A Promising Application of Injectable Hydrogels in Nerve Repair and Regeneration for Ischemic Stroke

Hydrogels for Peripheral Nerve Repair: Emerging Materials and Therapeutic Applications

Peripheral nerve injuries pose a significant clinical challenge due to the complex biological processes involved in nerve repair and their limited regenerative capacity. Despite advances in surgical techniques, conventional treatments, such as nerve autografts, are faced with limitations like donor site morbidity and inconsistent functional outcomes. As such, there is a growing interest in new, novel, and innovative strategies to enhance nerve regeneration. Tissue engineering/regenerative medicine and its use of biomaterials is an emerging example of an innovative strategy. Within the realm of tissue engineering, functionalized hydrogels have gained considerable attention due to their ability to mimic the extracellular matrix, support cell growth and differentiation, and even deliver bioactive molecules that can promote nerve repair. These hydrogels can be engineered to incorporate growth factors, bioactive peptides, and stem cells, creating a conducive microenvironment for cellular growth and axonal regeneration. Recent advancements in materials as well as cell biology have led to the development of sophisticated hydrogel systems, that not only provide structural support, but also actively modulate inflammation, promote cell recruitment, and stimulate neurogenesis. This review explores the potential of functionalized hydrogels for peripheral nerve repair, highlighting their composition, biofunctionalization, and mechanisms of action. A comprehensive analysis of preclinical studies provides insights into the efficacy of these hydrogels in promoting axonal growth, neuronal survival, nerve regeneration, and, ultimately, functional recovery. Thus, this review aims to illuminate the promise of functionalized hydrogels as a transformative tool in the field of peripheral nerve regeneration, bridging the gap between biological complexity and clinical feasibility.

Ellagic acid alleviates NLRP6/caspase-1/GSDMD-mediated inflammation and pyroptosis in rats post cerebral ischemia/reperfusion injury

Objectives

Ellagic acid (EA) is a natural polyphenol with anti-cancer, anti-oxidant, anti-inflammatory, antibacterial, and other effects. However, the role of EA in cerebral ischemia/reperfusion injury (CIRI) remains unclear. This study aims to investigate the neuroprotective effects of EA in CIRI.

Materials and Methods

Forty male Wistar rats (260-300 g) were randomly divided into four groups with 10 rats per group: 1) Sham+Veh: Rats underwent I/R surgery, except that they were not inserted with thread plugs, and received solute treatment at the same time. 2) MCAO/R+Veh. 3) MCAO/R+EA: Rats were administered 200 mg/kg EA before undergoing MCAO. 4) MCAO/R+Nim: Rats were administered Nim before undergoing MCAO.

Results

Cerebral MCAO/R damaged brain tissue, elevated neurological deficit score (P<0.01), cerebral infarction volume (P<0.01), inflammatory cell infiltration (P<0.01), NLRP6, ASC, caspase-1 and GSDMD mRNA level (P<0.01 and P<0.001), NLRP6, caspase-1, GSDMD-N and IL-1β protein level (P<0.01 and P<0.001), and inflammatory cytokines in brain tissue (P<0.01). Prophylactic administration of EA also significantly improved brain tissue damage, reduced neurological deficit score (P<0.01), cerebral infarction volume (P<0.01), inflammatory cell number (P<0.05), NLRP6, caspase-1, GSDMD-N mRNA and protein level (P<0.05 and P<0.01), ASC mRNA level and IL-1β protein level (P<0.01), and IL-1β and IL-18 level in brain tissue (P<0.01) compared to positive control.

Conclusion

EA may serve as a potential drug for the treatment of brain I/R, which may exert an anti-inflammatory effect by inhibiting the activation of the inflammasome.

Hydrogel-Based Therapies for Ischemic and Hemorrhagic Stroke: A Comprehensive Review

Stroke remains the second leading cause of death and a major cause of disability worldwide, significantly impacting individuals, families, and healthcare systems. This neurological emergency can be triggered by ischemic events, including small vessel arteriolosclerosis, cardioembolism, and large artery atherothromboembolism, as well as hemorrhagic incidents resulting from macrovascular lesions, venous sinus thrombosis, or vascular malformations, leading to significant neuronal damage. The resultant motor impairment, cognitive dysfunction, and emotional disturbances underscore the urgent need for effective therapeutic interventions. Recent advancements in biomaterials, particularly hydrogels, offer promising new avenues for stroke management. Hydrogels, composed of three-dimensional networks of hydrophilic polymers, are notable for their ability to absorb and retain substantial amounts of water. Commonly used polymers in hydrogel formulations include natural polymers like alginate, chitosan, and collagen, as well as synthetic polymers such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylamide. Their customizable characteristics-such as their porosity, swelling behavior, mechanical strength, and degradation rates-make hydrogels ideal for biomedical applications, including drug delivery, cell delivery, tissue engineering, and the controlled release of therapeutic agents. This review comprehensively explores hydrogel-based approaches to both ischemic and hemorrhagic stroke therapy, elucidating the mechanisms by which hydrogels provide neuroprotection. It covers their application in drug delivery systems, their role in reducing inflammation and secondary injury, and their potential to support neurogenesis and angiogenesis. It also discusses current advancements in hydrogel technology and the significant challenges in translating these innovations from research into clinical practice. Additionally, it emphasizes the limited number of clinical trials utilizing hydrogel therapies for stroke and addresses the associated limitations and constraints, underscoring the need for further research in this field.

Hydrogels for Neural Regeneration: Exploring New Horizons

Nerve injury can significantly impair motor, sensory, and autonomic functions. Understanding nerve degeneration, particularly Wallerian degeneration, and the mechanisms of nerve regeneration is crucial for developing effective treatments. This manuscript reviews the use of advanced hydrogels that have been researched to enhance nerve regeneration. Hydrogels, due to their biocompatibility, tunable properties, and ability to create a supportive microenvironment, are being explored for their effectiveness in nerve repair. Various types of hydrogels, such as chitosan-, alginate-, collagen-, hyaluronic acid-, and peptide-based hydrogels, are discussed for their roles in promoting axonal growth, functional recovery, and myelination. Advanced formulations incorporating growth factors, bioactive molecules, and stem cells show significant promise in overcoming the limitations of traditional therapies. Despite these advancements, challenges in achieving robust and reliable nerve regeneration remain, necessitating ongoing research to optimize hydrogel-based interventions for neural regeneration.

Injectable Hydrogels for Nervous Tissue Repair-A Brief Review

The repair of nervous tissue is a critical research field in tissue engineering because of the degenerative process in the injured nervous system. In this review, we summarize the progress of injectable hydrogels using in vitro and in vivo studies for the regeneration and repair of nervous tissue. Traditional treatments have not been favorable for patients, as they are invasive and inefficient; therefore, injectable hydrogels are promising for the treatment of damaged tissue. This review will contribute to a better understanding of injectable hydrogels as potential scaffolds and drug delivery system for neural tissue engineering applications.