Shuhei Tara

Controlled-Release Basic Fibroblast Growth Factor for Peripheral Artery Disease: Comparison with Autologous Bone Marrow-Derived Stem Cell Transfer

OBJECTIVE We examined the safety and efficacy of controlled-release basic fibroblast growth factor (b-FGF) for peripheral artery disease (PAD), compared with autologous bone marrow mononuclear cell implantation (BMCI). BACKGROUND We recently developed a b-FGF-incorporated biodegradable hydrogel that enables slow-releasing drug delivery system. METHODS PAD patients were divided into a b-FGF group (n=10) and BMCI group (n=15). Injection of gelatin hydrogel containing 600 μg b-FGF or BMCI (0.4-5.1×10(10) cell) was performed. Visual analog pain scale (VAS), (99m)technetium-tetrofosmin (Tc-TF) scintigraphy, transcutaneous oxygen tension (TcPO(2)), and ankle-brachial index (ABI) were evaluated before and 4 weeks after each treatment, and 2-year prognosis was determined. RESULTS VAS (b-FGF 67±15 to 4±5, p<0.01, BMCI 67±42 to 5±9 mm, p<0.01) and TcPO(2) (b-FGF 16±14 to 47±17, p<0.01, BMCI 13±13 to 37±21 mmHg, p<0.01) were significantly improved in both groups. Tc-TF and ABI were not changed. Prognosis was similar between the groups (b-FGF 91%, BMCI 80%, NS). CONCLUSION Controlled-release b-FGF is as safe as BMCI, and its efficacy appears to be comparable. Thus, this therapy may be an alternative to BMCI.

Evaluation of remodeling process in small-diameter cell-free tissue-engineered arterial graft

OBJECTIVE Autologous grafts are used to repair atherosclerotic cardiovascular diseases; however, many patients lack suitable donor graft tissue. Recently, tissue engineering techniques have emerged to make biologically active blood vessels. We applied this technique to produce arterial grafts using established biodegradable materials without cell seeding. The grafts were evaluated in vivo for vessel remodeling during 12 months. METHODS Poly(L-lactide-co-ε-caprolactone) scaffolds reinforced by poly(lactic acid) (PLA) fiber were prepared as arterial grafts. Twenty-eight cell-free grafts were implanted as infrarenal aortic interposition grafts in 8-week-old female SCID/Bg mice. Serial ultrasound and micro computed tomography angiography were used to monitor grafts after implantation. Five grafts were harvested for histologic assessments and reverse transcription-quantitative polymerase chain reaction analysis at time points ranging from 4 months to 1 year after implantation. RESULTS Micro computed tomography indicated that most implanted mice displayed aneurysmal changes (three of five mice at 4 months, four of five mice at 8 months, and two of five mice at 12 months). Histologic assessments demonstrated extensive tissue remodeling leading to the development of well-circumscribed neovessels with an endothelial inner lining, a neointima containing smooth muscle cells and elastin, and a collagen-rich extracellular matrix. There were a few observed calcified deposits, located around residual PLA fibers at 12 months after implantation. Macrophage infiltration into the scaffold, as evaluated by F4/80 immunohistochemical staining, remained after 12 months and was focused mostly around residual PLA fibers. Reverse transcription-quantitative polymerase chain reaction analysis revealed that gene expression of Itgam, a marker for macrophages, and of matrix metalloproteinase 9 was higher than in native aorta during the course of 12 months, indicating prolonged inflammation (Itgam at 8 months: 11.75 ± 0.99 vs native aorta, P < .01; matrix metalloproteinase 9 at 4 months: 4.35 ± 3.05 vs native aorta, P < .05). CONCLUSIONS In this study, we demonstrated well-organized neotissue of cell-free biodegradable arterial grafts. Although most grafts experienced aneurysmal change, such findings provide insight into the process of tissue-engineered vascular graft remodeling and should allow informed rational design of the next generation of arterial grafts.

Well-organized neointima of large-pore poly(l-lactic acid) vascular graft coated with poly(l-lactic-co-ε-caprolactone) prevents calcific deposition compared to small-pore electrospun poly(l-lactic acid) graft in a mouse aortic implantation model

OBJECTIVE Tissue engineering techniques have emerged that allow bioresorbable grafts to be implanted that restore function and transform into biologically active arteries. However, these implants are susceptible to calcification during the remodeling process. The objective of this study was to evaluate the role of pore size of bioabsorbable grafts in the development of calcification. METHODS Two types of grafts were prepared: a large-pore graft constructed of poly(L-lactic acid) (PLA) fibers coated with poly(L-lactide-co-ε-caprolactone) (PLCL) (PLA-PLCL), and a small-pore graft made of electrospun PLA nanofibers (PLA-nano). Twenty-eight PLA-PLCL grafts and twenty-five PLA-nano grafts were implanted as infra-renal aortic interposition conduits in 8-week-old female SCID/Bg mice, and followed for 12 months after implantation. RESULTS Large-pore PLA-PLCL grafts induced a well-organized neointima after 12 months, and Alizarin Red S staining showed neointimal calcification only in the thin neointima of small-pore PLA-nano grafts. At 12 months, macrophage infiltration, evaluated by F4/80 staining, was observed in the thin neointima of the PLA-nano graft, and there were few vascular smooth muscle cells (VSMCs) in this layer. On the other hand, the neointima of the PLA-PLCL graft was composed of abundant VSMCs, and a lower density of macrophages (F4/80 positive cells, PLA-PLCL; 68.1 ± 41.4/mm(2) vs PLA-nano; 188.3 ± 41.9/mm(2), p = 0.007). The VSMCs of PLA-PLCL graft expressed transcription factors of both osteoblasts and osteoclasts. CONCLUSION These findings demonstrate that in mouse arterial circulation, large-pore PLA-PLCL grafts created a well-organized neointima and prevented calcific deposition compared to small-pore, electrospun PLA-nano grafts.

Development of small diameter nanofiber tissue engineered arterial grafts.

The surgical repair of heart and vascular disease often requires implanting synthetic grafts. While synthetic grafts have been successfully used for medium-to-large sized arteries, applications for small diameter arteries (<6 mm) is limited due to high rates of occlusion by thrombosis. Our objective was to develop a tissue engineered vascular graft (TEVG) for small diameter arteries. TEVGs composed of polylactic acid nanofibers with inner luminal diameter between 0.5 and 0.6 mm were surgically implanted as infra-renal aortic interposition conduits in 25 female C17SCID/bg mice. Twelve mice were given sham operations. Survival of mice with TEVG grafts was 91.6% at 12 months post-implantation (sham group: 83.3%). No instances of graft stenosis or aneurysmal dilatation were observed over 12 months post-implantation, assessed by Doppler ultrasound and microCT. Histologic analysis of explanted TEVG grafts showed presence of CD31-positive endothelial monolayer and F4/80-positive macrophages after 4, 8, and 12 months in vivo. Cells positive for α-smooth muscle actin were observed within TEVG, demonstrating presence of smooth muscle cells (SMCs). Neo-extracellular matrix consisting mostly of collagen types I and III were observed at 12 months post-implantation. PCR analysis supports histological observations. TEVG group showed significant increases in expressions of SMC marker, collagen-I and III, matrix metalloproteinases-2 and 9, and itgam (a macrophage marker), when compared to sham group. Overall, patency rates were excellent at 12 months after implantation, as structural integrity of these TEVG. Tissue analysis also demonstrated vessel remodeling by autologous cell.

Therapeutic Angiogenesis by Controlled-Release Fibroblast Growth Factor in a Patient With Churg-Strauss Syndrome Complicated by an Intractable Ischemic Leg Ulcer

Churg-Strauss syndrome (CSS) causes necrotizing vasculitis affecting small- to medium-sized arteries, mainly in the lungs, gastrointestinal system, heart, kidneys, and skin. Skin lesions sometimes ulcerate because of severe ischemia and become intractable when complicated by bacterial infection. We report a rare case of CSS, characterized by a nonhealing ischemic skin ulcer of the right calf with bacterial infection resistant to antibiotics. After sterile maggot debridement therapy, 2 skin autografts failed. Subsequently, a slow-release formula of basic fibroblast growth factor incorporated in biodegradable gelatin hydrogel was administered into the calf muscles to induce vascular regeneration. The ulcer eventually healed with no recurrence. This report describes the use of controlled-release basic fibroblast growth factor for an ischemic leg ulcer in a patient with CSS, suggesting a possible therapeutic role of this novel neovascularization therapy in treating severe skin lesions complicating autoimmune vasculitis syndromes.

Therapeutic vascular angiogenesis for intractable macroangiopathy-related digital ulcer in patients with systemic sclerosis: a pilot study

OBJECTIVE SSc causes intractable ischaemic ulcers. To avoid major amputation, we examined the safety and efficacy of therapeutic vascular angiogenesis for digital ulcers due to SSc. METHODS A single-centre, open-label pilot study was conducted in patients with an ischaemic digital ulcer [n = 40, mean age 65 years (s.d. 8), Rutherford class III-5 or III-6) due to lcSSc (n = 11) or arteriosclerosis obliterans (ASO; n = 29). Bone marrow mononuclear cells (0.4-5.1 × 10(10) cells in total) were administered into the ischaemic limbs. We evaluated short-term safety and efficacy by means of a pain scale, (99m)Tc-tetrofosmin scintigraphy and transcutaneous oxygen tension (TcPO2) before and 4 weeks after treatment. Also, the 2-year outcome was compared. RESULTS There was a case of amputation in each group within 4 weeks after therapy. The pain scale significantly decreased in both groups [lcSSc 93 mm (s.d. 9) to 11 (s.d. 16), P < 0.01; ASO 77 mm (s.d. 22) to 16 (s.d. 13), P < 0.01] and TcPO2 significantly improved [lcSSc 9.0 mmHg (s.d. 9) to 35 (s.d. 14), P < 0.01; ASO 18 mmHg (s.d. 10) to 29 (s.d. 21), P < 0.05). At the 2-year follow-up, the limb amputation rate was 9.1% in lcSSc and 20.7% in ASO (P = 0.36), while the recurrence rate was 18.2% in lcSSc and 17.2% in ASO (P = 0.95). All-cause mortality was 27.3% in lcSSc and 17.2% in ASO (P = 0.65). CONCLUSION In patients with lcSSc, bone marrow mononuclear cell implantation provides clinical benefit and is safe, without major adverse reactions, and may become an effective strategy. TRIAL REGISTRATION UMIN-CTR, http://www.umin.ac.jp/ctr/index-j.htm, no. UMIN000004112.

Rational design of an improved tissue-engineered vascular graft: determining the optimal cell dose and incubation time

AIM We investigated the effect of cell seeding dose and incubation time on tissue-engineered vascular graft (TEVG) patency. MATERIALS & METHODS Various doses of bone marrow-derived mononuclear cells (BM-MNCs) were seeded onto TEVGs, incubated for 0 or 12 h, and implanted in C57BL/6 mice. Different doses of human BM-MNCs were seeded onto TEVGs and measured for cell attachment. RESULTS The incubation time showed no significant effect on TEVG patency. However, TEVG patency was significantly increased in a dose-dependent manner. In the human graft, more bone marrow used for seeding resulted in increased cell attachment in a dose-dependent manner. CONCLUSION Increasing the BM-MNC dose and reducing incubation time is a viable strategy for improving the performance and utility of the graft.

Implantation of Inferior Vena Cava Interposition Graft in Mouse Model

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are often used for reconstructive surgery to treat congenital cardiac anomalies. The long-term clinical results showed excellent patency rates, however, with significant incidence of stenosis. To investigate the cellular and molecular mechanisms of vascular neotissue formation and prevent stenosis development in tissue engineered vascular grafts (TEVGs), we developed a mouse model of the graft with approximately 1 mm internal diameter. First, the TEVGs were assembled from biodegradable tubular scaffolds fabricated from a polyglycolic acid nonwoven felt mesh coated with ε-caprolactone and L-lactide copolymer. The scaffolds were then placed in a lyophilizer, vacuumed for 24 hr, and stored in a desiccator until cell seeding. Second, bone marrow was collected from donor mice and mononuclear cells were isolated by density gradient centrifugation. Third, approximately one million cells were seeded on a scaffold and incubated O/N. Finally, the seeded scaffolds were then implanted as infrarenal vena cava interposition grafts in C57BL/6 mice. The implanted grafts demonstrated excellent patency (>90%) without evidence of thromboembolic complications or aneurysmal formation. This murine model will aid us in understanding and quantifying the cellular and molecular mechanisms of neotissue formation in the TEVG.

Fast-degrading bioresorbable arterial vascular graft with high cellular infiltration inhibits calcification of the graft

Objective: Bioresorbable vascular grafts are biologically active grafts that are entirely reconstituted by host‐derived cells through an inflammation‐mediated degradation process. Calcification is a detrimental condition that can severely affect graft performance. Therefore, prevention of calcification is of great importance to the success of bioresorbable arterial vascular grafts. The objective of this study was to test whether fast‐degrading (FD) bioresorbable arterial grafts with high cellular infiltration will inhibit calcification of grafts. Methods: We created two versions of bioresorbable arterial vascular grafts, slow‐degrading (SD) grafts and FD grafts. Both grafts had the same inner layer composed of a 50:50 poly(l‐lactic‐co‐&egr;‐caprolactone) copolymer scaffold. However, the outer layer of SD grafts was composed of poly(l‐lactic acid) nanofiber, whereas the outer layer of FD grafts was composed of a combination of poly(l‐lactic acid) and polyglycolic acid nanofiber. Both grafts were implanted in 8‐ to 10‐week‐old female mice (n = 15 in the SD group, n = 10 in the FD group) as infrarenal aortic interposition conduits. Animals were observed for 8 weeks. Results: von Kossa staining showed calcification in 7 of 12 grafts in the SD group but zero in the FD group (P < .01, χ2 test). The cell number in the outer layer of FD grafts was significantly higher than in the SD grafts (SD, 0.87 ± 0.65 × 103/mm2; FD, 2.65 ± 1.91 × 103/mm2; P = .02). Conclusions: The FD bioresorbable arterial vascular graft with high cellular infiltration into the scaffold inhibited calcification of grafts. Clinical Relevance: Bioresorbable vascular grafts are biologically active grafts that are entirely reconstituted by host‐derived cells throughout the life span of the patient. Calcification of the graft is a detrimental condition that can severely affect graft performance. Therefore, preventing graft calcification is of great importance to success of bioresorbable vascular grafts. We hypothesized that remaining scaffold polymer could affect graft calcification. Therefore, we created fast‐degrading bioresorbable arterial vascular grafts. We report here that no calcification occurred in the fast‐degrading grafts, although calcification occurred in the slow‐degrading grafts. These findings provide further strategies for prevention of calcification after implantation of bioresorbable vascular grafts in the clinical setting.

Tropoelastin inhibits intimal hyperplasia of mouse bioresorbable arterial vascular grafts

Neointimal hyperplasia, which results from the activation, proliferation and migration of vascular smooth muscle cells (SMCs), is a detrimental condition for vascular stents or vascular grafts that leads to stenosis. Preventing neointimal hyperplasia of vascular grafts is critically important for the success of arterial vascular grafts. We hypothesized that tropoelastin seeding onto the luminal surface of the graft would prevent neointimal hyperplasia through suppressing neointimal smooth muscle cell proliferation. In this study, we investigated the efficacy of tropoelastin seeding in preventing neointimal hyperplasia of bioresorbable arterial vascular grafts. Poly (glycolic acid) (PGA) fiber mesh coated with poly (l-lactic-co-ε-caprolactone) (PLCL) scaffolds reinforced by poly (l-lactic acid) (PLA) nano-fibers were prepared as bioresorbable arterial grafts. Tropoelastin was then seeded onto the luminal surface of the grafts. Tropoelastin significantly reduced the thickness of the intimal layer. This effect was mainly due to a substantial reduction the number of cells that stained positive for SMC (α-SMA) and PCNA in the vessel walls. Mature elastin and collagen type I and III were unchanged with tropoelastin treatment. This study demonstrates that tropoelastin seeding is beneficial in preventing SMC proliferation and neointimal hyperplasia in bioresorbable arterial vascular grafts. STATEMENT OF SIGNIFICANCE Small resorbable vascular grafts can block due to the over-proliferation of smooth muscle cells in neointimal hyperplasia. We show here that the proliferation of these cells is restricted in this type of graft. This is achieved with a simple dip, non-covalent coating of tropoelastin. It is in principle amendable to other grafts and is therefore an attractive process. This study is particularly significant because: (1) it shows that smooth muscle cell proliferation can be reduced while still accommodating the growth of endothelial cells, (2) small vascular grafts with an internal diameter of less than 1mm are amenable to this process, and (3) this process works for resorbable grafts.