A Pilot Study Of The Role Of Eosinophil Progenitors In The Pathogenesis Of Eosinophilic Bronchitis

Background Eosinophilic bronchitis is one of the most common causes of chronic cough.It is characterized by eosinophilic airway inflammation and responds well to inhaled glucocorticosteroids.After treatment,sputum eosinophils could be reduced to normal level and re-elevated when relapse happen.Up to date,the pathogenesis of eosinophilic bronchitis remains unclear.Eosinophil is differentiated from eosinophil progenitors which is originated from hematopoietic progenitor cell.Majority of eosinophil progenitors differentiate into mature eosinophils in bone marrow and then release into peripheral blood.Recently,some studies showed that part of the eosinophil progenitors can migrate from bone morrow to circulation and be attracted to lung-homing directly,which induce airway inflammation in asthmatics by the in situ differentiation into eosinophils.However,whether in situ differentiation also plays a role in the airway inflammation of eosinophilic bronchitis remains unclear.Objective To investigate the levels of hematopoietic stem cells and eosinophil progenitors of sputum and peripheral blood in subjects with eosinophilic bronchitis by flow cytometry.A pilot study to explore the role of eosinophil progenitors in eosinophilic bronchitis.Method Patients with eosinophiic bronchitis and asthmatics,as well as the normal control of health subjects,were enrolled in this study.Sputum induction,fractional exhaled nitric oxide(Fe NO),serum total Ig E,spiromerty and bronchial provocation test,blood routine test were performed in all patients.Besides the differential cell counts,Sputum and peripheral blood sample would also used to detect the hematopoietic stem cell(HPC)and eosinophil progenitors(Eo P)by the flow cytometry.The level of HPC and Eo P after a four-week inhaled glucocorticosteroids therapy in patients were also record.Results 1.18 subjects with eosinophilic bronchitis,28 bronchial asthma(including 15 eosinophilic asthmatics/EA and 11 non-eosinophilic asthmatics/NEA)and 14 normal control subjects were enrolled.After a four-week inhaled glucocorticosteroids therapy,9 subjects with eosinophilic bronchitis and 16 asthmatics(including 10 EA and 6 NEA)provided enough sputum for follow visit.2.The eosinophil progenitors counts in airway(induced sputum)in EB patients [17(51)/ml] and asthmatics [87(250)/ml] were both significantly higher than that in the normal control [17(51)/ml](all P <0.05).No significant difference of sputum Eop level was found between EB and asthmatics(P>0.05).Besides,no significantly difference was found between EA and NEA(P>0.05).3.In circulation level,there was no significant difference of Eo P level in peripheral blood between eosinophilic bronchitis[70(115)/ml] and normal control[118(127)/ml](P >0.05).However,Eo P level in peripheral blood of asthmatics [113(154)/ml] and EA [121(156)/ml] had a increased tendency compared with that in EB(P=0.10 and P =0.08,respectively).4.After a four weeks inhaled glucocorticosteroids therapy,Eo P level in the sputum in EB decreased significantly as compared with the baseline[7(200)vs 91(256)/ml,P =0.05].However,no significant difference of Eo P level in peripheral blood in EB [76(143)vs 68(219)/ml,P>0.05] was found.In asthmatics,Eo P level was significantly decreased both in sputum and peripheral blood(all P <0.05)Conclusion 1.The Eo P level is increased in airway but not in circulation,which might play a potential role in the pathogenesis of eosinophilic bronchitis.2.In EB subjects,the eosinophilic inflammation may be predominantly localized in airway rather than system compared with asthmatics.