Tamayuki Shinomura

Aggrecan is the most abundant proteoglycan in cartilage. It contains a lot of negatively charged glycosaminoglycan chains along the core protein, providing a large osmotic swelling pressure within the cartilage. Therefore, the biomechanical properties of cartilage, such as its compressive load-bearing capacity, are highly dependent on the presence of abundant aggrecan in the cartilage matrix. To elucidate the transcriptional mechanism that leads to abundant expression of aggrecan by chondrocytes, we screened for enhancer elements in 130 kb of the aggrecan gene, Agc1, using a reporter assay system that we previously developed. The system is based on co-transfection of candidate enhancer elements and reporter constructs into Swarm rat chondrosarcoma chondrocytes that retain a high level of aggrecan expression. We found an element that might be involved in high-level expression of Agc1 gene in chondrocytes in vivo. The element is located 30 kb upstream of the Agc1 transcription start site.

Type II collagen is a major component of cartilage where it is present at a high concentration, which is essential for the functional maintenance of the tissue. Therefore, any fundamental understanding of the physiology of cartilage tissue must include an understanding of the mechanism that allows the high level of expression of type II collagen gene, Col2a1, by chondrocytes. To this end, we developed a new reporter assay system based on the co-transfection of candidate enhancer elements and reporter construct into Swarm rat chondrosarcoma chondrocytes that allowed their stable expression. Using this system, we screened more than 70 kb of the Col2a1 gene and found an enhancer domain that is responsible for the regulation of its expression level. The domain is localized in intron 7, and consists of an 800-bp region that contains within it a previously unidentified domain, ∼140 bp in size.

Oshiro A, Iseki S, Miyauchi M, Terashima T, Kawaguchi Y, Ikeda Y, Shinomura T. Lipopolysaccharide induces rapid loss of follicular dendritic cell‐secreted protein in the junctional epithelium. J Periodont Res 2012; 47: 689–694. © 2012 John Wiley & Sons A/SBackground and Objective:  We have previously reported that mRNA encoding follicular dendritic cell‐secreted protein (FDC‐SP) is expressed specifically in the junctional epithelium at the gingival crevice. Other tissues, such as tonsil, prostate gland and trachea, also express high levels of FDC‐SP. These tissues participate in a range of functions closely related to innate immunity. Therefore, it is hypothesized that FDC‐SP plays a crucial role in close association with the host defense system within the gingival crevice. Accordingly, the main aim of this study was to investigate the expression and localization of FDC‐SP in and around the junctional epithelium and to observe the dynamic changes of FDC‐SP in experimental inflammation.Material and Methods:  We examined, immunohistochemically, the expression of FDC‐SP in the junctional epithelium using a specific antibody raised in rabbit after immunization with a synthetic peptide derived from the hydrophilic region of FDC‐SP. Experimental inflammation was induced in the upper molars of Wistar rats by applying bacterial lipopolysaccharide (LPS; 5 mg/mL in sterile saline) for 1 h.Results:  We confirmed that FDC‐SP is present in the junctional epithelium in a pattern that is consistent with the expression of FDC‐SP mRNA. Of special interest is that no FDC‐SP was detectable in the junctional epithelium 3 h after transient topical treatment with LPS.Conclusion:  The presence of FDC‐SP in the junctional epithelium and its loss after LPS treatment strongly support our hypothesis of FDC‐SP playing a crucial role in close association with the host defense system within the gingival crevice.