Tissue engineering is one of the most promising subjects,which has broad application prospects in the fields of regenerative medicine and human health care.According to the papers published in this current issue about scaffold material preparation and mechanical environment affection to cells during the construction process of tissue engineering,this paper describes the current status and progress of tissue engineering research at home and abroad,indicating that tissue engineering research is developing to a deeper and wider field.

Objective To study the main mechanotransduction area and to estimate the overall shear deformation of rat osteoblasts in shear stress loading experiment based on data acquired from the in vitro rat osteoblast experimental, and to study the effects of four-point bending medium flow generated shear stress on cells. Methods Viscoelastic mechanics theory was used in the calculation process, the standard viscoelastic model was adopted for cells, and shear force on the cellular surface was simplified to be uniform. Results The cellular deformation caused by shear force was about one-tenth of that from tensile loading experiment which induced equivalent biological response. Conclusion In terms of mechanical stimulus induced biological responds, the mechanical transduction caused by cellular deformation in shear stress loading experiment is negligible, and the main transduction area is in the cellular membranes experiencing shear stress.

Osteoclast is one of the basic function cells involved in bone metabolism during the process of bone remodeling.Osteoclasts are responsible for destruction and absorption of the old bone tissue.Thus,a tiny change of osteoclast apoptosis may change the process of bone remodeling.Osteoclast apoptosis is regulated by many factors including estrogen,bisphosphonates and so on.However,fewer researches on effect of mechanical loading on the biological activity of osteoclasts has been carried out.In this paper,the effect of mechanical loading on the biological activity of osteoclasts and its regulation on apoptosis of cells and osteoclast are reviewed.

Seed cell, biomaterials, constructing of tissue are three essential elements of tissue engineering. The core is the technology of tissue constructing. Bioreactor for tissue engineering is a sort of systematic equipment constructing ttissues in vitro. Cardiac tissue engineering may hold great potentials for not only replacing or supporting an infarcted cardiac tissue but also treating and saving the lives of patients with heart diseases. This paper mainly introduced the progress of domestic and international technology for constructing engineered cardiac tissue in vitro, especially in the research of bioreactors used for engineered cardiac tissue construction.

Objective To prepare the small intestinal submucosa (SIS) to be used as a scaffold in constructing engineered cardiac tissue. Methods Small intestinal submucosa of pig was treated with 0.25% trypsin and then 0.5% SDS for 24 hours each to obtain decellularized SIS. The obtained SIS was tested for its mechanical strength by stretching both horizontally and longitudinally with a material test machine. The cytotoxicity and histocompatibility of the material was also examined. Then the cardiomyocytes harvested from 3-day old neonatal rats were seeded on the SIS to construct engineered cardiac tissue sheets. These acquired engineered cardiac tissue sheets were immunohistochemically stained and observed with inversion microscope and transmission electromicroscope to evaluate their characteristics. Results SIS was decellularized completely. The mechanical capability of the decellularized SIS was satisfactory. Under 15% stretching, its strain and stress was nearly linear. SIS showed no cytotoxicity and inflammatory response. After 12 hours, the cardiomyocytes seeded in the SIS scaffold began to beat spontaneously. Two days later, the cardiomyocytes-SIS scaffold composite (engineered cardiac tissue sheet) began to beat spontaneously, and could beat spontaneously for 14 days. The constructed engineered cardiac tissue sheets consisted of layers of cardiomyocytes and with abundant extracellular collagen in the sheet. Conclusions SIS with good mechanical capability and biocompatibility has been prepared successfully, and then the engineered cardiac tissue has been constructed successfully based on the SIS scaffold.

Bone marrow mesenchymal stem cells (BMSCs) is a kind of multipotent adult stem cells,which is one of the most important seed sources of tissue engineering.Microgravity has inhibitory effects on osteogenic differentiation of BMSCs,which will cause bone mass reduction and changes of bone micro-structure that finally lead to osteoporosis.This process is regulated by multiple signaling pathways such as mitogen-activated protein kinase (MAPK) pathway,Notch pathway and Wnt/β-catenin pathway which co-regulated BMSCs osteogenic differentiation under microgravity.Studying the effects of microgravity on BMSCs into osteogenic differentiation can clarify the mechanism of bone loss,put forward new targets for the treatment of diseases and provide a useful reference for the development of China's space industry.

BACKGROUND:With the development of science and technology and modern aerospace, the effects of mechanobiology in extreme mechanical environment—high acceleration are becoming an issue of concern. Studies have shown that high acceleration has certain effects on the cels. OBJECTIVE:Based on a centrifuge, to design a cel loading centrifuge used for exploration of cel mechanobiology under high acceleration. METHODS:For the cel loading centrifuge, a culture plate or/and culture bottle ful of culture fluid was/were loaded with constant acceleration or variable velocity to explore the experimental feasibility. Besides, a finite element model was built by ANSYS software according to structure and properties of the rotor. The rotor system was calculated under equilibrium and dangerous working conditions, respectively, to analyze the stress and deformation distribution. Moreover, the strength of the main shaft was checked under the dangerous working conditions. Then the analysis results of ANSYS were compared with the results of strength check. RESULTS AND CONCLUSION:Experimental findings showed that the culture plate or/and the culture bottle could be used for (0-40)×g highly constant acceleration or variable acceleration loading. Through the simulation and comparison analysis, we confirmed the reliability of the cel loading centrifuge. This cel loading centrifuge can be used to implement the study of cel mechanobiology under high acceleration in the general biology laboratory. It also provides a basis for wide application of cel loading centrifuge in the future.

Objective To observe the adhesion of MC3T3-EI osteoblastic progenitor cells to the three-dimensional chitosan-decellularised-derma scaffolds,and evaluate the cytocompatibility of the scaffolds.Method The threedimensional chitosan-decellularised-derma scaffolds were prepared by the freeze-dtying method,the porosity,density and water absorption of which were measured.The microscopic morphology of the composite scaffolds was analyzed by the scanning electron microscopy(SEM).The MC3T3-E1 cells cultivated in vitro were seeded onto the composite scaffolds,and then co-cultured for 2,3,4 and 5 hours.At each time point,three specimens from each matrix were taken to determine the cell-adhesion rate and the best time of the cell-adhesion.The cells were seeded onto the composite scaffolds,and then co-cultured for 1,3,5,7,9,11 and 13 days.The MC3T3-E1 cells inside were evaluated with MTS test.The cell morphology was observed by the histological staining.The compression tests were performed using a Universal Testing Machine,at room temperature,as compared with no-cell-scaffolds.Results The three-dimensional chitosan-decellularised-derma scaffolds have high interval poroslty with the porosity(92.8%),the density(0.09796 g/ml)and the water absorption(2169±100)%.The cytocompatibility test shows that the seeded MC3T3-E1 cells can adhere to the scaffolds and proliferate.Conclusions The three-dimensional chitosan-decellularised-derma scaffolds have high interval porosity with the welldistributed diameter.The MC3T3-E1 cells are easy to adhere the scaffolds and proliferate which shows that the scaffolds have a good cytocompatibility.

Nano-hydroxyapatite has been widely used as reconstructive and prosthetic material for osseous tissue,owing to its excellent biocompatibility and tissue bioactivity.But the poor mechanical property of hydroxyapatite restricts its further application.In order to enhance the comprehensive performance of the material,many researches have been dedicated to the synthesization of the composite materials.This article reviews the main preparation methods of nano-hydroxyapatite and the advancement in research of its composite.The directions in this research area are described as well.

This paper designs a kind of electric field generator based on high-frequency waveform generator MAX038 according to the need of the myocardial tissue engineering research.The amplitude,pulse width and frequency of the signal producing by the generator can be adjusted.Characterized with high precise and wide frequency scope,this generator can produce triangle,square and sine waveforms and pulse etc.