Micropatterning Extracellular Matrix Proteins on Electrospun Fibrous Substrate Promote Human Mesenchymal Stem Cell Differentiation Toward Neurogenic Lineage

Effect of Collector Rotational Speed on the Morphology and Structure of Solution Blow Spun Polylactic Acid (PLA)

Apart from structure and composition, morphology plays a significant role in influencing the performance of materials in terms of both bulk and surface behavior. In this work, polylactic acid (PLA) constituted by submicrometric fibers is prepared. Using a modified electrospinning (ES) device to carry out solution blow spinning (SBS), the fibrillar morphology is modified, with the aim to induce variations in the properties of the material. The modification of the ES device consists of the incorporation of a source of pressurized gas (air) and a 3D-printed nozzle of our own design. For this work, the morphology of the PLA submicrometric fibers is modified by varying the rotational speed of the collector in order to understand its influence on different properties and, consequently, on the performance of the material. The rotational speed of a cylindrical collector (250, 500, 1000 and 2000 rpm) is considered as variable for changing the morphology. Morphological study of the materials was performed using scanning electron microscopy and image analysis carried out with ImageJ 1.54f software. Besides a morphology study, structural characterization by Fourier transformed infrared spectroscopy using attenuated total reflectance of prepared materials is carried out. Finally, the morphology and structure of produced PLA fibrous mats were correlated with the analysis of mechanical properties, wettability behavior and adhesion of DH5-α E. coli bacteria. It is of interest to highlight how small morphological and chemical structure variations can lead to important changes in materials' performance. These changes include, for example, those above 30% in some mechanical parameters and clear variations in bacterial adhesion capacity.

Electrical Stimulation of Human Mesenchymal Stem Cells on Conductive Substrates Promotes Neural Priming

Electrical stimulation (ES) within a conductive scaffold is potentially beneficial in encouraging the differentiation of stem cells toward a neuronal phenotype. To improve stem cell-based regenerative therapies, it is essential to use electroconductive scaffolds with appropriate stiffnesses to regulate the amount and location of ES delivery. Herein, biodegradable electroconductive substrates with different stiffnesses are fabricated from chitosan-grafted-polyaniline (CS-g-PANI) copolymers. Human mesenchymal stem cells (hMSCs) cultured on soft conductive scaffolds show a morphological change with significant filopodial elongation after electrically stimulated culture along with upregulation of neuronal markers and downregulation of glial markers. Compared to stiff conductive scaffolds and non-conductive CS scaffolds, soft conductive CS-g-PANI scaffolds promote increased expression of microtubule-associated protein 2 (MAP2) and neurofilament heavy chain (NF-H) after application of ES. At the same time, there is a decrease in the expression of the glial markers glial fibrillary acidic protein (GFAP) and vimentin after ES. Furthermore, the elevation of intracellular calcium [Ca2+ ] during spontaneous, cell-generated Ca2+ transients further suggests that electric field stimulation of hMSCs cultured on conductive substrates can promote a neural-like phenotype. The findings suggest that the combination of the soft conductive CS-g-PANI substrate and ES is a promising new tool for enhancing neuronal tissue engineering outcomes.

Harvest of Cell-Only Muscle Fibers Using Thermally Expandable Hydrogels with Adhesive Patterns

Muscle tissue engineering has been the focus of extensive research due to its potential for numerous medical applications, including ex vivo actuator development and clinical treatments. In this study, we developed a method for harvesting muscle fiber in a floatable and translocatable manner utilizing thermally expandable hydrogels with a chemically patterned polydopamine (PD) layer generated by microcontact printing (μCP). The μCP of PD on the hydrogel facilitated the formation of stripe patterns with varying widths of printed/nonprinted area (50/50, 100/100, and 200/200 μm). The spatially controlled adhesion of C2C12 myoblasts on the PD patterns produced clearly distinguishable muscle fibers, and translocated muscle fibers exhibited preserved extracellular matrix and junction proteins. Furthermore, the development of anisotropic arrangements and mature myotubes within the fibers suggests the potential for functional control of engineered muscle tissues. Overall, the muscle fiber harvesting method developed herein is suitable for both translocation and floating and is a promising technique for muscle tissue engineering as it mimics the structure-function relationship of natural tissue.

Soft nano and microstructures for the photomodulation of cellular signaling and behavior

Photoresponsive soft materials are everywhere in the nature, from human's retina tissues to plants, and have been the inspiration for engineers in the development of modern biomedical materials. Light as an external stimulus is particularly attractive because it is relatively cheap, noninvasive to superficial biological tissues, can be delivered contactless and offers high spatiotemporal control. In the biomedical field, soft materials that respond to long wavelength or that incorporate a photon upconversion mechanism are desired to overcome the limited UV-visible light penetration into biological tissues. Upon light exposure, photosensitive soft materials respond through mechanisms of isomerization, crosslinking or cleavage, hyperthermia, photoreactions, electrical current generation, among others. In this review, we discuss the most recent applications of photosensitive soft materials in the modulation of cellular behavior, for tissue engineering and regenerative medicine, in drug delivery and for phototherapies.

Adipose mesenchymal stem cell-based tissue engineering mesh with sustained bFGF release to enhance tissue repair

Pelvic organ prolapse (POP) harms the quality of life of elderly patients. Transvaginal polypropylene mesh repair for POP was a frequently reported complication and was banned by the FDA in 2019. New therapeutic strategies are urgently required, and tissue engineering technology could be a novel therapy. Here, we developed a tissue engineering mesh out of three components: silk fibroin (SF) knitted mesh loaded with basic fibroblast growth factor (bFGF) and adipose-derived stem cells (ADSCs). We used coaxial electrospinning technology to achieve local bFGF release to promote regeneration. Additionally, ADSCs were loaded to demonstrate their paracrine ability of immune regulation and angiogenesis. Meanwhile, knitted silk fibroin mesh provided mechanical support. In vitro, SF/bFGF/ADSC tissue engineering mesh can stably release bFGF and has good biocompatibility, promoting cell proliferation and extracellular matrix synthesis. Six months after the SF/bFGF/ADSC tissue engineering mesh was implanted in a SD rat model, extracellular matrix reorganization, angiogenesis, and immunomodulatory effect, as well as mechanical properties of the implanting position were improved. Hence, SF/bFGF/ADSC tissue engineering mesh could be regarded as a promising option with excellent collagen synthesis, low foreign body response, and early angiogenic ability, providing potential ideas for POP treatment.

Control of stem cell differentiation by using extrinsic photobiomodulation in conjunction with cell adhesion pattern

The induction and direction of stem cell differentiation into needed cell phenotypes is the central pillar of tissue engineering for repairing damaged tissues or organs. Conventionally, a special recipe of chemical factors is formulated to achieve this purpose for each specific target cell type. In this work, it is demonstrated that the combination of extrinsic photobiomodulation and collagen-covered microislands could be used to induce differentiation of Wharton’s jelly mesenchymal stem cells (WJ-MSCs) with the differentiation direction dictated by the specific island topography without use of chemical factors. Both neurogenic differentiation and adipogenic differentiation could be attained with a rate surpassing that using chemical factors. Application of this method to other cell types is possible by utilizing microislands with a pattern tailored particularly for each specific cell type, rendering it a versatile modality for initiating and guiding stem cell differentiation.

Electrospun Fiber Scaffolds for Engineering Glial Cell Behavior to Promote Neural Regeneration

Electrospinning is a fabrication technique used to produce nano- or micro- diameter fibers to generate biocompatible, biodegradable scaffolds for tissue engineering applications. Electrospun fiber scaffolds are advantageous for neural regeneration because they mimic the structure of the nervous system extracellular matrix and provide contact guidance for regenerating axons. Glia are non-neuronal regulatory cells that maintain homeostasis in the healthy nervous system and regulate regeneration in the injured nervous system. Electrospun fiber scaffolds offer a wide range of characteristics, such as fiber alignment, diameter, surface nanotopography, and surface chemistry that can be engineered to achieve a desired glial cell response to injury. Further, electrospun fibers can be loaded with drugs, nucleic acids, or proteins to provide the local, sustained release of such therapeutics to alter glial cell phenotype to better support regeneration. This review provides the first comprehensive overview of how electrospun fiber alignment, diameter, surface nanotopography, surface functionalization, and therapeutic delivery affect Schwann cells in the peripheral nervous system and astrocytes, oligodendrocytes, and microglia in the central nervous system both in vitro and in vivo. The information presented can be used to design and optimize electrospun fiber scaffolds to target glial cell response to mitigate nervous system injury and improve regeneration.

Repair and regeneration of small intestine: A review of current engineering approaches

The small intestine (SI) is difficult to regenerate or reconstruct due to its complex structure and functions. Recent developments in stem cell research, advanced engineering technologies, and regenerative medicine strategies bring new hope of solving clinical problems of the SI. This review will first summarize the structure, function, development, cell types, and matrix components of the SI. Then, the major cell sources for SI regeneration are introduced, and state-of-the-art biofabrication technologies for generating engineered SI tissues or models are overviewed. Furthermore, in vitro models and in vivo transplantation, based on intestinal organoids and tissue engineering, are highlighted. Finally, current challenges and future perspectives are discussed to help direct future applications for SI repair and regeneration.

Effects of Fiber Alignment and Coculture with Endothelial Cells on Osteogenic Differentiation of Mesenchymal Stromal Cells

Vascularization is a critical process during bone regeneration. The lack of vascular networks leads to insufficient oxygen and nutrients supply, which compromises the survival of regenerated bone. One strategy for improving the survival and osteogenesis of tissue-engineered bone grafts involves the coculture of endothelial cells (ECs) with mesenchymal stromal cells (MSCs). Moreover, bone regeneration is especially challenging due to its unique structural properties with aligned topographical cues, with which stem cells can interact. Inspired by the aligned fibrillar nanostructures in human cancellous bone, we fabricated polycaprolactone (PCL) electrospun fibers with aligned and random morphology, cocultured human MSCs with human umbilical vein ECs (HUVECs), and finally investigated how these two factors modulate osteogenic differentiation of human MSCs (hMSCs). After optimizing cell ratio, a hMSCs/HUVECs ratio (90:10) was considered to be the best combination for osteogenic differentiation. Coculture results showed that hMSCs and HUVECs adhered to and proliferated well on both scaffolds. The aligned structure of PCL fibers strongly influenced the morphology and orientation of hMSCs and HUVECs; however, fiber alignment was observed to not affect alkaline phosphate (ALP) activity or mineralization of hMSCs compared with random scaffolds. More importantly, cocultured cells on both random and aligned scaffolds had significantly higher ALP activities than monoculture groups, which indicated that coculture with HUVECs provided a larger relative contribution to the osteogenesis of hMSCs compared with fiber alignment. Taken together, we conclude that coculture of hMSCs with ECs is an effective strategy to promote osteogenesis on electrospun scaffolds, and aligned fibers could be introduced to regenerate bone tissues with oriented topography without significant deleterious effects on hMSCs differentiation. This study shows the ability to grow oriented tissue-engineered cocultures with significant increases in osteogenesis over monoculture conditions. Impact statement This work demonstrates an effective method of enhancing osteogenesis of mesenchymal stromal cells on electrospun scaffolds through coculturing with endothelial cells. Furthermore, we provide the optimized conditions for cocultures on electrospun fibrous scaffolds and engineered bone tissues with oriented topography on aligned fibers. This study demonstrates promising findings for growing oriented tissue-engineered cocultures with significant increase in osteogenesis over monoculture conditions.

Hybrid Nanofiber Scaffold-Based Direct Conversion of Neural Precursor Cells/Dopamine Neurons

The concept of cellular reprogramming was developed to generate induced neural precursor cells (iNPCs)/dopaminergic (iDA) neurons using diverse approaches. Here, we investigated the effects of various nanoscale scaffolds (fiber, dot, and line) on iNPC/iDA differentiation by direct reprogramming. The generation and maturation of iDA neurons (microtubule-associated protein 2-positive and tyrosine hydroxylase-positive) and iNPCs (NESTIN-positive and SOX2-positive) increased on fiber and dot scaffolds as compared to that of the flat (control) scaffold. This study demonstrates that nanotopographical environments are suitable for direct differentiation methods and may improve the differentiation efficiency.

Ultraviolet Functionalization of Electrospun Scaffolds to Activate Fibrous Runways for Targeting Cell Adhesion

A critical challenge in scaffold design for tissue engineering is recapitulating the complex biochemical patterns that regulate cell behavior in vivo. In this work, we report the adaptation of a standard sterilization methodology-UV irradiation-for patterning the surfaces of two complementary polymeric electrospun scaffolds with oxygen cues able to efficiently immobilize biomolecules. Independently of the different polymer chain length of poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymers and PEOT/PBT ratio, it was possible to easily functionalize specific regions of the scaffolds by inducing an optimized and spatially controlled adsorption of proteins capable of boosting the adhesion and spreading of cells along the activated fibrous runways. By allowing an efficient design of cell attachment patterns without inducing any noticeable change on cell morphology nor on the integrity of the electrospun fibers, this procedure offers an affordable and resourceful approach to generate complex biochemical patterns that can decisively complement the functionality of the next generation of tissue engineering scaffolds.

Epithelial-mesenchymal transition of cancer cells using bioengineered hybrid scaffold composed of hydrogel/3D-fibrous framework

Cancer cells undergoing epithelial-mesenchymal transition (EMT) acquire stem cell-like phenotype associated with malignant behaviour, chemoresistance, and relapse. Current two-dimensional (2D) in-vitro culture models of tumorigenesis are inadequate to replicate the complexity of in-vivo microenvironment. Therefore, the generation of functional three-dimensional (3D) constructs is a fundamental prerequisite to form multi-cellular tumour spheroids for studying basic pathological mechanisms. In this study, we focused on two major points (i) designing and fabrication of 3D hybrid scaffolds comprising electrospun fibers with cancer cells embedded within hydrogels, and (ii) determining the potential roles of 3D hybrid scaffolds associated with EMT in cancer progression and metastasis. Our findings revealed that 3D hybrid scaffold enhances cell proliferation and induces cancer cells to undergo EMT, as demonstrated by significant up-regulation of EMT associated transcriptional factors including Snail1, Zeb1, and Twist2; and mesenchymal markers whereas epithelial marker, E-Cadherin was downregulated. Remarkably, this induction is independent of cancer cell-type as similar results were obtained for breast cancer cells, MDA-MB-231 and gastric cancer cells, MKN74. Moreover, the hybrid scaffolds enrich aggressive cancer cells with stem cell properties. We showed that our 3D scaffolds could trigger EMT of cancer cells which could provide a useful model for studying anticancer therapeutics against metastasis.

Migration and Phenotype Control of Human Dermal Fibroblasts by Electrospun Fibrous Substrates

Electrospun fibrous matrices, mimicking extracellular matrix (ECM) hierarchical structures, are potential scaffolds for wound healing. To design functional scaffolds, it is important to explore the interactions between scaffold topographic features and cellular responses, especially directional migration and phenotypic changes, which are critical functional aspects during wound healing. Here, accelerated and persistent migration of human dermal fibroblasts (HDFs) is observed on fibers with aligned orientation. Furthermore, aligned fibers can induce fibroblast-to-myofibroblast differentiation of HDFs. During wound healing, the presence of myofibroblasts advances wound repair by rendering contractile force and ECM deposition within the early and middle courses, but its continuous persistence in the later event may not be desired due to the contribution in pathological scarring. To tune the balance, it is noted in this work that the introduction of matricellular protein angiopoietin-like 4 (ANGPTL4) is capable of reversing the phenotypic alteration induced by aligned fibers, in a time-dependent manner. These results indicate fibrous matrices with oriented configuration are functional in mediating directional cell migration and phenotypic change. The discoveries further suggest that tissue-engineered fibrous grafts with precise alignment modulation and ANGPTL4 releasing properties may thus be promising to promote wound repair with minimizing scar formation.

Combining Stem Cells and Biomaterial Scaffolds for Constructing Tissues and Cell Delivery

Combining stem cells with biomaterial scaffolds serves as a promising strategy for engineering tissues for both in vitro and in vivo applications. This updated review details commonly used biomaterial scaffolds for engineering tissues from stem cells. We first define the different types of stem cells and their relevant properties and commonly used scaffold formulations. Next, we discuss natural and synthetic scaffold materials typically used when engineering tissues, along with their associated advantages and drawbacks and gives examples of target applications. New approaches to engineering tissues, such as 3D bioprinting, are described as they provide exciting opportunities for future work along with current challenges that must be addressed. Thus, this review provides an overview of the available biomaterials for directing stem cell differentiation as a means of producing replacements for diseased or damaged tissues.

Maskless Arrayed Nanofiber Mats by Bipolar Pyroelectrospinning

The numerous advantages of micro- and nanostructures produced by electrospinning (ES) have stimulated enormous interest in this technology with potential application in several fields. However, ES still has some limitations in controlling the geometrical arrangement of the fiber mats so that expensive and time-consuming technologies are usually employed for producing ordered geometries. Here we present a technique that we call "bipolar pyroelectrospinning" (b-PES) for generating ordered arrays of fiber mats in a direct manner by using the bipolar pyroelectric field produced by a periodically poled lithium niobate crystal (PPLN). The b-PES is free from expensive electrodes, nozzles, and masks because it makes use simply of the structured pyroelectric field produced by the PPLN crystal used as collector. The results show clearly the reliability of the technique in producing a wide variety of arrayed fiber mats that could find application in bioengineering or many other fields. Preliminary results of live cells patterning under controlled geometrical constraints is also reported and discussed in order to show potential exploitation as a scaffold in tissue engineering.

Differential and Interactive Effects of Substrate Topography and Chemistry on Human Mesenchymal Stem Cell Gene Expression

Variations in substrate chemistry and the micro-structure were shown to have a significant effect on the biology of human mesenchymal stromal cells (hMSCs). This occurs when differences in the surface properties indirectly modulate pathways within numerous signaling networks that control cell fate. To understand how the surface features affect hMSC gene expression, we performed RNA-sequencing analysis of bone marrow-derived hMSCs cultured on tissue culture-treated polystyrene (TCP) and poly(l-lactide) (PLLA) based substrates of differing topography (Fl: flat and Fs: fibrous) and chemistry (Pr: pristine and Am: aminated). Whilst 80% of gene expression remained similar for cells cultured on test substrates, the analysis of differentially expressed genes (DEGs) revealed that surface topography significantly altered gene expression more than surface chemistry. The Fl and Fs topologies introduced opposite directional alternations in gene expression when compared to TCP control. In addition, the effect of chemical treatment interacted with that of topography in a synergistic manner with the Pr samples promoting more DEGs than Am samples in all gene ontology function groups. These findings not only highlight the significance of the culture surface on regulating the overall gene expression profile but also provide novel insights into cell-material interactions that could help further design the next-generation biomaterials to facilitate hMSC applications. At the same time, further studies are required to investigate whether or not the observations noted correlate with subsequent protein expression and functionality of cells.

Sub-micrometer Sized, 3D-Surface-attached Polymer Networks by Microcontact Printing: Using UV-Crosslinking Efficiency to Tune Structure Height

The lateral dimensions of micro- and nanostructures obtained by microcontact printing (μCP) can be easily varied by selecting stamps with the desired spacing and pattern. However, the height of these structures cannot be tuned as easily, and in most cases only 2D structures are obtained. Here, we show how the chemical cross-linking properties of polymer inks designed for μCP can be used to obtain 3D structures with heights ranging from 3 to 750 nm using the same μCP stamps. This is technologically relevant because the ink concentration affects the quality and resolution of the printed image, and therefore can only be varied in a certain range. By exploiting the cross-linking efficiency to tune the height, an additional parameter is available to reach the desired structure height without compromising the image quality. The inks were made from copolymers containing a low percentage of different UV cross-linkable repeat units: nitrobenzoxadiazole (NBD), coumarin (COU), and/or benzophenone (BP). The base polymer of the here presented model system was an antimicrobially active poly(oxanorbornene) (SMAMP), however the concept should be transferable to many other polymer backbones. We describe the fabrication and characterization of the printed micro- and nanostructures made from pure SMAMP, NBD-SMAMP, coumarin-SMAMP, BP-SMAMP, BP-NBD-SMAMP and BP-coumarin-SMAMP polymer inks. The photo-dimerization of COU during UV irradiation at λ = 254 nm was confirmed by UV-Vis spectroscopy. Since NBD and COU are fluorescent, the polymer could be visualized by fluorescence microscopy. Additionally, their height profiles were measured by atomic force microscopy (AFM). The heights of the 3D surface-attached polymer networks obtained from the here presented polymer inks correlated with the gel-content of the corresponding unstructured polymer layers, and thus with the cross-linking efficiency of the NBD, COU and BP cross-linkers. Due to being covalently cross-linked, these 3D-surface attached polymer structures were solvent-stable and stable in aqueous surroundings.

Functional and Biomimetic Materials for Engineering of the Three-Dimensional Cell Microenvironment

The cell microenvironment has emerged as a key determinant of cell behavior and function in development, physiology, and pathophysiology. The extracellular matrix (ECM) within the cell microenvironment serves not only as a structural foundation for cells but also as a source of three-dimensional (3D) biochemical and biophysical cues that trigger and regulate cell behaviors. Increasing evidence suggests that the 3D character of the microenvironment is required for development of many critical cell responses observed in vivo, fueling a surge in the development of functional and biomimetic materials for engineering the 3D cell microenvironment. Progress in the design of such materials has improved control of cell behaviors in 3D and advanced the fields of tissue regeneration, in vitro tissue models, large-scale cell differentiation, immunotherapy, and gene therapy. However, the field is still in its infancy, and discoveries about the nature of cell-microenvironment interactions continue to overturn much early progress in the field. Key challenges continue to be dissecting the roles of chemistry, structure, mechanics, and electrophysiology in the cell microenvironment, and understanding and harnessing the roles of periodicity and drift in these factors. This review encapsulates where recent advances appear to leave the ever-shifting state of the art, and it highlights areas in which substantial potential and uncertainty remain.

Tailored release of triiodothyronine and retinoic acid from a spatio-temporally fabricated nanofiber composite instigating neuronal differentiation

Regeneration of the central and peripheral nervous system is challenging since the functional restoration of injured nerves is an incredible task. The fabrication of an ideal nerve guide that fulfills the requirement to regenerate nerve tissue is a herculean challenge requiring a combination of both biochemical and topographical cues. The present study explores the combinatorial effect of aligned nanofibers and the regulated delivery of triiodothyronine and retinoic acid on nerve regeneration. A sequential release mechanism is adopted in fabricating the nanofiber scaffold, with triiodothyronine incorporated into the nanofiber shell ensuring its prior release, followed by retinoic acid (entrapped within zein nanoparticles) from the core. The composite nanofibers thus fabricated possess excellent mechanical, physical and thermal properties and good topographical morphology and were highly biocompatible. The nanofibers were scrutinized for their efficacy in stimulating differentiation to a neuronal phenotype. The elongation factor (E-factor) of the neural cells had doubled in the bioactive incorporated composite compared to other scaffolds, as observed on phalloidin staining of their cytoskeleton, which endorsed enhanced neural differentiation on the fabricated nanofiber scaffold. There was a significant increase in the expression of neural-lineage specific markers on investigation of mRNA by real time PCR, showing a 10 fold increase in the gene expression of β-III-tubulin, a 5.5 fold increase for microtubule associated protein 2 gene and 3.5 fold for neurofilament M gene in the cells cultured over bioactive incorporated aligned nanofiber composites. Similarly protein expression was analyzed by immunofluorescence and flow cytometry studies, which showed an increase in the expression of β-III-tubulin in the composite nanofiber. This corroborates that neuronal differentiation is enhanced by the aligned nanotopography and spatio-temporal delivery of triiodothyronine and retinoic acid, opening avenues for nerve regenerative graft fabrication.

Nanotopography featured polycaprolactone/polyethyleneoxide microfibers modulate endothelial cell response

Among many physical properties, surface nanotopography has been found to strongly affect cell adhesion, migration and other functions. Accurate biological interpretation requires the nanotopography to be presented in a three-dimensional (3D) micro-environment. Herein, immiscible blends of polycaprolactone (PCL)/polyethyleneoxide (PEO) were electrospun into a grounded coagulation bath, resulting in macroporous microfibers with nanotopography featured surfaces. Variations in PCL/PEO ratios enabled tunable surface nanotopographic structures, from longitudinal submicron grooves to transverse nano-lamellae. Chemical composition, crystallinity and quantitative nanomechanical analysis confirmed that the interplay of the two semi-crystalline immiscible polymers and the pairing of miscible solvents/non-solvents in both the electrospinning solution and the bath solution were critical for the formation of the secondary structure. It was found that the nanotopography features promoted the proliferation of human umbilical vein endothelial cells (HUVECs) compared with their smooth film counterparts. An analysis of the cell adhesion related markers, vinculin and phosphorylated focal adhesion kinase (pFAK), further revealed that the nanotopographies enhanced the nascent adhesion complex formation compared with smooth PCL fibers, even in the scaffolds with a high PEO content, which is often considered as a non-adhesive material.

Surface nanotopography guides kidney-derived stem cell differentiation into podocytes

Stem cells have enormous potential for developing novel therapies for kidney disease but our current inability to direct their differentiation to specialised renal cells presents a barrier to their use in renal bioengineering and drug development programmes. Here, a plasma-based technology was used to produce a range of biocompatible substrates comprising controlled surface nanotopography and tailored outermost chemical functionalities. These novel substrata were used to investigate the response of mouse kidney-derived stem cells to changes in both substrate nanotopography and surface chemistry. The stem cells proliferated to a similar extent on all substrates, but specific combinations of nanotopography and surface chemistry promoted differentiation into either podocyte or proximal tubule-like cells. The data reveal that high density of surface nanodefects in association with amine rich chemistry primarily lead to differentiation into podocytes while surfaces with low amine content constituted better substrates for differentiation into proximal tubule cells regardless of the surface nanotopographic profile. Thus plasma coated nanorough substrate may provide useful platform for guiding the fate kidney stem cell in vitro.

STATEMENT OF SIGNIFICANCE

Adult kidney-derived stem cells have been identified as a promising way to regenerate damaged nephrons. Artificial growth platforms capable to guide the stem cells differentiation into useful cell lineages are needed to expand regenerative cell therapies for chronic kidney diseases. Chemically homogeneous growth substrates endowed with nanotopography gradients were generated via plasma assisted methods in order to investigate the effect of physical cues on the proliferation and differentiation of kidney-derived stem cells. For the first time it is shown that the surface density of the nano-structures had a greater impact on fate of the stem cells than their size. Careful design of the growth substrate nanotopography may help directing the differentiation into either podocytes or proximal tubule cells.

Electrospun 3D Fibrous Scaffolds for Chronic Wound Repair

Chronic wounds are difficult to heal spontaneously largely due to the corrupted extracellular matrix (ECM) where cell ingrowth is obstructed. Thus, the objective of this study was to develop a three-dimensional (3D) biodegradable scaffold mimicking native ECM to replace the missing or dysfunctional ECM, which may be an essential strategy for wound healing. The 3D fibrous scaffolds of poly(lactic acid-co-glycolic acid) (PLGA) were successfully fabricated by liquid-collecting electrospinning, with 5~20 µm interconnected pores. Surface modification with the native ECM component aims at providing biological recognition for cell growth. Human dermal fibroblasts (HDFs) successfully infiltrated into scaffolds at a depth of ~1400 µm after seven days of culturing, and showed significant progressive proliferation on scaffolds immobilized with collagen type I. In vivo models showed that chronic wounds treated with scaffolds had a faster healing rate. These results indicate that the 3D fibrous scaffolds may be a potential wound dressing for chronic wound repair.