Mobilization of peripheral blood hematopoietic stem cells following liver resection surgery.

Background/aims: Stem cells are characterized by plasticity, namely the ability of interchanging between various tissue and organs. In this regard, many studies have demonstrated the presence of antigenic structures relevant to the hematopoietic stem cell on hepatocytes, thus suggesting that in certain conditions liver cells may derive from the hematopoietic compartment. The aim of this study has been to verify whether surgical liver resection can activate bone marrow, by mobilizing peripheral blood hematopoietic stem cells (CD34+ cells) putatively able to induce liver repopulation.

Methodology: White blood cell and CD34+ cell count was determined at baseline (before surgery) and then monitored in the postoperative period in 13 patients undergoing liver resection (in most cases because of malignant, primary or secondary liver diseases) and, as a control group, in 12 patients affected with other diseases requiring abdominal surgery, but not liver resection. Moreover, to assess the basal value of circulating CD34+ cells, 50 healthy blood donors were included in the study. The CD34+ cell count has been carried out by flow cytometry, by applying conventional protocols.

Results: Patients, as altogether considered, showed at baseline a significantly higher white blood cell count as compared to healthy controls (7.41+/-2.89 x 10(3)/microL vs. 6.00+/-1.37 x 10(3)/microL, P<0.01), as opposed to the CD34+ cell count, the results of which were significantly lower (2.8+/-1.8/microL vs. 4.1+/-1.9/microL, P<0.01). The increase of CD34+ cells was significantly higher in patients following liver resection as compared to others (+6.5+/-4.1/microL vs. +0.7+/-1.4/microL, P<0.001), whereas the variation of white blood cell count was not statistically significant (+1.87+/-3.76 x 10(3)/microL vs. + 1.51+/-2.87 x 10(3)/microL).

Conclusions: Our results indicate that hepatic injury caused by extensive liver resection may constitute a trigger to the mobilization of hematopoietic stem cells putatively able to differentiate into hepatocytes, thus starting the recovery process of liver. These data could open innovative views to the treatment of certain liver diseases (e.g. fulminant hepatic failure), in particular by the administration of hematopoietic growth factors, such as G-CSF or GM-CSF, after the hepatic damage, to contribute, through the activation of the hematopoietic compartment, to a more efficient liver regeneration.