Progressive Reinvention or Destination Lost? Half a Century of Cardiovascular Tissue Engineering.

The concept of tissue engineering evolved long before the phrase was forged, driven by the thromboembolic complications associated with the early total artificial heart programs of the 1960s. Yet more than half a century of dedicated research has not fulfilled the promise of successful broad clinical implementation. A historical account outlines reasons for this scientific impasse. For one, there was a disconnect between distinct eras each characterized by different clinical needs and different advocates. Initiated by the pioneers of cardiac surgery attempting to create neointimas on total artificial hearts, tissue engineering became fashionable when vascular surgeons pursued the endothelialisation of vascular grafts in the late 1970s. A decade later, it were cardiac surgeons again who strived to improve the longevity of tissue heart valves, and lastly, cardiologists entered the fray pursuing myocardial regeneration. Each of these disciplines and eras started with immense enthusiasm but were only remotely aware of the preceding efforts. Over the decades, the growing complexity of cellular and molecular biology as well as polymer sciences have led to surgeons gradually being replaced by scientists as the champions of tissue engineering. Together with a widening chasm between clinical purpose, human pathobiology and laboratory-based solutions, clinical implementation increasingly faded away as the singular endpoint of all strategies. Moreover, a loss of insight into the healing of cardiovascular prostheses in humans resulted in the acceptance of misleading animal models compromising the translation from laboratory to clinical reality. This was most evident in vascular graft healing, where the two main impediments to the in-situ generation of functional tissue in humans remained unheeded-the trans-anastomotic outgrowth stoppage of endothelium and the build-up of an impenetrable surface thrombus. To overcome this dead-lock, research focus needs to shift from a biologically possible tissue regeneration response to one that is feasible at the intended site and in the intended host environment of patients. Equipped with an impressive toolbox of modern biomaterials and deep insight into cues for facilitated healing, reconnecting to the "user needs" of patients would bring one of the most exciting concepts of cardiovascular medicine closer to clinical reality.

Long-term experience in autologous in vitro endothelialization of infrainguinal ePTFE grafts.

OBJECTIVE: Based on a previous randomized study showing significantly superior patency rates for in vitro endothelialized expanded polytetrafluoroethylene (ePTFE) grafts we investigated whether it was feasible for a nontertiary institution to offer autologous in vitro endothelialization to all elective infrainguinal bypass patients who had no suitable saphenous vein available. METHODS: Over a period of 15 years, 310 out of 318 consecutive nonacute patients (age 64.7 +/- 8.6) received 341 endothelialized ePTFE grafts (308 femoropopliteal: 153 above knee [AK] and 155 below knee [BK] and 33 femorodistal). Autologous endothelial cells were harvested from short segments (3.9 +/- 1.1 cm) of subcutaneous veins (80% cephalic, 11% basilic, 2% external jugular, and 7% saphenous) and grown to mass cultures within 18.9 +/- 4.5 days before being confluently lined onto fibrin glue-coated ePTFE grafts. The graft diameter was 6 mm (64%) or 7 mm (36%). The overall procedure-related delay for graft implantation was 27.6 + 7.8 days. Growth failure prevented 2.5% of patients from receiving an endothelialized graft. The mean observation period was 9.6 years. Primary patencies were obtained from Kaplan-Meier survivorship functions. Explants for morphological analysis were obtained from eight patients. RESULTS: The overall primary patency rate of femoropopliteal grafts was 69% at 5 years (68% [AK] vs 71% [BK]) and 61% at 10 years (59% [AK] vs 64% [BK]). Primary patency of 7 mm vs 6 mm grafts was 78%/62% at 5 years and 71%/55% at 10 years. The difference between the two groups was statistically significant (log rank test P = .023; Breslow test P = .017). Stage I vs II/III patients showed 5-year patencies of 67% vs 73% (N.S.) and 10-year patencies of 61%% vs 53% (N.S.). The primary patency of femorodistal grafts was 52% at 5 years and 36% at 10 years. The limb salvage rate was 94% (fempop) vs 86% (femdistal) at 5 years and 89% vs 71% at 10 years. All retrieved samples showed the presence of an endothelium after 38.9 +/- 17.8 months. CONCLUSION: Autologous in vitro endothelialization was shown to be a feasible routine procedure at a nontertiary hospital. Explants confirmed the presence of an endothelium years after implantation while the primary patency in the particularly challenging subgroup of patients without a suitable saphenous vein resembles that of vein grafts.

Enhanced endothelial cell retention on shear-stressed synthetic vascular grafts precoated with RGD-cross-linked fibrin.

Clinical in vitro endothelialization has been shown to increase the patency of synthetic vascular grafts. The shear stress resistance of the cultured autologous endothelium represents a crucial cornerstone of the concept. We investigated whether an enrichment of the precoating matrix with adhesion sites can augment endothelial cell attachment. Adult human saphenous vein endothelial cells (AHSVECs) were seeded confluently ([58 +/- 11] x 10(3) AHSVECs/cm2) onto 10-cm-long ePTFE (expanded polytetrafluorethylene) vascular grafts (n = 24) precoated with commercial clinically approved fibrin gel (Tisseal) containing various concentrations of cross-linked RGD peptide (0.0, 4.0, 8.0, or 16.0 mg of RGD per milliliter of Tisseal fibrinogen component). Endothelialized grafts were postcultivated for 9 days before they were exposed to a pulsatile circulation model mimicking peak physiological shear stress conditions of the femoral artery (12 dyn/cm2; min/max, -60/+28 dyn/cm2). Cell loss after 24 h was quantitatively determined by image analysis of vital stains. Initial 24-h cell loss was 27.2 +/- 1.7% in grafts precoated with the non-RGD-enriched fibrin matrix. In contrast, cell loss was significantly less on fibrin containing 4.0 mg of RGD peptide per milliliter of Tisseal fibrinogen component (13.3 +/- 7.9%; p < 0.05). Cell loss on fibrin containing 8 and 16 mg of RGD per milliliter of Tisseal fibrinogen component was 41.0 +/- 27.4 and 43.0 +/- 23.2% (p > 0.05), respectively. We conclude that low concentrations of RGD peptide cross-linked into commercial fibrin matrices used for clinical in vitro lining of vascular grafts led to significantly increased endothelial cell retention. The failure of higher RGD concentrations to enhance endothelial cell attachment may be explained by competitive binding of endothelial cells to non-cross-linked RGD.

Mitral valve repair with the Colvin-Galloway Future Band.

BACKGROUND: A new annuloplasty device, the Colvin-Galloway Future Band, has been developed to allow simple and safe mitral valve repair surgery. Here we report its clinical use and the clinical results after a short-term, 2-year follow-up. METHODS: We assessed the performance of this new device in 40 consecutive patients (55% male; mean age, 68.3 +/- 8.1 years) who were operated on for mitral valve incompetence between 2001 and 2002. Ninety percent of these patients had associated surgical procedures. Clinical and echocardiographic assessment was performed perioperatively and at a mean follow-up of 16.5 +/- 5.7 months (range, 6 to 25 months) in all patients (100%), permitting analysis of 55 patient-years. RESULTS: Thirty-eight patients survived surgery, resulting in an overall early mortality of 5.0%. There were four noncardiac-related late deaths, resulting in an overall late mortality of 10.0%. Perioperative echocardiography showed no incidences of systolic anterior movement at the time of discharge from the hospital and satisfactory mitral repair results in 36 (95%) patients. At the time of the 2-year follow-up, echocardiography showed satisfactory mitral valve function in all but 2 patients (94%) and a significant postoperative ventricular remodeling: the left ventricular end-diastolic diameter decreased from 64.5 +/- 6.2 mm preoperatively to 50.4 +/- 9.5 mm postoperatively (p < 0.1). At the time of follow-up, 29 (90.6%) patients were in New York Heart Association functional class I or II, all of them describing their quality of life as "significantly improved" if compared with their preoperative status. There were no late reoperations and no thromboembolic, bleeding, or other complications. CONCLUSIONS: The clinical results of the Colvin-Galloway Future Band in this short-term follow-up of patients undergoing complex mitral valve repair seem to be promising.

Antineutrophil cytoplasmic autoantibody-negative antiproteinase 3 syndrome presenting as vasculitis, endocarditis, polyneuropathy and Dupuytren's contracture.

Antiproteinase 3 antibodies (antiPR3) are assumed to be subtypes of antineutrophil cytoplasmic autoantibodies (ANCA), with a high specificity for active Wegener's granulomatosis and microscopic polyangiitis. Thus, antiPR3 positivity in ELISA, together with negativity in indirect immunofluorescence (IIF) is a rare finding. A 56-year-old man with Dupuytren's contracture and polyneuropathy was admitted for leukocytoclastic vasculitis. Echocardiography, performed because of fever and dyspnea, detected aortic valve endocarditis. Because of severe aortic insufficiency the valve was replaced. Blood cultures and bacteriologic investigations of the explanted valve were negative. AntiPR3 were elevated (123-163 U/ml; normal <6 U/ml), together with negativity in IIF. This case shows that antiPR3 elevation with negative ANCA may be associated with vasculitis, endocarditis, polyneuropathy and Dupuytren's contracture. A causal relationship between the clinical presentation and antiPR3 elevation is likely. In order not to miss such cases of vasculitis, combined screening by IIF and ELISA is recommended in selected cases.

Hyperlipidemia coincides with reversible growth impairment of cultured human autologous endothelial cells.

Patient-related risk factors for the growth of autologous endothelial cells were assessed in a clinical series of 100 consecutive recipients of in vitro endothelialized prosthetic vascular grafts. For all patients, the indication for bypass operation was arteriosclerotic occlusive disease of the distal arteries. Endothelial cells were harvested from a small piece of subdermal vein and cultured in medium containing 20% of autologous serum. Growth was continually monitored. In cultures that failed to grow, the autologous serum supplement to the culture medium was replaced by pooled homologous serum from young healthy donors. The comparison of a multitude of serum parameters between patients whose endothelial cells failed to grow and those showing normal growth revealed a significant difference in serum lipid content: triglycerides: 4.76 +/- 3.36 versus 2.83 +/- 2.28 mmol/L (p = .001); cholesterol: 6.78 +/- 1.69 versus 5.69 +/- 1.32 mmol/L (p = .003); and lipoprotein (a): 35.9 +/- 28.3 versus 22.2 +/- 26.6 mg/dl (p = .04). Following serum exchange with low-lipid pool serum that contained 1.74 mmol/L triglycerides, 4.86 mmol/L cholesterol, 5 mg/dl lipoprotein (a), and 5.79 mmol/L glucose, a remarkable recovery occurred in 85% of these cultures, resulting in fully restored proliferative capacity. As a consequence, population doubling time did not differ between the two groups at any point in time and mass cultures sufficient for confluent graft endothelialization were obtained with hardly any delay. The authors conclude that hyperlipidemia may lead to growth impairment of cultured human endothelial cells. This growth inhibition is reversible if the supplemented autologous serum is replaced by pooled serum with low lipid content.