Abstract 624: The Growth Factor Presenting Isoform CD44v3 is Highly Expressed During Collateral Artery Growth and Mediates Perfusion Restoration After Femoral Artery Ligation
Background: Arteriogenesis refers to the enlargement of pre-existent collateral arteries. We recently demonstrated that mice lacking CD44 show a hampered arteriogenic response after femoral artery occlusion. CD44 is a transmembrane molecule with a variety of different functions due to alternative splicing variants (e.g. cell-cell and cell-matrix interactions). Isoforms that contain CD44v3 can bind heparan sulphate side chains, which play a role in presentation and preservation of growth factors. We therefore hypothesized that among the CD44 isoforms, CD44v3 is essential for collateral growth and is upregulated in growing collateral vessels.
Materials and Methods: In 26 C57BL/6J mice the right femoral artery was ligated and the left hind limb was sham operated. At day 1, 3 and 7 the thigh muscles were harvested and snap frozen for isolation of RNA and histology. Furthermore, microsphere perfusion measurements were performed on day 7 in mice that lack the CD44v3 isoform (CD44v4 −10 knock-in mice) and in C57BL/6J mice.
Results: At day 3 a 25-fold increase in total CD44 mRNA and a 13-fold increase in CD44v3 mRNA were observed using RT-PCR (p<0.05). At day 1 and 7 no significant difference between the ligated and the non-ligated hind limb was found. Immunohistochemical analysis demonstrated that CD44v3 expression was limited to the vessel wall of growing collateral arteries. Perfusion in mice lacking CD44v3 was significantly reduced as compared to their genetic background (perfusion occluded vs. non-occluded hindlimb [%]: CD44v4 –10: 18.0±3.2; C57BL/6J: 55.5±9.2; p<0.05).
Conclusion: Both total CD44 as well as CD44v3 are upregulated during arteriogenesis. Absence of CD44v3 results in an attenuated collateral artery growth. This is the first study indicating the importance of the growth factor binding domain v3 of the CD44 molecule in arteriogenesis. This isoform might serve as a potential therapeutic target for the stimulation of collateral artery growth.