Global gene expression patterns in the post-pneumonectomy lung of adult mice

Abstract

Background: Adult mice have a remarkable capacity to regenerate functional alveoli following either lung resection or injury that exceeds the regenerative capacity observed in larger adult mammals. The molecular basis for this unique capability in mice is largely unknown. We examined the transcriptomic responses to single lung pneumonectomy in adult mice in order to elucidate prospective molecular signaling mechanisms used in this species during lung regeneration.

Methods: Unilateral left pneumonectomy or sham thoracotomy was performed under general anesthesia (n = 8 mice per group for each of the four time points). Total RNA was isolated from the remaining lung tissue at four time points post-surgery (6 hours, 1 day, 3 days, 7 days) and analyzed using microarray technology.

Results: The observed transcriptomic patterns revealed mesenchymal cell signaling, including up-regulation of genes previously associated with activated fibroblasts (Tnfrsf12a, Tnc, Eln, Col3A1), as well as modulation of Igf1-mediated signaling. The data set also revealed early down-regulation of pro-inflammatory cytokine transcripts and up-regulation of genes involved in T cell development/function, but few similarities to transcriptomic patterns observed during embryonic or post-natal lung development. Immunohistochemical analysis suggests that early fibroblast but not myofibroblast proliferation is important during lung regeneration and may explain the preponderance of mesenchymal-associated genes that are over-expressed in this model. This again appears to differ from embryonic alveologenesis.

Conclusion: These data suggest that modulation of mesenchymal cell transcriptome patterns and proliferation of S100A4 positive mesenchymal cells, as well as modulation of pro-inflammatory transcriptome patterns, are important during post-pneumonectomy lung regeneration in adult mice.

Figure 1

Illustrations of the top gene networks for the time-independent microarray analysis. A - Most significant network for the time-independent microarray analysis (score = 56). B - Second most significant network for the time-independent microarray analysis (score = 45).

Figure 2

Illustrations of the top gene networks at the 6 hour time point of the time-dependent microarray analysis. A - most significant gene network (score = 38). B - second most significant network (score = 36).

Figure 3

Illustrations of the top gene networks at the 1 day time point of the time-dependent microarray analysis. A - most significant gene network (score = 42). B - second most significant network (score = 38).

Figure 4

Illustrations of the top gene networks at the 3 day time point of the time-dependent microarray analysis. A - most significant gene network (score = 57). B - second most significant network (score = 45).

Figure 5

Illustrations of the top gene networks at the 7 day time point of the time-dependent microarray analysis. A - most significant gene network (score = 48). B - second most significant network (score = 42).

Figure 6

Topography of S100A4/BrdU double positive alveolar cells. Photomicrographs (630× magnification) of double positive staining cells, with S100A4 (green), BrdU (red) and nuclei (blue).

Figure 7

Percentage of nucleated cells that stained positive for either S100A4, BrdU or double positive for S100A4 and BrdU. Data are mean values ± SE. *P < 0.05 between PNY and SHAM for a given time point.

Figure 8

Topography of αSMA positive cells 7 days after pneumonectomy. Photomicrograph (400× magnification) with αSMA (green), BrdU (red) and nuclei (blue), illustrating αSMA staining around a vessel, but not in surrounding alveoli or associated with BrdU positive cells. Similar results were seen at 3 days after pneumonectomy and in sham-operated animals (results not shown).