| Summary: | 博士 === 國立臺灣大學 === 醫學工程學研究所 === 97 === Tooth is a special organ, the hardest tissue in body is tooth, which is used to tear, scrape, milk, and chew food. Tooth losses may affect most adults adversely at some time in their lives due to dental caries, periodontal disease, trauma and/or a variety of genetic disorders. So far, the therapeutic options to treat missing teeth are by using crown-bridge restoration, removable dental, and dental implant. Dental implant can provide an adequate solution for tooth regeneration, however; the cost of dental implant is expensive and the surgical is needed. Therefore, consideration of the quality of live and the limitations of current treatment options have driven the research into tooth regeneration as a new option. In addition, tooth is an organ, to understand the tooth regeneration is leading to understate the organ regeneration. So Far, the hypothesis of this study is as following biomaterials play important roles in tissue or organ regeneration and proper biomaterials may affect the growth and differentiation of cells through signal transduction pathways. Therefore, the purpose of this study is to investigate the effects of biomaterials on tooth germ (TG) cells growth and differentiation in tooth regeneration.
Tooth germ cells, the formation of teeth, constantly using in tooth regeneration, involving ameloblasts, odontoblasts, mesenchyme cells, and stem cells. This study precede the tooth regeneration for investigating relationship of TG cells with biomaterials and including four parts: the first part is to investigate the growth and potential of TG cells isolated from different age of Wistar rats. The second part is to find the best biomaterials for the growth of TG cells and observed the interaction of TG cells. The third part is to investigate the substrate similar to the biological environment for improving proliferation, mineralization, and differentiation of TG cells on biomaterials. The forth part is to investigate the act of biomaterials on mineralization and differentiation of TG cells through cell signaling pathway.
The structures and characters of tooth are different in different age during the development of tooth. Therefore, it is important to find the best age source of TG cells for the study on tooth regeneration. In part I, the purpose of this study is to find the adequate TG cells from different age rats for tooth regeneration. Interestingly, the best proliferation and differentiation potential of TG cells might be from cells isolated from four-day-old rats. Hence, TG cells from four-day-old rats are used in this study.
Although, biomaterials are generally used in tissue engineering, however; the effects of biomaterials on TG cells are still unknown. In part II, the aim is to observe the interaction of TG cells and biomaterials of varying surface hydrophilicities. The biomaterials including pol (yvinyl alcohol; PVA), poly (lactic-co-glycolic acid; PLGA), poly (ethylene-co-vinyl alcohol; EVAL), and poly (vinylidene fluoride; PVDF) are used. Our results indicate that adhesion of tooth germ cells to biomaterials with moderate hydrophilicity/hydrophobicity was superior compared to extreme analogs. Cellular adhesion and proliferation was evident on all tested biomaterials except PVA. Surprisingly, the spheroidal cellular aggregation on PVA appeared not to be proliferative, cells remained vitally and is able to reattach to tissue culture plates as determined. It is suggested that the behaviors of TG cells can be medicated by biomaterials.
Many papers have been reported that low cellular proliferation is conducive to cellular differentiation. Low cellular proliferation may indicate the cell-cell interactions are compacted. In part III, TG cells cultured on PVA with different cell densities to obtain the compacted cell-cell interactions are described. TG cell spheroids on PVA obviously increased the alkaline phosphatase (ALP) activity, the degree of mineralization, and upregulate osteopontin, osteonectin, dentin matrix protein 1, and enamelin genes, regardless of the low or high seeding density. Surprisingly, it seemed that PVA appears to activate the ALP activity and mineralization effects on TG cell spheroids in the absence of differentiation medium. Furthermore, the present study indicates that ECM may play an important role in mineralization on TG cell spheroids by adding Arg-Gly-Asp (RGD) peptides.
In addition, many papers have been reported that mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in tightly related to the regulation of cell proliferation, differentiation, motility and death of osteoblast, especially through extracellular signal-regulated kinase1/2 (ERK1/2), however; there were contradictory results about the relationship between ERK1/2 phosphorylation and osteoblast differentiation. In part IV, in order to determine the role of ERK 1/2 pathway in enhancing ALP activity and mineralization of TG cells, the specific inhibitor for blocking the pathway are used. The results reveal that PVA itself can stimulate TG cells with the differentiation and mineralization ability. By showing the direct suppression of extracellular signaling-regulated kinase (ERK1/2) of TG cells treated with inhibitor, known to suppress the activation of ERK1/2, and significant synergistic effects between PVA and inhibitor, we demonstrated the suppression of ERK1/2 pathway is one of the effects of PVA-promoted TG cell differentiation and mineralization. Importantly, analysis of the data of the proliferation, mineralization, and differentiation of TG cells on biomaterials demonstrated the feasibility of utilizing biomaterials in clinical applications for tooth regenerating.
|
|---|
