| The disfunction after spinal cord injury (SCI) not only casts a shadow over the patients but also brings heavy burdens to the family and society. How to minimize the disfunction of patients with SCI and improve their function has become a widely-focused problem. With the development of new science and technology, the research of repair to SCI has made great progress. However, it was not yet introduced into the clinic, which results from the following reasons. SCI pathology is determined not only by the initial mechanical insult, but also by the secondary damages including ischemia, anoxia, free-radical formation, and excitotoxicity that occur over hours and days following injury. Central nervous system axonal regeneration appears to be impeded partly by myelin-associated inhibitors, loss in adult neurons of an intrinsic ability to overcome inhibitory cues, and formation of a post-lesion scar barrier. These problems blocked the resume of the function after SCI. All of above could hardly be taken over by traditional medication, operation and other methods of therapy. However, the treatment by tissue engineering has brought a ray of hope on it. The treatment by tissue engineering involves three parts, including seeding cells, scaffold material and forming tissue in vitro with the former both. The seeding cells in the tissue-engineered spinal cord involve embryonic stem cells (ESC), neural stem cells(NSC) and mesenchymal stem cells(MSC), which are provided with self-multiplication and multilineage potential. The materials in the tissue-engineered spinal cord are mainly synthesized materials just as PGA, PLA and PLGA, whose surfaces are decorated with materials beneficial to the adherence of cells and the congregation of cell factors. Nevertheless, there were still some problems in the past research of tissue engineering. For instance, stem cells are unable to be differentiated into repairing cells in vivo, and it is difficult to make materials under usual conditions and meet the need of seeding cells. Besides, the production decomposed by materials in vivo is usually acidic, whose possible effect on the body is still unknown. NSCs were differentiated into cholinergic motor neurons with retinoic acid(RA) and sonic hedgehog(Shh) in vitro, which expressed HB9 with identity of motor neurons in spinal cord. Then they were seeded on the scaffold materials, Sapeptide(self-assembling peptide), a kind of 16 peptide composed of arginine, alanine and aspartic acid, to form cellular prostheses to repair SCI. There were some predominances in the compound. First, seeding cells, which were motor neurons instead of stem cells, directly formed the connection with tissue in the host. Second, Sapeptide produced three kinds of indispensable amino acids which were harmless and easy to be taken up and consumed by the body. Third, scaffold was easy to be formed by putting Sapeptide into NaCl solution. At the same time, Sapeptide was observed by scanning electron microscope (SEM), whose absorbancy of water and pH of the solution were measured. Furthermore, its possible toxic effects were observed by injecting it into rats'muscles in the leg. The model of half-cut spinal cord was improved by designing a knife to form SCI and the artifical errors in model of SCI on the rats could be reduced. The model has been verified to be scientific and reliable by pathologic examination, detecting apoptosis of cells, grading the scale of BBB and electrophysiological function. The supporting function of scaffold and the existence rate of cells after transplantation were observed by designing motor neuron-prostheses therapy group (Sapeptide compounded with motor neurons), NSC-prostheses control group (Sapeptide compounded with NSCs), Sapeptide control group, motor neurons control group and trauma control group. Then, nervous tissue fibrous connection between the transplant and the host was evaluated. Finally, the resuming functional differences among five group were compared by grading the scale of BBB and electrophysiologic function. The main results and conclusions were as followed. 1. NSCs were differentiated into cholinergic motor neurons (HB9) with RA and Shh in vitro. The rate of motor neurons in differentiating cells was over 80%. 2. The surface of Sapeptide was regular web through SEM, on which the diameter of hole and fiber was respectively 54μm and 9μm. It was enough to hold seeding cells and beneficial to fibrous connection through the holes. 3. Sapeptide's absorbancy of water was 1087.68% and pH of the solution reduced from 7.40 to 6.79 during 12 weeks, in which no toxic effects were observed. Sapeptide promoted the adherence of cells, on which NSCs could proliferate, differentiate and extend axons. 4. Motor neurons on Sapeptide actively developed axons and were sensitive to factorsaffecting intracellular Ca2+, which was beneficial to synapse between axons from both transplant and host as well as resist trauma. 5. The model of SCI,the length, width and height of deficit in which were 4mm×4mm×2mm,was created successfully. The model has been verified to be scientific and reliable by experiments. 6. It could be proved that transplanted cells could exist, and Sapeptide prevented tissue around trauma from caving in, promoted fiber to regenerate regularly and helped neurons to exist in the regenerative tissue and reduced the apoptosis of cells in tissue around trauma by the dyeing of HE, Nissl and Holmes, detecting apoptosis of cells and technology of histochemistry and histofluorescence. 7. The regenerative fiber forming functional connection with host and the promotion of the function of movement and electrophysiology benefited from transfering tissue-engineered spinal cord formed by motor neurons and Sapeptide to the traumatic part of spinal cord.
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