Experimental use of a modified fibrin glue to induce site-directed angliogenesis from the aorta to the heart

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

Deferoxamine-fibrin accelerates angiogenesis in a rabbit model of peripheral ischemia

The intramuscular (IM) injection of a modified fibrin meshwork plus deferoxamine was tested in a rabbit model of acute hind-limb ischemia. After excision of the left external iliac and femoral arteries, 12 rabbits at the Milwaukee Heart Institute were divided into two groups: control and fibrin meshwork plus deferoxamine (FDEF) IM. The rabbits underwent angiography before surgery, immediately after, and 1 month postoperatively. These data were compiled through counting by means of a grid overlay. Another 12 rabbits at the Vakhidov Center of Surgery, which did not undergo angiography, underwent lower limb-calf blood pressure (LCBP) measurements made immediately after surgery and at postoperative days 10, 20 and 30. Biopsies from thigh skeletal muscles of rabbits that had L-CBP measurements underwent alkaline phosphatase staining on day 30 to determine the percentage of biopsied area that was occupied by capillaries. The number of arteries and arterioles crossing 71 grid intersections immediately post-surgery decreased from 30.2 6 2.3 to 18.0 6 2.0 (p, 0.05). One month post-surgery this number increased to 29.2 6 2.4 in controls (p, 0.05 vs immediately post-surgery) and to 59.6 6 3.2 in the FDEF group (p, 0.001 vs immediately post-surgery). By day 30 the L-CBP ratio improved in the FDEF group (0.8 6 0.02) vs controls (0.3 6 0.04). By day 30 the capillary density increased from that of normal muscle tissue (198.6 6 12.9/mm2) to 292 612.4/mm2 in the FDEF group (p, 0.05), but decreased in the control group to 98.7 6 7.7/mm2. IM injection of FDEF considerably accelerated angiogenesis in severely ischemic hind-limb tissue in this model, making it a viable treatment method for clinical use in patients who have critical limb ischemia.

Hydrogels for therapeutic cardiovascular angiogenesis

Acute myocardial infarction (MI) caused by ischemia is the most common cause of cardiac dysfunction. While growth factor or cell therapy is promising, the retention of bioactive agents in the highly vascularized myocardium is limited and prevents sustained activation needed for adequate cellular responses. Various types of biomaterials with different physical and chemical properties have been developed to improve the localized delivery of growth factor and/or cells for therapeutic angiogenesis in ischemic tissues. Hydrogels are particularly advantageous as carrier systems because they are structurally similar to the tissue extracellular matrix (ECM), they can be processed under relatively mild conditions and can be delivered in a minimally invasive manner. Moreover, hydrogels can be designed to degrade in a timely fashion that coincides with the angiogenic process. For these reasons, hydrogels have shown great potential as pro-angiogenic matrices. This paper reviews a few of the hydrogel systems currently being applied together with growth factor delivery and/or cell therapy to promote therapeutic angiogenesis in ischemic tissues, with emphasis on myocardial applications.

Injectable extracellular matrix derived hydrogel provides a platform for enhanced retention and delivery of a heparin-binding growth factor

Injectable hydrogels derived from the extracellular matrix (ECM) of decellularized tissues have recently emerged as scaffolds for tissue-engineering applications. Here, we introduce the potential for using a decellularized ECM-derived hydrogel for the improved delivery of heparin-binding growth factors. Immobilization of growth factors on a scaffold has been shown to increase their stability and activity. This can be done via chemical crosslinking, covalent bonding, or by incorporating natural or synthetic growth factor-binding domains similar to those found in vivo in sulfated glycosaminoglycans (GAGs). Many decellularized ECM-derived hydrogels retain native sulfated GAGs, and these materials may therefore provide an excellent delivery platform for heparin-binding growth factors. In this study, the sulfated GAG content of an ECM hydrogel derived from decellularized pericardial ECM was confirmed by Fourier transform infrared spectroscopy and its ability to bind basic fibroblast growth factor (bFGF) was established. Delivery in the pericardial matrix hydrogel increased retention of bFGF both in vitro and in vivo in ischemic myocardium compared to delivery in collagen. In a rodent infarct model, intramyocardial injection of bFGF in pericardial matrix enhanced neovascularization by approximately 112% compared to delivery in collagen. Importantly, the newly formed vasculature was anastomosed with existing vasculature. Thus, the sulfated GAG content of the decellularized ECM hydrogel provides a platform for incorporation of heparin-binding growth factors for prolonged retention and delivery.

Improved myocardial perfusion and cardiac function by controlled-release basic fibroblast growth factor using fibrin glue in a canine infarct model

OBJECTIVE

Angiogenic therapy is emerging as a potential strategy for the treatment of ischemic heart disease but is limited by a relatively short half-life of growth factors. Fibrin glue (FG) provides a reservoir for controlled-release of growth factors. The aim of this study was to evaluate the effects of basic fibroblast growth factor (bFGF) incorporating FG on angiogenesis and cardiac performance in a canine infarct model.

METHODS

Acute myocardial infarction was induced by ligation of the left anterior descending coronary artery (LAD). Group I (n=6) underwent ligation of LAD alone. In Group II, transmural channels were created in the infarct area (n=6). In Group III, non-transmural channels were created to locate FG cylinders containing bFGF (n=6). Eight weeks after operation, myocardial perfusion was assessed by single photon emission computed tomography, cardiac function by echocardiography, and vascular development by immunohistochemical staining.

RESULTS

Total vascular density and the number of large vessels (internal diameter ≥50 μm) were dramatically higher in Group III than in Groups I and II at eight weeks. Only the controlled-release group exhibited an improvement in regional myocardial perfusion associated with lower defect score. Animals in Group III presented improved cardiac regional systolic and diastolic functions as well as global systolic function in comparison with the other two groups.

CONCLUSIONS

Enhanced and sustained angiogenic response can be achieved by controlled-release bFGF incorporating FG within transmyocardial laser channels, thus enabling improvement in myocardial perfusion and cardiac function.

The hemodynamic behavior of arterial anastomosis using fibrin sealant: experimental study in swine

The wide use of biological sealants as a reinforcement for arterial sutures and the small experimental base in literature motivated this study. Our aim was to evaluate the flow, tear pressure, and the need of reinforcement stitches in sutured arteries after a cross-section. This research project complied with the Helsinki convention. The Tissucol (Baxter) fibrin sealant was used in all experiments. The femoral and carotid arteries of 17 swine from the same breed (weighing from 15 to 20 kg) were cross-sectioned after heparinization and subjected to anastomoses using a single continuous plane of 7-0 prolene. We worked with 68 artery samples, 34 in the treatment group and 34 in the control group. For each animal, one carotid and one femoral artery randomly received fibrin sealant with the contralateral side being used as a control. The need and the number of reinforcement stitches were recorded. Ten minutes after protamine infusion, the animals were sacrificed and the arteries were catheterized respecting 1 cm proximal and distal. The arteries were measured and placed on a flow meter to evaluate the flow rate of 10 mL of 0.9% NaCl in a 50 cm high column. The arteries were then subjected to air infusion at increasingly higher pressures (stepwise increases of 25 mm Hg), the grafts were dipped in 0.9% NaCl solution, the first air leakage was observed, and the tear pressure recorded. Data was analyzed with EpiInfo 6 data manager. The external diameters and thickness of the arteries were similar in both the treatment and control group. There was no significant difference between the groups regarding the tear pressure (P = 0.329), flow rate (P = 0.943), and the number of samples with a tear pressure above 200 mm Hg. However, the sealant reduced the number of reinforcement stitches necessary (P = 0.029). We conclude that fibrin sealant reduces the need of additional stitches; however, it does not change the tear pressure nor significantly reduces the flow.

Netrin-1 induces angiogenesis via a DCC-dependent ERK1/2-eNOS feed-forward mechanism

Netrin-1 is critical for axonal pathfinding which shares similarities with formation of vascular network. Here we report that netrin-1 induction of angiogenesis is mediated by an increase in endothelial nitric oxide (NO*) production, which occurs via a DCC-dependent, ERK1/2-eNOS feed-forward mechanism. Exposure of mature aortic endothelial cells to netrin-1 resulted in a potent, dose-dependent increase in NO* production, detected by electron spin resonance. Scavenging NO* with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) abolished netrin-1 stimulated angiogenesis. Netrin-1-stimulated NO* production or angiogenesis was inhibited by DCC antibody, DCC small interfering RNA (siRNA), specific inhibitors (PD98059, U0126), or siRNAs for MEK1/2. PTIO attenuated ERK1/2 phosphorylation, indicating a feed-forward mechanism. Netrin-1 induced a time-dependent phosphorylation of eNOS(s1179, s116) and a rapid dephosphorylation of eNOS(t497). Only eNOS(s1179) was sensitive to U0126 or PTIO. These data characterized a mechanism whereby netrin-1 promotes angiogenesis, which may broadly relate to cardiovascular, neuronal and cancer physiology.

The efficacy of fibrin sealant in prevention of anastomotic leak after laparoscopic gastric bypass

BACKGROUND

Anastomotic leak after laparoscopic gastric bypass (GBP) can result in significant morbidity, mortality, and consumption of healthcare resources. Fibrin sealant has been used clinically in the prevention of leak; however, its efficacy has not been clearly demonstrated. The aims of this study were to (1) develop an iatrogenic leak model in swine, (2) examine the efficacy of fibrin sealant in sealing iatrogenic anastomotic leak, and (3) review our experience with the use of fibrin sealant in 66 patients who underwent laparoscopic GBP.

METHODS

This study was performed in three phases. In phase 1, laparoscopic gastrojejunostomy was performed in adult swine with iatrogenic disruption of the anastomotic staple line. The size of disruption was sequentially increased (6- to 12-F opening) until a leak model was developed. In phase 2, 16 animals underwent laparoscopic gastrojejunostomy with a 12-F disruption of the anastomosis; 10 animals (study group) had fibrin sealant (Tisseel VH) applied on the disrupted anastomosis and 6 animals (control group) did not receive fibrin sealant. Animals were sacrificed on postoperative day 5 or earlier if peritonitis developed and were examined for sealing of the anastomotic disruption and the presence of intraabdominal abscess. In phase 3, the outcome of 66 consecutive patients who underwent laparoscopic GBP with fibrin sealant applied at the gastrojejunostomy was reviewed.

RESULTS

In phase 1, an anastomotic leak model was developed with a 12-F disruption of the staple line. In phase 2, two control animals required early sacrifice for bile peritonitis; three control animals had intraabdominal abscess discovered at sacrifice and one animal did not have any evidence of intraabdominal abscess or leak. Of the 10 animals in the study group, all survived until sacrifice and none of these animals had evidence of intraabdominal abscess or persistent leak. Therefore, 83% of animals in the control group developed either leak or abscess compared to 0% in the study group (P < 0.01, Fisher's exact test). Clinically, no leak or intraabdominal abscess developed in 66 patients who underwent laparoscopic GBP with the use of fibrin sealant.

CONCLUSIONS

An anastomotic leak model was developed in swine with disruption of the stapled gastrojejunostomy to a 12-F opening. The use of fibrin sealant significantly reduces leak and abscess complication. Our results support the tissue sealing property of fibrin sealant and its use on high-risk gastrointestinal anastomosis.

Biopolymeric delivery matrices for angiogenic growth factors

The development of new therapeutic approaches that aim to help the body exert its natural mechanisms for vascularized tissue growth (therapeutic angiogenesis) has become one of the most active areas of tissue engineering. Through basic research, several growth factor families and cytokines that are capable to induce physiological blood vessel formation have been identified. Indeed, preclinical and clinical investigations have indicated that therapeutic administration of angiogenic factors, such as the prototypic vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF), to sites of ischemia in the heart or the limb can improve regional blood flow. For new and lasting tissue vascularization, prolonged tissue exposure to these factors could be critical. Furthermore, as shown for VEGF, dosage must be tightly controlled, as excess amounts of VEGF can cause severe vascular leakage and hypotension. This review emphasizes natural and synthetic polymer matrices with respect to their development as vehicles for local and controlled delivery of angiogenic proteins, such as VEGF and bFGF, and their clinical applicability. In the dawn of experimental vascular engineering, new biomaterial schemes for clinical growth factor administration that take better account of biological principles of angiogenic growth factor function and the cell biological basis necessary to produce functional vasculature are evolving. Alongside their base function as protective embedment for angiogenic growth factors, these new classes of bioactive polymers are engineered with additional functionalities that better preserve growth factor activity and more closely mimic the in vivo release mechanisms and profiles of angiogenic growth factors from the extracellular matrix (ECM). Consequently, the preparation of both natural or completely synthetic materials with biological characteristics of the ECM has become central to many tissue engineering approaches that aim to deliver growth factors in a therapeutically efficient mode. Another promising venue to improve angiogenic performance is presented by biomaterials that allow sequential delivery of growth factors with complementary roles in blood vessel initiation and stabilization.

Engineered fibrin matrices for functional display of cell membrane-bound growth factor-like activities: Study of angiogenic signaling by ephrin-B2

With the rapid increase in approaches to pro- or anti-angiogenic therapy, new and effective methodologies for administration of cell-bound growth factors will be required. We sought to develop the natural hydrogel matrix fibrin as platform for extensive interactions and continuous signaling by the vascular morphogen ephrin-B2 that normally resides in the plasma membrane and requires multivalent presentation for ligation and activation of Eph receptors on apposing endothelial cell surfaces. Using fibrin and protein engineering technology to induce multivalent ligand presentation, a recombinant mutant ephrin-B2 receptor binding domain was covalently coupled to fibrin networks at variably high densities. The ability of fibrin-bound ephrin-B2 to act as ligand for endothelial cells was preserved, as demonstrated by a concomitant, dose-dependent increase of endothelial cell binding to engineered ephrin-B2-fibrin substrates in vitro. The therapeutic relevance of ephrin-B2-fibrin implant matrices was demonstrated by a local angiogenic response in the chick embryo chorioallontoic membrane evoked by the local and prolonged presentation of matrix-bound ephrin-B2 to tissue adjacing the implant. This new knowledge on biomimetic fibrin vehicles for precise local delivery of membrane-bound growth factor signals may help to elucidate specific biological growth factor function, and serve as starting point for development of new treatment strategies.

Delivery of high dose VEGF plasmid using fibrin carrier does not influence its angiogenic potency

Delivery of DNA mixed with a degradable matrix carrier was supposed to improve transgene expression. Using a rabbit hind-limb ischemia model, we tested the angiogenic potency of plasmid encoding human vascular endothelial growth factor (pSG5-VEGF165) entrapped in fibrin sealant. Animals were injected intramuscularly with 500 microg of pSG5-VEGF165 or control plasmid, dissolved in saline (PBS) or fibrin glue. After 14 days, presence of delivered constructs and expression of transgene was confirmed in injected muscles of all animals. There were no significant differences in the levels of human VEGF mRNA and protein between VEGF-PBS and VEGF-fibrin groups (Mann-Whitney test). Accordingly, pSG5-VEGF165 regardless of the way of delivery, induced similar increases in capillary density within treated muscles (ANOVA). Control plasmid did not show any effects. In conclusion, injection of pSG5-VEGF165 into ischemic adductor muscle leads to synthesis of human VEGF and increases the number of capillaries. Fibrin carrier does not influence its angiogenic potential.

Deferoxamine enhances neovascularization and recovery of ischemic skeletal muscle in an experimental sheep model

BACKGROUND

Iron chelators have been reported to interfere with inflammatory cells and possibly enhance vascular growth factor expression. The objective of this study was to investigate the efficacy of the iron chelator deferoxamine mesylate in preventing skeletal muscle ischemia.

METHODS

The latissimus dorsi muscle (LDM) was mobilized in 20 adult sheep. Two separate pockets were created in each sheep. Autologous fibrin sealant with or without 100 mg/mL of deferoxamine mesylate (10 pockets) was added to the pockets. Deferoxamine mesylate alone was also applied to another 10 pockets, whereas the 10 other pockets served as controls.

RESULTS

Conventional, indirect immunofluorescent enface staining showed that in nonmobilized, nonischemic LDM the capillary density was 196 +/- 14 capillaries/mm2 in the distal and 207 +/- 19 capillaries/mm2 in the middle part. After severe ischemic shock (subtotal mobilization), the muscle did not recover completely even after 2 months (149 +/- 15 capillaries/mm2 in the distal part and 177 +/- 16 capillaries/mm2 in the middle part of the LDM). Fibrin application only increased muscle neovascularization. The number of capillaries per mm2 of muscle increased to 250 +/- 25 in the distal part and to 271 +/- 24 in the middle part of the LDM. However, when fibrin was applied with added deferoxamine mesylate, the capillary density increased to 361 +/- 25 capillaries/mm2 in the distal part (p < 0.05 vs fibrin only; controls) and to 401 +/- 20 capillaries/mm2 in the middle part of the LDM (p < 0.05 vs fibrin only and p < 0.001 vs controls). The data are concordant with the blood flow estimation before and after mobilization (severe ischemic shock) in the different parts of the LDM.

CONCLUSIONS

Local application of deferoxamine mesylate enhances neovascularization and recovery of surgically induced skeletal muscle ischemia in a sheep model.

Therapeutic angiogenesis: a fantastic new adventure

A significant proportion of patients with coronary artery disease have symptoms refractory to medical treatment, yet are unsuitable for conventional revascularization techniques, like percutaneous coronary intervention and coronary artery bypass surgery. Such patients are potential candidates for alternative forms of coronary revascularization, like therapeutic angiogenesis. This strategy is designed to promote the development of supplemental collateral blood vessels that will act as endogenous bypass conduits. Two major avenues for achieving therapeutic angiogenesis are currently under intense investigation: gene therapy (the introduction of new genetic material into somatic cells to synthesize proteins that are missing, defective, or desired for specific therapeutic purposes) and protein-based therapy (administration of the growth factors, instead of the genes encoding for the growth factors responsible for angiogenesis). This article provides a concise review of the "components" of gene and protein-based therapy, namely, the growth factors, the vector (for gene therapy), the route of delivery, the therapeutic target, the desired therapeutic effect, and quantifiable clinical end points for trials of angiogenesis. Based on preliminary studies, the authors believe that therapeutic angiogenesis represents a promising novel therapy for treatment of the ischemic heart. In the future, angiogenesis will likely be offered as an adjunct to conventional revascularization strategies in subsets of patients who are only "suboptimally" revascularized with conventional techniques, and might evolve into a stand-alone treatment for some patients with nonrevascularizable disease.

The use of fibrin glue in skin grafts and tissue-engineered skin replacements: a review

Fibrin glue has been widely used as an adhesive in plastic and reconstructive surgery. This article reviews the advantages and disadvantages of its use with skin grafts and tissue-engineered skin substitutes. Fibrin glue has been shown to improve the percentage of skin graft take, especially when associated with difficult grafting sites or sites associated with unavoidable movement. Evidence also suggests improved hemostasis and a protective effect resulting in reduced bacterial infection. Fibrin, associated with fibronectin, has been shown to support keratinocyte and fibroblast growth both in vitro and in vivo, and may enhance cellular motility in the wound. When used as a delivery system for cultured keratinocytes and fibroblasts, fibrin glue may provide similar advantages to those proven with conventional skin grafts. Fibrin glue has also been shown to be a suitable delivery vehicle for exogenous growth factors that may in the future be used to accelerate wound healing.

A prospectus on tissue adhesives

Tissue adhesives are common adjuncts in surgical practice. Fibrin sealants are the most prevalent adhesives today. Recently, new adhesives have been approved for use in the United States, including cyanoacrylates, albumin-based compounds, collagen-based compounds, glutaraldehyde glues, and hydrogels. This review summarizes all the available tissue adhesives, focusing on their current and prospective indications in the clinical forum.

Covalently conjugated VEGF--fibrin matrices for endothelialization

Vascular endothelial growth factor (VEGF) is a key factor in endothelial cell biology and blood vessel formation and a candidate therapeutic for the stimulation of angiogenesis-dependent tissue regeneration. The objective of this study was to confer the angiogenic activity of VEGF(121) upon the biomaterial fibrin, a natural substrate for endothelial cell growth and clinically accepted as 'fibrin glue'. To achieve this, we engineered fibrin-based hydrogels that were covalently modified with VEGF(121). Our laboratory has recently developed novel methodology that allows the covalent incorporation of exogenous bioactive peptides by the transglutaminase activity of factor XIIIa into fibrin during coagulation. Here, this ability of factor XIIIa to crosslink additional proteins within fibrin was employed to covalently incorporate VEGF(121). By recombinant DNA methodology, a mutant VEGF(121) variant, alpha(2)-PI(1--8)-VEGF(121), which contains an additional factor XIIIa substrate sequence NQEQVSPL at the aminoterminus, was expressed in E. coli. In soluble form, the mutant protein fully retained its mitogenic activity for endothelial cells. Using (125)I-labeled alpha(2)-PI(1--8)-VEGF(121), its covalent incorporation and the efficiency of incorporation into fibrin was demonstrated and characterized. The immobilized, fibrin-conjugated VEGF(121) protein remained an active and very efficient mitogen for human endothelial cells grown on two-dimensional VEGF(121)-modified fibrin surfaces, and the incorporation of increasing amounts of alpha(2)-PI(1--8)-VEGF(121) resulted in dose-dependent enhancement of endothelial cell growth. The VEGF-modified fibrin matrices can be formed as injectable gels in a single-step reaction under physiological conditions in vivo. When used as a ingrowth matrix, such VEGF incorporating materials could be useful in a variety of clinical situations that require an angiogenic response into an ischemic region or inplant.

Angiogenesis in ischemic human myocardium: clinical results after 3 years

BACKGROUND

Using the human fibroblast growth factor we could already demonstrate the induction of neoangiogenesis in the ischemic human myocardium.

METHODS

Forty patients, who were undergoing elective coronary artery bypass grafting were randomly selected and allotted either to a treatment or a control group. In 20 patients (study group) fibroblast growth factor was injected directly into the myocardium, close to the left anterior descending coronary artery. The control group comprised 20 patients who had been injected with heat denatured fibroblast growth factor. The 3-year follow-up consisted of a clinical examination, echocardiography, and selective imaging of the internal mammary artery bypass using angiography.

RESULTS

As with the early results, a dense new capillary network could be demonstrated angiographically in the region where the factor had been injected. Echocardiography showed an increase in the left ventricular ejection fraction in the study group. We also found a more pronounced improvement in the clinical appearance of the patients with fibroblast growth factor.

CONCLUSIONS

Fibroblast growth factor, in addition to operative myocardial revascularization, may be the appropriate treatment for patients with peripheral stenosis or diffuse coronary arteriosclerosis. It is necessary to confirm these results in further studies on a larger group of patients.

Angiogenic potential of perivascularly delivered aFGF in a porcine model of chronic myocardial ischemia

A number of heparin-binding growth factors, including basic (bFGF) and acidic (aFGF) fibroblast growth factors have been shown to promote angiogenesis in vivo. In this study, we employed a sustained-release polymer extravascular delivery system to evaluate the angiogenic efficacy of a novel form of genetically modified aFGF in the setting of chronic myocardial ischemia. Fifteen Yorkshire pigs subjected to Ameroid occluder placement on the left circumflex (LCX) artery were treated with perivascularly administered aFGF in ethylene vinyl acetate (EVAc) polymer (10 micrograms, n = 7) or EVAc alone (controls, n = 8). Seven to nine weeks later, after coronary angiography to document Ameroid-induced coronary occlusion, all animals underwent studies of coronary flow and global and regional left ventricular function. Microsphere-determined coronary flow in the Ameroid-compromised territory was significantly increased in aFGF-treated compared with control animals, and this improvement in perfusion was maintained during ventricular pacing. Left ventricular function studies demonstrated improved global and regional function in aFGF-treated animals. We conclude that local perivascular delivery of genetically modified aFGF results in significant improvement in myocardial flow and regional and global left ventricular function.

Induction of neoangiogenesis in ischemic myocardium by human growth factors: first clinical results of a new treatment of coronary heart disease

BACKGROUND

The present article is a report of our animal experiments and also of the first clinical results of a new treatment for coronary heart disease using the human growth factor FGF-I (basic fibroblast growth factor) to induce neoangiogenesis in the ischemic myocardium.

METHODS AND RESULTS

FGF-I was obtained from strains of Escherichia coli by genetic engineering, then isolated and highly purified. Several series of animal experiments demonstrated the apathogenic action and neoangiogenic potency of this factor. After successful conclusion of the animal experiments, it was used clinically for the first time. FGF-I (0.01 mg/kg body weight) was injected close to the vessels after the completion of internal mammary artery (IMA)/left anterior descending coronary artery (LAD) anastomosis in 20 patients with three-vessel coronary disease. All the patients had additional peripheral stenoses of the LAD or one of its diagonal branches. Twelve weeks later, the IMA bypasses were selectively imaged by intra-arterial digital subtraction angiography and quantitatively evaluated. In all the animal experiments, the development of new vessels in the ischemic myocardium could be demonstrated angiographically. The formation of capillaries could also be demonstrated in humans and was found in all cases around the site of injection. A capillary network sprouting from the proximal part of the coronary artery could be shown to have bypassed the stenoses and rejoined the distal parts of the vessel.

CONCLUSIONS

We believe that the use of FGF-I for myocardial revascularization is in principle a new concept and that it may be particularly suitable for patients with additional peripheral stenoses that cannot be revascularized surgically.