Espressione genica indotta dall'ormone somatotropo nei monociti di bambini sani e con deficit di GH

Abstract

Somatotropic hormone (GH) has transcriptional effects on the cells of many organs, directly by activating its receptor (GHR) or indirectly through induction of IGF-1 or other mediators. The presence of GHR in almost all cellular tissues makes GH action systemic even if, to date, still not well characterized. The immune system is among the districts where the effect of the somatotropic hormone is documented by mechanisms that are still poorly understood.The primary objective of this study is to determine the transcriptional effect of GH on peripheral blood monocytes. These cells were chosen for the significant expression of GHR on their surface and because they are easily accessible. Although the transcriptional response to somatotropic hormone is specific tissue, the study of the effects of GH on monocytes can serve as a model for other cell types and highlight differences between healthy subjects and those with GH deficiency (GHD).The diagnosis of GHD, during the developmental age, is classically based on the clinical evaluation associated with radiological and laboratory investigations (GH-IGF-1 axis stimulus test). Although provocation tests represent diagnostic gold standard, they have poor reproducibility and accuracy and are characterized by a considerable number of false positives and sometimes negatives.The secondary objective of this study is to identify differential transcriptional profiles between healthy subjects and with GHD.For this purpose, the gene expression of monocytes from healthy children and with GHD was compared in culture, under basal conditions and after stimulation with recombinant GH (rh-GH).Two groups of 12 subjects were selected, group S: healthy male children with normal height and growth rate and group D: children of the same sex and age and suffering from GHD, not yet in replacement therapy. Peripheral blood monocytes were purified by subtraction with monoclonal antibodies and the purity level was determined by laminar flow cytofluorimetry with monoclonal antibodies. Monocytes were grown for 24 hours with and without rh-GH. Total RNA was extracted and frozen until the analysis was performed simultaneously for all the experimental points using the Next Generation Sequencing methodology on Illumina platform. Differential expression of mRNA was analyzed by comparing the monocytes of healthy children and with GHD, stimulated in culture with rh-GH or not stimulated: GHD not stimulated (D-CNTR) vs healthy not stimulated (S-CNTR); healthy non-stimulated (S-CNTR) vs healthy stimulated (S-GH); non-stimulated GHD (D-CNTR) vs stimulated GHD (D-GH); GHD stimulated (D-GH) vs healthy stimulated (S-GH).The analysis between D-CNTR vs S-CNTR groups identified 58 genes with differential expression. Furthermore, 23 genes were modulated by GH in healthy children and 4 genes in children with GHD. Differential analysis between D-GH vs S-GH groups, on the other hand, identified 150 genes with differential expression.Finally, analysis performed by Ingenuity Pathway Analysis software showed a significant increase in NFAT immune pathways and dendritic cell maturation and a consistent increase in the expression of dendritic markers (HLA-A, HLA-C, CCR7) in monocytes of children with GHD compared to healthy children, after stimulation in culture with recombinant GH.In conclusion, the results of this study have demonstrated a clear transcriptional effect of GH on monocytes, direct and indirect through intermediate mediators, suggesting to evaluate the pro-inflammatory status of children with growth hormone deficiency more in depth.Furthermore, this study identified a gene expression profile of monocytes in children with GHD which, once verified in a larger number of patients, could represent an alternative to stimulus tests and guide the diagnosis of GH deficiency.Finally, our study opens future perspectives in order to identify a transcriptional profile or specific genes specific to GHD condition. [edited by Author]