Gene expression analysis after prenatal tracheal ligation in fetal rat as a model of stimulated lung growth.
OBJECTIVE
Prenatal tracheal occlusion or ligation (TL) has been proven to accelerate lung growth, but the mechanism of this is poorly understood. To increase understanding of the biological mechanisms involved in growth stimulation after TL in the fetal lung, we performed Global gene expression analysis using microarray technology.


METHODS
Sprague-Dawley rats underwent surgery on gestational day 19. After a small hysterotomy, the trachea was mobilized and tied. As controls, we used littermates to manipulated fetuses. On day 21, fetuses were removed and lungs harvested. Global gene expression analysis was performed using Affymetrix Platform and the RAE 230 set arrays (Affymetrix Inc, Santa Clara, Calif). For validation of microarray data, we performed real time polymerase chain reaction (PCR) of the most significant upregulated or downregulated genes, combined with immunohistochemical (IHC) analysis of lung sections.


RESULTS
In the group that underwent TL, several growth factors had an increased expression including connective tissue growth factor (CTGF), insulin-like growth factor 1 (IGF-1), and fibroblast growth factor 18 (FGF-18). Some of the genes that were downregulated in the group that underwent TL compared with controls were surfactant protein A (SP-A), apolipoprotein E (Apo-E), and phospholipase group II A2 (plg2a2). These results could be confirmed with real time PCR and IHC studies.


CONCLUSIONS
Tracheal occlusion or ligation is a well-documented stimulator of fetal lung growth, and the present study provides novel insights into the underlying molecular mechanisms, with increased expression of genes and proteins with growth factor activity. One of these growth factors, CTGF, has never been previously described in this model. Also, decreased levels of genes involved in surfactant metabolism were observed, providing molecular insights into the decreased surfactant production that is known to occur in TL. Increased understanding of the molecular mechanisms that control lung growth may be the key to develop novel therapeutic techniques to stimulate prenatal and/or postnatal lung growth.
Astrid Lindgren s Children Hospital, Division for Pediatric Surgery, Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Carmen
C
Mesas-Burgos
Magnus
M
Nord
Lukas
L
Didon
Ann-Christine
AC
Eklöf
Björn
B
Frenckner
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000032:analysis; D005260:Female; D005325:Fetal Organ Maturity / Q000235:genetics; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism*; D008026:Ligation; D008168:Lung / Q000196:embryology* / Q000254:growth & development; D023421:Models, Animal; D011247:Pregnancy; D011270:Pregnancy, Animal; D011663:Pulmonary Surfactants / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014132:Trachea / Q000601:surgery
D015415:Biomarkers; D018076:DNA, Complementary; D011663:Pulmonary Surfactants; C113569:fibroblast growth factor 18; D055513:Connective Tissue Growth Factor; D005346:Fibroblast Growth Factors; D007334:Insulin-Like Growth Factor I