Surface nanotopography guides kidney-derived stem cell differentiation into podocytes

Enhancing regenerative medicine: the crucial role of stem cell therapy

Stem cells offer new therapeutic avenues for the repair and replacement of damaged tissues and organs owing to their self-renewal and multipotent differentiation capabilities. In this paper, we conduct a systematic review of the characteristics of various types of stem cells and offer insights into their potential applications in both cellular and cell-free therapies. In addition, we provide a comprehensive summary of the technical routes of stem cell therapy and discuss in detail current challenges, including safety issues and differentiation control. Although some issues remain, stem cell therapy demonstrates excellent potential in the field of regenerative medicine and provides novel tactics and methodologies for managing a wider spectrum of illnesses and traumas.

Micro- and nanotechnology in biomedical engineering for cartilage tissue regeneration in osteoarthritis

Osteoarthritis, which typically arises from aging, traumatic injury, or obesity, is the most common form of arthritis, which usually leads to malfunction of the joints and requires medical interventions due to the poor self-healing capacity of articular cartilage. However, currently used medical treatment modalities have reported, at least in part, disappointing and frustrating results for patients with osteoarthritis. Recent progress in the design and fabrication of tissue-engineered microscale/nanoscale platforms, which arises from the convergence of stem cell research and nanotechnology methods, has shown promising results in the administration of new and efficient options for treating osteochondral lesions. This paper presents an overview of the recent advances in osteochondral tissue engineering resulting from the application of micro- and nanotechnology approaches in the structure of biomaterials, including biological and microscale/nanoscale topographical cues, microspheres, nanoparticles, nanofibers, and nanotubes.

Mechanistic Insight in Surface Nanotopography Driven Cellular Migration

Cellular migration plays a vital role in many physiological processes. To elucidate the role of surface nanotopography on the downstream signaling pathways underlying cell migration, model surfaces having well-defined hill-like surface nanotopography and uniform surface chemistry were designed and implemented using plasma polymerization and covalent attachment of nanoparticles of predetermined size. A scratch wound assay, immunostaining, and gene expression of focal adhesion (FA) proteins were performed to determine the influence of surface nanotopography on cell migration. The results of this study demonstrate that the gap closure between cell monolayers is faster on surfaces having greater nanoscale topography. The phenomenon is predominantly driven by cell migration and was independent from cell proliferation. Qualitative and quantitative assessment of proteins involved in the signaling pathways underlying cell migration showed significant modulation by surface nanotopography. Specifically, focal adhesion sites decreased with the increase in surface nanotopography scale while the expression of FA proteins increased. This implies that nanotopography mediated modulation of cell migration is directly governed by the recruitment of receptor and adapter proteins responsible for cell-surface interaction. The results of this study indicate that biomaterial devices and constructs having rationally designed surface nanotopography and chemistry could be utilized to regulate wound healing and tissue regeneration.

Synergistic Effect of Surface Chemistry and Surface Topography Gradient on Osteogenic/Adipogenic Differentiation of hMSCs

Much attention has been paid to understanding the individual effects of surface chemistry or topography on cell behavior. However, the synergistic influence of both surface chemistry and surface topography on differentiation of human mesenchymal stem cells (hMSCs) should also be addressed. Here, gold nanoparticles were immobilized in an increasing number density manner to achieve a surface topography gradient; a thin film rich in amine (-NH₂) or methyl (-CH₃) chemical groups was plasma-polymerized to adjust the surface chemistry of the outermost layer (ppAA and ppOD, respectively). hMSCs were cultured on these model substrates with defined surface chemistry and surface topography gradient. The morphology and focal adhesion (FA) formation of hMSCs were first examined. hMSC differentiation was then co-induced in osteogenic and adipogenic medium, as well as in the presence of extracellular-signal-regulated kinase1/2 (ERK1/2) and RhoA/Rho-associated protein kinase (ROCK) inhibitors. The results show that the introduction of nanotopography could enhance FA formation and osteogenesis but inhibited adipogenesis on both ppAA and ppOD surfaces, indicating that the surface chemistry could regulate hMSC differentiation, in a surface topography-dependent manner. RhoA/ROCK and ERK1/2 signaling pathways may participate in this process. This study demonstrated that surface chemistry and surface topography can jointly affect cell morphology, FA formation, and thus osteogenic/adipogenic differentiation of hMSCs. These findings highlight the importance of the synergistic effect of different material properties on regulation of cell response, which has important implications in designing functional biomaterials.

High-Throughput Methods in the Discovery and Study of Biomaterials and Materiobiology

The complex interaction of cells with biomaterials (i.e., materiobiology) plays an increasingly pivotal role in the development of novel implants, biomedical devices, and tissue engineering scaffolds to treat diseases, aid in the restoration of bodily functions, construct healthy tissues, or regenerate diseased ones. However, the conventional approaches are incapable of screening the huge amount of potential material parameter combinations to identify the optimal cell responses and involve a combination of serendipity and many series of trial-and-error experiments. For advanced tissue engineering and regenerative medicine, highly efficient and complex bioanalysis platforms are expected to explore the complex interaction of cells with biomaterials using combinatorial approaches that offer desired complex microenvironments during healing, development, and homeostasis. In this review, we first introduce materiobiology and its high-throughput screening (HTS). Then we present an in-depth of the recent progress of 2D/3D HTS platforms (i.e., gradient and microarray) in the principle, preparation, screening for materiobiology, and combination with other advanced technologies. The Compendium for Biomaterial Transcriptomics and high content imaging, computational simulations, and their translation toward commercial and clinical uses are highlighted. In the final section, current challenges and future perspectives are discussed. High-throughput experimentation within the field of materiobiology enables the elucidation of the relationships between biomaterial properties and biological behavior and thereby serves as a potential tool for accelerating the development of high-performance biomaterials.

Enzymatically crosslinked gelatin-laminin hydrogels for applications in neuromuscular tissue engineering

We report a water-soluble and non-toxic method to incorporate additional extracellular matrix proteins into gelatin hydrogels, while obviating the use of chemical crosslinkers such as glutaraldehyde. Gelatin hydrogels were fabricated using a range of gelatin concentrations (4%-10%) that corresponded to elastic moduli of approximately 1 kPa-25 kPa, respectively, a substrate stiffness relevant for multiple cell types. Microbial transglutaminase was then used to enzymatically crosslink a layer of laminin on top of gelatin hydrogels, resulting in 2-component gelatin-laminin hydrogels. Human induced pluripotent stem cell derived spinal spheroids readily adhered and rapidly extended axons on GEL-LN hydrogels. Axons displayed a more mature morphology and superior electrophysiological properties on GEL-LN hydrogels compared to the controls. Schwann cells on GEL-LN hydrogels adhered and proliferated normally, displayed a healthy morphology, and maintained the expression of Schwann cell specific markers. Lastly, skeletal muscle cells on GEL-LN hydrogels achieved long-term culture for up to 28 days without delamination, while expressing higher levels of terminal genes including myosin heavy chain, MyoD, MuSK, and M-cadherin suggesting enhanced maturation potential and myotube formation compared to the controls. Future studies will employ the superior culture outcomes of this hybrid substrate for engineering functional neuromuscular junctions and related organ on a chip applications.

Plasma deposited poly-oxazoline nanotextured surfaces dictate osteoimmunomodulation towards ameliorative osteogenesis

Developing "osteoimmune-smart" bone substitute materials have become the forefront of research in bone regeneration. Biocompatible polymer coatings are applied widely to improve the bioactivity of bone substitute materials. In this context, polyoxazolines (Pox) have attracted substantial attention recently due to properties such as biocompatibility, stability, and low biofouling. In view of these useful properties, it is interesting to explore the capacity of Pox as an osteoimmunomodulatory agent to generate a favorable osteoimmune environment for osteogenesis. We applied a technique called plasma polymerization and succeeded in preparing Pox-like coatings (Ppox) and engineered their nanotopography at the nanoscale. We found that Ppox switched macrophages towards M2 extreme, thus inhibiting the release of inflammatory cytokines. The underlying mechanism may be related to the suppression of TLR pathway. The generated osteoimmune environment improved osteogenesis while inhibited osteoclastogenesis. This may be related to the release of osteogenic factors, especially Wnt10b from macrophages. The addition of nanotopography (16 nm, 38 nm, 68 nm) can tune the Ppox-mediated inhibition on inflammation and osteoclastic activities, while no significant effects were observed within the tested nano sizes on the Ppox-mediated osteogenesis. These results collectively suggest that Ppox can be useful as an effective osteoiumunomodulatory agent to endow bone substitute materials with favourable osteoimmunomodulatory property. STATEMENT OF SIGNIFICANCE: In this study, we succeeded in preparing plasma deposited Pox-like nano-coatings (Ppox) via plasma polymerization and found that Ppox nanotopographies are useful osteoimmunomodulatory tools. Their osteoimmunodolatory effects and underlying mechanisms are unveiled. It is the first investigation into the feasibility of applying poly-oxazoline as an osteoimmunomodulatory agent. This expand the application of poly-oxazoline into the forefront in bone regeneration area for the development of advanced "osteoimmune-smart" bone substitute materials.

Plasma Polymer Coatings To Direct the Differentiation of Mouse Kidney-Derived Stem Cells into Podocyte and Proximal Tubule-like Cells

Kidney disease is now recognized as a global health problem and is associated with increased morbidity and mortality, along with high economic costs. To develop new treatments for ameliorating kidney injury and preventing disease progression, there is a need for appropriate renal culture systems for screening novel drugs and investigating the cellular mechanisms underlying renal pathogenesis. There is a need for in vitro culture systems that promote the growth and differentiation of specialized renal cell types. In this work, we have used plasma polymerization technology to generate gradients of chemical functional groups to explore whether specific concentrations of these functional groups can direct the differentiation of mouse kidney-derived stem cells into specialized renal cell types. We found that amine-rich (-NH₂) allylamine-based plasma-polymerized coatings could promote differentiation into podocyte-like cells, whereas methyl-rich (CH₃) 1,7-octadiene-based coatings promoted differentiation into proximal tubule-like cells (PTC). Importantly, the PT-like cells generated on the substrates expressed the marker megalin and were able to endocytose albumin, indicating that the cells were functional.

Nanotopographic cues and stiffness control of tendon-derived stem cells from diverse conditions

Background

Tendon-derived stem cells (TDSCs) are key factors associated with regeneration and healing in tendinopathy. The aim of this study was to investigate the effects of mechanical stiffness and topographic signals on the differentiation of TDSCs depending on age and pathological conditions.

Materials and methods

We compared TDSCs extracted from normal tendon tissues with TDSCs from tendinopathic Achilles tendon tissues of Sprague Dawley rats in vitro and TDSCs cultured on nanotopographic cues and substrate stiffness to determine how to control the TDSCs. The tendinopathy model was created using a chemical induction method, and the tendon injury model was created via an injury-and-overuse method. Norland Optical Adhesive 86 (NOA86) substrate with 2.48 GPa stiffness with and without 800 nm-wide nanogrooves and a polyurethane substrate with 800 nm-wide nanogrooves were used.

Results

TDSCs from 5-week-old normal tendon showed high expression of type III collagen on the flat NOA86 substrate. In the 15-week normal tendon model, expression of type III collagen was high in TDSCs cultured on the 800 nm NOA86 substrates. However, in the 15-week tendon injury model, expression of type III collagen was similar irrespective of nanotopographic cues or substrate stiffness. The expression of type I collagen was also independent of nanotopographic cues and substrate stiffness in the 15-week normal and tendon injury models. Gene expression of scleraxis was increased in TDSCs cultured on the flat NOA86 substrate in the 5-week normal tendon model (P=0.001). In the 15-week normal tendon model, scleraxis was highly expressed in TDSCs cultured on the 800 nm and flat NOA86 substrate (P=0.043). However, this gene expression was not significantly different between the substrates in the 5-week tendinopathy and 15-week tendon injury models.

Conclusion

Development and maturation of tendon are enhanced when TDSCs from normal tendons were cultured on stiff surface, but not when the TDSCs came from pathologic models. Therapeutic applications of TDSCs need to be flexible based on tendon age and tendinopathy.

Nanofibers as Bioinstructive Scaffolds Capable of Modulating Differentiation through Mechanosensitive Pathways for Regenerative Engineering

Bioinstructive scaffolds encode information in the physical shape and size of materials to direct cell responses. Electrospinning nanofibers is a process that offers control over scaffold architecture and fiber diameter, while providing extended linear length of fibers. This review summarizes tissue engineering literature that has utilized nanofiber scaffolds to direct stem cell differentiation for various tissues including musculoskeletal, vascular, immunological and nervous system tissues. Nanofibers are also considered for their extracellular matrix mimetic characteristics that can preserve stem cell differentiation capacity. These topics are considered in the context of focal adhesion and integrin signaling. Regenerative engineering will be enhanced by construction of scaffolds encoded with shape information to cause an attached cell to create the intended tissue at that region. Nanofibers are likely to be a bioinstructive scaffold in future regenerative engineering development as we pursue the Grand Challenges of engineering tissues.

Silver nanoparticle modified surfaces induce differentiation of mouse kidney-derived stem cells

In this paper, we interrogate the influence of silver nanoparticle (AgNPs)-based model surfaces on mouse kidney-derived stem cells (mKSCs) differentiation. The widespread use of silver in biomedical and consumer products requires understanding of this element's effect on kidney cells. Moreover, the potential for using stem cells in drug discovery require methods to direct their differentiation to specialized cells. Hence, we generated coated model substrates containing different concentrations of surface immobilized AgNPs, and used them to evaluate properties and functions of mKSCs. Initially, mKSCs exhibited reduced viability on higher silver containing surfaces. However, longer culture periods assisted mKSCs to recover. Greater degree of cell spreading and arborization led by AgNPs, suggest podocyte differentiation. Proximal tubule cell marker's expression revealed differentiation to the specific lineage. Although the exact mechanism underpinning these findings require significant future efforts, this study demonstrate silver's capacity to stimulate mKSC differentiation, which may provide opportunities for drug screenings.

2-Methyl-2-oxazoline plasma polymerized silver nanoparticles containing coatings are not toxic towards mouse kidney derived stem cells (mKSCs) and regulate mKSCs differentiation.

Nanotopography-based strategy for the precise manipulation of osteoimmunomodulation in bone regeneration

Immune cells play vital roles in regulating bone dynamics. Successful bone regeneration requires a favourable osteo-immune environment. The high plasticity and diversity of immune cells make it possible to manipulate the osteo-immune response of immune cells, thus modulating the osteoimmune environment and regulating bone regeneration. With the advancement in nanotechnology, nanotopographies with different controlled surface properties can be fabricated. On tuning the surface properties, the osteo-immune response can be precisely modulated. This highly tunable characteristic and immunomodulatory effects make nanotopography a promising strategy to precisely manipulate osteoimmunomdulation for bone tissue engineering applications. This review first summarises the effects of the immune response during bone healing to show the importance of regulating the immune response for the bone response. The plasticity of immune cells is then reviewed to provide rationales for manipulation of the osteoimmune response. Subsequently, we highlight the current types of nanotopographies applied in bone biomaterials and their fabrication techniques, and explain how these nanotopographies modulate the immune response and the possible underlying mechanisms. The effects of immune cells on nanotopography-mediated osteogenesis are emphasized, and we propose the concept of "nano-osteoimmunomodulation" to provide a valuable strategy for the development of nanotopographies with osteoimmunomodulatory properties that can precisely regulate bone dynamics.

The Role of Controlled Surface Topography and Chemistry on Mouse Embryonic Stem Cell Attachment, Growth and Self-Renewal

The success of stem cell therapies relies heavily on our ability to control their fate in vitro during expansion to ensure an appropriate supply. The biophysical properties of the cell culture environment have been recognised as a potent stimuli influencing cellular behaviour. In this work we used advanced plasma-based techniques to generate model culture substrates with controlled nanotopographical features of 16 nm, 38 nm and 68 nm in magnitude, and three differently tailored surface chemical functionalities. The effect of these two surface properties on the adhesion, spreading, and self-renewal of mouse embryonic stem cells (mESCs) were assessed. The results demonstrated that physical and chemical cues influenced the behaviour of these stem cells in in vitro culture in different ways. The size of the nanotopographical features impacted on the cell adhesion, spreading and proliferation, while the chemistry influenced the cell self-renewal and differentiation.

Protein Interactions with Nanoengineered Polyoxazoline Surfaces Generated via Plasma Deposition

Protein adsorption to biomaterials is critical in determining their suitability for specific applications, such as implants or biosensors. Here, we show that surface nanoroughness can be tailored to control the covalent binding of proteins to plasma-deposited polyoxazoline (PPOx). Nanoengineered surfaces were created by immobilizing gold nanoparticles varying in size and surface density on PPOx films. To keep the surface chemistry consistent while preserving the nanotopography, all substrates were overcoated with a nanothin PPOx film. Bovine serum albumin was chosen to study protein interactions with the nanoengineered surfaces. The results demonstrate that the amount of protein bound to the surface is not directly correlated with the increase in surface area. Instead, it is determined by nanotopography-induced geometric effects and surface wettability. A densely packed array of 16 and 38 nm nanoparticles hinders protein adsorption compared to smooth PPOx substrates, while it increases for 68 nm nanoparticles. These adaptable surfaces could be used for designing biomaterials where proteins adsorption is or is not desirable.