Reconstruction of small diameter arteries using decellularized vascular scaffolds

Although artificial vessels are available for large diameter arteries, there are no artificial vessels for small diameter arteries of < 4 mm. We created a decellularized vascular scaffold (length, 10 mm; outer diameter, 1.5 mm; inner diameter, 1.3 mm) from rat abdominal arteries. We measured the biomechanical characteristics of the scaffolds, implanted them to defects made in rat carotid arteries, and evaluated their patency and the endothelial cell linings. Silastic grafts were implanted as controls. The decellularized scaffolds demonstrated similar mechanical characteristics to normal arteries. All of the control grafts were occluded. Fibroblast-like cells were discovered in the thrombus, and fibrous organization was apparent. In contrast, patency of the grafts in 10 of 12 animals was observed 4 weeks after implantation. The internal cavity of the patent scaffold was completely lined by endotheliallike cells. Thus, the possibility of small artery reconstruction using decellularized scaffolds was demonstrated.

Application of a vacuum pressure impregnation technique for rehydrating decellularized tissues

Most of the clinically available decellularized tissues are preserved in a freeze-dried state. Freeze-dried (FD) tissues can be preserved for long term, although a rehydration process is necessary before use. Currently, an immersion method is most commonly used in clinical procedures, but it is difficult for complicated and thick structure tissue rehydration. In this study, we tried to apply a vacuum pressure impregnation (VPI) technique for FD tissue rehydration. The water content of decellularized tissues can reach the water content of native tissues within 30 min using VPI, whereas it took 6 h to reach the same water content using the immersion method. Furthermore, heparin rehydrated aortas by VPI had more heparin release at each time point and therefore appeared more anticoagulant activity. We found that the VPI treatment promotes solution infiltration into materials, achieves complete rehydration of the decellularized tissues, and deep infiltration of heparin into the decellularized tissues, suggesting that VPI treatment could be applied as a rehydration method for biological materials.

Decellularized dermis-polymer complex provides a platform for soft-to-hard tissue interfaces

To develop a soft-to-hard tissue interface, we made a decellularized dermis/poly(methyl methacrylate) (PMMA) complex by soaking the decellularized dermis in methyl methacrylate (MMA) and an initiator, and then polymerizing the MMA. The decellularized tissue was chosen because of its good biocompatibility and the easiness of suturing it, and MMA because of its hard tissue compatibility and wide use in the biomedical field. The MMA filled the cavities in the dermis and polymerized within 10 min. No leaking or polymer aggregation was observed, implying that a homogenous tissue-polymer complex had formed. The cell infiltration and the integration between the tissue and the dermis occurred in vivo, whereas the cells could not infiltrate the tissue-polymer complex. This implies that the interface tissue should possess both complex and noncomplex parts, where the cells infiltrate the noncomplex part and stop when they encounter the complex part, integrating the soft and hard tissue or hard polymer.

Static cardiomyoplasty with synthetic elastic net suppresses ventricular dilatation and dysfunction after myocardial infarction in the rat: a chronic study

Although static cardiomyoplasty prevents the left ventricle (LV) from dilatation, it may interfere with diastolic relaxation, or cause restriction. We developed a synthetic net with dual elasticity and tested its effect late after myocardial infarction in the rat. LV pressure-volume relationships (PVR) were successively analyzed before, after intravenous volume load, and 10 minutes after occlusion of the left anterior descending artery. Rats were then randomized into groups receiving synthetic net wrapping around the heart (NET+, n = 8) and only partially behind LV (NET-, n = 9), and they underwent the same PVR studies 6 weeks later. End-diastolic and end-systolic PVR were defined, and LV size and function were compared under standardized loading conditions. Although there was no difference in Day 0, increase in LV end-diastolic and end-systolic volumes were significantly attenuated in NET+ rats 6 weeks later when there was a significant correlation between LV volumes by PVR estimation and actual measurements, with significant differences in both measures between the groups: NET+ < NET-. The presence or absence of net did not show restrictive hemodynamics under acute volume load. Static cardiomyoplasty using a synthetic elastic net significantly attenuated LV dilatation and dysfunction without restriction late after myocardial infarction in the rat.

Porcine radial artery decellularization by high hydrostatic pressure

Many types of decellularized tissues have been studied and some have been commercially used in clinics. In this study, small-diameter vascular grafts were made using HHP to decellularize porcine radial arteries. One decellularization method, high hydrostatic pressure (HHP), has been used to prepare the decellularized porcine tissues. Low-temperature treatment was effective in preserving collagen and collagen structures in decellularized porcine carotid arteries. The collagen and elastin structures and mechanical properties of HHP-decellularized radial arteries were similar to those of untreated radial arteries. Xenogeneic transplantation (into rats) was performed using HHP-decellularized radial arteries and an untreated porcine radial artery. Two weeks after transplantation into rat carotid arteries, the HHP-decellularized radial arteries were patent and without thrombosis. In addition, the luminal surface of each decellularized artery was covered by recipient endothelial cells and the arterial medium was fully infiltrated with recipient cells.

The cytotoxic activity of diterpenoids from Isodon species

Fifteen Isodon diterpenoids (1-15) were evaluated for their cytotoxic activity against HeLa and HL-60 human cancer cell lines, and against murine vincristine (VCR)-resistant P388 cells. Kamebanin (14) showed efficient cytotoxic activity against HeLa and HL-60 cells. In addition, although dihydroenmein (2) and trichorabdal B (7) were inactive against several tested cell types, they were found to have cytotoxic-enhancing activity of VCR against VCR-resistant P388 cells.

The Cytotoxic Activity of Diterpenoids fromIsodonspecies

Fifteen Isodon diterpenoids (1–15) were evaluated for their cytotoxic activity against HeLa and HL-60 human cancer cell lines, and against murine vincristine (VCR)-resistant P388 cells. Kamebanin (14) showed efficient cytotoxic activity against HeLa and HL-60 cells. In addition, although dihydroenmein (2) and trichorabdal B (7) were inactive against several tested cell types, they were found to have cytotoxic-enhancing activity of VCR against VCR-resistant P388 cells.

Preparation of a hyaluronic acid hydrogel through polyion complex formation using cationic polylactide-based microspheres as a biodegradable cross-linking agent

A novel hyaluronic acid (HA)-based hydrogel was prepared through polyion complex (PIC) formation between cationic polylactide (PLA)-based microspheres (MS+) and hyaluronic acid (HA-) as an anionic polyelectrolyte. The MS+ and HA formed a biodegradable PIC hydrogel (HA-/MS+) when mixed in aqueous media. The swelling behavior and mechanical properties of the PIC hydrogel could be controlled by changing the charge ratio between HA- and MS+. In addition, the HA-/MS+ PIC hydrogel resulted in a lower inflammatory response compared with a collagen hydrogel in vivo.

Nano-vibration effect on cell adhesion and its shape

Extracellular physical features of underlying the adhesive substrate affect cell adhesion to it substrate. In this study, the effects of vibration, a type of artificial physical stimulation, on the adhesion of mouse L929 cells, mouse embryonic fibroblasts (MEFs), HeLa cells and human umbilical vein endothelial cells (HUVECs) are reported. A nano-vibration system was designed to produce nanometer-scale vibration. When L929 cells, HeLa cells, and HUVECs were subjected to vibration at 100 Hz and 1 kHz, they were not affected. On the other hand, in MEFs, the adherent cells were increased and changed their shape remarkably in response to 1 kHz vibration. To investigate the MEFs' sensitivity to vibration in detail, the cells shape was classified into four types; round, stellate, filopodia-formed and lamellipodia-formed. In serum addition culture, 1 kHz vibration increased the number of filopodia-formed cells but decreased lamellipodia cells. Furthermore, the preliminary cDNA microarray experiments showed that expression of genes which regulate cytoskeleton were changed by vibration stimulation. These results suggest that vibration could affect cell adhesion and the determination cell shape.

Effects of vibration on differentiation of cultured PC12 cells

Different types of physiological-mechanical stress, such as shear stress in vascular endothelial cells or hydrostatic pressure in chondrocytes are well known as regulators of cell function. In this study, the effects of vibration, a type of non-physiological mechanical stimulation, on differentiation of rat pheochromocytoma (PC12) cells are reported. A nano-vibration system was designed to produce nanometer-scale vibration. The frequency and amplitude of the nano-vibrations were monitored by a capacitance displacement sensor connected to an oscilloscope. When PC12 cells exposed to nerve growth factor were subjected to vibration at 10 kHz, differentiation and elongation of their neurites were promoted earlier in the culture. Vibration promoted differentiation of PC12 cells. This approach could therefore also be promising for determining of the effects of the physical environment on cell differentiation.

Therapeutic angiogenesis by implantation of a capillary structure constituted of human adipose tissue microvascular endothelial cells

OBJECTIVE

We previously reported a novel technology for the engineering of a capillary network using an optical lithographic technique. To apply this technology to the therapy of ischemic diseases, we tested human omental microvascular endothelial cells (HOMECs) as an autologous cell source and decellularized human amniotic membranes (DC-AMs) as a pathogen-free and low immunogenic transplantation scaffold.

METHODS AND RESULTS

Human umbilical vein endothelial cells were aligned on a patterned glass substrate and formed a capillary structure when transferred onto an amniotic membrane (AM). In contrast, HOMECs were scattered and did not form a capillary structure on AMs. Treatment of HOMECs with sphingosine 1-phosphate (S1P) inhibited HOMEC migration and enabled HOMEC formation of a capillary structure on AMs. Using quantitative RT-PCR and Western blot analyses, we demonstrated that the main S1P receptor in HOMECs is S1P(2), which is lacking in human umbilical vein endothelial cells, and that inhibition of cell migration by S1P is mediated through an S1P(2)-Rho-Rho-associated kinase signaling pathway. Implantation of capillaries engineered on DC-AMs into a hindlimb ischemic nude mouse model significantly increased blood perfusion compared with controls.

CONCLUSIONS

A capillary network consisting of HOMECs on DC-AMs can be engineered ex vivo using printing technology and S1P treatment. This method for regeneration of a capillary network may have therapeutic potential for ischemic diseases.

The use of high-hydrostatic pressure treatment to decellularize blood vessels

A decellularization method using high-hydrostatic pressure (HHP) technology (>600MPa) is described. The HHP disrupts the cells inside the tissue. The cell debris can be eliminated with a simple washing process, producing clean, decellularized tissue. In this study, porcine aortic blood vessel was decellularized by HHP. The mechanical properties and in vivo performance of the decellularized tissue were evaluated. Mechanical properties of the decellularized tissue were not altered by the HHP treatment. Reduced inflammation of the decellularized tissue was confirmed by xenogenic transplant experimentation. An allogenic transplantation study showed that decellularized blood vessel endured the arterial blood pressure, and there was no clot formation on the luminal surface. In addition, cellular infiltration into the vessel wall was observed 4 weeks after implantation, suggesting that HHP treatments could be applied widely as a high-quality decellularization method.