Katsuaki Ono

Photocrosslinkable chitosan as a dressing for wound occlusion and accelerator in healing process

Application of ultraviolet light (UV-) irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution resulted in an insoluble, flexible hydrogel like soft rubber within 60 s. The chitosan hydrogel could completely stop bleeding from a cut mouse tail within 30 s of UV-irradiation and could firmly adhere two pieces of sliced skins of mouse to each other. In order to evaluate its accelerating effect on wound healing, full thickness-skin incisions were made on the back of mice and subsequently an Az-CH-LA aqueous solution was added into the wound and irradiated with UV light for 90 s. Application of the chitosan hydrogel significantly induced wound contraction and accelerated wound closure and healing. Histological examinations also have demonstrated an advanced granulation tissue formation and epithelialization in the chitosan hydrogel treated wounds. The chitosan hydrogel due to its accelerating healing ability is considered to become an excellent dressing for wound occlusion and tissue adhesive in urgent hemostasis situations.

Photocrosslinkable chitosan as a biological adhesive

A photocrosslinkable chitosan to which both azide and lactose moieties were introduced (Az-CH-LA) was prepared as a biological adhesive for soft tissues and its effectiveness was compared with that of fibrin glue. Introduction of the lactose moieties resulted in a much more water-soluble chitosan at neutral pH. Application of ultraviolet light (UV) irradiation to photocrosslinkable Az-CH-LA produced an insoluble hydrogel within 60 s. This hydrogel firmly adhered two pieces of sliced ham with each other, depending upon the Az-CH-LA concentration. The binding strength of the chitosan hydrogel prepared from 30-50 mg/mL of Az-CH-LA was similar to that of fibrin glue. Compared to the fibrin glue, the chitosan hydrogel more effectively sealed air leakage from pinholes on isolated small intestine and aorta and from incisions on isolated trachea. Neither Az-CH-LA nor its hydrogel showed any cytotoxicity in cell culture tests of human skin fibroblasts, coronary endothelial cells, and smooth muscle cells. Furthermore, all mice studied survived for at least 1 month after implantation of 200 microL of photocrosslinked chitosan gel and intraperitoneal administration of up to 1 mL of 30 mg/mL of Az-CH-LA solution. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving as a new tissue adhesive in medical use.

Acceleration of wound contraction and healing with a photocrosslinkable chitosan hydrogel

Application of ultraviolet light irradiation to a photocrosslinkable chitosan aqueous solution resulted in an insoluble, flexible hydrogel like soft rubber within 60 seconds. In order to evaluate its accelerating effect on wound healing, full‐thickness skin incisions were made on the backs of mice and subsequently a photocrosslinkable chitosan aqueous solution was added into the wound and irradiated with UV light for 90 seconds. Application of the chitosan hydrogel significantly induced wound contraction and accelerated wound closure and healing compared with the untreated controls. Histological examination also showed an advanced contraction rate on the first 2 days and tissue fill rate on days 2 to 4 in the chitosan hydrogel‐treated wounds. Furthermore, in cell culture studies, chitosan hydrogel culture medium supplemented with 5% fetal–bovine serum was found to be chemoattractant for human dermal fibroblasts in an invasion chamber assay using filters coated with Matrigel and in a cell migration assay. Due to its ability to accelerate wound contraction and healing, chitosan hydrogel may become accepted as an occlusive dressing for wound management.

Heparin-carrying polystyrene to mediate cellular attachment and growth via interaction with growth factors.

Various sugar-carrying polystyrenes (PSs), which consist of synthetic styrene and sugar moieties, are glycoconjugates that are able to attach to polymeric surfaces. Heparin-carrying PS (HCPS) is especially able to retain the binding of heparin-binding growth factors (GFs) such as vascular endothelial GF 165 (VEGF(165)) or fibroblast GF 2 (FGF-2). Human skin fibroblast cells, human coronary smooth muscle cells, and human coronary endothelial cells have good adherence to the HCPS-coated plate. The growth rate of fibroblast cells on HCPS-coated plates is higher than or comparable to fibronectin-coated, gelatin-coated, or tissue culture treated plates, and the HCPS coating inhibits the growth of smooth muscle cells. On the other hand, the growth rate of endothelial cells on HCPS-coated plates in the presence of either VEGF(165) or FGF-2 is comparable to that on fibronectin-coated, gelatin-coated, and tissue culture treated plates. Endothelial cells grow at a higher rate on HCPS-coated plates retained with either VEGF(165) or FGF-2 than on the other coated plates. These results indicate that growth of various cells can be controlled by the HCPS coating, thereby retaining the bioactivity of molecules such as heparin-binding GFs. Thus, HCPS-coated surfaces control selective growth of various cells.

Photocrosslinkable chitosan: an effective adhesive with surgical applications

Abstract Background : As an effective adhesive with surgical applications, we designed a chitosan molecule (Az-CH-LA) that can be photocrosslinked by ultraviolet (UV) light irradiation, thus forming a hydrogel. The purpose of this work was to evaluate the effectiveness and safety of the photocrosslinkable chitosan hydrogel as an adhesive with surgical applications. Methods : The sealing ability of chitosan was evaluated as a bursting pressure, using the thoracic aorta, trachea, and lungs of farm pigs and was assessed in a rabbit model. The carotid artery and lung of rabbits were punctured with a needle and the use of the chitosan hydrogel stopped the bleeding and air leakage, respectively. In vivo chitosan degradability and biological responses were assessed histologically. Results : The sealing ability of the chitosan hydrogel was found to be similar or even stronger than that of fibrin. All rabbits whose carotid arteries or lungs were punctured with a needle and then sealed with the chitosan hydrogel stayed alive during a 1-month period, without bleeding or air leakage from the punctured site. Histological examinations demonstrated that, 30 days after application, a fraction of the chitosan hydrogel was phagocytozed by macrophages, partially degraded, and inducing the formation of fibrous tissue around the hydrogel. Conclusion : Photocrosslinkable chitosan showed strong sealing ability and potential use as a new tissue adhesive in surgical applications.

Successful resection of a glomus tumor arising from the lower trachea: Report of a case

Tracheal glomus tumors are extremely rare. We present herein the case of a 43-year-old man with hoarseness who was found to have a glomus tumor arising from the lower trachea. Bronchoscopy and chest computed tomography revealed a polypoid mass in the membranous portion of the trachea just above the carina. The patient underwent successful tracheal sleeve resection and reconstruction. A pathologic diagnosis of a glomus tumor with clear surgical margins was subsequently confirmed, and the patient is well 20 months postoperatively with an intact anastomosis.

Inhibition of neointimal proliferation in balloon-injured arteries using non-anticoagulant heparin-carrying polystyrene.

Non-anticoagulant heparin-carrying polystyrene (NAC-HCPS) has a higher activity to inhibit proliferation and migration of smooth muscle cells (SMCs) than heparin (Hep), periodate-oxidized (IO4-) Hep, and periodate-oxidized alkaline-degraded low molecular weight (IO4-LMW-) Hep. Less than 10 &mgr;g/ml of NAC-HCPS significantly inhibited the proliferation and migration of SMCs in vitro, while over 10-fold higher concentrations of Hep, IO4-Hep, and IO4-LMW-Hep were required to obtain the same inhibition. On the other hand, neointimal growth (intimal cross-section area and intimal cross-section area/medial cross-section area ratio) in vivo following vascular injury 28 days after balloon denudation in a rat carotid artery was substantially inhibited with high dose of intravenous administration (total 30 mg) of respectively IO4-Hep, IO4-LMW-Hep, and NAC-HCPS. A low-dose (total 10 mg) administration of IO4-Hep and IO4-LMW-Hep did not prevent the neointimal growth when compared with the control; only NAC-HCPS (total 10 mg) was able to significantly inhibit the neointimal. Thus, NAC-HCPS has a more-than 10-fold larger activity to inhibit SMC activities such as proliferation and migration in vitro, when comparing with Hep, IO4-Hep, and IO4-LMW-Hep; NAC-HCPS also prevents neointimal growth in vivo at lower doses.