Myoblast transplantation in the porcine model: a potential technique for myocardial repair.

The use of transgenic cells transplanted in syngeneic rodents has shown modest success, but allogeneic and xenogeneic transplants have not been uniformly successful. To assess the feasibility of xenogeneic and allogeneic myoblast transplantation, we subjected seven adult swine to transplantation of murine atrial tumor cells (xenogeneic), neonatal porcine myocytes (allogeneic), and human fetal cardiomyocytes into the left ventricular wall. After general anesthesia, isolated cells were injected along the anterior and posterior walls of the porcine left ventricle. All the animals were immuno-suppressed and observed for 1 month after injection, at which time they were killed and analyzed. This report will present results primarily concerned with the success of human cell transfers. In all injected sites examined, the transplanted cells thrived within the host myocardium with no significant rejection. Transplant cells formed close associations with host myocytes that resembled nascent intercalated disks on electron microscopy. These cells also contained myofibrils and other cell architecture resembling the transplanted cell lines. Additionally, these cells appeared to produce an angiogenic influence resulting in the proliferation of the surrounding microvasculature. We believe that these findings indicate successful xenogeneic and allogeneic myoblast cell transplantation in a large animal model. These experiments set the stage for future studies to assess the ability of these cells to form a syncytium, contract, and potentially repair failed myocardium.

Breast cancer increases initiation of angiogenesis without accelerating neovessel growth rate.

BACKGROUND: Recurrence and mortality rates in patients with breast cancer correlate with the degree of tumor angiogenesis (angiogenic index). We have developed a novel angiogenesis model by using disks of fresh human placental vein that initiate an angiogenic response and exhibit linear radial capillary growth in culture. We hypothesized that the addition of human breast cancer cells to this human placental vein angiogenesis model would increase the incidence of angiogenesis and accelerate the rate of neovessel growth compared with vein disk cultured without tumor cells. METHODS: To test this hypothesis, vein explants from seven human placentas were incorporated into clots of 0.3% fibrin in Medium 199 and fetal bovine serum with or without 1.5 x 10(5) T-47D (n = 6 placentas) or MCF-7 (n = 1 placenta) breast cancer cells. Statistical differences between the experimental (with breast cancer cells) and control (no added cells) cultures were determined by repeated measures ANOVA. RESULTS: The proportion of disks exhibiting neovessel growth (initiation) by day 12 was significantly increased in the presence of T-47D cells (p < 0.05 at day 12, p < 0.001 at day 15). No statistical difference was seen in rates of neovessel growth (millimeters per day). Similar results were seen with MCF-7 cells. CONCLUSIONS: Tumor enhancement of angiogenesis may occur by increased initiation of the angiogenic response. Subsequent vessel growth rates may be tumor independent. We predict that effective antiangiogenic therapies will block a tumor's ability to augment angiogenesis initiation rather than subsequent neovessel growth.

Cardiomyocyte transplantation in a porcine myocardial infarction model.

Transplantation of cardiomyocytes into the heart is a potential treatment for replacing damaged cardiac muscle. To investigate the feasibility and efficiency of this technique, either a cardiac-derived cell line (HL-1 cells), or normal fetal or neonatal pig cardiomyocytes were grafted into a porcine model of myocardial infarction. The myocardial infarction was created by the placement of an embolization coil in the distal portion of the left anterior descending artery in Yorkshire pigs (n = 9). Four to 5 wk after creation of an infarct, the three preparations of cardiomyocytes were grafted, at 1 x 10(6) cells/20 microL into normal and into the middle of the infarcted myocardium. The hearts were harvested and processed for histologic examinations 4 to 5 wk after the cell grafts. Histologic evaluation of the graft sites demonstrated that HL-1 cells and fetal pig cardiomyocytes formed stable grafts within the normal myocardium without any detrimental effect including arrhythmia. In addition, a marked increase in angiogenesis was observed both within the grafts and adjacent host myocardium. Electron microscopy studies demonstrated that fetal pig cardiomyocytes and the host myocardial cells were coupled with adherens-type junctions and gap junctions. Histologic examination of graft sites from infarct tissue failed to show the presence of grafted HL-1 cells, fetal, or neonatal pig cardiomyocytes. Cardiomyocyte transplantation may provide the potential means for cell-mediated gene therapy for introduction of therapeutic molecules into the heart.

Effects of endotoxin on neutrophil-mediated ischemia/reperfusion injury in the rat heart in vivo.

We have previously shown that a nonlethal dose of lipopolysaccharide (LPS) decreases L-selectin expression of neutrophils (PMNs), thereby preventing PMN-mediated reperfusion injury in the isolated heart. In the present study we determined whether or not that dose of LPS would protect hearts during in vivo ischemia and reperfusion by preventing PMN-induced reperfusion injury. Rats receiving saline vehicle showed marked myocardial injury (necrotic area/area at risk = 82%+/-2%) and significant depression in left ventricular function as assessed in the isolated isovolumic heart preparation at constant flow rates of 5, 10, 15, and 20 ml/min. The administration of LPS (100 microg/kg body wt) 7 hr prior to ischemia resulted in a reduction in myocardial damage (necrotic area/area at risk = 42%+/-3%) and preservation of function. Myocardial function was similar to that of sham ischemic saline- and LPS-treated rats. Moreover, PMN infiltration as determined by histology was quantitatively more severe in hearts of saline-treated rats than in hearts of LPS-treated rats. Isolated hearts from vehicle- and LPS-treated animals undergoing sham ischemia in vivo recovered to the same extent after in vitro ischemia/reperfusion, suggesting that LPS did not induce protection by altering intrinsic properties of the heart. Our results indicate that LPS-induced protection of the heart from in vivo PMN-mediated ischemia/reperfusion injury may be due to decreased L-selectin expression of PMNs in LPS-treated animals.

Peripheral corneal ulcer associated with benign hypergammaglobulinemic purpura.

We describe a 56-year-old woman with benign hypergammaglobulinemic purpura in whom scleritis, acute stromal keratitis and peripheral corneal furrowing developed. Initial therapy with topical antibiotics and steroids failed to control the scleritis and keratitis. Subsequent treatment with plasmapheresis led to a decrease in circulating immune complex and serum immunoglobulin levels, with resolution of the ocular inflammation. After 8 years of follow-up the serum IgG and IgM levels were again elevated; however, the corneal disease remained quiescent. Plasmapheresis may have a role in the therapy of this and other immune-complex-mediated ocular diseases.

Sarcoplasmic reticulum and intermediate filament organization in cultured neonatal cardiac muscle cells. Studies with reduced osmium ferrocyanide.

Cardiac muscle cells from 3-day-old rat neonates were cultured for periods of 2 to 56 days. In order to facilitate ultrastructural studies on the organization of the sarcoplasmic reticulum, the cells were prepared for transmission electron microscopy according to a regimen including postfixation in reduced osmium ferrocyanide. The nonjunctional sarcoplasmic reticulum (NJSR) was organized as a loose, fenestrated sleeve around the exterior of bundles of myofilaments and was particularly prominent at the level of the Z line. The only recognizable junctional elements of the sarcoplasmic reticulum were in a peripheral location. Reduced osmium ferrocyanide was also useful in distinguishing intermediate (10 nm) filaments, since it understained Z substance, which often obscured these structures. Intermediate filaments were arranged both at the Z line and the intercalated disc, in parallel strands, approximately at right angles to the myofilaments.

Double membrane-bounded intestinal microvilli in Oncopeltus fasciatus.

A double plasma membrane (DPM) surrounding intestinal microvilli of the migratory milkweed bug, Oncopeltus fasciatus, is described. Mutant and wild types of the phytophagous insect have been studied by conventional SEM and TEM procedures with the use of membrane-enhancing staining methods. Longitudinal and transverse sections revealed a DPM surrounding microvilli and continuing over the apical portions of the intestinal cell. The outer membrane of the DPM contributes to an intestinal lining or peritrophic membrane (PTM), which apparently accumulates in layers. SEM studies reveal a rugose intestinal surface and complete PTM in both starved and fed insects. Only rarely are exposed microvilli seen by SEM. SEM examinations also enable the observation of numerous blebs on the luminal side of the PTM apparently held in position by a neck-like attachment and apparently derived from the outer membrane of the DPM. Preliminary TEM studies of microvilli revealed unique microvesicle-like structures, lying just inside the inner membrane of the DPM, which may be of membrane origin based on their typical trilaminar appearance after en bloc staining with uranyl acetate. Highly ordered microfilaments were observed to occupy the most central aspect of the microvilli.

Ultrastructural morphometric analysis of cultured neonatal and adult rat ventricular cardiac muscle cells.

Neonatal and adult rat ventricular cardiac muscle cells cultured on laminin differed from similar myocytes grown on plastic in the amount and distribution of their mitochondria and transverse tubules. Point-count morphometry was used at the electron microscopic level to quantify these differences. Adult myocytes grown on laminin contained more mitochondria per unit volume than adult myocytes grown on plastic. No significant differences were observed in the volume percent of myofibrils in either adult or neonatal ventricular myocytes when grown on laminin and compared to those grown on plastic. The transverse tubule system in neonatal and adult myocytes was reduced significantly when both groups were cultured on laminin. Furthermore, neonatal and adult myocytes cultured on laminin were flatter than those cultured on plastic. This may indicate a relationship between the surface/volume ratio and transverse tubule development in cultured myocytes. These studies establish that point-count morphometry can be used to quantify changes in the organelle volume densities of cultured cardiac muscle cells.

Light, scanning, and transmission electron microscopy of a single population of detergent-extracted cardiac myocytes in vitro.

A technique for performing light, scanning, and transverse transmission electron microscopy on cultured cells grown within a single tissue culture flask is described. Permanent light microscopy slides are obtained by removing selected portions of the plastic tissue culture vessel and mounting them on glass slides with an aqueous mounting solution. The images obtained from these slides are superior to viewing through the bottom of the flask with an inverted stage microscope. For scanning electron microscopy, selected areas are also cut from the remainder of the vessel and prepared for viewing. The final portion of the culture container is transferred and attached to a new tissue culture vessel and prepared for transmission electron microscopy using alcohol instead of acetone and propylene oxide during dehydration, infiltration, and embedding.

Culture and characterization of fetal human atrial and ventricular cardiac muscle cells.

Atrial and ventricular cardiac muscle cells isolated from 14- to 18-wk old fetal human hearts were grown in culture and characterized. Once established in culture the flattened cells contracted spontaneously and possessed differentiated ultrastructural characteristics including organized sarcomeres, intercalated discs, and transverse tubules with couplings. Atrial granules were present in the cultured atrial cells. Some cultured ventricular myocytes also contained electron-dense granules associated with Golgi cisternae, which were similar in size and appearance to atrial granules. The cultured ventricular myocytes divided and expressed the genes for thymidine kinase, histone H4, myosin heavy chain, muscle-specific creatine kinase, atrial natriuretic factor, and insulin-like growth factor II. These results establish that differentiated fetal human heart muscle cells can be cultured in sufficient quantities for biochemical, molecular, and morphological analyses.

Morphological characterization of cardiomyocytes isolated from a transplantable cardiac tumor derived from transgenic mouse atria (AT-1 cells).

We have developed a transplantable tumor lineage derived from transgenic mouse atrial cardiomyocytes that express the SV40 large T oncogene and have named these cardiomyocytes AT-1 cells. In this study, the transplantable tumors, freshly isolated tumor cardiomyocytes, and cultured tumor cardiomyocytes were examined using phase-contrast microscopy, autoradiography, and electron microscopy. The vast majority of the subcutaneous tumor cells, greater than 90% of the cellular mass of the tumor, exhibited sarcomeric banding. Ultrastructural characteristics typical of in vivo atrial cardiac muscle cells, including well-organized myofibrils, gap junctions, and atrial-specific cytoplasmic granules, were observed in in situ and in freshly isolated AT-1 cells. Those cells that did not contain some form of organized myofibrils were primarily vascular elements, such as endothelial cells. Labeling with [3H]thymidine indicated that greater than 90% of cultured AT-1 cells were synthesizing DNA; furthermore, many cells could be seen undergoing cell division. Electron microscopy revealed that the cultured AT-1 cardiomyocytes contained all of the above-described characteristics, including a well-developed transverse tubular system.

Effects of endotoxin on neutrophil-mediated I/R injury in isolated perfused rat hearts.

With the use of a syngeneic model, we demonstrate that rat polymorphonuclear neutrophils (PMNs) exacerbate ischemia-reperfusion injury in the isolated rat heart. However, PMNs (19 x 10(6) cells) from lipopolysaccharide (LPS)-treated rats (LPS-PMNs; 100 mg/kg administered 7 h before exsanguination) induce less reperfusion injury in the isolated heart. Average recovery of left ventricular developed pressure after 20 min of ischemia and 60 min of reperfusion was 51 +/- 4% in hearts receiving PMNs from saline-treated control rats (saline-PMNs) versus 78 +/- 2% in hearts receiving LPS-PMNs. Ischemic hearts reperfused with LPS-PMNs recovered to the same extent as did hearts reperfused with Krebs buffer only. LPS-PMNs and saline-PMNs showed no difference in basal or phorbol ester-induced superoxide production. Whereas twice the number of LPS-PMNs was positive for nitroblue tetrazolium, the percent positive for L-selectin, a receptor integral in PMN-adhesion to endothelium, was 50% less in LPS-PMNs than in controls. After reperfusion, three-fourths of the saline-PMNs remained within the hearts, whereas only one-fourth of LPS-PMNs were trapped. These data suggest that PMNs from LPS-treated rats do not exacerbate ischemia-reperfusion injury as do control PMNs, possibly, due to impaired PMN adhesion to endothelium as a result of decreased L-selectin receptors.

Ultrastructure of cultured hepatocytes from fat- and cholesterol-fed rats.

Hepatocytes were enzymatically dissociated from the livers of rats maintained for eight weeks on diets of (1) standard rat chow, (2) chow plus 20% olive oil, and (3) chow plus 20% olive oil and 2% cholesterol. Cells were cultured for up to one week and characterized by phase contrast light microscopy and transmission electron microscopy. Cultured hepatocytes derived from the cholesterol-fed rats (3) were distinguishable by phase contrast light microscopy from those derived from chow-or chow plus olive oil-fed (1 and 2) cells, since they contained numerous refractile cytoplasmic structures. Transmission electron microscopy demonstrated that these structures were lipid droplets. Hepatocytes were observed to accumulate non-membrane bound cytoplasmic lipid droplets in the order control-fed less than olive oil-fed less than cholesterol-fed. In addition to varying quantitatively among the feeding groups, lipid droplets also varied in size and osmiophilia as a function of the feeding regimen. Other than the differential accumulation of lipid droplets, the ultrastructure of the cultured hepatocytes was similar among cells derived from the various feeding groups.

Molecular pathophysiology of cystic fibrosis based on the rescued knockout mouse model.

Cystic fibrosis transmembrane conductance regulator (cftr) gene mutations are thought to result in cystic fibrosis due to an absence of the protein's chloride channel. Recently, the lethal intestinal blockage in the cftr knockout mouse was reversed by a single in utero dose of a recombinant adenovirus containing the human cftr gene. The rescue of these animals did not require continuous expression of the gene and the cAMP-dependent chloride channel was not permanently restored. These data suggested that cftr was required for normal development of the intestine but not for normal function of the adult organ. Phenotypic changes in the intestines and lungs of in utero cftr-treated knockout and heterozygous mice revealed that altered development was induced. The intestines of the untreated knockout mice were shown to be deficient in both intracellular calcium and UTP receptors. Both of these deficiencies were partially corrected in the rescued knockout mice, whereas treatment of heterozygous animals disrupted the normal pattern of these markers. Examination of the lungs of knockout cftr (-/-) mice with lectins showed an increase in secreted glycoconjugates containing alpha(2,6)-sialic acid and fucose as compared with control heterozygotes. The in utero-treated knockouts showed an increase in this material as well, but it was contained in intracellular vesicles. Electron microscopy of these tissues confirmed the developmental alteration of secretory cell differentiation in the lungs. These data show that cftr is required in both the lung and intestines for normal differentiation of a secretory cell population and that in its absence these cells fail to develop properly.

CFTR modulates lung secretory cell proliferation and differentiation.

We have permanently reversed the lethal phenotype in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR)-deficient (knockout) mouse after in utero gene therapy with an adenovirus containing the cftr gene. The gene transfer targeted somatic stem cells in the developing lung and intestine, and these epithelial surfaces demonstrated permanent developmental changes after treatment. The survival statistics from the progeny of heterozygote-heterozygote matings after in utero cftr gene treatment demonstrated an increased mortality in the homozygous normal pups, indicating that overexpression during development was detrimental. The lungs of these pups revealed accelerated secretory cell proliferation and differentiation. The extent of proliferation and differentiation in the secretory cells of the lung parenchyma after in utero transfer of the cftr gene was evaluated with morphometric and biochemical analyses. These studies provide further support of the regulatory role of the cftr gene in the development of the secretory epithelium.

Cardiomyocyte proliferation in mice expressing alpha-cardiac myosin heavy chain-SV40 T-antigen transgenes.

To determine the proliferative potential of adult ventricular cardiomyocytes, we have generated transgenic mice that express the SV40 large T-antigen oncogene in the heart. A fusion gene comprised of the rat alpha-cardiac myosin heavy chain promoter and the SV40 early region was used to target oncogene expression to the myocardium. Expression of SV40 large T-antigen was observed in both atrial and ventricular cardiomyocytes in adult transgenic animals. T-antigen expression was associated with hyperplasia in the targeted cells. Immunohistological analysis indicated that the proliferating cells continued to express sarcomeric myosin. Electron microscopic examination demonstrated that cardiomyocytes in various stages of the cell cycle retained ultrastructural characteristics typical of mitotic cardiac muscle cells in vivo. Cardiomyocytes isolated from transgenic tumors were able to proliferate in culture and retained a differentiated phenotype, as evidenced by spontaneous contractile activity. Preliminary studies indicate that these cells can undergo a limited number of passages while retaining this differentiated phenotype. These studies demonstrate that both ventricular and atrial cardiomyocytes from transgenic mice proliferate in response to targeted T-antigen expression.

Gene transfer into the fetal primate: evidence for the secretion of transgene product.

In utero adenoviral-mediated transfer of genes via the amniotic fluid results in sustained high-efficiency expression in rodent lung and intestine. Rhesus macaque (Macaca mulatta) fetuses were injected with adenovirus vectors encoding reporter genes at different gestational ages to evaluate feasibility and timing in primates. The fetuses developed normally following gene transfer and no maternal adverse affects were noted. Highly efficient viral uptake and transgene protein expression occurred in the target organs. The lungs exhibited no immune response and transgenic protein was observed up to 30 days postinfection. Unexpectedly, large amounts of reporter gene protein were released, apparently from the lung, into the circulation and accumulated in the renal proximal tubules and bladder. PCR detection for adenovirus DNA was consistently negative in tissues not in contact with the amniotic fluid, such as kidneys, liver, gonads, and eyes. Treatment of primate fetuses at 110 days gestation with an adenovirus expressing the cystic fibrosis transmembrane conductance regulator (cftr) gene resulted in accelerated differentiation of the lung. These studies demonstrate the efficacy of in utero gene therapy in primates and its potential application to genetic diseases.

Proliferation in vivo and in culture of differentiated adult atrial cardiomyocytes from transgenic mice.

Transgenic mice expressing atrial natriuretic factor-SV40 T-antigen fusion genes (ANF-TAG) developed unilateral right atrial tumors composed of differentiated dividing cardiomyocytes. The atrial tumors could be propagated as transplantable tumor lineages in syngeneic animals. Cardiomyocytes derived from ANF-TAG atrial tumors did not proliferate in tissue culture. However, cardiomyocytes derived from the transplantable tumor lines proliferated in culture, and these proliferating cardiomyocytes could be passaged in culture and recovered from frozen stocks. Cardiomyocytes from either tumor source were highly differentiated as determined by diverse functional and structural criteria. The cells continued to express numerous cardiac-specific proteins and retained ultrastructural features characteristic of cardiomyocytes including well-formed myofibrils, transverse tubules, and intercalated disks. In addition, the cultured cells displayed spontaneous electrical and contractile activities. These atrial tumor cardiomyocytes are a novel experimental resource for the identification of genes regulating the cardiomyocyte cell cycle.

Effect of basic fibroblast growth factor on angiogenesis in the infarcted porcine heart.

Administration of growth factors is emerging as a new therapeutic approach for the enhancement of collateral vessel formation in the ischemic heart. We have investigated the effects of intramyocardial delivery of FGF-2 in the presence and absence of heparin on angiogenesis in a porcine model of myocardial infarction. Yorkshire pigs were subjected to myocardial infarction by the placement of an embolization coil in the left anterior descending artery (n = 5). Four to five weeks after creation of an infarct, FGF-2 (10 micrograms) alone or in complex with heparin, heparan sulfate, or heparin agarose beads was injected either into the normal myocardium or along the infarct border area. Histologic evaluation of each injection site was performed 4 to 5 weeks post-injection. The effect of FGF-2 on angiogenesis was evaluated by determining the number of capillaries (diameter < 20 microns (and arterioles (> 20 microns with tunica media) in each area observed. The number of capillaries were not affected by the treatment of FGF-2 both in normal myocardium and infarct border area. However, in the normal myocardium, the number of arterioles were increased with the treatment of FGF-2 alone (85 +/- 59%, P < 0.04), FGF-2 plus heparin (281 +/- 193%, P < 0.004) and FGF-2-coated heparin beads (241 +/- 141%, P < 0.01), as compared to control. Delivery of FGF-2 into the infarct border area, also increased the number of arterioles when FGF-2 was given with heparin (736 +/- 154%, P < 0.001) or heparin beads (700 +/- 109%, P < 0.001), as compared to control. FGF-2 administered with heparin was the most effective method of enhancing angiogenesis as compared to FGF-2 alone, FGF-2 plus heparan sulfate, or FGF-2 coated heparin agarose beads.