Tissue Repair Applications Research Articles

Investigating the use of curcumin-loaded electrospun filaments for soft tissue repair applications.

Electrospun filaments represent a new generation of medical textiles with promising applications in soft tissue repair. A potential strategy to improve their design is to combine them with bioactive molecules. Curcumin, a natural compound found in turmeric, is particularly attractive for its antioxidant, anti-inflammatory, and antimicrobial properties. However, investigating the range of relevant doses of curcumin in materials designed for tissue regeneration has remained limited. In this paper, a wide range of curcumin concentrations was explored and the potential of the resulting materials for soft tissue repair applications was assessed. Polydioxanone (PDO) filaments were prepared with various amounts of curcumin: 0%, 0.001%, 0.01%, 0.1%, 1%, and 10% (weight to weight ratio). The results from the present study showed that, at low doses (≤0.1%), the addition of curcumin has no influence on the spinning process or on the physicochemical properties of the filaments, whereas higher doses lead to smaller fiber diameters and improved mechanical properties. Moreover, filaments with 0.001% and 0.01% curcumin stimulate the metabolic activity and proliferation of normal human dermal fibroblasts (NHDFs) compared with the no-filament control. However, this stimulation is not significant when compared to the control filaments (0%). Highly dosed filaments induce either the inhibition of proliferation (with 1%) or cell apoptosis (with 10%) as a result of the concentrations of curcumin found in the medium (9 and 32 μM, respectively), which are near or above the known toxicity threshold of curcumin (~10 μM). Moreover, filaments with 10% curcumin increase the catalase activity and glutathione content in NHDFs, indicating an increased production of reactive oxygen species resulting from the large concentration of curcumin. Overall, this study suggested that PDO electrospun filaments loaded with low amounts of curcumin are more promising compared with higher concentrations for stimulating tissue repair. This study also highlighted the need to explore lower concentrations when using polymers as PDO, such as those with polycaprolactone and other degradable polyesters.

Wound Healing: Silk Fibroin Biomaterial Shows Safe and Effective Wound Healing in Animal Models and a Randomized Controlled Clinical Trial (Adv. Healthcare Mater. 10/2017)

Silk fibroin is a natural protein derived from Bombyx mori cocoons, and shows potential in tissue repair applications due to its excellent biomedical properties. The silk fibroin film, developed by Xiaohui Zou, Hongwei Ouyang, and co-workers from Zhejiang University in article number 1700121, is a highly transparent, biocompatible, air-permeable, waterproof and bacteria barrier scaffold. It significantly reduces the time to wound healing and incidence of adverse events compared to commercial dressing.

Engineered 3D-scaffolds of photocrosslinked chitosan-gelatin hydrogel hybrids for chronic wound dressings and regeneration

Wound repair is one of the most complex biological processes in human life. To date, no ideal biomaterial solution has been identified, which that encompasses all functions and properties of real skin tissue. Thus, this study focused on the synthesis of new biocompatible hybrid hydrogel scaffolds based on methacrylate-functionalized high molecular mass chitosan with gelatin-A photocrosslinked with UV radiation to tailor matrix network properties. These hybrid hydrogels were produced via freeze-drying and were extensively characterized by swelling and degradation measurements, Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–Vis), scanning electron microscopy (SEM-EDS), and micro-computed tomography (micro-CT). The results demonstrated that hydrogels were produced with broadly designed swelling degrees typically ranging from 500% to 2000%, which were significantly dependent on the relative concentration of polymers and irradiation time for crosslinking. Analogously, degradation was reduced with increased photocrosslinking of the network. Moreover, insights into the mechanism of photochemical crosslinking were suggested based on FTIR and UV–Vis analyses of the characteristic functional groups involved in the reactions. SEM analysis associated with micro-CT imaging of the hybrid scaffolds showed uniformly interconnected 3D porous structures, with architectural features affected by the crosslinking of the network. These hydrogels were biocompatible, with live cell viability responses of human embryonic kidney (HEK293T) cells being above 95%. Hence, novel hybrid hydrogels were designed and produced with tunable properties through photocrosslinking and with a biocompatible response suitable for use in wound dressing and skin tissue repair applications.

Silk Fibroin Biomaterial Shows Safe and Effective Wound Healing in Animal Models and a Randomized Controlled Clinical Trial.

Due to its excellent biological and mechanical properties, silk fibroin has been intensively explored for tissue engineering and regenerative medicine applications. However, lack of translational evidence has hampered its clinical application for tissue repair. Here a silk fibroin film is developed and its translational potential is investigated for skin repair by performing comprehensive preclinical and clinical studies to fully evaluate its safety and effectiveness. The silk fibroin film fabricated using all green chemistry approaches demonstrates remarkable characteristics, including transmittance, fluid handling capacity, moisture vapor permeability, waterproofness, bacterial barrier properties, and biocompatibility. In vivo rabbit full-thickness skin defect study shows that the silk fibroin film effectively reduces the average wound healing time with better skin regeneration compared with the commercial wound dressings. Subsequent assessment in porcine model confirms its long-term safety and effectiveness for full-thickness skin defects. Finally, a randomized single-blind parallel controlled clinical trial with 71 patients shows that the silk fibroin film significantly reduces the time to wound healing and incidence of adverse events compared to commercial dressing. Therefore, the study provides systematic preclinical and clinical evidence that the silk fibroin film promotes wound healing thereby establishing a foundation towards its application for skin repair and regeneration in the clinic.

Bioactive glasses in wound healing: hope or hype?

Bioactive glasses have long been investigated in mineralized tissue regeneration, but recently their potential applications in soft tissue repair, and in particular wound healing, have demonstrated great promise. Commonly used glasses, such as the silicate-based Bioglass® 45S5 [(46.1)SiO2-(26.9)CaO-(24.4)Na2O-(2.6)P2O5 (mol%)] and borate-based 13-93B3 [(54)B2O3-(22)CaO-(6)Na2O-(8)K2O-(8)MgO-(2)P2O5 (mol%)] have been implicated in the stages of wound healing due to their ability to release ions that can stimulate processes, such as haemostasis, antibacterial efficacy, epithelial cell migration, angiogenesis, and fibroblastic cell proliferation, amongst others. More recently, a wound dressing composed of a borate-based glass received regulatory approval for use in the treatment of acute and chronic wounds. However, to date, there are no comprehensive reports on their specific mechanism of action in accelerating the wound healing processes. In this highlight, we will provide a brief overview of the wound healing stages, review the bioactive glass formulations that have been investigated for potential applications in wound healing and attempt to summarize the consensus on why these glasses may be successful in wound healing.

MicroRNA-21 preserves the fibrotic mechanical memory of mesenchymal stem cells.

Expansion on stiff culture substrates activates pro-fibrotic cell programs that are retained by mechanical memory. Here, we show that priming on physiologically soft silicone substrates suppresses fibrogenesis and desensitizes mesenchymal stem cells (MSCs) against subsequent mechanical activation in vitro and in vivo, and identify the microRNA miR-21 as a long-term memory keeper of the fibrogenic program in MSCs. During stiff priming, miR-21 levels were gradually increased by continued regulation through the acutely mechanosensitive myocardin-related transcription factor-A (MRTF-A/MLK-1) and remained high over 2 weeks after removal of the mechanical stimulus. Knocking down miR-21 once by the end of the stiff-priming period was sufficient to erase the mechanical memory and sensitize MSCs to subsequent exposure to soft substrates. Soft priming and erasing mechanical memory following cell culture expansion protects MSCs from fibrogenesis in the host wound environment and increases the chances for success of MSC therapy in tissue-repair applications.

Development of dopant-free conductive bioelastomers.

Conductive biodegradable materials are of great interest for various biomedical applications, such as tissue repair and bioelectronics. They generally consist of multiple components, including biodegradable polymer/non-degradable conductive polymer/dopant, biodegradable conductive polymer/dopant or biodegradable polymer/non-degradable inorganic additives. The dopants or additives induce material instability that can be complex and possibly toxic. Material softness and elasticity are also highly expected for soft tissue repair and soft electronics. To address these concerns, we designed a unicomponent dopant-free conductive polyurethane elastomer (DCPU) by chemically linking biodegradable segments, conductive segments, and dopant molecules into one polymer chain. The DCPU films which had robust mechanical properties with high elasticity and conductivity can be degraded enzymatically and by hydrolysis. It exhibited great electrical stability in physiological environment with charge. Mouse 3T3 fibroblasts survived and proliferated on these films exhibiting good cytocompatibility. Polymer degradation products were non-toxic. DCPU could also be processed into a porous scaffold and in an in vivo subcutaneous implantation model, exhibited good tissue compatibility with extensive cell infiltration over 2 weeks. Such biodegradable DCPU with good flexibility and elasticity, processability, and electrical stability may find broad applications for tissue repair and soft/stretchable/wearable bioelectronics.

Solubilized extracellular matrix bioscaffolds derived from diverse source tissues differentially influence macrophage phenotype.

The host response to biomaterials is a critical determinant of their success or failure in tissue-repair applications. Macrophages are among the first responders in the host response to biomaterials and have been shown to be predictors of downstream tissue remodeling events. Biomaterials composed of mammalian extracellular matrix (ECM) in particular have been shown to promote distinctive and constructive remodeling outcomes when compared to their synthetic counterparts, a property that has been largely attributed to their ability to modulate the host macrophage response. ECM bioscaffolds are prepared by decellularizing source tissues such as dermis and small intestinal submucosa. The differential ability of such scaffolds to influence macrophage behavior has not been determined. The present study determines the effects of ECM bioscaffolds derived from eight different source tissues upon macrophage surface marker expression, protein content, phagocytic capability, metabolism, and antimicrobial activity. The results show that macrophages exposed to small intestinal submucosa (SIS), urinary bladder matrix (UBM), brain ECM (bECM), esophageal ECM (eECM), and colonic ECM (coECM) express a predominant M2-like macrophage phenotype, which is pro-remodeling and anti-inflammatory (iNOS-/Fizz1+/CD206+). In contrast, macrophage exposure to dermal ECM resulted in a predominant M1-like, pro-inflammatory phenotype (iNOS+/Fizz1-/CD206-), whereas liver ECM (LECM) and skeletal muscle ECM (mECM) did not significantly change the expression of these markers. All solubilized ECM bioscaffold treatments resulted in an increased macrophage antimicrobial activity, but no differences were evident in macrophage phagocytic capabilities, and macrophage metabolism was decreased following exposure to UBM, bECM, mECM, coECM, and dECM. The present work could have important implications when considering the macrophage response following ECM implantation for site-appropriate tissue remodeling. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 138-147, 2017.

A novel clay-based nanocomposite hydrogel with attractive mechanical properties and its application for bone tissue repair

A novel clay-based nanocomposite hydrogel with attractive mechanical properties and its application for bone tissue repair

Fabrication and characterization of polycaprolactone and tricalcium phosphate composites for tissue engineering applications

Background/purposeβ-Tricalcium phosphate (β-TCP) is an osteoconductive material which has been used for clinical purposes for several years, as is polycaprolactone (PCL), which has already been approved for a number of medical and drug delivery devices. In this study we have incorporated various concentrations of β-TCP into PCL with the aim of developing an injectable, mechanically strong, and biodegradable material which can be used for medical purposes without organic solvents. Materials and methodsThis study assesses the physical and chemical properties of this material, evaluates the in vitro bioactivity of the PCL/β-TCP composites, and analyzes cell proliferation and osteogenic differentiation when using human bone marrow mesenchymal stem cells (hBMSCs). ResultsThe results show that weight losses of approximately 5.3%, 12.1%, 18.6%, and 25.2%, were observed for the TCP0, TCP10, TCP30, and TCP50 composites after immersion in simulated body fluid for 12 weeks, respectively, indicating significant differences (P < 0.05). In addition, PCL/β-TCP composites tend to have lower contact angles (47 ± 1.5° and 58 ± 1.7° for TCP50 and TCP30, respectively) than pure PCL (85 ± 1.3°), which are generally more hydrophilic. After 7 days, a significant (22% and 34%, respectively) increase (P < 0.05) in alkaline phosphatase level was measured for TCP30 and TCP50 in comparison with the pure PCL. ConclusionPCL/TCP is biocompatible with hBMSCs. It not only promotes proliferation of hBMSCs but also helps to differentiate reparative hard tissue. We suggest 50% (weight) PCL-containing β-TCP biocomposites as the best choice for hard tissue repair applications.

Bioadaptability: An Innovative Concept for Biomaterials

Biocompatibility is the basic requirement of biomaterials for tissue repair. However, the present concept of biocompatibility has a certain limitation in explaining the phenomena involved in biomaterial-based tissue repair. New materials, in particular those for tissue engineering and regeneration, have been developed with common characteristics, i.e. they participate deeply into important chemical and biological processes in the human body and the interaction between the biomaterials and tissues is far more complex. Understanding the interplay between these biomaterials and tissues is vital for their development and functionalization. Herein, we suggest the concept of bioadaptability of biomaterials. This concept describes the three most important aspects that can determine the performance of biomaterials in tissue repair: 1) the adaptability of the micro-environment created by biomaterials to the native micro-environment in situ; 2) the adaptability of the mechanical properties of biomaterials to the native tissue; 3) the adaptability of the degradation properties of biomaterials to the new tissue formation. The concept of bioadaptability emphasizes both the material's characteristics and biological aspects within a certain micro-environment and molecular mechanism. It may provide new inspiration to uncover the interaction mechanism of biomaterials and tissues, to foster the new ideas of functionalization of biomaterials and to investigate the fundamental issues during the tissue repair process by biomaterials. Furthermore, designing biomaterials with such bioadaptability would open a new door for repairing and regenerating organs or tissues. In this review, we summarized the works in recent years on the bioadaptability of biomaterials for tissue repair applications.

Self-Assembled Tetrahedral DNA Nanostructures Promote Adipose-Derived Stem Cell Migration via lncRNA XLOC 010623 and RHOA/ROCK2 Signal Pathway.

Self-assembled tetrahedral DNA nanostructures (TDNs) with precise sizes have been extensively applied in various fields owing to their exceptional mechanical rigidity, structural stability, and modification versatility. In addition, TDNs can be internalized by mammalian cells and remain mainly intact within the cytoplasm by escaping degradation by nucleases. Here, we studied the effects of TDNs on cell migration and the underlying molecular mechanisms. TDNs remarkably enhanced the migration of rat adipose-derived stem cells and down-regulated the long noncoding RNA (lncRNA) XLOC 010623 to activate the mRNA expression of Tiam1 and Rac1. Furthermore, TDNs highly up-regulated the mRNA and protein expression of RHOA, ROCK2, and VCL. These results indicate that TDNs suppressed the transcription of lncRNA XLOC 010623 and activated the TIAM1/RAC1 and RHOA/ROCK2 signaling pathways to promote cell migration. On the basis of these findings, TDNs show a high potential for application in tissue repair and regenerative medicine as a functional three-dimensional DNA nanomaterial.

Bioactive SiO2-CaO-P2O5 hollow nanospheres for drug delivery

Hollow nanospherical bioactive glasses have attracted much interest in the recent years because of their important applications in drug delivery and hard tissue repair. Herein, we developed a facile method to fabricate bioactive SiO2-CaO-P2O5 (SCP) hollow nanospheres using polystyrene (PS) nanospheres as the hard template. The removal of PS templates by heating produced almost monodispersed hollow SCP nanospheres with an inner cavity of 210nm, making them suitable for drug delivery. The impact of the glass composition on the formation of hollow SCP nanospheres was investigated in detail. High drug-loading capacity and sustained multistep release of theophylline in the SCP nanospheres were achieved. Furthermore, the SCP nanospheres exhibited apatite-forming ability when immersed in a simulated body fluid. Cytotoxicity of SCP nanospheres on live cells has been evaluated. The SCP hollow nanospheres with sustained drug release property and bioactivity are promising new-generation biomaterials.

Increased Survival and Function of Mesenchymal Stem Cell Spheroids Entrapped in Instructive Alginate Hydrogels.

Mesenchymal stem cell (MSC)-based therapies are under broad investigation for applications in tissue repair but suffer from poor cell persistence and engraftment upon transplantation. MSC spheroids exhibit improved survival, anti-inflammatory, and angiogenic potential in vitro, while also promoting vascularization when implanted in vivo. However, these benefits are lost once cells engage the tissue extracellular matrix and migrate from the aggregate. The efficacy of cell therapy is consistently improved when using engineered materials, motivating the need to investigate the role of biomaterials to instruct spheroid function. In order to assess the contribution of adhesivity on spheroid activity in engineered materials and promote the bone-forming potential of MSCs, we compared the function of MSC spheroids when entrapped in Arg-Gly-Asp (RGD)-modified alginate hydrogels to nonfouling unmodified alginate. Regardless of material, MSC spheroids exhibited reduced caspase activity and greater vascular endothelial growth factor (VEGF) secretion compared with equal numbers of dissociated cells. MSC spheroids in RGD-modified hydrogels demonstrated significantly greater cell survival than spheroids in unmodified alginate. After 5 days in culture, spheroids in RGD-modified gels had similar levels of apoptosis, but more than a twofold increase in VEGF secretion compared with spheroids in unmodified gels. All gels contained mineralized tissue 8 weeks after subcutaneous implantation, and cells entrapped in RGD-modified alginate exhibited greater mineralization versus cells in unmodified gels. Immunohistochemistry confirmed more diffuse osteocalcin staining in gels containing spheroids compared with dissociated controls. This study demonstrates the promise of cell-instructive biomaterials to direct survival and function of MSC spheroids for bone tissue engineering applications. Mesenchymal stem cell (MSC) spheroids exhibit improved therapeutic potential in vitro compared with dissociated MSCs, yet spheroids are directly injected into tissues, ceding control of cell function to the extracellular matrix and potentially limiting the duration of improvement. Cell delivery using adhesive biomaterials promotes cell retention and function. These studies explored the role of adhesion to the surrounding matrix on spheroid function. When entrapped in an adhesive biomaterial, MSC spheroids exhibited improved survival and proangiogenic growth factor secretion in vitro and bone formation in vivo compared with cells in nonadhesive hydrogels. These findings demonstrate the value of deploying MSC spheroids in instructive biomaterials to improve cell function.

Differentiation of hepatocytes from induced pluripotent stem cells derived from human hair follicle mesenchymal stem cells.

Due to the limitations of organ donors and immune rejection in severe liver diseases, stem cell-based therapy presents a promising application for tissue repair and regeneration. As a novel cell source, mesenchymal stem cells separated from human hair follicles (HF-MSCs) are convenient to obtain and have no age limit. To date, the differentiation of HF-MSCs into hepatocytes has not been reported. In this study, we explored whether HF-MSCs and HF-MSC-derived-induced pluripotent stem cells (HF-iPS) could differentiate into hepatocytes in vitro. Flow cytometry, Oil Red O stain and Alizarin Red stain were used to identify the characteristics of HF-MSCs. The expression of liver-specific gene was detected by immunofluorescence and Quantitative Polymerase Chain Reaction. Periodic Acid-Schiff stain, Indocyanine Green stain and Low-Density Lipoprotein stain were performed to evaluate the functions of induced hepatocyte-like cells (HLCs). HF-MSCs were unable to differentiate into HLCs using previously reported procedures for MSCs from other tissues. However, HF-iPS efficiently induced the generation of HLCs that expressed hepatocyte markers and drug metabolism-related genes. HF-iPS can be used as novel and alternative cellular tools for inducing hepatocytes in vitro, simultaneously benefiting from utilizing HF-MSCs as a noninvasive and convenient cell source for reprogramming.

Effect of calcium hydroxide on mechanical strength and biological properties of bioactive glass

In this manuscript for the first time calcium hydroxide (Ca(OH)2) has been used for preparation of bioactive glass (BG-2) by co-precipitation method and compared with glass prepared using calcium nitrate tetrahydrate Ca(NO3)2·4H2O (BG-1), which is a conventional source of calcium. The new source positively affected physical, biological and mechanical properties of BG-2. The glasses were characterized by Fourier transform infrared (FTIR), X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA-DSC), BET surface area analysis and Knoop hardness. The results showed that BG-2 possessed relatively larger surface properties (100m2g−1 surface area) as compared to BG-1 (78m2g−1), spherical morphology and crystalline phases (wollastonite and apatite) after sintering at lower than conventional temperature. These properties contribute critical role in both mechanical and biological properties of glasses. The Knoop hardness measurements revealed that BG-2 possessed much better hardness (0.43±0.06GPa at 680°C and 2.16±0.46GPa at 980°C) than BG-1 (0.24±0.01 at 680°C and 0.57±0.07GPA at 980°C) under same conditions. Alamar blue Assay and confocal microscopy revealed that BG-2 exhibited better attachment and proliferation of MG63 cells. Based on the improved biological properties of BG-2 as a consequent of novel calcium source selection, BG-2 is proposed as a bioactive ceramic for hard tissue repair and regeneration applications.

Fabrication of alumina porous scaffolds with aligned oriented pores for bone tissue engineering applications

In the present study, porous alumina scaffolds with specific orientation and anisotropic properties are fabricated for application in bone tissue repair. The scaffolds with double shape pores, tubular oriented and isotropic rounded pores, were prepared using alumina and silica as starting materials by the slip casting route. Milled polyurethane foam and silk fibers were applied as replica materials as well. The effect of fiber types and diameter and number of fibers on the microstructure and pore size was studied. Moreover, different characteristics such as porosity, density, orientation, flexural strength and compressive strength of the samples were investigated. Results showed that various fibers with different diameters and numbers led to forming the pores with different pore sizes, microstructure and consequently changes in the physical and mechanical properties. In addition, the simultaneous presence of fibers and particles led to more porous scaffolds. The oriented tiny micro-tube and rounded pores were observed in all porous ceramic scaffolds. Mechanical testing showed an anisotropy in the mechanical behaviors such that higher strengths were observed in the oriented pore direction than that of transverse. With increasing the number and diameter of silk fibers, the scaffolds with a high porosity up to 68 vol% and proper flexural strength were obtained.

Design of a Novel Composite H2S‐Releasing Hydrogel for Cardiac Tissue Repair

The design of 3D scaffolds is a crucial step in the field of regenerative medicine. Scaffolds should be degradable and bioresorbable as well as display good porosity, interconnecting pores, and topographic features; these properties favour tissue integration and vascularization. These requirements could be fulfilled by hybrid hydrogels using a combination of natural and synthetic components. Here, the mechanical and biological properties of a polyethylene glycol-fibrinogen hydrogel (PFHy) are improved in order to favour the proliferation and differentiation of human Sca-1(pos) cardiac progenitor cells (hCPCs). PFHys are modified by embedding air- or perfluorohexane-filled bovine serum albumin microbubbles (MBs) and characterized. Changes in cell morphology are observed in MBs-PFHys, suggesting that MBs could enhance the formation of bundles of cells and influence the direction of the spindle growth. The properties of MBs as carriers of active macromolecules are also exploited. For the first time, enzyme-coated MBs have been used as systems for the production of hydrogen sulfide (H2 S)-releasing scaffolds. Novel H2 S-releasing PFHys are produced, which are able to improve the growth of hCPCs. This novel 3D cell-scaffold system will allow the assessment of the effects of H2 S on the cardiac muscle regeneration with its potential applications in tissue repair.

Chitosan based biocomposite scaffolds for bone tissue engineering

The clinical demand for scaffolds and the diversity of available polymers provide freedom in the fabrication of scaffolds to achieve successful progress in bone tissue engineering (BTE). Chitosan (CS) has drawn much of the attention in recent years for its use as graft material either as alone or in a combination with other materials in BTE. The scaffolds should possess a number of properties like porosity, biocompatibility, water retention, protein adsorption, mechanical strength, biomineralization and biodegradability suited for BTE applications. In this review, CS and its properties, and the role of CS along with other polymeric and ceramic materials as scaffolds for bone tissue repair applications are highlighted.

Proteomic Analysis of Mesenchymal Stem Cells.

Mesenchymal stem or stromal cells (MSCs) are of great interest in biomedical sciences and disease treatment because of their multipotency and wide range of applications for tissue repair and suppression of the immune system. Proteomic analysis of these unique cells has contributed to the identification of important pathways utilized by MSCs to differentiate into distinct tissues as well as important proteins responsible for their special function in vivo and in vitro. However, comparison of proteomic studies in MSCs still suffers from the heterogeneity of MSC preparations. In addition, as proteomics technology advances, several studies can be revisited in order to increase the depth of analysis and, therefore, elucidate more refined mechanisms involved in MSC functionalities. Here, we present detailed protocols to obtain MSCs, as well as protocols to perform in-depth profiling and quantification of alterations in MSC proteomes.