## 4 Discussion  
The possibility that miRNA pathways (including their mRNA gene targets) are involved in the modulation of MS during the developmental age carries the chance to actively interfere with novel  
Figure 1: Graphical representation of miRNA-target genes interaction network using Cytoscape v3.7.2. The node intensity color is proportional to the log2 fold change values in the DE analysis (red: under-regulated; green: upregulated); the node size is proportional to the number of miRNA/mRNA connections. Please note that only downregulated genes were selected as targets of upregulated miRNAs (in the lower semicircle) and vice versa for downregulated miRNAs (in the upper semicircle). and selective therapeutic strategies in order to prevent detrimental effects due to the progression of the disease or its disabling symptoms like the cognitive impairment. In the same direction, genetic variants (SNPs) within the genes coding for suggestive miRNAs or located in a miRNA-binding site of a target gene were evaluated as well, following the suggestion that they may impact the \"normal\" miRNA functions [33]. The hypothesis that there may be a molecular signature associated with the cognitive dysfunctions also in PedMS is more than plausible [7]. Several pieces of evidence also reported significant changes of selective miRNA/mRNA expression under the treatment available for MS, such as IFN\(\beta\), one of the first approved DMTs since 1996, in the adult MS population [34]. These data, together with the numerous clinical evidences showing significant improvement of the MS cognitive performances under the IFN\(\beta\) therapy [35], suggested that novel therapeutic strategies should be considered, with the final aim to target the dysregulated molecular pathways possibly identified during the MS cognitive performances. Unfortunately, the small number of PedMS patients available for this further evaluation did not allow us to reach conclusive findings on this hypothesis, even in the evaluation of possible interference of the concomitant IFN\(\beta\) in both the transcriptomic and the cognitive profiles of the studied PedMS cohort. However, in our view, several useful pieces of information were provided as well. First of all, the neuropsychiatric evaluation showed that over an interval of 1-year, in the domains of attention and information processing speed, visual-spatial memory, executive functioning and expressive language, results were more compromised in the PedMS subjects than in the general MS population [36; 37]. It is also worthy to note that for some other cognitive tests, the follow-ups registered slight improvements in the correspondent functions, without any concomitant cognitive rehabilitation, confirming once more that the interval for performing longitudinal investigation should be longer to avoid any interferences due to learning curve processing, especially in younger MS patients, as reported in other investigations [38]. Looking at the molecular results, our data demonstrated that the two time points differed significantly in the expression of 13 miRNAs. Among them, it is worthwhile to note that the expressions of miR-182-5p and miR-320a(-3p) were preliminarily associated with cognitive dysfunctions in the original cohort of 19 PedMS patients [7], whereas those of miR-26b-5p, miR-192-5p, miR-451a, miR-486-5p and miR-576-5p were already mentioned in adult MS populations [4; 13; 19; 21]. Some of these significant miRNAs were reported jointly dysregulated in previous analyses, as they were part of common molecular pathways; this was observed, e.g., for miR-26b-5p, miR-182-5p and miR-451a in ALS [15]. Further investigations in larger sample sizes and possibly over a reasonably longer interval, as well as functional studies in MS and other neurodegenerative diseases, will shed light on the possibility that these significant miRNAs may be considered markers of some clinical changes over time.