An Investigation on the Effect of Electroacupuncture on Insulin-like Growth Factor in the Cerebral Cortex After Focal Ischemia in Rats
|School||Tianjin Institute of Physical Education|
|Course||Rehabilitation Medicine and Physical Therapy|
|Keywords||Electroacupuncture IGF-1 Focal ischemia Cortex|
Stroke is one of the life-threatening diseases in the world, with a high prevalence middle age and older adults. Greater attention in pathological and clinical research has been paid to the ischemic strokes than hemorrhagic strokes because of its higher prevalence. The insulin-like growth factor (IGF-1) is one of essential growth factor that not only regulates individual’s overall growth and development, but also plays a crucial role in the repairment of nerve tissues after injuries. There has been clinical evidence that electroacupuncture can facilitate functional recovery after stroke. There has also been experimental evidence from animals that electroacupuncture can upregulate the expression of IGF-1 in muscles. Whether electroacupuncture could alter IGF-1 in cerebral cortex after focal ischemia therefore facilitate recovery of brain function has not been examined. The effects of different types of electroacupuncture treatments and their underlying mechanisms also require further study.Objectives: This study aimed to 1) examine the temporal effects of three weeks of electoacupuncture on the limb of SD rats with middle cerebral artery occlusion (MCAO) on the changes of IGF-1 mRNA and proteins in cerebral cortex; 2) ompare the effects of electroacupuncture on the affected and unaffected side of the affected and unaffected side of the MCAO rats for an optimal electroacupuncture treatment in rehabilitation of stroke. Methods: Sixty (60) male SD rats (weight 320-350g) were subjected to MCAO by inserting intraluminal thread through left internal carotid artery (ICA). Six rats were excluded by Bederson score and the remaining 54 rats were randomly divided into three groups: control group (CG, n=18), unaffected limb training group (UALTG, n=18), and affected limb training group (ALTG, n=18). All animals except those in the control group received electroacupuncture 24h after the onset of MCAO. Six rats in each group were sacrificed, in a random order, at 7, 14 and 21 days into the program. Animals were anesthetized with 10% choral hydrate in normal saline (3ml/100mg, intraperitoneally) and cerebral cortex were dissected quickly and divided into two parts. The specimens were frozen in liquid nitrogen before analysed for IGF-1 mRNA expression by RT-PCR and IGF-1protein by Western blot.Results: The major findings of the study include 1) Simlar level of increase of IGF-1 protein in both sides of the ischemic cortex was found in the MCAO control group. The IGF-1 level demonstrated a significant decline in the order of 7d>14d>21d (p<0.001 between the three time points), while the IGF-1 protein level in the non-ischemia cortex was significantly lower compared to the ischemic cortex (p<0.001).2) The expressions of IGF-1 mRNA in the ischemic cortex of the CG increased at 7d but decreased at 14d (p<0.001), and increased again at 21d (p<0.001). There was a delay in the expression of IGF-1 mRNA in the non-ischemia cortex, with an increase only from 14d to 21d (p<0.001).3) The IGF-1 protein level in both sides of the cortex in the electroacupuncture groups was significantly higher than that of the CG ( p<0.001). The IGF-1 protein in both sides of the cortex in the ALTG was significantly higher than that of the CG (p<0.001) at each of the time points. The IGF-1 protein in the non-ischemia cortex of the NALTG was higher than that in the ALTG at 7d and 21d (p<0.001). While the IGF-1 protein was lower at 14d in the non-ischemia cortex, there was a significantly higher level in the ischemic cortex in the ischemic cortex of UALTG, as compared with that of the ALTG (p<0.001).4) There was also a quickly increased expression of IGF-1 mRNA in the ischemic cortex of the UALTG (6.8±0.8 folds) and ALTG (3.0±0.4 folds), which was higher than that of the CG (p<0.001) at the 7d point. However, the expression of IGF-1mRNA in the ischemic cortex of the ALTG (5.7±0.1 folds) become higher than that of the UALTG (3.3±0.8 folds) at the 14d point (p<0.001).5) There was a slowly increased expression of IGF-1mRNA in the non-ischemia cortex. The expression of IGF-1mRNA did not significantly increased in the non-ischemia cortex of electroacupuncture groups till 14d, where the UALTG showed a much profound increase (10.7±1.5 folds compared to CG, p<0.001) than that of the ALTG (1.9±0.2 folds, p<0.05). However, at 21d point the expression of IGF-1mRNA in the non-ischemia cortex of the UALTG became lower than that of the CG (p<0.001) while that of the ALTG became significantly higher than the CG (3.2±0.5 folds, p<0.001).Conclusion: 1) The one-side MCAO induced increase of IGF-1 protein in both sides of the cortex. Ischemia also induced up-regulations of IGF-1mRNA in the ischemic cortex. However, there was a depression phase in IGF-1mRNA level indicating that the protective response might be limited to certain time frame.2) The electroacupuncture on the affected limb increased the level of IGF-1 protein in both sides of the cortex, and IGF-1 mRNA level in the ischemic cortex, indicating that the electroacupuncture on affected limb could enhance the protection function induced by ischemia.3) The electroacupuncture on the unaffected limb increased the level of IGF-1 protein in both sides of the cortex with a higher level of up-regulation of the expression of IGF-1mRNA than the intervention on the unaffected limb. Further studies are required to confirm whether the electroacupuncture on the unaffected limb would promote the protective mechanisms more effectively at early stage of an ischemic attack that would result in better rehabilitation effect.