There is emerging evidence that stem cells can rejuvenate damaged cells by mitochondrial transfer. Earlier studies show that epithelial mitochondrial dysfunction is critical in asthma pathogenesis. Here we show for the first time that Miro1, a mitochondrial Rho-GTPase, regulates intercellular mitochondrial movement from mesenchymal stem cells (MSC) to epithelial cells (EC). We demonstrate that overexpression of Miro1 in MSC (MSCmiro(Hi)) leads to enhanced mitochondrial transfer and rescue of epithelial injury, while Miro1 knockdown (MSCmiro(Lo)) leads to loss of efficacy. Treatment with MSCmiro(Hi) was associated with greater therapeutic efficacy, when compared to control MSC, in mouse models of rotenone (Rot) induced airway injury and allergic airway inflammation (AAI). Notably, airway hyperresponsiveness and remodeling were reversed by MSCmiro(Hi) in three separate allergen-induced asthma models. In a human in vitro system, MSCmiro(Hi) reversed mitochondrial dysfunction in bronchial epithelial cells treated with pro-inflammatory supernatant of IL-13-induced macrophages. Anti-inflammatory MSC products like NO, TGF-β, IL-10 and PGE2, were unchanged by Miro1 overexpression, excluding non-specific paracrine effects. In summary, Miro1 overexpression leads to increased stem cell repair.

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Dynamic variations in mitochondrial shape have been related to function. However, tools to automatically classify and enumerate mitochondrial shapes are lacking, as are systematic studies exploring the relationship of such shapes to mitochondrial stress. Here we show that during increased generation of mitochondrial reactive oxygen species (mtROS), mitochondria change their shape from tubular to donut or blob forms, which can be computationally quantified. Imaging of cells treated with rotenone or antimycin, showed time and dose-dependent conversion of tubular forms to donut-shaped mitochondria followed by appearance of blob forms. Time-lapse images showed reversible transitions from tubular to donut shapes and unidirectional transitions between donut and blob shapes. Blobs were the predominant sources of mtROS and appeared to be related to mitochondrial-calcium influx. Mitochondrial shape change could be prevented by either pretreatment with antioxidants like N-acetyl cysteine or inhibition of the mitochondrial calcium uniporter. This work represents a novel approach towards relating mitochondrial shape to function, through integration of cellular markers and a novel shape classification algorithm.

IL-10 is a key regulator of the immune system that critically determines health and disease. Its expression is finely tuned both at the transcriptional and posttranscriptional levels. Although the importance of posttranscriptional regulation of IL-10 has been previously shown, understanding the underlying mechanisms is still in its infancy. In this study, using a combination of bioinformatics and molecular approaches, we report that microRNA (hsamiR-106a) regulates IL-10 expression. The hsa-miR-106a binding site in the 3 UTR of IL10 has been identified by site-directed mutagenesis studies. Also, the involvement of transcription factors, Sp1 and Egr1, in the regulation of hsa-miR-106a expression and concomitant decrease in the IL-10 expression, has also been demonstrated. In summary, our results showed that IL-10 expression may be regulated by miR-106a, which is in turn transcriptionally regulated by Egr1 and Sp1.Egr1 ͉ IL-10 ͉ microRNA ͉ SP1 ͉ miR-106a promoter