Nanofibrous scaffolds for the regeneration of nervous tissue

Introductons The biophysical organization of extracellular matrix (ECM) plays an important role in tissue morphogenesis,remodeling and functions. In many types of tissues,e. g. ,blood vessel,nerve,heart,muscle,tendon and ligament,ECM has aniso-

Aligned carbon nanotube containing scaffolds for neural tissue regeneration

Neuropathologies include the deterioration and damage of the nervous system,especially neurons present in the brain,spinal cord and peripheral nervous system.Damage or alternations in neurons makes their structure and functionality abnormal.Every year over 90,000 people get affected by neurodegenerative diseases in the USA.Among all the neurological pathologies,

Extracellular matrix from human umbilical cordderived mesenchymal stem cells as a scaffold for peripheral nerve regeneration

The extracellular matrix,which includes collagens,laminin,or fibronectin,plays an important role in peripheral nerve regeneration.Recently,a Schwann cell-derived extracellular matrix with classical biomaterial was used to mimic the neural niche.However,extensive clinical use of Schwann cells remains limited because of the limited origin,loss of an autologous nerve,and extended in vitro culture times.In the present study,human umbilical cord-derived mesenchymal stem cells（h UCMSCs）,which are easily accessible and more proliferative than Schwann cells,were used to prepare an extracellular matrix.We identified the morphology and function of h UCMSCs and investigated their effect on peripheral nerve regeneration.Compared with a non-coated dish tissue culture,the h UCMSC-derived extracellular matrix enhanced Schwann cell proliferation,upregulated gene and protein expression levels of brain-derived neurotrophic factor,glial cell-derived neurotrophic factor,and vascular endothelial growth factor in Schwann cells,and enhanced neurite outgrowth from dorsal root ganglion neurons.These findings suggest that the h UCMSC-derived extracellular matrix promotes peripheral nerve repair and can be used as a basis for the rational design of engineered neural niches.

Liver regeneration using decellularized splenic scaffold: a novel approach in tissue engineering

BACKGROUND： The potential application of decellularized liver scaffold for liver regeneration is limited by severe shortage of donor organs. Attempt of using heterograft scaffold is accompanied with high risks of zoonosis and immunological rejection. We proposed that the spleen, which procured more extensively than the liver, could be an ideal source of decellularized scaffold for liver regeneration. METHODS： After harvested from donor rat, the spleen was processed by 12-hour freezing/thawing ×2 cycles, then circulation perfusion of 0.02% trypsin and 3% Triton X-100 sequentially through the splenic artery for 32 hours in total to prepare decellularized scaffold. The structure and component characteristics of the scaffold were determined by hematoxylin and eosin and immumohistochemical staining, scanning electron microscope, DNA detection, porosity measurement, biocompatibility and cytocompatibility test. Recellularization of scaffold by 5×106 bone marrow mesenchymal stem cells（BMSCs） was carried out to preliminarily evaluate the feasibility of liver regeneration by BMSCs reseeding and differentiation in decellularized splenic scaffold.RESULTS： After decellularization, a translucent scaffold, which retained the gross shape of the spleen, was generated. Histological evaluation and residual DNA quantitation revealed the remaining of extracellular matrix without nucleus and cytoplasm residue. Immunohistochemical study proved the existence of collagens I, IV, fibronectin, laminin and elastin in decellularized splenic scaffold, which showed a similarity with decellularized liver. A scanning electron microscope presented the remaining three-dimensional porous structure of extracellular matrix and small blood vessels. The poros-ity of scaffold, aperture of 45.36±4.87 μm and pore rate of 80.14%±2.99% was suitable for cell engraftment. Subcutaneous implantation of decellularized scaffold presented good histocompatibility, and recellularization of the splenic scaffold demonstrated that BMSCs could locate and survive in the decellularized matrix. CONCLUSION： Considering the more extensive organ source and satisfying biocompatibility, the present study indicated that the three-dimensional decellularized splenic scaffold might have considerable potential for liver regeneration when combined with BMSCs reseeding and differentiation.

Fabrication and Evaluation of Porous Keratin/chitosan(KCS) Scaffolds for Effectively Accelerating Wound Healing

Objective To develop a dressing with desired antibacterial activity, good water maintaining ability and mechanical properties for wound healing and skin regeneration. Methods The chitosan with different concentrations were added in keratin solution to form porous keratin/chitosan（KCS） scaffolds. The morphological characteristics, chemical composition, wettability, porosity, swelling ratio and degradation of the scaffolds were evaluated. The antibacterial activity was tested by using S. aureus and E. coli suspension for 2 h. And L929 fibroblast cells culture was used to evaluate the cytotoxicity of the KCS scaffolds. Results The adding of chitosan could increase the hydrophobicity, decrease porosity, swelling ratio and degradation rate of the KCS porous scaffolds. Mechanical properties of KCS scaffolds could be enhanced and well adjusted by chitosan. KCS scaffolds could obviously decrease bacteria number. The proliferation of fibroblast cells in porous KCS patch increased firstly and then decreased with the increase of chitosan concentration. It was appropriate to add 400 μg/m L chitosan to form porous KCS scaffold for achieving best cell attachment and proliferation compared with other samples. Conclusion The porous KCS scaffold may be used as implanted scaffold materials for promoting wound healing and skin regeneration.

A substrate scaffold for assessment of nerve regeneration and neurodegenerative diseases

Neuroregenerafion is a complex topic in neurosci- ence and includes 3 concepts： neurogenesis, neuro- plasticity, and neurorestoration. After injury of the nervous system, axons have the capacity for self-re- pair, regrowth or proliferation. The peripheral ner- vous system is more effective at restoring damaged axons than the central nervous system （CNS）. This is because formation of scar tissue in the CNS in- fluences neural regrowth or synthesis of growth-in- hibiting proteins, thereby preventing reconstruction of a neural circuit （Silver and Miller, 2004; Enciu et al., 2011）. Parkinson＇s disease （PD） and Alzheimer＇s disease （AD） are two most common degenerative diseases of the CNS among the elderly.

Modifi cation of β-TCP/PLGA Scaffold and Its Effect on Bone Regeneration in vivo

In order to look for the best proportion of β-tricalcium phosphate（β-TCP）and poly（lactideco-glycolide）（PLGA）we fabricated porous composites β-TCP/PLGA scaffold using freeze-drying method.Morphologicalcharacterization using scanning electron microscopy showed that the interconnected pore distribution was even and there was no significant difference with the increase of PLGA content.Moreover,the porosity,compressive strength and degradation in vitro were characterized.The fabricated scaffolds with increased PLGA in the composites β-TCP/PLGA scaffolds willget stronger mechanicalproperty and better appearance,furthermore,get suitable environment for cells.According to the evaluation indexes for the tissue engineering scaffold,the group of scaffold（β-TCP/PLGA=6：4）was selected to evaluate the induced celladhesion and proliferative ability of the scaffolds.Then as transplant embed into the bone criticaldefect sites on rats femur.The repairing processes of bone defect sites were characterized by X-ray analysis within 12 weeks.X-ray analysis showed that the bone defect sites alldisplayed the formation of callus obviously,In summary,our data suggest that the scaffold（β-TCP/PLGA=6：4）has a promising clinicalfuture in regeneration of bone criticaldefects.

A multi-channel collagen scaffold loaded with neural stem cells for the repair of spinal cord injury

Collagen scaffolds possess a three-dimensional porous structure that provides sufficient space for cell growth and proliferation,the passage of nutrients and oxygen,and the discharge of metabolites.In this study,a porous collagen scaffold with axially-aligned luminal conduits was prepared.In vitro biocompatibility analysis of the collagen scaffold revealed that it enhances the activity of neural stem cells and promotes cell extension,without affecting cell differentiation.The collagen scaffold loaded with neural stem cells improved the hindlimb motor function in the rat model of T8 complete transection and promoted nerve regeneration.The collagen scaffold was completely degraded in vivo within 5 weeks of implantation,exhibiting good biodegradability.Rectal temperature,C-reactive protein expression and CD68 staining demonstrated that rats with spinal cord injury that underwent implantation of the collagen scaffold had no notable inflammatory reaction.These findings suggest that this novel collagen scaffold is a good carrier for neural stem cell transplantation,thereby enhancing spinal cord repair following injury.This study was approved by the Animal Ethics Committee of Nanjing Drum Tower Hospital(the Affiliated Hospital of Nanjing University Medical School),China(approval No.2019AE02005)on June 15,2019.

A partition-type tubular scaffold loaded with PDGF-releasing microspheres for spinal cord repair facilitates the directional migration and growth of cells

The best tissue-engineered spinal cord grafts not only match the structural characteristics of the spinal cord but also allow the seed cells to grow and function in situ.Platelet-derived growth factor（PDGF） has been shown to promote the migration of bone marrow stromal cells;however,cytokines need to be released at a steady rate to maintain a stable concentration in vivo.Therefore,new methods are needed to maintain an optimal concentration of cytokines over an extended period of time to effectively promote seed cell localization,proliferation and differentiation.In the present study,a partition-type tubular scaffold matching the anatomical features of the thoracic 8–10 spinal cord of the rat was fabricated using chitosan and then subsequently loaded with chitosan-encapsulated PDGF-BB microspheres（PDGF-MSs）.The PDGF-MS-containing scaffold was then examined in vitro for sustained-release capacity,biocompatibility,and its effect on neural progenitor cells differentiated in vitro from multilineage-differentiating stress-enduring cells（MUSE-NPCs）.We found that pre-freezing for 2 hours at-20°C significantly increased the yield of partition-type tubular scaffolds,and 30 μL of 25% glutaraldehyde ensured optimal crosslinking of PDGF-MSs.The resulting PDGF-MSs cumulatively released 52% of the PDGF-BB at 4 weeks in vitro without burst release.The PDGF-MS-containing tubular scaffold showed suitable biocompatibility towards MUSE-NPCs and could promote the directional migration and growth of these cells.These findings indicate that the combination of a partition-type tubular scaffold,PDGF-MSs and MUSENPCs may be a promising model for the fabrication of tissue-engineered spinal cord grafts.

Differentiation of Wharton's jelly mesenchymal stem cells into neurons in alginate scaffold

Alginate scaffold has been considered as an appropriate biomaterial for promoting the differentiation of embryonic stem cells toward neuronal cell lineage. We hypothesized that alginate scaffold is suitable for culturing Wharton’s jelly mesenchymal stem cells（WJMSCs） and can promote the differentiation of WJMSCs into neuron-like cells. In this study, we cultured WJMSCs in a three-dimensional scaffold fabricated by 0.25% alginate and 50 m M Ca Cl2 in the presence of neurogenic medium containing 10 μM retinoic acid and 20 ng/m L basic fibroblast growth factor. These cells were also cultured in conventional two-dimensional culture condition in the presence of neurogenic medium as controls. After 10 days, immunofluorescence staining was performed for detecting β-tubulin（marker for WJMSCs-differentiated neuron） and CD271（motor neuron marker）. β-Tubulin and CD271 expression levels were significantly greater in the WJMSCs cultured in the three-dimensional alginate scaffold than in the conventional two-dimensional culture condition. These findings suggest that three-dimensional alginate scaffold cell culture system can induce neuronal differentiation of WJMSCs effectively.