Objective: To study the changes of (brain-derived neurotrophic factor) BDNF mRNA during embroyonic spinal cord repairing spinal cord injury of adult rats.
Methods: At day 1,3, 5, 7, 10, 15, and 30 after embryonic spinal cord being transplanted into acutely injured spinal cord of adult rats, changes of BDNF mRNA within donor tissue and host tissue were demonstrated qualitatively and quantitatively by in situ hybridization and dot hybridization.
Results: Qualitatively, BDNF mRNA was mainly expressed within cytoplasm of motor neurons and a few gliocytes in normal spinal cord. After spinal cord injury, hybridizing products expanded to the mediate and small-sized neurons, also more gliocytes took part in hybridization response. Following transplantation, positively hybridizing neurons and gliocytes increased in number in host tissue, and embryonic spinal cord kept an expressing level similar to that before being transplanted. It was also revealed quantitatively that reacting intensity of the cells in the injured group was strikingly higher than that in the normal group. However, hybridization intensity in the transplanted group was even higher at many intervals than that in the injured group. Besides, the lasting period for hybridization reaction in the transplanted group was also different from that in the injured group. The most intensive reacting phase in the former presented at day 10 and 15, and in the latter at day 7 after operation.
Conclusions: We suggest that transplanted embryonic spinal cord can, besides provision neurol trophines for itself and host spinal cord, evoke synthetic mechanisms of host spinal cord once holding during its embryonic development so as to enhance expression of the neurotrophin. In this way, the host spinal cord may provide neurotrophin for its regeneration and provide an trophic environment for the grafts to develop and differentiate.