Neurotrophin-3 (NT3) is an important neurotrophic factor for spinal cord injury (SCI) repair. However, constant exchange of cerebrospinal fluid often decreases the effective dosage of NT3 at the targeted injury site. In the present study, a recombinant collagen-binding NT3 (CBD-NT3), consisting of a collagen-binding domain (CBD) and native NT3, was constructed. Linear rat-tail collagen (LRTC) was used as a physical carrier for CBD-NT3 to construct a LRTC/C3 system. The collagen-binding ability of CBD-NT3 was verified, and the bioactivity of CBD-NT3 was assayed with neurite outgrowth of dorsal root ganglia (DRG) explants and DRG cells in vitro. After complete spinal cord transection in rats, LRTC/CBD-NT3 or the LRTC/NT3 system was transplanted into the injury site. Hindlimb locomotion recovery was closely observed using the Basso-Beattie-Bresnahan (BBB) locomotor rating scale and the grid walk test. Significant improvement was observed in the LRTC/CBD-NT3 group. The results of regenerating nerve fiber and anterograde tracing of biotinylated dextran amine (BDA)-labeled corticospinal tract (CST) fibers demonstrated axonal regeneration of LRTC/CBD-NT3 in the injured spinal cord. Serotonin fiber regrowth also illustrated the effectiveness of LRTC/CBD-NT3. Thus, collagen-binding NT3 with LRTC may provide an effective method for treating SCI.

Intracerebral hemorrhage (ICH) is a common and devastating disease affecting millions of people worldwide annually. Exaggerated inflammation and apoptosis are two pivotal pathological processes for secondary brain injury after ICH. Quercetin, a flavonoid widely distributed in various herbs, fruits and vegetables, has been proved to improve neuronal functional recovery in spinal cord injury rats. However, the efficacy of quercetin in caring for post-ICH brain injury has not been investigated. In the present study, we established an ICH model by injecting type VII bacterial collagenase (0.5U) into the central striatum of male Sprague-Dawley rats. The animals were randomized to four groups: sham-operation group; ICH + vehicle group; ICH + 5 mg/kg quercetin group; and ICH + 50 mg/kg quercetin group. The expression levels of IL-1β, IL-4, IL-6 and TNF-α in the brain tissue were assayed by Real-time PCR, ELISA and Western Blot, and cell apoptosis was assayed by TUNEL and caspase-3 staining 3 days after model establishment. It was found that the lesion volume, the brain water content, the expression levels of the four inflammation markers and the number of apoptotic cells were reduced significantly in ICH rats receiving quercetin, especially in 50 mg/kg quercetin group. These results confirmed the therapeutic efficacy of quercetin in repairing brain injury, probably by inhibiting inflammatory response and apoptosis, thus promoting nerve functional restoration.

Immunohistochemical distribution and cellular localization of neurotrophins was investigated in adult monkey brains using antisera against nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4). Western blot analysis showed that each antibody specifically recognized appropriate bands of approximately 14.7 kDa, 14.2 kDa, 13.6 kDa, and 14.5 kDa, for NGF, BDNF, NT-3, and NT-4, respectively. These positions coincided with the molecular masses of the neurotrophins studied. Furthermore, sections exposed to primary antiserum preadsorbed with full-length NGF, BDNF, NT-3, and NT-4 exhibited no detectable immunoreactivity, demonstrating specificities of the antibodies against the tissues prepared from rhesus monkeys. The study provided a systematic report on the distribution of NGF, BDNF, NT-3, and NT-4 in the monkey brain. Varying intensity of immunostaining was observed in the somata and processes of a wide variety of neurons and glial cells in the cerebrum, cerebellum, hippocampus, and other regions of the brain. Neurons in some regions such as the cerebral cortex and the hippocampus, which stained for neurotrophins, also expressed neurotrophic factor mRNA. In some other brain regions, there was discrepancy of protein distribution and mRNA expression reported previously, indicating a retrograde or anterograde action mode of neurotrophins. Results of this study provide a morphological basis for the elucidation of the roles of NGF, BDNF, NT-3, and NT-4 in adult primate brains.

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