Mechanical forces regulate stem cell response to surface topography

Hyaluronic acid hydrogels, as a biological macromolecule-based platform for stem cells delivery and their fate control: A review

Stem cell-based therapies offer numerous potentials to repair damaged or defective organs. The therapeutic outcomes of human studies, however, fall far short from what is expected. Enhancing stem cells local density and longevity would possibly maximize their healing potential. One promising strategy is to administer stem cells via injectable hydrogels. However, stem cells differentiation process is a delicate matter which is easily affected by various factors such as their interaction with their surrounding materials. Among various biomaterial options for hydrogels' production, hyaluronic acid (HA) has shown great promise. HA is a naturally occurring biological macromolecule, a polysaccharide of large molecular weight which is involved in cell proliferation, cell migration, angiogenesis, fetal development, and tissue function. In the current study we will discuss the applications, prospects, and challenges of HA-based hydrogels in stem cell delivery and fate control.

The Role and Activation Mechanism of TAZ in Hierarchical Microgroove/Nanopore Topography-Mediated Regulation of Stem Cell Differentiation

Purpose

To investigate the role and activation mechanism of TAZ in periodontal ligament stem cells (PDLSCs) perceiving hierarchical microgroove/nanopore topography.

Materials and Methods

Titanium surface with hierarchical microgroove/nanopore topography fabricated by selective laser melting combined with alkali heat treatment (SLM-AHT) was used as experimental group, smooth titanium surface (Ti) and sandblasted, large-grit, acid-etched (SLA) titanium surface were employed as control groups. Alkaline phosphatase (ALP) activity assays, qRT-PCR, Western blotting, and immunofluorescence were carried out to evaluate the effect of SLM-AHT surface on PDLSC differentiation. Moreover, TAZ activation was investigated from the perspective of nuclear localization to transcriptional activity. TAZ knockdown PDLSCs were seeded on three titanium surfaces to detect osteogenesis- and adipogenesis-related gene expression levels. Immunofluorescence and Western blotting were employed to investigate the effect of the SLM-AHT surface on actin cytoskeletal polymerization and MAPK signaling pathway. Cytochalasin D and MAPK signaling pathway inhibitors were used to determine whether actin cytoskeletal polymerization and the MAPK signaling pathway were indispensable for TAZ activation.

Results

Our results showed that SLM-AHT surface had a greater potential to promote PDLSC osteogenic differentiation while inhibiting adipogenic differentiation than the other two groups. The nuclear localization and transcriptional activity of TAZ were strongly enhanced on the SLM-AHT surface. Moreover, after TAZ knockdown, the enhanced osteogenesis and decreased adipogenesis in SLM-AHT group could not be observed. In addition, SLM-AHT surface could promote actin cytoskeletal polymerization and upregulate p-ERK and p-p38 protein levels. After treatment with cytochalasin D and MAPK signaling pathway inhibitors, differences in the TAZ subcellular localization and transcriptional activity were no longer observed among the different titanium surfaces.

Conclusion

Our results demonstrated that actin cytoskeletal polymerization and MAPK signaling pathway activation triggered by SLM-AHT surface were essential for TAZ activation, which played a dominant role in SLM-AHT surface-induced stem cell fate decision.

Protective Effects of Moderate Intensity Static Magnetic Fields on Diabetic Mice

The purpose of this study was to investigate the effects of moderate-intensity static magnetic field (SMF) on diabetic mice. We studied the effects of SMF on blood glucose of normal mice by starch tolerance and glucose tolerance tests. Then, we evaluated the effects of SMF on blood glucose of diabetic mice by establishing alloxan-induced type 1 diabetic mice and high-fat diet + streptozotocin (STZ)-induced type 2 diabetic mice. The results showed that different magnetic field intensities and blank control did not affect the blood glucose of normal mice. After starch and glucose administration, different magnetic fields could improve the glucose tolerance of normal mice, and this was obvious in the 600 mT group. In the experiment of type 1 diabetic mice induced by alloxan, the results showed that different magnetic field intensities could improve the starch tolerance of mice, and that in the 400 mT group was obvious. In the experiment of type 2 diabetic mice induced by a high-fat diet + STZ, the 400 mT group could reduce food intake and water consumption in the later period. The 600 mT group could improve the starch tolerance of mice. The 400 and 600 mT groups could reduce fasting blood glucose. At the same time, total cholesterol and triglyceride decreased in different magnetic field intensities, and the 600 mT group could significantly increase the serum insulin content of mice. In summary, the results of this study suggest that SMF has a protective role in diabetic mice. Bioelectromagnetics. © 2020 Bioelectromagnetics Society.

Effect of photobiomodulation therapy on the proliferation phase and wound healing in rats fed with an experimental hypoproteic diet

Photobiomodulation therapy (PBMT) has been indicated for enforcement on healing skin wounds. This study evaluated the effects of PBMT on the healing of skin wounds during the proliferation phase in rats with a hypoproteic diet. Rats were randomized to one of the following groups (n = 10 per group): (i) injured normoproteic (25% protein) not subjected to PBMT; (ii) injured normoproteic who received PBMT; (iii) injured hypoproteic (8% protein) not subjected to PBMT; and (iv) injured hypoproteic who received PBMT. Rats were submitted to skin wounds and then treated with PBMT (low-level laser therapy: 660 nm, 50 mW, 1.07 W/cm², 0.028 cm², 72 J/cm², 2 J). Analyses were performed at 7 and 14 days of follow-up: semi-quantitative histopathologic analysis, collagen type I and III expressions, immunohistochemical marking for matrix metalloproteinases-3 (MMP-3) and (matrix metalloproteinases-9) MMP-9, and mechanical resistance test. There were significant differences between the normoproteic groups and their respective treated groups (p < 0.05), as well as to treated and untreated hypoproteic groups in histopathologic analysis semi-quantitatively and immunohistochemistry for MMP-3 and 9, in which PBMT was able to decrease immunostaining. Moreover, there was a decrease in collagen deposition with the statistical difference (p < 0.05) for both collagen types III and I. In conclusion, PBMT application was proved effective in the treatment of cutaneous wounds in rats submitted to a hypoproteic diet. These alterations were more salient in the proliferation stage with the reduction of metalloproteinases providing better mechanical resistance of the injured area in the remodeling phase with an intensification of type I collagen.

Biological responses to physicochemical properties of biomaterial surface

Biomedical scientists use chemistry-driven processes found in nature as an inspiration to design biomaterials as promising diagnostic tools, therapeutic solutions, or tissue substitutes. While substantial consideration is devoted to the design and validation of biomaterials, the nature of their interactions with the surrounding biological microenvironment is commonly neglected. This gap of knowledge could be owing to our poor understanding of biochemical signaling pathways, lack of reliable techniques for designing biomaterials with optimal physicochemical properties, and/or poor stability of biomaterial properties after implantation. The success of host responses to biomaterials, known as biocompatibility, depends on chemical principles as the root of both cell signaling pathways in the body and how the biomaterial surface is designed. Most of the current review papers have discussed chemical engineering and biological principles of designing biomaterials as separate topics, which has resulted in neglecting the main role of chemistry in this field. In this review, we discuss biocompatibility in the context of chemistry, what it is and how to assess it, while describing contributions from both biochemical cues and biomaterials as well as the means of harmonizing them. We address both biochemical signal-transduction pathways and engineering principles of designing a biomaterial with an emphasis on its surface physicochemistry. As we aim to show the role of chemistry in the crosstalk between the surface physicochemical properties and body responses, we concisely highlight the main biochemical signal-transduction pathways involved in the biocompatibility complex. Finally, we discuss the progress and challenges associated with the current strategies used for improving the chemical and physical interactions between cells and biomaterial surface.

Microarray analysis reveals that lncRNA PWRN1-209 promotes human bone marrow mesenchymal stem cell osteogenic differentiation on microtopography titanium surface in vitro

Sandblasted, large-grit, and acid-etched (SLA) titanium (Ti) with microtopography is currently one of the most widely used implant materials to accelerate osseointegration. Numerous long noncoding RNAs (lncRNAs) have been involved in bone remodeling, with their role in osseointegration, and the underlying mechanisms remain largely unclear. Here, microarrays of human bone marrow mesenchymal stem cells (hBMSCs) were used to identify differentially expressed lncRNAs during early cell differentiation stages (0-7 days) on SLA Ti and polished Ti surfaces. The function of lncRNAs in the osteogenic differentiation of hBMSCs was identified by RNA silencing and overexpression assays. RT-PCR and Western blot were used to detect RNA and protein expression. Alkaline phosphatase (ALP) protein activity was tested by ALP staining. Altogether, 4112 differentially expressed lncRNAs were identified from day 0 to day 7 on SLA Ti with a novel lncRNA, Prader-willi region non-coding RNA 1-209 (PWRN1-209) upregulated. We then proved that PWRN1-209 promoted osteogenic differentiation in hBMSCs by genetic tools. The upregulation of PWRN1-209 was further confirmed to be related to the surface topography of Ti by comparing SLA Ti and polished Ti. Interestingly, this trend seems to have a certain correlation with the mRNA expression level of integrins (α2, αV, β1, β2) and the phosphorylation of focal adhesion kinase (FAK). Taken together, the lncRNA PWRN1-209 was upregulated by the SLA microtopography Ti surface, which may regulate osteogenic differentiation of hBMSCs through integrin-FAK-ALP signaling. Our results provide new insights into the relationship between surface topography and osseointergration.

Spreading area and shape regulate the apoptosis and osteogenesis of mesenchymal stem cells on circular and branched micropatterned islands

The topography of extracellular matrix regulates the differentiation of mesenchymal stem cells (MSCs). In particular, the effect of spreading shape or area on cellular differentiation and viability of individual MSCs cultured in the confined adhesive regions is an interesting fundamental issue. In this study, the adhesive patterns with the circularity of 0.1 or 1 and the areas of 314; 628; 1,256; or 2,512 μm² were constructed using micropatterning technology. The expression of osteogenesis marker alkaline phosphatase and the apoptosis level of individual MSCs were measured using double fluorescent staining. Results indicated that individual MSCs confined in the small area showed an apoptotic tendency, and those in the large area might enter into osteogenesis. The branched shape with small circularity increased MSC viability but reduced their pluripotency compared with the circular shape. The expression of other osteogenesis markers, such as osteocalcin and Collagen I, confirmed that large and branched pattern promoted MSC osteogenesis. In addition, the transcriptional coactivator yes-associated protein (YAP) was transferred higher in the nuclei of the large and branched cells than other micropatterned groups. This study suggested that the spreading area and shape of individual MSCs regulate their viability and osteogenesis through the YAP pathway.

Materials-Directed Differentiation of Mesenchymal Stem Cells for Tissue Engineering and Regeneration

Cell-based therapies are a promising alternative to grafts and organ transplantation for treating tissue loss or damage due to trauma, malfunction, or disease. Over the past two decades, mesenchymal stem cells (MSCs) have attracted much attention as a potential cell population for use in regenerative medicine. While the proliferative capacity and multilineage potential of MSCs provide an opportunity to generate clinically relevant numbers of transplantable cells, their use in tissue regenerative applications has met with relatively limited success to date apart from secreting paracrine-acting factors to modulate the defect microenvironment. Presently, there is significant effort to engineer the biophysical properties of biomaterials to direct MSC differentiation and further expand on the potential of MSCs in tissue engineering, regeneration, and repair. Biomaterials can dictate MSC differentiation by modulating features of the substrate including composition, mechanical properties, porosity, and topography. The purpose of this review is to highlight recent approaches for guiding MSC fate using biomaterials and provide a description of the underlying characteristics that promote differentiation toward a desired phenotype.

Extracellular matrix/stromal vascular fraction gel conditioned medium accelerates wound healing in a murine model

Conditioned medium (CM) is a new treatment modality in regenerative medicine and has shown a successful outcome in wound healing. We recently introduced extracellular matrix/stromal vascular fraction gel (ECM/SVF-gel), an adipose-derived stem cell and adipose native extracellular matrix-enriched product for cytotherapy. This study aimed to evaluate the effect of CM from ECM/SVF-gel (Gel-CM) on wound healing compared with the conventional CM from adipose tissue (Adi-CM) and stem cell (SVF-CM). In vitro wound healing effect of three CMs on keratinocytes and fibroblasts was evaluated in terms of proliferation property, migratory property, and extracellular matrix production. In vivo, two full-thickness wounds were created on the back of each mice. The wounds were randomly divided to receive Gel-CM, Adi-CM, SVF-CM, and PBS injection. Histologic observations and collagen content of wound skin were made. Growth factors concentration in three CMs was further quantified. In vitro, Gel-CM promoted the proliferation and migration of keratinocytes and fibroblasts and enhanced collagen I synthesis in fibroblasts compared to Adi-CM and SVF-CM. In vivo, wound closure was faster, and dermal and epidermal regeneration was improved in the Gel-CM-treated mice compared to that in Adi-CM and SVF-CM-treated mice. Moreover, The growth factors concentration (i.e., vascular endothelial growth factor, basic fibroblast growth factor, hepatocyte growth factor, and transforming growth factor-β) in Gel-CM were significantly higher than those in Adi-CM and SVF-CM. Gel-CM generated under serum free conditions significantly enhanced wound healing effect compared to Adi-CM and SVF-CM by accelerating cell proliferation, migration, and production of ECM. This improved trophic effect may be attributed to the higher growth factors concentration in Gel-CM. Gel-CM shows potential as a novel and promising alternative to skin wound healing treatment. But limitations include the safety and immunogenicity studies of Gel-CM still remain to be clearly clarified and more data on mechanism study are needed.

Inkjet printed periodical micropatterns made of inert alumina ceramics induce contact guidance and stimulate osteogenic differentiation of mesenchymal stromal cells

Bioinert high performance ceramics exhibit detrimental features for implant components with direct bone contact because of their low osseointegrating capability. We hypothesized that periodical microstructures made of inert alumina ceramics can influence the osteogenic differentiation of human mesenchymal stromal cells (hMSC). In this study, we manufactured pillared arrays made of alumina ceramics with periodicities as low as 100μm and pillar heights of 40μm employing direct inkjet printing (DIP) technique. The response of hMSC to the microstructured surfaces was monitored by measuring cell morphology, viability and formation of focal adhesion complexes. Osteogenic differentiation of hMSCs was investigated by alkaline phosphatase activity, mineralization assays and expression analysis of respective markers. We demonstrated that MSCs react to the pillars with contact guidance. Subsequently, cells grow onto and form connections between the microstructures, and at the same time are directly attached to the pillars as shown by focal adhesion stainings. Cells build up tissue-like constructs with heights up to the micropillars resulting in increased cell viability and osteogenic differentiating properties. We conclude that periodical micropatterns on the micrometer scale made of inert alumina ceramics can mediate focal adhesion dependent cell adhesion and stimulate osteogenic differentiation of hMSCs.

Biomimetic substrate control of cellular mechanotransduction

Extracellular mechanophysical signals from both static substrate cue and dynamic mechanical loading have strong potential to regulate cell functions. Most of the studies have adopted either static or dynamic cue and shown that each cue can regulate cell adhesion, spreading, migration, proliferation, lineage commitment, and differentiation. However, there is limited information on the integrative control of cell functions by the static and dynamic mechanophysical signals. For example, a majority of dynamic loading studies have tested mechanical stimulation of cells utilizing cultures on flat surfaces without any surface modification. While these approaches have provided significant information on cell mechanotransduction, obtained outcomes may not correctly recapitulate complex cellular mechanosensing milieus in vivo. Several pioneering studies documented cellular response to mechanical stimulations upon cultures with biomimetic substrate modifications. In this min-review, we will highlight key findings on the integrative role of substrate cue (topographic, geometric, etc.) and mechanical stimulation (stretch, fluid shear) in modulating cell function and fate. The integrative approaches, though not fully established yet, will help properly understand cell mechanotransduction under biomimetic mechanophysical environments. This may further lead to advanced functional tissue engineering and regenerative medicine protocols.

Regulation of stem cell fate by nanomaterial substrates

Stem cells are increasingly studied because of their potential to underpin a range of novel therapies, including regenerative strategies, cell type-specific therapy and tissue repair, among others. Bionanomaterials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. New advances in these fields are presented in this review. This work highlights the importance of topography and elasticity of the nano-/micro-environment, or niche, for the initiation and induction of stem cell differentiation and proliferation.

Topographical cues regulate the crosstalk between MSCs and macrophages

Implantation of scaffolds may elicit a host foreign body response triggered by monocyte/macrophage lineage cells. Growing evidence suggests that topographical cues of scaffolds play an important role in MSC functionality. In this work, we examined whether surface topographical features can regulate paracrine interactions that MSCs establish with macrophages. Three-dimensional (3D) topography sensing drives MSCs into a spatial arrangement that stimulates the production of the anti-inflammatory proteins PGE₂ and TSG-6. Compared to two-dimensional (2D) settings, 3D arrangement of MSCs co-cultured with macrophages leads to an important decrease in the secretion of soluble factors related with inflammation and chemotaxis including IL-6 and MCP-1. Attenuation of MCP-1 secretion in 3D co-cultures correlates with a decrease in the accumulation of its mRNA levels in MSCs and macrophages. Using neutralizing antibodies, we identified that the interplay between PGE₂, IL-6, TSG-6 and MCP-1 in the co-cultures is strongly influenced by the micro-architecture that supports MSCs. Local inflammatory milieu provided by 3D-arranged MSCs in co-cultures induces a decrease in monocyte migration as compared to monolayer cells. This effect is partially mediated by reduced levels of IL-6 and MCP-1, proteins that up-regulate each other's secretion. Our findings highlight the importance of topographical cues in the soluble factor-guided communication between MSCs and macrophages.

Role of extracellular matrix signaling cues in modulating cell fate commitment for cardiovascular tissue engineering

It is generally agreed that engineered cardiovascular tissues require cellular interactions with the local milieu. Within the microenvironment, the extracellular matrix (ECM) is an important support structure that provides dynamic signaling cues in part through its chemical, physical, and mechanical properties. In response to ECM factors, cells activate biochemical and mechanotransduction pathways that modulate their survival, growth, migration, differentiation, and function. This Review describes the role of ECM chemical composition, spatial patterning, and mechanical stimulation in the specification of cardiovascular lineages, with a focus on stem cell differentiation, direct transdifferentiation, and endothelial-to-mesenchymal transition. The translational application of ECMs is discussed in the context of cardiovascular tissue engineering and regenerative medicine.

Nanotechnology in the regulation of stem cell behavior

Stem cells are known for their potential to repair damaged tissues. The adhesion, growth and differentiation of stem cells are likely controlled by the surrounding microenvironment which contains both chemical and physical cues. Physical cues in the microenvironment, for example, nanotopography, were shown to play important roles in stem cell fate decisions. Thus, controlling stem cell behavior by nanoscale topography has become an important issue in stem cell biology. Nanotechnology has emerged as a new exciting field and research from this field has greatly advanced. Nanotechnology allows the manipulation of sophisticated surfaces/scaffolds which can mimic the cellular environment for regulating cellular behaviors. Thus, we summarize recent studies on nanotechnology with applications to stem cell biology, including the regulation of stem cell adhesion, growth, differentiation, tracking and imaging. Understanding the interactions of nanomaterials with stem cells may provide the knowledge to apply to cell-scaffold combinations in tissue engineering and regenerative medicine.