Yoorim Choi

SIRT1 directly regulates SOX2 to maintain self-renewal and multipotency in bone marrow-derived mesenchymal stem cells.

SOX2 is crucial for the maintenance of the self‐renewal capacity and multipotency of mesenchymal stem cells (MSCs); however, the mechanism by which SOX2 is regulated remains unclear. Here, we report that RNA interference of sirtuin 1 (SIRT1) in human bone marrow (BM)‐derived MSCs leads to a decrease of SOX2 protein, resulting in the deterioration of the self‐renewal and differentiation capacities of BM‐MSCs. Using immunoprecipitation, we demonstrated direct binding between SIRT1 and SOX2 in HeLa cells overexpressing SOX2. We further discovered that the RNA interference of SIRT1 induces the acetylation, nuclear export, and ubiquitination of SOX2, leading to proteasomal degradation in BM‐MSCs. SOX2 suppression by trichostatin A (TSA), a known histone deacetylase inhibitor, was reverted by treatment with resveratrol (0.1 and 1 µM), a known activator of SIRT1 in BM‐MSCs. Furthermore, 0.1 and 1 µM resveratrol reduced TSA‐mediated acetylation and ubiquitination of SOX2 in BM‐MSCs. SIRT1 activation by resveratrol enhanced the colony‐forming ability and differentiation potential to osteogenic and adipogenic lineages in a dose‐dependent manner. However, the enhancement of self‐renewal and multipotency by resveratrol was significantly decreased to basal levels by RNA interference of SOX2. These results strongly suggest that the SIRT1‐SOX2 axis plays an important role in maintaining the self‐renewal capability and multipotency of BM‐MSCs. In conclusion, our findings provide evidence for positive SOX2 regulation by post‐translational modification in BM‐MSCs through the inhibition of nuclear export and subsequent ubiquitination, and demonstrate that SIRT1‐mediated deacetylation contributes to maintaining SOX2 protein in the nucleus. Stem Cells 2014;32:3219–3231

Cell recruiting chemokine-loaded sprayable gelatin hydrogel dressings for diabetic wound healing.

UNLABELLED In this study, we developed horseradish peroxidase (HRP)-catalyzed sprayable gelatin hydrogels (GH) as a bioactive wound dressing that can deliver cell-attracting chemotactic cytokines to the injured tissues for diabetic wound healing. We hypothesized that topical administration of chemokines using GH hydrogels might improve wound healing by inducing recruitment of the endogenous cells. Two types of chemokines (interleukin-8; IL-8, macrophage inflammatory protein-3α; MIP-3α) were simply loaded into GH hydrogels during in situ cross-linking, and then their wound-healing effects were evaluated in streptozotocin-induced diabetic mice. The incorporation of chemokines did not affect hydrogels properties including swelling ratio and mechanical stiffness, and the bioactivities of IL-8 and MIP-3α released from hydrogel matrices were stably maintained. In vivo transplantation of chemokine-loaded GH hydrogels facilitated cell infiltration into the wound area, and promoted wound healing with enhanced re-epithelialization/neovascularization and increased collagen deposition, compared with no treatment or the GH hydrogel alone. Based on our results, we suggest that cell-recruiting chemokine-loaded GH hydrogel dressing can serve as a delivery platform of various therapeutic proteins for wound healing applications. STATEMENT OF SIGNIFICANCE Despite development of materials combined with therapeutic agents for diabetic wound treatment, impaired wound healing by insufficient chemotactic responses still remain as a significant problem. In this study, we have developed enzyme-catalyzed gelatin (GH) hydrogels as a sprayable dressing material that can deliver cell-attracting chemokines for diabetic wound healing. The chemotactic cytokines (IL-8 and MIP-3α) were simply loaded within hydrogel during in situ gelling, and wound healing efficacy of chemokine-loaded GH hydrogels was investigated in STZ-induced diabetic mouse model. These hydrogels significantly promoted wound-healing efficacy with faster wound closure, neovascularization, and thicker granulation. Therefore, we expect that HRP-catalyzed in situ forming GH hydrogels can serve as an injectable/sprayable carrier of various therapeutic agents for wound healing applications.

Different effects of resveratrol on early and late passage mesenchymal stem cells through β-catenin regulation.

Resveratrol is a sirtuin 1 (SIRT1) activator and can function as an anti-inflammatory and antioxidant factor. In mesenchymal stem cells (MSCs), resveratrol enhances the proliferation and differentiation potential and has an anti-aging effect. However, contradictory effects of resveratrol on MSC cultures have been reported. In this study, we found that resveratrol had different effects on MSC cultures according to their cell passage and SIRT1 expression. Resveratrol enhanced the self-renewal potential and multipotency of early passage MSCs, but accelerated cellular senescence of late passage MSCs. In early passage MSCs expressing SIRT1, resveratrol decreased ERK and GSK-3β phosphorylation, suppressing β-catenin activity. In contrast, in late passage MSCs, which did not express SIRT1, resveratrol increased ERK and GSK-3β phosphorylation, activating β-catenin. We confirmed that SIRT1-deficient early passage MSCs treated with resveratrol lost their self-renewal potential and multipotency, and became senescent due to increased β-catenin activity. Sustained treatment with resveratrol at early passages maintained the self-renewal potential and multipotency of MSCs up to passage 10. Our findings suggest that resveratrol can be effectively applied to early passage MSC cultures, whereas parameters such as cell passage and SIRT1 expression must be taken into consideration before applying resveratrol to late passage MSCs.

Synergistic Action of IL-8 and Bone Marrow Concentrate on Cartilage Regeneration Through Upregulation of Chondrogenic Transcription Factors

The objective of this study was to determine whether a biphasic scaffold loaded with a combination of a chemokine and bone marrow concentrate (BMC) could improve tissue regeneration in knee articular cartilage of beagles with cylindrical osteochondral defects. For this investigation, an osteochondral defect (6 mm in diameter and 8 mm deep) was created in the weight-bearing articular surface of the femoral medial condyle in beagles. Bone marrow was aspirated from the posterior iliac crests of beagles to obtain mesenchymal stem cells (MSCs) for in vitro assay. Hematoxylin and eosin (HE), Massons trichrome (MT), safranin O/fast green staining, and immunohistochemistry were performed for histological analysis. Quantitative real-time polymerase chain reaction was performed to understand the roles of BMC in chondrogenic differentiation of MSCs. At 12 weeks after transplantation of biphasic scaffolds, we observed that interleukin-8 (IL-8) or the combination of IL-8 and BMC induced massive bone regeneration compared to saline, BMC only, and MSCs. In gross appearance, the osteochondral defect site was nearly completely filled with repair tissue in the group that received the combination of IL-8 and BMC but not in the other groups. Moreover, histological analysis showed obvious differences in cartilage regeneration among groups. HE and MT staining showed that the cartilage defect sites of the group receiving the combination of IL-8 and BMC were regenerated with cartilage-like tissues showing chondrocyte morphology. Safranin O staining showed hyaline cartilage regeneration in the group receiving IL-8 and BMC, whereas fibrous-like tissues were formed in the other groups. Furthermore, immunostaining revealed the presence of type II collagen and aggrecan in regenerated cartilage tissue of the group receiving IL-8 and BMC, whereas regenerated cartilage tissues of the other groups weakly expressed type II collagen and aggrecan. These results indicate that the combination of a chemokine IL-8 and BMC has significant positive effects on osteochondral regeneration in a beagle model through enhancing expression of the chondrogenic transcription factors and markers such as Sox9 and type II collagen.

Triclosan Disrupts SKN-1/Nrf2-Mediated Oxidative Stress Response in C . elegans and Human Mesenchymal Stem Cells

Triclosan (TCS), an antimicrobial chemical with potential endocrine-disrupting properties, may pose a risk to early embryonic development and cellular homeostasis during adulthood. Here, we show that TCS induces toxicity in both the nematode C. elegans and human mesenchymal stem cells (hMSCs) by disrupting the SKN-1/Nrf2-mediated oxidative stress response. Specifically, TCS exposure affected C. elegans survival and hMSC proliferation in a dose-dependent manner. Cellular analysis showed that TCS inhibited the nuclear localization of SKN-1/Nrf2 and the expression of its target genes, which were associated with oxidative stress response. Notably, TCS-induced toxicity was significantly reduced by either antioxidant treatment or constitutive SKN-1/Nrf2 activation. As Nrf2 is strongly associated with aging and chemoresistance, these findings will provide a novel approach to the identification of therapeutic targets and disease treatment.

Effects of structurally stabilized EGF and bFGF on wound healing in type I and type II diabetic mice

Diabetes mellitus comprises a multiple metabolic disorder that affects millions of people worldwide and consequentially poses challenges for clinical treatment. Among the various complications, diabetic ulcer constitutes the most prevalent associated disorder and leads to delayed wound healing. To enhance wound healing capacity, we developed structurally stabilized epidermal growth factor (ST-EGF) and basic fibroblast growth factor (ST-bFGF) to overcome limitations of commercially available EGF (CA-EGF) and bFGF (CA-bFGF), such as short half-life and loss of activity after loading onto a matrix. Neither ST-EGF nor ST-bFGF was toxic, and both were more stable at higher temperatures than CA-EGF and CA-bFGF. We loaded ST-EGF and ST-bFGF onto a hyaluronate-collagen dressing (HCD) matrix, a biocompatible carrier, and tested the effectiveness of this system in promoting wound healing in a mouse model of diabetes. Wounds treated with HCD matrix loaded with 0.3 μg/cm2 ST-EGF or 1 μg/cm2 ST-bFGF showed a more rapid rate of tissue repair as compared to the control in type I and II diabetes models. Our results indicate that an HDC matrix loaded with 0.3 μg/cm2 ST-EGF or 1 μg/cm2 ST-bFGF can promote wound healing in diabetic ulcers and are suitable for use in wound dressings owing to their stability for long periods at room temperature. STATEMENT OF SIGNIFICANCE Various types of dressing materials loaded with growth factors, such as VEGF, EGF, and bFGF, are widely used to effect wound repair. However, such growth factor-loaded materials have several limitations for use as therapeutic agents in healing-impaired diabetic wounds. To overcome these limitations, we have developed new materials containing structurally stabilized EGF (ST-EGF) and bFGF (ST-bFGF). To confirm the wound healing capacity of newly developed materials (ST-EGF and ST-bFGF-loaded hyaluronate-collagen dressing [HCD] matrix), we applied these matrices in type I and type II diabetic wounds. Notably, these matrices were able to accelerate wound healing including re-epithelialization, neovascularization, and collagen deposition. Consequentially, these ST-EGF and ST-bFGF-loaded HCD matrix may be used as future therapeutic agents in patients with diabetic foot ulcers.

Metastatic extramammary Paget's disease with HER2 amplification to renal cell carcinoma: a unique presentation of cancer in cancer metastasis

nonatherosclerotic coronary artery. Eighty percent of spontaneous or primary coronary artery dissections occur in females with an age range between 25 and 60 years and most cases are sporadic. Most cases occur during pregnancy, pastpartum period, or are related to oral contraceptive pills. Although the exact pathophysiology of this rare condition remains unknown, it has been postulated that hormones, particularly progesterone, can cause weakening of the media. In addition, the stress of labour may lead to dissection of weakened vessels. On the other hand, gender differences do exist. For example, the right coronary dissections are more common in men, while left coronary dissections are more common in females. This leads to several reports suggesting a role for a cytokine-mediated action especially when an inflammatory cellular infiltrate is seen. But it remains uncertain whether these inflammatory changes are contributing to the dissection. No inflammatory infiltrate was seen in our case.

Enhanced articular cartilage regeneration with SIRT1-activated MSCs using gelatin-based hydrogel

To investigate the functional effects of resveratrol (RSV) on mesenchymal stem cells (MSCs), we treated MSCs with RSV continuously during ex vivo expansion. MSCs were continuously treated with RSV from passage (P) 0 to P5. A proliferative capacity of RSV-treated MSCs was higher than that of non-treated MSCs and similar with P1-MSCs. Continuous treatment of RSV on MSCs increased the stemness and inhibited the senescence. During chondrogenic differentiation in vitro, RSV-treated MSCs had higher differentiation potential and reduced hypertrophic maturation, which are limitations for hyaline cartilage formation. The histological analysis of micromass demonstrated increased chondrogenic differentiation potential. We further explored the therapeutic effectiveness of this method in a rabbit osteochondral defect model. A rabbit osteochondral defect model was established to investigate the hyaline cartilage regeneration potential of RSV-treated MSCs. Moreover, the cartilage regeneration potential of RSV-treated MSCs was greater than that of untreated MSCs. The expression levels of chondrogenic markers increased and those of hypertrophic markers decreased in RSV-treated MSCs compared with untreated MSCs. Sustained treatment of RSV on MSCs during ex vivo expansion resulted in the maintenance of stemness and enhanced chondrogenic differentiation potential. Consequentially, highly efficient MSCs promoted superior hyaline cartilage regeneration in vivo. This novel treatment method provides a basis for cell-based tissue engineering.

Enhancement of Mesenchymal Stem Cell-Driven Bone Regeneration by Resveratrol-Mediated SOX2 Regulation

Mesenchymal stem cells (MSCs) are an attractive cell source for regenerative medicine. However, MSCs age rapidly during long-term ex vivo culture and lose their therapeutic potential before they reach effective cell doses (ECD) for cell therapy. Thus, a prerequisite for effective MSC therapy is the development of cell culture methods to preserve the therapeutic potential during long-term ex vivo cultivation. Resveratrol (RSV) has been highlighted as a therapeutic candidate for bone disease. Although RSV treatment has beneficial effects on bone-forming cells, in vivo studies are lacking. The current study showed that long-term (6 weeks from primary culture date)-cultured MSCs with RSV induction retained their proliferative and differentiation potential despite reaching ECD. The mechanism of RSV action depends entirely on the SIRT1-SOX2 axis in MSC culture. In a rat calvarial defect model, RSV induction significantly improved bone regeneration after MSC transplantation. This study demonstrated an example of efficient MSC therapy for treating bone defects by providing a new strategy using the plant polyphenol RSV.

Discrepancies between Physiological and Psychological Measures of Stress Associated with Indoor Temperature

To assess stress levels associated with thermal comfort, this study measured stress levels in different Predicted Mean Vote (PMV) conditions using verbal vote, electroencephalographic (EEG), and salivary α-amylase assessments. This study was conducted in a climate chamber to regulate and experimentally manipulate PMV conditions. Environmental factors were set to 7 different PMV levels, from −3 to +3 by units. EEGs were measured for each subject using 8 electrodes covering the frontal, temporal, and parietal lobes, for 65 min for each PMV condition. Following EEG collection, saliva samples (for alpha (α)-amylase quantification) and a verbal report were gathered for each subject. The EEG and salivary α-amylase responses were similar, in that both tests showed the 0 to +2 conditions were relatively non-stressful compared to other conditions. On the other hand, the verbal reports indicated that the −1 to +1 conditions were relatively non-stressful.