Tannic Acid-Modified Decellularized Tendon Scaffold with Antioxidant and Anti-Inflammatory Activities for Tendon Regeneration

Loading tea polyphenols enhances the repair of human umbilical cord mesenchymal stem cell sheet after spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a devastating central nervous system disorder that remains a global health challenge. SCI-induced oxidative stress in the postinjury microenvironment limits tissue repair by provoking the excessive production of reactive oxygen species (ROS). Tea polyphenols (TP), as a natural plant polyphenol, could effectively reduce ROS. In recent years, stem cell-based therapy combined with cell sheet technology has been widely used in the treatment of SCI. Therefore, we constructed human umbilical cord mesenchymal stem cell sheet loaded with TP (CS-TP) and evaluated their therapeutic effects and mechanisms both in vitro and in vivo in SCI rats.

METHODS

Human umbilical cord mesenchymal stem cell sheet (CS) were prepared by temperature-responsive cell culture method and successfully loaded with TP. The protective effect of CS and CS-TP on cells against oxidative stress was tested by Live/Dead cell staining and CCK-8 assay. CS and CS-TP were co-cultured with PC12 cells and human umbilical vein endothelial cells (HUVECs), respectively, and their effects on reducing ROS production were evaluated using flow cytometry and ROS fluorescence assays. Immune fluorescence (IF) and Western blot analysis of the mechanism by which CS-TP affects PC12 cells and HUVECs in vitro. Wound healing assay, transwell Chamber invasion experiment and tube formation assay were performed to evaluate the effects of CS and CS-TP on the biological behaviors of HUVECs. (Basso-Beattie-Bresnahan) BBB scores and gait analysis were performed to assess the recovery of motor function in rats. Molecular modeling is used to study the affinity between the main active ingredient epigallocatechin gallate (EGCG) in TP and target proteins. Western blot analyzes the mechanism of action of CS and CS-TP in SCI animals and the expression levels of antioxidant proteins. Tissue IF staining was used to evaluate angiogenesis, neuron regeneration and axonal extension.

RESULTS

Compared with CS, CS-TP could effectively reduce cellular ROS production and increase cell viability under high oxidative stress conditions and significantly enhance its biological activity. In vitro, CS-TP can significantly activate the Keap-1/Nrf2/HO-1 pathway, thereby affecting PC12 cells and HUVECs. After transplantation in SCI rats, CS-TP also activates the Keap-1/Nrf2/HO-1 pathway, influencing the repair of SCI and upregulating the expression of SOD1 and SOD2. CS-TP can more effectively promote angiogenesis, neuronal regeneration, and axonal extension in injured spinal cords, greatly improving the motor function of the rats.

CONCLUSION

CS-TP not only significantly enhances the resistance of CS to ROS, activates the Keap-1/Nrf2/HO-1 pathway, and regulates the level of antioxidant proteins in the body. Compared to CS, it can also more effectively increase the number of new blood vessels, promote neuron regeneration and axon extension, thereby more effectively repairing SCI.

Reactive oxygen species in tendon injury and repair

Reactive oxygen species (ROS) are chemical moieties that in physiological concentrations serve as fast-acting signaling molecules important for cellular homeostasis. However, their excess either due to overproduction or inability of the antioxidant system to inactivate them results in oxidative stress, contributing to cellular dysfunction and tissue damage. In tendons, which are hypovascular, hypocellular, and composed predominantly of extracellular matrix (ECM), particularly collagen I, ROS likely play a dual role: regulating cellular processes such as inflammation, proliferation, and ECM remodeling under physiological conditions, while contributing to tendinopathy and impaired healing when dysregulated. This review explores the sources of ROS in tendons, including NADPH oxidases and mitochondria, and their role in key processes such as tissue adaptation to mechanical load and injury repair, also in systemic conditions such as diabetes. In addition, we integrate the emerging perspective that calcium signaling-mediated by mechanically activated ion channels-plays a central role in tendon mechanotransduction under daily mechanical loads. We propose that mechanical overuse (overload) may lead to hyperactivation of calcium channels, resulting in chronically elevated intracellular calcium levels that amplify ROS production and oxidative stress. Although direct evidence linking calcium channel hyperactivity, intracellular calcium dysregulation, and ROS generation under overload conditions is currently circumstantial, this review aims to highlight these connections and identify them as critical avenues for future research. By framing ROS within the context of both adaptive and maladaptive responses to mechanical load, this review provides a comprehensive synthesis of redox biology in tendon injury and repair, paving the way for future work, including development of therapeutic strategies targeting ROS and calcium signaling to enhance tendon recovery and resilience.

Methacrylated silk fibroin based composite hydrogel with ROS-scavenging and osteogenic ability to orchestrate diabetic bone regeneration

The repair of diabetic bone defects is still filled with enormous challenges. Excessive reactive oxygen species (ROS) are regenerated in diabetic bone defect sites which is harmful to bone regeneration. Therefore, it's to a good strategy to scavenge the excess ROS to provide a friendly environment for diabetic bone defects repair. Herein, a novel composite hydrogel with ROS-scavenging and osteogenic ability is constructed. This methacrylated silk fibroin based composite hydrogel is capable of releasing tannin acid and inorganic ion, which can reduce oxidative stress, restore homeostasis and enhance osteogenesis. In vitro results indicated that the composite hydrogel could promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) under oxidative stress condition. Furthermore, in vivo results suggested that it can significantly promote bone regeneration in diabetic bone defects. In conclusion, this study provides critical insight into the biological mechanism and potential therapy for diabetic bone regeneration.

An antibacterial, antioxidant and hemostatic hydrogel accelerates infectious wound healing

Hydrogel drug-delivery system that can effectively load antibacterial drugs, realize the in-situ drug release in the microenvironment of wound infection to promote wound healing. In this study, a multifunctional hydrogel drug delivery system (HA@TA-Okra) was constructed through the integration of hyaluronic acid methacrylate (HAMA) matrix with tannic acid (TA) and okra extract. The composition and structural characteristics of HA@TA-Okra system and its unique advantages in the treatment of diverse wounds were systematically evaluated. TA, due to its unique chemical structure, is able to anchor within the HAMA network through interactions and cross-linking, conferring exceptional mechanical strength and stability to the hydrogel. Both TA and okra extract possess antioxidant and antibacterial properties, and when they two acts synergistically they can effectively scavenge free radicals, enhance antibacterial action, diminishing the risk of wound infection. In vitro experiments revealed that HA@TA-Okra system has superior properties, such as rapid gel response, remarkable swelling regulation, and potent antioxidant ability. Furthermore, the HA@TA-Okra system significantly outperformed conventional dressings in terms of hemostatic performance in a rat hemorrhage model. We further evaluated the repair role of HA@TA-Okra system in vivo by establishing an animal model of full-thickness skin defects and a model of infected total skin defects. The results confirmed its positive effects in fighting bacterial infection, reducing inflammation and promoting wound healing. In summary, the HA@TA-Okra system exhibits comprehensive properties such as antibacterial, antioxidant and hemostatic properties, which has a potential application in the field of tissue repair medicine.

Smart hydrogel-based trends in future tendon injury repair: A review

Despite advances in tissue engineering for tendon repair, rapid functional repair is still challenging due to its specificity and is prone to complications such as postoperative infections and tendon adhesions. Smart responsive hydrogels provide new ideas for tendon therapy with their flexibly designed three-dimensional cross-linked polymer networks that respond to specific stimuli. In recent years, a variety of smart-responsive hydrogels have been developed for the treatment of tendon disorders, showing great research promise and ability to address complex challenges. This article provides a comprehensive review of recent advances in the field of smart-responsive hydrogels for the treatment of tendon disorders, with a special focus on their response properties to different physical, chemical and biological stimuli. The multiple functional properties of these innovative materials are discussed in depth, including excellent biocompatibility and biodegradability, excellent mechanical properties, biomimetic structural design, convenient injectability, and unique self-healing capabilities. These properties enable the smart-responsive hydrogels to demonstrate significant advantages in solving difficult problems in the treatment of tendon disorders, such as precise drug delivery, tendon adhesion prevention and postoperative infection control. In addition, the article looks at the future prospects of smart-responsive hydrogels and analyses the challenges they may face in achieving widespread application.

Biomimetic Nanomodulator Regulates Oxidative and Inflammatory Stresses to Treat Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) is a devastating complication of sepsis, affecting approximately 70% of patients with sepsis in intensive care units (ICU). Although the pathophysiological mechanisms remain elusive, sepsis is typically accompanied by systemic inflammatory response syndrome (SIRS) and hyper-oxidative conditions. Here, we introduce a biomimetic nanomodulator (mAOI NP) that specifically targets inflammation site and simultaneously regulates oxidative and inflammatory stresses. mAOI NPs are constructed using metal-coordinated polyphenolic antioxidants (tannic acid) and flavonoid quercetin, which are then coated with macrophage membrane to enhance pharmacokinetics and enable SAE targeting. In a cecal ligation and puncture (CLP)-induced severe sepsis model, mAOI NPs effectively mitigate oxidative stress by purging reactive oxygen species, repairing mitochondrial damage and activating the Nrf2/HO-1 signaling pathway; while polarizing M1 macrophages or microglia toward anti-inflammatory M2 subtype. mAOI NPs potently inhibit sepsis progress, prolong overall survival from 25 to 66% and enhance learning and memory capabilities in SAE mice. Further proteomics analysis reveals that mAOI NPs modulate neurodevelopment processes related to learning and memory formation while also exerting anti-inflammatory and antioxidative effects on brain tissue responses associated with SAE pathology. This study offers significant potential for improving patient outcomes and revolutionizing the treatment landscape for this devastating complication of sepsis.

Short-term cryoprotectant-free cryopreservation at -20°C does not affect the viability and regenerative capacity of nanofat

Nanofat is an autologous fat derivative with high regenerative activity, which is usually administered immediately after its generation by mechanical emulsification of adipose tissue. For its potential repeated use over longer time, we herein tested whether cryopreservation of nanofat is feasible. For this purpose, the inguinal fat pads of donor mice were processed to nanofat, which was i) frozen and stored in a freezer at -20°C, ii) shock frozen in liquid nitrogen with subsequent storage at -80°C or iii) gradually frozen and stored at -80°C. After 7 days, the cryopreserved nanofat samples were thawed and immunohistochemically compared with freshly generated nanofat (control). Nanofat frozen and stored at -20°C exhibited the lowest apoptotic rate and highest densities of blood and lymph vessels, which were comparable to those of control. Accordingly, nanofat cryopreserved at -20°C or control nanofat were subsequently fixed with platelet-rich plasma in full-thickness skin defects within dorsal skinfold chambers of recipient mice to assess vascularization, formation of granulation tissue and wound closure by means of stereomicroscopy, intravital fluorescence microscopy, histology and immunohistochemistry over 14 days. These analyses revealed no marked differences between the healing capacity of wounds filled with cryopreserved or control nanofat. Therefore, it can be concluded that cryopreservation of nanofat is simply feasible without affecting its viability and regenerative potential. This may broaden the range of future nanofat applications, which would particularly benefit from repeated administration of this autologous biological product.