We previously showed that PLN(Pancreatic-lymphnodes) of patients with T1D have CD4+CD25bright T-cells epigenetically imprinted to be regulatory(Tregs) but that do not function as such in-vitro. This functional defect is present only in Tregs residing in the PLN of T1D-patients and not in their PB(Peripheral-blood). MicroRNAs are small non-coding-RNAs that negatively regulate gene expression. We hypothesize that there might be post-transcriptional regulations in Tregs which may affect Tregs when residing in the PLN but not when circulating in the periphery of T1D-subjects.
CD4+CD25++CD127- Tregs were sorted from PLN and PB of 4 patients with T1D and from PLN and PB of 3 and 8 non-diabetic donors, respectively. From each sample, 200 sorted cells were analyzed and microRNA expression profiles were performed by using Taqman microRNAs arrays.
Specific microRNAs differentially expressed between Tregs residing in the PLN of T1D-patients and those in their PB or in PLN of non-diabetic donors were identified. Interestingly, we found 4 microRNAs with a particular expression pattern. Namely, miR-125a-5p, miR-642, and miR-155 were increased in Treg cells isolated from PLN as compared to those isolated from PB of T1D-patients. This differential expression was not identified in Tregs from PLN or PB of non-diabetic donors uncovering a tissue- and disease-specific microRNA expression pattern. In addition, miR-146a was increased in Tregs isolated from PLN as compared to those isolated from PB, both in T1D-patients and in non-diabetic donors suggesting a tissue specific microRNA expression pattern irrespective of the disease status. Several genes involved in Tregs function and migration were identified as predicted targets of miR-125a-5p and miR-642.
We revealed a miRNA signature specific for unfitted Tregs residing in the PLN of T1D-patients. This differential expression may explain functional defects of PLN-residing Treg-cells in T1D in repressing autoreactive T-cells. Studies are ongoing to confirm such a profile in nPOD donors.