Hypoxia enhances the proliferation and migration of adipose-derived stem cells (ASCs) via the generation of reactive oxygen species (ROS). Therefore, this study primarily investigated whether or not ROS generation could regulate microRNA-210 (miR-210) expression, and increase proliferation/migration of ASCs. In addition, we tried to identify the signaling pathways involved in miR-210 upregulation and the direct target genes of miR-210 that mediate these functions. Various sources of ROS generation such as hypoxia, antimycin, rotenone, and platelet-derived growth factor (PDGF)-BB upregulated miR-210 expression, and increased the proliferation/migration of ASCs. There is a positive feed-forward loop between ROS generation and miR-210, and miR-210 itself increases ROS generation by downregulation of iron–sulfur cluster scaffold homolog 2 (ISCU2). Although hypoxia-inducible factor-1α was not involved in miR-210 expression, pharmacological or small interfering RNA (siRNA)-driven inhibition of Akt and ERK1/2 molecules reduced miR-210 expression. Transfection of siRNAs of NF-κB and Elk1 also reduced miR-210 expression, indicating that these signaling pathways mediate miR-210 upregulation. Protein tyrosine phosphatase, non-receptor type 2 (PTPN2) was selected for miR-210 target gene, and it was downregulated by ROS generators or miR-210 mimic treatment. PTPN2 was first proven to be a direct miR-210 target in luciferase activity assay, and pharmacological inhibition or overexpression of PTPN2 regulated the proliferation and migration of ASC. In conclusion, ROS generation from diverse sources induces miR-210 expression in ASCs via PDGFR-β, Akt and ERK pathways. Transcription of miR-210 expression is regulated by NF-κB and Elk1, and miR-210 increases the proliferation and migration of ASCs via ISCU2 and PTPN2 downregulation.

We have previously demonstrated that hypoxia stimulates adipose-derived stem cells (ASCs) through the generation of reactive oxygen species (ROS). However, the precise mechanism involved in the ROS generation by ASCs is not well understood. We sought to investigate in this work: (1) which subtype of NADPH oxidase (Nox) is primarily expressed in ASCs; (2) where Nox4 is localized in ASCs; and (3) whether silencing of Nox4 attenuates hypoxia-enhanced function of ASC. We used 2′,7′-dichlorofluorescin diacetate (DCF-DA) as an indicator of ROS generation and found that the fluorescence intensity of DCF-DA was significantly increased after hypoxia exposure (2% oxygen). In addition, hypoxia enhanced the proliferation and migration of ASCs and upregulated the mRNA expression of Oct4 and Rex1. Quantitative analysis of mRNA expression of Nox family in ASCs demonstrated that Nox4 is primarily expressed in ASCs, while immunofluorescence assay showed that Nox4 is mainly localized in the perinuclear region and overlaps with Mitotracker, a mitochondria marker. Silencing of Nox4 by siRNA treatment downregulated the RNA and protein expression of Nox4, which significantly reduced the ROS generation under hypoxia. In addition, Nox4 silencing significantly reduced the proliferation and migration of ASCs and downregulated the mRNA expression of Oct4 and Rex1. Phosphorylation of platelet-derived growth factor receptor-β, AKT, and ERK1/2 also diminished following Nox4 silencing. In a nutshell, these results suggest that Nox4 is primarily expressed in ASCs and plays a pivotal role in the hypoxia-enhanced stimulation of ASCs.

Several lines of evidence suggest that VEGF is a key regulator of the paracrine effects of adipose-derived stem cells (ASCs), but the mechanism of action remains to be identified. This brief review discusses the following research questions: i) Does VEGF increase the proliferation/migration and differentiation of ASCs?; ii) Does VEGF mediate the paracrine effects of ASCs?; and iii) How is VEGF synthesized, and which factors regulate VEGF secretion? External stimuli such as hypoxia may activate receptor tyrosine kinases in the membrane of ASCs, which, in turn, phosphorylate extracellular signal regulated kinase (ERK) and members of the Akt signaling pathway, stabilizing hypoxia inducible factor 1α (HIF-1α) that are primary regulators of VEGF expression. Secreted VEGF directly stimulates ASCs via VEGF receptors in an autocrine manner and regenerates damaged neighboring cells in a paracrine manner. Most studies of stem cell regeneration have focused on differentiation of ASCs and their building block function; however, the paracrine effects of ASCs should also be the focus of attention.

Since April 2015, post-mastectomy breast reconstruction has been covered by the Korean National Health Insurance Service (NHIS). The frequency of these procedures has increased very rapidly. We analyzed data obtained from the Big Data Hub of the Health Insurance Review and Assessment Service (HIRA) and determined annual changes in the number of breast reconstruction procedures and related trends in Korea. We evaluated the numbers of mastectomy and breast reconstruction procedures performed between April 2015 and December 2018 using data from the HIRA Big Data Hub. We determined annual changes in the numbers of total, autologous, and implant breast reconstructions after NHIS coverage commenced. Data were analyzed using Microsoft Excel. The post-mastectomy breast reconstruction rate increased from 19.4% in 2015 to 53.4% in 2018. In 2015, implant reconstruction was performed in 1,366 cases and autologous reconstruction in 905 (60.1% and 39.8%, respectively); these figures increased to 3,703 and 1,570 (70.2% and 29.7%, respectively) in 2018. Free tissue transfer and deep inferior epigastric perforator flap creation were the most common autologous reconstruction procedures. For implant-based reconstructions, the rates of directto-implant and tissue-expander breast reconstructions (first stage) were similar in 2018. This study summarizes breast reconstruction trends in Korea after NHIS coverage was expanded in 2015. A significant increase over time in the post-mastectomy breast reconstruction rate was evident, with a trend toward implant-based reconstruction. Analysis of data from the HIRA Big Data Hub can be used to predict breast reconstruction trends and convey precise information to patients and physicians.