Armendariz-Borunda J, Katai H, Jones C M, Seyer J M, Kang A H, Raghow R
Veterans Affairs Medical Center, Nashville, Tennessee.
Lab Invest. 1993 Sep;69(3):283-94.
Transforming growth factor beta 1 (TGF beta 1) gene expression is increased in CCl4-injured rat livers. The biologic link of this increase and liver regeneration has not been established.
To explore the identity of the TGF beta 1-producing cells in the CCl4 regenerating liver, we hybridized untreated and CCl4-treated liver sections of TGF beta 1-specific riboprobes and immunolocalized TGF beta 1 protein, simultaneously. To assess the dynamics of cellular proliferation during hepatic regeneration, chronologic changes in the cellular DNA synthesis were also monitored by [3H]thymidine incorporation and autoradiography. In situ hybridization analyses were further extended by subfractionation of nonparenchymal cells into Kupffer cells/macrophages, endothelial and Ito cells, and determining TGF beta 1 mRNA levels in different cell types. Finally, we experimentally tested if the temporal relationship between the transient elevation of expression of TGF beta 1 and hepatic cell proliferation were casually related.
We observed that the rate of DNA synthesis was the highest around 36 hours post-treatment and preceded the time of enhanced accumulation of TGF beta 1 transcripts and protein, both of which peaked at approximately 48 hours and declined thereafter. Transient upregulation of TGF beta 1 gene expression was seen in the inflammatory cell infiltrates around the central vein and at less extent, in portal tracts, and in perisinusoidal cells near the zone of necrosis. Like TGF beta 1 transcripts, TGF beta 1 protein was also predominantly co-localized in and around the pericentral and periportal cells. Kupffer cells, that accumulate abundantly in the liver 48 hours after CCl4 administration, were the primary producers of TGF beta 1. The injection of neutralizing anti-TGF beta 1 antibodies into animals prevented both the decline in [3H]thymidine incorporation and cell division in the waning phases of hepatic regeneration at 72 hours.
Based on our observations that (i) TGF beta 1 gene expression is triggered transiently during a crucial phase of liver regeneration, (ii) the exogenously added TGF beta 1 inhibits hepatic DNA synthesis and that (iii) the administration of TGF beta 1 antibodies extends the proliferative response of the regenerating liver, we conclude that TGF beta 1 plays a pivotal role in down regulating liver regeneration.
在四氯化碳损伤的大鼠肝脏中，转化生长因子β1（TGFβ1）基因表达增加。这种增加与肝脏再生之间的生物学联系尚未确立。
为了探究四氯化碳损伤后再生肝脏中产生TGFβ1的细胞的特性，我们用TGFβ1特异性核糖探针与未处理及四氯化碳处理的肝脏切片进行杂交，并同时对TGFβ1蛋白进行免疫定位。为了评估肝脏再生过程中细胞增殖的动态变化，还通过[3H]胸腺嘧啶核苷掺入和放射自显影监测细胞DNA合成的时间变化。通过将非实质细胞亚分为库普弗细胞/巨噬细胞、内皮细胞和贮脂细胞，并测定不同细胞类型中TGFβ1 mRNA水平，进一步扩展了原位杂交分析。最后，我们通过实验测试了TGFβ1表达的短暂升高与肝细胞增殖之间的时间关系是否存在因果关联。
我们观察到，DNA合成速率在处理后约36小时最高，早于TGFβ1转录本和蛋白积累增加的时间，二者均在约48小时达到峰值，随后下降。在中央静脉周围的炎性细胞浸润中可见TGFβ1基因表达的短暂上调，在门静脉区及坏死区附近的窦周细胞中上调程度较小。与TGFβ1转录本一样，TGFβ1蛋白也主要共定位在中央周围和门静脉周围细胞及其周围。在四氯化碳给药48小时后在肝脏中大量积聚的库普弗细胞是TGFβ1的主要产生者。向动物注射中和性抗TGFβ1抗体可阻止在72小时肝脏再生减弱阶段[3H]胸腺嘧啶核苷掺入的下降和细胞分裂。
基于我们的观察结果：（i）TGFβ1基因表达在肝脏再生的关键阶段被短暂触发；（ii）外源性添加的TGFβ1抑制肝脏DNA合成；（iii）给予TGFβ1抗体可延长再生肝脏的增殖反应，我们得出结论，TGFβ1在下调肝脏再生中起关键作用。
