Endogenous Brain Repair: Overriding intrinsic lineage determinates through injury-induced micro-environmental signals

Collagen-chitosan scaffold impregnated with bone marrow mesenchymal stem cells for treatment of traumatic brain injury

Combinations of biomaterials and cells can effectively target delivery of cells or other therapeutic factors to the brain to rebuild damaged nerve pathways after brain injury. Porous collagen-chitosan scaffolds were prepared by a freeze-drying method based on brain tissue engineering. The scaffolds were impregnated with rat bone marrow mesenchymal stem cells. A traumatic brain injury rat model was established using the 300 g weight free fall impact method. Bone marrow mesenchymal stem cells/collagen-chitosan scaffolds were implanted into the injured brain. Modified neurological severity scores were used to assess the recovery of neurological function. The Morris water maze was employed to determine spatial learning and memory abilities. Hematoxylin-eosin staining was performed to measure pathological changes in brain tissue. Immunohistochemistry was performed for vascular endothelial growth factor and for 5-bromo-2-deoxyuridine (BrdU)/neuron specific enolase and BrdU/glial fibrillary acidic protein. Our results demonstrated that the transplantation of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds to traumatic brain injury rats remarkably reduced modified neurological severity scores, shortened the average latency of the Morris water maze, increased the number of platform crossings, diminished the degeneration of damaged brain tissue, and increased the positive reaction of vascular endothelial growth factor in the transplantation and surrounding areas. At 14 days after transplantation, increased BrdU/glial fibrillary acidic protein expression and decreased BrdU/neuron specific enolase expression were observed in bone marrow mesenchymal stem cells in the injured area. The therapeutic effect of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds was superior to stereotactic injection of bone marrow mesenchymal stem cells alone. To test the biocompatibility and immunogenicity of bone marrow mesenchymal stem cells and collagen-chitosan scaffolds, immunosuppressive cyclosporine was intravenously injected 12 hours before transplantation and 1-5 days after transplantation. The above indicators were similar to those of rats treated with bone marrow mesenchymal stem cells and collagen-chitosan scaffolds only. These findings indicate that transplantation of bone marrow mesenchymal stem cells in a collagen-chitosan scaffold can promote the recovery of neuropathological injury in rats with traumatic brain injury. This approach has the potential to be developed as a treatment for traumatic brain injury in humans. All experimental procedures were approved by the Institutional Animal Investigation Committee of Capital Medical University, China (approval No. AEEI-2015-035) in December 2015.

Harnessing migraines for neural regeneration

The success of naturalistic or therapeutic neuroregeneration likely depends on an internal milieu that facilitates the survival, proliferation, migration, and differentiation of stem cells and their assimilation into neural networks. Migraine attacks are an integrated sequence of physiological processes that may protect the brain from oxidative stress by releasing growth factors, suppressing apoptosis, stimulating neurogenesis, encouraging mitochondrial biogenesis, reducing the production of oxidants, and upregulating antioxidant defenses. Thus, the migraine attack may constitute a physiologic environment conducive to stem cells. In this paper, key components of migraine are reviewed – neurogenic inflammation with release of calcitonin gene-related peptide (CGRP) and substance P, plasma protein extravasation, platelet activation, release of serotonin by platelets and likely by the dorsal raphe nucleus, activation of endothelial nitric oxide synthase (eNOS), production of brain-derived neurotrophic factor (BDNF) and, in migraine aura, cortical spreading depression – along with their potential neurorestorative aspects. The possibility is considered of using these components to facilitate successful stem cell transplantation. Potential methods for doing so are discussed, including chemical stimulation of the TRPA1 ion channel, conjoint activation of a subset of migraine components, invasive and noninvasive deep brain stimulation of the dorsal raphe nucleus, transcranial focused ultrasound, and stimulation of the Zusanli (ST36) acupuncture point.