Tissue Regeneration Capabilities Research Articles

Evaluation of the mechanical properties and degradation behavior of chitosan-PVA-graphene oxide nanocomposite scaffolds in vitro

ObjectivesChitosan (CTS) has been a popular option for scaffold fabrication because of its biocompatibility, biodegradability, antimicrobial and nonimmunogenic effects. However, it is of limited function, due to its low mechanical strength and its solubility in acidified media. These limitations could be overcome by its blending with PVA and incorporation with bioactive materials to improve its mechanical properties and tissue regeneration capability. MethodsCarbon based nanomaterials, such as graphene oxide (GO) incorporated with CTS/PVA blend to improve composite-scaffold stability. GO nanoparticles were chemically prepared and fully characterized. Different concentrations of both CTS and nano-GO were used for the fabrication of CTS/PVA/GO nanocomposite films through the solvent-casting method. The mechanical properties, thermal stability biodegradation, and swelling of the nanocomposite films were evaluated after characterization by XRD, FTIR and SEM, to detect the effect of GO incorporation in the scaffold to select the suitable dental application. ResultsA better performance was observed in thermal stability, biodegradation, and water resistance after GO addition into CTS/PVA scaffolds. Regarding mechanical properties, groups were assessed by Kruskal Wallis test afterward Dunn’s post hoc test. There was no significant difference in tensile strength between the nanocomposite films of CTS (2%) and CTS (3%). The tensile strength decreased after addition of nano-GO at different concentrations. The elastic modulus significantly increased when (1%) GO was added into the 1CTS (2%):1PVA. ConclusionsCTS/PVA/GO nanocomposite can be used in dental hard tissue engineering, as the incorporation of GO into the CTS/PVA polymer blend improves its properties which is regarded as the critical concentrations of CTS and GO.

Graphene Hybrid Tough Hydrogels with Nanostructures for Tissue Regeneration.

Over the past few decades, hydrogels have attracted considerable attention as promising biomedical materials. However, conventional hydrogels require improved mechanical properties, such as brittleness, which significantly limits their widespread use. Recently, hydrogels with remarkably improved toughness have been developed; however, their low biocompatibility must be addressed. In this study, we developed a tough graphene hybrid hydrogel with nanostructures. The resultant hydrogel exhibited remarkable mechanical properties while representing an aligned nanostructure that resembled the extracellular matrix of soft tissue. Owing to the synergistic effect of the topographical properties, and the enhanced biochemical properties, the graphene hybrid hydrogel had excellent stretchability, resilience, toughness, and biocompatibility. Furthermore, the hydrogel displayed outstanding tissue regeneration capabilities (e.g., skin and tendons). Overall, the proposed graphene hybrid tough hydrogel may provide significant insights into the application of tough hydrogels in tissue regeneration.

Dual loaded Ce-MBGs with bioactivity, antioxidant and antibacterial properties

The performance of Bioactive Mesoporous Glasses (MBGs) as tissue regeneration scaffolds can be enhanced by the addition of therapeutic inorganic ions (TIIs) or organic molecules. In order to maximise the benefits conferred by different TIIs and organic molecules on bioactive glasses, we investigated the behavior of a 1:1 mixture (wt.%) of MBGs doped with cerium and loaded separately with gentamicin (Gen) and polyphenols (POLY). The resulting admixed material preserves bioactivity of the unloaded cerium-doped MBGs, assessed by evaluating the formation of an apatitic layer. Furthermore, it shows both antioxidant properties, evaluated by the reduction of Reactive Oxygen Species (ROS) measured by enzymatic assays, conferred by cerium POLY loadings and antibacterial properties conferred by Gen, and estimated by a modification of the Kirby-Bauer agar diffusion method. Ce-MBGs can thus be applied as a useful dual drug delivery system (DDS) with hard tissue regeneration capabilities.

Comprehensive Characterization of Tissues Derived from Animals at Different Regenerative Stages: A Comparative Analysis between Fetal and Adult Mouse Skin.

Tissue regeneration capabilities vary significantly throughout an organism's lifespan. For example, mammals can fully regenerate until they reach specific developmental stages, after which they can only repair the tissue without restoring its original architecture and function. The high regenerative potential of fetal stages has been attributed to various factors, such as stem cells, the immune system, specific growth factors, and the presence of extracellular matrix molecules upon damage. To better understand the local differences between regenerative and reparative tissues, we conducted a comparative analysis of skin derived from mice at regenerative and reparative stages. Our findings show that both types of skin differ in their molecular composition, structure, and functionality. We observed a significant increase in cellular density, nucleic acid content, neutral lipid density, Collagen III, and glycosaminoglycans in regenerative skin compared with reparative skin. Additionally, regenerative skin had significantly higher porosity, metabolic activity, water absorption capacity, and elasticity than reparative skin. Finally, our results also revealed significant differences in lipid distribution, extracellular matrix pore size, and proteoglycans between the two groups. This study provides comprehensive data on the molecular and structural clues that enable full tissue regeneration in fetal stages, which could aid in developing new biomaterials and strategies for tissue engineering and regeneration.

Extracellular Vesicles for Dental Pulp and Periodontal Regeneration

Extracellular vesicles (EVs) are lipid bound particles derived from their original cells, which play critical roles in intercellular communication through their cargoes, including protein, lipids, and nucleic acids. According to their biogenesis and release pathway, EVs can be divided into three categories: apoptotic vesicles (ApoVs), microvesicles (MVs), and small EVs (sEVs). Recently, the role of EVs in oral disease has received close attention. In this review, the main characteristics of EVs are described, including their classification, biogenesis, biomarkers, and components. Moreover, the therapeutic mechanism of EVs in tissue regeneration is discussed. We further summarize the current status of EVs in pulp/periodontal tissue regeneration and discuss the potential mechanisms. The therapeutic potential of EVs in pulp and periodontal regeneration might involve the promotion of tissue regeneration and immunomodulatory capabilities. Furthermore, we highlight the current challenges in the translational use of EVs. This review would provide valuable insights into the potential therapeutic strategies of EVs in dental pulp and periodontal regeneration.

The Role of Extracellular Vesicles in Optic Nerve Injury: Neuroprotection and Mitochondrial Homeostasis.

Stem cell therapies hold great promise as alternative treatments for incurable optic nerve disorders. Although mesenchymal stem cells exhibit various tissue regeneration and recovery capabilities that may serve as valuable therapies, the clinical applications remain limited. Thus, we investigated the utility of extracellular vesicles (EVs) from human placenta-derived mesenchymal stem cells (hPSCs) in this context. Hypoxically preconditioned hPSCs (HPPSCs) were prepared via short-term incubation under 2.2% O2 and 5.5% CO2. The EVs were then isolated. R28 cells (retinal precursor cells) were exposed to CoCl2 and treated with EVs for 24 h. Cell proliferation and regeneration were measured using a BrdU assay and immunoblotting; ATP quantification revealed the extent of the mitochondrial function. The proteome was determined via liquid chromatography-tandem mass spectroscopy. Differentially expressed proteins (DEPs) were detected and their interactions identified. HPPSC_EVs functions were explored using animal models of optic nerve compression. HPPSC_EVs restored cell proliferation and mitochondrial quality control in R28 cells damaged by CoCl2. We identified DEPs (p < 0.05) that aided recovery. The mitochondrial DEPs included LONP1; PARK7; VDAC1, 2, and 3; HSPD1; and HSPA9. EVs regulated the levels of mitophagic proteins in R28 cells injured by hypoxia; the protein levels did not increase in LONP1 knockdown cells. LONP1 is a key mediator of the mitophagy that restores mitochondrial function after hypoxia-induced optic nerve injury.

Scaffolds with anisotropic structure for neural tissue engineering

Nervous system injuries remain a great challenge due to limited natural tissue regeneration capabilities. Neural tissue engineering has been regarded as a promising approach for repairing nerve defects, which utilizes external biomaterial scaffolds to allow cells to migrate to the injury site and repair the tissue. Particularly, scaffolds with anisotropic structures biomimicking the native extracellular matrix (ECM) can effectively guide neural orientation and reconnection. Here, the advancements of scaffolds with anisotropic structures in the field of neural tissue engineering are presented. The fabrication strategies of scaffolds with anisotropic structures and their effects in vitro and in vivo are highlighted. We also discuss the challenges and provide a perspective of this field.

Sodium alginate-f-GO composite hydrogels for tissue regeneration and antitumor applications

Biopolymer-based composite hydrogels have attracted tremendous attention for tissue regeneration and antitumor applications. Since sodium alginate is a biopolymer, they offer excellent therapeutic options with long-term drug release and low side effects. To prepare multifunctional composite hydrogels with anticancer and tissue regeneration capabilities, sodium alginate (SA) and graphene oxide (GO) were covalently linked and crosslinked with tetraethyl orthosilicate (TEOS) by the solvothermal method. The structural and morphological results show that the hydrogels exhibit the desired functionality and porosity. The swelling of hydrogels in an aqueous and PBS medium was investigated. SGT-4 had the highest swelling in both aqueous and PBS media. Swelling and biodegradation of the hydrogel were inversely related. The drug release of SGT-4 was determined in different pH media (pH 6.4, 7.4, and 8.4) and the kinetics of drug release was determined according to the Higuchi model (R2 = 0.93587). Antibacterial activities were evaluated against severe infectious agents. Uppsala (U87) and osteoblast (MC3T3-E1) cell lines were used to determine the anticancer and biocompatibility of the composite hydrogels, respectively. These results suggest that the composite hydrogels could be used as potential biomaterials for tissue regeneration and antitumor applications.

Multifunctional Photoactive Hydrogels for Wound Healing Acceleration.

Light is an attractive tool that has a profound impact on modern medicine. Particularly, light-based photothermal therapy (PTT) and photodynamic therapy (PDT) show great application prospects in the prevention of wound infection and promoting wound healing. In addition, hydrogels have shown attractive advantages in the field of wound dressings due to their excellent biochemical effects. Therefore, multifunctional photoresponsive hydrogels (MPRHs) that integrate the advantages of light and hydrogels are increasingly used in biomedicine, especially in the field of wound repair. However, a comprehensive review of MPRHs for wound regeneration is still lacking. This review first focuses on various types of MPRHs prepared by diverse photosensitizers, photothermal agents (PHTAs) including transition metal sulfide/oxides nanomaterials, metal nanostructure-based PHTAs, carbon-based PHTAs, conjugated polymer or complex-based PHTAs, and/or photodynamic agents (PHDAs) such as ZnO-based, black-phosphorus-based, TiO2-based, and small organic molecule-based PHDAs. We also then discuss how PTT, PDT, and photothermal/photodynamic synergistic therapy can modulate the microenvironments of bacteria to inhibit infection. Overall, multifunctional hydrogels with both therapeutic and tissue regeneration capabilities have been discussed and existing challenges, as well as future research directions in the field of MPRHs and their application in wound management are argued.

Bone Tissue Regeneration by Collagen Scaffolds with Different Calcium Phosphate Coatings: Amorphous Calcium Phosphate and Low-Crystalline Apatite.

Surface-mineralized collagen sponges have attracted much attention as scaffolds for bone tissue engineering. Recently, we developed amorphous calcium phosphate (ACP) and low-crystalline apatite coating processes on collagen sponges. In the present study, we applied these coating processes to granular collagen sponges (referred to as Col) to compare the bone tissue regeneration capabilities of ACP-coated and apatite-coated Col (referred to as Col-ACP and Col-Ap, respectively) using a rat cranial bone defect model. According to micro-CT and histological analyses, Col-Ap enhanced bone tissue regeneration compared to Col, whereas Col-ACP did not. These results not only demonstrated the superior bone tissue regeneration capability of Col-Ap, but also indicated limitations of the in vitro simulated body fluid (SBF) test used in our previous study. Despite the apatite-forming ability of Col-ACP in SBF, it was ineffective in improving bone tissue regeneration in vivo, unlike Col-Ap, most likely due to the quick resorption of the ACP coating in the defect site. The present results clarified the importance of the coating stability in vivo and revealed that the low-crystalline apatite coating was more beneficial than the ACP coating in the fabrication of surface-mineralized collagen sponges for use as bone tissue engineering scaffolds.

Immunomodulatory extracellular vesicles: an alternative to cell therapy for COVID-19

ABSTRACT Introduction: SARS-CoV-2 induces a cytokine storm and can cause inflammation, fibrosis and apoptosis in the lungs, leading to acute respiratory distress syndrome (ARDS). ARDS is the leading cause of mortality and morbidity the associated to COVID-19, and the cytokine storm is a prominent etiological factor. Mesenchymal stem cell-derived extracellular vesicles are an alternative therapy for the management of inflammatory and autoimmune conditions due to their immunosuppressive properties. The immunomodulatory and tissue regeneration capabilities of extracellular vesicles may support their application as a prospective therapy for COVID-19. Areas Covered: We explored the clinical evidence on extracellular vesicles as antiviral agents and in mitigating ARDS, and their therapeutic potential in COVID-19. Expert Opinion: Clinical trials using extracellular vesicles are registered against COVID-19 associated complications, with some evidence of safety and efficacy. Extracellular vesicles present an alternative potential for cell therapy for COVID-19 management, but further preclinical and clinical investigations are needed.

Concerns About Mesenchymal Stem Cell Therapy

Dear Editor, Multipotent mesenchymal stromal cells (MSCs), because of their potential for treating diseases, have gained considerable attention over the past 30 years for their immunosuppressive properties and tissue regeneration capabilities.1,2 This grew into an interest in the 1970s by Friedenstein and contemporaries after studying the bone m ar row.3 MSCs are an excellent candidate for cell therapy because of having intrinsic differentiation potentials into bone, cartilage and fat cells not found previously in other cells. They can also be isolated and expanded easily in vitro, and produce abundant useful growth factors and cytokines.2,4Mesenchymal stem cells have become the top used stem cell type for clinical application with encouraging results.5,6 Significant progress has been made in stem cell research in recent years. The main therapeutic effects of MSCs are now attributed to the stimulation of several innate repair processes in injured tissues in vivo by secreted factors as well as the immunomodulation response. Therefore, MSC therapy is expected to find clinical application in human diseases.6,7 However, there are some critical issues that need to be addressed before MSCs can be used for clinical therapy in humans which will help determine the efficiency of cells administered to the patients as a therapeutic approach, most important of which is immunosuppressive properties.8,9 MSCs can be affected by tumor support that may affect potential tumorigenesis after MSCs transplantation, including different donors and tissues, inconsistent protocols, varying dosages and differing transfusion patterns, and mechanisms that control the behavior of the MSCs at the target site.10,11 Because of their unique features, stem cells are undoubtedly a great hope for the treatment of many diseases. More research is developing on the potential long-term risks associated with MSC therapy. However, Additional studies would also be a major contribution to stem cell biology in general as well as their transplantation.

Methods for the Assembly and Characterization of Polyelectrolyte Multilayers as Microenvironments to Modulate Human Mesenchymal Stromal Cell Response.

Thin films are of interest in materials design because they allow for the modification of surface properties of materials while the bulk properties of the material are largely unaffected. In this work, we outline methods for the assembly of thin films using a technique known as layer-by-layer (LbL). Furthermore, their interactions with human mesenchymal stromal cells (hMSCs) are discussed. hMSCs are a subject of growing interest because of their potential to treat or cure diseases, given their immunosuppressive properties, multipotent differentiation capabilities, and tissue regeneration capabilities. Numerous improvements and modifications have been suggested for the harvesting, treatment, and culture of hMSCs prior to their administration in human subjects. Here, we discuss methods to assess the interactions of hMSCs with thin LbL-assembled films of heparin and collagen. Three different methods are discussed. The first details the preparation of heparin/collagen multilayers on different surfaces and the seeding of cells on these multilayers. The second method details the characterization of multilayers, including techniques to assess the thickness, roughness, and surface charge of the multilayers, as well as in situ deposition of multilayers. The third method details the analysis of cell interactions with the multilayers, including techniques to assess proliferation, viability, real-time monitoring of hMSC behavior, analysis of hMSC-adhesive proteins on the multilayers, immunomodulatory factor expression of hMSCs, and cytokine expression on heparin/collagen multilayers. We propose that the methods described in this work will assist in the design and characterization of LbL-assembled thin films and the analysis of hMSCs cultured on these thin films.

UBA2 activates Wnt/\u03b2-catenin signaling pathway during protection of R28 retinal precursor cells from hypoxia by extracellular vesicles derived from placental mesenchymal stem cells

BackgroundStem cell transplantation has been proposed as an alternative treatment for intractable optic nerve disorders characterized by irrecoverable loss of cells. Mesenchymal stem cells, with varying tissue regeneration and recovery capabilities, are being considered for potential cell therapies. To overcome the limitations of cell therapy, we isolated exosomes from human placenta-derived mesenchymal stem cells (hPMSCs) and investigated their therapeutic effects in R28 cells (retinal precursor cells) exposed to CoCl2.MethodAfter 9 h of exposure to CoCl2, the hypoxic damaged R28 cells were divided into the non-treatment group (CoCl2 + R28 cells) and treatment group (CoCl2 + R28 cells treated with exosome). Immunoblot analysis was performed for Pcna, Hif-1α, Vegf, Vimentin, Thy-1, Gap43, Ermn, Neuroflament, Wnt3a, β-catenin, phospo-GSK3β, Lef-1, UBA2, Skp1, βTrcp, and ubiquitin. The proteomes of each group were analyzed by liquid chromatography/tandem mass (LC-MS/MS) spectrometry. Differentially expressed proteins (DEPs) were detected by label-free quantification, and the interactions of the proteins were examined through signal transduction pathway and gene ontology analysis.ResultWe observed that exosome could significantly recover proliferation damaged by CoCl2 treatment. In addition, the treatment group presented the decreased expression of Hif-1α protein (P < 0.05) and increased expression of proliferation marker, Pcna, and nerve regeneration-related factors such as Vimentin, Thy-1, and Neuroflament (P < 0.05) compared with the non-treatment group. In total, 200 DEPs were identified in the non-treatment group and treatment group (fold change ≥ 2, p < 0.05). Catenin and ubiquitin systems (UBA2, UBE2E3, UBE2I) were found in both the DEP lists of downregulated proteins from the non-treatment group and upregulated proteins from the treatment group. The mRNA expressions of ubiquitin systems were significantly decreased under hypoxic conditions. Moreover, UBA2 and Wnt/β-catenin protein were associated with the rescue of the hypoxic damaged R28 cells. Using a siRNA system, we could find it out that hPMSC exosomes could not repair altered expressions of target proteins by CoCl2 in lacking UBA2 R28 cells.ConclusionThis study reported that hypoxic damaged expression of regeneration markers in R28 cells was significantly recovered by hPMSC exosomes. We could also demonstrate that UBA2 played a key role in activating the Wnt/β-catenin signaling pathway during protection of hypoxic damaged R28 cells, induced by hPMSC exosomes.

Carbon quantum dots-embedded electrospun antimicrobial and fluorescent scaffold for reepithelialization in albino wistar rats.

A prosthetic scaffold development using fluorescent nanofiber is reported for an enhanced reepithelialization in wistar albino rats. In this study, a novel approach was followed to construct the biocompatible fluorescent nanofiber that will be helpful to monitor the tissue regeneration process. Here, a multifunctional carbon quantum dots (CQDs)-embedded electrospun polyacrylonitrile (PAN) nanofiber was fabricated and characterized using standard laboratory techniques. The biodegradation ability was assessed by simulated body fluid thereby analyzing porosity and water absorption capacity of the material. The fluorescent scaffold was tested for cytotoxicity and antimicrobial activity using bacterial and fibroblast cells and fluorescent stability was analyzed by bioimaging of animal and bacterial cells. Tissue regeneration capability of the developed scaffold was evaluated using wistar albino rats. Unlike biomicking scaffolds, the CQDs-embedded PAN-based substrate has given dual support by enhancing reepithelialization without growth factors and acted as an antimicrobial agent to provide contamination free tissue regeneration. Scaffolds were examined by using histostaining techniques and scanning electron microscopy to observe the reepithelialization in the regenerated tissues. The novel approach for developing infection free soft tissue regeneration was found to be phenomenal in scaffold development.

Stem cell and tissue regeneration analysis in low-dose irradiated planarians treated with cerium oxide nanoparticles.

Owing to the self-renewing reactive oxygen species scavenger capability of cerium oxide nanoparticles (nanoceria), we tested in vivo radioprotective effects on stem cells and tissue regeneration using low-dose irradiated planarians as model system. We treated planarians with nanoceria or gum Arabic, as control, and we analyzed the expression of stem cell molecular markers and tissue regeneration capability, as well as cell death and DNA damage in non-irradiated and in low-dose irradiated animals. Our findings show that nanoceria increase the number of stem cells and tissue regenerative capability, and reduce cell death and DNA damage after low-dose irradiation, suggesting a protective role on stem cells.

Evaluation of the therapeutic potential of mesenchymal stromal cells during in vitro production: search for markers related to immunomodulatory properties

Background & Aim Mesenchymal stromal/stem cells (MSCs) are a heterogeneous population characterized by self-renewing and ability to differentiate into mesodermal cell origin. Wharton Jelly MSC (WJ-MSC) are a promising candidate for cell therapy due to their ease of isolation and their tissue regeneration capabilities. Moreover, they can regulate the immune response by secreting a set of soluble factors and by establishing direct interactions with the cells of immune system. These immunomodulation properties are used in the treatment of different pathologies such as graft versus host disease. In order to use WJ-MSCs for clinical applications, an in vitro expansion step is critical to obtain the sufficient dose. This step imposes several physicochemical and hydrodynamic constraints that can influence the quality and functional properties of cells. The objective of this work was to identify and validate predictive markers related to immunomodulatory properties of WJ-MSCs. For this purpose, CD119, CD200 and Notch1 were chosen and studied. Methods, Results & Conclusion At first, markers distribution was studied by flow cytometry. Secondly, immunomodulatory potential of WJ-MSC was evaluated by a coculture of these cells with CD4, CD8 lymphocytes, followed by the study of lymphocytes proliferation by flow cytometry. These experimentss were performed under different conditions: WJ-MSCs cultivated in normoxia (N) and hypoxia (H), early passage and senescent cells, and under stimulation with gamma interferon (IFN-γ). Our results showed a heterogeneity of distribution of the markers studied. In addition, our study revealed that WJ-MSC cultivated in H was more immunosuppressive than those cultivated in N. Moreover, we showed that the cellular senescence induced a reduction of the immunosuppressive properties, and that IFN-γ stimulation increased WJ-MSC immunosuppression potential. Finally, our study highlighted a trend towards a correlation between the expression of CD119 and Notch1 by WJ-CSM and their immunomodulatory properties. To conclude, the culture conditions and cell senescence affect the immunomodulatory properties of WJ-CSM hence the interest of verifying these properties after the cell expansion procedures. Furthermore CD119 and Notch1 receptors may be predictive markers of the immunomodulatory properties of WJ -CSM to be checked during in vitro amplification.

Polymer-Assisted In Situ Synthesis of Silver Nanoparticles with Epigallocatechin Gallate (EGCG) Impregnated Wound Patch Potentiate Controlled Inflammatory Responses for Brisk Wound Healing.

IntroductionAn ideal wound dressing material needs to be predisposed with desirable attributes like anti-infective effect, skin hydration balance, adequate porosity and elasticity, high mechanical strength, low wound surface adherence, and enhanced tissue regeneration capability. In this work, we have synthesized hydrogel-based wound patches having antibacterial silver nanoparticles and antioxidant epigallocatechin gallate (EGCG) and showed fast wound closure through their synergistic interaction without any inherent toxicity.Methods and resultsWound patches were synthesized from modified guar gum polymer and assessed to determine accelerated wound healing. The modified polymer beget chemical-free in-situ synthesis of monodispersed silver NPs (~12 nm), an antimicrobial agent, besides lending ionic surface charges. EGCG impregnated during ionotropic gelation process amplified the efficacy of wound patches that possess apt tensile strength, porosity, and swellability for absorbing wound exudates. Further, in vitro studies endorsed them as non-cytotoxic and the post agent effect following exposure to the patch showed an unbiased response to E coli K12 and B. subtilis. In vivo study using sub-cutaneous wounds in Wistar rats validated its accelerated healing properties when compared to a commercially available wound dressing material (skin graft; Neuskin-F®) through better wound contraction, promoted collagen deposition and enhanced vascularization of wound region by modulating growth factors and inflammatory cytokines.ConclusionSynthesized wound patches showed all the desired attributes of a clinically effective dressing material and the results were validated in various in vitro and in vivo assays.

Effects of Physical, Chemical, and Biological Stimulus on h-MSC Expansion and Their Functional Characteristics.

Human adult mesenchymal stem or stromal cells (h-MSC) therapy has gained considerable attention due to the potential to treat or cure diseases given their immunosuppressive properties and tissue regeneration capabilities. Researchers have explored diverse strategies to promote high h-MSC production without losing functional characteristics or properties. Physical stimulus including stiffness, geometry, and topography, chemical stimulus, like varying the surface chemistry, and biochemical stimuli such as cytokines, hormones, small molecules, and herbal extracts have been studied but have yet to be translated to industrial manufacturing practice. In this review, we describe the role of those stimuli on h-MSC manufacturing, and how these stimuli positively promote h-MSC properties, impacting the cell manufacturing field for cell-based therapies. In addition, we discuss other process considerations such as bioreactor design, good manufacturing practice, and the importance of the cell donor and ethics factors for manufacturing potent h-MSC.

3D-printed nanocomposite scaffolds with tunable magnesium ionic microenvironment induce in situ bone tissue regeneration

Local tissue microenvironment is able to regulate cell-to-cell interaction that leads to effective tissue repair. This study aims to demonstrate a tunable magnesium ionic (Mg2+) microenvironment in bony tissue that can significantly induce bone defect repair. The concept can be realized by using a newly fabricated nanocomposite comprising of custom-made copolymer polycaprolactone-co-poly(ethylene glycol)-co-polycaprolactone (PCL-PEG-PCL) and surface-modified magnesium oxide (MgO) nanoparticles. In this study, additive manufacturing (AM) technology had been adopted to help design the porous three-dimensional (3D) scaffolds with tunable Mg2+ microenvironment. We found that the wettability and printability of new copolymer had been improved as compared with that of PCL polymer. Additionally, when MgO nanoparticles incorporated into the newly synthesized hydrophilic copolymer matrix, it could lead to increased compressive moduli significantly. In the in vitro studies, the fabricated nanocomposite scaffold with low concentration of Mg2+ microenvironment not only demonstrated better cytocompatibility, but also remarkably enhanced osteogenic differentiation in vitro as compared with the pure PCL and PCL-PEG-PCL co-polymer controls. In the animal studies, we also found that superior and early bone formation and tissue mineralization could be observed in the same 3D printed scaffold. However, the nanocomposite scaffold with high concentration of Mg2+ jeopardized the in situ bony tissue regeneration capability due to excessive magnesium ions in bone tissue microenvironment. Lastly, this study demonstrates that the nanocomposite 3D scaffold with controlled magnesium concentration in bone tissue microenvironment can effectively promote bone defect repair.