Soo Hyun Kim

Stem cell recruitment and angiogenesis of neuropeptide substance P coupled with self-assembling peptide nanofiber in a mouse hind limb ischemia model

For the successful treatment of ischemia, it is important to resupply sufficient blood into ischemic regions by inducing angiogenesis. Many stem cell transplantation studies have been reported to enhance angiogenesis, especially those relating to mesenchymal stem cells (MSCs); however cell transplantation has a number of limitations, such as the low rate of cell survival and donor cell shortage. In this study, we developed bioactive peptides by immobilizing substance P into self-assembling peptides, and their MSCs recruiting ability and therapeutic effects were evaluated by using ischemic hind limb models. Limb ischemia was produced in athymic mice, and 1% (wt/vol) peptides were injected into ischemic sites (n = 6 in each group: ischemia, substance P, RADA16-II, RADA16-II + substance P, and RADA16-II + RADA-SP (bioactive peptides)). The tissues were harvested for histological analysis and tissue perfusion measurement at 1, 3, 7, and 28 days after injection. We observed that bioactive peptides assembled themselves (<10 nm nanofibers) and formed 3-dimensional (3D) microenvironments within ischemic regions. In the animal study, it was observed that by applying bioactive peptides, substance P continued to be released at 28 days, and consequently, MSCs were successfully recruited into ischemic regions. Bioactive peptides could prevent fibrosis, promote neovascularization, enhance tissue perfusion, and prevent limb salvages. Our results demonstrated that bioactive peptides are one of the most powerful tools for the treatment of ischemia, through their recruitment of autologous MSCs and promotion of angiogenesis without cells transplantation.

Mental Health of Healthcare Workers who Experience Needlestick and Sharps Injuries

Mental Health of Healthcare Workers who Experience Needlestick and Sharps Injuries: Jang‐Wook Sohn, et al. Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, Korea University, Korea—Healthcare workers (HCWs) are exposed daily to the risk of injury by needlesticks and other medical instruments. However, the psychiatric impacts of such injuries have not been evaluated. The aim of this study was to evaluate the mental health status of HCWs with experiences of needlestick and sharps injuries. A cross‐sectional written survey was performed. The psychological symptoms before injury and current status were measured using the Beck Depression Inventory (BDI), Hamilton Anxiety Scale (HAM‐A) and Perceived Stress Scale (PSS). The proportions of HCWs with and without needlestick and sharps injuries were 71.1% (n=263) and 28.9% (n=107), respectively. HAM‐A and BDI scores were significantly higher among HCWs with injury experiences (p<0.01). HCWs with injury experiences exhibited higher PSS and BDI scores after the injury and higher levels of anxiety and depression. Particular attention should be directed towards the psychological consequences of needlestick and sharps injuries in HCWs.

The E3 Ubiquitin Ligase HOS1 Regulates Low Ambient Temperature-Responsive Flowering in Arabidopsis thaliana

Ubiquitin-dependent proteolysis regulates multiple aspects of plant growth and development, but little is known about its role in ambient temperature-responsive flowering. In addition to being regulated by daylength, the onset of flowering in many plants can also be delayed by low ambient temperatures. Here, we show that HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1), which encodes an E3 ubiquitin ligase, controls flowering time in response to ambient temperatures (16 and 23°C) and intermittent cold. hos1 mutants flowered early, and were insensitive to ambient temperature, but responded normally to vernalization and gibberellic acid. Genetic analyses suggested that this ambient temperature-insensitive flowering was independent of FLOWERING LOCUS C (FLC). Also, FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF) expression was up-regulated in hos1 mutants at both temperatures. The ft tsf mutation almost completely suppressed the early flowering of hos1 mutants at different temperatures, suggesting that FT and TSF are downstream of HOS1 in the ambient temperature response. A lesion in CONSTANS (CO) did not affect the ambient temperature-insensitive flowering phenotype of hos1-3 mutants. In silico analysis showed that FVE was spatiotemporally co-expressed with HOS1. A HOS1-green fluorescent protein (GFP) fusion co-localized with FVE-GFP in the nucleus at both 16 and 23°C. HOS1 physically interacted with FVE and FLK in yeast two-hybrid and co-immunoprecipitation assays. Moreover, hos1 mutants were insensitive to intermittent cold. Collectively, our results suggest that HOS1 acts as a common regulator in the signaling pathways that control flowering time in response to low ambient temperature.

Multiple-Objective Metric for Placing Multiple Base Stations in Wireless Sensor Networks

The placement of base stations in wireless sensor networks affects the coverage of sensor nodes, the tolerance against faults or attacks, the energy consumption and the congestion from communication. However, previous studies mostly focus on the placement of base stations to improve a partial property, not considering all of them. In this paper we propose multiple-objective metric (MOM), which reflects four different metrics for base station placement in wireless sensor networks. First, the ratio of sensor nodes which can communicate with a base station via either single-hop or multi-hop represents the coverage of sensor nodes. Second, the average ratio of sensor nodes after the failure of base stations represents the fault tolerance of a network. Third, the average distance between sensor nodes and their nearest base station represents the energy consumption of a network. Fourth, the standard deviation of the degree of base stations represents the average delay of a network due to congestion. We show that placing multiple base stations using our proposed MOM can fairly increase various properties of wireless sensor networks

Association between betatrophin/ANGPTL8 and non-alcoholic fatty liver disease: animal and human studies.

Betatrophin/angiopoietin-like protein 8 (ANGPTL8) is a liver-secreted protein recently identified as a potent stimulator of beta cell proliferation in mice. However, it is unclear how betatrophin is regulated in humans with non-alcoholic fatty liver disease (NAFLD). We investigated the role of betatrophin in mice and in humans with and without NAFLD. Serum betatrophin levels were examined by ELISA in 164 subjects, including 96 patients with NAFLD. Levels were significantly elevated in subjects with NAFLD compared with controls (1.301u2009±u20090.617u2009vs. 0.900u2009±u20090.574u2009μg/L, Pu2009<u20090.001), even after stratification by diabetic or obesity status. Circulating betatrophin positively correlated with obesity or glycemic indices, liver enzyme profiles, and NAFLD status, and was confirmed by multivariate regression analyses (βu2009=u20090.195, Pu2009=u20090.040). However, when including insulin resistance index in the model, the significant association between betatrophin level and NAFLD was diminished due to a mediation effect of insulin resistance on this relationship. Palmitate or tunicamycin increased betatrophin expression in HepG2 cells, while a chemical chaperone blocked its induction. Hepatic expression of betatrophin was elevated in mice with NAFLD including db/db or ob/ob mice and mice with a high-fat or methionine-choline deficient diet. In conclusion, circulating betatrophin was increased in mice and humans with NAFLD and its expression was induced by endoplasmic reticulum stress in hepatocytes (Clinical trial no. NCT02285218).

Stem cell recruitment, angiogenesis, and tissue regeneration in substance P-conjugated poly(l-lactide-co-ɛ-caprolactone) nonwoven meshes.

Recruitment of endogenous stem cells to impaired tissues holds enormous potential to regenerative medicine. In this study, we examined whether covalently conjugated substance P (SP) would significantly enhance the recruitment of stem cells and promote angiogenesis in poly(l-lactide-co-ε-caprolactone) (P(LA-co-CL)) meshes. SP was conjugated with star-shaped P(LA-co-CL) copolymer using carbonyldiimidazole chemistry. P(LA-co-CL) and SP-conjugated star-shaped P(LA-co-CL) copolymers were mixed in appropriate proportions and electrospun to fabricate nonwoven meshes. Amino acid analysis confirmed the conjugation of SP with star-shaped P(LA-co-CL) copolymers. Conjugated SP remained bioactive and recruited human bone-marrow-derived mesenchymal stem cells in an in vitro transwell migration assay. Moreover, SP was released in a sustained fashion from the nonwoven meshes for up to 30 days. P(LA-co-CL) as well as SP containing meshes were implanted subcutaneously in Sprague-Dawley rats (nu2009=u200916) for 14 and 21 days. Hematoxylin and eosin staining of the retrieved samples revealed cellularization of P(LA-co-CL) as well as SP containing meshes. Large and mature blood vessels were observed in greater numbers in SP-containing meshes compared with their control counterparts as revealed by Massons trichrome staining. We also observed a larger number of von Willebrand factor-positive vessels in SP-containing meshes than in the controls. Significantly large numbers of CD29- and CD90-positive stem cells were recruited in the meshes containing SP. Collectively, these findings suggest that the methodology presented may have broad applications in regenerative medicine, and these novel scaffolding materials can be used for in situ tissue regeneration of soft tissues.

Therapeutic effects of neuropeptide substance P coupled with self-assembled peptide nanofibers on the progression of osteoarthritis in a rat model.

Osteoarthritis (OA) is a progressively degenerative disease that is accompanied by articular cartilage deterioration, sclerosis of the underlying bone and ultimately joint destruction. Although therapeutic medicine and surgical treatment are done to alleviate the symptoms of OA, it is difficult to restore normal cartilage function. Mesenchymal stem cell (MSC) transplantation is one of the therapeutic trials for treating OA due to its potential, and many researchers have recently reported on the effects of MSCs associated with OA therapy. However, cell transplantation has limitations including low stem cell survival rates, limited stem cell sources and long-term exxa0vivo culturing. In this study, we evaluated the efficacy of neuropeptide substance P coupled with self-assembled peptide hydrogels in a rat knee model to prevent OA by mobilizing endogenous MSCs to the defect site. To assess the effect of the optimal concentration of SP, varying concentrations of bioactive peptides (substance P (SP) with self-assembled peptide (SAP)) were used to treat OA. OA was induced by unilateral anterior cruciate and medial collateral ligament transection of the knee joints. Forty rats were randomly allocated into 5 groups: SAP-0.5SP (17.5 μg of SP), SAP-SP group (35 μg of SP), SAP-2SP group (70 μg of SP), SAP-SP-MSC group, and control group. At 2 weeks post-surgical induction of OA, each mixture was injected into the joint cavity of the left knee. Histologic examination, immunofluorescence staining, quantitative real time-polymerase chain reaction and micro-computed tomography analysis were done at 6 weeks post-surgical induction. As shown by our results, the SAP-SP hydrogel accelerated tissue regeneration by anti-inflammatory modulation shown by an anti-inflammation test using dot-blot inxa0vitro. Additionally, the treatment of OA in the SAP-SP group showed markedly improved cartilage regeneration through the recruitment of MSCs. Thus, these cells could be infiltrating into the defect site for the regeneration of OA defects. In addition, from the behavioral studies on the rats, the number of rears significantly increased 2 and 4 weeks post-injection in all the groups. Our results show that bioactive peptides may have clinical potential for inhibiting the progression of OA as well as its treatment by recruiting autologous stem cells without cell transplantation.

Lotus-leaf-like structured heparin-conjugated poly(L-lactide-co-ɛ-caprolactone) as a blood compatible material

A heparin-conjugated biodegradable polymer was synthesized by direct coupling of heparin to poly(L-lactide-co-ɛ-caprolactone) (PLCL) and was manufactured into lotus-leaf-like structured films. We evaluated whether lotus-leaf-like structured heparin-conjugated PLCL (LH-PLCL) could be applied to blood vessel tissue engineering. Differences in the surface structures of the films with respect to hydrophobicity and the lotus effect as well as the antithrombotic efficiency in human whole blood were examined using scanning electron microscopy (SEM) and a contact angle meter. Recovery testing was conducted using a tensile strength testing machine, and quantitative analysis of conjugated heparin was performed using the toluidine blue colorimetric method. The concentration of conjugated heparin was 0.14 μg/mg H-PLCL, and the contact angle with the lotus-leaf-like surface was approximately 120°. Furthermore, the LH-PLCL film yielded a lower platelet adhesion rate (around less than 1.4%) in whole blood than that yielded by an untreated PLCL film. These results indicate a unique property of bound heparin and the lotus-leaf-like structure. This novel LH-PLCL polymer could be applied as a blood/tissue compatible biodegradable material for implantable medical devices and tissue engineering.

Covalent immobilization of stem cell inducing/recruiting factor and heparin on cell-free small-diameter vascular graft for accelerated in situ tissue regeneration

The development of cell-free vascular grafts has tremendous potential for tissue engineering. However, thrombus formation, less-than-ideal cell infiltration, and a lack of growth potential limit the application of electrospun scaffolds for in situ tissue-engineered vasculature. To overcome these challenges, here we present development of an acellular tissue-engineered vessel based on electrospun poly(L-lactide-co-ɛ-caprolactone) scaffolds. Heparin was conjugated to suppress thrombogenic responses, and substance P (SP) was immobilized to recruit host cells. SP was released in a sustained manner from scaffolds and recruited human bone marrow-derived mesenchymal stem cells. The biocompatibility and biological performance of the grafts were evaluated by in vivo experiments involving subcutaneous scaffold implantation in Sprague-Dawley rats (nu2009=u200912) for up to 4 weeks. Histological analysis revealed a higher extent of accumulative host cell infiltration, neotissue formation, collagen deposition, and elastin deposition in scaffolds containing either SP or heparin/SP than in the control groups. We also observed the presence of a large number of laminin-positive blood vessels, von Willebrand factor (vWF(+) ) cells, and alpha smooth muscle actin-positive cells in the explants containing SP and heparin/SP. Additionally, SP and heparin/SP grafts showed the existence of CD90(+) and CD105(+) MSCs and induced a large number of M2 macrophages to infiltrate the graft wall compared with that observed with the control group. Our cell-free grafts could enhance vascular regeneration by endogenous cell recruitment and by mediating macrophage polarization into the M2 phenotype, suggesting that these constructs may be a promising cell-free graft candidate and are worthy of further in vivo evaluation.

Effects of pulsatile bioreactor culture on vascular smooth muscle cells seeded on electrospun poly (lactide-co-ε-caprolactone) scaffold.

Electrospun nanofibrous scaffolds have several advantages, such as an extremely high surface-to-volume ratio, tunable porosity, and malleability to conform over a wide variety of sizes and shapes. However, there are limitations to culturing the cells on the scaffold, including the inability of the cells to infiltrate because of the scaffolds nano-sized pores. To overcome the limitations, we developed a controlled pulsatile bioreactor that produces static and dynamic flow, which improves transfer of such nutrients and oxygen, and a tubular-shaped vascular graft using cell matrix engineering. Electrospun scaffolds were seeded with smooth muscle cells (SMCs), cultured under dynamic or static conditions for 14 days, and analyzed. Mechanical examination revealed higher burst strength in the vascular grafts cultured under dynamic conditions than under static conditions. Also, immunohistology stain for alpa smooth muscle actin showed the difference of SMC distribution and existence on the scaffold between the static and dynamic culture conditions. The higher proliferation rate of SMCs in dynamic culture rather than static culture could be explained by the design of the bioreactor which mimics the physical environment such as media flow and pressure through the lumen of the construct. This supports regulation of collagen and leads to a significant increase in tensile strength of the engineered tissues. These results showed that the SMCs/electrospinning poly (lactide-co-ε-caprolactone) scaffold constructs formed tubular-shaped vascular grafts and could be useful in vascular tissue engineering.