Mononuclear Leukocytes Bind to Specific Hyaluronan Structures on Colon Mucosal Smooth Muscle Cells Treated with Polyinosinic Acid:Polycytidylic Acid

Abstract

Inflammatory bowel disease (IBD) is a chronic disorder whose etiology is linked to triggering events, including viral infections, that lead to immunoregulatory dysfunction in genetically susceptible people. Characteristic pathological changes include increased mononuclear leukocyte influx into the intestinal mucosa as well as mucosal smooth muscle cell (M-SMC) hyperplasia. Virus infection or viral mimic [polyinosinic acid:polycytidylic acid (polyI:C)] treatment of human colon M-SMCs in vitro increases cell surface hyaluronan (HA), and nonactivated mononuclear leukocytes bind to virus-induced HA structures by interactions that involve the HA-binding receptor CD44. In this study, confocal microscopy reveals increased HA on poly I:C-treated M-SMC surfaces within 3 hours, arrayed in coat-like structures. By 17 hours, novel, lengthy cable structures are evident, and these are primarily responsible for mediating leukocyte adhesion. Immunohistochemical staining demonstrates components of the inter-alpha-trypsin inhibitor (IalphaI) complex in both coat-like and cable structures. M-SMCs co-treated with polyI:C and a polyclonal antibody to IalphaI display HA in coats but with diminished cables, and they bind significantly fewer leukocytes than M-SMCs treated with polyI:C alone. Western blot data suggest that heavy chains of IalphaI are specifically associated with cable structures. Staining of tissue sections from patients with IBD demonstrates the presence of HA in inflamed colon tissue, and shows that HA-associated IalphaI staining increases in the mucosa of inflamed IBD specimens compared to noninflamed sections from the same patient, establishing a probable link between the observations in vitro and the progression of the inflammatory process in IBD.

Small hyaluronan oligosaccharides induce inflammation by engaging both toll-like-4 and CD44 receptors in human chondrocytes

“…The identification of the TLR-4 and CD44 receptors as the target for 6-mer HA had previously been demonstrated by several studies [2,[17][18][30][31][32][33]. We recently reported that low molecular weight HA was able to stimulate inflammation in normal articular mouse chondrocytes [15][16].…”

BMP-7 Modulates Hyaluronan-Mediated Proximal Tubular Cell-Monocyte Interaction

“…This would suggest a specific effect of BMP-7 on the assembly of pericellular HA structures. The inter-␣-trypsin inhibitor (I␣I) family are a group of serum protease inhibitors, and previous studies utilizing colonic mucosal smooth muscle cells have suggested that the heavy chains of I␣I are critical to the formation HA-based cables (34). It was particularly noted that there was a marked attenuation of HA cable formation in the absence of serum.…”

Hyaluronan-dependent pericellular matrix☆

“…For example, the Cterminal lectin-like domain of versican has been shown to bind to multimeric tenascin-R and tenascin-C in a calcium-dependent manner, creating the possibility of crosslinking hyaluronan through non-covalent versican-tenascin-versican interactions [33,34]. Other studies have implicated inter-alpha trypsin inhibitor (IαI) as necessary for the formation of cell coats [35,36], for the maintenance of hyaluronan scaffold integrity during cumulus expansion [37], and for potentiating CD44-mediated leukocyte adhesion to hyaluronan-rich matrices [38,39]. IαI heavy chains are transferred from the chondroitin sulfate chain of IαI to the hyaluronan.…”

“…inflammation, viral infection, endoplasmic reticulum (ER) stress and hyperglycemia] and these fibers have specific leukocyte-binding properties [38,[44][45][46][47]. The hyaluronan chains from one cell often merge with those from other cells to form extremely large cables that can span many cell lengths.…”

“…Evidence for an anti-adhesive role of the pericellular matrix comes from several studies indicating that hyaluronan promotes cell detachment [72][73][74]. Surface coatings of purified hyaluronan and chondroitin sulfate proteoglycans are generally anti-adhesive and can form barriers to cell movement and create guidance pathways for neurite outgrowth or neural crest migration [38,[75][76][77]. Avoidance of hyaluronan and versican substrate coatings also occurs in fibroblasts and smooth muscle cells (Evanko and Wight, unpublished observations).…”