Biomedical subjects

Ung-il Chung

Publications and source records attributed to Ung-il Chung.

21 records · Page 2Linked to original sources

PubMed2004

The combination of SOX5, SOX6, and SOX9 (the SOX trio) provides signals sufficient for induction of permanent cartilage.

OBJECTIVE: To regenerate permanent cartilage, it is crucial to know not only the necessary conditions for chondrogenesis, but also the sufficient conditions. The objective of this study was to determine the signal sufficient for chondrogenesis. METHODS: Embryonic stem cells that had been engineered to fluoresce upon chondrocyte differentiation were treated with combinations of factors necessary for chondrogenesis, and chondrocyte differentiation was detected as fluorescence. We screened for the combination that could induce fluorescence within 3 days. Then, primary mesenchymal stem cells, nonchondrogenic immortalized cell lines, and primary dermal fibroblasts were treated with the combination, and the induction of chondrocyte differentiation was assessed by detecting the expression of the cartilage marker genes and the accumulation of proteoglycan-rich matrix. The effects of monolayer, spheroid, and 3-dimensional culture systems on induction by combinations of transcription factors were compared. The effects of the combination on hypertrophic and osteoblastic differentiation were evaluated by detecting the expression of the characteristic marker genes. RESULTS: No single factor induced fluorescence. Among various combinations examined, only the SOX5, SOX6, and SOX9 combination (the SOX trio) induced fluorescence within 3 days. The SOX trio successfully induced chondrocyte differentiation in all cell types tested, including nonchondrogenic types, and the induction occurred regardless of the culture system used. Contrary to the conventional chondrogenic techniques, the SOX trio suppressed hypertrophic and osteogenic differentiation at the same time. CONCLUSION: These data strongly suggest that the SOX trio provides signals sufficient for the induction of permanent cartilage.

Adult↗

PubMed2004

Distinct osteogenic mechanisms of bones of distinct origins.

Mammalian bones have three distinct origins (paraxial mesoderm, lateral plate mesoderm, and neural crest) and undergo two different modes of formation (intra-membranous and endochondral). Bones derived from the paraxial mesoderm and lateral plate mesoderm mainly form through the endochondral process. During this process, hypertrophic chondrocytes play a vital role in inducing both osteogenesis and angiogenesis. One of the essential osteogenic factors secreted from hypertrophic chondrocytes is Indian hedgehog (Ihh). In contrast, bones derived from the neural crest mainly form through the intramembranous pro-cess and do not require Ihh. Thus, depending on their origin, bones have distinct signaling properties, which need to be considered in the research and application of bone biology.

Animals↗

PubMed2004

[Regenerative medicine of bone and cartilage].

Regenerative medicine, which takes advantage of the unique capacity of stem cells, is a novel medical strategy to cure irreversible organ failure. There are three important elements in regenerative medicine: cells, scaffolds and signals. Although substantial progress regarding each element has been made in the past few years, it still falls short of clinical applications. In the geriatric field, osteoporosis, osteoarthritis and periodontitis are the major targets of regenerative medicine. They are usually not life-threatening, but often severely affect QOL of elderly patients. Since elderly people have already reduced number of stem cells in bone and cartilage, we need to know the sufficient conditions for osteogenesis and chondrogenesis by comprehensively screening various conditions. We developed a marker gene system expressing green fluorescence protein (GFP) under the control of osteoblast- and chondrocyte-specific promoters. This system helps us monitor osteoblast and chondrocyte differentiation easily, precisely and non-invasively. Using this system, we are now trying to find the sufficient conditions for osteogenesis and chondrogenesis, and to discover osteogenic and chondrogenic small compounds.

Aged↗