| Objective: Diabetic peripheral neuropathy (DPN) is a crucial patho-foundation of diabetic foot (DF). It's the result of various factors' complex action, such as metabolic disorder, neurotrophy disturbance, vasculopathy and oxidative stress, and so on. Among the total, altered neurotrophism plays an important role in the mechanism of DPN. Researches show that, there are evident pathobiological changes in nerve tissue of DPN patients, at the same time, hyperglycaemia reduces the expression of Caveolin-1(Cav-1) and IGF-1 in Schwann cells. The reduction has correlation with the severity degree of neuropathy. So, it's thought that the reduction of these two factors may alter the neurotrophy by different mechanisms, and this may become an important risk factor in the development of DPN. At present, most of results come from animal, but research based on human tissue is seldom. We obtain the femoral nerve from the DF patients for the observation the pathobiological changes with different course of diabetes, and the expression level of Cav-1 and IGF-1 in Schwann cells, to discuss the relationship between them and the role of these factors in the development of DPN.Methods: We selected patients who had undertaken high amputation in the Foot department of the Metabolic Disease Hospital of Tianjin Medical University from January 2003 to November 2005 as the research objects. And they all had DPN. There were 40 patients (22 males and 18 females) in our study(mean age, 67.83±8.74 years). We divided them into three groups depending on their course of diabetes: group A (≤5 years), group B (6-10 years) and group C,(＞10 years). We obtained nerve samples when high amputation operation was progressing, l. The samples were putted in the solution of 10% formalin, and then embedded in paraffin, the sections were used to observe the general and the myelin sheath structure of the femoral nerve tissue by HE staining and Weil's staining. And then we counted the nerve fiber's density under light microscope. 2. The samples were putted in the solution of the 4% glutaric dialdehyde and 1% osmium tetroxide to fixate, and then observed the changes of ultramicrostructure with HITACHI H7500 transmission electron microscope. 3. To observe the expressions of caveolin-1 and IGF-1 in femoral nerve by immunohistochemistry and count the percent of positive cells under light microscope.Results: 1. There's comparability in clinical data and biochemical indicators among three groups, and variances in course, fasting blood glucose(FBG) and glycosylated hemoglobin ( HbAlc ) show statistical significance. And variances in the others have no statistical significance. 2. Observation of histology: (1) HE and Well's staining: we found there's evident pathobiological changes in femoral nerve among the three groups. Group A: Diameters of nerve fiber are not uniformity, axis cylinder anachromasis and degeneration can be seen by chance, regenerate axis cylinders show up, and the numbers of small vessels in nerve tract increase, small vessel walls thicken. Group B: The nerve fiber is sparse, diameters of which are not uniformity. Many axis cylinders display anachromasis and degeneration, Schwann cells proliferation. Group C: The numbers of nerve fiber decrease obviously, and the fibers thin. The density of regeneration clump decrease, the quantity of small vessels in nerve tract decrease, and the deformity and thickening of vessel walls get worse. The variance of fiber's density among the three groups has statistical significance (P＜0.05) , and it has negative correlation with HbAlc (r=-42.630, P＜0.01) and has positive correlation with Cav-1 ( r=394.930, P＜0.01 ). (2) Ultrastructural pathology: Medullary sheaths hyperplasy, the structure of the layers mixes together, vanishes or delaminate. Medullary cord is oedema, and the numbers of microfilament and microtubule decrease. There are a lot of big and high density lipid drop. Chondriosomes, which numbers decrease, display dropsy and vacuolization, and cristaes mix together or vanish. And rough endoplasmic reticulum degranulate. 3. Results of immunohistochemistry: The expression of Cav-1 and IGF-1 are all positive in three groups. The variances have statistical significance(P＜0.01). Cav-1 has negative correlation with HbAlc (r=-9.010, P＜0.05)and has positive correlation with density of nerve fiber(r=0.001, P＜0.05). IGF-1 has negative correlation with course(r=-2.543, P＜0.01) and HbAlc(r=-4.580, P＜0.05),and has positive correlation with density of nerve fiber(r=0.044, P＜0.05).Conclusions: 1. Results obtained from light microscope and electron microscope all prove that, there are significant pathological changes in DF patients with DPN, and the degree is aggravating along with the course of diabetes. 2. As the lengthen of the course and the increase of HbA1c, the density of nerve fiber decreased. They may have correlation with the severity of DPN. The reduction of Car-1 may promote the development of DPN. 3. The expressions of Car-1 and IGF-1 are all positive in femoral nerve among three groups, but they all decreased along with the course. Depending on the multiple regression results, the reduction of Car-1 may have correlation with HbAlc and the density of nerve fiber. And the reduction of IGF-1 mayhave correlation with the course, HbA1c and the density of nerve fiber. Ina word, long-term hyperglycemia leads to different pathological changes.It decreases the density of nerve fiber and the level of Cav-1 and IGF-1in Schwann cells in DF patients with different course. And the reductionof Cav-1 and IGF-1 may takes part in the development of DPN.
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