Laser microdissection allows detection of abnormal gene expression in cystic adenomatoid malformation of the lung

Abstract

Background/Purpose Congenital cystic adenomatoid malformation (CCAM) of the lung may result from a localized aberrant epithelial-mesenchymal interaction during lung development. We used laser microdissection (LMD) to isolate the epithelium and mesenchyme of CCAM, and studied candidate gene expression in these pure cell populations. Methods Congenital cystic adenomatoid malformation tissue was obtained from fetal (n = 5) and postnatal (n = 5) surgical specimens. Normal fetal lung (n = 10) was obtained from abortus material, and normal postnatal lung (n = 5) was identified from surgical specimens. Whole tissue was analyzed using immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Using LMD, columnar bronchiolar type epithelium and underlying mesenchyme were isolated. Multiplex nested RT-PCR was then used to detect message levels of candidate genes. Results Reverse transcriptase polymerase chain reaction performed on LMD-isolated tissue, but not whole tissue homogenate, revealed differences between CCAM and normal lung. In this report, we focus on the fibroblast growth factor (FGF) family. By RT-PCR, there was 4-fold more epithelial expression of FGF9 in fetal CCAM vs normal fetal lung ( P < .07). This was qualitatively confirmed by immunohistochemistry. We also detected decreased FGF7 expression in CCAM mesenchyme ( P < .05) but no significant differences in FGF10 or FGFR2. Conclusions LMD may be used to overcome the limitations of tissue heterogeneity in the study of CCAM. Abnormal growth factor expression may play a role in the etiology of this lesion.