title: Constitutive expression of inter-α-inhibitor (IαI) family proteins and tumor necrosis factor-stimulated gene-6 (TSG-6) by human amniotic membrane epithelial and stromal cells supporting formation of the heavy chain-hyaluronan (HC-HA) complex.
abstract: Recently, we reported HC-HA, a covalent complex formed between heavy chains (HCs) of inter-α-inhibitor (IαI) and hyaluronan (HA) by the catalytic action of tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6), is responsible for human amniotic membrane (AM) anti-inflammatory, anti-scarring, and anti-angiogenic actions. At the present time, the only well characterized source of IαI is serum being produced by the liver. This study showed that AM epithelial and stromal cells and stromal matrix all stained positively for HA, HC 1, 2, and 3, bikunin, and TSG-6. TSG-6 mRNA and protein were constitutively expressed by cultured AM epithelial and stromal cells without being up-regulated by TNF. In serum-free conditions, these cells expressed IαI, leading to the formation of HC-HA complex that contained both HC1 and HC2. In contrast, only HC1 was found in the HC-HA complex purified from AM. Local production of IαI, the HC-TSG-6 intermediate complex, and HC-HA were abolished when cells were treated with siRNA to HC1, HC2, bikunin (all of which impair the biosynthesis of IαI), or TSG-6 but not to HC3. Collectively, these results indicate that AM is another tissue in addition to the liver to constitutively produce IαI and that the HC-HA complex made by this tissue is different from that found at inflammatory sites (e.g. in asthma and arthritis) and in the matrix of the cumulus oocyte complex.
authors.affiliation: Ocular Surface Research and Education Foundation, Miami, Florida 33173, USA.
authors.forename: Suzhen
authors.initials: S
authors.lastname: Zhang
authors.forename: Hua
authors.initials: H
authors.lastname: He
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Day
authors.forename: Scheffer C G
authors.initials: SC
authors.lastname: Tseng
mesh_terms: D000510:Alpha-Globulins / Q000235:genetics / Q000378:metabolism*; D000650:Amnion / Q000166:cytology* / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004847:Epithelial Cells / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism*; D046911:Macromolecular Substances / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017154:Stromal Cells / Q000378:metabolism*
chemical_list: D000510:Alpha-Globulins; D015815:Cell Adhesion Molecules; D016895:Culture Media, Serum-Free; D046911:Macromolecular Substances; D020033:Protein Isoforms; C072273:TNFAIP6 protein, human; C016001:alpha-1-microglobulin; C011877:inter-alpha-inhibitor; D006820:Hyaluronic Acid