Platelets bind to hyaluronic acid through CD44 and induce a focal adhesion kinase dependent airway smooth muscle cell proliferation

• Platelets have been implicated as important players in the remodeling process, e.g. due to their ability to induce airway smooth muscle cell (ASMC) proliferation. The aim of the present study was to investigate the role of the extracellular matrix component hyaluronic acid (HA), the HA-binding surface receptor CD44 and focal adhesion kinase (FAK) in platelet-induced ASMC proliferation. The ability of ASMC to synthesize HA was investigated by fluorescent staining using biotinylated HA-binding protein and streptavidin conjugate. In addition, the interaction between ASMC and platelets was studied by fluorescent staining of the F-actin. We found that ASMC produced HA and that a CD44 blocking antibody and the hyaluronic acid synthase inhibitor 4-Methylumbelliferone (4-MU) inhibited platelet binding to the area surrounding the ASMC. Proliferation of ASMC was measured using the MTS-assay, and we found that the CD44 blocking antibody and 4-MU inhibited platelet-induced ASMC proliferation. We also found that co-culture of ASMC and platelets resulted in increased phosphorylation of FAK as detected by Western blot analysis. Furthermore, the FAKinhibitor PF 573228 inhibited platelet-induced ASMC proliferation. In conclusion, our findings demonstrate that HA, CD44 and FAK contribute to the increased ASMC proliferation caused by platelets. This event is initiated by an interaction between platelets CD44 and HA produced by the ASMC. These new findings may be important in understanding the interplay between ECM, platelets and ASMC in the remodeling process. In conclusion, our results demonstrate that FAK is phosphorylated and on that account activated during the CD44-dependent platelet/ASMC interaction and this contributes to proliferation of the ASMC. These new findings may be important in understanding the interplay between ECM, platelets and ASMC in the remodeling process.

Nyckelord

airway smooth muscle; airway remodeling

hyaluronic acid

CD44

focal adhesion kinase

MEDICINE

MEDICIN

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vet (ämneskategori)

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