Intestinal ischemia-reperfusion injury causes activation of bone marrow-derived progenitor cells

INTRODUCTION: Bone marrow-derived circulating granulocyte and macrophage progenitor cells can contribute to the regeneration of ischemic tissue. Mobilization after heart or brain ischemia is well established, but it is unclear if this occurs after intestinal ischemia-reperfusion injury. Our aim was to evaluate bone marrow granulocyte-macrophage proliferation and the possible beneficial effect of recombinant human granulocyte-colony stimulating factor (rhG-CSF) in a model of intestinal ischemia-reperfusion. MATERIAL AND METHODS: After animal committee approval, anesthetized adult rats were divided into groups (n=4 per group) as follows: (i) control [C], (ii) 60 min intestinal ischemia [I], (iii) 60 min intestinal ischemia+360 min reperfusion [IR], (iv) 420 min sham operation [SH]. At sacrifice, bone marrow was removed, erythrocytes lysed and 1 50 000 nucleated cells plated in triplicate in 35 mm Petri dishes containing methylcellulose (MethoCult). After 11 days, granulocyte-macrophage colony-forming units (CFU-GM) were counted. In addition, to determine whether rhG-CSF injection stimulates progenitor cell activation, two further groups were studied: (v) 60 min intestinal ischemia+360 min reperfusion with injection of 50 microg/kg rhG-CSF at reperfusion [IR-G]; (vi) 420 min sham with rhG-CSF injected at 60 min [SH-G]. Data are expressed as median, range and IQR and compared using one-way ANOVA with Tukey's post-hoc test. RESULTS: Neither sham operation nor ischemia alone influenced the activation of bone marrow. However, IR caused a significant increase in bone marrow activation compared to control animals (p<0.01), ischemic animals (p<0.01) and sham operated animals (p<0.05). Administered at a dose of 50 microg/kg, which is commonly used in animal studies, rhG-CSF had no effect on bone marrow activation, and did not augment the effects of ischemia-reperfusion. At a higher dose (100 microg/kg), however, rhG-CSF resulted in the mortality of IR animals. CONCLUSIONS: Intestinal ischemia-reperfusion injury causes proliferation of bone marrow granulocyte-macrophage progenitors which contribute to long-term repair. This phenomenon is not augmented by the administration of exogenous rhG-CSF.