Jie Qi, Ph.D. (right), our senior research scientist, and Liqun Chi (left), a former lab technician, perform basic science research using our products in the field of Tissue Engineering.
We are currently running four major projects:
1. The functions of extracellular nucleotides in mechanical signal transduction. We found that extracellular nucleotides (ATP, UTP) play an important role in mechanical signal transduction. Stretch will stimulate the secretion of ATP and will upregulate the expression of the apical membrane ABC transporter cystic fibrosis transmembrane conductance regulator (CFTR). Addition of apyrase to the medium will block the response of cells to mechanical load. There is also feedback regulation between extracellular ATP and the mechanical load response. Pretreating cells with ATP blocks the cellular responses to mechanical loading. High concentrations of extracellular ATP will reduce the contraction of mouse osteoblast MC3T3-E1 populated 3D collagen gels by blocking the NF-kB pathway. Quantitative RT-PCR studies show that extracellular ATP downregulated the expression of integrin 1, matrix proteins (collagens I and V, fibronectin, and decorin) and cytoskeleton proteins (vinculin, palladin, and actopaxin), but upregulated the expression of integrin 5 and osteopontin, a major extracellular matrix protein of bone cells.
2. Influence of mechanical loading and cytokines on the strength of bioartificial tendons (BATs). Bioartificial tendons are human tenocyte populated 3D collagen gels fabricated in Tissue Train® culture plates. We treat BATs with 100 pM IL-1 for one week and test the strength of BATs using EnduraTEC® ELF 3200 series equipment. We found that IL-1 treatment decreased the strength of BATs, but increased the elasticity. Quantitative RT-PCR and immunostaining results showed that IL-1 decreased the expression of type I collagen and actin, but increased elastin expression.
3. Preliminary study on the application of BATs in tendon repair using chicken as an in vivo model. The regulation of intrinsic strain is important for the repair and recovery of injured tendon tissues. Using the Tissue Train® 3D culture system, we can investigate the influence of mechanical loads, nucleotides and cytokines on the strength of BATs so that we can control the intrinsic strain of BATs before we implant them into wounded tendon tissues to improve functional recovery.
4. The polarity of neurons, the formation of axon and dendrites is the prerequisite for signal transduction in the neuronal system. The mechanisms of establishment and maintenance of neuronal polarity are not completely understood. However, it has been shown that reorganization of cytoskeleton, intercellular calcium, protein kinases, MAPK and small GTPases are involved in this process. It is well known that exercise is important for the recovery of neuronal system injury, especially for motor neurons. It has been reported that cyclic mechanical loading activated protein kinases and small GTPases, induced reorganization of the cytoskeleton, and increased intercellular calcium. Therefore, we hypothesized that cyclic mechanical loading may stimulate the polarization of neurons. In this project, we investigate the effects of cyclic mechanical loading on the polarization of neuron cells (B35, PC12 and some primary neuron cells such as hippocampal neurons) grown on silicone membranes or in three dimensional collagen gels (BATs).
