Deficiency of CD44 prevents thoracic aortic dissection in a murine model.

Thoracic aortic dissection (TAD) is a life-threatening vascular disease. We showed that CD44, a widely distributed cell surface adhesion molecule, has an important role in inflammation. In this study, we examined the role of CD44 in the development of TAD. TAD was induced by the continuous infusion of ß-aminopropionitrile (BAPN), a lysyl oxidase inhibitor, and angiotensin II (AngII) for 7 days in wild type (WT) mice and CD44 deficient (CD44-/-) mice. The incidence of TAD in CD44-/- mice was significantly reduced compared with WT mice (44% and 6%, p < 0.01). Next, to evaluate the initial changes, aortic tissues at 24 hours after BAPN/AngII infusion were examined. Neutrophil accumulation into thoracic aortic adventitia in CD44-/- mice was significantly decreased compared with that in WT mice (5.7 ± 0.3% and 1.6 ± 0.4%, p < 0.01). In addition, BAPN/AngII induced interleukin-6, interleukin-1ß, matrix metalloproteinase-2 and matrix metalloproteinase-9 in WT mice, all of which were significantly reduced in CD44-/- mice (all p < 0.01). In vitro transmigration of neutrophils from CD44-/- mice through an endothelial monolayer was significantly decreased by 18% compared with WT mice (p < 0.01). Our findings indicate that CD44 has a critical role in TAD development in association with neutrophil infiltration into adventitia.

CD44 Deficiency in Mice Protects the Heart Against Angiotensin Ii-Induced Cardiac Fibrosis.

This study tested the hypothesis that CD44 is involved in the development of cardiac fibrosis via angiotensin II (Ang II) AT1 receptor-stimulated TNFα/NFκB/IκB signaling pathways. Study was conducted in C57BL/6 wild type and CD44 knockout mice subjected to Ang II infusion (1,000 ng/kg/min) using osmotic minipumps up to 4 weeks or with gastric gavage administration of the AT1 receptor blocker, telmisartan at a dose of 10 mg/kg/d. Results indicated that Ang II enhances expression of the AT1 receptor, TNFα, NFκB, and CD44 as well as downregulates IκB. Further analyses revealed that Ang II increases macrophage migration, augments myofibroblast proliferation, and induces vascular/interstitial fibrosis. Relative to the Ang II group, treatment with telmisartan significantly reduced expression of the AT1 receptor and TNFα. These changes occurred in coincidence with decreased NFκB, increased IκB, and downregulated CD44 in the intracardiac vessels and intermyocardium. Furthermore, macrophage migration and myofibroblast proliferation were inhibited and fibrosis was attenuated. Knockout of CD44 did not affect Ang II-stimulated AT1 receptor and modulated TNFα/NFκB/IκB signaling, but significantly reduced macrophage/myofibroblast-mediated fibrosis as identified by less extensive collagen-rich area. These results suggest that the AT1 receptor is involved in the development of cardiac fibrosis by stimulating TNFα/NFκB/IκB-triggered CD44 signaling pathways. Knockout of CD44 blocked Ang II-induced cell migration/proliferation and cardiac fibrosis. Therefore, selective inhibition of CD44 may be considered as a potential therapeutic target for attenuating Ang II-induced deleterious cardiovascular effects.

Targeted deletion of HYBID (hyaluronan binding protein involved in hyaluronan depolymerization/ KIAA1199/CEMIP) decreases dendritic spine density in the dentate gyrus through hyaluronan accumulation.

HYBID (hyaluronan binding protein involved in hyaluronan [HA] depolymerization, KIAA1199/CEMIP) is a key player in HA depolymerization of the skin fibroblasts, arthritic synovial fibroblasts, and brain. Our previous study demonstrated that Hybid knock-out (KO) mice showed spatial memorial impairment, which is accompanied by the accumulation of high molecular weight HA in the hippocampus. However, the mechanism underlying cognitive impairment by Hybid deficiency remains unclear. In the present study, we examined the HA distribution patterns in the brains of wild-type (WT) and Hybid KO mice by HA staining using HA binding protein, and found that in Hybid KO mice, HA is accumulated and doublecortin-positive immature neurons are significantly decreased in the dentate gyrus of the hippocampus, where Hybid mRNA is highly expressed in WT mice. The Golgi-Cox staining demonstrated that the dendritic spine density is significantly decreased in the dentate gyrus granule cells in Hybid KO mice. These results suggest that Hybid-mediated HA degradation is critical for the synaptic formation process by contributing to cognitive functions, such as learning and memory, in the mouse brain.

CRISPR-Cas9-Mediated Silencing of CD44 in Human Highly Metastatic Osteosarcoma Cells.

BACKGROUND/AIMS: Metastasis is the major cause of death in patients with osteosarcoma. There is an urgent need to identify molecular markers that promote metastasis. Cluster of differentiation 44 is a receptor for hyaluronic acid (HA) and HA-binding has been proven to participate in various biological tumor activities, including tumor progression and metastasis. METHODS: We performed a meta-analysis to investigate the relationship between CD44 expression, survival, and metastasis in patients with osteosarcoma. We then utilized the CRISPR-Cas9 system to specifically silence CD44 in highly metastatic human osteosarcoma cells (MNNG/HOS and 143B) and further determined the functional effects of CD44 knockout in these cells. RESULTS: The meta-analysis demonstrated that a high level of CD44 may predict poor survival and higher potential of metastasis in patients with osteosarcoma. The expression of CD44 in highly metastatic human osteosarcoma cell lines was efficiently blocked by CRISPR-Cas9. When CD44 was silenced, the proliferation and spheroid formation of these osteosarcoma cells was inhibited under 3-D culture conditions. Furthermore, the migratory and invasive functions were also impaired in these highly metastatic osteosarcoma cells. CONCLUSION: These results suggest that developing new strategies to target CD44 in osteosarcoma may prevent metastasis and improve the clinical outcome of osteosarcoma patients.

Synthetic peptide TEKKRRETVEREKE derived from ezrin induces differentiation of NIH/3T3 fibroblasts.

Synthetic 14 AA peptide (Gepon) derived from the hinge region of ezrin, a protein that links cell surface molecules to intracellular actin filaments, accelerates and facilitates wound and ulcer healing in clinical applications. However, the molecular mechanisms underlying this phenomenon and involved in enhanced healing of wounds with Gepon are not yet understood. The purpose of current study was to investigate intracellular signaling pathways involved in the effect of this peptide on wild type and genetically modified (CD44 KO) NIH/3T3 embryonic mouse fibroblasts. Gepon treatment of NIH/3T3 cells resulted in morphological and biochemical changes, characteristic of differentiated fibroblasts. While treatment of NIH/3T3 cells with TGF-ß1 triggered the activation of both canonical and non-canonical signaling pathways, exposure of fibroblasts to Gepon activated only the ERK1/2 dependent pathway without modulating SMAD dependent signaling pathway. Knocking out hyaluronic acid CD44 receptor did not change Gepon or TGF-ß1 dependent activation of intracellular signaling pathways and assembling of α-SMA-positive filaments. Gepon dependent differentiation of NIH/3T3 fibroblasts is based on activation of ERK1/2 kinase, non-canonical intracellular signaling pathway. Our data suggest that the treatment of fibroblasts with Gepon triggers activation of the non-canonical (SMAD independent) intracellular signaling pathway that involves ERK1/2kinase phosphorylation. Activation of the MAPK signaling pathway and the increase in formation of α-SMA containing stress filaments induced by Gepon were independent on presence of CD44 receptor in NIH/3T3 fibroblasts. Thus, our observation designates the significance and sufficiency of MAPK pathway mediated activation of fibroblasts with Gepon for healing of erosion, ulcers and wounds.

CD44 is a key player in non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Cluster of differentiation (CD)44 regulates adipose tissue inflammation in obesity and hepatic leukocyte recruitment in a lithogenic context. However, its role in hepatic inflammation in a mouse model of steatohepatitis and its relevance in humans have not yet been investigated. We aimed to evaluated the contribution of CD44 to non-alcoholic steatohepatitis (NASH) development and liver injury in mouse models and in patients at various stages of non-alcoholic fatty liver disease (NAFLD) progression. METHODS: The role of CD44 was evaluated in CD44-/- mice and after injections of an αCD44 antibody in wild-type mice challenged with a methionine- and choline-deficient diet (MCDD). In obese patients, hepatic CD44 (n=30 and 5 NASH patients with a second liver biopsy after bariatric surgery) and serum sCD44 (n=64) were evaluated. RESULTS: Liver inflammation (including inflammatory foci number, macrophage and neutrophil infiltration and CCL2/CCR2 levels), liver injury and fibrosis strongly decreased in CD44-/- mice compared to wild-type mice on MCDD. CD44 deficiency enhanced the M2 polarization and strongly decreased the activation of macrophages by lipopolysaccharide (LPS), hepatocyte damage-associated molecular patterns (DAMPs) and saturated fatty acids. Neutralization of CD44 in mice with steatohepatitis strongly decreased the macrophage infiltration and chemokine ligand (CCL)2 expression with a partial correction of liver inflammation and injury. In obese patients, hepatic CD44 was strongly upregulated in NASH patients (p=0.0008) and correlated with NAFLD activity score (NAS) (p=0.001), ballooning (p=0.003), alanine transaminase (p=0.005) and hepatic CCL2 (p<0.001) and macrophage marker CD68 (p<0.001) expression. Correction of NASH was associated with a strong decrease in liver CD44+ cells. Finally, the soluble form of CD44 increased with severe steatosis (p=0.0005) and NASH (p=0.007). CONCLUSION: Human and experimental data suggest that CD44 is a marker and key player of hepatic inflammation and its targeting partially corrects NASH. LAY SUMMARY: Human and experimental data suggest that CD44, a cellular protein mainly expressed in immune cells, is a marker and key player of non-alcoholic steatohepatitis (NASH). Indeed, CD44 enhances the non-alcoholic fatty liver (NAFL) (hepatic steatosis) to NASH progression by regulating hepatic macrophage polarization (pro-inflammatory phenotype) and infiltration (macrophage motility and the MCP1/CCL2/CCR2 system). Targeting CD44 partially corrects NASH, making it a potential therapeutic strategy.