Gellan gum-hyaluronic acid spongy-like hydrogels and cells from adipose tissue synergize promoting neoskin vascularization

A structure-functionality insight into the bioactivity of microbial polysaccharides toward biomedical applications: A review

Microbial polysaccharides (MPs) are biopolymers secreted by microorganisms such as bacteria and fungi during their metabolic processes. Compared to polysaccharides derived from plants and animals, MPs have advantages such as wide sources, high production efficiency, and less susceptibility to natural environmental influences. The most attractive feature of MPs lies in their diverse biological activities, such as antioxidative, anti-tumor, antibacterial, and immunomodulatory activities, which have demonstrated immense potential for applications in functional foods, cosmetics, and biomedicine. These bioactivities are precisely regulated by their sophisticated molecular structure. However, the mechanisms underlying this precise regulation are not yet fully understood and continue to evolve. This article presents a comprehensive review of the most representative species of MPs, including their fermentation and purification processes and their biomedical applications in recent years. In particular, this work presents an in-depth analysis into the structure-activity relationships of MPs across multiple molecular levels. Additionally, this review discusses the challenges and prospects of investigating the structure-activity relationships, providing valuable insights into the broad and high-value utilization of MPs.

Advances in stem cells treatment of diabetic wounds: A bibliometric analysis via CiteSpace

Diabetes is a chronic medical condition that may induce complications such as poor wound healing. Stem cell therapies have shown promise in treating diabetic wounds with pre-clinical and clinical studies. However, little bibliometric analysis has been carried out on stem cells in the treatment of diabetic wounds. In this study, we retrieved relevant papers published from January 1, 2003, to December 31, 2023, from Chinese and English databases. CiteSpace software was used to analyze the authors, institutions, and keywords by standard bibliometric indicators. Our analysis findings indicated that publications on stem cells in the treatment of diabetic wounds kept increasing. The most prolific author was Qian Cai (n = 7) and Mohammad Bayat (n = 16) in Chinese and English databases, respectively. Institutions distribution analysis showed that Chinese institutions conducted most publications, and the most prolific institution was the Chinese People's Liberation Army General Hospital (n = 9) and Shahid Beheshti University of Medical Sciences (n = 17) in Chinese and English databases, respectively. The highest centrality keyword in Chinese and English databases was "wound healing" (0.54) and "in vitro" (0.13), respectively. There were 8 and 11 efficient and convincing keyword clusters produced by a log-likelihood ratio in the Chinese and English databases, respectively. The strongest burst keyword was "exosome" (strength 3.57) and "endothelial progenitor cells" (strength 7.87) in the Chinese and English databases, respectively. These findings indicated a direction for future therapies and research on stem cells in the treatment of diabetic wounds.

Vascularized 3D Human Skin Models in the Forefront of Dermatological Research

In vitro engineered skin models are emerging as an alternative platform to reduce and replace animal testing in dermatological research. Despite the progress made in recent years, considerable challenges still exist for the inclusion of diverse cell types within skin models. Blood vessels, in particular, are essential in maintaining tissue homeostasis and are one of many primary contributors to skin disease inception and progression. Substantial efforts in the past have allowed the successful fabrication of vascularized skin models that are currently utilized for disease modeling and drugs/cosmetics testing. This review first discusses the need for vascularization within tissue-engineered skin models, highlighting their role in skin grafting and disease pathophysiology. Second, the review spotlights the milestones and recent progress in the fabrication and utilization of vascularized skin models. Additionally, advances including the use of bioreactors, organ-on-a-chip devices, and organoid systems are briefly explored. Finally, the challenges and future outlook for vascularized skin models are addressed.

Conductive interpenetrating network organohydrogels of gellan gum/polypyrrole with weather-tolerance, piezoresistive sensing and shape-memory capability

To develop ecofriendly multifunctional gel materials for sustainable flexible electronic devices, composite organohydrogels of gellan gum (GG) and polypyrrole (PPy) with an interpenetrating network structure (IPN-GG/PPy organohydrogels) were developed first time, through fabrication of GG organohydrogels followed by in-situ oxidation polymerization of pyrrole inside. Combination of water with glycerol can not only impart environment-stability to GG hydrogels but promote the mechanics remarkably, with the compressive strength amplified by 1250 % from 0.02 to 0.27 MPa. Incorporation of PPy confers electrical conductivity to the GG organohydrogel as well as promoting the mechanical performance further. The maximum conductivity of the IPN-GG/PPy organohydrogels reached 1.2 mS/cm at 25 °C, and retained at 0.6 mS/cm under -20 °C and 0.56 mS/cm after 7 days' exposure in 25 °C and 60 % RH. The compression strength of that with the maximum conductivity increases by 170 % from 0.27 to 0.73 MPa. The excellent conductivity and mechanical properties endow the IPN-GG/PPy organohydrogels good piezoresistive strain/pressure sensing behavior. Moreover, the thermo-reversible GG network bestows them shape-memory capability. The multifunctionality and intrinsic eco-friendliness is favorable for sustainable application in fields such as flexible electronics, soft robotics and artificial intelligence, competent in motion recognition, physiological signal monitoring, intelligent actuation.

Synthesis and characterization of gellan gum-based hydrogels for drug delivery applications

In this study, gellan gum (Gel) derivatives were allowed to interact via aqueous Diels-Alder chemistry without the need for initiators, producing a crosslinked hydrogel network that exhibited good potential as a drug carrier using tramadol as a drug model. Hydrogel conjugation was achieved by the synthesis of a maleimide and furan-functionalized Gel, and the pre- and post-gelation chemical structure of the resulting hydrogel precursors was fully investigated. Potential uses of the developed hydrogel in the pharmaceutical industry were also evaluated by looking at its gelation duration, temperature, morphologies, swelling, biodegradation, and mechanical characteristics. The Gel-FM hydrogels were safe, showed good antimicrobial activity, and had a low storage modulus, which meant that they could be used in many biochemical fields. The encapsulation and release of tramadol from the hydrogel system in phosphate-buffered saline (PBS) at 37 °C were investigated under acidic and slightly alkaline conditions, replicating the stomach and intestinal tracts, respectively. The in-vitro release profile showed promising results for drug encapsulation, revealing that the drug could safely be well-encapsulated in acidic stomach environments and released more quickly in slightly alkaline intestinal environments. This implies that the hydrogels produced could work well as polymers for specifically delivering medication to the colon.

Adhesivity-tuned bioactive gelatin/gellan hybrid gels drive efficient wound healing

Gelatin-based hydrogels have been widely used for wound healing applications. However, increase in ligand density and reduction in pore size with increasing gelatin concentration may delay wound healing by limiting cell infiltration. In this study, we address this shortcoming by combining gelatin with gellan-which is super hydrophilic and non-adhesive to cells. We show that UV crosslinked hybrid gels composed of methacrylated gelatin (GelMA) and methacrylated gellan gum (mGG), possess considerably larger pores and improved mechanical properties compared to GelMA gels. Reduced spreading and reduced formation of focal adhesions on hybrid gels combined with lower contractility and faster detachment upon trypsin-induced de-adhesion suggests that hybrid gels are less adhesive than GelMA gels. Gradual release of fibroblast growth factor (FGF) and silver nanoparticles (AgNPs) incorporated in hybrid gels not only boosts cell migration, but also confers anti-bacterial activity against gram-positive and gram-negative bacteria at concentrations nontoxic to cells. Full thickness wound healing in Wistar rats revealed increased granulation tissue formation in hybrid gels, fastest epithelialization and highest collagen deposition in rats treated with FGF entrapped hybrid gels. Together, our results demonstrate how adhesive tuning and incorporation of bioactive factors can be synergistically combined for achieving complete wound healing.

Innovations in Stem Cell Therapy for Diabetic Wound Healing

Significance: The global burden of diabetic wounds, particularly diabetic foot ulcers, continues to have large economic and social impact throughout the world. Current strategies are not sufficient to overcome this burden of disease. Finding newer, more advanced regenerative cell and tissue-based strategies to reduce morbidity remains paramount. Recent Advances: Recent advances in stem cell therapies are discussed. We also highlight the practical issues of translating these advancing technologies into the clinical setting. Critical Issues: We discuss the use of somatic and induced pluripotent stem cells and the stromal vascular fraction, as well as innovations, including the use of 3D bioprinting of skin. We also explore related issues of using regenerative techniques in clinical practice, including the current regulatory landscape and translatability of in vivo research. Future Directions: Advances in stem cell manipulation showcase the best therapeutic resources available to enhance mechanisms of wound healing such as angiogenesis, cell proliferation, and collagen synthesis; potential methods include changing the scaffold microenvironment, including relative oxygen tension, and the use of gene modification and nanotechnology. Secretome engineering, particularly the use of extracellular vesicles, may be another potential cell-derived therapeutic that may enable use of cell-free translational therapy.

Effect of photobiomodulation on the behaviour of mesenchymal stem cells in three-dimensional cultures

Photobiomodulation (PBM) has been proposed as a strategy to improve the regenerative capacity of human adipose-derived stem cells (hASCs). Yet, this effect has been proved in 2D culture conditions. To analyze the effect of different doses of laser irradiation (660 nm) with different levels of energy (1 J, 2 J and 6 J) on hASCs cultured at 2D and 3D conditions. We used gellan gum spongy-like hydrogels as a biomaterial to 3D culture hASCs. Different doses (1-7 daily irradiations) and energy levels (1-6 J) of PBM were applied, and the metabolic activity, viability, proliferation, and release of ROS and IL-8 was evaluated up to 7 days. In 3D, cell proliferation increased at high energy (6 J) and after a single dose of irradiation, while in 2D, metabolic activity and proliferation was enhanced only after 3 doses and independently of the energy. More than 1 dose was needed to promote ROS secretion both in 2D and 3D culture conditions. Interestingly, a decrease of IL-8 secretion was detected only in 3D after 3-7 daily irradiations. Overall, hASCs response to PBM was not only dependent on the energy level and the number of applied stimuli, but also on the in vitro culture conditions.

Human adipose-derived mesenchymal stem cells laden in gellan gum spongy-like hydrogels for volumetric muscle loss treatment

BACKGROUND

volumetric muscle loss (VML) is a traumatic massive loss of muscular tissue which frequently leads to amputation, limb loss, or lifetime disability. The current medical intervention is limited to autologous tissue transfer, which usually leads to non-functional tissue recovery. Tissue engineering holds a huge promise for functional recovery.

METHODS

in this work, we evaluated the potential of human adipose-derived mesenchymal stem cells (hASCs) pre-cultured in gellan gum based spongy-like hydrogels (SLHs).

RESULTS

in vitro, hASCs were spreading, proliferating, and releasing growth factors and cytokines (i.e. fibroblast growth factor, hepatocyte growth factor, insulin-like growth factor 1, interleukin-6 (IL-6), IL-8, IL-10, vascular endothelial growth factor) important for muscular regeneration. After implantation into a volumetric muscle loss (VML) mouse model, implants were degrading overtime, entirely integrating into the host between 4 and 8 weeks. In both SLH and SLH + hASCs defects, infiltrated cells were observed inside constructs associated with matrix deposition. Also, minimal collagen deposition was marginally observed around the constructs along both time-points. Neovascularization (CD31+vessels) and neoinnervation (β-III tubulin+bundles) were significantly detected in the SLH + hASCs group, in relation to the SHAM (empty lesion). A higher density ofα-SA+and MYH7+cells were found in the injury site among all different experimental groups, at both time-points, in relation to the SHAM. The levels ofα-SA, MyoD1, and myosin heavy chain proteins were moderately increased in the SLH + hASCs group after 4 weeks, and in the hASCs group after 8 weeks, in relation to the SHAM.

CONCLUSIONS

taken together, defects treated with hASCs-laden SLH promoted angiogenesis, neoinnervation, and the expression of myogenic proteins.

Senotherapeutic peptide treatment reduces biological age and senescence burden in human skin models

Cellular senescence is known to play a role in age-related skin function deterioration which potentially influences longevity. Here, a two-step phenotypic screening was performed to identify senotherapeutic peptides, leading to the identification of Peptide (Pep) 14. Pep 14 effectively decreased human dermal fibroblast senescence burden induced by Hutchinson-Gilford Progeria Syndrome (HGPS), chronological aging, ultraviolet-B radiation (UVB), and etoposide treatment, without inducing significant toxicity. Pep 14 functions via modulation of PP2A, an understudied holoenzyme that promotes genomic stability and is involved in DNA repair and senescence pathways. At the single-cell level, Pep 14 modulates genes that prevent senescence progression by arresting the cell cycle and enhancing DNA repair, which consequently reduce the number of cells progressing to late senescence. When applied on aged ex vivo skin, Pep 14 promoted a healthy skin phenotype with structural and molecular resemblance to young ex vivo skin, decreased the expression of senescence markers, including SASP, and reduced the DNA methylation age. In summary, this work shows the safe reduction of the biological age of ex vivo human skins by a senomorphic peptide.

Gellan gum spongy-like hydrogel-based dual antibiotic therapy for infected diabetic wounds

Diabetic foot infection (DFI) is an important cause of morbidity and mortality. Antibiotics are fundamental for treating DFI, although bacterial biofilm formation and associated pathophysiology can reduce their effectiveness. Additionally, antibiotics are often associated with adverse reactions. Hence, improved antibiotic therapies are required for safer and effective DFI management. On this regard, drug delivery systems (DDSs) constitute a promising strategy. We propose a gellan gum (GG)-based spongy-like hydrogel as a topical and controlled DDS of vancomycin and clindamycin, for an improved dual antibiotic therapy against methicillin-resistant Staphylococcus aureus (MRSA) in DFI. The developed DDS presents suitable features for topical application, while promoting the controlled release of both antibiotics, resulting in a significant reduction of in vitro antibiotic-associated cytotoxicity without compromising antibacterial activity. The therapeutic potential of this DDS was further corroborated in vivo, in a diabetic mouse model of MRSA-infected wounds. A single DDS administration allowed a significant bacterial burden reduction in a short period of time, without exacerbating host inflammatory response. Taken together, these results suggest that the proposed DDS represents a promising strategy for the topical treatment of DFI, potentially overcoming limitations associated with systemic antibiotic administration and minimizing the frequency of administration.

Design of Injectable Bioartificial Hydrogels by Green Chemistry for Mini-Invasive Applications in the Biomedical or Aesthetic Medicine Fields

Bioartificial hydrogels are hydrophilic systems extensively studied for regenerative medicine due to the synergic combination of features of synthetic and natural polymers. Injectability is another crucial property for hydrogel mini-invasive administration. This work aimed at engineering injectable bioartificial in situ cross-linkable hydrogels by implementing green and eco-friendly approaches. Specifically, the versatile poly(ether urethane) (PEU) chemistry was exploited for the development of an amphiphilic PEU, while hyaluronic acid was selected as natural component. Both polymers were functionalized to expose thiol and catechol groups through green water-based carbodiimide-mediated grafting reactions. Functionalization was optimized to maximize grafting yield while preserving group functionality. Then, polymer miscibility was studied at the macro-, micro-, and nano-scale, suggesting the formation of hydrogen bonds among polymeric chains. All hydrogels could be injected through G21 and G18 needles in a wide temperature range (4-25 °C) and underwent sol-to-gel transition at 37 °C. The addition of an oxidizing agent to polymer solutions did not improve the gelation kinetics, while it negatively affected hydrogel stability in an aqueous environment, suggesting the occurrence of oxidation-triggered polymer degradation. In the future, the bioartificial hydrogels developed herein could find application in the biomedical and aesthetic medicine fields as injectable formulations for therapeutic agent delivery.

Advances of hydrogel combined with stem cells in promoting chronic wound healing

Wounds can be divided into two categories, acute and chronic. Acute wounds heal through the normal wound healing process. However, chronic wounds take longer to heal, leading to inflammation, pain, serious complications, and an economic burden of treatment costs. In addition, diabetes and burns are common causes of chronic wounds that are difficult to treat. The rapid and thorough treatment of chronic wounds, including diabetes wounds and burns, represents a significant unmet medical need. Wound dressings play an essential role in chronic wound treatment. Various biomaterials for wound healing have been developed. Among these, hydrogels are widely used as wound care materials due to their good biocompatibility, moisturizing effect, adhesion, and ductility. Wound healing is a complex process influenced by multiple factors and regulatory mechanisms in which stem cells play an important role. With the deepening of stem cell and regenerative medicine research, chronic wound treatment using stem cells has become an important field in medical research. More importantly, the combination of stem cells and stem cell derivatives with hydrogel is an attractive research topic in hydrogel preparation that offers great potential in chronic wound treatment. This review will illustrate the development and application of advanced stem cell therapy-based hydrogels in chronic wound healing, especially in diabetic wounds and burns.

Highly tailorable gellan gum nanoparticles as a platform for the development of T cell activator systems

Background

T cell priming has been shown to be a powerful immunotherapeutic approach for cancer treatment in terms of efficacy and relatively weak side effects. Systems that optimize the stimulation of T cells to improve therapeutic efficacy are therefore in constant demand. A way to achieve this is through artificial antigen presenting cells that are complexes between vehicles and key molecules that target relevant T cell subpopulations, eliciting antigen-specific T cell priming. In such T cell activator systems, the vehicles chosen to deliver and present the key molecules to the targeted cell populations are of extreme importance. In this work, a new platform for the creation of T cell activator systems based on highly tailorable nanoparticles made from the natural polymer gellan gum (GG) was developed and validated.

Methods

GG nanoparticles were produced by a water in oil emulsion procedure, and characterized by dynamic light scattering, high resolution scanning electronic microscopy and water uptake. Their biocompatibility with cultured cells was assessed by a metabolic activity assay. Surface functionalization was performed with anti-CD3/CD28 antibodies via EDC/NHS or NeutrAvidin/Biotin linkage. Functionalized particles were tested for their capacity to stimulate CD4⁺ T cells and trigger T cell cytotoxic responses.

Results

Nanoparticles were approximately 150 nm in size, with a stable structure and no detectable cytotoxicity. Water uptake originated a weight gain of up to 3200%. The functional antibodies did efficiently bind to the nanoparticles, as confirmed by SDS-PAGE, which then targeted the desired CD4⁺ populations, as confirmed by confocal microscopy. The developed system presented a more sustained T cell activation over time when compared to commercial alternatives. Concurrently, the expression of higher levels of key cytotoxic pathway molecules granzyme B/perforin was induced, suggesting a greater cytotoxic potential for future application in adoptive cancer therapy.

Conclusions

Our results show that GG nanoparticles were successfully used as a highly tailorable T cell activator system platform capable of T cell expansion and re-education.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00297-z.

Research Progress on Emerging Polysaccharide Materials Applied in Tissue Engineering

The development and application of polysaccharide materials are popular areas of research. Emerging polysaccharide materials have been widely used in tissue engineering fields such as in skin trauma, bone defects, cartilage repair and arthritis due to their stability, good biocompatibility and reproducibility. This paper reviewed the recent progress of the application of polysaccharide materials in tissue engineering. Firstly, we introduced polysaccharide materials and their derivatives and summarized the physicochemical properties of polysaccharide materials and their application in tissue engineering after modification. Secondly, we introduced the processing methods of polysaccharide materials, including the processing of polysaccharides into amorphous hydrogels, microspheres and membranes. Then, we summarized the application of polysaccharide materials in tissue engineering. Finally, some views on the research and application of polysaccharide materials are presented. The purpose of this review was to summarize the current research progress on polysaccharide materials with special attention paid to the application of polysaccharide materials in tissue engineering.

Pushing the Natural Frontier: Progress on the Integration of Biomaterial Cues toward Combinatorial Biofabrication and Tissue Engineering

The engineering of fully functional, biological-like tissues requires biomaterials to direct cellular events to a near-native, 3D niche extent. Natural biomaterials are generally seen as a safe option for cell support, but their biocompatibility and biodegradability can be just as limited as their bioactive/biomimetic performance. Furthermore, integrating different biomaterial cues and their final impact on cellular behavior is a complex equation where the outcome might be very different from the sum of individual parts. This review critically analyses recent progress on biomaterial-induced cellular responses, from simple adhesion to more complex stem cell differentiation, looking at the ever-growing possibilities of natural materials modification. Starting with a discussion on native material formulation and the inclusion of cell-instructive cues, the roles of shape and mechanical stimuli, the susceptibility to cellular remodeling, and the often-overlooked impact of cellular density and cell-cell interactions within constructs, are delved into. Along the way, synergistic and antagonistic combinations reported in vitro and in vivo are singled out, identifying needs and current lessons on the development of natural biomaterial libraries to solve the cell-material puzzle efficiently. This review brings together knowledge from different fields envisioning next-generation, combinatorial biomaterial development toward complex tissue engineering.

Development of an antibiotics delivery system for topical treatment of the neglected tropical disease Buruli ulcer

Skin infection by Mycobacterium ulcerans causes Buruli ulcer (BU) disease, a serious condition that significantly impact patient' health and quality of life and can be very difficult to treat. Treatment of BU is based on daily systemic administration of antibiotics for at least 8 weeks and presents drawbacks associated with the mode and duration of drug administration and potential side effects. Thus, new therapeutic strategies are needed to improve the efficacy and modality of BU therapeutics, resulting in a more convenient and safer antibiotic regimen. Hence, we developed a dual delivery system based on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) microparticles and a gellan gum (GG) hydrogel for delivery of rifampicin (RIF) and streptomycin (STR), two antibiotics used for BU treatment. RIF was successfully loaded into PHBV microparticles, with an encapsulation efficiency of 43%, that also revealed a mean size of 10 µm, spherical form and rough topography. These microparticles were further embedded in a GG hydrogel containing STR. The resultant hydrogel showed a porous microstructure that conferred a high water retention capability (superior to 2000%) and a controlled release of both antibiotics. Also, biological studies revealed antibacterial activity against M. ulcerans, and a good cytocompatibility in a fibroblast cell line. Thus, the proposed drug delivery system can constitute a potential topical approach for treatment of skin ulcers caused by BU disease.

3D bioprinting of gellan gum-based hydrogels tethered with laminin-derived peptides for improved cellular behavior

The treatment of skeletal muscle defects is still a topic of noteworthy concern since surgical intervention is not capable of recovering muscle function. Herein, we propose myoblasts laden in laminin-inspired biofunctionalized gellan gum hydrogels as promising tissue-engineered skeletal muscle surrogates. Gellan gum-based hydrogels were developed by combining native gellan gum (GG) and GG tethered with laminin-derived peptides (CIKVAVS (V), KNRLTIELEVRTC (T) or RKRLQVQLSIRTC (Q)), using different polymer content (0.75%-1.875%). Hydrogels were characterized in terms of compressive modulus, molecules trafficking, and C2C12 adhesion. Hydrogels with higher polymeric content (1.125%-1.875%) showed higher stiffness whereas hydrogels with lower polymer content (0.75%-1.125%) showed higher fluorescein isothiocyanate-dextran molecules diffusion. Cell spreading was achieved regardless of the laminin-derived peptide but preferred in hydrogels with higher polymer content (1.125%-1.875%). Taken together, hydrogels with 1.125% of polymer content were selected for printability analysis. GG-based inks showed a non-newtonian, shear-thinning, and thixotropic behavior suitable for printing. Accordingly, all inks were printable, but inks tethered with T and Q peptides presented some signs of clogging. Cell viability was affected after printing but increased after 7 days of culture. After 7 days, cells were spreading but not showing significant signs of cell-cell communications. Therefore, cell density was increased, thus, myocytes loaded in V-tethered GG-based inks showed higher cell-cell communication, spreading morphology, and alignment 7, 14 days post-printing. Overall, myoblasts laden in laminin-inspired biofunctionalized GG-based hydrogels are a promising skeletal muscle surrogate with the potential to be used as in vitro model or explored for further in vivo applications.

Injectable laminin-biofunctionalized gellan gum hydrogels loaded with myoblasts for skeletal muscle regeneration

Moderate muscular injuries that exceed muscular tissue's auto-healing capacity are still a topic of noteworthy concern. Tissue engineering appeared as a promising therapeutic strategy capable of overcoming this unmet clinical need. To attain such goal, herein we propose an in situ-crosslinking gellan gum (GG)-based hydrogel tethered with a skeletal muscle-inspired laminin-derived peptide RKRLQVQLSIRTC(Q) and encapsulated with skeletal muscle cells (SMCs). Pre-hydrogel solutions presented decreasing shear viscosity with increasing shear rate and shear stress, and required low forces for extrusion, validating their injectability. The GGDVS hydrogel was functionalized with Q-peptide with 30% of efficiency. C2C12 were able to adhere to the developed hydrogel, remained living and spreading 7 days post-encapsulation. Q-peptide release studies indicated that 25% of the unbound peptide can be released from the hydrogels up to 7 days, dependent on the hydrogel formulation. Treatment of a chemically-induced muscular lesion in mice with an injection of C2C12-laden hydrogels improved myogenesis, primarily promoted by the C2C12. In accordance, a high density of myoblasts (α-SA⁺ and MYH7⁺) were localized in tissues treated with the C2C12 (alone or encapsulated in the hydrogel). α-SA protein levels were significantly increased 8 weeks post-treatment with C2C12-laden hydrogels and MHC protein levels were increased in all experimental groups 4 weeks post-treatment, in relation to the SHAM. Neovascularization and neoinnervation was also detected in the defects. Altogether, this study indicates that C2C12-laden hydrogels hold great potential for skeletal muscle regeneration. STATEMENT OF SIGNIFICANCE: We developed an injectable gellan gum-based hydrogel for delivering C2C12 into localized myopathic model. The gellan gum was biofunctinalized with laminin-derived peptide to mimic the native muscular ECM. In addition, hydrogel was physically tuned to mimic the mechanical properties of native tissue. To the best of our knowledge, this formula was used for the first time under the context of skeletal muscle tissue regeneration. The injectability of the developed hydrogel provided non-invasive administration method, combined with a reliable microenvironment that can host C2C12 with nominal inflammation, indicated by the survival and adhesion of encapsulated cells post-injection. The treatment of skeletal muscle defect with the cell-laden hydrogel approach significantly enhanced the regeneration of localized muscular trauma.

Current Understanding of the Applications of Photocrosslinked Hydrogels in Biomedical Engineering

Hydrogel materials have great application value in biomedical engineering. Among them, photocrosslinked hydrogels have attracted much attention due to their variety and simple convenient preparation methods. Here, we provide a systematic review of the biomedical-engineering applications of photocrosslinked hydrogels. First, we introduce the types of photocrosslinked hydrogel monomers, and the methods for preparation of photocrosslinked hydrogels with different morphologies are summarized. Subsequently, various biomedical applications of photocrosslinked hydrogels are reviewed. Finally, some shortcomings and development directions for photocrosslinked hydrogels are considered and proposed. This paper is designed to give researchers in related fields a systematic understanding of photocrosslinked hydrogels and provide inspiration to seek new development directions for studies of photocrosslinked hydrogels or related materials.

Fabrication and assessment of a novel hybrid scaffold consisted of polyurethane-gellan gum-hyaluronic acid-glucosamine for meniscus tissue engineering

The meniscus has inadequate intrinsic regenerative capacity and its damage can lead to degeneration of articular cartilage. Meniscus tissue engineering aims to restore an injured meniscus followed by returning its normal function through bioengineered scaffolds. In the present study, the structural and biological properties of 3D-printed polyurethane (PU) scaffolds dip-coated with gellan gum (GG), hyaluronic acid (HA), and glucosamine (GA) were investigated. The optimum concentration of GG was 3% (w/v) with maintaining porosity at 88.1%. The surface coating of GG-HA-GA onto the PU scaffolds increased the compression modulus from 30.30 kPa to 59.10 kPa, the water uptake ratio from 27.33% to 60.80%, degradation rate from 5.18% to 8.84%, whereas the contact angle was reduced from 104.8° to 59.3°. MTT assay, acridine orange/ethidium bromide (AO/EB) fluorescent staining, and SEM were adopted to assess the behavior of the seeded chondrocytes on scaffolds, and it was found that the ternary surface coating stimulated the cell proliferation, viability, and adhesion. Moreover, the coated scaffolds showed higher expression levels of collagen II and aggrecan genes at day 7 compared to the control groups. Therefore, the fabricated PU-3% (w/v) GG-HA-GA scaffold can be considered as a promising scaffold for meniscus tissue engineering.

Collagen triple helix repeat containing-1 promotes functional recovery of sweat glands by inducing adjacent microvascular network reconstruction in vivo

Background

Sweat glands (SGs) have low regenerative potential after severe burns or trauma and their regeneration or functional recovery still faces many obstacles. In practice, restoring SG function requires not only the structural integrity of the gland itself, but also its neighboring tissues, especially blood vessels. Collagen triple helix repeat containing-1 (CTHRC1) was first identified in vascular repair, and increasing reports showed a close correlation between cutaneous appendage specification, patterning and regeneration. The purpose of the present study was to clarify the role of CTHRC1 in SGs and their adjacent microvessels and find therapeutic strategies to restore SG function.

Methods

The SGs and their adjacent microvascular network of Cthrc1^−/− mice were first investigated using sweat test, laser Doppler imaging, tissue clearing technique and transcriptome analysis. The effects of CTHRC1 on dermal microvascular endothelial cells (DMECs) were further explored with cell proliferation, DiI-labeled acetylated low-density lipoprotein uptake, tube formation and intercellular junction establishment assays. The effects of CTHRC1 on SG function restoration were finally confirmed by replenishing the protein into the paws of Cthrc1^−/− mice.

Results

CTHRC1 is a key regulator of SG function in mice. At the tissue level, Cthrc1 deletion resulted in the disorder and reduction of the microvascular network around SGs. At the molecular level, the knockout of Cthrc1 reduced the expression of vascular development genes and functional proteins in the dermal tissues. Furthermore, CTHRC1 administration considerably enhanced SG function by inducing adjacent vascular network reconstruction.

Conclusions

CTHRC1 promotes the development, morphogenesis and function execution of SGs and their neighboring vasculature. Our study provides a novel target for the restoration or regeneration of SG function in vivo.

Recent advances on bioengineering approaches for fabrication of functional engineered cardiac pumps: A review

The field of cardiac tissue engineering has advanced over the past decades; however, most research progress has been limited to engineered cardiac tissues (ECTs) at the microscale with minimal geometrical complexities such as 3D strips and patches. Although microscale ECTs are advantageous for drug screening applications because of their high-throughput and standardization characteristics, they have limited translational applications in heart repair and the in vitro modeling of cardiac function and diseases. Recently, researchers have made various attempts to construct engineered cardiac pumps (ECPs) such as chambered ventricles, recapitulating the geometrical complexity of the native heart. The transition from microscale ECTs to ECPs at a translatable scale would greatly accelerate their translational applications; however, researchers are confronted with several major hurdles, including geometrical reconstruction, vascularization, and functional maturation. Therefore, the objective of this paper is to review the recent advances on bioengineering approaches for fabrication of functional engineered cardiac pumps. We first review the bioengineering approaches to fabricate ECPs, and then emphasize the unmatched potential of 3D bioprinting techniques. We highlight key advances in bioprinting strategies with high cell density as researchers have begun to realize the critical role that the cell density of non-proliferative cardiomyocytes plays in the cell-cell interaction and functional contracting performance. We summarize the current approaches to engineering vasculatures both at micro- and meso-scales, crucial for the survival of thick cardiac tissues and ECPs. We showcase a variety of strategies developed to enable the functional maturation of cardiac tissues, mimicking the in vivo environment during cardiac development. By highlighting state-of-the-art research, this review offers personal perspectives on future opportunities and trends that may bring us closer to the promise of functional ECPs.

3D hydrogel models of the neurovascular unit to investigate blood-brain barrier dysfunction

The neurovascular unit (NVU), consisting of neurons, glial cells, vascular cells (endothelial cells, pericytes and vascular smooth muscle cells (VSMCs)) together with the surrounding extracellular matrix (ECM), is an important interface between the peripheral blood and the brain parenchyma. Disruption of the NVU impacts on blood-brain barrier (BBB) regulation and underlies the development and pathology of multiple neurological disorders, including stroke and Alzheimer's disease (AD). The ability to differentiate induced pluripotent stem cells (iPSCs) into the different cell types of the NVU and incorporate them into physical models provides a reverse engineering approach to generate human NVU models to study BBB function. To recapitulate the in vivo situation such NVU models must also incorporate the ECM to provide a 3D environment with appropriate mechanical and biochemical cues for the cells of the NVU. In this review, we provide an overview of the cells of the NVU and the surrounding ECM, before discussing the characteristics (stiffness, functionality and porosity) required of hydrogels to mimic the ECM when incorporated into in vitro NVU models. We summarise the approaches available to measure BBB functionality and present the techniques in use to develop robust and translatable models of the NVU, including transwell models, hydrogel models, 3D-bioprinting, microfluidic models and organoids. The incorporation of iPSCs either without or with disease-specific genetic mutations into these NVU models provides a platform in which to study normal and disease mechanisms, test BBB permeability to drugs, screen for new therapeutic targets and drugs or to design cell-based therapies.

Cationic, anionic and neutral polysaccharides for skin tissue engineering and wound healing applications

Today, chronic wound care and management can be regarded as a clinically critical issue. However, the limitations of current approaches for wound healing have encouraged researchers and physicians to develop more efficient alternative approaches. Advances in tissue engineering and regenerative medicine have resulted in the development of promising approaches that can accelerate wound healing and improve the skin regeneration rate and quality. The design and fabrication of scaffolds that can address the multifactorial nature of chronic wound occurrence and provide support for the healing process can be considered an important area requiring improvement. In this regard, polysaccharide-based scaffolds have distinctive properties such as biocompatibility, biodegradability, high water retention capacity and nontoxicity, making them ideal for wound healing applications. Their tunable structure and networked morphology could facilitate a number of functions, such as controlling their diffusion, maintaining wound moisture, absorbing a large amount of exudates and facilitating gas exchange. In this review, the wound healing process and the influential factors, structure and properties of carbohydrate polymers, physical and chemical crosslinking of polysaccharides, scaffold fabrication techniques, and the use of polysaccharide-based scaffolds in skin tissue engineering and wound healing applications are discussed.

Biomimetic Hydrogels to Promote Wound Healing

Wound healing is a common physiological process which consists of a sequence of molecular and cellular events that occur following the onset of a tissue lesion in order to reconstitute barrier between body and external environment. The inherent properties of hydrogels allow the damaged tissue to heal by supporting a hydrated environment which has long been explored in wound management to aid in autolytic debridement. However, chronic non-healing wounds require added therapeutic features that can be achieved by incorporation of biomolecules and supporting cells to promote faster and better healing outcomes. In recent decades, numerous hydrogels have been developed and modified to match the time scale for distinct stages of wound healing. This review will discuss the effects of various types of hydrogels on wound pathophysiology, as well as the ideal characteristics of hydrogels for wound healing, crosslinking mechanism, fabrication techniques and design considerations of hydrogel engineering. Finally, several challenges related to adopting hydrogels to promote wound healing and future perspectives are discussed.

The Therapeutic Potential of Mesenchymal Stromal Cells for Regenerative Medicine: Current Knowledge and Future Understandings

In recent decades, research on the therapeutic potential of progenitor cells has advanced considerably. Among progenitor cells, mesenchymal stromal cells (MSCs) have attracted significant interest and have proven to be a promising tool for regenerative medicine. MSCs are isolated from various anatomical sites, including bone marrow, adipose tissue, and umbilical cord. Advances in separation, culture, and expansion techniques for MSCs have enabled their large-scale therapeutic application. This progress accompanied by the rapid improvement of transplantation practices has enhanced the utilization of MSCs in regenerative medicine. During tissue healing, MSCs may exhibit several therapeutic functions to support the repair and regeneration of injured tissue. The process underlying these effects likely involves the migration and homing of MSCs, as well as their immunotropic functions. The direct differentiation of MSCs as a cell replacement therapeutic mechanism is discussed. The fate and behavior of MSCs are further regulated by their microenvironment, which may consequently influence their repair potential. A paracrine pathway based on the release of different messengers, including regulatory factors, chemokines, cytokines, growth factors, and nucleic acids that can be secreted or packaged into extracellular vesicles, is also implicated in the therapeutic properties of MSCs. In this review, we will discuss relevant outcomes regarding the properties and roles of MSCs during tissue repair and regeneration. We will critically examine the influence of the local microenvironment, especially immunological and inflammatory signals, as well as the mechanisms underlying these therapeutic effects. Importantly, we will describe the interactions of local progenitor and immune cells with MSCs and their modulation during tissue injury. We will also highlight the crucial role of paracrine pathways, including the role of extracellular vesicles, in this healing process. Moreover, we will discuss the therapeutic potential of MSCs and MSC-derived extracellular vesicles in the treatment of COVID-19 (coronavirus disease 2019) patients. Overall, this review will provide a better understanding of MSC-based therapies as a novel immunoregenerative strategy.

Preparation and evaluation of gellan gum hydrogel reinforced with silk fibers with enhanced mechanical and biological properties for cartilage tissue engineering

Various research about cartilage regeneration using biomaterials has been done recently. Particularly, gellan gum hydrogel (GG) is reported to be suitable as a biomaterial for cartilage tissue engineering (TE) for its water uptaking ability, producibility, and environmental resemblance of native cartilage. Despite these advantages, mechanical and cell adhesion properties are still difficult to modulate. Reinforcement is essential to overcome these problems. Herein, GG was modified by physically blending with different lengths of silk fiber (SF). As SF is expected to improve such disadvantages of GG, mechanical and biological properties were characterized to confirm its reinforcement ability. Mechanical properties such as degradation rate, swelling rate, compression strength, and viscosity were studied and it was confirmed that SF significantly reinforces the mechanical properties of GG. Furthermore, in vitro study was carried out to confirm morphology, biocompatibility, proliferation, and chondrogenesis of chondrocytes encapsulated in the hydrogels. Overall, chondrocytes in the GG blended with SF (SF/GG) showed enhanced cell viability and growth. According to this study, SF/GG can be a promising biomaterial for cartilage TE biomaterial.

Gellan gum/alginate-based Ca-enriched acellular bilayer hydrogel with robust interface bonding for effective osteochondral repair

The treatment of osteochondral (OC) defects remains challenging because of the lack of economical and feasible therapeutic strategies for OC repair and reconstruction. In this study, we report an integrated bilayer hydrogel with robust interface binding force (40 kPa) by facilitating the diffusion of calcium ions to the secondary crosslink of the bilayer hydrogel, in which gellan gum and sodium alginate acted as the chondral layer, gellan gum and hydroxyapatite acted as subchondral layer. This integrated construct has high cytocompatibility, and can seed with mesenchymal stem cells (MSCs) related to different functional protein expression for cartilage and bone formation, respectively. Furthermore, in the rabbit critical-sized osteochondral defect model (4.0 mm in diameter and 8.0 mm in depth), the calcium enriched hydrogel act as a calcium reservoir, promote neovascularization at week 4, and repair the critical defect at week 8, demonstrating the feasible preparation of an acellular hydrogel for OC repair.

In vitro vascularization of tissue engineered constructs by non-viral delivery of pro-angiogenic genes

Vascularization is still one of the major challenges in tissue engineering. In the context of tissue regeneration, the formation of capillary-like structures is often triggered by the addition of growth factors which are associated with high cost, bolus release and short half-life. As an alternative to growth factors, we hypothesized that delivering genes-encoding angiogenic growth factors to cells in a scaffold microenvironment would lead to a controlled release of angiogenic proteins promoting vascularization, simultaneously offering structural support for new matrix deposition. Two non-viral vectors, chitosan (Ch) and polyethyleneimine (PEI), were tested to deliver plasmids encoding for vascular endothelial growth factor (pVEGF) and fibroblast growth factor-2 (pFGF2) to human dermal fibroblasts (hDFbs). hDFbs were successfully transfected with both Ch and PEI, without compromising the metabolic activity. Despite low transfection efficiency, superior VEGF and FGF-2 transgene expression was attained when pVEGF was delivered with PEI and when pFGF2 was delivered with Ch, impacting the formation of capillary-like structures by primary human dermal microvascular endothelial cells (hDMECs). Moreover, in a 3D microenvironment, when PEI-pVEGF and Ch-FGF2 were delivered to hDFbs, cells produced functional pro-angiogenic proteins which induced faster formation of capillary-like structures that were retained in vitro for longer time in a Matrigel assay. The dual combination of the plasmids resulted in a downregulation of the production of VEGF and an upregulation of FGF-2. The number of capillary-like segments obtained with this system was inferior to the delivery of plasmids individually but superior to what was observed with the non-transfected cells. This work confirmed that cell-laden scaffolds containing transfected cells offer a novel, selective and alternative approach to impact the vascularization during tissue regeneration. Moreover, this work provides a new platform for pathophysiology studies, models of disease, culture systems and drug screening.

Pristine Gellan Gum-Collagen Interpenetrating Network Hydrogels as Mechanically Enhanced Anti-inflammatory Biologic Wound Dressings for Burn Wound Therapy

Gellan gum is a biologically inert natural polymer that is increasingly favored as a material-of-choice to form biorelevant hydrogels. However, as a burn wound dressing, native gellan gum hydrogels do not drive host's biology toward regeneration and are mechanically inadequate wound barriers. To overcome these issues, we fabricateda gellan gum-collagen full interpenetrating network (full-IPN) hydrogel that can house adipose-derived mesenchymal stem cells (ADSCs) and employ their multilineage differentiation potential and produce wound-healing paracrine factors to reduce inflammation and promote burn wound regeneration. Herein, a robust temperature-dependent simultaneous IPN (SIN) hydrogel fabrication process was demonstrated using applied rheology for the first time. Subsequently after fabrication, mechanical characterization assays showed that the IPN hydrogels were easy to handle without deforming and retained sufficient mass to effect ADSCs' anti-inflammation property in a simulated wound environment. The IPN hydrogels' increased stiffness proved conducive for mechanotransduced cell adhesion. Scanning electron microscopy revealed theIPN's porous network, which enabled encapsulated ADSCs to spread and proliferate, for up to 3 weeks of culture, further shown by cells' dynamic filopodia extension observed in 3D confocal images. Successful incorporation of ADSCs accorded the IPN hydrogels with biologic wound-dressing properties, which possess the ability to promote human dermal fibroblast migration and secrete an anti-inflammatory paracrine factor, TSG-6 protein, as demonstrated in the 2D scratch wound assay and ELISA, respectively. More importantly, upon application onto murine full thickness burn wounds, our biologic wound dressing enhanced early wound closure, reduced inflammation, and promoted complete skin regeneration. Altogether, our results highlight the successful mechanical and biological enhancement of the inert matrix of gellan gum. Through completely natural procedures, a highly applicable biologic wound dressing is introduced for cell-based full thickness burn wound therapy.

Biomedical Applications of Bacterial Exopolysaccharides: A Review

Bacterial exopolysaccharides (EPSs) are an essential group of compounds secreted by bacteria. These versatile EPSs are utilized individually or in combination with different materials for a broad range of biomedical field functions. The various applications can be explained by the vast number of derivatives with useful properties that can be controlled. This review offers insight on the current research trend of nine commonly used EPSs, their biosynthesis pathways, their characteristics, and the biomedical applications of these relevant bioproducts.

Ad-Dressing Stem Cells: Hydrogels for Encapsulation

Regenerative medicine is a novel scientific field that employs the use of stem cells as cell-based therapy for the regeneration and functional restoration of damaged tissues and organs. Stem cells bear characteristics such as the capacity for self-renewal and differentiation towards specific lineages and, therefore, serve as a backup reservoir in case of tissue injuries. Therapeutically, they can be autologously or allogeneically transplanted for tissue regeneration; however, allogeneic stem cell transplantation can provoke host immune responses leading to a host-versus-transplant reaction. A probable solution to this problem is stem cell encapsulation, a technique that utilizes various biomaterials for the creation of a semi-permeable membrane that encases the stem cells. Stem cell encapsulation can be accomplished by employing a great variety of natural and/or synthetic hydrogels and offers many benefits in regenerative medicine, including protection from the host’s immune system and mechanical stress, improved cell viability, proliferation and differentiation, cryopreservation and controlled and continuous delivery of the stem-cell-secreted therapeutic agents. Here, in this review, we report and discuss almost all natural and synthetic hydrogels used in stem cell encapsulation, along with the benefits that these materials, alone or in combination, could offer to cell therapy through functional cell encapsulation.

3D-printing of solvent exchange deposition modeling (SEDM) for a bilayered flexible skin substitute of poly (lactide-co-glycolide) with bioorthogonally engineered EGF

Biodegradable polyesters have been widely used as rigid biomedical apparatus because of high mechanical properties but few flexible implants. Herein, we report a flexible poly(lactide-co-glycolide) (PLGA) scaffold using a rapid in situ formation system based on phase separation by solvent exchange deposition modeling (SEDM), which was different from traditional 3D printing of fused deposition modeling (FDM). The FDM printed product was rigidity, its Young's modulus was approximate 2.6 times higher than that of SEDM printed sample. In addition, the thickness of the solidified ink would not shrink during the SEDM printing process, its surface had nano-/micro pores in favor of protein immobilization and cell adhesion. Then a flexible bilayered scaffold with nano-/microstructure was constructed combing SEDM with electrospinning technology for skin substitute, wherein the SEDM printed sample acted as a sub-layer for cell and tissue ingrowth, the densely packed electrospun nanofibers served as an upper-layer improving the sub-layer's tensile strength by 57.07% and preventing from bacteria as physical barrier. Ultimately, the bilayered scaffold immobilized epidermal growth factor (EGF) by a bioorthogonal approach was successfully applied to facilitate full-thickness wound healing of rats.

Effect of Gellan Gum/Tuna Skin Film in Guided Bone Regeneration in Artificial Bone Defect in Rabbit Calvaria

It is necessary to prevent the invasion of soft tissue into bone defects for successful outcomes in guided bone regeneration (GBR). For this reason, many materials are used as protective barriers to bone defects. In this study, a gellan gum/tuna skin gelatin (GEL/TSG) film was prepared, and its effectiveness in bone regeneration was evaluated. The film exhibited average cell viability in vitro. Experimental bone defects were prepared in rabbit calvaria, and a bone graft procedure with beta-tricalcium phosphate was done. The film was used as a membrane of GBR and compared with results using a commercial collagen membrane. Grafted material did not show dispersion outside of bone defects and the film did not collapse into the bone defect. New bone formation was comparable to that using the collagen membrane. These results suggest that the GEL/TSG film could be used as a membrane for GBR.

Tailoring Gellan Gum Spongy-Like Hydrogels' Microstructure by Controlling Freezing Parameters

Gellan gum (GG) spongy-like hydrogels have been explored for different tissue engineering (TE) applications owing to their highly attractive hydrogel-like features, and improved mechanical resilience and cell performance. Although the whole process for the preparation of these materials is well-defined, we hypothesized that variations occurring during the freezing step lead to batch-to-batch discrepancies. Aiming to address this issue, two freezing devices were tested, to prepare GG spongy-like hydrogels in a more reproducible way. The cooling and freezing rates, the nucleation time and temperature, and the end freezing time were determined at different freezing temperatures (-20, -80, and -210 °C). The efficacy of the devices was assessed by analyzing the physicochemical, mechanical, and biological properties of different formulations. The cooling rate and freezing rate varied between 0.1 and 128 °C/min, depending on the temperature used and the device. The properties of spongy-like hydrogels prepared with the tested devices showed lower standard deviation in comparison to those prepared with the standard process, due to the slower freezing rate of the hydrogels. However, with this method, mean pore size was significantly lower than that with the standard method. Cell entrapment, adhesion, and viability were not affected as demonstrated with human dermal fibroblasts. This work confirmed that batch-to-batch variations are mostly due to the freezing step and that the tested devices allow fine tuning of the scaffolds' structure and properties.

Recent Advances in Natural Gum-Based Biomaterials for Tissue Engineering and Regenerative Medicine: A Review

The engineering of tissues under a three-dimensional (3D) microenvironment is a great challenge and needs a suitable supporting biomaterial-based scaffold that may facilitate cell attachment, spreading, proliferation, migration, and differentiation for proper tissue regeneration or organ reconstruction. Polysaccharides as natural polymers promise great potential in the preparation of a three-dimensional artificial extracellular matrix (ECM) (i.e., hydrogel) via various processing methods and conditions. Natural polymers, especially gums, based upon hydrogel systems, provide similarities largely with the native ECM and excellent biological response. Here, we review the origin and physico-chemical characteristics of potentially used natural gums. In addition, various forms of scaffolds (e.g., nanofibrous, 3D printed-constructs) based on gums and their efficacy in 3D cell culture and various tissue regenerations such as bone, osteoarthritis and cartilage, skin/wound, retinal, neural, and other tissues are discussed. Finally, the advantages and limitations of natural gums are precisely described for future perspectives in tissue engineering and regenerative medicine in the concluding remarks.

Application of Gellan Gum-Based Scaffold for Regenerative Medicine

Gellan gum (GG) is a linear microbial exopolysaccharide which is derived naturally by the fermentation process of Pseudomonas elodea. Application of GG in tissue engineering and regeneration medicine (TERM) is already over 10 years and has shown great potential. Although this biomaterial has many advantages such as biocompatibility, biodegradability, nontoxic in nature, and physical stability in the presence of cations, a variety of modification methods have been suggested due to some disadvantages such as mechanical properties, high gelation temperature, and lack of attachment sites. In this review, the application of GG-based scaffold for tissue engineering and approaches to improve GG properties are discussed. Furthermore, a recent trend and future perspective of GG-based scaffold are highlighted.

Biological Role of Gellan Gum in Improving Scaffold Drug Delivery, Cell Adhesion Properties for Tissue Engineering Applications

Over the past few decades, gellan gum (GG) has attracted substantial research interest in several fields including biomedical and clinical applications. The GG has highly versatile properties like easy bio-fabrication, tunable mechanical, cell adhesion, biocompatibility, biodegradability, drug delivery, and is easy to functionalize. These properties have put forth GG as a promising material in tissue engineering and regenerative medicine fields. Nevertheless, GG alone has poor mechanical strength, stability, and a high gelling temperature in physiological conditions. However, GG physiochemical properties can be enhanced by blending them with other polymers like chitosan, agar, sodium alginate, starch, cellulose, pullulan, polyvinyl chloride, xanthan gum, and other nanomaterials, like gold, silver, or composites. In this review article, we discuss the comprehensive overview and different strategies for the preparation of GG based biomaterial, hydrogels, and scaffolds for drug delivery, wound healing, antimicrobial activity, and cell adhesion. In addition, we have given special attention to tissue engineering applications of GG, which can be combined with another natural, synthetic polymers and nanoparticles, and other composites materials. Overall, this review article clearly presents a summary of the recent advances in research studies on GG for different biomedical applications.

A review of accelerated wound healing approaches: biomaterial- assisted tissue remodeling

Nowadays, due to a growing number of tissue injuries, in particular, skin wounds, induction and promotion of tissue healing responses can be considered as a crucial step towards a complete regeneration. Recently, biomaterial design has been oriented towards promoting a powerful, effective, and successful healing. Biomaterials with wound management abilities have been developed for different applications such as providing a native microenvironment and supportive matrices that induce the growth of tissue, creating physical obstacles against microbial contamination, and to be used as delivery systems for therapeutic reagents. Until now, numerous strategies aiming to accelerate the wound healing process have been utilized and studied with their own pros and cons. In this review, tissue remodeling phenomena, wound healing mechanisms, and their related factors will be discussed. In addition, different methods for induction and acceleration of healing via cell therapy, bioactive therapeutic delivery, and/or biomaterial-based approaches will be reviewed.

The effect of hyaluronic acid hydrogels on dental pulp stem cells behavior

Dental caries and trauma, particularly in childhood, are among the most prevalent teeth problems, which result in the creation of cavities and probably tooth loss. Thus, novel regenerative approaches with high efficiency and less toxicity are required. Stem cell therapy along with the implementation of scaffolds has provided excellent opportunities in the regeneration of teeth structure. Hyaluronic acid (HA) hydrogels have enticed great attention in the field of regenerative medicine. The unique chemical and structural properties of HA and its derivatives have enabled their application in tissue engineering. Several factors such as the location and type of the lesion, teeth age, the type of capping materials determine the success rate of pulp therapy. HA hydrogels have been considered as biocompatible and safe scaffold supports in human dental cell therapies.

Hydrogel-Based Strategies to Advance Therapies for Chronic Skin Wounds

Chronic skin wounds are the leading cause of nontraumatic foot amputations worldwide and present a significant risk of morbidity and mortality due to the lack of efficient therapies. The intrinsic characteristics of hydrogels allow them to benefit cutaneous healing essentially by supporting a moist environment. This property has long been explored in wound management to aid in autolytic debridement. However, chronic wounds require additional therapeutic features that can be provided by a combination of hydrogels with biochemical mediators or cells, promoting faster and better healing. We survey hydrogel-based approaches with potential to improve the healing of chronic wounds by reviewing their effects as observed in preclinical models. Topics covered include strategies to ablate infection and resolve inflammation, the delivery of bioactive agents to accelerate healing, and tissue engineering approaches for skin regeneration. The article concludes by considering the relevance of treating chronic skin wounds using hydrogel-based strategies.

Autologous adipose-derived stem cell transplantation enhances healing of wound with exposed bone in a rat model

OBJECTIVES

Soft tissue wounds with exposed bone often require extended healing times and can be associated with severe complications. We describe the ability of artificial dermis with autogenic adipose-derived stem cells (ADSCs) to promote the healing of wounds with exposed bone in a rat model.

METHODS

Adipose tissues harvested from the bilateral inguinal regions of Wistar rats were used as ADSCs. Rats were randomly divided into control and ADSC groups to investigate the efficacy of ADSC transplantation for wound healing (n = 20 per group). Soft tissue defects were created on the heads of the rats and were covered with artificial dermis with or without the seeded ADSCs. Specimens from these rats were evaluated using digital image analysis, histology, immunohistochemistry, cell labeling, and real-time reverse-transcription polymerase chain reaction (real-time RT-PCR).

RESULTS

The average global wound area was significantly smaller in the ADSC group than in the control group on days 3, 7, and 14 after surgery (p<0.05). After 14 days, the blood vessel density in the wound increased by 1.6-fold in the ADSC group compared with that in the control group (p<0.01). Real-time RT-PCR results showed higher Fgfb and Vegf expression levels at all time points, and higher Tgfb1 and Tgfb3 expression levels until 14 days after surgery in the ADSC group than in the control group (p<0.05).

CONCLUSIONS

In wounds with exposed bone, autogenic ADSCs can promote vascularization and wound healing. Use of this cell source has multiple benefits, including convenient clinical application and lack of ethical concerns.