Eiki Koyama, DDS, PhD
Most Recent Peer-reviewed Publications
- Osteophyte formation and matrix mineralization in a TMJ osteoarthritis mouse model are associated with ectopic hedgehog signaling
- Genesis and morphogenesis of limb synovial joints and articular cartilage
- TMJ degeneration in SAMP8 mice is accompanied by deranged ihh signaling
- Mouse limb skeletal growth and synovial joint development are coordinately enhanced by Kartogenin
- Lubricin is required for the structural integrity and post-natal maintenance of TMJ
DDS, Matsumoto Dental University - 1985
PhD, Okayama University, Developmental Biology - 1992
Expertise & Research Interests
Dr. Koyama's research involves molecular and cellular analyses of synovial joint formation in mouse and chick embryos, which are invaluable for the insights they provide into how specific populations of cells are able to cleave at specific boundary lines and reorganize into highly ordered and reiterative patterns. In the developing embryos, the first overt sign of joint development is the appearance of a layer of closely-packed mesenchymal non-chondrogenic cells at each prospective joint site and this trangient structures are collectively referred to as the interzone. With further development, cavitation process takes place, leads to physical separation of the adjacent skeletalanlagen, and eventually, all of the joint components are formed including joint capsule, synovial cavity, and articular cartilage. Given the tempro-sapatial appearance and distribution, the cells have been thought to be very important for joint formation.
To endeavor the origin, roles and fate of progenitor interzone cells, we produced prenatal and postnatal genetic cell fate-maps by mating ROSA-LacZ-reporter mice with mice expressing Cre-recombinase at prospective joint sites under the control of Gdf5 regulatory sequences (Gdf5-Cre). We found that reporter-expressing cells initially constituted the interzone and later, those cells gave rise to articular cartilage, synovial lining and other joint tissues, but contributed little if any to underlying growth plate cartilage and shaft. In sum, our data indicate that interzone cells present at prospective joint sites and expressing Gdf5 constitute a distinct cohort of progenitor cells responsible for limb joint formation. The cells appear to be patterned along specific limb symmetry axes and rely on local signaling tools to make distinct contributions to joint formation.