Jeff Stogsdill and Dr. Paul Reynolds, Department of Physiology and Developmental Biology
The receptor for advanced glycation end-products (RAGE) is becoming an increasingly popular molecule of study after having been initially characterized in relation to a number of diseases such as diabetes, Alzheimer’s and atherosclerosis among others. It has recently been noted that RAGE is found at high quantities in lung diseases such as lung fibrosis, acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD) coupled with emphysema, yet the specific role it plays to date is unknown. In this research, RAGE has been conditionally over-expressed in the mouse lung in order to determine its contribution to pulmonary development and characterize the resulting phenotype.
RAGE over-expressing mouse pups were generated and allowed to progress through full gestation. It was noted that these pups did not survive past the first few hours of birth. Additional pups were created and removed half a day before birth in order to study the lung using histology. H&E staining of the lung revealed a significant decrease in tissue surface area as in the case of extreme COPD and emphysema (figure 1). Cell specific staining identified that certain lung cell types were diminished within the RAGE over-expressing lung. Specifically, alveolar type I cells, the cells that allow for proper oxygen and carbon dioxide exchange within the air sacs of the lung, were significantly decreased when compared to the wild type lung. This was confirmed by flow cytometry, showing that alveolar type I cells were significantly diminished per 10,000 cells in the distal lung compartment.
Ultra-magnification of the lung tissue was observed using electron microscopy. Both wild type and RAGE over-expressing lungs were viewed at greater than 2000X magnification (figure 2). Two key observations were noted. First, the basement membrane, the barrier between alveolar type 1 cells and the surrounding blood vessels were significantly disorganized in the RAGE mouse as compared to the wild type mouse. Second, a substantial number of alveolar type I cells viewed, showed a characteristic “blebbing” effect, typical of programmed cell death (apoptosis).
The results of these experiments show that RAGE, when over-expressed has both an underdeveloped and destructive effect on the lung. From these experiments, it was concluded that the over-expression of RAGE decreases alveolar type I cells and significantly decreases lung tissue surface area leading to postnatal death. The RAGE over-expresser can potentially be a good genetic model for the progression of certain lung diseases such as COPD. In addition, numerous hypotheses have been formed as a result of these experiments, stemming several future grant applications including the study of basement membrane destruction and improper balances between cell death and proliferation.
Data from the research funded by the ORCA grant was presented at a national Experimental Biology conference in Anaheim, California. A manuscript is under review for publication in a distinguished lung specific journal.