Intramuscular injection of skeletal muscle derived extracellular matrix mitigates denervation atrophy after sciatic nerve transection

Injectable skeletal muscle constructs overexpressing GLUT4 for type 2 diabetes intervention

Skeletal muscle tissue engineering aims to repair tissue defects caused by injury, cancer, metabolic or neuromuscular disease. The need for invasive implantation techniques often limits the implantation of large tissue constructs or repeated treatments. Recent studies have reported on the development of injectable scaffolds for tissue engineering; however, fabrication of skeletal muscle tissue is particularly challenging due to the large size of human myotubes and the required mechanical properties. This work developed a collagen-based shape-memory scaffold supportive of skeletal muscle tissue growth and differentiation in vitro and maintained shape post-injection in vivo. The injectable engineered muscle construct was intramuscularly delivered via a syringe needle and integrated successfully with the native muscle tissue. We demonstrated the system's potential on a Type 2 diabetes mouse model. A prominent early sign of type 2 diabetes is the reduction in GLUT4 expression and translocation in skeletal muscle; therefore, based on a previous work published by our group, we created injectable GLUT4-overexpressing muscle constructs. Following injection, GLUT4 overexpressing skeletal muscle tissue retained its shape-memory properties and viability and improved glucose homeostasis in the diabetic mice. This work demonstrated successful minimally invasive delivery of engineered muscle tissue and potential treatment for chronic muscle-related conditions. STATEMENT OF SIGNIFICANCE: Type 2 diabetes is a widespread metabolic disorder characterized by insulin resistance and impaired glucose regulation. This study offers a minimally invasive approach to treatment through the development of an injectable skeletal muscle construct overexpressing GLUT4 to improve glucose homeostasis. Unlike traditional surgical methods, this minimally invasive system employs a collagen-based scaffold with shape-memory properties, enabling effective tissue delivery and integration. Existing therapies are limited in addressing chronic metabolic disorders that require repeated interventions. Our work fills that gap by enhancing muscle function and glucose regulation. The scaffold's unique ability to retain its structure post-injection and support muscle differentiation presents a significant advancement with broad implications for treating metabolic diseases and advancing regenerative medicine.

Magnetic fibrin nanofiber hydrogel delivering iron oxide magnetic nanoparticles promotes peripheral nerve regeneration

Peripheral nerve injury is a debilitating condition that have a profound impact on the overall quality of an individual's life. The repair of peripheral nerve defects continues to present significant challenges in the field. Iron oxide magnetic nanoparticles (IONPs) have been recognized as potent nanotools for promoting the regeneration of peripheral nerves due to their capability as biological carriers and their ability to template the hydrogel structure under an external magnetic field. This research used a fibrin nanofiber hydrogel loaded with IONPs (IONPs/fibrin) to promote the regeneration of peripheral nerves in rats. In vitro examination of PC12 cells on various concentrations of IONPs/fibrin hydrogels revealed a remarkable increase in NGF and VEGF expression at 2% IONPs concentration. The biocompatibility and degradation of 2% IONPs/fibrin hydrogel were assessed using the in vivo imaging system, demonstrating subcutaneous degradation within a week without immediate inflammation. Bridging a 10-mm sciatic nerve gap in Sprague Dawley rats with 2% IONPs/fibrin hydrogel led to satisfactory morphological recovery of myelinated nerve fibers. And motor functional recovery in the 2% IONPs/fibrin group was comparable to autografts at 6, 9 and 12 weeks postoperatively. Hence, the composite fibrin hydrogel incorporating 2% IONPs exhibits potential for peripheral nerve regeneration.

dECM restores macrophage immune homeostasis and alleviates iron overload to promote DTPI healing

Due to its highly insidious and rapid progression, deep tissue pressure injury (DTPI) is a clinical challenge. Our previous study found that DTPI may be a skeletal muscle injury dominated by macrophage immune dysfunction due to excessive iron accumulation. Decellularized extracellular matrix (dECM) hydrogel promotes skeletal muscle injury repair. However, its role in polarizing macrophages and regulating iron metabolism in DTPI remains unclear. Here, porcine dECM hydrogel was prepared, and its therapeutic function and mechanism in repairing DTPI were investigated. The stimulus of dECM hydrogel toward RAW264.7 cells resulted in a significantly higher percentage of CD206+ macrophages and notably decreased intracellular divalent iron levels. In mice DTPI model, dECM hydrogel treatment promoted M1 to M2 macrophage conversion, improved iron metabolism and reduced oxidative stress in the early stage of DTPI. In the remodeling phase, the dECM hydrogel remarkably enhanced revascularization and accelerated skeletal muscle repair. Furthermore, the immunomodulation of dECM hydrogels in vivo was mainly involved in the P13k/Akt signaling pathway, as revealed by GO and KEGG pathway analysis, which may ameliorate the iron deposition and promote the healing of DTPI. Our findings indicate that dECM hydrogel is promising in skeletal muscle repair, inflammation resolution and tissue injury healing by effectively restoring macrophage immune homeostasis and normalizing iron metabolism.

Dynamic three-dimensional coculture model: The future of tissue engineering applied to the peripheral nervous system

Traumatic injuries to the peripheral nervous system (PNI) can lead to severe consequences such as paralysis. Unfortunately, current treatments rarely allow for satisfactory functional recovery. The high healthcare costs associated with PNS injuries, worker disability, and low patient satisfaction press for alternative solutions that surpass current standards. For the treatment of injuries with a deficit of less than 30 mm to bridge, the use of synthetic nerve conduits (NGC) is favored. However, to develop such promising therapeutic strategies, in vitro models that more faithfully mimic nerve physiology are needed. The absence of a clinically scaled model with essential elements such as a three-dimension environment and dynamic coculture has hindered progress in this field. The presented research focuses on the development of an in vitro coculture model of the peripheral nervous system (PNS) involving the use of functional biomaterial which microstructure replicates nerve topography. Initially, the behavior of neuron-derived cell lines (N) and Schwann cells (SC) in contact with a short section of biomaterial (5 mm) was studied. Subsequent investigations, using fluorescent markers and survival assays, demonstrated the synergistic effects of coculture. These optimized parameters were then applied to longer biomaterials (30 mm), equivalent to clinically used NGC. The results obtained demonstrated the possibility of maintaining an extended coculture of SC and N over a 7-day period on a clinically scaled biomaterial, observing some functionality. In the long term, the knowledge gained from this work will contribute to a better understanding of the PNS regeneration process and promote the development of future therapeutic approaches while reducing reliance on animal experimentation. This model can be used for drug screening and adapted for personalized medicine trials. Ultimately, this work fills a critical gap in current research, providing a transformative approach to study and advance treatments for PNS injuries.

Conducting polymer-based scaffolds for neuronal tissue engineering

Neuronal tissue engineering has immense potential for treating neurological disorders and facilitating nerve regeneration. Conducting polymers (CPs) have emerged as a promising class of materials owing to their unique electrical conductivity and biocompatibility. CPs, such as poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-hexylthiophene) (P3HT), polypyrrole (PPy), and polyaniline (PANi), have been extensively explored for their ability to provide electrical cues to neural cells. These polymers are widely used in various forms, including porous scaffolds, hydrogels, and nanofibers, and offer an ideal platform for promoting cell adhesion, differentiation, and axonal outgrowth. CP-based scaffolds can also serve as drug delivery systems, enabling localized and controlled release of neurotrophic factors and therapeutic agents to enhance neural regeneration and repair. CP-based scaffolds have demonstrated improved neural regeneration, both in vitro and in vivo, for treating spinal cord and peripheral nerve injuries. In this review, we discuss synthesis and scaffold processing methods for CPs and their applications in neuronal tissue regeneration. We focused on a detailed literature review of the central and peripheral nervous systems.