Objective To evaluate which is better method zymogen or low temperature frozen in removing vascular endothelial cell so as to lay a foundation for creating a kind of brace which is not to be rejected and the same as own blood vessel. Methods Fresh and not damaged umbilical blood vessel was collected from natural labour women, human umbilical blood vessel was remove carefully from normal foetus, then was put into disinfectant at 37℃ for 24 hours. They were divided into 3 groups:normal group(NG),zymogen group(ZG) and low temperature frozen group(LG). ZG: 0.1% collagenⅡ enzyme was addedin umbilical blood vessel and closed the both sides and the vascular endothelialcell was removed in 37℃ water. LG:Umbilical blood vessel was put into liquidnitrogen for 24 hours after frozened step by step, and then it was put into 37℃ water for 30-60 s and the vascular endothelial cells were washed away by normal saline. NG:Umbilical blood vessel was kept into 4℃ Kerb’s liquid. The bacteria were culturedin each group. The samples were stained by HE,elastic fiber and collagen fiberwere observed by light and scanning electron microscope. The difference of compliance was compared. Human leukocyte antigen ABC(HLA-ABC) and HLA-DR were observed by immunohistochemical method and the expression of antigen of umbilical blood vessel was analysed. Results In LG, umbilical vascular endothelial cells were removed completely; artery showed vertical smooth muscle and vein showed elastic membrane. InZG, umbilical vascular endothelial cells were removed completely after 20 minutes;artery showed vertical smooth muscle cells and vein showed lower endothelial layer. The vascular compliance in LG was higher than that in NG, and the latter was also higher than that in ZG,but showing no significant differences (Pgt;0.05). The compliance of umbilical vein was 2-3 times as much asthat of umbilical artery.The expression of HLA-ABC and HLA-DR in LG andZG were lower than that in NG, showing significant differences (Plt;0.01). Conclusion Low temperature frozen methodand zymogen method(0.1% collagen Ⅱ enzyme for 20 min) can remove vascular endothelial cells of human umbilical blood vessel completely.Low temperature frozenmethod was better than zymogen method.
ObjectiveTo study the preparation and cytocompatibility of bone tissue engineering scaffolds by combining low temperature three dimensional (3D) printing and vacuum freeze-drying techniques. MethodsCollagen (COL)and silk fibroin (SF) were manufactured from fresh bovine tendon and silkworm silk. SolidWorks2014 was adopted to design bone tissue engineering scaffold models with the size of 9 mm×9 mm×3 mm and pore diameter of 500μm. According to the behavior of composite materials that low temperature 3D printing equipment required, COL, SF, and nano-hydroxyapatite (nHA)at a ratio of 9:3:2 and low temperature 3D printing in combination with vacuum freeze-drying techniques were accepted to build COL/SF/nHA composite scaffolds. Gross observation and scanning electron microscope (SEM) were applied to observe the morphology and surface structures of composite scaffolds. Meanwhile, compression displacement, compression stress, and elasticity modulus were measured by mechanics machine to analyze mechanical properties of composite scaffolds. The growth and proliferation of MC3T3-E1 cells were evaluated using SEM, inverted microscope, and MTT assay after cultured for 1, 7, 14, and 21 days on the composite scaffolds. The RT-PCR and Western blot techniques were adopted to detect the gene and protein expressions of COL I, alkaline phosphatase (ALP), and osteocalcin (OCN) in MC3T3-E1 cells after 21 days. ResultsCOL/SF/nHA composite scaffolds were successfully prepared by low temperature 3D printing technology and vacuum freeze-drying techniques; the SEM results showed that the bionic bone scaffolds were 3D polyporous structures with macropores and micropores. The mechanical performance showed that the elasticity modulus was (344.783 07±40.728 55) kPa; compression displacement was (0.958 41±0.000 84) mm; and compression stress was (0.062 15±0.007 15) MPa. The results of inverted microscope, SEM, and MTT method showed that a large number of cells adhered to the surface with full extension and good cells growth inside the macropores, which demonstrated a satisfactory proliferation rate of the MC3T3-E1 cells on the composite scaffolds. The RT-PCR and Western blot electrophoresis revealed gene expressions and protein synthesis of COL I, ALP, and OCN in MC3T3-E1 cells. ConclusionLow temperature 3D printing in combination with vacuum freeze-drying techniques could realize multi-aperture coexisted bionic bone tissue engineering scaffolds and control the microstructures of composite scaffolds precisely that possess good cytocompatibility. It was expected to be a bone defect repair material, which lays a foundation for further research of bone defect.
ObjectiveTo quantify the global burden of chronic obstructive pulmonary disease (COPD) attributable to high temperature, low temperature, and non-optimal temperatures from 1990 to 2021 using Global Burden of Disease (GBD) 2021 data. MethodsWe analyzed global, regional, and national COPD mortality and disability-adjusted life years (DALYs) attributable to high, low, and non-optimal temperatures. Joinpoint regression, age-period-cohort modeling, and Bayesian prediction models were employed. ResultsGlobally, age-standardized mortality rates (ASMRs) and DALY rates for COPD attributable to low temperature and non-optimal temperatures declined. However, the burden from high temperature increased. Low temperature consistently exerted a greater burden than high temperature across all metrics. Significant geographical disparities emerged: high-temperature mortality was highest in South Asia; low-temperature burden was most severe in East Asia; and high-income North America exhibited accelerated high-temperature mortality growth. The highest low-temperature burden occurred in middle-SDI regions, while high-temperature impacts predominated in low-middle-SDI regions. Age patterns showed rising high-temperature burden in the 15-39 age group and increasing low-temperature burden among adults aged ≥80 years. Bayesian projections revealed divergent gender trajectories: a continuing decline in low-temperature burden for males versus a decelerated decline for females (2020-2030). ConclusionLow temperature exposure remains the primary risk factor for COPD within non-optimal temperatures globally, although high-temperature impacts are increasing. Significant regional variations necessitate targeted interventions for three key populations: older adults vulnerable to cold, working-age adults with occupational heat exposure, and older women requiring rehabilitative support.