Targeting of peptides to restenotic vascular smooth muscle cells using phage display in vitro and in vivo

Restenosis after angioplasty occurs in 30–40% of the treated patients. To develop a strategy to deliver drugs to restenotic lesions, we selected phages that bind to proliferating vascular smooth muscle cells (VSMC), from a random constraint 15-mer peptide phage display library. Phages were selected for binding to cultured primary aortic VSMC (in vitro biopanning) and selected for binding to denudated carotid arteries in mice (in vivo biopanning). In vitro biopanning did not result in a consensus sequence, but recurring FLGW and LASR amino acid motifs were identified. In vivo biopanning resulted in two consensus peptides 5G6 (CNIWGVVLSWIGVFPEC) and 5E5 (CESLWGGLMWTIGLSDC). Surprisingly, these two sequences were recovered after both in vitro and in vivo biopanning, but predominantly in vivo. Moreover, a strong recurring motif, IGR, was identified in the in vivo clones. The consensus phages 5G6 and 5E5 bind selectively to VSMC compared to other cell types. Furthermore, they bind preferentially to proliferating VSMC compared to VSMC that were growth arrested, and are effectively internalized by their target cells. The specific binding capacities of 5G6 and 5E5 phages suggest that these peptide sequences can be used for targeting of restenotic lesions, in which proliferating VSMC are the dominant cell type.