Research progress in decellularized extracellular matrix hydrogels for intervertebral disc degeneration

Application trends and strategies of hydrogel delivery systems in intervertebral disc degeneration: A bibliometric review

Hydrogels are widely used to explore emerging minimally invasive strategies for intervertebral disc degeneration (IVDD) due to their suitability as drug and cell delivery vehicles. There has been no review of the latest research trends and strategies of hydrogel delivery systems in IVDD for the last decade. In this study, we identify the application trends and strategies in this field through bibliometric analysis, including aspects such as publication years, countries and institutions, authors and publications, and co-occurrence of keywords. The results reveal that the literature in this field has been receiving increasing attention with a trend of growth annually. Subsequently, the hotspots of hydrogels in this field were described and discussed in detail, and we proposed the "four core factors", hydrogels, cells, cell stimulators, and microenvironmental regulation, required for a multifunctional hydrogel for IVDD. Finally, we discuss the popular and emerging mechanistic strategies of hydrogel therapy for IVDD in terms of five aspects: fundamental pathologic changes in IVDD, counteracting cellular senescence, counteracting cell death, improving organelle function, and replenishing exogenous cells. This study provides a reference and a new perspective for future research in this urgently needed field.

Augmented Cornus officinalis Levels in Liuwei Dihuang Decoction Inhibits Nucleus Pulposus Cell Pyroptosis to Enhance Therapeutic Efficacy Against Intervertebral Disc Degeneration

Background

Intervertebral disc (IVD) degeneration (IVDD) is highly prevalent among the elderly population and stands as a leading cause of low back pain. Our prior studies have highlighted the therapeutic potential of Liuwei Dihuang decoction (LWDHD) and its component Cornus officinalis (CO)-derived compounds in alleviating IVDD and osteoarthritis, suggesting beneficial effects of CO in treating degenerative osteoarthropathies. However, uncertainty remains regarding the optimal CO dosage within LWDHD and its potential mechanism for effectively treating IVDD.

Objective

To ascertain the optimal dosage of CO within LWDHD for enhancing its therapeutic efficacy in treating IVDD, through a comparison of its effects across varied dosages using a mouse IVDD model.

Methods

Eight-week-old male C57BL/6J mice were subjected to a lumbar spine instability surgery to induce an IVDD model and received a modified LWDHD formulation containing varied dosages of CO (original dose of CO, or 5- or 10-time dose of CO (referred to as 1 × CO, 5 × CO, and 10 × CO)) for 8 weeks. The therapeutic efficacy on IVDD was evaluated through changes in lumbar spine function, histopathological morphology, extracellular matrix metabolism, nucleus pulposus cell viability, sensory nerve ingrowth, and nucleus pulposus (NP) cell pyroptosis.

Results

Augmenting CO levels in LWDHD led to a dose-dependent increase in the levels of CO-sourced active compounds in the plasma of mice. The modified LWDHD formulations, particularly the 5 × CO, exhibited a favorable pharmacological effect on lumbar function, structural integrity, ECM composition, NP cell viability, and sensory nerve ingrowth. Importantly, all 3 formulations notably mitigated NP cell pyroptosis by activating NRF2/KEAP1 pathway, with the 5 × CO formulation exhibiting superior efficacy. Additionally, a comprehensive score analysis indicated that 5 × CO formulation achieved the highest score.

Conclusion

These data underscore that elevating the dosage of CO to a specific threshold can enhance the effectiveness of LWDHD in treating IVDD.

Recent trends in 3D bioprinting technology for skeletal muscle regeneration

Skeletal muscle is a pro-regenerative tissue, that utilizes a tissue-resident stem cell system to effect repair upon injury. Despite the demonstrated efficiency of this system in restoring muscle mass after many acute injuries, in conditions of severe trauma such as those evident in volumetric muscle loss (VML) (>20 % by mass), this self-repair capability is unable to restore tissue architecture, requiring interventions which currently are largely surgical. As a possible alternative, the generation of artificial muscle using tissue engineering approaches may also be of importance in the treatment of VML and muscle diseases such as dystrophies. Three-dimensional (3D) bioprinting has been identified as a promising technique for regeneration of the complex architecture of skeletal muscle. This review discusses existing treatment strategies following muscle damage, recent progress in bioprinting techniques, the bioinks used for muscle regeneration, the immunogenicity of scaffold materials, and in vitro and in vivo maturation techniques for 3D bio-printed muscle constructs. The pros and cons of these bioink formulations are also highlighted. Finally, we present the current limitations and challenges in the field and critical factors to consider for bioprinting approaches to become more translationa and to produce clinically relevant engineered muscle. STATEMENT OF SIGNIFICANCE: This review discusses the physiopathology of muscle injuries and existing clinical treatment strategies for muscle damage, the types of bioprinting techniques that have been applied to bioprinting of muscle, and the bioinks commonly used for muscle regeneration. The pros and cons of these bioinks are highlighted. We present a discussion of existing gaps in the literature and critical factors to consider for the translation of bioprinting approaches and to produce clinically relevant engineered muscle. Finally, we provide insights into what we believe will be the next steps required before the realization of the application of tissue-engineered muscle in humans. We believe this manuscript is an insightful, timely, and instructive review that will guide future muscle bioprinting research from a fundamental construct creation approach, down a translational pathway to achieve the desired impact in the clinic.

Exploring the Potentials of Chitin and Chitosan-Based Bioinks for 3D-Printing of Flexible Electronics: The Future of Sustainable Bioelectronics

Chitin and chitosan-based bioink for 3D-printed flexible electronics have tremendous potential for innovation in healthcare, agriculture, the environment, and industry. This biomaterial is suitable for 3D printing because it is highly stretchable, super-flexible, affordable, ultrathin, and lightweight. Owing to its ease of use, on-demand manufacturing, accurate and regulated deposition, and versatility with flexible and soft functional materials, 3D printing has revolutionized free-form construction and end-user customization. This study examined the potential of employing chitin and chitosan-based bioinks to build 3D-printed flexible electronic devices and optimize bioink formulation, printing parameters, and postprocessing processes to improve mechanical and electrical properties. The exploration of 3D-printed chitin and chitosan-based flexible bioelectronics will open new avenues for new flexible materials for numerous industrial applications.

High-strength and high-toughness ECM films with the potential for peripheral nerve repair

Extracellular matrix (ECM) scaffolds are widely applied in the field of regeneration as the result of their irreplaceable biological advantages, and the preparation of ECM scaffolds into ECM hydrogels expands the applications to some extent. However, weak mechanical properties of current ECM materials limit the complete exploitation of ECM's biological advantages. To enable ECM materials to be utilized in applications requiring high strength, herein, we created a kind of new ECM material, ECM film, and evaluated its mechanical properties. ECM films exhibited outstanding toughness with no cracks after arbitrarily folding and crumpling, and dramatically high strength levels of 86 ± 17.25 MPa, the maximum of which was 115 MPa. Such spectacular high-strength and high-toughness films, containing only pure ECM without any crosslinking agents and other materials, far exceed current pure natural polymer gel films and even many composite gel films and synthetic polymer gel films. In addition, both PC12 cells and Schwann cells cultured on the surface of ECM films, especially Schwann cells, showed good proliferation, and the neurite outgrowth of the PC12 cells was promoted, indicating the application potential of ECM film in peripheral nerve repair.

Decellularized extracellular matrix-based composite scaffolds for tissue engineering and regenerative medicine

Despite the considerable advancements in fabricating polymeric-based scaffolds for tissue engineering, the clinical transformation of these scaffolds remained a big challenge because of the difficulty of simulating native organs/tissues' microenvironment. As a kind of natural tissue-derived biomaterials, decellularized extracellular matrix (dECM)-based scaffolds have gained attention due to their unique biomimetic properties, providing a specific microenvironment suitable for promoting cell proliferation, migration, attachment and regulating differentiation. The medical applications of dECM-based scaffolds have addressed critical challenges, including poor mechanical strength and insufficient stability. For promoting the reconstruction of damaged tissues or organs, different types of dECM-based composite platforms have been designed to mimic tissue microenvironment, including by integrating with natural polymer or/and syntenic polymer or adding bioactive factors. In this review, we summarized the research progress of dECM-based composite scaffolds in regenerative medicine, highlighting the critical challenges and future perspectives related to the medical application of these composite materials.

Three-Dimensional Bioprinting of Naturally Derived Hydrogels for the Production of Biomimetic Living Tissues: Benefits and Challenges

Three-dimensional bioprinting is the process of manipulating cell-laden bioinks to fabricate living structures. Three-dimensional bioprinting techniques have brought considerable innovation in biomedicine, especially in the field of tissue engineering, allowing the production of 3D organ and tissue models for in vivo transplantation purposes or for in-depth and precise in vitro analyses. Naturally derived hydrogels, especially those obtained from the decellularization of biological tissues, are promising bioinks for 3D printing purposes, as they present the best biocompatibility characteristics. Despite this, many natural hydrogels do not possess the necessary mechanical properties to allow a simple and immediate application in the 3D printing process. In this review, we focus on the bioactive and mechanical characteristics that natural hydrogels may possess to allow efficient production of organs and tissues for biomedical applications, emphasizing the reinforcement techniques to improve their biomechanical properties.

Recent Advances in Decellularized Extracellular Matrix-Based Bioinks for 3D Bioprinting in Tissue Engineering

In recent years, three-dimensional (3D) bioprinting has been widely utilized as a novel manufacturing technique by more and more researchers to construct various tissue substitutes with complex architectures and geometries. Different biomaterials, including natural and synthetic materials, have been manufactured into bioinks for tissue regeneration using 3D bioprinting. Among the natural biomaterials derived from various natural tissues or organs, the decellularized extracellular matrix (dECM) has a complex internal structure and a variety of bioactive factors that provide mechanistic, biophysical, and biochemical signals for tissue regeneration and remodeling. In recent years, more and more researchers have been developing the dECM as a novel bioink for the construction of tissue substitutes. Compared with other bioinks, the various ECM components in dECM-based bioink can regulate cellular functions, modulate the tissue regeneration process, and adjust tissue remodeling. Therefore, we conducted this review to discuss the current status of and perspectives on dECM-based bioinks for bioprinting in tissue engineering. In addition, the various bioprinting techniques and decellularization methods were also discussed in this study.