Yuki Ichihara

Late-term results of tissue-engineered vascular grafts in humans

OBJECTIVE The development of a tissue-engineered vascular graft with the ability to grow and remodel holds promise for advancing cardiac surgery. In 2001, we began a human trial evaluating these grafts in patients with single ventricle physiology. We report the late clinical and radiologic surveillance of a patient cohort that underwent implantation of tissue-engineered vascular grafts as extracardiac cavopulmonary conduits. METHODS Autologous bone marrow was obtained and the mononuclear cell component was collected. Mononuclear cells were seeded onto a biodegradable scaffold composed of polyglycolic acid and epsilon-caprolactone/L-lactide and implanted as extracardiac cavopulmonary conduits in patients with single ventricle physiology. Patients were followed up by postoperative clinic visits and by telephone. Additionally, ultrasonography, angiography, computed tomography, and magnetic resonance imaging were used for postoperative graft surveillance. RESULTS Twenty-five grafts were implanted (median patient age, 5.5 years). There was no graft-related mortality (mean follow-up, 5.8 years). There was no evidence of aneurysm formation, graft rupture, graft infection, or ectopic calcification. One patient had a partial mural thrombosis that was successfully treated with warfarin. Four patients had graft stenosis and underwent successful percutaneous angioplasty. CONCLUSION Tissue-engineered vascular grafts can be used as conduits in patients with single ventricle physiology. Graft stenosis is the primary mode of graft failure. Further follow-up and investigation for the mechanism of stenosis are warranted.

Allogeneic Mesenchymal Stromal Cells Transplanted Onto the Heart Surface Achieve Therapeutic Myocardial Repair Despite Immunologic Responses in Rats.

Background Transplantation of allogeneic mesenchymal stromal cells (MSCs) is a promising treatment for heart failure. We have shown that epicardial placement of cell sheets markedly increases donor cell survival and augments therapeutic effects compared with the current methods. Although immune rejection of intramyocardially injected allogeneic MSCs have been suggested, allogeneic MSCs transplanted on the heart surface (virtual space) may undergo different courses. This study aimed to elucidate immunologic response against epicardially placed allogeneic MSCs, rejection or acceptance of these cells, and their therapeutic effects for heart failure. Methods and Results At 4 weeks after coronary artery ligation, Lewis rats underwent epicardial placement of MSC sheets from syngeneic Lewis or allogeneic Fischer 344 rats or sham treatment. At days 3 and 10 after treatment, similar ratios (≈50% and 30%, respectively) of grafted MSCs survived on the heart surface in both MSC sheet groups. By day 28, survival of syngeneic MSCs was substantially reduced (8.9%); survival of allogeneic MSCs was more extensively reduced (0.2%), suggesting allorejection. Correspondingly, allogeneic MSCs were found to have evoked an immunologic response, albeit low level, as characterized by accumulation of CD4+ T cells and upregulation of interleukin 6. Despite this alloimmune response, the allogeneic MSC sheet achieved myocardial upregulation of reparative factors, enhanced repair of the failing myocardium, and improved cardiac function to the equivalent degree observed for the syngeneic MSC sheet. Conclusions Allogeneic MSCs placed on the heart surface evoked an immunologic response; however, this allowed sufficient early phase donor cell survival to induce equivalent therapeutic benefits to syngeneic MSCs. Further development of this approach toward clinical application is warranted.

A new tissue-engineered biodegradable surgical patch for high-pressure systems

OBJECTIVES Ideal alternatives for replacing native arteries, which have biocompatibility such as growth potential, anti-thrombogenesis and durability, have yet to be discovered. We previously demonstrated the utility of tissue-engineered vascular autografts; however, the use of these autografts is limited to low-pressure conditions. The aim of this study was to create the tissue-engineered arterial patch (TEAP) that could be used in high-pressure systems, and to evaluate the maturation in this regenerative tissue. METHODS We developed a new biodegradable polymer scaffold, which is composed of a co-polymer of epsilon-caprolactone and lactide acid [P(CL/LA)] and a poly-L-lactide acid (PLLA). To obtain mechanical strength, we modified PLLA that is degraded by hydrolysis for 1-2 years in contrast to polyglycolic acid in our low-pressure study previously. We implanted an oval-shaped patch (30 × 15 mm) of this polymer without cell seeding into the descending aorta of 12 dogs, and followed the animals for 1, 3 and 6 months (n = 4 in each group). The cell proliferation in the patch was evaluated with histological and immunohistochemical methods. Additionally, the expression of vascular endothelial growth factor (VEGF) and smooth muscle myosin heavy chain (smMHC) mRNA in the patches was determined with reverse transcriptase-polymerase chain reaction. RESULTS Macroscopically, there was no incidence of rupture or aneurysmal formation on the patch. The luminal surface of the TEAP was covered with a single layer of endothelial cells stained with vWF immunohistochemically at 1 month after implantation. αSMA-positive cells that indicated smooth muscle cells and collagen fibres were observed in the patch and they increased over time. The VEGF mRNA expression in the patch at 1 month was significantly higher than that of native arterial tissue (1 month; 0.124 ± 0.017 ng/µl, native; 0.009 ± 0.003 ng/µl, P < 0.05). The smMHC mRNA expression gradually increased, and reached ∼ 60% of that of the native artery at 6 months (6 months: 0.351 ± 0.028 ng/µl, native: 0.540 ± 0.027 ng/µl). CONCLUSIONS We demonstrated the maturation of endothelial and smooth muscle cells in TEAP, suggesting that this biodegradable polymer scaffold could be used as an alternative vascular material even in high-pressure systems.

IL-4 as a Repurposed Biological Drug for Myocardial Infarction through Augmentation of Reparative Cardiac Macrophages: Proof-of-Concept Data in Mice

Recent research has shown that reparative (alternatively activated or M2) macrophages play a role in repair of damaged tissues, including the infarcted hearts. Administration of IL-4 is known to augment M2 macrophages. This translational study thus aimed to investigate whether IL-4 administration is useful for the treatment of myocardial infarction. Long-acting IL-4 complex (IL-4c; recombinant IL-4 mixed with anti-IL-4 monoclonal antibody as a stabilizer) was administered after coronary artery ligation in mice. It was observed that IL-4c administration increased accumulation of CD206+F4/80+ M2-like macrophages predominantly in the injured myocardium, compared to the control. Sorted cardiac M2-like macrophages highly expressed wide-ranging tissue repair-related genes. Indeed, IL-4c administration enhanced cardiac function in association with reduced infarct size and enhanced tissue repair (strengthened connective tissue formation, improved microvascular formation and attenuated cardiomyocyte hypertrophy). Experiments using Trib1−/− mice that had a depleted ability to develop M2 macrophages and other in-vitro studies supported that these IL-4-mediated effects were induced via M2-like macrophages. On the other hand, when administered at Day 28 post-MI, the effects of IL-4c were diminished, suggesting a time-frame for IL-4 treatment to be effective. These data represent proof-of-concept of efficacy of IL-4 treatment for acute myocardial infarction, encouraging its further development.

Self-assembling peptide hydrogel enables instant epicardial coating of the heart with mesenchymal stromal cells for the treatment of heart failure

Transplantation of mesenchymal stromal cells (MSCs) is an emerging therapy for the treatment of heart failure. However, the delivery method of MSC is currently suboptimal. The use of self-assembling peptide hydrogels, including PuraMatrix® (PM; 3-D Matrix, Ltd), has been reported for clinical hemostasis and in research models. This study demonstrates the feasibility and efficacy of an advanced approach for MSC-therapy, that is coating of the epicardium with the instantly-produced PM hydrogel incorporating MSCs (epicardial PM-MSC therapy). We optimized the conditions/procedure to produce “instant” 2PM-MSC complexes. After spreading on the epicardium by easy pipetting, the PM-MSC complex promptly and stably adhere to the beating heart. Of note, this treatment achieved more extensive improvement of cardiac function, with greater initial retention and survival of donor MSCs, compared to intramyocardial MSC injection in rat heart failure models. This enhanced efficacy was underpinned by amplified myocardial upregulation of a group of tissue repair-related genes, which led to enhanced repair of the damaged myocardium, i.e. augmented microvascular formation and reduced interstitial fibrosis. These data suggest a potential for epicardial PM-MSC therapy to be a widely-adopted treatment of heart failure. This approach may also be useful for treating diseases in other organs than the heart.

Ventricular Assist Device Implantation Late After Double Switch Operation for L-Transposition of the Great Arteries

We provided a left ventricular assist device (LVAD) for a 22-year-old man with congenital L-transposition of the great arteries after anatomic repair at the age of 7 years. He was hospitalized for progressive low-output syndrome caused by intractable biventricular failure. He received LVAD in his morphologic left ventricle with a concomitant pulmonary valve replacement. After the surgery, critical multiorgan failure with severe right heart failure occurred. It took three postoperative months to normalize all organ function following improvement of morphologic right ventricular function. He has remained stable with LVAD support for 1.5 years.

Modified Elephant Trunk Technique in Distal Anastomosis With the Aid of Antegrade Selective Cerebral Perfusion for Total Arch Replacement

BACKGROUND Secure distal anastomosis and reliable brain protection are indispensable for successful total arch replacement (TAR). In 2002, we introduced a modified elephant trunk technique, a novel approach to distal anastomosis, and employed antegrade selective cerebral perfusion. We retrospectively analyzed 107 consecutive patients to evaluate the efficacy of this technique for TAR with antegrade selective cerebral perfusion. METHODS Since 2002 we have employed moderate hypothermic circulatory arrest, selective antegrade cerebral perfusion, and open distal anastomosis with a modified elephant trunk technique in TAR. Between February 2002 and September 2011, 107 TARs were performed in 88 males and 19 females (age, 33 to 88 years; mean, 70.9±9.5 years). Etiologies of cases were as follows: 89 true aneurysm due to atherosclerosis; 5 infectious aneurysm; 1 aortic dilation with bicuspid aortic valve; 12 aortic dissection, including 1 of acute aortic dissection case; and 2 Marfan syndrome. Concomitant procedures included 19 coronary artery bypass grafting (CABG) cases, 2 aortic valve replacement cases, 1 mitral valve plasty case, 1 Bentall procedure case, and 1 case of Bentall with CABG. RESULTS The operative mortality within 30 days was 0.9% (1 of 107), and overall hospital mortality was 1.9% (2 of 107). Temporary and permanent neurologic dysfunction occurred in 5 patients each (4.7%). The Kaplan-Meier survival analysis revealed a 5-year survival rate of 91.8%. CONCLUSIONS The modified elephant trunk technique using selective antegrade cerebral perfusion provided secure distal anastomosis and demonstrated excellent results, with low operative mortality and few neurologic complications.

Fibrin Glue-aided, Instant Epicardial Placement Enhances the Efficacy of Mesenchymal Stromal Cell-Based Therapy for Heart Failure

Transplantation of mesenchymal stromal cells (MSCs) is a promising new therapy for heart failure. However, the current cell delivery routes result in poor donor cell engraftment. We therefore explored the role of fibrin glue (FG)-aided, instant epicardial placement to enhance the efficacy of MSC-based therapy in a rat ischemic cardiomyopathy model. We identified a feasible and reproducible method to instantly produce a FG-MSC complex directly on the heart surface. This complex exhibited prompt, firm adhesion to the heart, markedly improving initial retention of donor MSCs compared to intramyocardial injection. In addition, maintenance of retained MSCs was enhanced using this method, together contributing the increased donor cell presence. Such increased donor cell quantity using the FG-aided technique led to further improved cardiac function in association with augmented histological myocardial repair, which correlated with upregulation of tissue repair-related genes. We identified that the epicardial layer was eliminated shortly after FG-aided epicardial placement of MSCs, facilitating permeation of the donor MSC’s secretome into the myocardium enabling myocardial repair. These data indicate that FG-aided, on-site, instant epicardial placement enhances MSC engraftment, promoting the efficacy of MSC-based therapy for heart failure. Further development of this accessible, advanced MSC-therapy is justified.