Zerihun Negasi, PhD
Pulmonary and Clinical Care Medicine
Zerihun Hailemariam Negasi*, Mizanur Rahman, Yohannes A. Mebratu and Yohannes Tesfaigzi
Rationale: Cigarette smoking (CS) is a major inducer of chronic obstructive pulmonary disease (COPD) in humans. Due to its relevance in human disease, the present study was designed to establish a mouse model of COPD using H1N1 virus. Further, because quantification of emphysema is labor intensive, we developed a semi-automated rapid model to quantify emphysema.
Methods: C57BL/6 mice at 8-10 weeks were exposed to 150 mg/m3 CS particulate matter for 6 days/week, 2 hours/day, over 4 weeks. Following exposure to CS or room air (RA), mice were infected by intranasal instillation with the influenza A/California/07/2009 H1N1 strain (H1N1) at 500, 200, and 100 plaque forming units (PFU). Experimental groups exposed to RA+PBS, CS+PBS, RA+H1N1, and CS+H1N1 at 14 days post-infection were compared. Inflammation was evaluated in the right lungs after bronchoalveolar lavage, and emphysema was quantified from systematically taken random images of the hematoxylin- and eosin-stained tissue sections of the left lungs.
Results: Infection of mice with 500 pfu H1N1 caused extensive tissue inflammation and emphysema in both RA+H1N1 and CS+H1N1 groups. To minimize H1N1-induced tissue damage, we reduced the titer to 200 pfu and found significantly higher total leukocytes and macrophages in the CS+200H1N1 group. MLI was also increased in the RA+200H1N1 group compared with the RA+PBS, RA+H1N1, or CS+PBS groups. Further reduction of the H1N1 titers to 100 pfu resulted in CS+100H1N1 group still showing significantly more emphysema compared with the other three groups.
Conclusions: We describe an improved semi-automated MLI method that drastically reduced the time required to process and measure air space enlargement. Further, we have established a mouse model of COPD that uses a human-relevant virus to cause emphysema. These results suggest that CS sensitizes the lungs to influenza-induced injury at much lower virus titers.
Funding source: RO1HL068111 and R01HL140839
Cigarette smoking (CS) is a major inducer for chronic obstructive pulmonary disease (COPD) in humans, and mice exposed to CS for 6 months are generally used as a model to study this disease.
Due to its relevance in human disease, the present study was designed to establish a model using H1N1 virus. Further, because quantification of emphysema is labor intensive, we developed a semi-automated rapid model to quantify emphysema.
Developing an improved method for quantifying emphysema and establishing an appropriate mouse model of emphysema are paramount in exploring the mechanism of COPD and represent a critical approach in deciding possible future human therapeutics.