Induction of in Vivo Ectopic Hematopoiesis by a Three-Dimensional Structured Extracellular Matrix Derived from Decellularized Cancellous Bone

An in vitro blood production system could be an alternative to blood donation. We constructed a hematopoietic microenvironment using decellularized cancellous bones (DCBs) as scaffolds to sustain hematopoietic stem cells and supporting cells. The subcutaneous implantation of DCBs into mice with or without human mesenchymal stem cells (hMSCs) revealed that regardless of the presence of hMSCs DCBs were recellularized by some host cells and induced hematopoiesis. The ability of DCB to promote hematopoiesis was investigated by focusing on the components and the structure of cancellous bone, specifically reticular and adipose tissues and trabecular bone. Two decellularization methods were used to prepare DCBs. The DCBs differed concerning reticular tissue and adipose tissue. DCBs with these tissues could be recellularized at the original cellular location. An implantation experiment with DCBs revealed that they were very favorable for the persistent homing of hematopoietic stem cells. In addition, DCBs promoted ectopic hematopoiesis. The findings indicate that reticular tissues are important in directing hematopoiesis of DCBs.

A fibrin-coated pericardial extracellular matrix prevented heart adhesion in a rat model

As most surgical treatments pose a risk of tissue adhesion, methods to prevent adhesion are needed across various surgical fields. In this study, we investigated the use of a decellularized pericardium with fibrin glue to prevent rat heart adhesion. Porcine pericardia were decellularized by a high-hydrostatic pressure method. Cells adhered to the resulting pericardial extracellular matrix (ECM) during an in vitro cell-seeding test, but fibrin-coated pericardial ECM showed reduced cell adhesion. In a rat surgical model of heart adhesion, the fibrin-coated pericardial ECM did not adhere to the heart and mesothelial cell adhesion was observed on the ECM surface. Notably, the anti-adhesion effect of fibrin-coated pericardial ECM was observed 4 weeks after surgery. These results support the utility of fibrin-coated pericardial ECM as an adhesion prevention material for cardiovascular surgery. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1088-1094, 2019.

[Rabbit Model for Evaluation of Anti-adhesive Materials after Open Heart Surgery]

Surgical trauma to the pericardial mesothelium during open heart procedures has formation of fibrovascular adhesions. Surgeons are confronted with cardiac adhesions, leading to an increased surgical risk such as intractable bleeding and possible catastrophic hemorrhage. In order to solve the problem, the anti-adhesion membrane has been developed and used. However, their performances are far from perfect, so it has been expected to develop a novel anti-adhesive material. For preparing an anti-adhesive material, there is 1 serious problem, a lack of golden standard of animal model for evaluation of anti-adhesivity. In this study, we tried to establish a standard system for evaluation of the performance of anti-adhesive materials for the chest-area surgery using rabbit. Setting the condition of the damage to heart, the objective evaluation system was established. And we performed experimental study to evaluate prevention of adhesions with pericardial substitutes and our product under development based on this model.

Water absorption by decellularized dermis

Water absorption by decellularized dermis was investigated and compared with biopolymer and synthetic polymer hydrogels (glutaraldehyde-crosslinked gelatin and crosslinked poly(acrylamide) hydrogel, respectively). Porcine dermis was decellularized in an aqueous sodium dodecyl sulfate (SDS) solution. Histological evaluation revealed that the SDS-treated dermis has much larger gaps between collagen fibrils than non-treated dermis, and that water absorption depends on these gaps. Decellularized dermis has low water absorptivity and the absorption obeys Fick's second law. During absorption, the water diffusion rate decreases with time and occurs in two steps. The first is rapid absorption into the large gaps, followed by slow absorption by the collagen fiber layer. Because of the gaps, decellularized dermis can absorb more water than native dermis and shows different water absorption behavior to glutaraldehyde-crosslinked gelatin and crosslinked poly(acrylamide) hydrogels.

Cell transfer technology for tissue engineering

We recently developed novel cell transplantation method “cell transfer technology” utilizing photolithography. Using this method, we can transfer ex vivo expanded cells onto scaffold material in desired patterns, like printing of pictures and letters on a paper. We have investigated the possibility of this novel method for cell-based therapy using several disease models. We first transferred endothelial cells in capillary-like patterns on amnion. The transplantation of the endothelial cell-transferred amnion enhanced the reperfusion in mouse ischemic limb model. The fusion of transplanted capillary with host vessel networks was also observed. The osteoblast- and periodontal ligament stem cell-transferred amnion were next transplanted in bone and periodontal defects models. After healing period, both transplantations improved the regeneration of bone and periodontal tissues, respectively. This method was further applicable to transfer of multiple cell types and the transplantation of osteoblasts and periodontal ligament stem cell-transferred amnion resulted in the improved bone regeneration compared with single cell type transplantation. These data suggested the therapeutic potential of the technology in cell-based therapies for reperfusion of ischemic limb and regeneration of bone and periodontal tissues. Cell transfer technology is applicable to wide range of regenerative medicine in the future.

Capture and release of cells using a temperature-responsive surface that immobilizes an antibody through DNA duplex formation

We synthesized a temperature-responsive surface that immobilized an antibody via DNA duplex formation for selective capture and release of target cells. Polyethylene films were modified by grafting poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAAm-co-AAc)), which were prepared at various ratios of NIPAAm/AAc. The increased hydrophilicity of P(NIPAAm-co-PAA) film with decreased temperature was confirmed by water contact angle measurement. Single strand DNA (20mer) was chemically immobilized on the surface and then antibody (anti-mouse CD45, mCD45) modified with the complementary single strand DNA was immobilized on the surface through DNA duplex formation. The mCD45 antibody immobilization was confirmed by immunostaining. HeLa cells (mCD45 negative) and mouse bone marrow (BM) cells (mCD45 positive) were adhered on the surfaces at 37 °C. Although HeLa cells were detached by 4 °C incubation, BM cells were still adhered on the surface and then the adhered cells were released by DNase treatment. From these results, it was suggested that cells could be selectively captured and collected by using a film having surface that immobilizes an antibody via DNA duplex formation.

Evaluation of small-diameter vascular grafts reconstructed from decellularized aorta sheets

Following small-diameter vascular grafting, blood vessels fail to retain excellent antithrombotic function and therefore require application of antithrombogenic drugs. We have previously reported early attachment of endothelial cells to the luminal surface of high hydrostatic pressure (HHP)-decellularized arteries after transplantation. In addition, the graft retained antithrombotic function by endothelialization and remained open for several weeks. To fabricate tube grafts of optimal size and shape for small-diameter vascular grafting, we evaluated decellularized porcine aorta sheets as a suitable antithrombogenic material. Porcine aortic sheets were decellularized using detergent-based or HHP methods. The HHP-, but not detergent-based-, decellularized aortic sheets were verified to be acellular, and the mechanical properties of the native aortic sheet remained intact. To fabricate vascular grafts, the decellularized aortic sheets were rolled into tubes and secured using fibrin glue bonding. After implantation into a rat carotid artery model, the tubular grafts withstood normal blood pressure, mechanical beating, and pulsatile flow. After 3 weeks, the tubular grafts remained patent and recipient cell infiltration and cell attachment were observed on the luminal surface. These results indicate that HHP-decellularized aortic sheets may be useful as an antithrombogenic material for tubular vascular grafts. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1293-1298, 2017.

Immobilization of Human Vascular Endothelial Growth Factor (VEGF165) onto Biomaterials: An Evaluation of the Biological Activity of Immobilized VEGF165

Human vascular endothelial growth factors (VEGF) are angiogenic factors that induce specific endothelial cell proliferation. In this study, VEGF165, which contains 165 amino acids, was immobilized onto poly(acrylic acid) grafted polyethylene) films (PAAc-g-PE). VEGF165 was immobilized via a reaction between the amino group of VEGF165 and the carboxyl group of PAAc using water-soluble carbodiimide. Using cultured human umbilical vein endothelial cells (HUVEC), adhesion, proliferation, and migration of the cells were evaluated with three kinds of protein that were immobilized on the PE films. The proteins used were collagen (type IV), fibronectin (FN), and VEGF165. The adhesion of HUVEC was enhanced by the immobilization of collagen or FN and by the co-immobilization of VEGF with FN, but not VEGF alone. The VEGF FN-co-immobilized surface showed cell growth promotion activity. Endothelialization was observed only on the collagen-immobilized or VEGF FN-co-immobilized film surfaces. We proposed that the VEGF with FN-co-immobilized biomaterials could be used for artificial vessels and for other tissue engineering scaffolds.

Polymer Drugs and Polymeric Drugs X: Slow Release of 5-Fluorouracil from Biodegradable Poly(γ-Glutamic Acid) and its Benzyl Ester Matrices

We prepared poly(γ-glutamic acid)(γ-PGA) benzyl ester(γ-PBG) by the esterification of γ-PGA and benzyl bromide and evaluated the degradation behavior and its usefulness as a drug delivery system (DDS) matrix using 5-fluorouracil (5-FU) as a model drug. γ-PBG degraded in an acidic solution gradually for up to 130 days, and degraded very slowly in a phosphate buffer solution (pH 7.4). After 150 days, the weight loss of the γ-PBG film was only 10% in a phosphate buffer solution. A slow release of 5-FU from γ-PBG films was achieved. The release rate was affected by the pH of the outer solution and the loading drug. We observed an initial burst-release on the first day, after that, the release of 5-FU was diffusion-controlled. γ-PBG may be a novel biodegradable material that may be useful in the pharmaceutical, biomedical, and agricultural fields.

Ultrastructural analysis of the decellularized cornea after interlamellar keratoplasty and microkeratome-assisted anterior lamellar keratoplasty in a rabbit model

The decellularized cornea has received considerable attention for use as an artificial cornea. The decellularized cornea is free from cellular components and other immunogens, but maintains the integrity of the extracellular matrix. However, the ultrastructure of the decellularized cornea has yet to be demonstrated in detail. We investigated the influence of high hydrostatic pressure (HHP) on the decellularization of the corneal ultrastructure and its involvement in transparency, and assessed the in vivo behaviour of the decellularized cornea using two animal transplantation models, in relation to remodelling of collagen fibrils. Decellularized corneas were prepared by the HHP method. The decellularized corneas were executed by haematoxylin and eosin and Masson's trichrome staining to demonstrate the complete removal of corneal cells. Transmission electron microscopy revealed that the ultrastructure of the decellularized cornea prepared by the HHP method was better maintained than that of the decellularized cornea prepared by the detergent method. The decellularized cornea after interlamellar keratoplasty and microkeratome-assisted anterior lamellar keratoplasty using a rabbit model was stable and remained transparent without ultrastructural alterations. We conclude that the superior properties of the decellularized cornea prepared by the HHP method were attributed to the preservation of the corneal ultrastructure.

A lanostane triterpenoid and three cholestane sterols from Tilia kiusiana

Kiusianins A-D (1-4) were isolated from the leaves of a Japanese endemic plant, Tilia kiusiana, together with 14 known compounds. The structures of a new lanostane-type triterpenoid 1 and three new cholestane-type sterols 2-4 were elucidated by spectroscopic methods, including two dimensional (2D) NMR. All the compounds isolated were evaluated for their cytotoxicity against two human cancer cell lines, HeLa and HL-60.

Thermal denaturation behavior of collagen fibrils in wet and dry environment

We have developed a new minimally invasive technique--integrated low-level energy adhesion technique (ILEAT)--which uses heat, pressure, and low-frequency vibrations for binding living tissues. Because the adhesion mechanism of the living tissues is not fully understood, we investigated the effect of thermal energy on the collagen structure in living tissues using ILEAT. To study the effect of thermal energy and heating time on the structure of the collagen fibril, samples were divided in two categories-wet and dry. Further, atomic force microscopy was used to analyze the collagen fibril structure before and after heating. Results showed that collagen fibrils in water denatured after 1 minute at temperatures higher than 80 °C, while partial denaturation was observed at temperatures of 80 °C and a heating time of 1 min. Furthermore, complete denaturation was achieved after 90 min, suggesting that the denaturation rate is temperature and time dependent. Moreover, the collagen fibrils in dry condition maintained their native structure even after being heated to 120 °C for 90 min in the absence of water, which specifically suppressed denaturation. However, partial denaturation of collagen fibrils could not be prevented, because this determines the adhesion between the collagen molecules, and stabilizes tissue bonding.

Fabrication of fibrillized collagen microspheres with the microstructure resembling an extracellular matrix

Microspheres using artificial or natural materials have been widely applied in the field of tissue engineering and drug delivery systems. Collagen is being widely used for microspheres because of its abundancy in the extracellular matrix (ECM), and its good biocompatibility. The purpose of this study is to establish the appropriate condition for preparing collagen microspheres (CMS) and fibrillized collagen microspheres (fCMS) using water-in-oil (W/O) emulsion. Collagen can be tailored to mimic the native cell environment possessing a similar microstructure to that of the ECM by conditioning the aqueous solution. We focused on the preparation of stable and injectable CMS and fCMS which is stable and would promote the healing response. Controlling the interfacial properties of hydrophilic-lipophilic balance (HLB), we obtained CMS and fCMS with various sizes and various morphologies. The microsphere prepared with wetting agents showed good microsphere formation, but too low or too high HLB value caused low yield and uncontrollable size distribution. The change in the surfactant amount and the rotor speed also affected the formation of the CMS and fCMS, where the low surfactant amount and fast rotor speed produced smaller CMS and fCMS. In the case of fCMS, the presence of NaCl made it possible to prepare stable fCMS without using any cross-linker due to fibrillogenesis and gelling of collagen molecules. The microstructure of fCMS was similar to that of the native tissue indicating that the fCMS would replicate its function in vivo.