| Background and objective：Neuropathic pain refers to a variety of chronic pain conditions with different underlyingpathophysiologic mechanisms. Neuropathic pain can originate from neuronal tissue damageor a dysfunction in the nervous system. The abnormal perception of neuropathic pain ischaracterized as being allodynic (a typically nonpainful stimulus is perceived as painful),hyperalgesic (a normally painful stimulus is exaggerated) or as spontaneuous (shock-like,stabbing or burning pain sensations that are unrelated to a known stimulus). The pastresearches about neuropathic pain mainly focused on neuron and nerve cells. However, recentstudies indicated that a communication existed between the astrocytes and the nervous system.A great number of animal and cellular experiments showed that astrocyte regulated theneuropathic pain by means of inflammation. Astrocytes were known to play a role in thedevelopment, spread, and potentiation of neuropathic pain. Recently, research indicated theactivation of FGFR family in the neuropathic pain model may have participated in theforming of neuropathic pain.Fibroblast growth factor receptors (FGFRs) are the members of receptor tyrosinekinase (RTK) family, which exert their biological function by associating with fibroblastgrowth factors (FGFs). FGFR3is widely expressed in the development of central nervesystem. Researches indicated that it was responsible for the development of central nervesystem. FGFR3regulated the differentiation of various neurons. And the expression ofFGFR3could be observed in the precursor cell of spinal oligodendrocyte and spinal motorneuron. And other studies also found FGFR3could bind to its ligand FGFs specifically toregulate the differentiation, growth and proliferation of astrocyte. Therefore, we propose that FGFR3might have participated in the development and maintenance of neuropathicpain by influencing the activity of astrocyte. To identify the mechanism of FGFR3inregulating neuropathic pain will helping us to understand the role of FGFR3in neuropathicpain. And it will benefit to find the new therapeutic targets for neuropathic pain.Main methods and techniques:1. Male SD rats (n=20) weighing180-200g were randomly divided into2groups: onegroup of control (sham) and another group of surgery (SNI). The paw withdraw mechanicalthreshold (PWPT) of rats’ right paws were measured one day before the operation. And thechanges of PWPT were measured at1,3,5and7days after operation by Von Frey hairs. Andthe L4-L6spinal cord were taken to observe GFAP activation and mRNA expression levelrespectively by laser scanning confocal microscope and real time PCR. The mRNAexpression of FGFRs was detected by real time PCR.2. Male SD rats (n=40) were randomly divided into two groups: one group of control(sham, n=20) and another group of surgery (SNI, n=20). The PWPT values of rats’ right pawwere detected at pre-operated1d and post-operated1,3,5,7days. And the expressions ofGFAP and FGFR3were evaluated by double-labeled immunofluorescence after7days ofoperation. The expressions of FGFR3in each time point of post-operation were observed bywestern blot.3. Male SD rats were divided into three groups in random: group A (for comparison)of intrathecal catheterization in normal rats; group B of SNI+saline injection,20μl eachday for14days; group C of SNI+intrathecally injecting FGFR3inhibitors,20μl each dayfor14days. The PWPT of three groups rats were detected at pre-operated1d andpost-operated1,5,7,14days. And the L4-L6sections of spinal cords of three group ratswere obtained for immunofluorescence observation of the expression of GFAP and FGFR3seven days after the operation. The expression of GFAP, TNF-α and FGFR3mRNA in eachtime point before and after the operation were also be examined. Results:1. Compared with sham, the PWPT of SNI group decreased sharply (P<0.05), andGFAP positive cells increased remarkly. And the expression of GFAP mRNA rised at firstday after operation and reached the peak at the fifth day. The mRNA expressions ofdifferent members of FGFRs family were different from each other. The expression ofFGFR1mRNA reached the peak at first day after operation in two groups and decreasedsubsequently. The expressions of FGFR2~4mRNA maintained at a low level within5daysafter operation in both two groups, but increasing remaikly from the7th day after operationonly of SNI group (P<0.05).2. No obvious difference was found in two groups of pre-operated1d rats (P>0.05).The PWPT values of SNI group at1,3,5,7days pos-toperation were6.67±2.12，3.17±0.99，2.33±0.65,1.75±0.31respectively, while the PWPT values of sham group were12.75±2.83,12.33±2.84,12.08±2.57,11.50±2.65, correspondingly. Compared with shamgroup, there was a significant decrease of PWPT of SNI group (P<0.05). An obviousco-expression of FGFR3and GFAP was found in astrocyte of cornu dorsale medullaespinalis at7days after operation. And the number of positive astrocytes of SNI group wasobviously higher than that of sham group. The expression of FGFR3protein of SNI group at1,3,5,7days pos-toperation were0.280±0.015,0.328±0.026,0.568±0.027,0.529±0.033respectively. While the expression of FGFR3protein of sham group were0.193±0.013,0.214±0.021,0.295±0.025,0.266±0.027. Compared with sham group, the expression ofFGFR3protein of SNI group increased gradually with time (P<0.05)。3. The change of PWPT values of A group rats was not significant. The PWPT valueof group C increased slightly with time compared with group B, but less obvious than groupA. Seven days after the operation, the number GFAP positive cells and FGFR3positive cellsin group C was significantly lower than group B (P <0.05), but higher than group A (P<0.05). Compared with group B, the expression of GRAP, TNF-α, FGFR3and mRNA ofgroup C were rapidly decreased with time (P<0.05). After intrathecally injecting FGFR3 inhibitors, the expression of FGFR3and GFAP were negatively correlated with PWPT.Conclusion：1. The relation of astrocytes GFAP with FGFRs mRNA expression changes wasobvious in NPP process. It suggested that FGFRs may play an important role in NPPmaintence and development.2. In the process of neuropathic pain, there is a up expression of FGFR3, whichprobably involve in the activation of GFAP and play an important role in the developmentand maintance of NPP.3. Intrathecal injection of PD173074can reduce the high expression of GFAP, TNF-αand FGFR3and relieve the pain of NPP simultaneously. FGFR3might be a suitablemolecular target for curing NPP. |
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