Angiogenesis-related genes may be a more important factor than matrix metalloproteinases in bronchopulmonary dysplasia development

Abstract

We characterized the expression profile of angiogenesis-related genes (ARG) and matrix metalloproteinase (MMP) genes in preterm infants, with and without bronchopulmonary dysplasia (BPD). We reanalyzed a gene expression dataset for preterm infants from the Gene Expression Omnibus database using the Gene-Cloud of Biotechnology Information platform. A total of 1,652 genes were differentially (1.2-fold change) expressed: 811 were highly expressed in infants with BPD, and 841 were highly expressed in those without BPD. Twenty-eight and 11 ARGs were upregulated in infants with and without BPD, respectively. Among 27 detected MMPs and TIMPs, MMP8, MMP9, MMP25, TIMP2 and TIMP3 were differently expressed. Levels of THBS1, MMP8, MMP9, MMP25, TIMP2 and TIMP3 increased as severity of BPD and retinopathy of prematurity (ROP) increased, whereas ETS1, LEF1 and SPOCK2 exhibited the opposite trend. Expression of ETS1 and LEF1 had a fitting rate of R2 = 0.849 and P < 0.001. ELISAs showed a positive correlation between THBS1 and CD36 (receptor of THBS1) levels in serum samples from preterm infants. Our study indicates that the upregulation of THBS1 and downregulation of ETS1, LEF1 promotes BPD in preterm infants by disrupting blood vessel formation rather than by dysregulation of MMPs and TIMPs.

Keywords: MMPs; Pathology Section; THBS1; bronchopulmonary dysplasia; chronic lung disease; premature infant.

Figure 1. Graphs show ARGs expression in preterm infants

A. Heatmap shows differential expression genes in 294 samples (Brown: no-BPD infant samples, 112; Blue: BPD infant samples, 182). B. Volcano plot shows differential expression genes in BPD and no-BPD preterm infants (Fold change > 1.2, P < 0.05). C. Cluster analysis for 39 detected ARGs in 294 samples. (no = no-BPD; mi = mild BPD; mo = moderate BPD; se = severe BPD; act = activation; inh = inhibition) D. Fold change of 39 ARGs in BPD and no-BPD preterm infants.

Figure 2. The expression of ARGs, MMPs and TIMPs at different severity levels of BPD samples

A. The expression of 39 ARGs. THBS1 showed high expression activity. B. MMP8, MMP9 and TIMP1 exhibited high expression value.

Figure 3. Graphs show ANOVA of gene expression of THBS1, LEF1, ETS1, MMPS and TIMPs at different severity levels of BPD samples

Multiple comparisons were done by Tukey-Kramer, P < 0.05. Circles for means that are significantly different either do not intersect or intersect slightly, so that the outside angle of intersection is less than 90 degrees. If the circles intersect by an angle of more than 90 degrees, or if they are nested, the means are not significantly different. For BPD degree, 0 = no-BPD, 1 = mild BPD, 2 = moderate BPD, 3 = severe BPD.

Figure 4. Graphs show ANOVA of gene expression of THBS1, LEF1, ETS1, MMPS and TIMPs at different severity levels of ROP

Multiple comparisons were done by Tukey-Kramer, P < 0.05. 1 = no ROP, 2 = ROP not requiring treatment, 3 = ROP requiring laser therapy.

Figure 5. Graphs show the correlations of the genes as indicated with birth gestational age of the preterm infants

Figure 6. ELISA experiments show the levels of THBS1, CD36, MMP8 and MMP9

THBS1, CD36, and MMP9 were differently expressed in no-BPD and BPD samples, P < 0.05. For no-BPD, n = 32; for BPD, n = 45.