Barron Lauren, Sun Raphael C, Aladegbami Bola, Erwin Christopher R, Warner Brad W, Guo Jun
Division of Pediatric Surgery, St. Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri.
Cell Mol Gastroenterol Hepatol. 2016 Dec 10;3(2):231-244. doi: 10.1016/j.jcmgh.2016.10.006. eCollection 2017 Mar.
BACKGROUND & AIMS: Intestinal adaptation is a compensatory response to the massive loss of small intestine after surgical resection. We investigated the role of intestinal epithelial cell-specific mammalian target of rapamycin complex 1 (i-mTORC1) in intestinal adaptation after massive small bowel resection (SBR).
We performed 50% proximal SBR on mice to study adaptation. To manipulate i-mTORC1 activity, transgenic mice were crossed with tuberous sclerosis complex () or mice to inducibly activate or inactivate i-mTORC1 activity with tamoxifen. Western blot was used to confirm the activity of mTORC1. Crypt depth and villus height were measured to score adaptation. Immunohistochemistry was used to investigate differentiation and rates of crypt proliferation.
After SBR, mice treated with systemic rapamycin showed diminished structural adaptation, blunted crypt cell proliferation, and significant body weight loss. Activating i-mTORC1 via TSC1 deletion induced larger hyperproliferative crypts and disorganized Paneth cells without a significant change in villus height. After SBR, ablating TSC1 in intestinal epithelium induced a robust villus growth with much stronger crypt cell proliferation, but similar body weight recovery. Acute inactivation of i-mTORC1 through deletion of Raptor did not change crypt cell proliferation or mucosa structure, but significantly reduced lysozyme/matrix metalloproteinase-7-positive Paneth cell and goblet cell numbers, with increased enteroendocrine cells. Surprisingly, ablation of intestinal epithelial cell-specific Raptor after SBR did not affect adaptation or crypt proliferation, but dramatically reduced body weight recovery after surgery.
Systemic, but not intestinal-specific, mTORC1 is important for normal adaptation responses to SBR. Although not required, forced enterocyte mTORC1 signaling after resection causes an enhanced adaptive response.
肠道适应性是手术切除后小肠大量丢失后的一种代偿反应。我们研究了肠道上皮细胞特异性哺乳动物雷帕霉素靶蛋白复合物1（i-mTORC1）在大量小肠切除（SBR）后肠道适应性中的作用。
我们对小鼠进行50%近端SBR以研究适应性。为了操纵i-mTORC1活性，将转基因小鼠与结节性硬化复合物（）或小鼠杂交，用他莫昔芬诱导激活或失活i-mTORC1活性。使用蛋白质免疫印迹法确认mTORC1的活性。测量隐窝深度和绒毛高度以评估适应性。使用免疫组织化学法研究分化和隐窝增殖率。
SBR后，全身使用雷帕霉素治疗的小鼠结构适应性减弱，隐窝细胞增殖减弱，体重显著减轻。通过缺失TSC1激活i-mTORC1可诱导更大的高增殖性隐窝和潘氏细胞紊乱，绒毛高度无显著变化。SBR后，在肠道上皮中消融TSC1可诱导强烈的绒毛生长和更强的隐窝细胞增殖，但体重恢复相似。通过缺失Raptor急性失活i-mTORC1不会改变隐窝细胞增殖或黏膜结构，但会显著减少溶菌酶/基质金属蛋白酶-7阳性潘氏细胞和杯状细胞数量，同时肠内分泌细胞增加。令人惊讶的是，SBR后消融肠道上皮细胞特异性Raptor并不影响适应性或隐窝增殖，但会显著降低术后体重恢复。
全身而非肠道特异性的mTORC1对SBR的正常适应性反应很重要。虽然不是必需的，但切除后强迫肠上皮细胞mTORC1信号传导会导致增强的适应性反应。
