Melatonin-loaded self-healing hydrogel targets mitochondrial energy metabolism and promotes annulus fibrosus regeneration

Progress of melatonin in the treatment of intervertebral disc degeneration

The most common degenerative condition affecting the musculoskeletal system, and the leading cause of persistent low back pain, is intervertebral disc degeneration (IDD). IDD is increasingly common with age and has a variety of etiologic factors including inflammation, oxidative stress, extracellular matrix (ECM) degradation, and apoptosis that interact with each other to cause IDD. Because it is difficult to determine the exact pathogenesis of IDD, there is a lack of effective therapeutic agents. Melatonin has been intensively studied for its strong anti-inflammatory, antioxidant, and anti-apoptotic properties. Melatonin is a pleiotropic indole-stimulating hormone produced by the pineal gland, which can be used to treat a wide range of degenerative diseases. Therefore, melatonin supplementation may be a viable treatment for IDD. This article reviews the current mechanisms of IDD and the multiple roles regarding melatonin's anti-inflammatory, antioxidant, anti-apoptotic, and mitigating ECM degradation in IDD, incorporating new current research perspectives, as well as recent studies on drug delivery systems.

Melatonin-Loaded Hydrogel Modulates Circadian Rhythms and Alleviates Oxidative Stress and Inflammation to Promote Wound Healing

Circadian rhythm disruption, commonly caused by factors such as jet lag and shift work, is increasingly recognized as a critical factor impairing wound healing. Although melatonin is known to regulate circadian rhythms and has potential in wound repair, its clinical application is limited by low bioavailability. To address these challenges, we developed an alginate-based dual-network hydrogel as a delivery system for melatonin, ensuring its stable and sustained release at the wound site. This approach enhances the efficacy of melatonin in modulating the wound healing process. We investigated the effects of circadian rhythm disruption on the wound microenvironment under the influence of the melatonin-loaded hydrogel with a focus on its biocompatibility, hemostatic properties, and antioxidant response functions. Additionally, we elucidated the mechanisms by which the melatonin-loaded hydrogel system promotes wound healing. Our findings provide insights into the relationship between circadian rhythm disruption and wound healing, offering a promising strategy for the management of chronic wounds associated with circadian rhythm disorders.

A One-Stone-Two-Birds Strategy for Intervertebral Disc Repair: Constructing a Reductive Chelation Hydrogel to Mitigate Oxidative Stress and Promote Disc Matrix Reconstruction

Intervertebral disc degeneration (IVDD) is characterized by fibrosis of nucleus pulposus (NP) cells and accelerated surrounding extracellular matrix catabolism. Bioactive hydrogels have shown significant potential in regulating cellular functions and tissue homeostasis. In this work, a dynamic hydrogel (HA-NCSN/Cu) is designed via the reductive chelation of hyaluronic acid grafted with thiourea (HA-NCSN) and Cu2+. The reductivity of the grafted thiourea groups of HA-NCSN can quickly reduce part of the chelated Cu2+ to Cu+. Therefore, during the gelation process, the color of hydrogel become dark immediately, which endowed hydrogel with remarkable photothermal effect. The abundant thiourea groups inside hydrogel can effectively scavenge reactive oxygen species to mitigate the inflammatory stress of NP cells. RNA sequencing analysis further reveals that glutathione signaling pathway is significantly altered. Meanwhile, mild photothermal therapy could activate the TGF-β/Smad pathway in NP cells, promoting the expression and secretion of Aggrecan and Collagen II. Ultimately, the combined modulation of inflammation alleviation and matrix regeneration achieves the restoration of the structure and function of the damaged intervertebral disc, which is also strongly demonstrated by the in vivo animal experiments. All of these results demonstrate the great potential of the dynamic HA-NCSN/Cu hydrogel in IVDD treatment.

Application of Self-Healing Hydrogels in the Treatment of Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is one of the leading causes of chronic pain and disability, and traditional treatment methods often struggle to restore its complex biomechanical properties. This article explores the innovative application of self-healing hydrogels in the treatment of IDD, offering new hope for disc repair due to their exceptional self-repair capabilities and adaptability. As a key support structure in the human body, intervertebral discs are often damaged by trauma or degenerative changes. Self-healing hydrogels not only mimic the mechanical properties of natural intervertebral discs but also self-repair when damaged, thereby maintaining stable functionality. This article reviews the self-healing mechanisms and design strategies of self-healing hydrogels and, for the first time, outlines their potential in the treatment of IDD. Furthermore, the article looks forward to future developments in the field, including intelligent material design, multifunctional integration, encapsulation and release of bioactive molecules, and innovative combinations with tissue engineering and stem cell therapy, offering new perspectives and strategies for IDD treatment.

Progress in the Application of Multifunctional Composite Hydrogels in Promoting Tissue Repair

Tissue repair is an extremely complex process, and effectively promoting tissue regeneration remains a significant clinical challenge. Hydrogel materials, which exhibit physical properties closely resembling those of living tissues, including high water content, oxygen permeability, and softness, have the potential to revolutionize the field of tissue repair. However, the presence of various complex conditions, such as infection, ischemia, and hypoxia in tissue defects, means that hydrogels with simple structures and functions are often insufficient to meet the diverse needs of tissue repair. Researchers have focused on integrating multiple drugs, nanomaterials, bioactive substances, and stem cells into hydrogel matrices to develop novel multifunctional composite hydrogels for addressing these challenges, which have superior antibacterial properties, hemostatic abilities, self-healing capacities, and excellent mechanical properties. These composite hydrogels are designed to enhance tissue repair and have become an important direction in the current research. This review provides a comprehensive review of the recent advances in the application of multifunctional composite hydrogels in promoting tissue repair, including drug-loaded hydrogels, nanomaterial composite hydrogels, bioactive substance composite hydrogels, and stem cell composite hydrogels.

Microenvironment-responsive metal-phenolic network release platform with ROS scavenging, anti-pyroptosis, and ECM regeneration for intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) can be caused by aging, injury, and genetic factors. The pathological changes associated with IVDD include the excessive accumulation of reactive oxygen species (ROS), cellular pyroptosis, and extracellular matrix (ECM) degradation. There are currently no approved specific molecular therapies for IVDD. In this study, we developed a multifunctional and microenvironment-responsive metal-phenolic network release platform, termed TMP@Alg-PBA/PVA, which could treat (IL-1β)-induced IVDD. The metal-phenolic network (TA-Mn-PVP, TMP) released from this platform targeted mitochondria to efficiently scavenge ROS and reduce ECM degradation. Pyroptosis was suppressed through the inhibition of the IL-17/ERK signaling pathway. These findings demonstrate the versatility of the platform. And in a rat model of IVDD, TMP@Alg-PBA/PVA exhibited excellent therapeutic effects by reducing the progression of the disease. TMP@Alg-PBA/PVA, therefore, presents clinical potential for the treatment of IVDD.

Melatonin/Sericin Wound Healing Patches: Implications for Melanoma Therapy

Melatonin and sericin exhibit antioxidant properties and may be useful in topical wound healing patches by maintaining redox balance, cell integrity, and regulating the inflammatory response. In human skin, melatonin suppresses damage caused by ultraviolet radiation (UVR) which involves numerous mechanisms associated with reactive oxygen species/reactive nitrogen species (ROS/RNS) generation and enhancing apoptosis. Sericin is a protein mainly composed of glycine, serine, aspartic acid, and threonine amino acids removed from the silkworm cocoon (particularly Bombyx mori and other species). It is of interest because of its biodegradability, anti-oxidative, and anti-bacterial properties. Sericin inhibits tyrosinase activity and promotes cell proliferation that can be supportive and useful in melanoma treatment. In recent years, wound healing patches containing sericin and melatonin individually have attracted significant attention by the scientific community. In this review, we summarize the state of innovation of such patches during 2021-2023. To date, melatonin/sericin-polymer patches for application in post-operational wound healing treatment has been only sparingly investigated and it is an imperative to consider these materials as a promising approach targeting for skin tissue engineering or regenerative dermatology.