Adhesion of mesenchymal stem cells to biomimetic polymers: A review

Hydroxyapatite-Coated Ti6Al4V ELI Alloy: In Vitro Cell Adhesion

The high rate of rejection and failure of orthopedic implants is primarily attributed to incomplete osseointegration and stress at the implant-to-bone interface due to significant differences in the mechanical properties of the implant and the surrounding bone. Various surface treatments have been developed to enhance the osteoconductive properties of implants. The aim of this work was the in vitro characterization of titanium alloy modified with a nanocrystalline hydroxyapatite surface layer in relative comparison to unmodified controls. This investigation focused on the behavior of the surface treatment in relation to the physiological environment. Moreover, the osteogenic response of human osteoblasts and adipose stem cells was assessed. Qualitative characterization of cellular interaction was performed via confocal laser scanning microscopy focusing on the cell nuclei and cytoskeletons. Filipodia were assessed using scanning electron microscopy. The results highlight that the HA treatment promotes protein adhesion as well as gene expression of osteoblasts and stem cells, which is relevant for the inorganic and organic components of the extracellular matrix and bone. In particular, cells grown onto HA-modified titanium alloy are able to promote ECM production, leading to a high expression of collagen I and non-collagenous proteins, which are crucial for regulating mineral matrix formation. Moreover, they present an impressive amount of filipodia having long extensions all over the test surface. These findings suggest that the HA surface treatment under investigation effectively enhances the osteoconductive properties of Ti6Al4V ELI.

Development of a new biomaterial based on cashew tree gum (Anarcadium occidentale L.) enriched with hydroxyapatite and evaluation of cytotoxicity in adipose-derived stem cell cultures

Cashew tree gum is a polysaccharide material highly available in the Northeast region of Brazil. It has been explored for biocompatibility with human tissues. This research aimed to describe the synthesis and characterization of cashew gum/hydroxyapatite scaffold and evaluate the possible cytotoxicity in murine adipo-derived stem cells (ADSCs) cultures. ADSCs of the subcutaneous fat tissue of Wistar rats were collected, isolated, expanded, differentiated into three strains, and characterized immunophenotypically. The scaffolds were synthesized through chemical precipitation, lyophilized and characterized through scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal analysis (TG and DTG), and mechanical testing. The scaffold presented a crystalline structure and pores with an average diameter of 94.45 ± 50.57 μm. By mechanical tests, the compressive force and modulus of elasticity were like the cancellous bone. The isolated adipose-derived stem cells (ADSCs) presented fibroblast morphology, adhesion capacity to plastic, differentiation in osteogenic, adipogenic and chondrogenic lineages, positive expression for the CD105 and CD90 markers and negative expression for the CD45 and CD14 markers. The MTT test showed increased cell viability, and the biomaterial showed a high level of hemocompatibility (<5 %). This study allowed the development of a new scaffold for future surgical applicability in tissue regeneration.

Metal Ion Doping of Alginate-Based Surface Coatings Induces Adipogenesis of Stem Cells

Metal ions are important effectors of protein and cell functions. Here, polyelectrolyte multilayers (PEMs) made of chitosan (Chi) and alginate (Alg) were doped with different metal ions (Ca²⁺, Co²⁺, Cu²⁺, and Fe³⁺), which can form bonds with their functional groups. Ca²⁺ and Fe³⁺ ions can be deposited in PEM at higher quantities resulting in more positive ζ potentials and also higher water contact angles in the case of Fe³⁺. An interesting finding was that the exposure of PEM to metal ions decreases the elastic modulus of PEM. Fourier transformed infrared (FTIR) spectroscopy of multilayers provides evidence of interaction of metal ions with the carboxylic groups of Alg but not for hydroxyl and amino groups. The observed changes in wetting and surface potential are partly related to the increased adhesion and proliferation of multipotent C3H10T1/2 fibroblasts in contrast to plain nonadhesive [Chi/Alg] multilayers. Specifically, PEMs doped with Cu²⁺ and Fe³⁺ ions greatly promote cell attachment and adipogenic differentiation, which indicates that changes in not only surface properties but also the bioactivity of metal ions play an important role. In conclusion, metal ion-doped multilayer coatings made of alginate and chitosan can promote the differentiation of multipotent cells on implants without the use of other morphogens like growth factors.

Improved cell adhesion to activated vapor silanization-biofunctionalized Ti-6Al-4V surfaces with ECM-derived oligopeptides

Titanium implants are widely used in traumatology and various orthopedic fields. Titanium and other metallic-based implants have limited structural and functional integration into the body, which translates into progressive prosthesis instability and the need for new surgical interventions that have enormous social and economic impacts. To enhance the biocompatibility of titanium implants, numerous biofunctionalization strategies have been developed. However, the problem persists, as more than 70% of implant failures are due to aseptic loosening. In this study we addressed the problem of improving the physiological engraftability and acceptability of titanium-based implants by applying a robust and versatile functionalization method based on the covalent immobilization of extracellular matrix (ECM)-derived oligopeptides on Ti-6Al-4V surfaces treated by activated vapor silanization (AVS). The feasibility of this technique was evaluated with two oligopeptides of different structures and compositions. These oligopeptides were immobilized on Ti-6Al-4V substrates by a combination of AVS and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) crosslinking chemistry. The immobilization was shown to be stable and resistant to chemical denaturing upon sodium dodecyl sulfate treatment. On Ti-6Al-4V surfaces both peptides increased the attachment, spreading, rearrangement and directional growth of mesenchymal stem and progenitor cells (MSC) with chondro- and osteo-regenerative capacities. We also found that this biofunctionalization method (AVS-EDC/NHS) increased the attachment capacity of an immortalized cell line of neural origin with poor adhesive properties, highlighting the versatility and robustness of this method in terms of potential oligopeptides that may be used, and cell lineages whose anchorage to the biomaterial may be enhanced. Collectively, this novel functionalization strategy can accelerate the development of advanced peptide-functionalized metallic surfaces, which, in combination with host or exogenously implanted stem cells, have the potential to positively affect the osteoregenerative and osteointegrative abilities of metallic-based prostheses.

The efficiency of PCL/HAp electrospun nanofibers in bone regeneration: a review

Electrospinning is a method which produces various nanofiber scaffolds for different tissues was attractive for researchers. Nanofiber scaffolds could be made from several biomaterials and polymers. Quality and virtues of final scaffolds depend on used biomaterials (even about single substance, the origin is effective), additives (such as some molecules, ions, drugs, and inorganic materials), electrospinning parameter (voltage, injection speed, temperature, …), etc. In addition to its benefits, which makes it more attractive is the possibility of modifications. Common biomaterials in bone tissue engineering such as poly-caprolactone (PCL), hydroxyapatite (HAp), and their important features, electrospinning nanofibers were widely studied. Related investigations indicate the critical role of even small parameters (like the concentration of PCL or HAp) in final product properties. These changes also, cause deference in cell proliferation, adhesion, differentiation, and in vivo repair process. In this review was focussed on PCL/HAp based nanofibers and additives that researchers used for scaffold improvement. Then, reviewing properties of gained nanofibers, their effect on cell behaviour, and finally, their valency in bone tissue engineering studies (in vitro and in vivo).

The secretome of mesenchymal stem cells and oxidative stress: challenges and opportunities in cell-free regenerative medicine

Over the last decade, mesenchymal stem cells (MSCs) have been considered a suitable source for cell-based therapy, especially in regenerative medicine. First, the efficacy and functions of MSCs in clinical applications have been attributed to their differentiation ability, called homing and differentiation. However, it has recently been confirmed that MSCs mostly exert their therapeutic effects through soluble paracrine bioactive factors and extracellular vesicles, especially secretome. These secreted components play critical roles in modulating immune responses, improving the survival, and increasing the regeneration of damaged tissues. The secretome content of MSCs is variable under different conditions. Oxidative stress (OS) is one of these conditions that is highly important in MSC therapy and regenerative medicine. High levels of reactive oxygen species (ROS) are produced during isolation, cell culture, and transplantation lead to OS, which induces cell death and apoptosis and limits the efficacy of their regeneration capability. In turn, the preconditioning of MSCs in OS conditions contributes to the secretion of several proteins, cytokines, growth factors, and exosomes, which can improve the antioxidant potential of MSCs against OS. This potential of MSC secretome has turned it into a new promising cell-free tissue regeneration strategy.This review provides a view of MSC secretome under OS conditions, focusing on different secretome contents of MSCs and thier possible therapeutic potential against cell therapy.

Efficacy of mesenchymal stromal cells and cellular products in improvement of symptoms for COVID-19 and similar lung diseases

At the end of 2019, respiratory coronavirus diseases 2019 (COVID-19) appeared and spread rapidly in the world. Besides several mutations, the outcome of this pandemic was the death up to 15% of hospitalized patients. Mesenchymal stromal cell therapy as a therapeutic strategy seemed successful in treatment of several diseases. Not only mesenchymal stromal cells of several tissues, but also their secreted extracellular vesicles and even secretome indicated beneficial therapeutic function. All of these three options were studied for treatment of COVID-19 as well as those respiratory diseases that have similar symptom. Fortunately, most of the outcomes were promising and optimistic. In this paper, we review in-vivo and clinical studies which have been used different sources of mesenchymal stromal cell, secreted extracellular vesicles, and secretome to improve and treat symptoms of COVID-19 and similar lung diseases.

Liver bioengineering: Recent trends/advances in decellularization and cell sheet technologies towards translation into the clinic

Development of novel technologies provides the best tissue constructs engineering and maximizes their therapeutic effects in regenerative therapy, especially for liver dysfunctions. Among the currently investigated approaches of tissue engineering, scaffold-based and scaffold-free tissues are widely suggested for liver regeneration. Analogs of liver acellular extracellular matrix (ECM) are utilized in native scaffolds to increase the self-repair and healing ability of organs. Native ECM analog could improve liver repairing through providing the supportive framework for cells and signaling molecules, exerting normal biomechanical, biochemical, and physiological signal complexes. Recently, innovative cell sheet technology is introduced as an alternative for conventional tissue engineering with the advantage of fewer scaffold restrictions and cell culture on a Thermo-Responsive Polymer Surface. These sheets release the layered cells through a temperature-controlled procedure without enzymatic digestion, while preserving the cell-ECM contacts and adhesive molecules on cell-cell junctions. In addition, several novelties have been introduced into the cell sheet and decellularization technologies to aid cell growth, instruct differentiation/angiogenesis, and promote cell migration. In this review, recent trends, advancements, and issues linked to translation into clinical practice are dissected and compared regarding the decellularization and cell sheet technologies for liver tissue engineering.

Nanostructured Cellulose-Gellan-Xyloglucan-Lysozyme Dressing Seeded with Mesenchymal Stem Cells for Deep Second-Degree Burn Treatment

PURPOSE

In deep burns, wound contraction and hypertrophic scar formation can generate functional derangement and debilitation of the affected part. In order to improve the quality of healing in deep second-degree burns, we developed a new treatment in a preclinical model using nanostructured membranes seeded with mesenchymal stem cells (MSCs).

METHODS

Membranes were obtained by reconstitution of bacterial cellulose (reconstituted membrane [RM]) and produced by a dry-cast process, then RM was incorporated with 10% tamarind xyloglucan plus gellan gum 1:1 and 10% lysozyme (RMGT-LZ) and with 10% gellan gum and 10% lysozyme (RMG-LZ). Membrane hydrophobic/hydrophilic characteristics were investigated by static/dynamic contact-angle measurements. They were cultivated with MSCs, and cell adhesion, proliferation, and migration capacity was analyzed with MTT assays. Morphological and topographic characteristics were analyzed by scanning electron microscopy. MSC patterns in flow cytometry and differentiation into adipocytes and osteocytes were checked. In vivo assays used RMG-LZ and RMGT-LZ (with and without MSCs) in Rattus norvegicus rats submitted to burn protocol, and histological sections and collagen deposits were analyzed and immunocytochemistry assay performed.

RESULTS

In vitro results demonstrated carboxyl and amine groups made the membranes moderately hydrophobic and xyloglucan inclusion decreased wettability, favoring MSC adhesion, proliferation, and differentiation. In vivo, we obtained 40% and 60% reduction in acute/chronic inflammatory infiltrates, 96% decrease in injury area, increased vascular proliferation and collagen deposition, and complete epithelialization after 30 days. MSCs were detected in burned tissue, confirming they had homed and proliferated in vivo.

CONCLUSION

Nanostructured cellulose-gellan-xyloglucan-lysozyme dressings, especially when seeded with MSCs, improved deep second-degree burn regeneration.

Effect of matrix stiffness and adhesion ligand density on chondrogenic differentiation of mesenchymal stem cells

Adhesion ligands and mechanical properties of extracellular matrix (ECM) play significant roles in directing mesenchymal stem cells' (MSCs) behaviors, but how they affect chondrogenic differentiation of MSCs has rarely been studied. In this study, we investigated the effects of matrix stiffness and adhesion ligand density on proliferation and chondrogenic differentiation of MSCs by using UV crosslinked hydrogels comprised of methacrylated gelatin (GelMA) and poly(ethylene glycol) diacrylate (PEGDA) of different weight ratios. The PEGDA/GelMA hydrogels were fabricated by adjusting the weight ratio of PEGDA and GelMA with low or high adhesion ligand density (0.05 and 0.5% GelMA, respectively) and independent tunable stiffness (1.6, 6, and 25 kPa separately for hydrogels with 5, 10, and 15% PEGDA). MSCs presented differential behaviors to ECM by adjusting its adhesion ligand density and stiffness. Cell proliferation and chondrogenic differentiation could be enhanced with the improvement of adhesive properties and stiffness, evidenced by cell viability assay, hematoxylin-eosin staining, Safranin O staining, immunohistochemistry (Collagen types II, Col2a1), as well as the chondrogenic genes expression of Col2a1, Acan, and Sox9. This study may provide new strategies to design the scaffolds for cartilage tissue engineering.

Direct cell imprint lithography in superconductive carbon black polymer composites: process optimization, characterization and in vitro toxicity analysis

Cell imprint lithography (CIL) or cell replication plays a vital role in fields like biomimetic smart culture substrates, bone tissue engineering, cell guiding, cell adhesion, tissue engineering, cell microenvironments, tissue microenvironments, cell research, drug delivery, diagnostics, therapeutics and many other applications. Herein we report a new formulation of superconductive carbon black photopolymer composite and its characterization towards a CIL process technique. In this article, we demonstrated an approach of using a carbon nanoparticle-polymer composite (CPC) for patterning cells. It is observed that a 0.3 wt % load of carbon nanoparticles (CNPs) in a carbon polymer mixture (CPM) was optimal for cell-imprint replica fabrication. The electrical resistance of the 3-CPC (0.3 wt %) was reduced by 68% when compared to N-CPC (0 wt %). This method successfully replicated the single cell with sub-organelle scale. The shape of microvesicles, grooves, pores, blebs or microvilli on the cellular surface was patterned clearly. This technique delivers a free-standing cell feature substrate. In vitro evaluation of the polymer demonstrated it as an ideal candidate for biomimetic biomaterial applications. This approach also finds its application in study based on morphology, especially for drug delivery applications and for investigations based on molecular pathways.

An injectable cationic hydrogel electrostatically interacted with BMP2 to enhance in vivo osteogenic differentiation of human turbinate mesenchymal stem cells

We have designed and characterized an injectable, electrostatically bonded, in situ-forming hydrogel system consisting of a cationic polyelectrolyte [(methoxy)polyethylene glycol-b-(poly(ε-caprolactone)-ran-poly(L-lactic acid)] (MP) copolymer derivatized with an amine group (MP-NH₂) and anionic BMP2. To the best of our knowledge, there have been hardly any studies that have investigated electrostatically bonded, in situ-forming hydrogel systems consisting of MP-NH₂ and BMP2, with respect to how they promote in vivo osteogenic differentiation of human turbinate mesenchymal stem cells (hTMSCs). Injectable formulations almost immediately formed an electrostatically loaded hydrogel depot containing BMP2, upon injection into mice. The hydrogel features and stability of BMP2 inside the hydrogel were significantly affected by the electrostatic attraction between BMP2 and MP-NH₂. Additionally, the time BMP2 spent inside the hydrogel depot was prolonged in vivo, as evidenced by in vivo near-infrared fluorescence imaging. Biocompatibility was demonstrated by the fact that hTMSCs survived in vivo, even after 8 weeks and even though relatively few macrophages were in the hydrogel depot. The osteogenic capacity of the electrostatically loaded hydrogel implants containing BMP2 was higher than that of a hydrogel that was simply loaded with BMP2, as evidenced by Alizarin Red S, von Kossa, and hematoxylin and eosin staining as well as osteonectin, osteopontin, osteocalcin, and type 1α collagen mRNA expression. The results confirmed that our injectable, in situ-forming hydrogel system, electrostatically loaded with BMP2, can enhance in vivo osteogenic differentiation of hTMSCs.

Cell sheet biofabrication by co-administration of mesenchymal stem cells secretome and vitamin C on thermoresponsive polymer

Cell sheet technology aims at replacement of artificial extracellular matrix (ECM) or scaffolds, popular in tissue engineering, with natural cell derived ECM. Adipose tissue mesenchymal stem cells (ASCs) have the ability of ECM secretion and presented promising outcomes in clinical trials. As well, different studies found that secretome of ASCs could be suitable for triggering cell free regeneration induction. The aim of this study was to investigate the effect of using two bio-factors: secretome of ASCs (SE) and vitamin C (VC) for cell sheet engineering on a thermosensitive poly N-isopropyl acryl amide-Methacrylic acid (P(NIPAAm-MAA)) hydrogel. The results revealed that using thermosensitive P(NIPAAm-MAA) copolymer as matrix for cell sheet engineering lead to a rapid ON⁄OFF adhesion/deadhesion system by reducing temperature without enzymatic treatment (complete cell sheet release takes just 6 min). In addition, our study showed the potential of SE for inducing ASCs sheet formation. H&E staining exhibited the properties of a well-formed tissue layer with a dense ECM in sheets prepared by both SE and VC factors, as compared to those of VC or SE alone. Functional synergism of SE and VC exhibited statistically significant enhanced functionality regarding up-regulation of stemness genes expression, reduced β-galactosidase associated senescence, and facilitated sheet release. Additionally, alkaline phosphatase activity (ALP), mineralized deposits and osteoblast matrix around cells confirmed a better performance of ostogenic differentiation of ASCs induced by VC and SE. It was concluded that SE of ASCs and VC could be outstanding biofactors applicable for cell sheet technology.

Effects of new beta-type Ti-40Nb implant materials, brain-derived neurotrophic factor, acetylcholine and nicotine on human mesenchymal stem cells of osteoporotic and non osteoporotic donors

Introduction

Treatment of osteoporotic fractures is still challenging and an urgent need exists for new materials, better adapted to osteoporotic bone by adjusted Young’s modulus, appropriate surface modification and pharmaceuticals.

Materials and methods

Titanium-40-niobium alloys, mechanically ground or additionally etched and titanium-6-aluminium-4-vanadium were analyzed in combination with brain-derived neurotrophic factor, acetylcholine and nicotine to determine their effects on human mesenchymal stem cells in vitro over 21 days using lactate dehydrogenase and alkaline phosphatase assays, live cell imaging and immunofluorescence microscopy.

Results

Cell number of human mesenchymal stem cells of osteoporotic donors was increased after 14 d in presence of ground titanium-40-niobium or titanium-6-aluminium-4-vanadium, together with brain-derived neurotrophic factor. Cell number of human mesenchymal stem cells of non osteoporotic donors increased after 21 d in presence of titanium-6-aluminium-4-vanadium without pharmaceuticals. No significant increase was measured for ground or etched titanium-40-niobium after 21 d. Osteoblast differentiation of osteoporotic donors was significantly higher than in non osteoporotic donors after 21 d in presence of etched, ground titanium-40-niobium or titanium-6-aluminium-4-vanadium accompanied by all pharmaceuticals tested. In presence of all alloys tested brain-derived neurotrophic factor, acetylcholine and nicotine increased differentiation of cells of osteoporotic donors and accelerated it in non osteoporotic donors.

Conclusion

We conclude that ground titanium-40-niobium and brain-derived neurotrophic factor might be most suitable for subsequent in vivo testing.