Construction of a NT-3 sustained-release system cross-linked with an acellular spinal cord scaffold and its effects on differentiation of cultured bone marrow mesenchymal stem cells

Neurological recovery and neurogenesis by curcumin sustained-release system cross-linked with an acellular spinal cord scaffold in rat spinal cord injury: Targeting NLRP3 inflammasome pathway

In the context of treating spinal cord injury (SCI), the modulation of inflammatory responses, and the creation of a suitable region for tissue regeneration may present a promising approach. This study aimed to evaluate the effects of curcumin (Cur)-loaded bovine serum albumin nanoparticles (Cur-BSA NPs) cross-linked with an acellular spinal cord scaffold (ASCS) on the functional recovery in a rat model of SCI. We developed an ASCS using chemical and physical methods. Cur-BSA, and blank (B-BSA) NPs were fabricated and cross-linked with ASCS via EDC-NHS, resulting in the production of Cur-ASCS and B-ASCS. We assessed the properties of scaffolds and NPs as well as their cross-links. Finally, using a male rat hemisection model of SCI, we investigated the consequences of the resulting scaffolds. The inflammatory markers, neuroregeneration, and functional recovery were evaluated. Our results showed that Cur was efficiently entrapped at the rate of 42% ± 1.3 in the NPs. Compared to B-ASCS, Cur-ASCS showed greater effectiveness in the promotion of motor recovery. The implantation of both scaffolds could increase the migration of neural stem cells (Nestin- and GFAP-positive cells) following SCI with the superiority of Cur-ASCS. Cur-ASCS was successful to regulate the gene expression and protein levels of NLRP3, ASC, and Casp1in the spinal cord lesion. Our results indicate that using ASCS can lead to the entrance of cells into the scaffold and promote neurogenesis. However, Cur-ASCS had greater effects in terms of inflammation relief and enhanced neurogenesis.

Biomedical Application of Decellularized Scaffolds

Tissue loss and end-stage organ failure are serious health problems across the world. Natural and synthetic polymer scaffold material based artificial organs play an important role in the field of tissue engineering and organ regeneration, but they are not from the body and may cause side effects such as rejection. In recent years, the biomimetic decellularized scaffold based materials have drawn great attention in the tissue engineering field for their good biocompatibility, easy modification, and excellent organism adaptability. Therefore, in this review, we comprehensively summarize the application of decellularized scaffolds in tissue engineering and biomedicine in recent years. The preparation methods, modification strategies, construction of artificial tissues, and application in biomedical applications are discussed. We hope that this review will provide a useful reference for research on decellularized scaffolds and promote their application tissue engineering.

Current Status and Progress in Stem Cell Therapy for Intracerebral Hemorrhage

Intracerebral hemorrhage is a highly prevalent and prognostically poor disease, imposing immeasurable harm on human life and health. However, the treatment options for intracerebral hemorrhage are severely limited, particularly in terms of improving the microenvironment of the lesion, promoting neuronal cell survival, and enhancing neural function. This review comprehensively discussed the application of stem cell therapy for intracerebral hemorrhage, providing a systematic summary of its developmental history, types of transplants, transplantation routes, and transplantation timing. Moreover, this review presented the latest research progress in enhancing the efficacy of stem cell transplantation, including pretransplantation preconditioning, genetic modification, combined therapy, and other diverse strategies. Furthermore, this review pioneeringly elaborated on the barriers to clinical translation for stem cell therapy. These discussions were of significant importance for promoting stem cell therapy for intracerebral hemorrhage, facilitating its clinical translation, and improving patient prognosis.

Decellularized extracellular matrix in the treatment of spinal cord injury

Functional limitation caused by spinal cord injury (SCI) has the problem of significant clinical and economic burden. Damaged spinal axonal connections and an inhibitory environment severely hamper neuronal function. Regenerative biomaterials can fill the cavity and produce an optimal microenvironment at the site of SCI, inhibiting apoptosis, inflammation, and glial scar formation while promoting neurogenesis, axonal development, and angiogenesis. Decellularization aims to eliminate cells from the ultrastructure of tissues while keeping tissue-specific components that are similar to the structure of real tissues, making decellularized extracellular matrix (dECM) a suitable scaffold for tissue engineering. dECM has good biocompatibility, it can be widely obtained from natural organs of different species, and can be co-cultured with cells for 3D printing to obtain the target scaffold. In this paper, we reviewed the pathophysiology of SCI, the characteristics of dECM and its preparation method, and the application of dECM in the treatment of SCI. Although dECM has shown its therapeutic effect at present, there are still many indicators that need to be taken into account, such as the difficulty in obtaining materials and standardized production mode for large-scale use, the effect of decellularization on the physical and chemical properties of dECM, and the study on the synergistic effect of dECM and cells.

Preparation of Cross-Linked Bovine Tendon Acellular Fibers and Study of Their Biophysical and Chemical Properties

To explore the effect of glutaraldehyde (GA) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) cross-linking on the biophysical and chemical properties of acellular scaffold to better provide suitable donor materials for tendon reconstruction. GA and EDC with different concentrations and action time gradients were used to cross-link the acellular scaffold. By detecting the collagen content in the cross-linked scaffold and the cytotoxicity, the cross-linking scheme with minimal damage to the scaffold and minimal cytotoxicity was explored for subsequent studies. The biomechanical properties (durability, elastic modulus, stressmax) of the scaffolds in GA, EDC, acellular scaffold, and tendon groups were compared, and the scaffold rat models were constructed to further evaluate their in vivo histocompatibility. Under different concentration gradients, the collagen content of the scaffolds in the GA and EDC groups had no obvious difference. When 0.5% GA was cross-linked for 24 h, and the mass ratio of EDC (1:2) was cross-linked for 4 h, the inhibition rate of the scaffold extract on fibroblasts was the lowest. In the mechanical property test, the Stressmax, durability, and elastic modulus of the cross-linked acellular scaffolds were significantly improved than those before cross-linking, and the elastic modulus of the EDC acellular scaffold was similar to that of the bovine tendon. In the compatibility test, compared with the acellular scaffold group, fibroblast activity in the GA group decreased obviously, and the scaffold implanted in rat models led to a persistent chronic inflammatory reaction. However, cells in the EDC group could maintain good activity. Moreover, the scaffold had good compatibility with rats and did not cause an obvious inflammatory reaction. EDC cross-linking scheme will not damage the acellular scaffold, and the cytotoxicity of the obtained scaffold is controllable. Additionally, EDC cross-linked acellular scaffold has mechanical properties similar to normal tendons and excellent histocompatibility.

Construction of a decellularized spinal cord matrix/GelMA composite scaffold and its effects on neuronal differentiation of neural stem cells

Spinal cord injury (SCI) leads to severe loss of motor and sensory functions, and the rehabilitation of SCI is a worldwide problem. Tissue-engineered scaffolds offer new hope for SCI patients, while the newly developed materials encountered a challenge in modeling the microenvironment around the lesion site. We constructed a new composite scaffold by mixing decellularized spinal cord extracellular matrix (dECM) with gelatin methacryloyl (GelMA). The dECM, as a natural biological material, retained a large number of proteins and growth factors related to neurogenesis. GelMA was a photopolymerizable material, harbored a polymer network structure, soft texture, certain shape and plenty of water. The viability, proliferation, and differentiation of neural stem cells (NSCs) on the composite scaffold were evaluated by cell count kit-8 (CCK8), Live/Dead assay, phalloidin staining, 5-Ethynyl-2'-deoxyurdine (EdU), immunofluorescence staining and western blot. The Live/Dead assay, phalloidin staining, EdU, and CCK8 assay showed that the composite scaffold had good biocompatibility and provided better support for proliferation of NSCs. Results of immunocytochemistry and western blot showed that the composite scaffolds promoted the specific differentiation of NSCs into neuron cells. Together, this dECM/GelMA composite scaffold can be used as a cell culture coating, the isolated NSCs seeded on the surface of composite scaffold expressed neuronal markers and assumed neuronal morphology. Our work provided a new method that would be widely used in tissue engineering of SCI.

Decellularization alters the unfavorable regenerative adverse microenvironment of the injured spinal cord to support neurite outgrowth

Background

Acellular tissue has been transplanted into the injury site as an external microenvironment to intervene with imbalance microenvironment that occurs after spinal cord injury (SCI) and stimulating axonal regeneration, although the mechanism is unclear. Given decellularization is the key means to obtain acellular tissues, we speculated changes in the internal components of tissue caused by decellularization may be the key reason why acellular tissues affect remodeling of the microenvironment.

Methods

Complete spinal cord crush in a mouse model was established, and the dynamic of extracellular matrix (ECM) expression and distribution during SCI was studied with immunohistochemistry (IHC). Normal spinal cord (NSC) and 14-day injury spinal cord (ISC) were obtained to prepare the decellularized NSC (DNSC) and decellularized ISC (DISC) through a well-designed decellularization method, and the decellularization effects were evaluated by residual DNA content determination, hematoxylin and eosin staining (H&E), and IHC. Rat dorsal root ganglia (DRG) were co-cultured with NSC, ISC, DNSC, and DISC to evaluate their effect on neurite outgrowth. Furthermore, the mechanisms by which decellularized tissue promotes axonal growth were explored with proteomics analysis of the protein components and function of 14-day ISC and DISC.

Results

We found the expression of the four main ECM components (collagen type I and IV, fibronectin, and laminin) gradually increased with the progression of SCI compared to NSC, peaking at 14 days of injury then slightly decreasing at 21 days, and the distribution of the four ECM proteins in the ISC also changed dynamically. H&E staining, residual DNA content determination, and IHC showed decellularization removed cellular components and preserved an intact ECM. The results of co-cultured DRG with NSCs, ISCs, DNSCs, and DISCs showed DNSCs and DISCs had a stronger ability in supporting neurite outgrowth than NSC and ISC. We found through proteomics that decellularization could remove proteins associated with inflammatory responses, scarring, and other pathological factors, while completely retaining the ECM proteins.

Conclusions

Taken together, our findings demonstrate decellularization can optimize the imbalanced microenvironment after SCI by removing components that inhibit spinal cord regeneration, providing a theoretical basis for clinical application of acellular tissue transplantation to repair SCI.

Decellularised extracellular matrix-based biomaterials for repair and regeneration of central nervous system

The central nervous system (CNS), consisting of the brain and spinal cord, regulates the mind and functions of the organs. CNS diseases, leading to changes in neurological functions in corresponding sites and causing long-term disability, represent one of the major public health issues with significant clinical and economic burdens worldwide. In particular, the abnormal changes in the extracellular matrix under various disease conditions have been demonstrated as one of the main factors that can alter normal cell function and reduce the neuroregeneration potential in damaged tissue. Decellularised extracellular matrix (dECM)-based biomaterials have been recently utilised for CNS applications, closely mimicking the native tissue. dECM retains tissue-specific components, including proteoglycan as well as structural and functional proteins. Due to their unique composition, these biomaterials can stimulate sensitive repair mechanisms associated with CNS damages. Herein, we discuss the decellularisation of the brain and spinal cord as well as recellularisation of acellular matrix and the recent progress in the utilisation of brain and spinal cord dECM.

Decellularized optic nerve functional scaffold transplant facilitates directional axon regeneration and remyelination in the injured white matter of the rat spinal cord

Axon regeneration and remyelination of the damaged region is the most common repair strategy for spinal cord injury. However, achieving good outcome remains difficult. Our previous study showed that porcine decellularized optic nerve better mimics the extracellular matrix of the embryonic porcine optic nerve and promotes the directional growth of dorsal root ganglion neurites. However, it has not been reported whether this material promotes axonal regeneration in vivo. In the present study, a porcine decellularized optic nerve was seeded with neurotrophin-3-overexpressing Schwann cells. This functional scaffold promoted the directional growth and remyelination of regenerating axons. In vitro, the porcine decellularized optic nerve contained many straight, longitudinal channels with a uniform distribution, and microscopic pores were present in the channel wall. The spatial micro topological structure and extracellular matrix were conducive to the adhesion, survival and migration of neural stem cells. The scaffold promoted the directional growth of dorsal root ganglion neurites, and showed strong potential for myelin regeneration. Furthermore, we transplanted the porcine decellularized optic nerve containing neurotrophin-3-overexpressing Schwann cells in a rat model of T10 spinal cord defect in vivo. Four weeks later, the regenerating axons grew straight, the myelin sheath in the injured/transplanted area recovered its structure, and simultaneously, the number of inflammatory cells and the expression of chondroitin sulfate proteoglycans were reduced. Together, these findings suggest that porcine decellularized optic nerve loaded with Schwann cells overexpressing neurotrophin-3 promotes the directional growth of regenerating spinal cord axons as well as myelin regeneration. All procedures involving animals were conducted in accordance with the ethical standards of the Institutional Animal Care and Use Committee of Sun Yat-sen University (approval No. SYSU-IACUC-2019-B034) on February 28, 2019.

Status of Plant Protein-Based Green Scaffolds for Regenerative Medicine Applications

In recent decades, regenerative medicine has merited substantial attention from scientific and research communities. One of the essential requirements for this new strategy in medicine is the production of biocompatible and biodegradable scaffolds with desirable geometric structures and mechanical properties. Despite such promise, it appears that regenerative medicine is the last field to embrace green, or environmentally-friendly, processes, as many traditional tissue engineering materials employ toxic solvents and polymers that are clearly not environmentally friendly. Scaffolds fabricated from plant proteins (for example, zein, soy protein, and wheat gluten), possess proper mechanical properties, remarkable biocompatibility and aqueous stability which make them appropriate green biomaterials for regenerative medicine applications. The use of plant-derived proteins in regenerative medicine has been especially inspired by green medicine, which is the use of environmentally friendly materials in medicine. In the current review paper, the literature is reviewed and summarized for the applicability of plant proteins as biopolymer materials for several green regenerative medicine and tissue engineering applications.