Relationship between bone marrow-derived CD34+ cells expressing interleukin-5 receptor messenger RNA and asthmatic airway inflammation

Background Asthma is clinically related with the degree of eosinophilic inflammation.How asthmatic airway inflammation is affected is still poorly understood. So the effects of bone marrow-derived hematopoietic cells expressing CD_ 34 (CD_ 34 ) and interleukin-5 (IL-5) receptor messenger RNA (IL-5R mRNA ) on asthmatic airway inflammation were investigated. Methods Balb/c mice were sensitized and challenged by ovalbumin (OVA) to establish an asthmatic model while control mice were sensitized and exposed to sterile saline. The mice were killed at different time points after being challenged by OVA and sterile saline. Then,bronchoalveolar lavage fluid (BALF),peripheral blood (PB) and bone marrow (BM) were prepared. Eosinophils in PB (PB_ EOS ) and BALF (BALF_ EOS ),nuclear cells in BALF,PB and BM were counted. By flow cytometry,the percentage of CD_ 34 cells to nucleated cells in PB,BM and the relative number of CD_ 34 cells in PB (PB_ CD34 ) and BM (BM_ CD34 ) were calculated. Immunocytochemistry and in situ hybridization were used to investigate the hematopoietic cells with co-localized expression of CD_ 34 and IL-5R mRNA in BM (BM_ CD34 _ IL-5R mRNA ). The percentage of BM_ CD34 _ IL-5R mRNA to BM_ CD34 was calculated. Results Twelve hours after challenge by OVA,BALF_ EOS and PB_ EOS in the experimental group were significantly higher than those in the control group ( P <0.01). Twenty-four hours after OVA challenge,BALF_ EOS ,PB_ EOS and BM_ CD34 _ IL-5R mRNA were elevated maximally,significantly different from those in the control group ( P <0.01). Forty-eight hours after OVA challenge,BALF_ EOS and BM_ CD34 _ IL-5R mRNA were still significantly higher than those of the controls ( P <0.01). The other markers reverted to normal. In 60 mice,BM_ CD34 _ IL-5R mRNA was closely correlated with the BAL_ EOS ,PB_ EOS ,BM_ CD34 and BM_ CD34 (%) ( P <0.05). Conclusions The amount of CD_ 34 cells expressing IL-5R mRNA increased in the BM of asthmatic model mice,which favors eosinophilopoiesis and eosinophilic airway inflammation. A signal pathway exists between the lungs and the bone marrow,which is involved in the initiation and maintenance of asthmatic airway inflammation.