## 3 Results
### Cellular Diagnostic Parameters and Biomarkers in Asthma
On the other hand, the function of metabolites in allergic disorders has recently attracted scientific interest. Several pathophysiological processes in allergic diseases are influenced by eicosanoids, which include thromokanes, leukotrienes, prostaglandandins, and lipoxins [55]. In addition, periostin is an extracellular matrix protein that exhibits surrogate indicators for T2 immunity and tissue remodeling, making it a useful diagnostic marker for the early identification of asthma [56; 57; 58]. According to transcriptomic analysis, chromosome 17q21 is of interest in genetic epidemiological studies of asthma because it contains important genes (_ORMDL3_, _GSDMB_, _LRRC3C_, _GSDMA_, _ZPBP2_, _IZF3_, _GRB7_, _ERBB2_, and _PGAP3_) and three single nucleotide polymorphisms (SNPs) (rs4794820, rs807631, and rs2872507) that are strongly associated with the pathogenesis and severity of asthma [26; 59]. However, a multitude of factors (innate and adaptive immune response, metabolic pathways, microbiome infections, epithelial barrier, genetic and epigenetic factors, remodeled resident cells, anatomical factors, exposure allergens, irritants, pollutant- and psychosocial factors) can induce or suppress certain genes or pathways and may play a role in the development of certain phenotypes and endotypes as well as in the control of asthma [25]. In addition, differential gene expression related to cytokines and transcription factors, as well as immunological response and elevation of numerous cellular processes, are influenced by DNA methylation [60] and histone modifications [61; 62; 63]. Therefore, searching for epigenetic markers is also essential to finding out asthma endotypes, phenotypes, individualized treatments, and prevention. Finally, over the past ten years, the interest in miRNAs has increased [26; 38; 64]. MiRNAs are short noncoding RNAs that behave as post-transcriptional negative regulators by inhibiting the translation of mRNA or initiating its degradation [65]. MiRNA levels in asthma have been correlated to the expression of the Th2 cytokines [66; 67] IL-5 [68], IL-13 [69], as well as the tissue remodeling factor VEGF [70], which are key molecules in asthma pathogenesis [38]. Recent research has revealed that most miRNAs are involved in Th1 and Th2 cytokine secretion, anti-inflammatory responses, macrophage polarization, T cell differentiation towards T2 response, and bronchial smooth muscle cell hyperplasia and hypertrophy [71]. miRNA profiles can be correlated to clinical traits, such as lung function, phenotype, and asthma severity [72]. Moreover, miRNAs have been shown to be signaling molecules released by cells and transported in extracellular vesicles such as exosomes [73; 74; 75]. According to previous studies [76], asthma is primarily characterized by the upregulation of miR-21 [77; 78; 79], miR-223 [80], miR-146a [78], miR-142-5p [81], miR-142-3p [82], miR-146b [83], and miR-155 [84], and downregulation of the let-7 family [85], miR-193b [86], and miR-375 [87; 88]. It has been shown that miR-155, miR-146a, miR-21,miR-1248, and miR-210 play key roles in controlling eosinophil and T cell activities as well as the release of Th2 cytokines (IL-4, IL-5, IL-13) [76]. However, for the use of miRNAs as biomarkers, they must be specific to each pathology, able to predict asthma phenotypes, and easy to detect in bodily fluids [38]. Therefore, clinical investigations may benefit from the expression of circulating miRNAs [36], because several of these miRNAs were found to distinguish asthmatic from non-asthmatic children [89] and adults [66; 67; 84; 90; 91; 92; 93], and rank asthma severity [94].