Effective Tissue Regeneration Research Articles

Pectin nanoparticles loaded with nitric oxide donor drug: A potential approach for tissue regeneration

The process of wound healing and tissue regeneration involves several key mechanisms to ensure the production of new tissues with similar cellular functions. This study investigates the impact of pectin, a natural polysaccharide, and nebivolol hydrochloride (NBV), a nitric oxide (NO) donor drug, on wound healing. Utilizing ionotropic gelation, NBV-loaded pectin nanoparticles were developed following a 2231 full factorial design. The optimized formulation, determined using Design expert® software, exhibited an encapsulation efficiency percentage of 70.68%, zeta potential of −51.4 mV, and a particle size of 572 nm, characterized by a spherical, discrete morphology. An in vivo study was conducted to evaluate the effectiveness of the optimal formulation in wound healing compared to various controls. The results demonstrated the enhanced ability of the optimal formulation to accelerate wound healing. Moreover, histopathological examination further confirmed the formulation's benefits in tissue proliferation and collagen deposition at the wound site 15 days post-injury. This suggests that the developed formulation not only promotes faster healing but does so with minimal side effects, positioning it as a promising agent for effective wound healing and tissue regeneration.

Designer Micro-/Nanocrumpled MXene Multilayer Coatings Accelerate Osteogenesis and Regulate Macrophage Polarization.

Effective tissue regeneration and immune responses are essential for the success of biomaterial implantation. Although the interaction between synthetic materials and biological systems is well-recognized, the role of surface topographical cues in regulating the local osteoimmune microenvironment─specifically, their impact on host tissue and immune cells, and their dynamic interactions─remains underexplored. This study addresses this gap by investigating the impact of surface topography on osteogenesis and immunomodulation. We fabricated MXene/hydroxyapatite (HAP)-coated surfaces with controlled 2.5D nano-, submicro-, and microscale topographical patterns using our custom bottom-up patterning method. These engineered surfaces were employed to assess the behavior of osteoblast precursor cells and macrophage polarization. Our results demonstrate that MXene/HAP-coated surfaces with microscale crumpled topography significantly influence osteogenic activity and macrophage polarization: these surfaces notably enhanced osteoblast precursor cell spreading, proliferation, and differentiation and facilitated a shift in macrophages toward an anti-inflammatory, prohealing M2 phenotype. The observed cell responses indicate that the physical cues from the crumpled topographies, combined with the chemical cues from the MXene/HAP coatings, synergistically create a favorable osteoimmune microenvironment. This study presents the first evidence of employing MXene/HAP-multilayer coated surfaces with finely crumpled topography to concurrently facilitate osteogenesis and immunomodulation for improved implant-to-tissue integration. The tunable topographic patterns of these coatings coupled with a facile and scalable fabrication process make them widely applicable for various biomedical purposes. Our results highlight the potential of these multilayer coatings with controlled topography to improve the in vivo performance and fate of implants by modulating the host response at the material interface.

Extracellular matrix-mimetic immunomodulatory fibrous scaffold based on a peony stamens polysaccharide for accelerated wound healing

Re-establishment of the extracellular matrix (ECM) in wound tissue is critical for activating endogenous tissue repair. In this study, we designed an ECM-like scaffold material using plant polysaccharides and assessed its efficacy through in vitro and in vivo experiments. The scaffold accelerates wound healing by regulating inflammatory responses and accelerating tissue regeneration. Briefly, we isolated two polysaccharides of varying molecular weights from peony stamens. One of the polysaccharides exhibits potent immunomodulatory and tissue regeneration activities. We further prepared electrospinning materials containing this polysaccharide. In vitro investigations have demonstrated the polysaccharide's ability to modulate immune responses by targeting TLR receptors. In vivo experiments utilizing a scaffold composed of this polysaccharide showed accelerated healing of full-thickness skin wounds in mice, promoting rapid tissue regeneration. In conclusion, our study shows that this scaffold can mobilize the endogenous regenerative capacity of tissues to accelerate repair by mimicking the characteristics of ECM. The overall study has implications for the design of new, effective, and safer tissue regeneration strategies.

Chitosan-Based Hierarchical Scaffolds Crosslinked with Genipin

Osteochondral defects present significant challenges for effective tissue regeneration due to the complex composition of bone and cartilage. To address this challenge, this study presents the fabrication of hierarchical scaffolds combining chitosan/β-tricalcium phosphate (β-TCP) to simulate a bone-like layer, interconnected with a silk fibroin layer to mimic cartilage, thus replicating the cartilage-like layer to mimic the native osteochondral tissue architecture. The scaffolds were produced by freeze-drying and then crosslinking with genipin. They have a crosslinking degree of up to 24%, which promotes a structural rearrangement and improved connection between the different layers. Micro-CT analysis demonstrated that the structures have distinct porosity values on their top layer (up to 84%), interface (up to 65%), and bottom layer (up to 77%) and are dependent on the concentration of β-tricalcium phosphate used. Both layers were confirmed to be clearly defined by the distribution of the components throughout the constructs, showing adequate mechanical properties for biomedical use. The scaffolds exhibited lower weight loss (up to 7%, 15 days) after enzymatic degradation due to the combined effects of genipin crosslinking and β-TCP incorporation. In vitro studies showed that the constructs supported ATDC5 chondrocyte-like cells and MC3T3 osteoblast-like cells in duo culture conditions, providing a suitable environment for cell adhesion and proliferation for up to 14 days. Overall, the physicochemical properties and biological results of the developed chitosan/β-tricalcium phosphate/silk fibroin bilayered scaffolds suggest that they may be potential candidates for osteochondral tissue strategies.

Study of mechanical property and biocompatibility of graphene oxide/MEO2MA hydrogel scaffold for wound healing application.

Wound healing is a complex biological process crucial for restoring tissue integrity and preventing infections. The development of advanced materials that facilitate and expedite the wound-healing process has been a focal point in biomedical research. In this study, we aimed to enhance the wound-healing potential of hydrogel scaffolds by incorporating graphene oxide and poly (ethylene glycol) methyl ether methacrylate (MEO2MA). Various masses of graphene oxide were added to MEO2MA hydrogels via free radical polymerisation. Comprehensive characterizations, encompassing mechanical properties, and biocompatibility assays, were conducted to evaluate the hydrogels' suitability for wound healing. In vitro experiments demonstrated that the graphene oxide-based hydrogels exhibited a proper swelling degree and tensile strength, responding effectively to moisture conditions and adhesiveness for wound healing. Notably, the tensile strength significantly increased to 626 kPa in the graphene oxide hydrogels. Biocompatibility assessments revealed that the graphene oxide/MEO2MA hydrogels were non-toxic to human dermal fibroblast cell growth, with no significant difference in cell viability observed in the graphene oxide/MEO2MA hydrogel (H-HG) group. In a rat skin experiment, the wound-healing rate of the hydrogel incorporating graphene oxide surpassed that of the pristine hydrogel after a 15-day treatment, achieving over 95% wound closure in the H-HG group. The histopathological analysis further supported the efficacy of the H-HG hydrogel dressing in promoting more effective tissue regeneration. These results collectively highlight the potential of the graphene oxide/MEO2MA hydrogel scaffold as a promising dressing for medical applications.

Asymmetric adhesive SIS-based wound dressings for therapeutically targeting wound repair

Severe tissue injuries pose a significant risk to human health. Conventional wound dressings fall short in achieving effective tissue regeneration, resulting in suboptimal postoperative healing outcomes. In this study, an asymmetric adhesive wound dressing (marked as SIS/PAA/LAP) was developed, originating from acrylate acid (AA) solution with laponite (LAP) nanoparticles polymerization and photo-crosslinked on the decellularized extracellular matrix small intestinal submucosa (SIS) patch. Extensive studies demonstrated that the SIS/PAA/LAP exhibited higher tissue adhesion strength (~ 33 kPa) and burst strength (~ 22 kPa) compared to conventional wound dressings like Tegaderm and tissue adhesive products. Importantly, it maintained favorable cell viability and demonstrated robust angiogenic capacity. In animal models of full-thickness skin injuries in rats and skin injuries in Bama miniature pigs, the SIS/PAA/LAP could be precisely applied to wound sites. By accelerating the formation of tissue vascularization, it displayed superior tissue repair outcomes. This asymmetrically adhesive SIS-based patch would hold promising applications in the field of wound dressings.

2-N, 6-O sulfated chitosan evokes periosteal stem cells for bone regeneration

Musculoskeletal injuries and bone defects represent a significant clinical challenge, necessitating innovative approaches for effective bone tissue regeneration. In this study, we investigated the potential of harnessing periosteal stem cells (PSCs) and glycosaminoglycan (GAG)-mimicking materials for in situ bone regeneration. Our findings demonstrated that the introduction of 2-N, 6-O sulfated chitosan (26SCS), a GAG-like polysaccharide, enriched PSCs and promoted robust osteogenesis at the defect area. Mechanistically, 26SCS amplifies the biological effect of endogenous platelet-derived growth factor-BB (PDGF-BB) through enhancing the interaction between PDGF-BB and its receptor PDGFRβ abundantly expressed on PSCs, resulting in strengthened PSC proliferation and osteogenic differentiation. As a result, 26SCS effectively improved bone defect repair, even in an osteoporotic mouse model with lowered PDGF-BB level and diminished regenerative potential. Our findings suggested the significant potential of GAG-like biomaterials in regulating PSC behavior, which holds great promise for addressing osteoporotic bone defect repair in future applications.

Biomimetic Materials for Regenerative Medicine: Design and Applications

Bio mimetic materials have shown great potential for tissue engineering and regenerative medicine as they can mimic the natural extracellular matrix (ECM) of tissues and organs. The ECM is a complex network of proteins, glycosaminoglycans, and other bio molecules that provide structural support to cells and regulate their behaviour. Bio mimetic materials can be designed to replicate the biochemical and biophysical properties of the ECM, creating an environment that promotes cell adhesion, proliferation, differentiation, and tissue regeneration. There are different classes of bio mimetic materials, including natural and synthetic polymers, as well as inorganic materials such as Hydroxyapatite and ceramics. Polymers made from nature that assist with with cell growth and differentiation, like collagen, which is fibrin, and hyaluronic acid, for instance, have been utilised extensively in tissue engineering. Both the physical and chemical characteristics of synthetic polymers, which include polyethylene glycol, also known as PEG, and poly lactic acid (PLA), can be modified to satisfy the needs of different tissues. Inorganic materials such as hydroxyapatite and ceramics can mimic the mineralized ECM of bone and tooth tissues, providing a scaffold for cell attachment and mineral deposition. Recent advances in the field of bio mimetic materials include the use of nanotechnology and 3D printing to create complex structures with precise control over their size, shape, and mechanical properties. Nanoparticles and nano fibers can be incorporated into bio mimetic materials to enhance their mechanical strength, surface area, and bioactivity. 3D printing can be used to create customized scaffolds that match the shape of the target tissue, allowing for more effective tissue regeneration.

Novel approach to soft tissue regeneration: in vitro study of compound hyaluronic acid and horizontal platelet-rich fibrin combination.

This study aims to develop a compound biomaterial to achieve effective soft tissue regeneration. Compound hyaluronic acid (CHA) and liquid horizontal-platelet-rich fibrin (H-PRF) were mixed at a ratio of 1:1 to form a CHA-PRF gel. Human gingival fibroblasts (HGFs) were used in this study. The effect of CHA, H-PRF, and the CHA-PRF gel on cell viability was evaluated by CCK-8 assays. Then, the effect of CHA, H-PRF, and the CHA-PRF gel on collagen formation and deposition was evaluated by qRT‒PCR and immunofluorescence analysis. Finally, qRT‒PCR, immunofluorescence analysis, Transwell assays, and scratch wound-healing assays were performed to determine how CHA, H-PRF, and the CHA-PRF gel affect the migration of HGFs. The combination of CHA and H-PRF shortened the coagulation time of liquid H-PRF. Compared to the pure CHA and H-PRF group, the CHA-PRF group exhibited the highest cell proliferation at all time points, as shown by the CCK-8 assay. Col1a and FAK were expressed at the highest levels in the CHA-PRF group, as shown by qRT‒PCR. CHA and PRF could stimulate collagen formation and HGF migration, as observed by fluorescence microscopy analysis of COL1 and F-actin and Transwell and scratch healing assays. The CHA-PRF group exhibited greater potential to promote soft tissue regeneration by inducing cell proliferation, collagen synthesis, and migration in HGFs than the pure CHA or H-PRF group. CHA-PRF can serve as a great candidate for use alone or in combination with autografts in periodontal or peri-implant soft tissue regeneration.

Scaffolds for Dentin-Pulp Complex Regeneration.

Background and Objectives: Regenerative dentistry aims to regenerate the pulp-dentin complex and restore those of its functions that have become compromised by pulp injury and/or inflammation. Scaffold-based techniques are a regeneration strategy that replicate a biological environment by utilizing a suitable scaffold, which is considered crucial for the successful regeneration of dental pulp. The aim of the present review is to address the main characteristics of the different scaffolds, as well as their application in dentin-pulp complex regeneration. Materials and Methods: A narrative review was conducted by two independent reviewers to answer the research question: What type of scaffolds can be used in dentin-pulp complex regeneration? An electronic search of PubMed, EMBASE and Cochrane library databases was undertaken. Keywords including "pulp-dentin regeneration scaffold" and "pulp-dentin complex regeneration" were used. To locate additional reports, reference mining of the identified papers was undertaken. Results: A wide variety of biomaterials is already available for tissue engineering and can be broadly categorized into two groups: (i) natural, and (ii) synthetic, scaffolds. Natural scaffolds often contain bioactive molecules, growth factors, and signaling cues that can positively influence cell behavior. These signaling molecules can promote specific cellular responses, such as cell proliferation and differentiation, crucial for effective tissue regeneration. Synthetic scaffolds offer flexibility in design and can be tailored to meet specific requirements, such as size, shape, and mechanical properties. Moreover, they can be functionalized with bioactive molecules, growth factors, or signaling cues to enhance their biological properties and the manufacturing process can be standardized, ensuring consistent quality for widespread clinical use. Conclusions: There is still a lack of evidence to determine the optimal scaffold composition that meets the specific requirements and complexities needed for effectively promoting dental pulp tissue engineering and achieving successful clinical outcomes.

Releasable, Immune-Instructive, Bioinspired Multilayer Coating Resists Implant-Induced Fibrosis while Accelerating Tissue Repair.

Implantable biomaterials trigger foreign body reactions (FBRs), which reduces the functional life of medical devices and prevents effective tissue regeneration. Although existing therapeutic approaches can circumvent collagen-rich fibrotic encapsulation secondary to FBRs, they disrupt native tissue repair. Herein, a new surface engineering strategy in which an apoptotic-mimetic, immunomodulatory, phosphatidylserine liposome (PSL) is released from an implant coating to induce the formation of a macrophage phenotype that mitigates FBRs and improves tissue healing is described. PSL-multilayers constructed on implant surfaces via the layer-by-layer method release PSLs over a 1-month period. In rat muscles, poly(etheretherketone) (PEEK), a nondegradable polymer implant model, induces FBRs with dense fibrotic scarring under an aberrant cellular profile that recruits high levels of inflammatory infiltrates, foreign body giant cells (FBGCs), scar-forming myofibroblasts, and inflammatory M1-like macrophages but negligible amounts of anti-inflammatory M2-like phenotypes. However, the PSL-multilayer coating markedly diminishes these detrimental signatures by shifting the macrophage phenotype. Unlike other therapeutics, PSL-multilayered coatings also stimulate muscle regeneration. This study demonstrates that PSL-multilayered coatings are effective in eliminating FBRs and promoting regeneration, hence offering potent and broad applications for implantable biomaterials.

Orthopedic Scaffolds: Evaluation of Structural Strength and Permeability of Fluid Flow via an Open Cell Neovius Structure for Bone Tissue Engineering.

The ability of bone to regenerate itself through mechanobiological responses is its dynamic property. Mechanical cues from a neighboring environment produce the structural strain to promote blood flow and bone marrow mobility that in turn aids the bone regeneration process. Occurrences of these phenomena are crucial for the success of metallic scaffolds implanted in the host bone tissue. Thus, permeability and fluid flow-induced wall shear stress (WSS) are two parameters that directly influence cell bioactivities inside a scaffold and are crucial for effective bone tissue regeneration. Given that the scaffolds shall be implanted in the body, permeability assessment was carried out using non-Newtonian fluid. In this work, the triply periodic minimal surface scaffolds with Neovius architectures were fabricated by using selective laser melting technology. The estimation of fluid flow was carried out using computational fluid dynamics (CFD) analysis with a non-Newtonian blood fluid model. Further, the structural strength of various open cell Neovius lattices was evaluated using a static compression test, and in vitro cell culture using Alamar blue assay was evaluated. Results revealed that the values of intrinsic blood flow permeability of the three-dimensional (3D)-printed open cell porous scaffold with Neovius architecture were of the same order of magnitude as those of human bone, ranging from 0.0025 × 10-9 to 0.0152 × 10-9 m2. The structural elastic modulus and compressive strength of NOCL40, NOCL50, and NOCL60 lattices range from 3.27 to 3.71 GPa and 194 to 205 MPa, respectively. All of the values are comparable to the human bone, thus making these lattices a suitable alternative for orthopedic applications.

Secured delivery of basic fibroblast growth factor using human serum albumin-based protein nanoparticles for enhanced wound healing and regeneration

BackgroundBasic fibroblast growth factor (bFGF) is one of the critical components accelerating angiogenesis and tissue regeneration by promoting the migration of dermal fibroblasts and endothelial cells associated with matrix formation and remodeling in wound healing process. However, clinical applications of bFGF are substantially limited by its unstable nature due to rapid decomposition under physiological microenvironment.ResultsIn this study, we present the bFGF-loaded human serum albumin nanoparticles (HSA-bFGF NPs) as a means of enhanced stability and sustained release platform during tissue regeneration. Spherical shape of the HSA-bFGF NPs with uniform size distribution (polydispersity index < 0.2) is obtained via a simple desolvation and crosslinking process. The HSA-bFGF NPs securely load and release the intact soluble bFGF proteins, thereby significantly enhancing the proliferation and migration activity of human dermal fibroblasts. Myofibroblast-related genes and proteins were also significantly down-regulated, indicating decrease in risk of scar formation. Furthermore, wound healing is accelerated while achieving a highly organized extracellular matrix and enhanced angiogenesis in vivo.ConclusionConsequently, the HSA-bFGF NPs are suggested not only as a delivery vehicle but also as a protein stabilizer for effective wound healing and tissue regeneration.

A new era of macrophage-based cell therapy.

Macrophages are essential innate immune cells found throughout the body that have protective and pathogenic functions in many diseases. When activated, macrophages can mediate the phagocytosis of dangerous cells or materials and participate in effective tissue regeneration by providing growth factors and anti-inflammatory molecules. Ex vivo-generated macrophages have thus been used in clinical trials as cell-based therapies, and based on their intrinsic characteristics, they outperformed stem cells within specific target diseases. In addition to the old methods of generating naïve or M2 primed macrophages, the recently developed chimeric antigen receptor-macrophages revealed the potential of genetically engineered macrophages for cell therapy. Here, we review the current developmental status of macrophage-based cell therapy. The findings of important clinical and preclinical trials are updated, and patent status is investigated. Additionally, we discuss the limitations and future directions of macrophage-based cell therapy, which will help broaden the potential utility and clinical applications of macrophages.

Preclinical Studies and Clinical Trials on Cell-Based Treatments for Meniscus Regeneration.

This study aims at performing a thorough review of cell-based treatment strategies for meniscus regeneration in preclinical and clinical studies. The PubMed, Embase, and Web of Science databases were searched for relevant studies (both preclinical and clinical) published from the time of database construction to December 2022. Data related to cell-based therapies for in situ regeneration of the meniscus were extracted independently by two researchers. Assessment of risk of bias was performed according to the Cochrane Handbook for Systematic Reviews of Interventions. Statistical analyses based on the classification of different treatment strategies were performed. A total of 5730 articles were retrieved, of which 72 preclinical studies and 6 clinical studies were included in this review. Mesenchymal stem cells (MSCs), especially bone marrow MSCs (BMSCs), were the most commonly used cell type. Among preclinical studies, rabbit was the most commonly used animal species, partial meniscectomy was the most commonly adopted injury pattern, and 12 weeks was the most frequently chosen final time point for assessing repair outcomes. A range of natural and synthetic materials were used to aid cell delivery as scaffolds, hydrogels, or other morphologies. In clinical trials, there was large variation in the dose of cells, ranging from 16 × 106 to 150 × 106 cells with an average of 41.52 × 106 cells. The selection of treatment strategy for meniscus repair should be based on the nature of the injury. Cell-based therapies incorporating various "combination" strategies such as co-culture, composite materials, and extra stimulation may offer greater promise than single strategies for effective meniscal tissue regeneration, restoring natural meniscal anisotropy, and eventually achieving clinical translation. Impact Statement This review provides an up-to-date and comprehensive overview of preclinical and clinical studies that tested cell-based treatments for meniscus regeneration. It presents novel perspectives on studies published in the past 30 years, giving consideration to the cell sources and dose selection, delivery methods, extra stimulation, animal models and injury patterns, timing of outcome assessment, and histological and biomechanical outcomes, as well as a summary of findings for individual studies. These unique insights will help to shape future research on the repair of meniscus lesions and inform the clinical translation of new cell-based tissue engineering strategies.

Additive Manufacturing of Polymer/Bioactive Glass Scaffolds for Regenerative Medicine: A Review.

Tissue engineering (TE) is a branch of regenerative medicine with enormous potential to regenerate damaged tissues using synthetic grafts such as scaffolds. Polymers and bioactive glasses (BGs) are popular materials for scaffold production because of their tunable properties and ability to interact with the body for effective tissue regeneration. Due to their composition and amorphous structure, BGs possess a significant affinity with the recipient's tissue. Additive manufacturing (AM), a method that allows the creation of complex shapes and internal structures, is a promising approach for scaffold production. However, despite the promising results obtained so far, several challenges remain in the field of TE. One critical area for improvement is tailoring the mechanical properties of scaffolds to meet specific tissue requirements. In addition, achieving improved cell viability and controlled degradation of scaffolds is necessary to ensure successful tissue regeneration. This review provides a critical summary of the potential and limitations of polymer/BG scaffold production via AM covering extrusion-, lithography-, and laser-based 3D-printing techniques. The review highlights the importance of addressing the current challenges in TE to develop effective and reliable strategies for tissue regeneration.

Fabrication of Scratched Nanogrooves for Highly Oriented Cell Alignment and Application as a Wound Healing Dressing.

Using improper wound care materials may cause impaired wound healing, which can involve scar formation and infection. Herein, we propose a facile method to fabricate a cell-alignment scaffold, which can effectively enhance cell growth and migration, leading to the reproduction of cellular arrangements and restoration of tissues. The principle is scratching a diamond lapping film that gives uniaxial nanotopography on substrates. Cells are seeded to follow the geometric cue via contact guidance, resulting in highly oriented cell alignment. Remarkable biocompatibility is also demonstrated by the high cell viability on various substrates. In vivo studies in a wound healing model in mice show that the scratched film supports directed cell guidance on the nanostructure, with significantly reduced wound areas and inhibition of excessive collagen deposition. Rapid recovery of the epidermis and dermis is also shown by histological analyses, suggesting the potential application of the scratching technique as an advanced wound dressing material for effective tissue regeneration.

Research Progress on the Osteogenesis-Related Regulatory Mechanisms of Human Umbilical Cord Mesenchymal Stem Cells.

In recent years, research on human umbilical cord mesenchymal stem cells (hUCMSCs) derived from human umbilical cord tissue has accelerated and entered clinical application research. Compared with mesenchymal stem cells (MSCs) from other sources, hUCMSCs can be extracted from different parts of umbilical cord or from the whole umbilical cord. It has the characteristics of less ethical controversy, high differentiation potential, strong proliferation ability, efficient expansion in vitro, avoiding immune rejection and immune privilege, and avoids the limitations of lack of embryonic stem cells, heterogeneity, ethical and moral constraints. hUCMSCs avoid the need for embryonic stem cell sources, heterogeneity, and ethical and moral constraints. Bone defects are very common in clinical practice, but completely effective bone tissue regeneration treatment is challenging. Currently, autologous bone transplantation and allogeneic bone transplantation are main treatment approaches in clinical work, but each has different shortcomings, such as limited sources, invasiveness, immune rejection and insufficient osteogenic ability. Therefore, to solve the bottleneck of bone tissue regeneration and repair, a great amount of research has been carried out to explore the clinical advantages of hUCMSCs as seed cells to promote osteogenesis.However, the regulation of osteogenic differentiation of hUCMSCs is an extremely complex process. Although a large number of studies have demonstrated that the role of hUCMSCs in enhancing local bone regeneration and repair through osteogenic differentiation and transplantation into the body involves multiple signaling pathways, there is no relevant article that summarize the findings. This article discusses the osteogenesis-related regulatory mechanisms of hUCMSCs, summarizes the currently known related mechanisms, and speculates on the possible signals.

Nanomaterials based on chitosan for skin regeneration: an update.

Dear Editor,Highlights Skin is composed of several layers essential to its response and function to injury. Wound healing process is to achieve a quick and effective skin tissue regeneration. Biopolymers, such as chitosan, have been widely utilized in regenerative medicine. Nanomaterial topical use has been shown to dramatically enhance skin tissue healing. Skin is composed of several layers essential to its response and function to injury: hypodermis, dermis, and epidermis. Damaged skin tissue spontaneously starts the wound healing process when injured1. Inflammation, hemostasis, remodeling, and proliferation (or scar tissue development) stages make up the spontaneous and dynamic repair process that occurs in the wounded tissue during wound healing. Hemostasis is the initial stage following skin injuries, and bleeding is one of the main reasons for early demise2. By replacing tissue that has been destroyed and repairing damaged tissue, wound healing attempts to mend the damaged tissue3. High cellularity characterizes the inflammatory phase (1–3 days after injury), which brought on by the migration of macrophages, neutrophils, and lymphocytes to the site of the wound. This phase functions to clean the wound bed using attracting inflammatory cells to the wound site and promoting hemostasis. The next stage of healing of wounds is the proliferative granulation tissue formation phase (4–14 days after wounding). This stage is characterized by the growth of fibroblasts at the site of the wound and the production of crucial extracellular matrix (ECM) such collagen, elastin, and glycosaminoglycans. The last stage of wound healing is known as remodeling (or scar tissue development), and it is characterized using the replacement of immature type 3 collagen with mature type 1 collagen. As the tissue gets less vascularized in this stage, the skin tissue healing process is ultimately complete4. The goal of the wound healing process is to achieve a quick and effective skin tissue regeneration with maximum function, little to no scarring, and no keloid development. Successful skin tissue healing, however, continues to be a biological challenge and a significant healthcare concern. Especially persistent wounds, such as diabetic and ischemic wounds, often lead to functional ability loss and a rise in pain and infections4. To encourage complete skin tissue healing with the fewest possible adverse effects and expenses, innovative and effective treatments are now being developed vigorously5. To do this, biopolymers, such as chitosan, have been widely utilized in regenerative medicine. Tissue regeneration is accomplished using a variety of adaptable biomaterials that are used to repair, maintain, or enhance damaged skin tissues. Chitosan-based nanomaterials have made great help for the creation of new, appropriate materials for use in a there are numerous application in biomedicine, including those for biosensors, drug delivery, tissue engineering, and diagnostics6. Nanoparticles (NPs), nanogels, and nanofibrous scaffolds are the most prevalent types of chitosan-based nanomaterials. Nanomaterials have significant benefits related to their nanometer sizes, such as their very large surface area compared with their volume and the capacity to enter into cytoplasmic space (increased cellular uptake). Therapeutic substances might be added to chitosan NPs to increase their bioavailability, chemical stability, and biocompatibility, while allowing the pharmacokinetics and pharmacodynamics of the therapeutic agent to be modified, this increases the active drugs’ effectiveness and decreases their toxicity7–9. Nanomaterial topical use has been shown to dramatically enhance skin tissue healing in tissue engineering10. This results from interactions between several biomolecules and ECM elements at the nanoscale11. The primary biological element of the ECM is collagen, which contains fibers that range in size between 50 and 500 nm. Chitosan-nano-based materials, in particular, chitosan nanofibers releasing active drugs, are considered suitable scaffolds for skin tissue engineering12. Since biological cells cannot recreate their original structure without an extracellular guide (scaffold material), the existence of a scaffold is essential for the effective restoration of the original tissue architecture13. Interestingly, the phenotype of cells growing on nanofibrous scaffolds resembles that of cells growing in their native environment. By comparing the nanostructure of nanofibrous materials to that of natural ECM components (collagen), this phenomenon may be understood. Because nanofibrous materials have the ability to direct native human cells along their surface, healing the damaged region, topical administration of these materials can be employed for skin tissue regeneration13. Thus, chitosan-based fibrous nanostructures have a tremendous potential to encourage skin regeneration by resembling the milieu in which human cells and tissues are found naturally. In addition, compounds for the prolonged release of medicinal medicines and biological substances including DNA and proteins have been developed using chitosan-based nanofibrous materials6. There are several methods to create three-dimensional nanofibers, such as electrospinning, phase separation, self-assembly, drawing, and template synthesis6. The most often used method is electrospinning since it is effective and easy. It may be used to create nanofibers with diameters between 5 and 500 nm14. The method is based on injecting a polymer solution into a syringe, then expelling the polymer solution via a metal capillary while using a high-voltage power source14. Nanofibrous materials cannot be formed from aqueous solutions of pure chitosan using the electrospinning technique15. As a result, chitosan is modified or combined with other synthetic and natural polymers for use in tissue engineering, medication delivery, and healing of wounds16. Recently, Zhao et al.10 reviewed the synthesis of nanofibers with renewable polymers, including chitosan. In their review article, the authors highlighted the harmful aspects of preparing chitosan nanofibers in organic solvents for biomedical applications. To enhance the mechanical properties of the nanofibers, the majority of chitosan-based nanofibrous materials combine chitosan with other polymers in an aqueous solution. Due to their biodegradability, biocompatibility, antibacterial, hemostatic, and other properties, chitosan-based nanofibrous materials can be successfully employed for skin regeneration, tissue engineering, wound healing, and hemostasis depending on their chemical composition, and mechanical characteristics, as well as their capacity to allow cell attachment and growth on the surface of nanofibers10. Chitosan-based NPs have furthermore been used for wound healing to chitosan-based nanofibrous scaffolds for the continuous release of therapeutic agents (such as growth factors or antibiotics) in skin tissue regeneration17. As was already mentioned, chitosan itself promotes wound healing. The combination of chitosan with medicinal substances in the form of chitosan-based NPs may improve this effect. Reverse micellization18, reverse emulsion19, desolvation20, emulsion solvent diffusion21, and electrostatic complexation are the techniques utilized to create chitosan NPs22. The simplest of these processes, electrostatic complexation, produces NPs with repeatable size distributions and is carried out in an aqueous solution at ambient temperature and atmospheric pressure. Chitosan NPs can be created when protonated amino groups of chitosan combine with anionic macromolecules such hyaluronic acid, alginate, and DNA or with molecules like (poly) phosphate, sulfate, and citrate to form complexes. This is the last feature characteristics (nontoxicity, hemocompatibility, mucoadhesion, and antibacterial activity), in addition to their capacity to effectively integrate therapeutic compounds, that make them acceptable for biomedical applications23. Chitosan NPs may integrate hydrophilic, hydrophobic, and macromolecules, resulting in a prolonged release of the medications they are encapsulating. This method has been applied in a number of biological settings, including the regeneration of skin tissue. Nanogels are a significant subset of chitosan nanomaterials. Hydrogels in the nano-dimensional range are referred to as nanogels17. Changes in pH, temperature, and ionic content can cause certain nanogels to become stimulus-responsive, which is crucial for drug administration in topical applications17. Nanoscale cross-linked networks of the same or distinct kinds of polymers make up nanogels, which have a high water absorption capacity10. Due to the presence of hydrophilic groups on polymer chains, certain nanogels (hydrogels) can expand when exposed to water10. Nanogels with water-absorbent properties have structures like those of human tissues, making them appropriate for tissue engineering. Therapeutic drugs, biomacromolecules (growth factors, proteins), and NPs can all be included inside the cross-linked network of nanogels24. The persistent and localized release of the therapeutic substance to the target region is made possible by the polymeric structure of the nanogels, which shields the entrapped molecules from quick dissolution25. Depending on the kind of connections connecting various macromolecular chains, nanogels can be categorized as either permanent or reversible. The nanogel is referred to as reversible when secondary forces, like H-bonding and ionic or hydrophobic forces, play the primary role in building the nanogel network. Permanent networks are those created by covalent linkages as a result of polymer cross-linking26. Therefore, novel materials with beneficial qualities for skin regeneration may be created using a variety of nanogel production techniques. As scaffolding for cell adhesion, nanogels have been widely employed in regenerative medicine to enable cellular remodeling that replicates the normal cellular environment25. Nanogels have been used in surgical coatings, prosthetic skin, cartilage, and corneas in this approach. The oral, nasal, ocular, topical, vaginal, and subcutaneous routes are all acceptable ways to give nanogels25. As a result, nanostructured chitosan can be generated as NPs, nanofibers, or nanogels that are appropriate for skin regeneration. Provenance and peer review Not commissioned, internally peer-reviewed. Ethical approval Not applicable. Sources of funding None. Authors’ contribution I.B.A.: conceptualization, data curation, writing – original draft preparation, writing – reviewing and editing. T.B.E.: writing – reviewing and editing, visualization, supervision. H.H., S.Z., and S.E.L.: data curation, writing – original draft preparation, writing – reviewing and editing. Conflicts of interest disclosure The authors declare that they have no financial conflict of interest with regard to the content of this report. Research registration unique identifying number (UIN) Not applicable. Guarantor Talha B. Emran.

Fibrinogen/poly(l-lactide-co-caprolactone) copolymer scaffold: A potent adhesive material for urethral tissue regeneration in urethral injury treatment.

Since a scarcity of sufficient grafting materials, several complications can arise after urothelial defect reconstruction surgery, including severe hypospadias. Accordingly, developing alternative therapies, such as urethral restoration via tissue engineering are needed. In the present study, we developed a potent adhesive and repairing material using fibrinogen-poly(l-lactide-co-caprolactone) copolymer (Fib-PLCL) nanofiber scaffold to achieve effective urethral tissue regeneration after seeding with epithelial cells on the surface. The invitro result found the Fib-PLCL scaffold promoted the attachment and viability of epithelial cells on their surface. The increased expression levels of cytokeratin and actin filaments were observed in Fib-PLCL scaffold than PLCL scaffold. The invivo urethral injury repairing potential of Fib-PLCL scaffold was evaluated using a rabbit urethral replacement model. In this study, a urethral defect was surgically excised and replaced with the Fib-PLCL and PLCL scaffolds or autograft. As expected, the animals healed well after surgery in the Fib-PLCL scaffold group, and no significant strictures were identified. As expected, the cellularized Fib/PLCL grafts have induced the luminal epithelialization, urethral smooth muscle cell remodelling, and capillary development all at the same time. Histological analysis revealed that the urothelial integrity in the Fib-PLCL group had progressed to that of a normal urothelium, with enhanced urethral tissue development. Based on the results, the present study suggests that the prepared fibrinogen-PLCL scaffold is more appropriate for urethral defect reconstruction.