Fiber reinforced hydrated networks recapitulate the poroelastic mechanics of articular cartilage.

The role of poroelasticity on the functional performance of articular cartilage has been established in the scientific literature since the 1960s. Despite the extensive knowledge on this topic there remain few attempts to design for poroelasticity and to our knowledge no demonstration of an engineered poroelastic material that approaches the physiological performance. In this paper, we report on the development of an engineered material that begins to approach physiological poroelasticity. We quantify poroelasticity using the fluid load fraction, apply mixture theory to model the material system, and determine cytocompatibility using primary human mesenchymal stem cells. The design approach is based on a fiber reinforced hydrated network and uses routine fabrication methods (electrohydrodynamic deposition) and materials (poly[ɛ-caprolactone] and gelatin) to develop the engineered poroelastic material. This composite material achieved a mean peak fluid load fraction of 68%, displayed consistency with mixture theory, and demonstrated cytocompatibility. This work creates a foundation for designing poroelastic cartilage implants and developing scaffold systems to study chondrocyte mechanobiology and tissue engineering. STATEMENT OF SIGNIFICANCE: Poroelasticity drives the functional mechanics of articular cartilage (load bearing and lubrication). In this work we develop the design rationale and approach to produce a poroelastic material, known as a fiber reinforced hydrated network (FiHy™), that begins to approach the native performance of articular cartilage. This is the first engineered material system capable of exceeding isotropic linear poroelastic theory. The framework developed here enables fundamental studies of poroelasticity and the development of translational materials for cartilage repair.

Gene therapy progress and prospects: therapeutic angiogenesis for limb and myocardial ischemia.

After extensive investigation in preclinical studies and recent clinical trials, gene therapy has been established as a potential method to induce therapeutic angiogenesis in ischemic myocardial and limb disease. Advancements in viral and nonviral vector technology including cell-based gene transfer will continue to improve transgene transmission and expression efficiency. An alternative strategy to the use of transgenes encoding angiogenic growth factors is therapy based on transcription factors such as hypoxia-inducible factor-1alpha (HIF-1alpha) that regulate the expression of multiple angiogenic genes. Further understanding of the underlying biology of neovascularization is needed to determine the ability of growth factors to induce functionally significant angiogenesis in patients with atherosclerotic disease and associated comorbid conditions including endothelial dysfunction, which may inhibit blood vessel growth. The safety and tolerability of therapeutic angiogenesis by gene transfer has been demonstrated in phase I clinical trials. However, limited evidence of efficacy resulted from early phase II studies of angiogenic gene therapy for ischemic myocardial and limb disease. The utility of therapeutic angiogenesis by gene transfer as a treatment option for ischemic cardiovascular disease will be determined by adequately powered, randomized, placebo-controlled phase II and III clinical trials.

Gene transfer to induce angiogenesis in myocardial and limb ischaemia.

Stimulation of angiogenesis/arteriogenesis by gene transfer methods offers hope for treating patients with myocardial and peripheral limb ischaemia who are not candidates for standard revascularisation procedures. Preclinical studies showed that adenoviral and plasmid vectors encoding various angiogenic cytokines were capable of inducing functionally significant angiogenesis in vitro and in animal models of chronic myocardial ischaemia. Early clinical studies using VEGF121-, FGF-4- and VEGF165-encoding vectors showed a reasonable safety profile with promising results. However, significant advances in vector technology including regulatable and longer-term expression, delivery strategies (local and organ/tissue specific), clinical trial design, and outcome measure development are needed before this investigational treatment becomes reality.

Intramyocardial delivery of FGF2 in combination with radio frequency transmyocardial revascularization.

Therapeutic angiogenesis and percutaneous transmyocardial revascularization (PMR) are potentially synergistic modalities to improve myocardial perfusion. To evaluate the efficiency of FGF2 delivery into an area that has been radio frequency (RF) ablated, we studied two catheter-based delivery methods, a direct injection system (Stiletto) and a combined RF ablation-delivery system (RF-PMR). Four groups (n = 3/group) of pigs received six transendocardial injections of (125)I-FGF2/fluorescent microspheres with either the Stiletto or the RF-PMR catheter. RF-PMR injections were preceded by a 0.6 sec RF ablation step. After either 1 or 24 hr, hearts and other tissues were harvested. Intramyocardial deposition sites were located with UV light and isolated. Specific activity per site was expressed as a percentage of total activity injected per site corrected for quenching. Injection site recovery was high for both catheter systems (average = 88%) and systemic uptake was low (< 6% in the liver). FGF2 retention was significantly higher with the Stiletto than the RF-PMR catheter (Stiletto 1 hr 41% +/- 17%, 24 hr 26% +/- 10%, RF-PMR 1 hr 21% +/- 14%, 24 hr 13% +/- 8%; P < 0.001), principally explained by the differences in catheter design. The Stiletto has a retractable needle and is optimized for intramyocardial delivery, whereas infusion from the RF-PMR device occurs at the endocardial surface and relies on channels created during RF ablation. Overall, FGF2 retention after transendocardial intramyocardial delivery by the Stiletto or the RF-PMR system is significantly higher than previously observed for intracoronary, intravenous and intrapericardial delivery. In conclusion, the combination of RF ablation and growth factor delivery using the RF-PMR system is feasible and efficient. Cathet Cardiovasc Intervent 2001;53:429-434.

Combined percutaneous biosense-guided laser myocardial revascularization and coronary intervention.

Laser myocardial revascularization is a promising new treatment strategy for patients with severe ischemic heart disease who are not candidates for conventional percutaneous or surgical revascularization. The open chest surgical approach to transmyocardial revascularization has been approved by the FDA for the treatment of angina in inoperable patients, but has had limited use as a stand-alone procedure. More recently, use of fiber-optic catheters has made it possible to use a holmium:yttrium aluminum garnet laser to perform percutaneous catheter-based transmyocardial revascularization. To the extent that many patients have a combination of ischemic sources, some amenable to conventional revascularization and some not, combination or hybrid approaches have been considered. We report herein two patients with class IV angina who underwent laser myocardial revascularization using the Biosense system and complex percutaneous coronary intervention during the same procedure. Areas amenable to conventional percutaneous coronary intervention (PCI) were so treated, and viable but ischemic areas were supplied by totally occluded native vessels and bypass grafts underwent Biosense-guided laser myocardial revascularization (LMR). As the results of more controlled and blinded studies of laser myocardial revascularization become available (if results continue to be promising) and a better understanding of the mechanism of action of this treatment modality is achieved, LMR-PTCA hybrid will be performed in increasing frequency. However, even after establishing LMR efficacy, studies of LMR-PTCA hybrid should be conducted to determine the efficacy of this approach.

Angiogenesis (clinical trials).

Therapeutic angiogenesis may play a role in the treatment of patients with vascular disease who have no other treatment option (those who are not candidates for bypass surgery or angioplasty). The first published clinical trial results appeared in 1998 and additional trials have since been completed or are ongoing. Results of several of these trials are reviewed. Studies of angiogenesis with basic fibroblast growth factor and human vascular endothelial growth factor suggest that these growth factors can induce functionally significant angiogenesis. Evolving delivery modalities and strategies are also highlighted.

Pharmacokinetics and pharmacodynamics of recombinant FGF-2 in a phase I trial in coronary artery disease.

Fibroblast growth factor-2 (FGF-2) is a heparin-binding protein capable of inducing angiogenesis in multiple animal models of chronic ischemia. The pharmacokinetics and pharmacodynamics of a single dose of recombinant FGF-2 (rFGF-2) administered by intracoronary or intravenous infusion were evaluated in a Phase I trial in 66 patients with severe coronary artery disease. rFGF-2 displayed biphasic elimination with a mean studywide distribution t1/2 of 21 minutes and a mean apparent terminal elimination t1/2 of 7.6 hours. Systemic exposure to rFGF-2 was comparable following intracoronary or intravenous administration. Peak plasma concentration and area under the concentration-time curve increased proportionally with dose, indicating linear pharmacokinetics over the dose range examined (0.33 to 48.0 micrograms/kg). Greater systemic exposure was observed when heparin was administered closer to rFGF-2 infusion, consistent with slower clearance of heparin/rFGF-2 complexes. Infusion of rFGF-2 was associated with changes in acute hemodynamics. While a clear PK/PD dose-response relationship was not established, a trend toward hypotension and tachycardia with higher rFGF-2 doses was observed.

Comparison of endocardial electromechanical mapping with radionuclide perfusion imaging to assess myocardial viability and severity of myocardial ischemia in angina pectoris.

The assessment of left ventricular electromechanical activity using a novel, nonfluoroscopic 3-dimensional mapping system demonstrates considerable differences in electrical and mechanical activities within regions of myocardial infarction or ischemia. We sought to determine whether these changes correlate with indexes of myocardial perfusion, viability, or ischemia. A 12-segment comparative analysis was performed in 61 patients (45 men, 61 +/- 12 years old) with class III to IV angina, having reversible and/or fixed myocardial perfusion defects on single-photon emission computed tomographic perfusion imaging. A dual-isotope protocol was used, consisting of rest and 4-hour redistribution thallium images followed by adenosine technetium-99m sestamibi imaging. Average rest endocardial unipolar voltage (UpV) and local shortening (LS) mapping values were compared with visually derived perfusion scores. There was gradual and proportional reduction in regional UpV and LS in relation to thallium-201 uptake score at rest (p = 0.0001 and p = 0.0002, respectively) and redistribution studies (p = 0.0001 and p = 0.003, respectively). UpV > or = 7.4 mV and LS > or = 5.0% had a sensitivity of 78% and 65%, respectively, with a specificity of 68% and 67% for detecting viable myocardium. UpV values of 12.3 and 5.4 mV had 90% specificity and sensitivity, respectively, to predict viable tissue. UpV, but not LS, values differentiated between normal segments and those with adenosine-induced severe perfusion defects (11.8 +/- 5.3 vs 8.8 +/- 4.1 mV, p = 0.005). Catheter-based left ventricular assessment of electromechanical activity correlates with the degree of single-photon emission computed tomographic perfusion abnormality and can identify myocardial viability with a greater accuracy than myocardial ischemia.

Expression of vascular endothelial growth factor and its receptors is increased, but microvascular relaxation is impaired in patients after acute myocardial ischemia.

BACKGROUND: Vascular endothelial growth factor, a specific endothelial mitogen, plays an important role in myocardial angiogenesis. Previous work has demonstrated increased expression of vascular endothelial growth factor and its receptors in a rat myocardial infarction model, as well as in a pig model of chronic ischemia. The expression of vascular endothelial growth factor and other growth factors after acute myocardial ischemia in patients has not been examined. In this study we examined the expression of vascular endothelial growth factor and its receptors and the responsiveness of human atrial microvessels to vascular endothelial growth factor before and after acute ischemia. METHODS: Paired specimens of human atrial tissue were harvested before and after atrial devascularization (ligation) in 16 patients undergoing coronary bypass operations. RESULTS: The messenger RNA (reverse transcriptase-polymerase chain reaction) level of vascular endothelial growth factor and vascular endothelial growth factor receptor 1 were increased by 22.2% +/- 4.2% and 30.7% +/- 7.6%, respectively (P <.05), in the ischemic specimens as compared with the control specimens. Protein expression (Western blotting) of vascular endothelial growth factor and that of vascular endothelial growth factor receptor 1 also were increased significantly by 71.7% +/- 27.8% and 68.2% +/- 27.6%, respectively (P <.05). However, both RNA and protein expressions of another vascular endothelial growth factor receptor, vascular endothelial growth factor receptor 2, and fibroblast growth factor and fibroblast growth factor receptor 1 were unchanged. Reactivity of precontracted atrial vessels was examined with video microscopy. Vascular endothelial growth factor-induced (33.9% +/- 2.4% vs 18.3% +/- 2.8% in control and ischemic vessels, respectively; P <.05), fibroblast growth factor-induced (31.6% +/- 3.2% vs 15.8% +/- 4.1%, P <.05), and substance P-induced (84.5% +/- 3.7% vs 54.3% +/- 9.0%, P <.05) microvascular relaxations were decreased in ischemic samples and in the presence of N (G)nitro-L -arginine, whereas responses to sodium nitroprusside were unchanged (90.9% +/- 2.2% vs 91.2% +/- 2.0%). CONCLUSIONS: This study suggests that acute myocardial ischemia in patients results in increased expression of vascular endothelial growth factor but not fibroblast growth factor and that the functional activity of vascular endothelial growth factor receptors and that of other growth factors may be impaired.

Gene transfer for angiogenesis in coronary artery disease.

Angiogenesis is a promising novel therapeutic strategy to provide new venues for blood flow in patients with severe ischemic heart and peripheral vascular disease, who are not candidates for standard revascularization strategies. We describe the underlying mechanisms involved in physiologic and therapeutic angiogenesis, underscoring the relative importance of vasculogenesis, angiogenesis, and arteriogenesis. We then present the various gene transfer vectors including plasmid, viral, and cell-based vectors, and various delivery modalities. The available preclinical data are presented, followed by a description of preliminary clinical experience, with an emphasis on the preliminary nature of these results, which address safety and not efficacy. Finally, we discuss the promises and pitfalls of clinical angiogenesis and gene transfer studies, stressing the importance of proper design of clinical trials and adequate protection of research subjects.

Efficacy of intracoronary or intravenous VEGF165 in a pig model of chronic myocardial ischemia.

OBJECTIVES: We sought to optimize vascular endothelial growth factor (VEGF) treatment for therapeutic angiogenesis in myocardial ischemia, we explored the efficacy of five different regimens. BACKGROUND: Although VEGF165 is one of the most potent pro-angiogenic growth factors, VEGF165 treatment for myocardial ischemia has been hampered by low efficacy and dose-limiting hypotension after systemic or intracoronary delivery. METHODS: This study evaluated the effect of intravenous or intracoronary rhVEGF165 in the presence or absence of nitric oxide (NO) synthase inhibition in a porcine model of chronic myocardial ischemia. Forty-two Yorkshire pigs with chronically occluded left circumflex coronary arteries were randomly assigned to receive 10 microg/kg of VEGF165: 1) rapid (40 min) intravenous VEGF165 0.25 microg/kg/min, 2) slow (200 min) intravenous VEGF165 0.05 microg/kg/min, 3) rapid intracoronary VEGF165 0.25 microg/kg/min, 4) rapid intracoronary VEGF165 0.25 microg/kg/min + nitro-L-arginine methyl ester hydrochloride (L-NAME) or 5) rapid vehicle infusion. RESULTS: Intracoronary and intravenous VEGF165 induced hypotension. Intracoronary VEGF-induced hypotension was blocked by L-NAME. Coronary angiography three weeks after treatment showed improvement in collateral index in both intracoronary groups but not the intravenous VEGF165 groups. Likewise, myocardial blood flow and microvascular function in the ischemic territory improved in both intracoronary groups but not in the intravenous groups. Global and regional myocardial function showed no significant improvements in any groups. CONCLUSIONS: Intracoronary infusion of VEGF165 significantly improves blood flow to the ischemic myocardium. Concomitant administration of L-NAME inhibits VEGF-induced hypotension while most likely preserving VEGF-induced angiogenesis. Intravenous infusion of VEGF165 was not effective in augmenting either myocardial flow or function in this model.

Therapeutic angiogenesis in cardiology using protein formulations.

Therapeutic angiogenesis in cardiovascular disease aims at improving myocardial function by increasing blood flow to ischemic myocardium that is not amenable to traditional forms of revascularization. Preclinical data have provided proof of the concept that angiogenic growth factors such as fibroblast growth factor 2 (FGF-2) and vascular endothelium growth factor (VEGF) may indeed improve myocardial flow and function when administered in ways that ensure prolonged tissue exposure to these short-lived molecules. Although other cytokines have been shown to enhance angiogenesis in vivo, FGF-2 and VEGF have been most widely studied and may serve as prototype proangiogenic drugs. Currently, several delivery techniques that are clinically applicable are being studied with respect to tissue distribution and retention as well as angiogenic efficacy of FGF-2 and VEGF. Although tissue distribution and retention of FGF-2 after intramyocardial injection compares favorably with other routes of administration, efficacy studies are not yet conclusive. At the same time, different protein- and gene-based formulations are being investigated. Arguments for and against protein and gene therapy are presented, showing that protein-based therapy seems to have advantages over gene therapy at the present time, although continuous efforts should be made to increase the tissue exposure time after a single administration of protein. While delivery systems and growth factor formulations are being improved, double-blind, placebo-controlled trials designed with existing animal data in mind, are needed to firmly establish the utility of therapeutic angiogenesis in cardiovascular disease.

Intracoronary basic fibroblast growth factor (FGF-2) in patients with severe ischemic heart disease: results of a phase I open-label dose escalation study.

OBJECTIVES: Evaluate the safety, tolerability and preliminary efficacy of intracoronary (IC) basic fibroblast growth factor (bFGF, FGF-2). BACKGROUND: FGF-2 is a heparin-binding growth factor capable of inducing functionally significant angiogenesis in animal models of myocardial ischemia. METHODS: Phase I, open-label dose-escalation study of FGF-2 administered as a single 20-min infusion in patients with ischemic heart disease not amenable to treatment with CABG or PTCA. RESULTS: Fifty-two patients enrolled in this study received IC FGF-2 (0.33 to 48 microg/kg). Hypotension was dose-dependent and dose-limiting, with 36 microg/kg being the maximally tolerated dose. Four patients died and four patients had non-Q-wave myocardial infarctions. Laboratory parameters and retinal examinations showed mild and mainly transient changes during the 6-month follow-up. There was an improvement in quality of life as assessed by Seattle Angina Questionnaire and improvement in exercise tolerance as assessed by treadmill exercise testing (510+/-24 s at baseline, 561+/-26 s at day 29 [p = 0.023], 609+/-26 s at day 57 (p < 0.001), and 633+/-24 s at day 180 (p < 0.001), overall p < 0.001). Magnetic resonance (MR) imaging showed increased regional wall thickening (baseline: 34+/-1.7%, day 29: 38.7+/-1.9% [p = 0.006], day 57: 41.4+/-1.9% [p < 0.001], and day 180: 42.0+/-2.3% [p < 0.001], overall p = 0.001) and a reduction in the extent of the ischemic area at all time points compared with baseline. CONCLUSIONS: Intracoronary administration of rFGF-2 appears safe and is well tolerated over a 100-fold dose range (0.33 to 0.36 microk/kg). Preliminary evidence of efficacy is tempered by the open-label uncontrolled design of the study.

Therapeutic angiogenesis with recombinant fibroblast growth factor-2 improves stress and rest myocardial perfusion abnormalities in patients with severe symptomatic chronic coronary artery disease.

BACKGROUND: We report the effects of the administration of recombinant fibroblast growth factor-2 (rFGF-2) protein on myocardial perfusion using single photon emission computed tomography imaging in humans with advanced coronary disease. METHODS AND RESULTS: A total of 59 patients with coronary disease that was not amenable to mechanical revascularization underwent intracoronary (n=45) or intravenous (n=14) administration of rFGF-2 in ascending doses. Changes in perfusion were evaluated at baseline and again at 29, 57, and 180 days after rFGF-2 administration. In this uncontrolled study, perfusion scans were analyzed by 2 observers who were blinded to patient identity and test sequence; scans were displayed in random order, with scans from nonstudy patients randomly interspersed to enhance blinding. Combining all dose groups, a reduction occurred in the per-segment reversibility score (reflecting the magnitude of inducible ischemia) from 1.7+/-0.4 at baseline to 1.1+/-0.6 at day 29 (P:<0.001), 1.2+/-0.7 at day 57 (P:<0.001), and 1.1+/-0.7 at day 180 (P:<0.001). The 37 patients with evidence of resting hypoperfusion had evidence of improved resting perfusion: their per-segment rest perfusion score of 1.5+/-0. 5 at baseline decreased to 1.0+/-0.8 at day 29 (P:<0.001), 1.0+/-0.8 at day 57 (P:=0.003), and 1.1+/-0.9 at day 180 (P:=0.11). CONCLUSIONS: These preliminary data suggest that the administration of rFGF-2 to patients with advanced coronary disease resulted in an attenuation of stress-induced ischemia and an improvement in resting myocardial perfusion; these findings are consistent with a favorable effect of therapeutic angiogenesis.

Clinical trials in coronary angiogenesis: issues, problems, consensus: An expert panel summary.

The rapid development of angiogenic growth factor therapy for patients with advanced ischemic heart disease over the last 5 years offers hope of a new treatment strategy based on generation of new blood supply in the diseased heart. However, as the field of therapeutic coronary angiogenesis is maturing from basic and preclinical investigations to clinical trials, many new and presently unresolved issues are coming into focus. These include in-depth understanding of the biology of angiogenesis, selection of appropriate patient populations for clinical trials, choice of therapeutic end points and means of their assessment, choice of therapeutic strategy (gene versus protein delivery), route of administration, and the side effect profile. The present article presents a summary statement of a panel of experts actively working in the field, convened by the Angiogenesis Foundation and the Angiogenesis Research Center during the 72nd meeting of the American Heart Association to define and achieve a consensus on the challenges facing development of therapeutic angiogenesis for coronary disease.

Short- and intermediate-term clinical outcomes from direct myocardial laser revascularization guided by biosense left ventricular electromechanical mapping.

BACKGROUND: Direct myocardial revascularization (DMR) has been examined as an alternative treatment for patients with chronic refractory myocardial ischemic syndromes who are not candidates for conventional coronary revascularization. Methods and Results-We used left ventricular electromagnetic guidance in 77 patients with chronic refractory angina (56 men, mean age 61+/-11 years, ejection fraction 0.48+/-0.11) to perform percutaneous DMR with an Ho:YAG laser at 2 J/pulse. Procedural success (laser channels placed in prespecified target zones) was achieved in 76 of 77 patients with an average of 26+/-10 channels (range 11 to 50 channels). The rate of major in-hospital cardiac adverse events was 2.6%, with no deaths or emergency operations, 1 patient with postprocedural pericardiocentesis, and 1 patient with minor embolic stroke. The rate of out-of-hospital adverse cardiac events (up to 6 months) was 2.6%, with 1 patient with myocardial infarction and 1 patient with stroke. Exercise duration after DMR increased from 387+/-179 to 454+/-166 seconds at 1 month and to 479+/-161 seconds at 6 months (P=0.0001). The time to onset of angina increased from 293+/-167 to 377+/-176 seconds at 1 month and to 414+/-169 seconds at 6 months (P=0.0001). Importantly, the time to ST-segment depression (>/=1 mm) also increased from 327+/-178 to 400+/-172 seconds at 1 month and to 436+/-175 seconds at 6 months (P=0.001). Angina (Canadian Cardiovascular Society classification) improved from 3.3+/-0.5 to 2.0+/-1.2 at 6 months (P<0.001). Nuclear perfusion imaging studies with a dual-isotope technique, however, showed no significant improvements at 1 or 6 months. CONCLUSIONS: Percutaneous DMR guided by left ventricular mapping is feasible and safe and reveals improved angina and prolonged exercise duration for up to a 6-month follow-up.

Coronary angiogenesis: detection in vivo with MR imaging sensitive to collateral neocirculation--preliminary study in pigs.

PURPOSE: To assess the ability to track neovascularization over time with a magnetic resonance (MR) imaging technique sensitized to new intramyocardial collateral development as a means of evaluating therapeutic angiogenesis. MATERIALS AND METHODS: Magnetization preparation plus spatial frequency reordering was applied to distinguish new intramyocardial collateral vessels from normal circulation on the basis of geometric differences. A vascular occluder was inserted in 34 pigs, and they were assigned randomly to treatment groups with either placebo or angiogenic growth factor. Collateral extent determined with collateral-sensitive MR imaging was correlated with direct measurements by means of three-dimensional (3D) computed tomography (CT), coronary blood flow distribution determined with microspheres, and findings at histologic examination. Changes in the signal at collateral-sensitive MR imaging before and after treatment were assessed by two observers blinded to treatment. RESULTS: The collateral extent determined with collateral-sensitive MR imaging correlated well with findings at 3D CT (r = 0.95) and with microspheres (r = 0.86). Furthermore, the collateral extent determined with collateral-sensitive MR imaging increased significantly (P < .001) in response to the administration of an angiogenic growth factor but not to placebo. The correspondence of findings at collateral-sensitive MR imaging to collateral neovascularization was confirmed at histologic examination. CONCLUSION: The presence of intramyocardial collateral microvessels was accurately determined with collateral-sensitive MR imaging. The technique may be useful in clinical studies of therapeutic angiogenesis.

Intrapericardial delivery of fibroblast growth factor-2 induces neovascularization in a porcine model of chronic myocardial ischemia.

Therapeutic angiogenesis is a novel approach to the treatment of myocardial ischemia based on the use of proangiogenic growth factors to induce the growth of new blood vessels to supply the myocardium at risk. This study was designed to assess the safety and efficacy of a single intrapericardial injection of basic fibroblast growth factor (FGF-2) in a porcine model of chronic myocardial ischemia. Yorkshire pigs underwent ameroid placement around the left circumflex coronary artery. At 3 weeks, animals were randomized to receive a single intrapericardial injection of either saline (n = 10), 3 mg of heparin (n = 9), 3 mg of heparin + 30 microgram of FGF-2 (n = 10), 200 microgram of FGF-2 (n = 10), or 2 mg of FGF-2 (n = 10). Coronary angiography, microsphere flow, magnetic resonance functional, and perfusion imaging were performed before and 4 weeks after treatment, at which time histologic analysis was also performed on 3 animals in each group. In ischemic pigs, FGF-2 treatment resulted in significant increases in left-to-left angiographic collaterals and left circumflex coronary artery blood flow. These benefits were accompanied by improvements in myocardial perfusion and function in the ischemic territory, as well as histologic evidence of increased myocardial vascularity without any adverse effects. Not one of these benefits was seen in saline- or heparin-treated ischemic animals. A single intrapericardial injection of FGF-2 in a porcine model of chronic myocardial ischemia results in functionally significant myocardial angiogenesis, without any adverse outcomes. This mode of FGF-2 administration may prove to be a useful therapeutic strategy for the treatment of patients with ischemic heart disease.

Efficacy of intracoronary versus intravenous FGF-2 in a pig model of chronic myocardial ischemia.

BACKGROUND: Therapeutic angiogenesis in ischemic myocardium has been shown to be a feasible and effective strategy to improve regional blood flow and myocardial function. However, the optimal mode of growth factor administration still needs to be established. METHODS: Using a pig model of chronic myocardial ischemia, we evaluated the efficacy of intravenous and intracoronary infusion of FGF-2 at 2 and 6 microg/kg compared with a vehicle control. Improvement in myocardial perfusion and function was assessed by angiography, colored microspheres, and function and perfusion magnetic resonance imaging. RESULTS: Intracoronary 6-microg/kg FGF-2 increased angiographic collaterals (p = 0.046) and increased regional blood flow to the ischemic area from 0.36 +/- 0.07 to 0.59 +/- 0.08 mL/min/g at stress (vs control, p = 0.032). Also, after 6 microg/kg intracoronary FGF-2, ejection fraction, regional wall motion, and thickening improved significantly by 9.9% +/- 1.9%, 126% +/- 39%, and 13.8% +/- 3.6%, respectively. Intravenous FGF-2 and intracoronary 2 microg/kg FGF-2 were ineffective. CONCLUSIONS: A single 6-microg/kg intracoronary treatment with FGF-2 resulted in significant improvement in collateralization and regional and global function of chronically ischemic myocardium. Single intravenous infusion of FGF-2 was not effective in this model.