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116 stabilization of vulnerable plaques


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116 stabilization of vulnerable plaques

  1. 1. 1 STABILIZATION OFSTABILIZATION OF VULNERABLE PLAQUESVULNERABLE PLAQUES using Ultra Super Paramagnetic Iron Oxide and Ferromagnetic Hyperthermia
  2. 2. 2 Vulnerable AtheroscleroticVulnerable Atherosclerotic PlaquePlaque Large lipid core Thin Fibrous Cap Macrophage Infiltration (inflammation)
  3. 3. 3 Vulnerable PlaqueVulnerable Plaque
  4. 4. 4 Factors Responsible forFactors Responsible for Plaque InstabilityPlaque Instability Increased macrophage infiltration SMC apoptosis Collagen degradation Oxidized LDL Plaque angiogenesis Infection (CP, HSV, CMV) Systemic inflammation / infections (influenza)
  5. 5. 5 Factors Responsible forFactors Responsible for Plaque StabilityPlaque Stability Reduced Inflammation (Macrophage Apoptosis?) SMC Proliferation Collagen Production Lipid Lowering (lipid core)
  6. 6. 6 Methods of Stabilizing /Methods of Stabilizing / Treatment of PlaquesTreatment of Plaques Lipid lowering Stent Placement Anti inflammatory Photodynamic therapy Gene therapy Beta blockers ACE inhibitors Antioxidants Estrogen therapy Antibiotics
  7. 7. 7 Photodynamic TherapyPhotodynamic Therapy PDT is based on the use of light-sensitive compounds,photo sensitizers (PS), which can be activated by light of a specificwavelength that is matched to the absorption characteristic of the particular PS. Photo activation in the presence of tissue oxygenleads to the formation of cytotoxic-reactive oxygen species suchas singlet oxygen. Photo activation of PS thereforemay result in the damage of cellular components, eventually leadingto cell death. (Levy, 1994).
  8. 8. 8 The rationale forusing PDT in atherosclerosis is based on the observation thatvarious PS, such as porphyrins, phthalocyanines, and texaphyrins accumulate in the atherosclerotic plaque as compared with theadjacent normal vessel wall. Localintra-arterial application of light of the appropriate wavelengthto the atherosclerotic vessel therefore may reduce the narrowingof thevessel.
  9. 9. 9 Substances Used AsSubstances Used As PhotosensitizersPhotosensitizers porphyrins, Phthalocyanines(2.6 times more in plaques after 4 hours) Gadolinium texaphyrin Lutetium texaphyrin Tetracyclin Pheophorbide Mono-L-aspartyl chlorin e 6
  10. 10. 10 Texaphyrins in PDTTexaphyrins in PDT ( Lutetium Texaphyrins)( Lutetium Texaphyrins)  These are aromatic and highly colored compounds related to porphyrins.  Lutetium texaphyrin is a second generation PS.  It possesses a low energy maximum in the far red portion of the visible spectrum.  This provides for activation of these compounds by light that is capable of penetration through tissue and blood.  It is retained selectively in the macrophages in the atherosclerotic plaque in spite of rapid clearance from blood.
  11. 11. 11 ……ContinuedContinued It can be used in photo angioplasty and reduction of atherosclerotic plaque. The efficacy of Lutetium Texaphyrin has been demonstrated in animal models It is in phase I clinical trial for coronary artery procedure and in phase II for peripheral arteries.
  12. 12. 12 Left: Pretreatment angiogram of the femoral artery of a patientLeft: Pretreatment angiogram of the femoral artery of a patient showing the severe narrowing of this vessel caused byshowing the severe narrowing of this vessel caused by atherosclerosis. Right: One month after a single treatment withatherosclerosis. Right: One month after a single treatment with Lu-Tex-based ANTRINLu-Tex-based ANTRIN(TM)(TM) photosensitizer-based angioplasty,photosensitizer-based angioplasty, shows a 50% increase in the diameter of the arterial opening andshows a 50% increase in the diameter of the arterial opening and increased blood flow. Reproduced with permission.increased blood flow. Reproduced with permission. 98 Pharmacyclics Inc.98 Pharmacyclics Inc.
  13. 13. 13 Biodistribution of LutetiumBiodistribution of Lutetium TexaphyrinTexaphyrin (10mg/kg)(10mg/kg) Time Plasmaµg/g Muscleµg/g Tumorµg/g 3 hours 5.07 0.60 5.25 5 hours 4.72 0.46 1.96 12 hours 3.91 0.41 0.48 24 hours 2.79 0.40 0.18
  14. 14. 14 Uptake of Porphyrins inUptake of Porphyrins in arteries and plaquesarteries and plaques Hsiang (1993) found that porphyrins are taken up by human arteries in in-vitro studies. In in-vivo studies in miniswine these are taken up by the plaques and normal arteries in a ratio of 1.7-3.5 with a dose of 2.0mg/kg.
  15. 15. 15 Disadvantages of PDTDisadvantages of PDT Coagulation necrosis, cell cytotoxicity Burning plaque Skin photosensitivity and severe skin burns upon exposure to sun light  Even LT is not highly plaque specific.
  16. 16. 16 Selective Targeting of PSSelective Targeting of PS Selective targeting of PS to atherosclerotic plaque may reduce its possible side effects, such as skin hypersensitivity to sunlight Photo activation of cells loaded with Ox LDL- AlPc(aluminum phthalocyanine chloride) complexes resulted in selective cell death that correlated with the time of illumination. The cytotoxic effect of OxLDL-AlPc on leukemic murine macrophages is concentration- and incubation time-dependent.[Vries 1999]
  17. 17. 17 Effects of Gentle HeatingEffects of Gentle Heating Anti-Proliferative Effect of Heat Anti-inflammatory Effects of Heat Other Effects of Heat Mitra Rajabi:Mitra Rajabi: Mitra Rajabi:Mitra Rajabi:
  18. 18. 18 Anti-Proliferative Effect ofAnti-Proliferative Effect of HeatHeat Heat as well as other stressors (such as withdrawal of growth factors, lack of oxygen or glucose) can induce apoptosis, in a wide variety of cell types.
  19. 19. 19 AntiAnti--inflammatory Effects ofinflammatory Effects of HeatHeat  Reduced expression of pro inflammatory cytokines: TNF-α, IL-1 and IL-6 and many others cytokines that are important mediators of inflammation.  Temperatures between 40°- 45 °C or chemical inducers of heat shock proteins cause inhibition of both TNF alpha and IL-1 expression.  Inducing selective macrophage apoptosis.
  20. 20. 20 Effects of Heat onEffects of Heat on CollagenCollagen(cap strengthening)(cap strengthening)  Heat can increase expression of TGF-β 1 and VGEF which are well known for their effects on collagen and matrix production.  Low grade heat therapy has been shown to help the process of wound healing by increasing collagen production in several studies. Heated wounds showed increased collagen fibers which were denser, thicker, better arranged and more continuous, and the mean tensile strength of them was significantly greater than control group.
  21. 21. 21 Effects of Heat on LipidEffects of Heat on Lipid It has been shown that rise in temperature to 41ºC causes partial melting of the lipid crystals in rabbit atherosclerotic plaque At 45ºC most of the crystals melt. Small, Arterosclerosis 1988
  22. 22. 22 Effect of Heat on MMP ActivityEffect of Heat on MMP Activity Heat shock at 42°C preferentially suppresses the production and expression of MT1-MMP and thereby inhibits pro MMP- 2 (gelatinase) activation, events which subsequently inhibits tumor invasion Sato, 1999
  23. 23. 23 Disadvantages of Non-selectiveDisadvantages of Non-selective HyperthermiaHyperthermia Partial damage of the endothelial cell membrane (at 54ºC for 5-10 minutes) [Gabbiani,1984] Swelling of the endothelial cell nuclei (at43ºC for 12 minutes) [Emami, 1984] Sticking of the WBC’s to the vessel walls when heated, [Emami, 1984]
  24. 24. 24 Methods of InterstitialMethods of Interstitial HyperthermiaHyperthermia Radiofrequency Microwave Infrared Laser Focused Ultra Sound Extra corporeal heating of blood. Whole Body Hyperthermia
  25. 25. 25 Invasive  Catheters  Ferromagnetic Hyperthermia  Surgical implantation of NeedleThermo seed  Extra corporeal heating of blood. Non Invasive.  Inductive HT
  26. 26. 26 RF & Ferromagnetic HyperthermiaRF & Ferromagnetic Hyperthermia Because the layers of tissues within the human body have different water content and dielectric properties, deep pattern of exogenous energy absorption is highly non- uniform. To make hyperthermia clinically useful and feasible, it is essential that the heat delivery techniques be able to provide a sufficient heat dose within the whole site of interest while leaving surrounding normal tissue unaffected.
  27. 27. 27 Use of Ferromagnetic Micro ParticlesUse of Ferromagnetic Micro Particles for Interstitial / Intracellularfor Interstitial / Intracellular HyperthermiaHyperthermia Heat production by metal devices implanted directly into the tissues Thermoseeds absorb energy from an externally applied EM field in a non contact manner. Ferromagnetic microparticles and colloidal magnetic particles act like thermoseeds but in submicron and intracellualr level.
  28. 28. 28 Ferromagnetic particles act like self- contained heaters for which no cable connections are needed. They dissipate energy by various kinds of energy losses (eddy currents, hysteresis and residual loss) and cause heat on exposure to external alternating magnetic field.
  29. 29. 29 Amount of heat produced by ferromagnetic particles is a function of frequency (HZ) and power (W) of currents created by RF generator. It varies from gentle heating (1 ° -2 ° C rise) to aggressive heating and melting tissues (50°-70 ° C rise )
  30. 30. 30 Ex Vivo StudiesEx Vivo Studies 1989-94 Dextran Magnetite Complex was used to generate heat by exposing them to AC magnetic field. In 1994 Mitsumori compared heat generation in DM/Lipiodal emulsion and DM/Degradable starch micro sphere emulsions.
  31. 31. 31
  32. 32. 32 …….continued.continued 1999-Shinkai, used agar containing magnetite particles and heated them with MHz-RF capacitative device. It resulted in an increase in the temperature of the agar by 9ºC at 5minutes and by 24ºC at 9 minutes. 2000-Hilger, heated magnetite particles placed in cow muscle tissue with 400 kHz RF. Temperature elevation of up to 87ºC was observed at a distance of 15mm from the magnetite deposition area.
  33. 33. 33
  34. 34. 34 In Vivo Studies Using IronIn Vivo Studies Using Iron Oxide ParticlesOxide Particles 1981-Gordon used Iron particles with diameter of less than 1µ in rats and rabbits and exposed them to external high frequency electromagnetic field for 8- 10 minutes. The treated animals showed in a marked decrease in the lipid accumulation and intimal hyperplasia
  35. 35. 35 Submicron colloidal carbon iron particles could be observed immediatelySubmicron colloidal carbon iron particles could be observed immediately under the endothelium 5 hours after the administration, in mesentericunder the endothelium 5 hours after the administration, in mesenteric artery, in a ratartery, in a rat
  36. 36. 36 ……ContinuedContinued 1994- Mitsumori injected DM containing embolic material to renal arteries of rabbits and selectively heated the embolized kidney by exposure to AC magnetic field. The temperature of the kidney was raised 12.7º±3.1 during the initial 10 minutes.
  37. 37. 37 Iron Particles in the KidneyIron Particles in the Kidney
  38. 38. 38 ……continuedcontinued 1999-Shinkai, injected CMC-Magnetite (carboxy methyl complex) into the femur of pigs. 8 MHz-RF was used to heat the magnetite complex. The temperature in the CMC-Mag complex was increased to 43ºC after 7 minutes.
  39. 39. 39
  40. 40. 40 ……continuedcontinued 1998 Merkle and associates, injected 6 male NZ normal rabbits with ferumoxide and applied RF field for 8 minutes. Coagulative lesions were produced in the liver of the rabbits which were detected by MR imaging.
  41. 41. 41 Nonenhanced T1- weighted SE image (480/26 with three signals acquired) allows better visualization of the hypointense RF- induced lesion (arrows) [Merkle et al 1999- Radiology]
  42. 42. 42 SPIO, USPIOSPIO, USPIO Magnetic resonance imaging contrast medium with a central core of iron oxide generally coated by a polysaccharide layer Shortening MR relaxation time Phagocytosed and accumulated in cells with phagocytic activity
  43. 43. 43 SPIO in Macrophages
  44. 44. 44 SPIOs AND USPIOsSPIOs AND USPIOs These biocompatible particles are injectable and nontoxic agents that have the ability to dissipate the energy of radio frequency electro magnetic field in the form of heat. Can be useful in the site / cell specific hyperthermia treatment.
  45. 45. 45 In Vivo Hyperthermia UsingIn Vivo Hyperthermia Using CMIOCMIO(Colloidal Magnetic Iron Oxide)(Colloidal Magnetic Iron Oxide) Dr Chan and associates evaluated the effect of RF hyperthermia with CMIO injected mice. Mice were implanted with three types of human lung carcinoma cells. Tumors were exposed to RF field at 0.85 MHz for 6-10minutes.
  46. 46. 46 ……continuedcontinued Body vs tumor temperature differential of 6.5º-8.5ºC was reached. Dr. Chan’s studies demonstrated the ability to achieve clinically significant, site specific heating of the tumors.
  47. 47. 47  Uptake of Ferromagnetic particles by macrophages in the plaque.  Heating of the Ferromagnetic particles with low frequency magnetic field.  Increasing the temperature of the particles in the macrophages to within the febrile range (38º- 43ºC)  Apoptosis of the macrophages in the plaques leading to decreasing inflammation and increasing stability of the plaque. SPIO Heating of VulnerableSPIO Heating of Vulnerable PlaquesPlaques
  48. 48. 48 Our preliminary findings confirmed selective accumulation of ferromagnetic particles in the atherosclerotic plaque, RES system of the liver and spleen as well as lymph nodes.
  49. 49. 49 Apo-e Mice 1 and 3 DaysApo-e Mice 1 and 3 Days After Injection of FeridexAfter Injection of Feridex Pearl’s Staining Day1Day3
  50. 50. 50 HypothesesHypotheses Radiofrequency heating of USPIO injected animals for a short period of time (15-20 minutes at 42°-43°C) triggers apoptosis in macrophages containing these particles and therefore helps to stabilize the plaque by reducing inflammation. We also seek other beneficial effects of gentle heating on collagen production as seen in wound healing process, which may further help to stabilize vulnerable plaque by cap strengthening.
  51. 51. 51 Study DesignStudy Design Non-Invasive Using inductive RF heating Invasive Using Intravascular cooled tip RF catheter
  52. 52. 52 Using Intravascular catheter for applying radiofrequency For Non-Invasively heating the plaque we need to improve the bio-distribution of SPIOs to make them more plaque specific so that hyperthermia can be induced non- invasively
  53. 53. 53 Non-invasive Arm of theNon-invasive Arm of the StudyStudy 15 with RF H ypertherm ia 5 without RF H ypertherm ia 20m ice U SPIO injection 5 with RF H ypertherm ia 5 without RF H ypertherm ia 10 withoutinjectionType title here 30 M ice All animals sacrificed & then samples will be send for Pathologic evaluation for apoptosis  5 Days Later 12hours later
  54. 54. 54 Invasive Arm of the StudyInvasive Arm of the Study 5 rab b it w ith R F 5 ra b b it w ith o u t R F 1 0 ra b b it w ith U S P IO in je ctio n 5 ra b b its w ith R F 5 ra bb its w ith o u t R F 1 0 ra b b it w ith o u t in je ctio n 2 0 W H H L ra b b it After 5 days All animals sacrificed & then samples will be send for Pathologic evaluation for apoptosis After 12 hours
  55. 55. 55
  56. 56. 56 Future PlanFuture Plan Targeting of vulnerable plaque Ox-LDL – USPIO tagged with FC receptor for MDA epitope of Ox-LDL Adhesion Molecules -VCAM / ICAM - P-Selectin - CD39
  57. 57. 57
  58. 58. 58