Self-Assembly of Aligned Tissue-Engineered Annulus Fibrosus and Intervertebral Disc Composite Via Collagen Gel Contraction

Many cartilaginous tissues such as intervertebral disc (IVD) display a heterogeneous collagen microstructure that results in mechanical anisotropy. These structures are responsible for mechanical function of the tissue and regulate cellular interactions and metabolic responses of cells embedded within these tissues. Using collagen gels seeded with ovine annulus fibrosus cells, constructs of varying structure and heterogeneity were created to mimic the circumferential alignment of the IVD. Alignment was induced within gels by contracting annular gels around an inner boundary using both a polyethylene center and alginate center to create a composite engineered IVD. Collagen alignment and heterogeneity were measured using second harmonic generation microscopy. Decreasing initial collagen density from 2.5 mg/mL to 1 mg/mL produced greater contraction of constructs, resulting in gels that were 55% and 6.2% of the original area after culture, respectively. As a result, more alignment occurred in annular-shaped 1 mg/mL gels compared with 2.5 mg/mL gels (p < 0.05). This alignment was also produced in a composite-engineered IVD with alginate nucleus pulposus. The resulting collagen alignment could promote further aligned collagen development necessary for the creation of a mechanically functional tissue-engineered IVD

Cytogenetic and molecular responses of ammonium sulphate application for tolerance to extreme temperatures in Vicia faba L.

Effects of ammonium sulphate [(NH4)(2)SO4] on mitosis, cell cycle and chromosomes in Vicia faba L. seeds exposed to extreme temperatures were investigated using flowcytometric and cytogenetic analysis. Seeds germinated at high and low temperatures showed a significant decrease in mitotic index as compared to those of optimum temperature conditions. Application of 50 and 1000 mu M (NH4)(2)SO4 were successful in alleviating the negative effects of low and high temperature on mitotic activity, respectively. 50 mu M (NH4)(2)SO4 showed the most positive effect on cell cycle at the extreme temperatures. This concentration increased the cell division removing or decreasing the negative effects of temperature stress. Namely, the highest G2/M and S phase percentages under stress conditions were obtained with application of 50 mu M (NH4)(2)SO4. Chromosomal aberrations were not observed in cells of seeds germinated in distilled water and also at any temperatures. However, the frequency of chromosomal aberrations increased significantly by increasing (NH4)(2)SO4 concentration. The highest aberration frequency in all temperature degree tested was found at 1000 mu M (NH4)(2)SO4 concentration.Department of Scientific Research Project Management of Suleyman Demirel University (SDUBAP)Suleyman Demirel University [1636-YL-08]The authors thank the Department of Scientific Research Project Management of Suleyman Demirel University (SDUBAP) for the financial support of the project SDUBAP (1636-YL-08). Thanks also to Dr. Gulderen Yanikkaya DEMIREL and Mehtap OZDEMIR (Istanbul Centro Laboratory Flowcytometry Department, Istanbul, Turkey) for its help in flow cytometric study