The Role Of HA And CD 44 In The Airway Remodeling Of Chronic Asthmatic Rat Model

Objective1. To observe the expression of hyaluronan (HA) in lung tissue, the content of HA in Bronchoalveolar Lavage(BALF) and the expression of CD44 in asthmatic conditions.2. To observe the expression of ERKl/2, P-ERKl/2 and protein ratio of P-ERK1/2 to ERK1/2 in airway of chronic asthmatic rats.3. To analyze the correlation of HA content to the thickness of airway wall (WA/P), the thickness of smooth muscle layer(S/Pi), the content of smooth muscle cell nucleus (N/Pi), the expression of ERK1/2 as well as the expression of P-ERK 1/2 in asthmatic conditions. To analyze the correlation of CD44 expression to the thickness of airway (WA/Pi), the thickness of smooth muscle layer(S/Pi), the content of smooth muscle cell nucleus (N/Pi), the expression of ERK1/2 as well as the expression of P-ERK 1/2 in asthmatic conditions.4. To explore possible relationship between HA, CD44 and the proliferation of airway smooth muscle cell (ASMCs) in asthmatic conditions.Methods and Materials20 SD rats were randomly divided into 2 groups, normal control and asthmatic group. The histologic changes in airway remodeling in asthmatic conditions were analyzed by using hematoxylin-eosin staining , The expression of HA and CD 44 in airway were analyzed by using Histological Examination ,the content of HA in both lung tissue and BALF were measured by ELISA. the content of HA in lung tissue were aslo analyzed by using polyacrylamide gel electrophoresis of fluorophore-labeled saccharides (PAGEFS). The expression of CD 44,ERK1/2 and P-ERK1/2 were analyzed by using Western blot.Results1. The 8-week OVA-challenged rats showed a significant pathological changes , including an apparent increase in the thickness of airway wall and smooth musclelayer,matrix deposition, subepithelial fibrosis, angiogenesis ,eosinoph-ilia and the other inflammatory cells recruitment. Compared to normal control group (9.43±1.42), the thickness of the airway wall(WA/Pi) of asthmatic group(13.23±1.30)was significantly increased(n=10, P<0.01), Compared to normal control group (3.55±0.70), the thickness of the smooth muscle layer(S/Pi) of asthmatic group(4.47±0.77)was significantly increased(n=10, P<0.05),Compared to normal control group( 0.0303±0.0070), the content of smooth muscle cell nucleus (N/Pi) of asthmatic group ( 0.0435±0.0121) (n=10, P< 0.01).2. Compared to normal control group, there appeared to be more intense HA staining in subepithelia and around the smooth muscle bundles of asthmatic group . Compared to normal control group (7.05±0.70), the content of HA in lung tissue of asthmatic group (9.16±0.78) was significantly increased (n=10 , P<0.01), Compared to normal control group( 6.63±0.96)the content of HA in BALF of asthmatic group(7.64±1.05)was significantly increased(n=10, P<0.05).3. Compared to normal control group( 9.50±1.20),the expression of CD44 of asthmatic group(14.39±1.26)was significantly increased (n=10, P<0.01).4. Compared to normal control group(2.03±0.34),the expression of ERK 1/2 of asthmatic group(2.38±0.28) was significantly increased(n=10, P<0.05), Compared to normal control group(0.46±0.10), the expression of P-ERK1/2 of asthmatic group(0.62±0.12)was significantly increase( n=10, P<0.01), Compared to normal control group( 0.23±0.03), Protein ratio of P-ERK1/2 to ERK1/2 of asthmatic group(0.26±0.03) ( n=10, P<0.05).5 HA content positively correlated to the thickness of the airway wall (WA/Pi) (r=0.770,P<0.01) , the thickness of the smooth muscle layer(S/Pi) (r=0.700, P<0.05), the content of smooth muscle cell nucleus(N/Pi)(r=0.870, P<0.01), the expression of ERK1/2 (r=0.754, P<0.05) as well as the expression of P-ERK1/2 (r= 0.824, P<0.01) in asthmatic conditions, CD44 expression positively correlated to the thickness of the airway wall (WA/Pi) (r=0.692, P<0.05),the thickness of the smooth muscle layer(S/Pi)(r=0.673, P<0.05), the content of smooth muscle cell nucleus(N/Pi) (r=0.817, P<0.01), the expression of ERK1/2 (r=0.752, P<0.05)as well as the expression of P-ERK1/2 (r=0.809, P<0.01) in asthmatic conditions.ConclusionsOur results revealed an increased hyaluronic acid content associated with overexpression of CD44 and ERK1/2 in asthmatic group compared to normal control group , an significant correlation between HA content and some index of airway remodeling ,ERK1/2 expression as well as P-ERK1/2 expression in asthmatic conditions, an significant correlation between CD44 expression and some index of airway remodeling , ERK1/2 expression as well as P-ERK1/2 expression in asthmatic conditions. And we speculated that , in asthmatic conditions, the increased HA or/and CD44 may involve in the proliferation of airway smooth muscle cell(ASMCs)and the remodeling of airway partly by activating the ERK1/2.