烧伤早期家兔小肠细胞凋亡的研究

An experimental study on the apoptosis of rabbit small intestinal cells during early postburn stage

目的 探讨严重烧伤早期家兔小肠粘膜上皮细胞、淋巴细胞以及蚓状突淋巴细胞凋亡及其意义。 方法 采用日本大耳白兔 2 5只 ,随机分成 5组 :正常对照组、严重烧伤 3、6、12、2 4h组 ,每组均为 5只。各烧伤组制作成 30 %TBSAⅢ度烧伤动物模型 ,于伤后相应时相点对 5个部位的肠组织取材 ,行HE染色、电镜检查及用DNA切口末端标记技术 (TUNEL)行原位细胞凋亡检测 ,TUNEL切片作统计分析。 结果 HE染色烧伤组见较多凋亡细胞单个分散在小肠及蚓状突粘膜上皮层、粘膜固有层 (部分延伸到粘膜下层 )的淋巴小结和散在淋巴组织中 ;伤后 2 4h组有少数肠粘膜断裂 ;所有切片未见明显炎症及坏死现象。电镜显示凋亡小体形成。TUNEL法见大量呈蓝黑色的阳性细胞核 ,分布位置同HE染色。伤后 3h小肠及蚓状突细胞凋亡数较对照组已有明显增多 (P<0 .0 1) ,到 6和 12h显著升高达峰值 (P <0 .0 1) ,伤后 2 4h已下降接近 3h水平 ,但仍高于对照组 (P <0 .0 1) ;烧伤组家兔中段及远端小肠粘膜上皮细胞凋亡数均高于近端小肠 (P <0 .0 5 )。 结论 严重烧伤早期家兔小肠粘膜上皮细胞、淋巴细胞以及蚓状突淋巴细胞大量凋亡 ,中远端小肠粘膜上皮细胞凋亡较近端小肠显著 ,这些变化可能是烧伤后肠道细菌及内毒素移位的细胞学基础。

Objective To explore the significance of apoptosis of rabbit small intestinal mucosal epithelial cells and lymphocytes, and lymphocytes of lumbrical process at early postburn stage. Methods Twenty-five Japanese white rabbits were randomly divided into 5 groups with 5 in each group, i.e. normal control (N), 3-postburn-hour group (3 PBH), 6 PBH, 12 PBH and 24 PBH groups. The rabbits in all PBH groups were inflicted with 30% TBSA Ⅲ degree of flame burn on the back. The intestinal tissue samples were harvested from 5 anatomical sites for HE staining, electron microscopic examination and the detection of apoptosis in situ by TUNEL method at all the postburn time points. The results of TUNEL slides were analyzed statistically. Results HE staining revealed that there were relatively abundant apoptotic cells scattering solitarily in the lymph nodules and diffuse lymphatic tissue in the mucosal epithelial and mucosal lamina propria (and partially extended into the submucosal layer ) of the intestine and lumbrical process in all burn groups. There were some disruption of intestinal muosa in 24 PBH group. But no obvious inflammatory reaction and signs of necrosis were observed in all the slides. Apoptotic body formation could be identified by EM. Large number of blue-black positive cellular nuclei were revealed by TUNEL method with their distribution as similar to that found by HE staining. When comparing with those in control group, the apoptotic cells in small intestine and lumbrical process were increased obviously ( P < 0.01) in 3 PBH group and reached the top level in 6 and 12 PBH groups ( P < 0.01), declining thereafter to near value of 3 PBH in 24 PBH group, though it was still higher than control ( P < 0.05). The number of apoptotic epithelial cells in middle distal portions of small intestinal mucosa in burn groups was much higher than that in proximal intestine ( P < 0.05). Conclusion There was a large number of apoptotic cells in rabbit small intestinal mucosal epithelium, gut associated lymphoid tissue and lymphocytes in the lumbrical process, especially in the middle and distal portions of the intestine. These change might be the cellular basis of postburn intestinal translocation of bacteria and endotoxin.