Transcriptional response of peripheral blood mononuclear cells to recombinant human growth hormone in a routine four-days IGF-I generation test

Abstract

Background: There are very few laboratory markers which reflect the biological sensitivity of children to recombinant human growth hormone (rhGH) treatment. Genome-wide transcriptional changes in peripheral blood mononuclear cells (PBMC) have been widely used as functional readout for different pharmacological stimuli.

Objective: To characterize transcriptional changes in PBMC induced by rhGH during a routine short-term IGF-I generation test (IGFGT) in children with growth disorders.

Materials and methods: Blood was obtained for IGF-I determination and RNA-preparation from PBMC of 12 children before and after 4days treatment with 30μgrhGH/kg body weight/day s.c. Transcriptional changes were assessed by cDNA-microarrays in the first six children. Selected genes were validated in all 12 cases by RT-qPCR.

Results: Serum IGF-I rose in all patients except one (p<0.0001), confirming biological response to rhGH. Unsupervised microarray data analysis in the first six children revealed 313 transcripts with abundant transcriptional changes but considerable inter-individual variability of response patterns. Many patients showed a large cluster of up-regulated genes, including EGR1, EGR2, FOS and to a lesser extent STAT2 and 5b. Exemplarily, EGR1, EGR2 and FOS data were independently reproduced by RT-qPCR. Gene ontology analysis revealed that pathways involved in cell proliferation and immune functions were significantly over represented.

Conclusion: The IGFGT is a suitable method for measuring reproducible and biologically conclusive transcriptional changes in PBMC. As our unsupervised data analysis strategy exposed a considerable inter-individual variability of response profiles a search for molecules of diagnostic and even prognostic value needs to be based on large long-term studies.