Electrical Stimulation Modulates the Expression of Multiple Wound Healing Genes in Primary Human Dermal Fibroblasts

Development of a Cell Culture Chamber for Investigating the Therapeutic Effects of Electrical Stimulation on Neural Growth

Natural electric fields exist throughout the body during development and following injury, and, as such, EFs have the potential to be utilized to guide cell growth and regeneration. Electrical stimulation (ES) can also affect gene expression and other cellular behaviors, including cell migration and proliferation. To investigate the effects of electric fields on cells in vitro, a sterile chamber that delivers electrical stimuli is required. Here, we describe the construction of an ES chamber through the modification of an existing lid of a 6-well cell culture plate. Using human SH-SY5Y neuroblastoma cells, we tested the biocompatibility of materials, such as Araldite®, Tefgel™ and superglue, that were used to secure and maintain platinum electrodes to the cell culture plate lid, and we validated the electrical properties of the constructed ES chamber by calculating the comparable electrical conductivities of phosphate-buffered saline (PBS) and cell culture media from voltage and current measurements obtained from the ES chamber. Various electrical signals and durations of stimulation were tested on SH-SY5Y cells. Although none of the signals caused significant cell death, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays revealed that shorter stimulation times and lower currents minimized negative effects. This design can be easily replicated and can be used to further investigate the therapeutic effects of electrical stimulation on neural cells.

Fabrication and Characterization of an Electro-Compacted Collagen/Elastin/Hyaluronic Acid Sheet as a Potential Skin Scaffold

The development of biomimetic structures with integrated extracellular matrix (ECM) components represents a promising approach to biomaterial fabrication. Here, an artificial ECM, comprising the structural protein collagen I and elastin (ELN), as well as the glycosaminoglycan hyaluronan (HA), is reported. Specifically, collagen and ELN are electrochemically aligned to mimic the compositional characteristics of the dermal matrix. HA is incorporated into the electro-compacted collagen-ELN matrices via adsorption and chemical immobilization, to give a final composition of collagen/ELN/HA of 7:2:1. This produces a final collagen/ELN/hyaluronic acid scaffold (CEH) that recapitulates the compositional feature of the native skin ECM. This study analyzes the effect of CEH composition on the cultivation of human dermal fibroblast cells (HDFs) and immortalized human keratinocytes (HaCaTs). It is shown that the CEH scaffold supports dermal regeneration by promoting HDFs proliferation, ECM deposition, and differentiation into myofibroblasts. The CEH scaffolds are also shown to support epidermis growth by supporting HaCaTs proliferation, differentiation, and stratification. A double-layered epidermal-dermal structure is constructed on the CEH scaffold, further demonstrating its ability in supporting skin cell function and skin regeneration.

Revolutionizing Drug Delivery and Therapeutics: The Biomedical Applications of Conductive Polymers and Composites-Based Systems

The first conductive polymers (CPs) were developed during the 1970s as a unique class of organic substances with properties that are electrically and optically comparable to those of inorganic semiconductors and metals while also exhibiting the desirable traits of conventional polymers. CPs have become a subject of intensive research due to their exceptional qualities, such as high mechanical and optical properties, tunable electrical characteristics, ease of synthesis and fabrication, and higher environmental stability than traditional inorganic materials. Although conducting polymers have several limitations in their pure state, coupling with other materials helps overcome these drawbacks. Owing to the fact that various types of tissues are responsive to stimuli and electrical fields has made these smart biomaterials attractive for a range of medical and biological applications. For various applications, including the delivery of drugs, biosensors, biomedical implants, and tissue engineering, electrical CPs and composites have attracted significant interest in both research and industry. These bimodalities can be programmed to respond to both internal and external stimuli. Additionally, these smart biomaterials have the ability to deliver drugs in various concentrations and at an extensive range. This review briefly discusses the commonly used CPs, composites, and their synthesis processes. Further highlights the importance of these materials in drug delivery along with their applicability in various delivery systems.

Electrical Stimulation in Cartilage Tissue Engineering

Electrical stimulation (ES) has been frequently used in different biomedical applications both in vitro and in vivo. Numerous studies have demonstrated positive effects of ES on cellular functions, including metabolism, proliferation, and differentiation. The application of ES to cartilage tissue for increasing extracellular matrix formation is of interest, as cartilage is not able to restore its lesions owing to its avascular nature and lack of cells. Various ES approaches have been used to stimulate chondrogenic differentiation in chondrocytes and stem cells; however, there is a huge gap in systematizing ES protocols used for chondrogenic differentiation of cells. This review focuses on the application of ES for chondrocyte and mesenchymal stem cell chondrogenesis for cartilage tissue regeneration. The effects of different types of ES on cellular functions and chondrogenic differentiation are reviewed, systematically providing ES protocols and their advantageous effects. Moreover, cartilage 3D modeling using cells in scaffolds/hydrogels under ES are observed, and recommendations on reporting about the use of ES in different studies are provided to ensure adequate consolidation of knowledge in the area of ES. This review brings novel insights into the further application of ES in in vitro studies, which are promising for further cartilage repair techniques.

Engineering diabetic human skin equivalent for in vitro and in vivo applications

The prevalence of diabetes is increasing worldwide. Diabetes contributes to 70% of all non-traumatic lower-limb amputations, which are directly caused by diabetic foot ulcers (DFU) that are difficult to heal. Non-healing diabetic ulcers represent one of modern society’s most difficult medical challenges. One of the promising initiatives to treat DFU is the grafting of autologous skin or stimulating the skin cells at the edge of the wound to proliferate and close the wound. The present study was to engineer a diabetic human skin equivalent (DHSE) that contains fibroblasts and keratinocytes extracted from the skin collected from diabetic patients. The DHSE was used to investigate whether exposure to low-intensity electrical stimulation (ES) could promote diabetic cell activity. The ES was generated by a direct current (DC) electric field of 20 or 40 mV/mm. We demonstrated that the fibroblasts and keratinocytes could be extracted from older diabetics, cultured, and used to engineer DHSE. Interestingly, the exposure of DHSE to ES led to a structural improvement through tissue stratification, increased Ki-67 expression, and the deposition of basement membrane proteins (laminin and type IV collagen). The DHSE exposed to ES showed a high level of keratin 5 and 14 expressions in the basal and supra-basal layers. The keratinocyte proliferation was supported by an increased secretion of the keratinocyte growth factor (FGF-7). Exposure to ES decreased the activity of metalloproteinases (MMP) 2 and 9. In conclusion, we extracted keratinocytes and fibroblasts from the skin of diabetic-old donors. These cells were used to engineer skin equivalents and demonstrate that ES can promote diabetic wound healing. This DHSE can be a promising tool for various in vitro studies to understand the wound healing mechanisms under chronic inflammatory conditions such as diabetes. The DHSE could also be used as an autologous substrate to cover the DFU permanently.

Effect of Magnetohydrodynamic on Cutaneous Wound Healing in Rat Model

Background: Exogenous electrical stimulation of the skin may mimic its endogenous bioelectric currents. In this study, a combination of direct current (DC) and magnetic field (MF) was investigated in the excision of the rat wound model. Methods: A circular wound was created on the posterior of the neck, and an electrode was fixed in the wound center. Rats were divided into sham, DC (600 µA), MF (~0.8 T), and magnet-direct current (MDC) groups. The study was conducted in 14 days with 20-min treatment daily. Results: The DC and MDC groups had higher healing percentages (P < 0.01) with mean differences of -13.42 and -15.63, respectively. Direct current on days 2, 5, and 6, and MDC on days 8, 9, 10, 11, 12, and 13 showed higher wound closing. In the DC-treated group, angiogenesis was improved on day 7. In MDC-treated rats, angiogenesis and fibroplasia were improved on day 13. The MF and MDC groups had lower granulation thicknesses on day 7. Granulation thickness increased on day 13 in the MF and MDC groups, while it decreased in the DC group. Direct current treatment improved healing in the first half of the study period, whereas MDC enhanced it in the second half, overtaking DC. From day 7, the magnet group started to overtake the control group slightly in the last four days. Conclusions: To accelerate wound healing, we suggest applying DC in the first days of wounding and MDC in the following days.

Electrical stimulation of titanium to promote stem cell orientation, elongation and osteogenesis

Electrical stimulation of cells allows exogenous electric signals as stimuli to manipulate cell growth, preferential orientation and bone remodelling. In this study, commercially pure titanium discs were utilised in combination with a custom-built bioreactor to investigate the cellular responses of human mesenchymal stem cells via in-vitro functional assays. Finite element analysis revealed the homogeneous delivery of electric field in the bioreactor chamber with no detection of current density fluctuation in the proposed model. The custom-built bioreactor with capacitive stimulation delivery system features long-term stimulation with homogeneous electric field, biocompatible, sterilisable, scalable design and cost-effective in the manufacturing process. Using a continuous stimulation regime of 100 and 200 mV/mm on cp Ti discs, viability tests revealed up to an approximately 5-fold increase of cell proliferation rate as compared to non-stimulated controls. The human mesenchymal stem cells showed more elongated and differentiated morphology under this regime, with evidence of nuclear elongation and cytoskeletal orientation perpendicular to the direction of electric field. The continuous stimulation did not cause pH fluctuations and hydrogen peroxide production caused by Faradic reactions, signifying the suitability for long-term toxic free stimulation as opposed to the commonly used direct stimulation regime. An approximate of 4-fold increase in alkaline phosphatase production and approximately 9-fold increase of calcium deposition were observed on 200 mV/mm exposed samples relative to non-stimulated controls. It is worth noting that early stem cell differentiation and matrix production were observed under the said electric field even without the presence of chemical inductive growth factors. STATEMENT OF SIGNIFICANCE: This manuscript presents a study on combining pure titanium (primarily preferred as medical implant materials) and electrical stimulation in a purpose-built bioreactor with capacitive stimulation delivery system. A continuous capacitive stimulation regime on titanium disc has resulted in enhanced stem cell orientation, nuclei elongation, proliferation and differentiation as compared to non-stimulated controls. We believe that this manuscript creates a paradigm for future studies on the evolution of healthcare treatments in the area of targeted therapy on implantable and wearable medical devices through tailored innovative electrical stimulation approach, thereby influencing therapeutic conductive and electroactive biomaterials research prospects and development.

Ionic liquid functionalized injectable and conductive hyaluronic acid hydrogels for the efficient repair of diabetic wounds under electrical stimulation

The treatment and care of diabetic wounds remains a global challenge due to the the high rates of amputation, recurrence, and mortality. It has been proven that electrical stimulation has...

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers, carbon nanomaterials, or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering, owing to the similar conductivity to human skin, good antioxidant and antibacterial activities, electrically controlled drug delivery, and photothermal effect. However, a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking. In this review, the design and fabrication methods of conductive biomaterials with various structural forms including film, nanofiber, membrane, hydrogel, sponge, foam, and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized. The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies (electrotherapy, wound dressing, and wound assessment) were reviewed. The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound (infected wound and diabetic wound) and for wound monitoring is discussed in detail. The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Redox Polymers for Tissue Engineering

This review will focus on the targeted design, synthesis and application of redox polymers for use in regenerative medicine and tissue engineering. We define redox polymers to encompass a variety of polymeric materials, from the multifunctional conjugated conducting polymers to graphene and its derivatives, and have been adopted for use in the engineering of several types of stimulus responsive tissues. We will review the fundamental properties of organic conducting polymers (OCPs) and graphene, and how their properties are being tailored to enhance material - biological interfacing. We will highlight the recent development of high-resolution 3D fabrication processes suitable for biomaterials, and how the fabrication of intricate scaffolds at biologically relevant scales is providing exciting opportunities for the application of redox polymers for both in-vitro and in-vivo tissue engineering. We will discuss the application of OCPs in the controlled delivery of bioactive compounds, and the electrical and mechanical stimulation of cells to drive behaviour and processes towards the generation of specific functional tissue. We will highlight the relatively recent advances in the use of graphene and the exploitation of its physicochemical and electrical properties in tissue engineering. Finally, we will look forward at the future of organic conductors in tissue engineering applications, and where the combination of materials development and fabrication processes will next unite to provide future breakthroughs.

Conductive Materials for Healing Wounds: Their Incorporation in Electroactive Wound Dressings, Characterization, and Perspectives

The use of conductive materials to promote the activity of electrically responsive cells is an effective means of accelerating wound healing. This article focuses on recent advancements in conductive materials, with emphasis on overviewing their incorporation with non-conducting polymers to fabricate electroactive wound dressings. The characteristics of these electroactive dressings are deliberated, and the mechanisms on how they accelerate the wound healing process are discussed. Potential directions for the future development of electroactive wound dressings and their potential in monitoring the course of wound healing in vivo concomitantly are also proposed.

Conductive Antibacterial Hemostatic Multifunctional Scaffolds Based on Ti3C2Tx MXene Nanosheets for Promoting Multidrug-Resistant Bacteria-Infected Wound Healing

Chronic bacterial-infected wound healing/skin regeneration remains a challenge due to drug resistance and the poor quality of wound repair. The ideal strategy is combating bacterial infection, while facilitating satisfactory wound healing. However, the reported strategy hardly achieves these two goals simultaneously without the help of antibiotics or bioactive molecules. In this work, a two-dimensional (2D) Ti₃C₂T_x MXene with excellent conductivity, biocompatibility, and antibacterial ability was applied in developing multifunctional scaffolds (HPEM) for methicillin-resistant Staphylococcus aureus (MRSA)-infected wound healing. HPEM scaffolds were fabricated by the reaction between the poly(glycerol-ethylenimine), Ti₃C₂T_x MXene@polydopamine (MXene@PDA) nanosheets, and oxidized hyaluronic acid (HCHO). HPEM scaffolds presented multifunctional properties containing self-healing behavior, electrical conductivity, tissue-adhesive feature, antibacterial activity especially for MRSA resistant to many commonly used antibiotics (antibacterial efficiency was 99.03%), and rapid hemostatic capability. HPEM scaffolds enhanced the proliferation of normal skin cells with negligible toxicity. Additionally, HPEM scaffolds obviously accelerated the MRSA-infected wound healing (wound closure ratio was 96.31%) by efficient anti-inflammation effects, promoting cell proliferation, and the angiogenic process, stimulating granulation tissue formation, collagen deposition, vascular endothelial differentiation, and angiogenesis. This study indicates the important role of multifunctional 2D MXene@PDA nanosheets in infected wound healing. HPEM scaffolds with multifunctional properties provide a potential strategy for MRSA-infected wound healing/skin regeneration.

Injectable Electrical Conductive and Phosphate Releasing Gel with Two-Dimensional Black Phosphorus and Carbon Nanotubes for Bone Tissue Engineering

Injectable hydrogels have unique advantages for the repair of irregular tissue defects. In this study, we report a novel injectable carbon nanotube (CNT) and black phosphorus (BP) gel with enhanced mechanical strength, electrical conductivity, and continuous phosphate ion release for tissue engineering. The gel utilized biodegradable oligo(poly(ethylene glycol) fumarate) (OPF) polymer as the cross-linking matrix, with the addition of cross-linkable CNT-poly(ethylene glycol)-acrylate (CNTpega) to grant mechanical support and electric conductivity. Two-dimensional (2D) black phosphorus nanosheets were also infused to aid in tissue regeneration through the steady release of phosphate that results from environmental oxidation of phosphorus in situ. This newly developed BP-CNTpega-gel was found to enhance the adhesion, proliferation, and osteogenic differentiation of MC3T3 preosteoblast cells. With electric stimulation, the osteogenesis of preosteoblast cells was further enhanced with elevated expression of several key osteogenic pathway genes. As monitored with X-ray imaging, the BP-CNTpega-gel demonstrated excellent in situ gelation and cross-linking to fill femur defects, vertebral body cavities, and posterolateral spinal fusion sites in the rabbit. Together, these results indicate that this newly developed injectable BP-CNTpega-gel owns promising potential for future bone and broad types of tissue engineering applications.

A modified cholera toxin B subunit containing an ER retention motif enhances colon epithelial repair via an unfolded protein response

Cholera toxin B subunit (CTB) exhibits broad-spectrum biologic activity upon mucosal administration. Here, we found that a recombinant CTB containing an endoplasmic reticulum (ER) retention motif (CTB-KDEL) induces colon epithelial wound healing in colitis via the activation of an unfolded protein response (UPR) in colon epithelial cells. In a Caco2 cell wound healing model, CTB-KDEL, but not CTB or CTB-KDE, facilitated cell migration via interaction with the KDEL receptor, localization in the ER, UPR activation, and subsequent TGF-β signaling. Inhibition of the inositol-requiring enzyme 1/X-box binding protein 1 arm of UPR abolished the cell migration effect of CTB-KDEL, indicating that the pathway is indispensable for the activity. CTB-KDEL's capacity to induce UPR and epithelial restitution or wound healing was corroborated in a dextran sodium sulfate-induced acute colitis mouse model. Furthermore, CTB-KDEL induced a UPR, up-regulated wound healing pathways, and maintained viable crypts in colon explants from patients with inflammatory bowel disease (IBD). In summary, CTB-KDEL exhibits unique wound healing effects in the colon that are mediated by its localization to the ER and subsequent activation of UPR in epithelial cells. The results provide implications for a novel therapeutic approach for mucosal healing, a significant unmet need in IBD treatment.-Royal, J. M., Oh, Y. J., Grey, M. J., Lencer, W. I., Ronquillo, N., Galandiuk, S., Matoba, N. A modified cholera toxin B subunit containing an ER retention motif enhances colon epithelial repair via an unfolded protein response.

Electrical impulse effects on degenerative human annulus fibrosus model to reduce disc pain using micro-electrical impulse-on-a-chip

Electrical stimulation of cells and tissues for therapeutic benefit is a well-established method. Although animal studies can emulate the complexity of an organism’s physiology, lab-on-a-chip platforms provide a suitable primary model for follow-up animal studies. Thus, inexpensive and easy-to-use platforms for in vitro human cell studies are required. In the present study, we designed a micro-electrical impulse (micro-EI)-on-a-chip (micro-EI-chip), which can precisely control electron density and adjust the frequency based on a micro-EI. The micro-EI-chip can stimulate cells at various micro-EI densities (0–500 mV/mm) and frequencies (0–300 Hz), which enables multiple co-culture of different cell types with or without electrical stimulation. As a proof-of-concept study, a model involving degenerative inflamed human annulus fibrosus (hAF) cells was established in vitro and the effects of micro-EI on inflamed hAF cells were evaluated using the micro-EI-chip. Stimulation of the cells (150 mV/mm at 200 Hz) inhibited the secretion of inflammatory cytokines and downregulated the activities of extracellular matrix-modifying enzymes and matrix metalloproteinase-1. These results show that micro-EI stimulation could affect degenerative diseases based on inflammation, implicating the micro-EI-chip as being useful for basic research of electroceuticals.

A Disposable Photovoltaic Patch Controlling Cellular Microenvironment for Wound Healing

Electrical stimulation (ES) is known to affect the wound healing process by modulating skin cell behaviors. However, the conventional clinical devices that can generate ES for promoting wound healing require patient hospitalization due to large-scale of the extracorporeal devices. Herein, we introduce a disposable photovoltaic patch that can be applied to skin wound sites to control cellular microenvironment for promoting wound healing by generating ES. In vitro experiment results show that exogenous ES could enhance cell migration, proliferation, expression of extracellular matrix proteins, and myoblast differentiation of fibroblasts which are critical for wound healing. Our disposable photovoltaic patches were attached to the back of skin wound induced mice. Our patch successfully provided ES, generated by photovoltaic energy harvested from the organic solar cell under visible light illumination. In vivo experiment results show that the patch promoted cutaneous wound healing via enhanced host-inductive cell proliferation, cytokine secretion, and protein synthesis which is critical for wound healing process. Unlike the current treatments for wound healing that engage passive healing processes and often are unsuccessful, our wearable photovoltaic patch can stimulate regenerative activities of endogenous cells and actively contribute to the wound healing processes.

Electrical Stimulation Increases Random Migration of Human Dermal Fibroblasts

Exogenous electrical stimulation (ES) has been investigated as a therapy for chronic wounds, as the skin produces currents and electrical fields (EFs) during wound healing. ES therapies operate by applying small EFs to the skin to mimic the transepithelial potentials that occur during the granulation phase of wound healing. Here, we investigated the effect of short duration (10 min) ES on the migration of HDFs using various magnitudes of physiologically relevant EFs. We modeled cutaneous injury by culturing HDFs in custom chambers that allowed the application of ES and then performed timelapse microscopy on a standard wound model. Using MATLAB to process cell coordinate data, we determined that the cells were migrating randomly and fit mean squared displacement data to the persistent random walk equation using nonlinear least squares regression analysis. Results indicated that application of 25-100 mV/mm DC EFs to HDFs on either uncoated or FN-coated surfaces demonstrated no significant changes in viability or proliferation. Of significance is that the HDFs increased random migration behavior under some ES conditions even after 10 min, providing a mechanism to enhance wound healing.

Angiogenic effects of low-intensity cathodal direct current on ischemic diabetic foot ulcers: A randomized controlled trial

AIMS

This study investigated the effect of low-intensity cathodal direct current (CDC) of electrical stimulation (ES) on the release of hypoxic inducible factor-1α (HIF-1α), nitric oxide (NO), vascular endothelial growth factor (VEGF), and soluble VEGF receptor-2 (sVEGFR-2) in the wound fluid of ischemic diabetic foot ulcers (DFUs).

METHODS

This study was a randomized, single-blind, placebo-controlled trial. Thirty type 2 diabetes patients with ischemic foot ulcerations were randomly assigned to receive either low-intensity CDC at sensory threshold (ES group, n=15) or placebo treatment (control group, n=15) for 1h/day, 3days/week, for 4weeks (12 sessions). After debridement during the first and twelfth treatment sessions, wound fluid was collected before and after ES application to determine the levels of HIF-1α, NO, VEGF, and sVEGFR-2. Wound surface area (WSA) was measured at the first, sixth, and twelfth sessions.

RESULTS

At the first session, after ES application, wound-fluid levels of HIF-1α were significantly increased (+61.98pg/mL) compared to the control group (-3.85pg/mL, P=0.01). After ES application at the first and twelfth sessions, wound-fluid levels of VEGF were also significantly increased (+36.77 and +39.57pg/mL, respectively) compared to the control group (+4.15 and +0.15pg/mL, P=0.007 and P=0.019, respectively). There was no significant effect on NO and sVEGFR-2 levels between the groups.

CONCLUSIONS

Low-intensity CDC has positive effects on the release of HIF-1α and VEGF in the wound area of ischemic DFUs. Furthermore, our results suggest that applying ES to ischemic DFUs can be a promising way to promote angiogenesis and to achieve better outcomes in diabetic wound healing.

Modulation of ROS levels in fibroblasts by altering mitochondria regulates the process of wound healing

Mitochondria are the major source of reactive oxygen species (ROS) in fibroblasts which are thought to be crucial regulators of wound healing with a potential to affect the expression of nuclear genes involved in this process. ROS generated by mitochondria are involved in all stages of tissue repair process but the regulation of ROS-generating system in fibroblasts still remains poorly understood. The purpose of this study was to better understand molecular mechanisms of how the regulation of ROS levels generated by mitochondria may influence the process of wound repair. Cybrid model system of mtDNA variations was used to study the functional consequences of altered ROS levels on wound healing responses in a uniform nuclear background of cultured ρ(0) fibroblasts. Mitochondrial ROS in cybrids were modulated by antioxidants that quench ROS to examine their ability to close the wound. Real-time PCR arrays were used to investigate whether ROS generated by specific mtDNA variants have the ability to alter expression of some key nuclear-encoded genes central to the wound healing response and oxidative stress. Our data suggest levels of mitochondrial ROS affect expression of some nuclear encoded genes central to wound healing response and oxidative stress and modulation of mitochondrial ROS by antioxidants positively affects in vitro process of wound closure. Thus, regulation of mitochondrial ROS-generating system in fibroblasts can be used as effective natural redox-based strategy to help treat non-healing wounds.

Keratinocyte Growth Factor Regulation of Aryl Hydrocarbon Receptor Activation in Colorectal Cancer Cells

BACKGROUND

Keratinocyte growth factor (KGF) stimulates normal growth, development and intestinal epithelial cell proliferation. Cyclin D1 promotes the cell cycle by inhibiting retinoblastoma protein (RB1). The activated aryl hydrocarbon receptor (AhR) has an important influence on the development of tumors through its interactions with the cell cycle.

AIM

The aim of the present study was to explore a new role for AhR in KGF-induced colon cancer cell growth.

MATERIALS AND METHODS

Real-time PCR, western blot or immunofluorescence analysis were used to detect the expression of KGF, AhR, cyclin D1 and CYP1A1. Immunohistochemistry was used to observe the localization of AhR. MTT assay and flow cytometric analyses were performed to measure cell viability and the cell cycle.

RESULTS

Real-time PCR analysis revealed that KGF, AhR, and CYP1A1 mRNAs were overexpressed in colorectal cancer tissues. Meanwhile, overexpression of AhR was primarily observed in epithelial cells. In in vitro assay, KGF promoted colon cancer cell growth, as well as up-regulated and activated AhR. At the same time, AhR-knockdown colon cancer cells were less responsive to KGF. Western blot analysis, real-time PCR, or immunofluorescence data indicated that cyclin D1 expression was up-regulated by KGF but this up-regulation was compromised when AhR was silenced, and the cell cycle was arrested in the G0/G1 stage in these cells.

CONCLUSIONS

Our study suggests that KGF, AhR, and CYP1A1 are overexpressed in colorectal cancer tissues. Moreover, we reveal a new mechanism by which KGF promotes cell proliferation through the AhR-cyclin D1 pathway in colon cancer cells.

Microfabrication of scaffold-free tissue strands for three-dimensional tissue engineering

In this note, we report a practical and efficient method based on a coaxial extrusion and microinjection technique for biofabrication of scaffold-free tissue strands. Tissue strands were obtained using tubular alginate conduits as mini-capsules with well-defined permeability and mechanical properties, where their removal by ionic decrosslinking allowed the formation of scaffold-free cell aggregates in the form of cylindrical strands with well-defined morphology and geometry. Rat dermal fibroblasts and mouse insulinoma beta TC3 cells were used to fabricate both single-cellular and heterocellular tissue strands with high cell viability, self-assembling capability and the ability to express cell-specific functional markers. By taking advantage of tissue self-assembly, we succeeded in guiding the fusion of tissue strands to fabricate larger tissue patches. The presented approach enables fabrication of cell aggregates with controlled dimensions allowing highly long strands, which can be used for various applications, including fabrication of scale-up complex tissues and of tissue models for drug screening and cancer studies.