Expression changes of nerve cell adhesion molecules L1 and semaphorin 3A after peripheral nerve injury

The expression of nerve cell adhesion molecule L1 in the neuronal growth cone of the central nervous system is strongly associated with the direction of growth of the axon, but its role in the regeneration of the peripheral nerve is still unknown. This study explored the problem in a femoral nerve section model in rats. L1 and semaphorin 3A m RNA and protein expressions were measured over the 4-week recovery period. Quantitative polymerase chain reaction showed that nerve cell adhesion molecule L1 expression was higher in the sensory nerves than in motor nerves at 2 weeks after injury, but vice versa for the expression of semaphorin 3A. Western blot assay results demonstrated that nerve cell adhesion molecule L1 expression was higher in motor nerves than in the sensory nerves at the proximal end after injury, but its expression was greater in the sensory nerves at 2 weeks. Semaphorin 3A expression was higher in the motor nerves than in the sensory nerves at 3 days and 1 week after injury. Nerve cell adhesion molecule L1 and semaphorin 3A expressions at the distal end were higher in the motor nerves than in the sensory nerves at 3 days, 1 and 2 weeks. Immunohistochemical staining results showed that nerve cell adhesion molecule L1 expression at the proximal end was greater in the sensory nerves than in the motor nerves; semaphorin 3A expression was higher in the motor nerves than in the sensory nerves at 2 weeks after injury. Taken together, these results indicated that nerve cell adhesion molecules L1 and semaphorin 3A exhibited different expression patterns at the proximal and distal ends of sensory and motor nerves, and play a coordinating role in neural chemotaxis regeneration.

Possible Mechanism of Therapeutic Effect of 3-Methyl-l-phenyl-2-pyrazolin-5-one and Bone Marrow Stromal Cells Combination Treatment in Rat Ischemic Stroke Model

Background： The functional improvement following bone marrow stromal cells （BMSCs） transplantation after stroke is directly related to the number of engrafted cells and neurogenesis in the injured brain. Here, we tried to evaluate whether 3-methyl-1-phenyl-2-pyrazolin-5-one （MCI-186）, a free radical scavenger, might influence BMSCs migration to ischemic brain, which could promote neurogenesis and thereby enhance treatment effects after stroke. Methods： Rat transient middle cerebral artery occlusion （MCAO） model was established. Two separate MCAO groups were administered with either MC1-186 or phosphate-buffered saline （PBS） solution to evaluate the expression of stromal cell-derived factor-1 （SDF-1） in ischemic brain, and compared to that in sham group （n 5/group/time point[at 1,3, and 7 days after operation]）. The content ofchemokine receptor-4 （CXCR4, a main receptor of SDF-I） at 7 days after operation was also observed on cultured BMSCs. Another four MCAO groups were intravenously administered with either PBS, MCI-186, BMSCs （2 ×106）, or a combination of MCI-186 and BMSCs （n = 10/ group）. 5-bromo-2-deoxyuridine （BrdU） and Nestin double-immunofluorescence staining was performed to identity the engrafted BMSCs and neuronal differentiation. Adhesive-removal test and foot-fault evaluation were used to test the neurological outcome. Results： MC1-186 upregulated the expression ofSDF- 1 in ischemic brain and CXCR4 content in BMSCs was enhanced after hypoxic stimulation. When MCAO rats were treated with either MCI- 186, BMSCs, or a combination ofMCI- 186 and BMSCs, the neurologic function was obviously recovered as compared to PBS control group （P 〈 0.01 or 0.05, respectively）. Combination therapy represented a further restoration, increased the number of BMSCs and Nestin- cells in ischemic brain as compared with BMSCs monotherapy （P 〈 0.01）. The number ofengrafted-BMSCs was correlated with the density of neuronal cells in ischemic brain （r = 0.72, P 〈 0.01 ） and the improvement of foot-thult （r = 0.70, P 〈 0.0 t ）. Conclusion： MCI- 186 might promote BMSCs migration to the ischemic brain, amplify the neurogenesis, and improve the effects of cell therapy.