Borax-loaded injectable alginate hydrogels promote muscle regeneration in vivo after an injury

Engineering Innervated Musculoskeletal Tissues for Regenerative Orthopedics and Disease Modeling

Musculoskeletal (MSK) disorders significantly burden patients and society, resulting in high healthcare costs and productivity loss. These disorders are the leading cause of physical disability, and their prevalence is expected to increase as sedentary lifestyles become common and the global population of the elderly increases. Proper innervation is critical to maintaining MSK function, and nerve damage or dysfunction underlies various MSK disorders, underscoring the potential of restoring nerve function in MSK disorder treatment. However, most MSK tissue engineering strategies have overlooked the significance of innervation. This review first expounds upon innervation in the MSK system and its importance in maintaining MSK homeostasis and functions. This will be followed by strategies for engineering MSK tissues that induce post-implantation in situ innervation or are pre-innervated. Subsequently, research progress in modeling MSK disorders using innervated MSK organoids and organs-on-chips (OoCs) is analyzed. Finally, the future development of engineering innervated MSK tissues to treat MSK disorders and recapitulate disease mechanisms is discussed. This review provides valuable insights into the underlying principles, engineering methods, and applications of innervated MSK tissues, paving the way for the development of targeted, efficacious therapies for various MSK conditions.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Comparative Analysis of Crosslinking Methods and Their Impact on the Physicochemical Properties of SA/PVA Hydrogels

Hydrogels, versatile materials used in various applications such as medicine, possess properties crucial for their specific applications, significantly influenced by their preparation methods. This study synthesized 18 different types of hydrogels using sodium alginate (SA) and two molecular weights of polyvinyl alcohol (PVA). Crosslinking agents such as aqueous solutions of calcium (Ca2+) and copper (Cu2+) ions and solutions of these ions in boric acid were utilized. The hydrogels were subjected to compression strength tests and drying kinetics analysis. Additionally, six hydrogel variants containing larger PVA particles underwent Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) post-drying. Some samples were lyophilized, and their surface morphology was examined using scanning electron microscopy (SEM). The results indicate that the choice of crosslinking method significantly impacts the physicochemical properties of the hydrogels. Crosslinking in solutions with higher concentrations of crosslinking ions enhanced mechanical properties and thermal stability. Conversely, using copper ions instead of calcium resulted in slower drying kinetics and reduced thermal stability. Notably, employing boric acid as a crosslinking agent for hydrogels containing heavier PVA molecules led to considerable improvements in mechanical properties and thermal stability.

Chicken muscle antibody array reveals the regulations of LDHA on myoblast differentiation through energy metabolism

Myoblast proliferation and differentiation are highly dynamic and regulated processes in skeletal muscle development. Given that proteins serve as the executors for the majority of biological processes, exploring key regulatory factors and mechanisms at the protein level offers substantial opportunities for understanding the skeletal muscle development. In this study, a total of 607 differentially expressed proteins between proliferation and differentiation in myoblasts were screened out using our chicken muscle antibody array. Biological function analysis revealed the importance of energy production processes and compound metabolic processes in myogenesis. Our antibody array specifically identified an upregulation of LDHA during differentiation, which was associated with the energy metabolism. Subsequent investigation demonstrated that LDHA promoted the glycolysis and TCA cycle, thereby enhancing myoblasts differentiation. Mechanistically, LDHA promotes the glycolysis and TCA cycle but inhibits the ETC oxidative phosphorylation through enhancing the NADH cycle, providing the intermediate metabolites that improve the myoblasts differentiation. Additionally, increased glycolytic ATP by LDHA induces Akt phosphorylation and activate the PI3K-Akt pathway, which might also contribute to the promotion of myoblasts differentiation. Our studies not only present a powerful tool for exploring myogenic regulatory factors in chicken muscle, but also identify a novel role for LDHA in modulating myoblast differentiation through its regulation of cellular NAD+ levels and subsequent downstream effects on mitochondrial function.

Tuning the crosslinking and degradation of hyaluronic acid/gelatin hydrogels using hydrogen peroxide for muscle cell sheet fabrication

Cell sheets have immense potential for medical and pharmaceutical applications including tissue regeneration, drug testing, and disease modelling. In this study, composite hydrogels were prepared from a mixture of phenolated hyaluronic acid (HA-Ph) and gelatin (Gelatin-Ph), with a controlled degree of polymer crosslinking and degradation, to fabricate muscle cell sheets from myoblasts. These hydrogels were obtained via hydrogen peroxide (H2O2)-mediated crosslinking catalysed by horseradish peroxidase (HRP) and peroxide-mediated cleavage of the polymer chains. The degrees of crosslinking and degradation were modulated by altering the exposure time to air containing H2O2. The results showed that exposing a solution of 2% w/v HA-Ph, 0.75% w/v Gelatin-Ph, and 1 unit mL-1 HRP to air with 16 ppm H2O2 for 60 min yielded a stiffer hydrogel (7.16 kPa Young's modulus) than exposure times of 15 min (0.46 kPa) and 120 min (3.98 kPa). Moreover, mouse myoblast C2C12 cells cultured on a stiff hydrogel and induced to undergo myogenic differentiation formed longer and higher-density myotubes than those on softer hydrogels. The cell sheets were readily detached within 5 min by immersing the HA-Ph/Gelatin-Ph hydrogels covered with a monolayer of cells in a medium containing hyaluronidase. Our findings demonstrate that composite hydrogels with properties tuned by controlling the exposure time to H2O2, show great promise as platforms for muscle cell sheet fabrication.

Preparation and Properties of Bimetallic Chitosan Spherical Microgels

The aim of this work was to prepare bimetallic chitosan microgels with high sphericity and investigate the influences of metal-ion type and content on the size, morphology, swelling, degradation and biological properties of microgels. Amino and hydroxyl groups of chitosan (deacetylation degree, DD, of 83.2% and 96.9%) served as ligands in the Cu2+–Zn2+/chitosan complexes with various contents of cupric and zinc ions. The electrohydrodynamic atomization process was used to produce highly spherical microgels with a narrow size distribution and with surface morphology changing from wrinkled to smooth by increasing Cu2+ ions’ quantity in bimetallic systems for both used chitosans. The size of the bimetallic chitosan particles was estimated to be between 60 and 110 µm for both used chitosans, and FTIR spectroscopy indicated the formation of complexes through physical interactions between the chitosans’ functional groups and metal ions. The swelling capacity of bimetallic chitosan particles decreases as the DD and copper (II) ion content increase as a result of stronger complexation with respect to zinc (II) ions. Bimetallic chitosan microgels showed good stability during four weeks of enzymatic degradation, and bimetallic systems with smaller amounts of Cu2+ ions showed good cytocompatibility for both used chitosans.

A Review of Recent Advances in Natural Polymer-Based Scaffolds for Musculoskeletal Tissue Engineering

The musculoskeletal (MS) system consists of bone, cartilage, tendon, ligament, and skeletal muscle, which forms the basic framework of the human body. This system plays a vital role in appropriate body functions, including movement, the protection of internal organs, support, hematopoiesis, and postural stability. Therefore, it is understandable that the damage or loss of MS tissues significantly reduces the quality of life and limits mobility. Tissue engineering and its applications in the healthcare industry have been rapidly growing over the past few decades. Tissue engineering has made significant contributions toward developing new therapeutic strategies for the treatment of MS defects and relevant disease. Among various biomaterials used for tissue engineering, natural polymers offer superior properties that promote optimal cell interaction and desired biological function. Natural polymers have similarity with the native ECM, including enzymatic degradation, bio-resorb and non-toxic degradation products, ability to conjugate with various agents, and high chemical versatility, biocompatibility, and bioactivity that promote optimal cell interaction and desired biological functions. This review summarizes recent advances in applying natural-based scaffolds for musculoskeletal tissue engineering.

Construction of tissue-customized hydrogels from cross-linkable materials for effective tissue regeneration

Hydrogels are prevalent scaffolds for tissue regeneration because of their hierarchical architectures along with outstanding biocompatibility and unique rheological and mechanical properties. For decades, researchers have found that many materials (natural, synthetic, or hybrid) can form hydrogels using different cross-linking strategies. Traditional strategies for fabricating hydrogels include physical, chemical, and enzymatical cross-linking methods. However, due to the diverse characteristics of different tissues/organs to be regenerated, tissue-customized hydrogels need to be developed through precisely controlled processes, making the manufacture of hydrogels reliant on novel cross-linking strategies. Thus, hybrid cross-linkable materials are proposed to tackle this challenge through hybrid cross-linking strategies. Here, different cross-linkable materials and their associated cross-linking strategies are summarized. From the perspective of the major characteristics of the target tissues/organs, we critically analyze how different cross-linking strategies are tailored to fit the regeneration of such tissues and organs. To further advance this field, more appropriate cross-linkable materials and cross-linking strategies should be investigated. In addition, some innovative technologies, such as 3D bioprinting, the internet of medical things (IoMT), and artificial intelligence (AI), are also proposed to improve the development of hydrogels for more efficient tissue regeneration.

Marine Polysaccharides for Wound Dressings Application: An Overview

Wound dressings have become a crucial treatment for wound healing due to their convenience, low cost, and prolonged wound management. As cutting-edge biomaterials, marine polysaccharides are divided from most marine organisms. It possesses various bioactivities, which allowing them to be processed into various forms of wound dressings. Therefore, a comprehensive understanding of the application of marine polysaccharides in wound dressings is particularly important for the studies of wound therapy. In this review, we first introduce the wound healing process and describe the characteristics of modern commonly used dressings. Then, the properties of various marine polysaccharides and their application in wound dressing development are outlined. Finally, strategies for developing and enhancing marine polysaccharide wound dressings are described, and an outlook of these dressings is given. The diverse bioactivities of marine polysaccharides including antibacterial, anti-inflammatory, haemostatic properties, etc., providing excellent wound management and accelerate wound healing. Meanwhile, these biomaterials have higher biocompatibility and biodegradability compared to synthetic ones. On the other hand, marine polysaccharides can be combined with copolymers and active substances to prepare various forms of dressings. Among them, emerging types of dressings such as nanofibers, smart hydrogels and injectable hydrogels are at the research frontier of their development. Therefore, marine polysaccharides are essential materials in wound dressings fabrication and have a promising future.