characterize the adhesion and detachment of S. cerevisiae and E. coli, serving as model eukaryotic and prokaryotic cells within extended time scales. Measurements were performed on surfaces displaying different surface energies (Au, SiO₂, and silanized SiO₂). Our results demonstrate that tuning the surface free energy of materials is a useful strategy for selectively promoting eukaryotic cell adhesion and preventing bacterial adhesion. Specifically, we show that under flow and steady-state conditions and within time scales up to ∼10 h, a high SFE, especially its polar component, enhances S. cerevisiae adhesion and hinders E. coli adhesion. In the long term, however, both cells tend to detach, but less detachment occurs on surfaces with a high dispersive SFE contribution. The conclusions on S. cerevisiae are also valid for a second eukaryotic cell type, being the human embryonic kidney (HEK) cells on which we performed the same analysis for comparison. Furthermore, each cell adhesion phase is associated with unique cytoskeletal viscoelastic states, which are cell-type-specific and surface free energy-dependent and provide insights into the underlying adhesion mechanisms.

Rapid Photoinduced Single Cell Detachment from Gold Nanoparticle-Embedded Collagen Gels with Low Denaturation Temperature

Cell Separation is important in various biomedical fields. We have prepared gold nanoparticle (AuNP)-embedded collagen gels as a visible-light-responsive cell scaffold in which photoinduced single cell detachment occurs through local thermal denaturation of the collagen gel via the photothermal effect of AuNP. Physicochemical properties of collagen materials depend on the origin of the collagen and the presence of telopeptides. In this study, we prepared various AuNP-embedded collagen gels by using different collagen materials with and without the telopeptides to compare their thermal denaturation properties and photoinduced single cell detachment behaviors. Cellmatrix type I-C without telopeptides exhibited a lower denaturation temperature than Cellmatrix type I-A and Atelocell IAC, as examined by Fourier transform infrared (FTIR) spectroscopy, rheological analysis, and sol-gel transition observation. Three-dimensional (3D) laser microscopic imaging revealed that collagen fibers shrank in Cellmatrix type I-A upon heating, but collagen fibers disappeared in Cellmatrix type I-C upon heating. Cells cultured on the Cellmatrix type I-C-based AuNP-embedded collagen gel detached with shorter photoirradiation than on the Cellmatrix type I-A-based AuNP-embedded collagen gel, suggesting that collagen gels without telopeptides are suitable for a photoinduced single cell detachment system.

Recent Advances in ROS-Responsive Cell Sheet Techniques for Tissue Engineering

Cell sheet engineering has evolved rapidly in recent years as a new approach for cell-based therapy. Cell sheet harvest technology is important for producing viable, transplantable cell sheets and applying them to tissue engineering. To date, most cell sheet studies use thermo-responsive systems to detach cell sheets. However, other approaches have been reported. This review provides the progress in cell sheet detachment techniques, particularly reactive oxygen species (ROS)-responsive strategies. Therefore, we present a comprehensive introduction to ROS, their application in regenerative medicine, and considerations on how to use ROS in cell detachment. The review also discusses current limitations and challenges for clarifying the mechanism of the ROS-responsive cell sheet detachment.

Cell detachment rapidly induces changes in noncoding RNA expression in human mesenchymal stromal cells

Aims: To identify differential expression of noncoding RNAs after trypsinization in human mesenchymal stromal cells (hMSCs), focusing on miRNAs, piRNAs and circRNAs. Methods: hMSCs from the bone marrow of three donors were collected for RNA extraction, either lysed directly in monolayer or trypsinized and lysed within 30 min. Total RNA was isolated and sequenced for the evaluation of miRNA and piRNA expression or RNaseR treated and labeled for circRNA array hybridization. RT-qPCR was performed to evaluate the stability of candidate reference genes. Results & conclusions: Alterations in levels of several noncoding RNAs are rapidly induced after trypsinization of hMSCs, affecting critical pathways. This should be carefully considered for a proper experimental design.

In Situ Subcellular Detachment of Cells Using a Cell-Friendly Photoresist and Spatially Modulated Light

Dynamic adhesion and detachment of subcellular regions occur during cell migration, thus a technique allowing precise control of subcellular detachment of cells will be useful for cell migration study. Previous methods for cell detachment were developed either for harvesting cells or cell sheets attached on surfaces with low resolution patterning capability, or for detaching subcellular regions located on predefined electrodes. In this paper, a method that allows in situ subcellular detachment of cells with ≈1.5 µm critical feature size while observing cells under a fluorescence microscope is introduced using a cell-friendly photoresist and spatially modulated light. Using this method, a single cell, regions in cell sheets, and a single focal adhesion complex within a cell are successfully detached. Furthermore, different subcellular regions of migrating cells are detached and changes in cell polarity and migration direction are quantitatively analyzed. This method will be useful for many applications in cell detachment, in particular when subcellular resolution is required.

Filamentous Non-albicans Candida Species Adhere to Candida albicans and Benefit From Dual Biofilm Growth

Non-albicans Candida species (NACS) are often isolated along with Candida albicans in cases of oropharyngeal candidiasis. C. albicans readily forms biofilms in conjunction with other oral microbiota including both bacteria and yeast. Adhesion between species is important to the establishment of these mixed biofilms, but interactions between C. albicans and many NACS are not well-characterized. We adapted a real-time flow biofilm model to study adhesion interactions and biofilm establishment in C. albicans and NACS in mono- and co-culture. Out of five NACS studied, only the filamenting species C. tropicalis and C. dubliniensis were capable of adhesion with C. albicans, while C. parapsilosis, C. lusitaniae, and C. krusei were not. Over the early phase (0-4 h) of biofilm development, both mono- and co-culture followed similar kinetics of attachment and detachment events, indicating that initial biofilm formation is not influenced by inter-species interactions. However, the NACS showed a preference for inter-species cell-cell interactions with C. albicans, and at later time points (5-11 h) we found that dual-species interactions impacted biofilm surface coverage. Dual-species biofilms of C. tropicalis and C. albicans grew more slowly than C. albicans alone, but achieved higher surface coverage than C. tropicalis alone. Biofilms of C. dubliniensis with C. albicans increased surface coverage more rapidly than either species alone. We conclude that dual culture biofilm of C. albicans with C. tropicalis or C. dubliniensis offers a growth advantage for both NACS. Furthermore, the growth and maintenance, but not initial establishment, of dual-species biofilms is likely facilitated by interspecies cell-cell adherence.

Role of Membrane Cholesterol Levels in Activation of Lyn upon Cell Detachment

Cholesterol, a major component of the plasma membrane, determines the physical properties of biological membranes and plays a critical role in the assembly of membrane microdomains. Enrichment or deprivation of membrane cholesterol affects the activities of many signaling molecules at the plasma membrane. Cell detachment changes the structure of the plasma membrane and influences the localizations of lipids, including cholesterol. Recent studies showed that cell detachment changes the activities of a variety of signaling molecules. We previously reported that the localization and the function of the Src-family kinase Lyn are critically regulated by its membrane anchorage through lipid modifications. More recently, we found that the localization and the activity of Lyn were changed upon cell detachment, although the manners of which vary between cell types. In this review, we highlight the changes in the localization of Lyn and a role of cholesterol in the regulation of Lyn’s activation following cell detachment.

Thermo-responsive cell culture carrier: Effects on macrophage functionality and detachment efficiency

Harvesting cultivated macrophages for tissue engineering purposes by enzymatic digestion of cell adhesion molecules can potentially result in unintended activation, altered function, or behavior of these cells. Thermo-responsive polymer is a promising tool that allows for gentle macrophage detachment without artificial activation prior to subculture within engineered tissue constructs. We therefore characterized different species of thermo-responsive polymers for their suitability as cell substrate and to mediate gentle macrophage detachment by temperature shift. Primary human monocyte- and THP-1-derived macrophages were cultured on thermo-responsive polymers and characterized for phagocytosis and cytokine secretion in response to lipopolysaccharide stimulation. We found that both cell types differentially respond in dependence of culture and stimulation on thermo-responsive polymers. In contrast to THP-1 macrophages, primary monocyte-derived macrophages showed no signs of impaired viability, artificial activation, or altered functionality due to culture on thermo-responsive polymers compared to conventional cell culture. Our study demonstrates that along with commercially available UpCell carriers, two other thermo-responsive polymers based on poly(vinyl methyl ether) blends are attractive candidates for differentiation and gentle detachment of primary monocyte-derived macrophages. In summary, we observed similar functionality and viability of primary monocyte-derived macrophages cultured on thermo-responsive polymers compared to standard cell culture surfaces. While this first generation of custom-made thermo-responsive polymers does not yet outperform standard culture approaches, our results are very promising and provide the basis for exploiting the unique advantages offered by custom-made thermo-responsive polymers to further improve macrophage culture and recovery in the future, including the covalent binding of signaling molecules and the reduction of centrifugation and washing steps. Optimizing these and other benefits of thermo-responsive polymers could greatly improve the culture of macrophages for tissue engineering applications.

Enzyme-free cell detachment mediated by resonance vibration with temperature modulation

Cell detachment is an essential process in adherent cell culture. However, trypsinization, which is the most popular detachment technique used in culture, damages cellular membranes. Reducing cellular membrane damage during detachment should improve the quality of cell culture. In this article, we propose an enzyme-free cell detachment method based on resonance vibration with temperature modulation. We developed a culture device that can excite a resonance vibration and control temperature. We then evaluated the cell detachment ratio and the growth response, observed the morphology, and analyzed the cellular protein of the collected cells-mouse myoblast cell line (C2C12). With the temperature of 10°C and the maximum vibration amplitude of 2 μm, 77.9% of cells in number were successfully detached compared with traditional trypsinization. The 72-h proliferation ratio of the reseeded cells was similar to that with trypsinization, whereas the proliferation ratio of proposed method was 12.6% greater than that of trypsinization after freezing and thawing. Moreover, the cells can be collected relatively intact and both intracellular and cell surface proteins in the proposed method were less damaged than in trypsinization. These results show that this method has definite advantages over trypsinization, which indicates that it could be applied to subcultures of cells that are more susceptible to trypsin damage for mass culture of sustainable clinical use. Biotechnol. Bioeng. 2017;114: 2279-2288. © 2017 Wiley Periodicals, Inc.

Selective Photomechanical Detachment and Retrieval of Divided Sister Cells from Enclosed Microfluidics for Downstream Analyses

Considerable evidence suggests that self-renewal and differentiation of cancer stem-like cells, a key cell population in tumorgenesis, can determine the outcome of disease. Though the development of microfluidics has enhanced the study of cellular lineage, it remains challenging to retrieve sister cells separately inside enclosed microfluidics for further analyses. In this work, we developed a photomechanical method to selectively detach and reliably retrieve target cells from enclosed microfluidic chambers. Cells cultured on carbon nanotube-polydimethylsiloxane composite surfaces can be detached using shear force induced through irradiation of a nanosecond-pulsed laser. This retrieval process has been verified to preserve cell viability, membrane proteins, and mRNA expression levels. Using the presented method, we have successfully performed 96-plex single-cell transcriptome analysis on sister cells in order to identify the genes altered during self-renewal and differentiation, demonstrating phenomenal resolution in the study of cellular lineage.

SiO2/TiO2 Nanocomposite Films on Polystyrene for Light-Induced Cell Detachment Application

Light-induced cell detachment shows much potential in in vitro cell culture and calls for high-performance light-responsive films. In this study, a smooth and dense SiO₂/TiO₂ nanocomposite thin film with thickness of around 250 nm was first fabricated on H₂O₂ treated polystyrene (PS) substrate via a low-temperature sol-gel method. It was observed that the film could well-adhere on the PS surface and the bonding strength became increasingly high with the increase of SiO₂ content. The peeling strength and shear strength reached 3.05 and 30.02 MPa, respectively. It was observed the surface of the film could transform into superhydrophilic upon 20 min illumination of ultraviolet with a wavelength of 365 nm (UV365). In cell culture, cells, i.e., NIH3T3 and MC3T3-E1 cells, cultured on SiO₂/TiO₂ nanocomposite film were easily detached after 10 min of UV365 illumination; the detachment rates reached 90.8% and 88.6%, respectively. Correspondingly, continuous cell sheets with good viability were also easily obtained through the same way. The present work shows that SiO₂/TiO₂ nanocomposite thin film could be easily prepared on polymeric surface at low temperature. The corresponding film exhibits excellent biocompatibility, high bonding strength, and good light responses. It could be a good candidate for the surface of cell culture utensils with light-induced cell detachment property.

Impact of Detachment Methods on M2 Macrophage Phenotype and Function

The methods of cell detachment influence phenotype and function of human macrophages cultured in vitro. However, comparative studies defining the influence of cell detachment techniques on secondary characterization of M1 or M2 polarized macrophages are largely absent from the literature. In this study we evaluated the impact of trypsin, accutase, EDTA, PBS, and cell scraping on: A. cell recovery, B. phenotype and C. function of in vitro polarized macrophages. Our data demonstrate that while exposure to trypsin or accutase yields highly efficient recovery of viable cells, such chemical cleavage results in loss of select M2 cell surface markers with correlative changes in cell function. In contrast, phenotype and function are maintained following detachment by EDTA on ice. Our data suggest that seemingly "trivial" changes in methodologies for macrophage detachment induce both variable and profound changes on cell phenotype and function which can dramatically impact the results of polarization experiments.

Ouabain enhances lung cancer cell detachment

A human steroid hormone, ouabain, has been shown to play a role in several types of cancer cell behavior; however, its effects on cancer metastasis are largely unknown. Herein, we demonstrate that sub-toxic concentrations of ouabain facilitate cancer cell detachment from the extracellular matrix in human lung cancer cells. Ouabain at concentrations of 0-10 pM significantly enhanced cell detachment in dose- and time- dependent manners, while having minimal effect on cell viability. The detachment-inducing effect of ouabain was found to be mediated through focal-adhesion kinase and ATP-dependent tyrosine kinase pathways. Alpha-5 and beta-1 integrins were found to be down-regulated in response to ouabain treatment. Since detachment of cancer cells is a prerequisite process for metastasis to begin, these insights benefit our understanding over the molecular basis of cancer biology.

Localized micro-scale disruption of cells using laser-generated focused ultrasound

We utilize laser-generated focused ultrasound (LGFU) to create targeted mechanical disturbance on a few cells. The LGFU is transmitted through an optoacoustic lens that converts laser pulses into focused ultrasound. The tight focusing (<100 µm) and high peak pressure of the LGFU produces cavitational disturbances at a localized spot with micro-jetting and secondary shock-waves arising from micro-bubble collapse. We demonstrate that LGFU can be used as a non-contact, non-ionizing, high-precision tool to selectively detach a single cell from its culture substrate. Furthermore, we explore the possibility of biomolecule delivery in a small population of cells targeted by LGFU at pressure amplitudes below and above the cavitation threshold. We experimentally confirm that cavitational disruption is required for delivery of propidium iodide, a membrane-impermeable nucleic acid-binding dye, into cells.

Rate control of cell sheet recovery by incorporating hydrophilic pattern in thermoresponsive cell culture dish

Thready stripe-polyacrylamide (PAAm) pattern was fabricated on a thermoresponsive poly(N-isopropylacrylamide) (PIPAAm) surface, and their surface properties were characterized. A PIPAAm surface spin-coated with positive photoresist was irradiated through a 5 µm/5 µm or a 10 µm/10-µm black and white striped photomask, resulting in the radical polymerization of AAm on the photoirradiated area. After staining with Alexa488 bovine serum albumin, the stripe-patterned surface was clearly observed and the patterned surface was also observed by a phase contrast image of an atomic force microscope. NIH-3T3 (3T3) single cells were able to be cultured at 37°C on the patterned surfaces as well as on a PIPAAm surface without pattern, and the detachment of adhered cells was more rapidly from the patterned surface after reducing temperature. Furthermore, the rate of detachment of 3T3 confluent cell sheet on the patterned surface was accelerated, compared with on a conventional PIPAAm surface under the static condition. The rate control of cell sheet recovery should contribute the preservations of cell phenotype and biological functions of cell sheet for applying to clinical trials.

Novel temperature-responsive polymer brushes with carbohydrate residues facilitate selective adhesion and collection of hepatocytes

Temperature-responsive glycopolymer brushes were designed to investigate the effects of grafting architectures of the copolymers on the selective adhesion and collection of hypatocytes. Homo, random and block sequences of N-isopropylacrylamide and 2-lactobionamidoethyl methacrylate were grafted on glass substrates via surface-initiated atom transfer radical polymerization. The galactose/lactose-specific lectin RCA₁₂₀ and HepG2 cells were used to test for specific recognition of the polymer brushes containing galactose residues over the lower critical solution temperatures (LCSTs). RCA₁₂₀ showed a specific binding to the brush surfaces at 37 °C. These brush surfaces also facilitated the adhesion of HepG2 cells at 37 °C under nonserum conditions, whereas no adhesion was observed for NIH-3T3 fibroblasts. When the temperature was decreased to 25 °C, almost all the HepG2 cells detached from the block copolymer brush, whereas the random copolymer brush did not release the cells. The difference in releasing kinetics of cells from the surfaces with different grafting architectures can be explained by the correlated effects of significant changes in LCST, mobility, hydrophilicity and mechanical properties of the grafted polymer chains. These findings are important for designing 'on-off' cell capture/release substrates for various biomedical applications such as selective cell separation.