[Changes in the related indicators of bone formation and bone resorption in severely burned rats].

Objective: To observe the changes in the related indicators of bone formation and bone resorption in severely burned rats. Methods: The experimental research method was adopted. Thirty female Sprague-Dawley rats aged 6 to 8 weeks were divided into sham injury group, 12% total body surface area (TBSA) full-thickness burn group, and 24%TBSA full-thickness burn group according to the random number table, with 10 rats in each group. The rats were treated on the back correspondingly, after which, the burned rats were rehydrated by intraperitoneal injection according to the Parkland formula, and the wound was coated with 20 g/L iodophor until wound healing. On post injury day (PID) 28, the tibia tissue of rats in each group was collected. The new bone tissue and the number of osteoclasts were observed after staining with Masson and tartrate-resistant acid phosphatase, respectively. The abdominal aortic blood of rats in each group was harvested for serum preparation. The bone metabolism indexes of serum calcium ion and phosphorus ion concentration were determined by the methyl thymol blue colorimetric method and phosphomolybdic acid method, respectively. The serum levels of bone formation marker of aminoterminal propeptide of type 1 procollagen (P1NP) and bone resorption marker of beta-carboxy-terminated peptide of type Ⅰ collagen (β-CTX) were determined by enzyme-linked immunosorbent assay. The first lumbar spine tissue of rats in each group was collected, and the mRNA expression levels of osteoprotegerin, receptor activator of nuclear factor-κB ligand (RANKL), tumor necrosis factor receptor-associated factor 6 (TRAF-6), nuclear factor of activated T cell 1 (NFATC1), c-Fos, and c-Src were detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction. Data were statistically analyzed with one-way analysis of variance, Bonferroni method, Welch test, Games-Howell test, Kruskal-Wallis test, Mann-Whitney U test, and Bonferroni correction. Results: On PID 28, compared with that in sham injury group, the formation of new bone tissue in the tibia tissue of rats in the two burn groups was decreased, and the larger the burn area, the more obvious the decrease. The numbers of osteoclasts in the tibia tissue of rats in the two burn groups were similar, both significantly more than the number in sham injury group. On PID 28, the serum calcium ion concentration and serum level of β-CTX of rats in the three groups were similar (P>0.05). The serum phosphorus ion concentration of rats in 24%TBSA full-thickness burn group was significantly higher than that in 12%TBSA full-thickness burn group (P<0.05), and the serum phosphorus ion concentrations in the two burn groups were significantly higher than the concentration in sham injury group (P<0.01). The serum level of P1NP of rats in 24%TBSA full-thickness burn group was significantly lower than that in sham injury group (P<0.01). On PID 28, the mRNA expression levels of osteoprotegerin in the first lumbar spine tissue of rats in sham injury group, 12%TBSA full-thickness burn group, and 24%TBSA full-thickness burn group were 1.01±0.20, 1.71±0.83, and 2.24±0.51, respectively, and that in 24%TBSA full-thickness burn group was significantly higher than that in sham injury group (P<0.01). The mRNA expression level of RANKL in the first lumbar spine tissue of rats in 24%TBSA full-thickness burn group was 1.31±0.17, which was significantly higher than 1.00±0.14 in sham injury group and 0.97±0.10 in 12%TBSA full-thickness burn group (P<0.01). The mRNA expression levels of TRAF-6, NFATC1 (Z=3.141, 3.782), and c-Src in the first lumbar tissue of rats in 12%TBSA full-thickness burn group and 24%TBSA full-thickness burn group and the mRNA expression level of c-Fos in the first lumbar tissue of rats in 12%TBSA full-thickness burn group were significantly higher than those in sham injury group (P<0.05 or P<0.01). The mRNA expression levels of c-Fos and c-Src in the first lumbar spine tissue of rats in 12%TBSA full-thickness burn group were significantly higher than those in 24%TBSA full-thickness burn group (P<0.01). Conclusions: Severe burns can cause a decrease in the generation of new bone tissue, an increase in the number of osteoclasts and the serum phosphorus ion concentration, and a decrease in the serum level of P1NP in rats. The level of osteoprotegerin, RANKL, TRAF-6, NFATC1, c-Fos, and c-Src in bone tissue showed an increasing trend while the level of NFATC1, c-Fos, and c-Src showed a decreasing trend with the increase of burn area.目的： 研究严重烧伤大鼠骨形成及骨吸收相关指标的变化。 方法： 采用实验研究方法。将30只6~8周龄SD雌性大鼠按随机数字表法分为假伤组、12%体表总面积（TBSA）Ⅲ度烧伤组、24%TBSAⅢ度烧伤组，每组10只。于各组大鼠背部进行相应处理，之后仅烧伤大鼠按Parkland公式经腹腔注射补液，创面外涂20 g/L碘伏，直至创面愈合。伤后28 d，取各组大鼠胫骨组织，分别行Masson、抗酒石酸酸性磷酸酶染色，观察新生骨组织、破骨细胞数量；取各组大鼠腹主动脉血制备血清，分别采用甲基百里酚蓝比色法、磷钼酸法测定骨代谢指标血清钙离子、磷离子浓度，采用酶联免疫吸附测定法检测血清中骨形成标志物Ⅰ型前胶原氨基端前肽（P1NP）和骨吸收标志物β-Ⅰ型胶原羧基端肽（β-CTX）水平；取各组大鼠第1腰椎组织，采用实时荧光定量反转录PCR法检测护骨因子、核因子κB受体激活蛋白配体（RANKL）、肿瘤坏死因子受体相关因子6（TRAF-6）、活化T细胞核因子1（NFATC1）、c-Fos、c-Src的mRNA表达水平。数据处理采用单因素方差分析、Bonferroni法、Welch检验、Games-Howell检验、Kruskal-Wallis检验、Mann-Whitney U检验及Bonferroni校正。 结果： 伤后28 d，与假伤组比较，2个烧伤组大鼠胫骨组织中新生骨组织生成均减少，烧伤面积越大减少越明显；2个烧伤组大鼠胫骨组织中破骨细胞数量相近，均较假伤组明显增多。伤后28 d，3组大鼠血清钙离子浓度、血清中β-CTX水平相近（P>0.05）；24%TBSAⅢ度烧伤组大鼠血清磷离子浓度明显高于12%TBSAⅢ度烧伤组（P<0.05），且2个烧伤组大鼠血清磷离子浓度均显著高于假伤组（P<0.01）；24%TBSAⅢ度烧伤组大鼠血清中P1NP水平明显低于假伤组（P<0.01）。伤后28 d，假伤组、12%TBSAⅢ度烧伤组、24%TBSAⅢ度烧伤组大鼠第1腰椎组织中护骨因子mRNA表达水平分别为1.01±0.20、1.71±0.83、2.24±0.51，其中24%TBSAⅢ度烧伤组明显高于假伤组（P<0.01）；24%TBSAⅢ度烧伤组大鼠第1腰椎组织中RANKL mRNA表达水平为1.31±0.17，明显高于假伤组的1.00±0.14与12%TBSAⅢ度烧伤组的0.97±0.10（P<0.01）；12%TBSAⅢ度烧伤组、24%TBSAⅢ度烧伤组大鼠第1腰椎组织中TRAF-6、NFATC1（Z=3.141、3.782）、c-Src mRNA表达水平及12%TBSAⅢ度烧伤组大鼠第1腰椎组织中c-Fos mRNA表达水平均明显高于假伤组（P<0.05或P<0.01）；12%TBSAⅢ度烧伤组大鼠第1腰椎组织中c-Fos、c-Src mRNA表达水平均明显高于24%TBSAⅢ度烧伤组（P<0.01）。 结论： 严重烧伤可引起大鼠新生骨组织生成减少及破骨细胞数量增多，血清磷离子浓度升高与血清中P1NP水平下降，骨组织中护骨因子、RANKL、TRAF-6、NFATC1、c-Fos、c-Src呈升高趋势，且NFATC1、c-Fos、c-Src随烧伤总面积增加呈下降趋势。.