Safety and efficacy of transvenous lead extraction in octogenarians using powered extraction sheaths.

BACKGROUND: In the aging population equipped with cardiac implantable electronic devices, an increasing number of octogenarians require lead extractions. This patient population is often considered as a high-risk group for surgical procedures. We, therefore, investigated the safety and efficacy of transvenous lead extraction in octogenarians using powered extraction sheaths. METHODS: Between January 2013 and March 2017, 403 patients underwent lead extraction at two high-volume lead extraction centers. A total of 71 octogenarians were treated with laser lead extraction and were included in this analysis. Primary extraction method was laser lead extraction, with additional use of mechanical rotational sheaths or femoral snares, if necessary. Patient-based and procedural data were collected and analyzed retrospectively. RESULTS: Mean age was 83.5 ± 3.3 years, 64.7% were males. A total of 152 leads were extracted. The mean lead dwell time of treated leads was 10.2 ± 5.2 years. Complete procedural success rate was 92.9%, while clinical success was achieved in 98.6%. Failure of extraction occurred in one patient (1.4%). In six (7.7%) patients, additional mechanical rotational sheaths or femoral snares were used. Overall complication rate was 4.2%, including one (1.4%) major (RA perforation) and two (2.8%) minor complications. No procedure-related mortality was observed in any of the patients. CONCLUSION: Transvenous lead extraction in octogenarians with old leads is safe and effective when performed in experienced centers. Patient's age should therefore not be considered as contraindication for lead extraction using powered extraction sheaths.

Transvenous Endomyocardial Biopsy: A Comparison of 2 Approaches.

BACKGROUND: Endomyocardial biopsy (EMB) is a well-established procedure for the diagnosis of specific myocardial diseases and represents the gold standard in monitoring allografts after heart transplantation. In our study, we compared 2 different approaches for harvesting EMB in order to optimize patient safety and efficacy of the procedure. METHODS: As a standard approach for harvesting EMB, a venous introducer sheath was inserted percutaneously via the internal jugular vein using the Seldinger technique. Thereafter, a bioptome was repeatedly introduced throughout this sheath into the right ventricle (RV), each time passing the tricuspid valve (TV). Alternatively, a coronary sinus catheter was inserted via an introducer sheath placed in the subclavian vein and only once was introduced into RV cavity. Hence, just a unique passage of TV was required. Thereafter, a bioptome was introduced via this catheter and precisely guided to the targeted biopsy site. RESULTS: A standard approach was used with 34 patients, and a modified technique was used with 37 patients. Patient characteristics were comparable in both cohorts, and analyses of peri-procedural parameters identified only marginal differences between the groups. Interestingly, the number of harvested tissue samples per procedure was higher in the modified approach compared to the standard approach. No complications occurred. CONCLUSION: The modified approach for EMB is a safe procedure. The facilitated bioptome-guidance and enhanced protection of TV may prevent periprocedural complications.

Safety and efficacy of transvenous lead extraction of very old leads.

OBJECTIVES: Transvenous lead extraction using mechanical rotational- or laser sheaths is an established procedure. Lead dwell time has been recognized as a risk factor for extraction failure and procedure-related complications. We therefore investigated the safety and efficacy of transvenous extraction of leads with an implant duration of more than 10 years. METHODS: Between January 2013 and March 2017, a total of 403 patients underwent lead extraction in 2 high-volume lead extraction centres. One hundred and fifty-four patients with extraction of at least 1 lead aged over 10 years were included in this analysis. Laser lead extraction was the primary extraction method, with additional use of mechanical rotational sheaths or femoral snares, if necessary. All procedural- and patient-based data were collected into a database and retrospectively analysed. RESULTS: Mean patient's age was 65.8 ± 15.8 years, 68.2% were male. Three hundred and sixty-two leads had to be extracted. The mean lead dwell time of treated leads was 14.0 ± 6.1 years. Complete procedural success was achieved in 91.6% of cases, while clinical success was achieved in 96.8%. Failure of extraction occurred in 3.2%. Leads that could not be completely removed had a significantly longer lead dwell time (18.2 vs 13.2 years; P = 0.016). Additional mechanical rotational sheaths or femoral snares were used in 26 (16.9%) patients. Overall complication rate was 4.6%, including 5 (3.3%) major and 2 (1.3%) minor complications. There was no procedure-related mortality. CONCLUSIONS: Transvenous lead extraction in leads aged over 10 years is safe and effective when performed in specialized centres and with use of multiple tools and techniques. Leads that could not be completely extracted had a statistically significant longer lead dwell time.

Probability of sinus rhythm conversion and maintenance in cardiac resynchronization therapy patients with atrial fibrillation during 5-year follow-up.

INTRODUCTION: There is a high prevalence of atrial fibrillation (AF) in patients with heart failure presented for cardiac resynchronization therapy (CRT). It remains unclear whether an atrial lead should be implanted in these patients. We, therefore, analyzed outcomes and course of rhythm in AF patients undergoing CRT implantation during long-term follow-up. METHODS AND RESULTS: Between 2004 and 2018, 328 consecutive patients with a history of AF receiving CRT implantation were included in this study. 132 patients had preoperatively paroxysmal AF (px-AF), while 70 and 126 patients had persistent AF (ps-AF) and long-standing persistent AF (lp-AF), respectively. The outcome data were collected in our institutional database and analyzed retrospectively. Two hundred and seventy-seven patients received an atrial lead at the time of implantation, nine during follow-up. No major lead implantation-associated complications were observed. In patients with px-AF, sinus rhythm (SR) was present in 78.8% at admission, 95.5% (p < .001) at discharge, and 85.7% (p = .965) after 5 years. In ps-AF patients SR was present in 28.6%, 91.4% (p < .001) and 69.7% (p < .001), while all lp-AF patients showed AF at admission and had SR rate of 50.8% (p < .001) at discharge and 44.1% after 5 years (p < .001). CONCLUSION: We observed a high rate of conversion and long-term persistence of SR in AF patients undergoing CRT implantation. Due to the low rate of lead implantation-associated complications and the high successful SR conversion rates, we recommend the implantation of an atrial lead in CRT patients with AF.

Five-year follow-up of transvenous and epicardial left ventricular leads: experience with more than 1000 leads.

OBJECTIVES: Transvenous coronary sinus leads are considered to be the gold standard for cardiac resynchronization therapy (CRT). However, in patients with abnormal coronary vein anatomy, the epicardial leads can be an alternative. Data comparing durability and performance of these 2 lead types are limited. In order to provide clarity, we investigated patients receiving CRT system in our centre. METHODS: One thousand and fifty-three consecutive patients scheduled for CRT implantation were retrospectively analysed. From these, 895 received transvenous coronary sinus and 158 epicardial left ventricular (LV) leads. Lead-specific as well as LV functional parameters have been evaluated in 60 months' follow-up. RESULTS: Technical characteristics (pacing threshold, impedance and sensing) of both lead types remained stable during the whole observation period. Whereas an early revision (<6 month) was noted in 5.4% of transvenous leads, no reintervention has been necessary for epicardial leads. During the 5-year observation period, a lead revisions rate of 10.2% for transvenous leads and 1.9% for epicardial leads were detected. Regarding CRT efficacy, excellent results were achieved for both electrode types. In both groups, a statistically significant reduction of New York Heart Association class (2.85-2.13 and 2.96-2.09), increase in left ventricular ejection fraction (24.6-32.6% and 27.2-34.6%), reduction of left ventricular end-systolic diameter/left ventricular end-diastolic diameter and reduction in degree of mitral valve insufficiency could be observed over the time. CONCLUSIONS: Our data demonstrate safety and functional efficacy of both transvenous and epicardial leads. Moreover, in long-term follow-up, a commendable durability and performance were found for both lead types. Thus, epicardial leads represent a good alternative when transvenous implantation fails.

Intraoperative Defibrillation Testing Should Not Be Generally Abandoned for All ICD Procedures-A Multicenter Study on 4,572 Consecutive Patients.

Background The ongoing technical advances in development of new implantable cardioverter defibrillator (ICD) systems led some investigators to question the routine use of intraoperative defibrillation testing (DT). Therefore, we evaluated retrospectively in a multicenter study effectiveness, safety, and usefulness of intraoperative DT on unbiased large patient population. Methods Data from 4,572 consecutive patients undergoing any ICD intervention were retrospectively analyzed. Besides efficacy of DT, risk factors for DT failure were identified in a multiple logistic regression analysis. Results Overall 5,483 shock data from 4,532 patients were available. Not tested for medical reasons were 13.5%. DT-associated complications were not noted. Primary DT effectiveness was 95.8%, whereas 4.2% were ineffective. Optimization (51.6% increase of DT energy, 10.1% subcutaneous lead array (SQ array), 2% generator exchange, 4.8% lead reposition, 9.3% lead exchange, and 22.2% change of shock parameters) led to successful DT in 152 patients (96.2%). Subanalyses and logistic regression identified implantation of generator in any other position than left subpectoral, age, body mass index and left ventricular ejection fraction as independent predictors for primary DT failure. Conclusion The number of patients, including those undergoing generator exchange, system upgrade, or system revision, with inappropriate intraoperative testshock is relatively high. The results of recent prospective clinical trials can be extrapolated only on first ICD implantations with high-energy generators. For patients undergoing subcutaneous ICD implantation, right-sided implantation, patients with channelopathies and hypertrophic cardiomyopathy, as well as for procedures on already implanted ICD systems, the intraoperative DT might still be recommended.

Role of early growth response 1 in arteriogenesis: impact on vascular cell proliferation and leukocyte recruitment in vivo.

Based on previous findings that early growth response 1 (Egr-1) participates in leukocyte recruitment and cell proliferation in vitro, this study was designed to investigate its mode of action during arteriogenesis in vivo. In a model of peripheral arteriogenesis, Egr-1 was significantly upregulated in growing collaterals of wild-type (WT) mice, both on mRNA and protein level. Egr-1(-/-) mice demonstrated delayed arteriogenesis after femoral artery ligation. They further showed increased levels of monocytes and granulocytes in the circulation, but reduced levels in adductor muscles under baseline conditions. After femoral artery ligation, elevated numbers of macrophages were detected in the perivascular zone of collaterals in Egr-1(-/-) mice and mRNA of leukocyte recruitment mediators was upregulated. Other Egr family members (Egr-2 to -4) were significantly upregulated only in Egr-1(-/-) mice, suggesting a mechanism of counterbalancing Egr-1 deficiency. Moreover, splicing factor-1, downregulated in WT mice after femoral artery ligation in the process of increased vascular cell proliferation, was upregulated in Egr-1(-/-) mice. αSM-actin on the other hand, significantly downregulated in WT mice, showed no differential expression in Egr-1(-/-) mice. While cell cycle regulator cyclin E and cdc20 were upregulated in Egr-1(-/-) mice, cyclin D1 expression decreased below the detection limit in collaterals, and the proliferation marker ki67 was not differentially expressed. In conclusion, compensation for deficiency in Egr-1 function in leukocyte recruitment can presumably be mediated by other transcription factors; however, Egr-1 is indispensable for effective vascular cell cycle progression in arteriogenesis.

New generation of transvenous left ventricular leads - first experience with implantation of multipolar left ventricular leads.

BACKGROUND: Aside from unfavourable anatomy, inacceptable pacing thresholds and phrenic nerve stimulation represent major obstacles for successful left ventricular (LV) lead placement for cardiac resynchronization therapy (CRT). OBJECTIVE: To implant, for the first time, a new generation of transvenous multipolar LV leads (a quad-electrode lead) in combination with a CRT-cardioverter defibrillator, and to demonstrate that this combination allows for 10 different pacing vectors to combat the problems cited above. METHODS: Thirty patients were selected for CRT-cardioverter defibrillator implantation. At implantation, standard lead parameters were recorded. The reason for choosing a vector other than the standard bipolar vector for LV pacing, the LV lead implantation time, x-ray exposure time required for lead placement, and the reason for and number of repositions were documented. Before hospital discharge, a system inspection was performed. RESULTS: The implantation lead parameters were satisfactory. In 17 patients, a vector other than the standard bipolar vector was chosen to avoid phrenic nerve stimulation or to establish a better pacing threshold. In seven cases, the LV lead was repositioned (three phrenic nerve stimulations, two inacceptable pacing captures and two nonstable lead positions). Phrenic nerve stimulation was noted in eight cases; however, in five, this was eliminated by changing the stimulation vector. At hospital discharge, two-thirds of patients retained the implantation stimulation vector and in one-third, the vector was modified to further optimize the system. CONCLUSIONS: The quad-electrode lead provides good handling and may reduce the risk of inacceptable pacing thresholds and phrenic nerve stimulation. Consequently, implantation time, x-ray exposure and contrast agent load may be decreased, leading to lower kidney stress. Furthermore, the option for vector change after implantation may reduce the number of necessary reinterventions resulting from the pacing threshold and impedance increase.

Calcium signaling-mediated endogenous protection of cell energetics in the acutely diabetic myocardium.

In acute diabetic myocardium, calcium signals propagated by intracellular calcium transients participate in the protection of cell energetics via upregulating the formation of mitochondrial energy transition pores (ETP). Mechanisms coupling ETP formation with an increase in membrane fluidity and a decrease in transmembrane potential of the mitochondria are discussed. Our results indicate that the amplification of calcium transients in the diabetic heart is associated with an increase in their amplitude. Moreover, the signals transferred by calcium transients also regulated ETP formation in nondiabetic myocardium. Evidence for the indispensable role of calcium in the regulation of transition pore formation is provided whereby an exchange of cadmium for calcium ions led to a rapid and dramatic decrease in the amount of ETP. Another possible regulatory factor of the mitochondrial function may be radical-induced damage to the diabetic heart. Nevertheless, our data indicate that radical-induced changes in mitochondria predominantly concern the respiratory chain and have no appreciable effect on the fluidity of the mitochondrial membranes. The residual mitochondrial production of ATP owing to its augmented transfer to the cytosol proved to be adequate to preserve sufficient levels of adenine nucleotides in the acute diabetic myocardium.

Notch ligand Delta-like 1 is essential for postnatal arteriogenesis.

Growth of functional arteries is essential for the restoration of blood flow to ischemic organs. Notch signaling regulates arterial differentiation upstream of ephrin-B2 during embryonic development, but its role during postnatal arteriogenesis is unknown. Here, we identify the Notch ligand Delta-like 1 (Dll1) as an essential regulator of postnatal arteriogenesis. Dll1 expression was specifically detected in arterial endothelial cells, but not in venous endothelial cells or capillaries. During ischemia-induced arteriogenesis endothelial Dll1 expression was strongly induced, Notch signaling activated and ephrin-B2 upregulated, whereas perivascular cells expressed proangiogenic vascular endothelial growth factor, and the ephrin-B2 activator EphB4. In heterozygous Dll1 mutant mice endothelial Notch activation and ephrin-B2 induction after hindlimb ischemia were absent, arterial collateral growth was abrogated and recovery of blood flow was severely impaired, but perivascular vascular endothelial growth factor and EphB4 expression was unaltered. In vitro, angiogenic growth factors synergistically activated Notch signaling by induction of Dll1, which was necessary and sufficient to regulate ephrin-B2 expression and to induce ephrin-B2 and EphB4-dependent branching morphogenesis in human arterial EC. Thus, Dll1-mediated Notch activation regulates ephrin-B2 expression and postnatal arteriogenesis.

Impact of mouse strain differences in innate hindlimb collateral vasculature.

OBJECTIVE: To assess the importance of genetic background for collateral artery development. METHODS AND RESULTS: C57BL/6, BALB/c and 129S2/Sv mice were studied after femoral artery ligation by laser Doppler imaging, visible light oximetry, time-of-flight-magnetic resonance imaging, and treadmill testing; C57BL/6 and BALB/c also underwent electron paramagnetic resonance (EPR) oximetry, x-ray angiography, and histology. C57BL/6 had the least initial distal ischemia and most complete recovery. BALB/c had the most severe initial ischemia and poorest recovery. BALB/c had some vasodilatory reserve in their ligated limbs not seen in the other strains at 3 weeks. By in vivo TOF-magnetic resonance angiography, C57BL/6 had larger preexistent and developed collaterals. By x-ray angiography, C57BL/6 had a higher collateral-dependent filling score and number of visible collaterals immediately after femoral ligation and a higher number of visible collaterals at 1 week but not at 4 weeks. EPR oximetry and histology revealed hypoxia and tissue damage in regions of collateral growth of BALB/c but not C57BL/6 mice. In C57BL/6 BrdUrd uptake in the thigh was limited to larger vessels and isolated perivascular cells. Proliferative activity in collateral arterioles was similar in both strains. CONCLUSIONS: Genetic differences in preexistent collateral vasculature can profoundly affect outcome and milieu for compensatory collateral artery growth after femoral artery occlusion.

Matrix metalloproteinases and their tissue inhibitors in pressure-overloaded human myocardium during heart failure progression.

OBJECTIVES: We studied the role of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in fibrosis formation in the transition from hypertrophy to heart failure (HF) as well as the cellular source of MMPs and TIMPs. BACKGROUND: Human pressure-overloaded hearts are characterized by a significant increase in cardiac fibrosis. However, the contribution of the proteolytic/antiproteolytic system in aortic stenosis (AS) during hypertrophy progression has not yet been elucidated. METHODS: Three groups of AS patients (I: EF >50%, n = 12; II: EF 50% to 30%, n = 10; III: EF <30%, n = 12) undergoing aortic valve replacement and seven controls were studied. Tissue samples were investigated by immunoconfocal microscopy, Western blotting, and zymography. RESULTS: Quantitative analysis by immunoconfocal microscopy and Western blotting showed an upregulation of MMP-1, -2, -3, -9, -13, and -14 in group I and further increases in later stages. Tissue inhibitors of metalloproteinase-1 and -2 were enhanced and TIMP-4 was decreased in comparison to control. Gelatinolytic activity of MMP-2 significantly (p < 0.05) increased 1.2-fold (group I), 1.5-fold (group II), and 1.6-fold (group III) over control. The level of collagen I was significantly upregulated in all AS groups. Immunoconfocal microscopy showed that MMPs and TIMPs are produced predominantly by fibroblasts. The number of proliferating fibroblasts was significantly elevated during the transition to HF (0.67 n/mm(2)-control, 5.03-group III, p < 0.05). CONCLUSIONS: In human hearts a continuous turnover of the extracellular matrix occurs during the progression from compensated hypertrophy to HF that is characterized by the upregulation of MMPs and inadequate inhibition by TIMPs. The altered balance between proteolysis/antiproteolysis with accompanying proliferation of fibroblasts results in fibrosis progression.

Improved arteriogenesis with simultaneous skeletal muscle repair in ischemic tissue by SCL(+) multipotent adult progenitor cell clones from peripheral blood.

BACKGROUND: The CD34(-) murine stem cell line RM26 cloned from peripheral blood mononuclear cells has been shown to generate hematopoietic progeny in lethally irradiated animals. The peripheral blood-derived cell clones expresses a variety of mesodermal and erythroid/myeloid transcription factors suggesting a multipotent differentiation potential like the bone marrow-derived 'multipotent adult progenitor cells' (MAP-C). METHODS: SCL(+) CD34(-) RM26 cells were transfused intravenously into mice suffering from chronic hind-limb ischemia, evaluating the effect of stem cells on collateral artery growth and simultaneous skeletal muscle repair. RESULTS: RM26 cells are capable of differentiating in vitro into endothelial cells when cultured on the appropriate collagen matrix. Activation of the SCL stem cell enhancer (SCL(+)) is mediated through the binding to two Ets and one GATA site and cells start to express milieu- and growth condition-dependent levels of the endothelial markers CD31 (PECAM) and Flt-1 (VEGF-R1). Intravenously infused RM26 cells significantly improved the collateral blood flow (arteriogenesis) and neo-angiogenesis formation in a murine hind-limb ischemia transplant model. Although transplanted RM26 cells did not integrate into the growing collateral arteries, cells were found adjacent to local arteriogenesis, but instead integrated into the ischemic skeletal muscle exclusively in the affected limb for simultaneous tissue repair. CONCLUSION: These data suggest that molecularly primed hem-/mesangioblast-type adult progenitor cells can circulate in the peripheral blood improving perfusion of tissues with chronic ischemia and extending beyond the vascular compartment.

Magnetic resonance angiography of collateral vessels in a murine femoral artery ligation model.

The in vivo detection of growing collateral vessels following arterial occlusion is difficult in small animals. We have addressed the feasibility of performing high resolution time-of-flight angiograms to monitor the growth of collateral vessels after femoral artery occlusion in mice. We will also present a low-pass quadrature birdcage coil construction with a sufficient signal-to-noise ratio to produce high resolution. After a 4-month recovery period a C57BL/6 mouse with a surgical occlusion of the right femoral artery was used to assess the image quality and time requirements to produce magnetic resonance angiograms sufficient to assess collateral artery development using a two-dimensional gradient echo sequence. At a resolution of 100 x 100 x 100 microm and a matrix size of 256 x 128 x 256 for a 2.56 cm isometric volume, three scans were performed with one, two and four repetitions resulting in signal-to-noise ratios for the femoral artery proximal to the ligation site of 58, 126 and 194, respectively. Five C57BL/6 mice were additionally measured 4 weeks after occlusion using two repetitions and the visual collateral vessels were assessed for number and location: 2.0 +/- 1.2 in quadriceps muscle, 0.6 +/- 0.5 in adductor (deep adductor vessel), 0.0 +/- 0.0 in adductor (surface adductor vessels). The results showed a significant difference, two-sided t-test, p < 0.05, in number of vessels in all the locations. We have shown that this method can be utilized to elucidate the contribution of collateral vessels to arterial flow.

Collateral artery growth (arteriogenesis) after experimental arterial occlusion is impaired in mice lacking CC-chemokine receptor-2.

Arteriogenesis has been associated with the presence of monocytes/macrophages within the collateral vessel wall. Induced macrophage migration in vivo is driven by the binding of monocyte chemoattractant protein-1 (MCP-1, or CCL2 in the new nomenclature) to the CCR2-chemokine receptor on macrophages. To determine whether the CCL2-CCR2 signaling pathway is involved in the accumulation of macrophages in growing collateral vessels, we used mice that are deficient in CCR2 in a model of experimental arterial occlusion and collateral vessel growth. In an in vitro CCL2-driven chemotaxis assay, mononuclear cells isolated from wild-type BALB/c mice exhibited CCL2 concentration-dependent migration, whereas this migration was abolished in cells from CCR2(-/-) mice on a BALB/c genetic background. In vivo, blood flow recovery as measured by laser Doppler (LDI) and MRI (MRI) was impaired in CCR2(-/-) mice on either the BALB/c or C57BL/6 genetic backgrounds. Three weeks after femoral artery ligation, LDI perfusion ratio of operated versus nonoperated distal hindlimb in BALB/c wild-type mice increased to 0.45+/-0.06 and in CCR2(-/-) animals only to 0.21+/-0.03 (P<0.01). In C57BL/6 mice, ratio increased to 0.96+/-0.09 and 0.85+/-0.08 (P<0.05), respectively. MRI at 3 weeks (0.76+/-0.06 versus 0.62+/-0.01; P<0.05) and hemoglobin oxygen saturation measurements confirmed these findings. Active foot movement score significantly decreased and gastrocnemius muscle atrophy was significantly greater in CCR2(-/-) mice. Morphometric analysis showed a lesser increase in collateral vessel diameters in CCR2(-/-) mice. Importantly, the number of invaded monocytes/macrophages in the perivascular space of collateral arteries of CCR2(-/-) animals was dramatically reduced in comparison to wild-type mice. In conclusion, our results demonstrate that the CCR2 signaling pathway is essential for efficient collateral artery growth.

Bone marrow-derived cells do not incorporate into the adult growing vasculature.

Bone marrow-Derived cells have been proposed to form new vessels or at least incorporate into growing vessels in adult organisms under certain physiological and pathological conditions. We investigated whether bone marrow-Derived cells incorporate into vessels using mouse models of hindlimb ischemia (arteriogenesis and angiogenesis) and tumor growth. C57BL/6 wild-type mice were lethally irradiated and transplanted with bone marrow cells from littermates expressing enhanced green fluorescent protein (GFP). At least 6 weeks after bone marrow transplantation, the animals underwent unilateral femoral artery occlusions with or without pretreatment with vascular endothelial growth factor or were subcutaneously implanted with methylcholanthrene-induced fibrosarcoma (BFS-1) cells. Seven and 21 days after surgery, proximal hindlimb muscles with growing collateral arteries and ischemic gastrocnemius muscles as well as grown tumors and various organs were excised for histological analysis. We failed to colocalize GFP signals with endothelial or smooth muscle cell markers. Occasionally, the use of high-power laser scanning confocal microscopy uncovered false-positive results because of overlap of different fluorescent signals from adjacent cells. Nevertheless, we observed accumulations of GFP-positive cells around growing collateral arteries (3-fold increase versus nonoccluded side, P<0.001) and in ischemic distal hindlimbs. These cells were identified as fibroblasts, pericytes, and primarily leukocytes that stained positive for several growth factors and chemokines. Our findings suggest that in the adult organism, bone marrow-Derived cells do not promote vascular growth by incorporating into vessel walls but may function as supporting cells.

Inhibition of collateral artery growth by mibefradil: possible role of volume-regulated chloride channels.

Endothelial cell swelling is one of the earliest hallmarks of arteriogenesis, the growth and maturation of collaterals. Mibefradil was found to block endothelial Cl(-) channels that control the volume of endothelial cells. Thus the authors investigated whether the blockade of volume-controlling endothelial cell channels would translate into an inhibition of arteriogenesis. In BALB/c mice, the right femoral artery was ligated and the animals received either mibefradil or solvent (phosphate-buffered saline [PBS]) via osmotic minipumps. Laser Doppler perfusion ratio (R/L) of ligated versus nonligated distal hindlimb increased from 0.06 +/- 0.01 (immediately after ligation) to 0.25 +/- 0.02 (day 7) in the PBS group and only from 0.07 +/- 0.02 to 0.13 +/- 0.02 in the mibefradil group (p <.01). Collateral artery diameters were significantly smaller in the mibefradil group (61 +/- 4.7 microm) versus controls (77.3 +/- 0.9 microm) (p <.05). Relative hemoglobin oxygen saturation measurements confirmed these findings (p <.02). The inhibition of arteriogenesis in the mibefradil group suggests that endothelial Cl(-) channels are involved in the initiation of arteriogenesis.

Arteriogenesis is associated with an induction of the cardiac ankyrin repeat protein (carp).

OBJECTIVE: Collateral artery growth (arteriogenesis) can be induced in rabbit and mice by occlusion of the femoral artery. We aimed to identify genes that are differentially expressed during arteriogenesis. METHODS: 24 h after femoral ligation or sham operation collateral arteries were isolated from New Zealand white rabbits, mRNAs were extracted and amplified using the SMART technique. cDNAs were subjected to suppression subtractive hybridization. The differential expression was confirmed by Northern blot, Real time PCR and Western blot. Additionally, the gene expression was modulated in vivo by application of cytokines via osmotic minipumps. RESULTS: We found the cardiac ankyrin repeat protein (carp) mRNA to be upregulated at 24 h and already at 6 h and 12 h after surgery as shown by Northern blot hybridization and real time PCR. The carp mRNA was also increased in our mouse model of arteriogenesis. Western blot results on nuclear extracts of rabbit collaterals 24 h after surgery indicated that carp, which we showed to be expressed in endothelial cells and smooth muscle cells of collateral arteries by immunohistochemistry, was also upregulated on the protein level. We infused MCP-1, TGF-beta1 or doxorubicin for 24 h in rabbits and found that only TGF-beta1 led to an additional increase of carp mRNA. Overexpression of carp in cos-1 cells resulted in a 3.7-fold increase of the immediate early gene egr-1. CONCLUSIONS: Our results implicate that carp is associated with the initiation and regulation of arteriogenesis.

Circulating vascular progenitor cells do not contribute to compensatory lung growth.

The biological principles that underlie the induction and process of alveolization in the lung as well as the maintenance of the complex lung tissue structure are one of the major obstacles in pulmonary medicine today. Bone marrow-derived cells have been shown to participate in angiogenesis, vascular repair, and remodeling of various organs. We addressed this phenomenon in the lung vasculature of mice in a model of regenerative lung growth. C57BL/6 mice were transplanted with bone marrow from one of three different reporter gene-transgenic strains. flk-1+/lacZ mice, tie-2/lacZ transgenic mice (both exhibiting endothelial cell-specific reporter gene expression), and ubiquitously enhanced green fluorescent protein (eGFP)-expressing mice served as marrow donors. After hematopoietic recovery, compensatory lung growth was induced by unilateral pneumonectomy and led to complete restoration of initial lung volume and surface area. The lungs were consecutively investigated for bone marrow-derived vascular cells by lacZ staining and immunohistochemistry for phenotype identification of vascular cells. lacZ- or eGFP-expressing bone marrow-derived endothelial cells could not be found in microvascular regions of alveolar septa. Single eGFP-positive endothelial cells were detected in pulmonary arteries at very low frequencies, whereas no eGFP-positive vascular smooth muscle cells were observed. In conclusion, we demonstrate in a model of lung growth and alveolization in adult mice the absence of significant bone marrow-derived progenitor cell contribution to the concomitant vascular growth and remodeling processes.