Bonding of Flexible Membranes for Perfusable Vascularized Networks Patch.

BACKGROUND: In vitro generation of three-dimensional vessel network is crucial to investigate and possibly improve vascularization after implantation in vivo. This work has the purpose of engineering complex tissue regeneration of a vascular network including multiple cell-type, an extracellular matrix, and perfusability for clinical application. METHODS: The two electrospun membranes bonded with the vascular network shape are cultured with endothelial cells and medium flow through the engineered vascular network. The flexible membranes are bonded by amine-epoxy reaction and examined the perfusability with fluorescent beads. Also, the perfusion culture for 7 days of the endothelial cells is compared with static culture on the engineered vascular network membrane. RESULTS: The engineered membranes are showed perfusability through the vascular network, and the perfused network resulted in more cell proliferation and variation of the shear stress-related genes expression compared to the static culture. Also, for the generation of the complex vascularized network, pericytes are co-cultured with the engineered vascular network, which results in the Collagen I is expressed on the outer surface of the engineered structure. CONCLUSION: This study is showing the perfusable in vitro engineered vascular network with electrospun membrane. In further, the 3D vascularized network module can be expected as a platform for drug screening and regenerative medicine.

Transplantation of human corneal limbal epithelial cell sheet harvested on synthesized carboxymethyl cellulose and dopamine in a limbal stem cell deficiency.

This study aimed to evaluate the efficacy and safety of transplantation with human corneal limbal epithelial (HCLE) cell sheets cultured on carboxymethyl cellulose (CMC)-dopamine (DA)-coated substrates and harvested via enzymatic digestion of CMC with cellulase in a rabbit animal model of limbal stem cell deficiency (LSCD). Synthesized CMC-DA was pretreated onto the surface of culture plates. Then, HCLE cells were cultured on precoated CMC-DA and HCLE cell sheets were harvested using cellulase-containing cell culture medium. HCLE cell sheets were evaluated using a live/dead assay, histological examination, and immunofluorescence staining. For in vivo assessment, HCLE cell sheets were transplanted in a rabbit model of LSCD for 2 weeks to determine the effectiveness of the repair. Primary culture of HCLE cells stained positively for p63, cytokeratin (CK)15, and CK12. HCLE cell sheets were generated with a well-preserved morphology and transparency ranging in size from 15 to 19 mm after cellulase-assisted cell sheet generation. HCLE cell sheets uniformly stained positively for human mitochondria, p63, CK15, CK12, CK3/2p, and zonula occludens (ZO)-1. HCLE cell sheet transplantation in a rabbit model of LSCD improved the corneal opacity and neovascularization scores. Transplanted HCLE cell sheets stained positively for p63 and CK12. Transplantation of HCLE cell sheets harvested on CMC-DA coating combined with cellulase is a safe and efficient procedure for corneal epithelial regeneration in a rabbit model of LSCD. This system could enable a promising strategy to regenerate corneal epithelium by transplantation in ocular surface disorders.

Association between exposure to traffic-related air pollution and pediatric allergic diseases based on modeled air pollution concentrations and traffic measures in Seoul, Korea: a comparative analysis.

BACKGROUND: Pediatric allergic diseases are a major public health concern, and previous studies have suggested that exposure to traffic-related air pollution (TRAP) exposure is a risk factor. These studies have typically assessed TRAP exposure using traffic measures, such as distance to major roads, or by modeling air pollutant concentrations; however inconsistent associations with pediatric allergic diseases have often been found. Using road proximity and density, we previously found an association between TRAP and atopic eczema among approximately 15,000 children living in Seoul, Korea, heavily populated and highly polluted city in which traffic is a major emission source. We aimed to conduct a parallel analysis using modeled air pollution concentrations and thus examine the consistency of the association. Specifically, we examined the associations of individual-level annual-average concentrations of NO2, PM10, and PM2.5 with symptoms and diagnoses of three pediatric allergic diseases including asthma, allergic rhinitis, and atopic eczema. METHODS: The study population included 14,614 children from the Seoul Atopy Friendly School Project Survey in Seoul, Korea, in 2010. To assess individual exposures to TRAP among these children, we predicted annual-average concentrations of NO2, PM10, and PM2.5 at the children's home addresses in 2010 using universal kriging and land use regression models along with regulatory air quality monitoring data and geographic characteristics. Then, we estimated odds ratios (ORs) of the three allergic diseases for interquartile increases in air pollution concentrations after adjusting for individual risk factors in mixed effects logistic regression. RESULTS: Symptoms and diagnoses of atopic eczema symptoms showed an association with NO2 (OR = 1.07, 95% confidence interval = 1.02-1.13; 1.08, 1.03-1.14) and PM10 (1.06, 1.01-1.12; 1.07, 1.01-1.13). ORs of PM2.5 were positive but not statistically significant (1.01, 0.95-1.07; 1.04, 0.98-1.10). No association was found between asthma and allergic rhinitis, although PM2.5 showed a marginal association with allergic rhinitis. CONCLUSIONS: Our consistent findings regarding the association between TRAP and the prevalence of atopic eczema using traffic measures and surrogate air pollutants suggested the effect of TRAP on children's health. Follow-up studies should elucidate the causal link, to support subsequent policy considerations and minimize adverse health effects in children.

Coaxial bioprinting of cell-laden vascular constructs using a gelatin-tyramine bioink.

Herein, three-dimensional (3D) bioprinting of engineered constructs with cell-laden biomaterials was investigated for the development of 3D tissue constructs in vitro. The present article proposes a simple coaxial-nozzle-based printing method using a one-step gelling gelatin bioink containing different cell types for vascular structure generation. First, a gelatin bioink prepolymer with a tyramine functional group was synthesized. To facilitate rapid gelation, polyethylene glycol (PEG) was introduced as a spacer between gelatin and tyramine. The gelatin-PEG-tyramine (GPT) prepolymer underwent enzymatic crosslinking, which yielded a higher gelation rate of up to 4.24 ± 0.08 s. Second, one-step bioprinting of a cell-laden tubular structure was demonstrated using a coaxial type extruder and the GPT bioink with human umbilical vein endothelial cells (HUVECs) with or without human dermal fibroblasts (HDFs). The printed no-cell GPT tube was demonstrated to possess a perfusable vascular structure. The extruded tube with HUVECs-in-GPT sheath configuration resulted in an endothelial cell-lined hollow structure and was maintained for up to 8 days in vitro. Additionally, the coaxially extruded tube with HUVECs-in-core (gelatin) and HDFs-in-GPT sheath (GPT) configuration exhibited a distribution of these two cell types along the tube axis. In the current study, it was demonstrated that a radial distribution of multiple vascular cells can be simply achieved using a synthetic GPT bioink combined with a coaxial nozzle printing system, serving as a proof-of-concept for one-step generation of vascular constructs. The rapid gelling bioink prepolymer, in combination with a coaxial bioprinter nozzle mechanism, has great potential for the development of designed, printed, and organized 3D tissue architecture vascularization.

In vitro lung cancer multicellular tumor spheroid formation using a microfluidic device.

The purpose of this study was to demonstrate self-organizing in vitro multicellular tumor spheroid (MCTS) formation in a microfluidic system and to observe the behavior of MCTSs under controlled microenvironment. The employed microfluidic system was designed for simple and effective formation of MCTSs by generating nutrient and oxygen gradients. The MCTSs were composed of cancer cells, vascular endothelial cells, and type I collagen matrix to mimic the in vivo tumor microenvironment (TME). Cell culture medium was perfused to the microfluidic device loaded with MCTSs by a passive fluidic pump at a constant flow rate. The dose response to an MMPs inhibitor was investigated to demonstrate the effects of biochemical substances. The result of long-term stability of MCTSs revealed that continuous perfusion of cell culture medium is one of the major factors for the successful MCTS formation. A continuous flow of cell culture medium in the in vitro TME greatly affected both the proliferation of cancer cells in the micro-wells and the sustainability of the endothelial cell-layer integrity in the lumen of microfluidic channels. Addition of MMP inhibitor to the cell culture medium improved the stability of the collagen matrix by preventing the detachment and shrinkage of the collagen matrix surrounding the MCTSs. In summary, the present constant flow assisted microfluidic system is highly advantageous for long-term observation of the MCTS generation, tumorous tissue formation process and drug responses. MCTS formation in a microfluidic system may serve as a potent tool for studying drug screening, tumorigenesis and metastasis.

Embossed Membranes with Vascular Patterns Guide Vascularization in a 3D Tissue Model.

The vascularization of three-dimensional (3D) tissue constructs is necessary for transporting nutrients and oxygen to the component cells. In this study, a vacuum forming method was applied to emboss a vascular pattern on an electrospun membrane so that guided vascular structures could develop within the construct. Two- or six-layer constructs of electrospun membranes seeded with endothelial cells and pericytes were stacked and subcutaneously implanted into mice. Blood vessel formation in the implanted constructs with six alternating layers of flat membranes and membranes embossed with a blood vessel pattern was observed after two weeks of implantation. The formation of blood vessels was observed along the embossed blood vessel pattern in the structure of the embossed membrane laminated at four weeks and eight weeks. Vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang-1) were highly expressed in the vascularized structures. Therefore, we demonstrated that a structure capable of producing a desired blood vessel shape with electrospun membranes embossed with a blood vessel pattern can be manufactured, and that a variety of structures can be manufactured using electrospun membranes in the tissue engineering era.

Conjugation of carboxymethyl cellulose and dopamine for cell sheet harvesting.

In this study, we investigated the feasibility of enzymatic digestion of polysaccharides for cell sheet harvesting. Cellulose was digested using cellulase; in brief, cellulose was pre-coated under a confluent cell layer, and then enzymatic digestion of cellulose under the confluent cell layer enabled cell detachment with minimal cell damage, yielding cell sheets. For the surface adhesion of the cellulose, carboxymethyl cellulose (CMC) molecules were conjugated with dopamine (DA), and the synthesized CMC-DA was pre-treated onto the surface of the culture plates. Then, human mesenchymal stem cells (hMSCs) or corneal limbal epithelial cells (hCLEs) were cultured on the pre-coated CMC-DA and harvested using cellulase containing cell culture medium. Single hMSCs treated with cellulase showed higher proliferative activity, showing an aggregated morphology compared with trypsin-treated hMSCs. Additionally, hMSC sheets were detached from the pre-coated CMC-DA surface 10 min after cellulase treatment. Also, hCLE sheets were generated with a well-preserved morphology and transparency after cellulase-assisted cell sheet generation. These results demonstrate that the strategy of CMC-DA coating combined with cellulase enzymatic harvesting is an effective option for harvesting cell sheets.

Human Conjunctival Epithelial Sheets Grown on Poly(Lactic-Co-Glycolic) Acid Membranes and Cocultured With Human Tenon's Fibroblasts for Corneal Repair.

Purpose: We determine the feasibility of human conjunctival epithelial cells (hCjECs) on poly(lactic-co-glycolic) acid (PLGA) membranes for corneal epithelium regeneration. hCjECs on PLGA or polyester (PET) membranes with or without coculture of human Tenon's fibroblasts (hTFs) were compared in vitro, and to determine whether epithelial sheets grown on PLGA membranes can repair injured rabbit corneal epithelium by transplantation for 2 weeks in vivo. Methods: Primary hCjECs were cultured on PLGA or the original PET membrane-based transwell inserts with or without coculture of hTFs on the floor of the culture plate. Cell behaviors, such as proliferation and differentiation, were compared. For in vivo assessment, the corneas of rabbits were burned, and PLGA-based epithelial sheets then were transplanted for 2 weeks before histologic staining was conducted and analyzed to determine the effectiveness of the repair. Results: Primary human epithelial cells on the PLGA membrane showed an increased proliferation when cocultured with fibroblasts, which was confirmed by CCK-8 analysis, and upregulation of Ki67, with the expression of the epithelial marker CK19. The stratified squamous cell marker MUC1 and conjunctival cell marker MUC5AC also were expressed in the epithelial sheet. The epithelial defect in the burned corneas was decreased in the PLGA-based epithelial sheet treatment group (6.1% ± 1.6% of the area) compared to that in the no-treatment group (30.5% ± 6.3%) 2 weeks postoperatively. Conclusions: We developed a coculture system using a human feeder cell layer and PLGA membrane-based transwell inserts to create human conjunctival epithelial sheets. This system represents a promising strategy to regenerate corneal epithelium by transplantation.

In Vivo Observation of Endothelial Cell-Assisted Vascularization in Pancreatic Cancer Xenograft Engineering.

In this study, for better understanding of patient-derived xenograft (PDX) generation, angiogenic characteristics during PDX cancerous tissue generation was investigated with different initial cell seeding conditions in the hydrogel. We monitored the angiogenic changes during the formation of in vivo cancer cell line xenografts induced by endothelial cells. Our in vivo cancer tissue formation system was designed with the assistance of tissue engineering technology to mimic patient-derived xenograft formation. Endothelial cells and MIA PaCa-2 pancreatic carcinoma cells were encapsulated in fibrin gel at different mixing configurations and subcutaneously implanted into nude mice. To investigate the effect of the initial cancerous cell distribution in the fibrin gel, MIA PaCa-2 cells were encapsulated as a homogeneous cell distribution or as a cell aggregate, with endothelial cells homogeneously distributed in the fibrin gel. Histological observation of the explanted tissues after different implantation periods revealed three different stages: isolated vascular tubes, leaky blood vessels, and mature cancerous tissue formation. The in vivo engineered cancerous tissues had leaky blood vessels with low expression of the vascular tight junction marker CD31. Under our experimental conditions, complex cancer-like tissue formation was most successful when tumorous cells and endothelial cells were homogeneously mixed in the fibrin gel. The present study implies that tumorous xenograft tissue formation can be achieved with a low number of initial cells and that effective vascularization conditions can be attained with a limited volume of patient-derived cancer tissue. Endothelial cell-assisted vascularization can be a potent choice for the effective development of vascularized cancerous tissues for studying patient-derived xenografts, cancer angiogenesis, cancer metastasis, and anticancer drugs.

Association between Exposure to Traffic-Related Air Pollution and Prevalence of Allergic Diseases in Children, Seoul, Korea.

Although there has been suggestive evidence of the association between TRAP and ADs, findings remained inconsistent possibly due to limited population. We investigated the association between TRAP and ADs in a large population of children with rich spatial coverage and expanded age span in Seoul, Korea. TRAP exposures were estimated by categorized proximity to the nearest major road (≤150, 150-300, 300-500, and >500 m) and density of major roads within 300 meters from children's residences. We estimated the association between two TRAP exposures and three ADs using generalized mixed model after adjusting for individual characteristics. We also investigated whether the association varied by household and regional socioeconomic status. We found associations of atopic eczema with road density [OR = 1.08; 95% CI = 1.01-1.15] and road proximity [1.15, 1.01-1.32; 1.17, 1.03-1.34; and 1.16, 1.01-1.34 for ≤150, 150-300, and 300-500 m, resp., compared to >500 m]. There was no association with asthma and allergic rhinitis. Effect estimates were generally the highest in the low socioeconomic region. Children living in areas surrounded by large and busy roads were likely to be at greater risks for atopic eczema, with increased vulnerability when living in deprived areas.

Multilayered Engineered Tissue Sheets for Vascularized Tissue Regeneration.

A major hurdle in engineering thick and laminated tissues such as skin is how to vascularize the tissue. This study introduces a promising strategy for generating multi-layering engineered tissue sheets consisting of fibroblasts and endothelial cells co-seeded on highly micro-fibrous, biodegradable polycaprolactone membrane. Analysis of the conditions for induction of the vessels in vivo showed that addition of endothelial cell sheets into the laminated structure increases the number of incorporated cells and promotes primitive endothelial vessel growth. In vivo analysis of 11-layered constructs showed that seeding a high number of endothelial cells resulted in better cell survival and vascularization 4 weeks after implantation. Within one week after implantation in vivo, red blood cells were detected in the middle section of three-layered engineered tissue sheets composed of polycaprolactone/collagen membranes. Our engineered tissue sheets have several advantages, such as easy handling for cell seeding, manipulation by stacking each layer, a flexible number of cells for next-step applications and versatile tissue regeneration, and automated thick tissue generation with proper vascularization.

Validity and reliability of the safe driving behavior measure in community-dwelling self-drivers with stroke.

[Purpose] Driving is a vital component of recovery for stroke survivors facilitating restoration of their family roles and reintegration back into their communities and associations. The purpose of this study was to evaluate the validity and reliability of the Safe Driving Behavior Measure (SDBM) in community-dwelling self-drivers post-stroke. [Subjects and Methods] Participants were sixty-seven community-dwelling self-drivers who had received a diagnosis of first stroke in the past twelve months. To investigate the validity and reliability of the SDBM, this study evaluated two sessions, held three days apart in a quiet and well-organized assessment room. Cronbach's alpha and the Intraclass Correlation Coefficient [ICC (2.1)] were used to evaluate statistically concurrent validity and reliability of the overall and three domain scores. Pearson's correlations were used to quantify the bivariate associations among the three domains. [Results] The Cronbach's alpha coefficients for the three domains of person-vehicle (0.989), person-environment (0.997), and person-vehicle-environment (0.968) of the SDBM indicated high internal consistency in community-dwelling self-drivers with stroke, in addition to excellent rest-retest reliability. [Conclusion] The results of this study suggest that the SDBM could be a reliable measure to evaluate automobile driving in community-dwelling self-drivers with stroke.

Three-dimensional motion analysis in the elbow joint position sense in children.

[Purpose] The purpose of this study was to investigate the difference in elbow joint position sense in children. [Subjects and Methods] Nineteen healthy children volunteered as subjects for this study. Joint position sense was assessed by asking the children to flex their elbows between 30° to 110° while blindfolded. The error range of elbow movement was analyzed with Compact Measuring System 10 for three-dimensional motion. To analyze data, descriptive statistics and paired t-test analysis were performed by using IBM SPSS Statistics 20.0. [Results] A significantly lower error was found in 30° right elbow flexion than 110° right elbow flexion (p<0.05). No significant difference was found between 30° and 110° left elbow flexion. [Conclusion] These results indicate that in children, joint position sense errors decrease as joint angles approach 30° flexion.

Inhibition of Rho-Associated Protein Kinase Increases the Angiogenic Potential of Mesenchymal Stem Cell Aggregates via Paracrine Effects.

The aggregation of multiple cells, such as mesenchymal condensation, is an important biological process in skeletal muscle development, osteogenesis, and adipogenesis. Due to limited in vivo study model systems, a simple and effective in vitro three-dimensional (3D) aggregation system is required to study the mechanisms of multicellular aggregation and its applications. We first generated controlled mesenchymal stem cell (MSC) aggregates using a bioprinting technique to monitor their aggregation and sprouting. We induced the angiogenic potential of the MSCs through chemical inhibition of the Rho/Rho-associated protein kinase (ROCK) pathway, which led to hairy sprouting in the aggregates. The angiogenic potential of this 3D construct was then tested by subcutaneously implanting the Matrigel with 3D MSC aggregates in a rat. Treatment of 3D MSCs with the ROCK inhibitor, Y27632, increased their angiogenic activity in vivo. The gene expressions and histological staining indicated that angiogenesis and neovascularization were mainly regulated by the paracrine factors secreted from human 3D MSC constructs. Our results demonstrate the enhancement of the angiogenic potential of the MSC constructs through the secretion of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) by the inhibition of the Rho/ROCK pathway.

The effects of a newsletter on bedding control on house dust mite allergen concentrations in childcare centers in Korea.

OBJECTIVES: Bedding in childcare centers (CCCs) can hold house dust mite (HDM) allergens. This study examined whether HDM allergen levels can be reduced through the distribution of an educational newsletter on bedding control to parents of CCC children in Korea. METHODS: All 38 CCCs were measured for Der 1 (sum of Der f 1 and Der p 1) concentrations on classroom floors and bedding before the intervention. Educational newsletters on children's bedding control were sent to 21 CCCs by mail, and teachers were asked to distribute the newsletters to the parents of the children (intervention group). The remaining 17 CCCs were not sent newsletters (control group). The measurement of Der 1 concentrations in 38 CCCs was repeated after the intervention. Dust samples were collected with a vacuum cleaner and analyzed using enzyme-linked immunosorbent assay methods. RESULTS: The Der 1 concentrations on the bedding were significantly higher than those on the floors in 38 CCCs at baseline (p<0.05). Although changes of the Der 1 concentrations for the control group (n=17) were not significant, Der 1 concentrations for the intervention group (n=21) decreased significantly from 2077.9 ng/g dust to 963.5 ng/g dust on the floors and from 3683.9 ng/g dust to 610.4 ng/g dust on bedding (p<0.05). CONCLUSIONS: The distribution of educational newsletters on bedding control to parents may be an effective means of controlling HDMs in CCCs.

Low consumption of fruits and dairy foods is associated with metabolic syndrome in Korean adults from outpatient clinics in and near Seoul.

BACKGROUND/OBJECTIVES: The aim of this study was to examine differences in nutrient intake and food consumption by the presence of metabolic syndrome in Korean adults. SUBJECTS/METHODS: Study subjects in this cross-sectional study were recruited from four outpatient clinics in and near the Seoul metropolitan area of South Korea between 2006 and 2012. A total of 668 subjects (413 men and 255 women) aged ≥ 30 y were included in the final data analyses. For each subject, daily nutrient intake and food consumption were calculated using three days of dietary intake data obtained from a combination of 24-hour recalls and dietary records. To evaluate food consumption, mean number of servings consumed per day and percentages of recommended number of servings for six food groups were calculated. Metabolic syndrome was defined using the National Cholesterol Education Program Adult Treatment Panel III criteria. The general linear model was performed to examine differences in nutrient intake and food consumption by sex and the presence of metabolic syndrome after adjustment for potential confounding variables. RESULTS: Nutrient intake did not differ by the presence of metabolic syndrome in both men and women. Men with metabolic syndrome had lower consumption and percentage of the recommendation for fruits compared with those without metabolic syndrome (1.6 vs. 1.1 servings/day, P-value = 0.001; 63.5 vs. 49.5%, P-value = 0.013). Women with metabolic syndrome showed lower consumption and percentage of the recommendation for dairy foods than those without metabolic syndrome (0.8 vs. 0.5 servings/day, P-value = 0.001; 78.6 vs. 48.9%, P-value = 0.001). CONCLUSIONS: Low intakes of fruits and dairy foods might be associated with the risk of having metabolic syndrome among Korean adults. Dietary advice on increasing consumption of these foods is needed to prevent and attenuate the risk of metabolic syndrome.

Air Quality, Biomarker Levels, and Health Effects on Staff in Korean Restaurants and Pubs Before and After a Smoking Ban.

INTRODUCTION: The Korean government implemented a smoking ban at square floor area of ≥150 m(2), rather than <150 m(2), restaurants and pubs from July 2013. This study examined the effects of the smoking regulations in restaurants and pubs in terms of the air quality, biomarker levels and health effects on staff. METHODS: Particulate matter smaller than 2.5 µm (PM2.5) was measured in 146 facilities before and 1 month after the ban. The urinary cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanol (NNAL) levels were measured in 101 staff members at 77 facilities before and 1 month after the ban. We also measured self-reported respiratory and sensory symptoms on both phases. RESULTS: Of the 146 facilities, 121 facilities were included in the PM2.5 analysis. In ≥150 m(2) pubs, the indoor PM2.5 concentration was significantly reduced after the ban (p < .05). While the urinary cotinine concentrations of the staff in all facilities were not changed after the ban, the total NNAL concentrations of the staff in ≥150 m(2) pubs were significantly reduced after the ban (p < .05). The health effects on staff show that only sensory symptoms significantly improved in ≥150 m(2) facilities after the ban (p < .05). CONCLUSIONS: The smoking ban significantly reduced the levels of PM2.5 and total NNAL concentrations in ≥150 m(2) pubs and improved sensory health among staff in ≥150 m(2) facilities. The results of this study can be useful in supporting an expansion of the smoking ban in all indoor places, including <150 m(2) restaurants and pubs.

Association between exposure to antimicrobial household products and allergic symptoms.

OBJECTIVES: Antimicrobial chemicals are used in a variety of household and personal care products. Exposure to antimicrobial household products has been hypothesized to lead to allergic diseases in children. METHODS: We investigated antimicrobial household product exposure and allergic symptoms in Korean children. An antimicrobial exposure (AE) score was derived. To examine the symptoms of allergic diseases (current wheeze, current rhinitis, and current eczema) in the past 12 months, we used a questionnaire based on the core module of the International Study of Asthma and Allergies in Children. Complete data for the analysis were available for 25,805 of the 35,590 (72.5%) children. RESULTS: The prevalence of current allergic diseases was as follows: wheeze, 5.6%; allergic rhinitis, 32.6%; and eczema, 17.7%. The mean (standard deviation) AE score was 14.3 (9.3) (range: 0-40). Compared with subjects with a low AE score (reference), subjects with a high AE score (fourth quartile) were more likely to have symptoms of wheezing and allergic rhinitis (adjusted odds ratio [aOR] for wheezing 1.24, 95% confidence interval [CI], 1.05-1.45, p for trend=0.24; aOR for allergic rhinitis 1.30, 95% CI, 1.20-1.40, p<0.01). CONCLUSIONS: These findings suggest that frequent use of antimicrobial household products was associated with current wheeze and current allergic rhinitis.

Differential regeneration of myocardial infarction depending on the progression of disease and the composition of biomimetic hydrogel.

Hydrogel has been used for regenerating myocardial infraction (MI) as a delivery vehicle for cells and growth factors. This study showed that injectable hyaluronic acid (HA)-based hydrogels alone would effectively regenerate the damaged infarcted heart tissue. We found that there are two major factors of regeneration in MI. One is molecular weight of HA and another is the progression of MI; sub-acute and chronic. Rat MI model was prepared by ligating the left anterior descending coronary artery (LAD). Four weeks after injection of hydrogel, functional analysis of the heart and histological analysis was assessed. When different molecular weight HA-based hydrogels with 50 kDa, 130 kDa, and 170 kDa were applied to the infarcted area in the sub-acute model, 50 kDa HA-based hydrogel showed the most significant regeneration of myocardium as well as functional recovery among samples. For the disease progression, 50 kDa HA-based hydrogels were injected to sub-acute and chronic MI models. The regeneration activity was significantly decreased in the chronic models reflecting that injection timing of the therapeutic agents is also major determinants in the regeneration process. These results suggest that injection time and composition of hydrogel are two major points treating MI.

Effect of prolonged breast-feeding on risk of atopic dermatitis in early childhood.

The effect of breast-feeding on the risk of developing atopic disease remains controversial. This study is an investigation of the effect of breast-feeding on current atopic dermatitis (AD) among Korean children. This cross-sectional study of children's histories of current AD and environmental factors was completed by the subjects' parents. The subjects included 10,383 children aged 0-13 years in Seoul, Korea, in 2008. The diagnostic criteria of the International Study of Asthma and Allergies in Childhood were applied in this study. Adjustments were performed for age, gender, maternal education, smoking in the household, relocation to a new house within 1 year of birth, and parental history of atopic disease. After adjustment for confounders, age and duration of maternal education were found to be inversely associated with the prevalence of AD. Among subjects aged ≤5 years, the prevalence of AD was positively associated with the duration of breast-feeding (p < 0.001). However, there was no significant association between AD and breast-feeding among children >5 years of age. Regardless of parental history of atopic diseases, breast-feeding >12 months was a significant risk factor for AD. The effect of breast-feeding differed by age group. Prolonged breast-feeding increased the risk of AD in children <5 years of age, regardless of parental history of atopic diseases.