Micropatterned hydrogenated amorphous carbon guides mesenchymal stem cells towards neuronal differentiation

Potential of Nano-Engineered Stem Cells in the Treatment of Multiple Sclerosis: A Comprehensive Review

Multiple sclerosis (MS) is a chronic and degrading autoimmune disorder mainly targeting the central nervous system, leading to progressive neurodegeneration, demyelination, and axonal damage. Current treatment options for MS are limited in efficacy, generally linked to adverse side effects, and do not offer a cure. Stem cell therapies have emerged as a promising therapeutic strategy for MS, potentially promoting remyelination, exerting immunomodulatory effects and protecting against neurodegeneration. Therefore, this review article focussed on the potential of nano-engineering in stem cells as a therapeutic approach for MS, focusing on the synergistic effects of combining stem cell biology with nanotechnology to stimulate the proliferation of oligodendrocytes (OLs) from neural stem cells and OL precursor cells, by manipulating neural signalling pathways-PDGF, BMP, Wnt, Notch and their essential genes such as Sox, bHLH, Nkx. Here we discuss the pathophysiology of MS, the use of various types of stem cells in MS treatment and their mechanisms of action. In the context of nanotechnology, we present an overview of its applications in the medical and research field and discuss different methods and materials used to nano-engineer stem cells, including surface modification, biomaterials and scaffolds, and nanoparticle-based delivery systems. We further elaborate on nano-engineered stem cell techniques, such as nano script, nano-exosome hybrid, nano-topography and their potentials in MS. The article also highlights enhanced homing, engraftment, and survival of nano-engineered stem cells, targeted and controlled release of therapeutic agents, and immunomodulatory and tissue repair effects with their challenges and limitations. This visual illustration depicts the process of utilizing nano-engineering in stem cells and exosomes for the purpose of delivering more accurate and improved treatments for Multiple Sclerosis (MS). This approach targets specifically the creation of oligodendrocytes, the breakdown of which is the primary pathological factor in MS.

Thermal treatment of magnesium particles in polylactic acid polymer films elicits the expression of osteogenic differentiation markers and lipidome profile remodeling in human adipose stem cells

The efficacy of polylactic acid (PLA)/Magnesium (Mg)-based materials for driving stem cells toward bone tissue engineering applications requires specific Mg surface properties to modulate the interface of stem cells with the film. Here, we have developed novel PLA/Mg-based composites and explored their osteogenic differentiation potential on human adipose stem cells (hASCs). Mg-particles/polymer interface was improved by two treatments: heating in oxidative atmosphere (TT) and surface modification with a compatibilizer (PEI). Different contents of Mg particles were dispersed in PLA and composite surface and bulk properties, protein adsorption, stem cell-PLA/Mg interactions, osteogenic markers expressions, and lipids composition profile were evaluated. Mg particles were uniformly distributed on the surface and in the bulk PLA polymer. Improved and modulated particle-polymer adhesion was observed in Mg particle-treated composites. After 21 days in canonical growth culture conditions, hASCs on PLA/MgTT displayed the highest expression of the general osteogenic markers, RUNX2, SSP1, and BGLAP genes, Alkaline Phosphatase, type I Collagen, Osteopontin, and Calcium deposits. Moreover, by LC/MS QTOF mass-spectrophotometry lipidomic analysis, we found in PLA/MgTT-cells, for the first time, a remodeling of the lipid classes composition associated with the osteogenic differentiation. We ascribed these results to MgTT characteristics, which improve Mg availability and composite osteoinductive performance.

Biomimicked large-area anisotropic grooves fromDracaena sanderianaleaf enhances cellular alignment and subsequent differentiation

Cellular alignment is important for the proper functioning of different tissues such as muscles or blood vessel walls. Hence, in tissue engineering, sufficient effort has been made to control cellular orientation and alignment. It has been shown that micro-and nanoscale anisotropic topological features on cell culture substrates can control cellular orientation. Such substrates are fabricated using various lithography techniques such as photolithography and soft lithography. Although such techniques are suitable for creating patterns in small areas to establish a proof-of-concept, patterning large areas with intricate features is an unsolved problem. In this work, we report that a replica of the groove-like anisotropic patterns of the abaxial side of aDracaena sanderiana(bamboo) leaf can be used for large-area patterning of cells. We imprinted the leaf on polydimethylsiloxane (PDMS) and characterised its surface topography using scanning electron microscopy. We further cultured bone marrow human mesenchymal cells (BM-hMSCs), skeletal muscle cells (C2C12), and neuroblastoma cells (SHSY5Y) on the patterned PDMS on which the cells orient along the direction of the grooved pattern. Further, we observed enhanced neuronal differentiation of SHSY5Y cells on biomimicked pattern compared to flat PDMS as measured by percentage of cells with neurites, neurite length and the expression of neuronal differentiation marker beta-III tubulin (TUJ1). This process is simple, frugal, and can be adopted by laboratories with resource constraints. This one-step technique to fabricate large-area anisotropic surface patterns from bamboo leaves can be used as a platform to study cellular alignment and its effect on various cellular functions, including differentiation.

Surface Functionalized Polyaniline Nanofibers:Chitosan Nanocomposite for Promoting Neuronal-like Differentiation of Primary Adipose Derived Mesenchymal Stem Cells and Urease Activity

Bioscaffolds having electrically conducting polymers (CPs) have become increasingly relevant in tissue engineering (TE) because of their ability to regulate conductivity and promote biological function. With this in mind, the current study shows a conducting polyaniline nanofibers (PNFs) dispersed chitosan (Ch) nanocomposites scaffold with a simple one-step surface functionalization approach using glutaraldehyde for potential neural regeneration applications. According to the findings, 4 wt % PNFs dispersion in Ch matrix is an optimal concentration for achieving desirable biological functions while maintaining required physicochemical properties as evidenced by SEM, XRD, current-voltage (I-V) measurement, mechanical strength test, and in vitro biodegradability test. Surface chemical compositional analysis using XPS and ATR FT-IR confirms the incorporation of aldehyde functionality after functionalization, which is corroborated by surface energy calculations following the Van Oss-Chaudhury-Good method. Surface functionalization induced enhancement in surface hydrophilicity in terms of the polar component of surface energy (γ_i^AB) from 6.35 to 12.54 mN m^-1 along with an increase in surface polarity from 13.61 to 22.54%. Functionalized PNF:Ch scaffolds demonstrated improvement in enzyme activity from 67 to 94% and better enzyme kinetics with a reduction of Michaelis constants (K_m) from 21.55 to 13.81 mM, indicating favorable protein-biomaterial interactions and establishing them as biologically perceptible materials. Surface functionalization mediated improved cell-biomaterial interactions led to improved viability, adhesion, and spreading of primary adipose derived mesenchymal stem cells (ADMSCs) as well as improved immunocompatibility. Cytoskeletal architecture assessment under differentiating media containing 10 ng/mL of each basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) revealed significant actin remodeling with neurite-like projections on the functionalized scaffolds after 14 days. Immunocytochemistry results showed that more than 85% of cells expressed early neuron specific β III tubulin protein on the functionalized scaffolds, whereas glial fibrillary acidic protein (GFAP) expression was limited to approximately 40% of cells. The findings point to the functionalized nanocomposites' potential as a smart scaffold for electrically stimulated neural regeneration, as they are flexible enough to be designed into microchanneled or conduit-like structures that mimic the microstructures and mechanical properties of peripheral nerves.

Constructing a cell microenvironment with biomaterial scaffolds for stem cell therapy

Stem cell therapy is widely recognized as a promising strategy for exerting therapeutic effects after injury in degenerative diseases. However, limitations such as low cell retention and survival rates after transplantation exist in clinical applications. In recent years, emerging biomaterials that provide a supportable cellular microenvironment for transplanted cells have optimized the therapeutic efficacy of stem cells in injured tissues or organs. Advances in the engineered microenvironment are revolutionizing our understanding of stem cell-based therapies by co-transplanting with synthetic and tissue-derived biomaterials, which offer a scaffold for stem cells and propose an unprecedented opportunity to further employ significant influences in tissue repair and regeneration.

Functionalized Silica Star-Shaped Nanoparticles and Human Mesenchymal Stem Cells: An In Vitro Model

The biomedical translational applications of functionalized nanoparticles require comprehensive studies on their effect on human stem cells. Here, we have tested neat star-shaped mesoporous silica nanoparticles (s-MSN) and their chemically functionalized derivates; we examined nanoparticles (NPs) with similar dimensions but different surface chemistry, due to the amino groups grafted on silica nanoparticles (s-MSN-NH2), and gold nanoseeds chemically adsorbed on silica nanoparticles (s-MSN-Au). The different samples were dropped on glass coverslips to obtain a homogeneous deposition differing only for NPs' chemical functionalization and suitable for long-term culture of human Bone Marrow-Mesenchymal stem cells (hBM-MSCs) and Adipose stem cells (hASCs). Our model allowed us to demonstrate that hBM-MSCs and hASCs have comparable growth curves, viability, and canonical Vinculin Focal adhesion spots on functionalized s-MSN-NH2 and s-MSN-Au as on neat s-MSN and control systems, but also to show morphological changes on all NP types compared to the control counterparts. The new shape was stem-cell-specific and was maintained on all types of NPs. Compared to the other NPs, s-MSN-Au exerted a small genotoxic effect on both stem cell types, which, however, did not affect the stem cell behavior, likely due to a peculiar stem cell metabolic restoration response.

Unpatterned Bioactive Poly(Butylene 1,4-Cyclohexanedicarboxylate)-Based Film Fast Induced Neuronal-Like Differentiation of Human Bone Marrow-Mesenchymal Stem Cells

Herein, we present poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) films characterized by an unpatterned microstructure and a specific hydrophobicity, capable of boosting a drastic cytoskeleton architecture remodeling, culminating with the neuronal-like differentiation of human bone marrow-mesenchymal stem cells (hBM-MSCs). We have used two different filming procedures to prepare the films, solvent casting (PBCE) and compression-moulding (PBCE*). PBCE film had a rough and porous surface with spherulite-like aggregations (Ø = 10-20 μm) and was characterized by a water contact angle = 100°. PBCE* showed a smooth and continuous surface without voids and visible spherulite-like aggregations and was more hydrophobic (WCA = 110°). Both surface characteristics were modulated through the copolymerization of different amounts of ether-oxygen-containing co-units into PBCE chemical structure. We showed that only the surface characteristics of PBCE-solvent-casted films steered hBM-MSCs toward a neuronal-like differentiation. hBM-MSCs lost their canonical mesenchymal morphology, acquired a neuronal polarized shape with a long cell protrusion (≥150 μm), expressed neuron-specific class III β-tubulin and microtubule-associated protein 2 neuronal markers, while nestin, a marker of uncommitted stem cells, was drastically silenced. These events were observed as early as 2-days after cell seeding. Of note, the phenomenon was totally absent on PBCE* film, as hBM-MSCs maintained the mesenchymal shape and behavior and did not express neuronal/glial markers.

Novel Nanocomposite PLA Films with Lignin/Zinc Oxide Hybrids: Design, Characterization, Interaction with Mesenchymal Stem Cells

Herein we present the production of novel nanocomposite films consisting of polylactic acid (PLA) polymer and the inclusion of nanoparticles of lignin (LNP), ZnO and hybrid ZnO@LNP (ZnO, 3.5% wt, ICP), characterized by similar regular shapes and different diameter distribution (30-70 nm and 100-150 nm, respectively). The obtained set of binary, ternary and quaternary systems were similar in surface wettability and morphology but different in the tensile performance: while the presence of LNP and ZnO in PLA caused a reduction of elastic modulus, stress and deformation at break, the inclusion of ZnO@LNP increased the stiffness and tensile strength (σb = 65.9 MPa and EYoung = 3030 MPa) with respect to neat PLA (σb = 37.4 MPa and EYoung = 2280 MPa). Neat and nanocomposite PLA-derived films were suitable for adult human bone marrow-mesenchymal stem cells and adipose stem cell cultures, as showed by their viability and behavior comparable to control conditions. Both stem cell types adhered to the films' surface by vinculin focal adhesion spots and responded to the films' mechanical properties by orchestrating the F-actin-filamin A interaction. Collectively, our results support the biomedical application of neat- and nanocomposite-PLA films and, based on the absence of toxicity in seeded stem cells, provide a proof of principle of their safety for food packaging purposes.

Therapeutic Advancement in Neuronal Transdifferentiation of Mesenchymal Stromal Cells for Neurological Disorders

Neurodegenerative disorders have become the leading cause of chronic pain and death. Treatments available are not sufficient to help the patients as they only alleviate the symptoms and not the cause. In this regard, stem cells therapy has emerged as an upcoming option for the replacement of dead and damaged neurons. Stem cells, in general, are characterized as cells exhibiting potency properties, i.e., on being subjected to specific conditions they transform into cells of another lineage. Of all the types, mesenchymal stem cells (MSCs) are known for their pluripotent nature without the obstacle of ethical concern surrounding the procurement of other cell types. Although fibroblasts are quite similar to MSCs morphologically, certain markers like CD73, CD 90 are specific to MSCs, making both the cell types distinguishable from each other. This is implemented while procuring MSCs from a plethora of sources like umbilical cord blood, adipose tissue, bone marrow, etc. Among these, bone marrow MSCs are the most widely used type for neural regeneration. Neural regeneration is achieved via transdifferentiation. Several studies have either transplanted the stem cells into rodent models or have carried out transdifferentiation in vitro. The process involves a combination of growth factors, pre-treatment factors, and neuronal differentiation inducing mediums. The results obtained are characterized by neuron-like morphology, expression of markers, along with electrophysical activity in some. Recent attempts involve exploring biomaterials that may mimic the native ECM and therefore can be directly introduced at the site of interest. The review gives a brief description of MSCs, their sources and markers, and the different attempts that have been made towards achieving the goal of differentiating MSCs into neurons.

Capturing instructive cues of tissue microenvironment by silica bioreplication

Cells in tissues are enveloped by an instructive niche made of the extracellular matrix. These instructive niches contain three general types of information: topographical, biochemical and mechanical. While the combined effects of these three factors are widely studied, the functions of each individual one has not been systematically characterised, because it is impossible to alter a single factor in a tissue microenvironment without simultaneously affecting the other two. Silica BioReplication (SBR) is a process that converts biological samples into silica, faithfully preserving the original topography at the nano-scale. We explored the use of this technique to generate inorganic replicas of intact mammalian tissues, including tendon, cartilage, skeletal muscle and spinal cord. Scanning electron and atomic force microscopy showed that the resulting replicas accurately preserved the three-dimensional ultrastructure of each tissue, while all biochemical components were eradicated by calcination. Such properties allowed the uncoupling the topographical information of a tissue microenvironment from its biochemical and mechanical components. Here, we showed that human mesenchymal stem cells (MSC) cultured on the replicas of different tissues displayed vastly different morphology and focal adhesions, suggesting that the topography of the tissue microenvironment captured by SBR could profoundly affect MSC biology. MSC cultured on tendon replica elongated and expressed tenocytes marker, while MSC on the spinal cord replica developed into spheroids that resembled neurospheres, in morphology and in the expression of neurosphere markers, and could be further differentiated into neuron-like cells. This study reveals the significance of topographical cues in a cell niche, as tissue-specific topography was sufficient in initiating and directing differentiation of MSC, despite the absence of any biochemical signals. SBR is a convenient and versatile method for capturing this topographical information, facilitating the functional characterisation of cell niches. STATEMENT OF SIGNIFICANCE: Various studies have shown that three major factors, topographical, biochemical and mechanical, in a tissue microenvironment (TME) are essential for cellular homeostasis and functions. Current experimental models are too simplistic to represent the complexity of the TME, hindering the detailed understanding of its functions. In particular, the importance each factor in a tissue microenvironment have not been individually characterised, because it is challenging to alter one of these factors without simultaneously affecting the other two. Silica bioreplication (SBR) is a process that converts biological samples into silica replicas with high structural fidelity. SBR is a convenient and versatile method for capturing this topographical information on to a biologically inert material, allowing the functional characterisation of the architecture of a TME.

Biomaterials and Advanced Biofabrication Techniques in hiPSCs Based Neuromyopathic Disease Modeling

Induced pluripotent stem cells (iPSCs) are reprogrammed somatic cells by defined factors, and have great application potentials in tissue regeneration and disease modeling. Biomaterials have been widely used in stem cell-based studies, and are involved in human iPSCs based studies, but they were not enough emphasized and recognized. Biomaterials can mimic the extracellular matrix and microenvironment, and act as powerful tools to promote iPSCs proliferation, differentiation, maturation, and migration. Many classic and advanced biofabrication technologies, such as cell-sheet approach, electrospinning, and 3D-bioprinting, are used to provide physical cues in macro-/micro-patterning, and in combination with other biological factors to support iPSCs applications. In this review, we highlight the biomaterials and fabrication technologies used in human iPSC-based tissue engineering to model neuromyopathic diseases, particularly those with genetic mutations, such as Duchenne Muscular Dystrophy (DMD), Congenital Heart Diseases (CHD) and Alzheimer's disease (AD).

Silk fibroin induces chondrogenic differentiation of canine adipose-derived multipotent mesenchymal stromal cells/mesenchymal stem cells

Under appropriate culture conditions, mesenchymal stem cells (MSC), also called more properly multipotent mesenchymal stromal cells (MMSC), can be induced toward differentiation into different cell lineages. In order to guide stem cell fate within an environment resembling the stem cell niche, different biomaterials are being developed. In the present study, we used silk fibroin (SF) as a biomaterial supporting the growth of MMSC and studied its effect on chondrogenesis of canine adipose–derived MMSC (cADMMSC). Adipose tissue was collected from nine privately owned dogs. MMSC were cultured on SF films and SF scaffolds in a standard cell culture medium. Cell morphology was evaluated by scanning electron microscopy (SEM). Chondrogenic differentiation was evaluated by alcian blue staining and mRNA expression of collagen type 1, collagen type 2, Sox9, and Aggrecan genes. cADMMSC cultured on SF films and SF scaffolds stained positive using alcian blue. SEM images revealed nodule-like structures with matrix vesicles and fibers resembling chondrogenic nodules. Gene expression of chondrogenic markers Sox9 and Aggrecan were statistically significantly upregulated in cADMMSC cultured on SF films in comparison to negative control cADMMSC. This result suggests that chondrogenesis of cADMMSC could occur when cells were grown on SF films in a standard cell culture medium without specific culture conditions, which were previously considered necessary for induction of chondrogenic differentiation.

Adipose Stem Cell Translational Applications: From Bench-to-Bedside

During the last five years, there has been a significantly increasing interest in adult adipose stem cells (ASCs) as a suitable tool for translational medicine applications. The abundant and renewable source of ASCs and the relatively simple procedure for cell isolation are only some of the reasons for this success. Here, we document the advances in the biology and in the innovative biotechnological applications of ASCs. We discuss how the multipotential property boosts ASCs toward mesenchymal and non-mesenchymal differentiation cell lineages and how their character is maintained even if they are combined with gene delivery systems and/or biomaterials, both in vitro and in vivo.

Recent Advances in Nanocomposites Based on Aliphatic Polyesters: Design, Synthesis, and Applications in Regenerative Medicine

In the last decade, biopolymer matrices reinforced with nanofillers have attracted great research efforts thanks to the synergistic characteristics derived from the combination of these two components. In this framework, this review focuses on the fundamental principles and recent progress in the field of aliphatic polyester-based nanocomposites for regenerative medicine applications. Traditional and emerging polymer nanocomposites are described in terms of polymer matrix properties and synthesis methods, used nanofillers, and nanocomposite processing and properties. Special attention has been paid to the most recent nanocomposite systems developed by combining alternative copolymerization strategies with specific nanoparticles. Thermal, electrical, biodegradation, and surface properties have been illustrated and correlated with the nanoparticle kind, content, and shape. Finally, cell-polymer (nanocomposite) interactions have been described by reviewing analysis methodologies such as primary and stem cell viability, adhesion, morphology, and differentiation processes.

Nanocomposites Based on Biodegradable Polymers

In the present review paper, our main results on nanocomposites based on biodegradable polymers (on a time scale from 2010 to 2018) are reported. We mainly focused our attention on commercial biodegradable polymers, which we mixed with different nanofillers and/or additives with the final aim of developing new materials with tunable specific properties. A wide list of nanofillers have been considered according to their shape, properties, and functionalization routes, and the results have been discussed looking at their roles on the basis of different adopted processing routes (solvent-based or melt-mixing processes). Two main application fields of nanocomposite based on biodegradable polymers have been considered: the specific interaction with stem cells in the regenerative medicine applications or as antimicrobial materials and the active role of selected nanofillers in food packaging applications have been critically revised, with the main aim of providing an overview of the authors' contribution to the state of the art in the field of biodegradable polymeric nanocomposites.

The Role of Biomaterials in Implantation for Central Nervous System Injury

Permanent deficits that occur in memory, sensation, and cognition can result from central nervous system (CNS) trauma that causes dysfunction and/or unregulated CNS regeneration. Some therapeutic approaches are preferentially applied to the human body. Therefore, cell transplantation, one of the therapeutic strategies, may be used to benefit people. However, poor cell viability and low efficacy are the limitations to cell transplantation strategies. Biomaterials have been widely used in several fields (e.g., triggering cell differentiation, guiding cell migration, improving wound healing, and increasing tissue regeneration) by modulating their characteristics in chemistry, topography, and softness/stiffness for highly flexible application. We reviewed implanted biomaterials to investigate the roles and influences of physical/chemical properties on cell behaviors and applications. With their unique molecular features, biomaterials are delivered in several methods and mixed with transplanted cells, which assists in increasing postimplanted biological substance efficiency on cell survival, host responses, and functional recovery of animal models. Moreover, tracking the routes of these transplanted cells using biomaterials as labeling agents is crucial for addressing their location, distribution, activity, and viability. Here, we provide comprehensive comments and up-to-date research of the application of biomaterials.

Surface Hydrophilicity of Poly(l-Lactide) Acid Polymer Film Changes the Human Adult Adipose Stem Cell Architecture

Current knowledge indicates that the molecular cross-talk between stem cells and biomaterials guides the stem cells’ fate within a tissue engineering system. In this work, we have explored the effects of the interaction between the poly(l-lactide) acid (PLLA) polymer film and human adult adipose stem cells (hASCs), focusing on the events correlating the materials’ surface characteristics and the cells’ plasma membrane. hASCs were seeded on films of pristine PLLA polymer and on a PLLA surface modified by the radiofrequency plasma method under oxygen flow (PLLA+O₂). Comparative experiments were performed using human bone-marrow mesenchymal stem cells (hBM-MSCs) and human umbilical matrix stem cells (hUCMSCs). After treatment with oxygen-plasma, the surface of PLLA films became hydrophilic, whereas the bulk properties were not affected. hASCs cultured on pristine PLLA polymer films acquired a spheroid conformation. On the contrary, hASCs seeded on PLLA+O₂ film surface maintained the fibroblast-like morphology typically observed on tissue culture polystyrene. This suggests that the surface hydrophilicity is involved in the acquisition of the spheroid conformation. Noteworthy, the oxygen treatment had no effects on hBM-MSC and hUCMSC cultures and both stem cells maintained the same shape observed on PLLA films. This different behavior suggests that the biomaterial-interaction is stem cell specific.

Toward the development of biomimetic injectable and macroporous biohydrogels for regenerative medicine

Repairing or replacing damaged human tissues has been the ambitious goal of regenerative medicine for over 25years. One promising approach is the use of hydrated three-dimensional scaffolds, known as hydrogels, which have had good results repairing tissues in pre-clinical trials. Benefiting from breakthrough advances in the field of biology, and more particularly regarding cell/matrix interactions, these hydrogels are now designed to recapitulate some of the fundamental cues of native environments to drive the local tissue regeneration. We highlight the key parameters that are required for the development of smart and biomimetic hydrogels. We also review the wide variety of polymers, crosslinking methods, and manufacturing processes that have been developed over the years. Of particular interest is the emergence of supramolecular chemistries, allowing for the development of highly functional and reversible biohydrogels. Moreover, advances in computer assisted design and three-dimensional printing have revolutionized the production of macroporous hydrogels and allowed for more complex designs than ever before with the opportunity to develop fully reconstituted organs. Today, the field of biohydrogels for regenerative medicine is a prolific area of research with applications for most bodily tissues. On top of these applications, injectable hydrogels and macroporous hydrogels (foams) were found to be the most successful. While commonly associated with cells or biologics as drug delivery systems to increase therapeutic outcomes, they are steadily being used in the emerging fields of organs-on-chip and hydrogel-assisted cell therapy. To highlight these advances, we review some of the recent developments that have been achieved for the regeneration of tissues, focusing on the articular cartilage, bone, cardiac, and neural tissues. These biohydrogels are associated with improved cartilage and bone defects regeneration, reduced left ventricular dilation upon myocardial infarction and display promising results repairing neural lesions. Combining the benefits from each of these areas reviewed above, we envision that an injectable biohydrogel foam loaded with either stem cells or their secretome is the most promising hydrogel solution to trigger tissue regeneration. A paradigm shift is occurring where the combined efforts of fundamental and applied sciences head toward the development of hydrogels restoring tissue functions, serving as drug screening platforms or recreating complex organs.

Direct reprogramming and biomaterials for controlling cell fate

Direct reprogramming which changes the fate of matured cell is a very useful technique with a great interest recently. This approach can eliminate the drawbacks of direct usage of stem cells and allow the patient specific treatment in regenerative medicine. Overexpression of diverse factors such as general reprogramming factors or lineage specific transcription factors can change the fate of already differentiated cells. On the other hand, biomaterials can provide physical and topographical cues or biochemical cues on cells, which can dictate or significantly affect the differentiation of stem cells. The role of biomaterials on direct reprogramming has not been elucidated much, but will be potentially significant to improve the efficiency or specificity of direct reprogramming. In this review, the strategies for general direct reprogramming and biomaterials-guided stem cell differentiation are summarized with the addition of the up-to-date progress on biomaterials for direct reprogramming.

Ex-Vivo Tissues Engineering Modeling for Reconstructive Surgery Using Human Adult Adipose Stem Cells and Polymeric Nanostructured Matrix

The major challenge for stem cell translation regenerative medicine is the regeneration of damaged tissues by creating biological substitutes capable of recapitulating the missing function in the recipient host. Therefore, the current paradigm of tissue engineering strategies is the combination of a selected stem cell type, based on their capability to differentiate toward committed cell lineages, and a biomaterial, that, due to own characteristics (e.g., chemical, electric, mechanical property, nano-topography, and nanostructured molecular components), could serve as active scaffold to generate a bio-hybrid tissue/organ. Thus, effort has been made on the generation of in vitro tissue engineering modeling. Here, we present an in vitro model where human adipose stem cells isolated from lipoaspirate adipose tissue and breast adipose tissue, cultured on polymeric INTEGRA^® Meshed Bilayer Wound Matrix (selected based on conventional clinical applications) are evaluated for their potential application for reconstructive surgery toward bone and adipose tissue. We demonstrated that human adipose stem cells isolated from lipoaspirate and breast tissue have similar stemness properties and are suitable for tissue engineering applications. Finally, the overall results highlighted lipoaspirate adipose tissue as a good source for the generation of adult adipose stem cells.

Material and mechanical factors: new strategy in cellular neurogenesis

Since damaged neural circuits are not generally self-recovered, developing methods to stimulate neurogenesis is critically required. Most studies have examined the effects of soluble pharmacological factors on the cellular neurogenesis. On the other hand, it is now recognized that the other extracellular factors, including material and mechanical cues, also have a strong potential to induce cellular neurogenesis. This article will review recent data on the material (chemical patterning, micro/nano-topography, carbon nanotube, graphene) and mechanical (static cue from substrate stiffness, dynamic cue from stretch and flow shear) stimulations of cellular neurogenesis. These approaches may provide new neural regenerative medicine protocols. Scaffolding material templates capable of triggering cellular neurogenesis can be explored in the presence of neurogenesis-stimulatory mechanical environments, and also with conventional soluble factors, to enhance axonal growth and neural network formation in neural tissue engineering.

Keratins extracted from Merino wool and Brown Alpaca fibres: thermal, mechanical and biological properties of PLLA based biocomposites

Keratins extracted from Merino wool (KM) and Brown Alpaca fibres (KA) by sulphitolysis and commercial hydrolyzed keratins (KH) were used as fillers in poly(l-lactic) acid based biocomposites processed by solvent casting in chloroform. Different contents (1 wt.% and 5 wt.%) of keratins were considered and the morphological, thermal, mechanical, chemical and biological behaviours of the developed PLLA biocomposites were investigated. The results confirmed that surface morphologies of biocomposites revealed specific round-like surface topography function of different microsized keratin particles in different weight contents, such as the analysis of bulk morphologies which confirmed a phase adhesion strictly dependent by the keratin source. Transparency and thermal responses were deeply affected by the presence of the different keratins and their interaction with the PLLA matrix. Tensile test results underlined the possibility to modulate the mechanical behaviour of PLLA selecting the keratin type and content in order to influence positively the elastic and/or plastic response. It was demonstrated that surface characteristics of PLLA/KA systems also influenced the bovine serum albumin adsorption, moreover PLLA and PLLA biocomposites based on different kinds of keratins supported the culture of human bone-marrow mesenchymal stem cells, indicating that these biocomposites could be useful materials for medical applications.

The interaction of bacteria with engineered nanostructured polymeric materials: a review

Bacterial infections are a leading cause of morbidity and mortality worldwide. In spite of great advances in biomaterials research and development, a significant proportion of medical devices undergo bacterial colonization and become the target of an implant-related infection. We present a review of the two major classes of antibacterial nanostructured materials: polymeric nanocomposites and surface-engineered materials. The paper describes antibacterial effects due to the induced material properties, along with the principles of bacterial adhesion and the biofilm formation process. Methods for antimicrobial modifications of polymers using a nanocomposite approach as well as surface modification procedures are surveyed and discussed, followed by a concise examination of techniques used in estimating bacteria/material interactions. Finally, we present an outline of future sceneries and perspectives on antibacterial applications of nanostructured materials to resist or counteract implant infections.

Neurogenesis of neural crest-derived periodontal ligament stem cells by EGF and bFGF

Neuroregenerative medicine is an ever-growing field in which regeneration of lost cells/tissues due to a neurodegenerative disease is the ultimate goal. With the scarcity of available replacement alternatives, stem cells provide an attractive source for regenerating neural tissue. While many stem cell sources exist, including: mesenchymal stem cells, embryonic stem cells, and induced pluripotent stem cells, the limited cellular potency, technical difficulties, and ethical considerations associated with these make finding alternate sources a desirable goal. Periodontal ligament stem cells (PDLSCs) derived from the neural crest were induced into neural-like cells using a combination of epidermal growth factor, and basic fibroblast growth factor. Morphological changes were evident in our treated group, seen under both light microscopy and scanning electron microscopy. A statistically significant increase in the expression of neuron-specific β-tubulin III and the neural stem/progenitor cell marker nestin, along with positive immunohistochemical staining for glial fibrillary acidic protein, demonstrated the success of our treatment in inducing both neuronal and glial phenotypes. Positive staining for synaptophysin demonstrated neural connections and electrophysiological recordings indicated that when subjected to whole-cell patch clamping, our treated cells displayed inward currents conducted through voltage-gated sodium (Na(+) ) channels. Taken together, our results indicate the success of our treatment in inducing PDLSCs to neural-like cells. The ease of sourcing and expansion, their embryologic neural crest origin, and the lack of ethical implications in their use make PDLSCs an attractive source for use in neuroregenerative medicine.

Mechanoregulation of stem cell fate via micro-/nano-scale manipulation for regenerative medicine

Recent developments in the field of mechanobiology have renewed the call for a better understanding of the role of mechanical forces as potent regulators and indicators of stem cell fate. Although it is well established that mechanical forces play a crucial role in guiding tissue development, little is known about how submicroscopic biomechanical forces can influence key stem cell behaviors. This review will detail the use of micro-/nano-technologies that are advancing our current understanding of stem cell mechanobiology, and mechanoregulation of stem cell fate using engineered surface topographies and small-scale patterning techniques. The involvement of focal adhesions and the cytoskeleton systems as a common biophysical impetus through which these mechanical signals are transduced via distinct signaling pathways will also be discussed. These insights are envisioned to provide the basis for the rational design of future biocompatible materials and may inspire alternative drug-free therapeutic strategies to manage diseased sites via biomechanical management.

PVA bio-nanocomposites: a new take-off using cellulose nanocrystals and PLGA nanoparticles

The formation of a new generation of hybrid bio-nanocomposites is reported: these are intended at modulating the mechanical, thermal and biocompatibility properties of the poly(vinyl alcohol) (PVA) by the combination of cellulose nanocrystals (CNC) and poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) loaded with bovine serum albumin fluorescein isothiocynate conjugate (FITC-BSA). CNC were synthesized from microcrystalline cellulose by hydrolysis, while PLGA nanoparticles were produced by a double emulsion with subsequent solvent evaporation. Firstly, binary bio-nanocomposites with different CNC amounts were developed in order to select the right content of CNC. Next, ternary PVA/CNC/NPs bio-nanocomposites were developed. The addition of CNC increased the elongation properties without compromising the other mechanical responses. Thermal analysis underlined the nucleation effect of the synergic presence of cellulose and nanoparticles. Remarkably, bio-nanocomposite films are suitable to vehiculate biopolymeric nanoparticles to adult bone marrow mesenchymal stem cells successfully, thus representing a new tool for drug delivery strategies.

Differential regulation of stiffness, topography, and dimension of substrates in rat mesenchymal stem cells

The physiological microenvironment of the stem cell niche, including the three factors of stiffness, topography, and dimension, is crucial to stem cell proliferation and differentiation. Although a growing body of evidence is present to elucidate the importance of these factors individually, the interaction of the biophysical parameters of the factors remains insufficiently characterized, particularly for stem cells. To address this issue fully, we applied a micro-fabricated polyacrylamide hydrogel substrate with two elasticities, two topographies, and three dimensions to systematically test proliferation, morphology and spreading, differentiation, and cytoskeletal re-organization of rat bone marrow mesenchymal stem cells (rBMSCs) on twelve cases. An isolated but not combinatory impact of the factors was found regarding the specific functions. Substrate stiffness or dimension is predominant in regulating cell proliferation by fostering cell growth on stiff, unevenly dimensioned substrate. Topography is a key factor for manipulating cell morphology and spreading via the formation of a large spherical shape in a pillar substrate but not in a grooved substrate. Although stiffness leads to osteogenic or neuronal differentiation of rBMSCs on a stiff or soft substrate, respectively, topography or dimension also plays a lesser role in directing cell differentiation. Neither an isolated effect nor a combinatory effect was found for actin or tubulin expression, whereas a seemingly combinatory effect of topography and dimension was found in manipulating vimentin expression. These results further the understandings of stem cell proliferation, morphology, and differentiation in a physiologically mimicking microenvironment.

Nanocomposites Based on PLLA and Multi Walled Carbon Nanotubes Support the Myogenic Differentiation of Murine Myoblast Cell Line

We explored the effect of poly(L-lactic acid) (PLLA) containing various percentages (0.1, 0.5, 1, and 3 wt.%) of multi walled carbon nanotubes (MWCNTs) on the myogenic differentiation of C2C12 murine myoblast progenitor cells. We showed that all PLLA/MWCNTs nanocomposite materials support the myotubes formation more efficiently than neat PLLA as indicated by the high expression of the most significant myogenic markers: MyoD, Myosin Heavy Chain, dimension of myofibres, and fusion myogenic index. Interestingly, we note that both MyoD and myogenic fusion index levels were in the order 0.1 MWCNTs = 0.5 MWCNTs > 1 MWCNTs > 3 MWCNTs > neat PLLA, suggesting that the amount of MWCNTs influenced the cell differentiation.

Protein encapsulation in biodegradable polymeric nanoparticles: morphology, fluorescence behaviour and stem cell uptake

The synthesis and characterization of new biodegradable polymeric NPs loaded with bovine serum albumin marked with fluorescein isothiocyanate (FITC-BSA) is reported. The protein is encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) NPs by the double emulsion method with subsequent solvent evaporation. The NPs display a spherical shape with a narrow size distribution and no aggregation is observed after drying. Steady-state and time-resolved fluorescence measurements appear to be a sensitive method to investigate the protein environment on the nanometer-scale. Finally, FITC-BSA-loaded NPs are rapidly internalized in stem cells. Interestingly, 25% cells were slightly positive after 28 days.

Carbon nanotube-poly(lactide-co-glycolide) composite scaffolds for bone tissue engineering applications

Despite their indisputable clinical value, current tissue engineering strategies face major challenges in recapitulating the natural nano-structural and morphological features of native bone. The aim of this study is to take a step forward by developing a porous scaffold with appropriate mechanical strength and controllable surface roughness for bone repair. This was accomplished by homogenous dispersion of carbon nanotubes (CNTs) in a poly(lactide-co-glycolide) (PLGA) solution followed by a solvent casting/particulate leaching scaffold fabrication. Our results demonstrated that CNT/PLGA composite scaffolds possessed a significantly higher mechanical strength as compared to PLGA scaffolds. The incorporation of CNTs led to an enhanced surface roughness and resulted in an increase in the attachment and proliferation of MC3T3-E1 osteoblasts. Most interestingly, the in vitro osteogenesis studies demonstrated a significantly higher rate of differentiation on CNT/PLGA scaffolds compared to the control PLGA group. These results all together demonstrate the potential of CNT/PLGA scaffolds for bone tissue engineering as they possess the combined effects of mechanical strength and osteogenicity.

Porous membrane substrates offer better niches to enhance the Wnt signaling and promote human embryonic stem cell growth and differentiation

Human embryonic stem cells (hESCs) require specific niches for adhesion, expansion, and lineage-specific differentiation. In this study, we showed that a membrane substrate offers better tissue niches for hESC attachment, spreading, proliferation, and differentiation. The cell doubling time was shortened from 46.3±5.7 h for hESCs grown on solid substrates to 25.6±2.6 h for those on polyester (PE) membrane substrates with pore size of 0.4 μm. In addition, we observed an increase of approximately five- to ninefold of definitive endoderm marker gene expression in hESCs differentiated on PE or polyethylene terephthalate membrane substrates. Global gene expression analysis revealed upregulated expressions of a number of extracellular matrix and cell adhesion molecules in hESCs grown on membrane substrates. Further, an enhanced nuclear translocation of β-catenin was detected in these cells. These observations suggested the augmentation of Wnt signaling in hESCs grown on membrane substrates. These results also demonstrated that a membrane substrate can offer better physicochemical cues for enhancing in vitro hESC attachment, proliferation, and differentiation.

Tuning multi/pluri-potent stem cell fate by electrospun poly(L-lactic acid)-calcium-deficient hydroxyapatite nanocomposite mats

In this study, we investigated whether multipotent (human-bone-marrow-derived mesenchymal stem cells [hBM-MSCs]) and pluripotent stem cells (murine-induced pluripotent stem cells [iPSCs] and murine embryonic stem cells [ESCs]) respond to nanocomposite fibrous mats of poly(L-lactic acid) (PLLA) loaded with 1 or 8 wt % of calcium-deficient nanohydroxyapatite (d-HAp). Remarkably, the dispersion of different amounts of d-HAp to PLLA produced a set of materials (PLLA/d-HAp) with similar architectures and tunable mechanical properties. After 3 weeks of culture in the absence of soluble osteogenic factors, we observed the expression of osteogenic markers, including the deposition of bone matrix proteins, in multi/pluripotent cells only grown on PLLA/d-HAp nanocomposites, whereas the osteogenic differentiation was absent on stem-cell-neat PLLA cultures. Interestingly, this phenomenon was confined only in hBM-MSCs, murine iPSCs, and ESCs grown on direct contact with the PLLA/d-HAp mats. Altogether, these results indicate that the osteogenic differentiation effect of these electrospun PLLA/d-HAp nanocomposites was independent of the stem cell type and highlight the direct interaction of stem cell-polymeric nanocomposite and the mechanical properties acquired by the PLLA/d-HAp nanocomposites as key steps for the differentiation process.

Stem cell-biomaterial interactions for regenerative medicine

The synergism of stem cell biology and biomaterial technology promises to have a profound impact on stem-cell-based clinical applications for tissue regeneration. Biomaterials development is rapidly advancing to display properties that, in a precise and physiological fashion, could drive stem-cell fate both in vitro and in vivo. Thus, the design of novel materials is trying to recapitulate the molecular events involved in the production, clearance and interaction of molecules within tissue in pathologic conditions and regeneration of tissue/organs. In this review we will report on the challenges behind translating stem cell biology and biomaterial innovations into novel clinical therapeutic applications for tissue and organ replacements (graphical abstract).

Mechanotransduction: tuning stem cells fate

It is a general concern that the success of regenerative medicine-based applications is based on the ability to recapitulate the molecular events that allow stem cells to repair the damaged tissue/organ. To this end biomaterials are designed to display properties that, in a precise and physiological-like fashion, could drive stem cell fate both in vitro and in vivo. The rationale is that stem cells are highly sensitive to forces and that they may convert mechanical stimuli into a chemical response. In this review, we describe novelties on stem cells and biomaterials interactions with more focus on the implication of the mechanical stimulation named mechanotransduction.

Development of a New Tool for 3D Modeling for Regenerative Medicine

The effectiveness of therapeutic treatment based on regenerative medicine for degenerative diseases (i.e., neurodegenerative or cardiac diseases) requires tools allowing the visualization and analysis of the three-dimensional (3D) distribution of target drugs within the tissue. Here, we present a new computational procedure able to overcome the limitations of visual analysis emerging by the examination of a molecular signal within images of serial tissue/organ sections by using the conventional techniques. Together with the 3D anatomical reconstitution of the tissue/organ, our framework allows the detection of signals of different origins (e.g., marked generic molecules, colorimetric, or fluorimetric substrates for enzymes; microRNA; recombinant protein). Remarkably, the application does not require the employment of specific tracking reagents for the imaging analysis. We report two different representative applications: the first shows the reconstruction of a 3D model of mouse brain with the analysis of the distribution of theβ-Galactosidase, the second shows the reconstruction of a 3D mouse heart with the measurement of the cardiac volume.