Inhibition of Platelet Recruitment to Arterial Lesions by Predeposition of Platelets Containing Encapsulated lloprost

Summary

Drugs can be encapsulated within blood platelets by reversible electroporation and can be haemostatically targeted to vessel wall injury sites. Initial studies with iloprost-loaded pig platelets and pig aorta tunica media in perfusion circuits are presented. After autologous reconstitution into blood, no significant difference was observed in the deposition of ¹¹¹Indium labelled sham-loaded and untreated platelets onto the tunica media during perfusion under low and high shear conditions. In paired experiments (n = 10 pairs), the deposition of iloprost-loaded platelets was significantly lower (mean 61%) after 5 min perfusion than the deposition from blood containing sham-loaded (control) platelets. A similar significant reduction (mean 54%) was seen after 10 min perfusion. Pre-perfusion of iloprost-loaded platelets for 10 min under low shear conditions (212/s), followed by 5 min perfusion of ¹¹¹Indium labelled normal platelets, significantly reduced the secondary platelet deposition (p <0.01) when compared with the deposition seen when control untreated platelets were preperfused. Significant differences (p <0.001) in secondary deposition were also observed when primary and secondary platelet perfusions were made under high shear (1690/s).

Histology of the tunica media segments post perfusion, supported the inhibitory effect of predeposited iloprost-loaded platelets on secondary platelet recruitment. By exploiting their natural haemostatic propensity, drug-loaded platelets can be targeted to vessel wall injury sites. Appropriate drugs could be packaged that may passivate the carrier platelets at the lesion inhibiting thrombus formation or they may act as a depot for sustained drug release. This platelet drug delivery strategy may have application in the prevention of the thrombotic and reste-notic events that can occur post angioplasty, or following therapy with thrombolytics, or after more invasive surgical procedures involving vascular reconstruction or prosthetic implantation.

• References

• 1 Forrester JS, Fishbein M, Helfant R, Fagin J. A paradigm for restenosis based on cell biology: Clues for the development of new preventive therapies. J Am Coll Cardiol 1991; 17: 758-69
• 2 Newby AC, George SJ. Proposed roles for growth factors in mediating smooth muscle proliferation in vascular pathologies. Cardiovasc Res 1993; 27: 1173-83
• 3 Ross R. The pathogenesis of atherosclerosis - an update. N Eng J Med 1986; 314: 758-69
• 4 Liu MW, Roubin GS, King SB III. Restenosis after coronary angioplasty. Potential biological determinants and role of intimal hyperplasia. Circula- tion 1989; 79: 1374-87
• 5 Stein B, Fuster V, Israel DH, Coen M, Badimon L, Badimon JJ, Chesebro JH. Platelet inhibitor agents in cardiovascular disease: An update. J Am Coll Cardiol 1989; 14: 813-36
• 6 Stein B, Fuster V, Halperin JL, Chesebro JH. Antithrombotic therapy in cardiac disease. An emerging approach based on pathogenesis and risk. Circulation 1989; 80: 1501-13
• 7 Badimon L, Chesebro JH, Badimon JJ. Thrombus formation on ruptured atherosclerotic plaques and rethrombosis on evolving thrombi. Circulation 1992; 86 suppl (Suppl. 03) 74-III-85
• 8 Lam JYT, Chesebro JH, Steele JH, Badimon L, Harris M, Fuster V. Antithrombotic therapy for arterial injury by angioplasty: Efficacy of common platelet inhibitors versus thrombin inhibition in pigs. Circulation 1991; 84: 814-20
• 9 Powell JS, Clozel JP, Muller RKM, Fuhn H, Hefti F, Hosan G. Inhibitors of angiotensin-converting enzyme prevent myointimal proliferation after vascular injury. Science 1989; 245: 186-8
• 10 Reidy MA, Bowyer DE. Control of arterial smooth muscle cell proliferation. Current Opinions in Lipidology 1993; 4: 349-55
• 11 Clowes AW, Karnowsky MJ. Suppression by heparin of smooth muscle cell proliferation in injured arteries. Nature 1977; 265: 625-6
• 12 Hughes K, Crawford N. Reversible electropermabilisation of human and rat platelets. Evaluation of morphological and functional integrity in vitro and in vivo. Biochem Biophys Acta 1989; 981: 277-87
• 13 Hughes K, Crawford N. Reversibly electropermeabilised platelets. Potential use as vehicles for drug delivery. Biochem Soc Trans 1990; 18: 871-3
• 14 El Gamal BAB, Pfliegler G, Crawford N. Effect of platelet encapsulated Iloprost on platelet aggregation and adhesion to collagen and injured blood vessels in vitro. Thromb and Haemost 1992; 68: 606-14
• 15 Fisher CA, Kappa JR, Sinha AK, Cottrell ED, Reiser MJ, Addonizio VP. Comparison of equimolar concentrations of Iloprost, prostacyclin and prostaglandin El on human platelet function. J Lab Clin Med 1987; 109: 184-90
• 16 Badimon L, Turitto VT, Rosemark JA, Badimon JJ, Fuster V. Characterisation of a tubular flow chamber for studying platelet interaction with biological and prosthetic materials. J Lab Clin Med 1988; 110: 706-18
• 17 Lassila R, Badimon JJ, Vallabhajosula S, Badimon L. Dynamic monitoring of platelet deposition on severely damaged vessel wall in flowing blood. Effects of different stenoses on thrombus growth. Arterioslerosis 1990; 10 (02) 306-15
• 18 Badimon L, Badimon JJ. Mechanisms of arterial thrombosis in non-parallel streamlines; platelet thrombi grow on the apex of stenotic severely injured vessel wall. Experimental study in a pig model. J Clin Invest 1989; 84: 1134-44
• 19 Badimon L, Fuster V, Chesebro JH, Dewanjee MK. New ex vivo radioisotopic method of quantitation of platelet deposition: Studies in four animal species. Thromb Haemostas 1983; 50: 639-44
• 20 Daman J, Regts J, Scherhof G. Transfer and exchange of phospholipid between small unilamellar liposomes and rat plasma high density lipoproteins. Biochim Biophys Acta 1981; 665: 538-45
• 21 Gregoriadis G, Senior J. Liposomes in vivo. A relationship between stability and clearance, in targeting of drugs with synthetic systems Gregoriadis G, Senior J, Poste G. eds New York: Plenum Press; 1986. pp 183-92
• 22 Rosen P, Schwippert B, Kaufmann L, Tschope D. Expression of adhesion molecules on the surface of activated platelets is diminished by PGI2-ana-logues and an NO (EDRF)-donor: a comparison between platelets of healthy and diabetic subjects. Platelets 1994; 5: 45-52