In situ transplantation of adipose tissue-derived stem cells organized on porous polymer nanosheets for murine skin defects.

Stem cell transplantation is expected to be an effective early-phase treatment for deep burn injuries and intractable ulcers. Localizing and proliferating stem cells on the lesion utilizing engineered scaffolds is important for this treatment. In this study, we demonstrated in situ transplantation of adipose-tissue derived stem cells (ASCs) organized on free-standing porous polymer ultrathin films (referred to as "porous nanosheets") to a skin defect model in diabetic mice. Porous nanosheets were prepared by a combination of micro-gravure coating with macrophase separation of poly(d,l-lactic acid) and polystyrene under a roll-to-roll process and solvent etching process with cyclohexane. The permeable structure of porous nanosheets (thickness of 150 nm, average pore diameter of 4 µm) allowed for proliferation of ASCs and also provided sufficient nutrient inflow into multilayered ASC constructs. Then, transplantation of a trilayered ASC-laden porous nanosheet achieved homogeneous transference of ASCs onto the skin lesion. Transplanted ASCs contributed to wound healing in a dorsal skin defect model in diabetic mice. Thus, cell transplantation using porous nanosheets will be a new method for promoting wound healing in diabetic and other kinds of refractory ulcers. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1363-1371, 2019.

The efficacy of basic fibroblast growth factor-loaded poly(lactic-co-glycolic acid) nanosheet for mouse wound healing.

Although human recombinant basic fibroblast growth factor (bFGF) is widely used for wound healing, daily treatment with bFGF is required because of its short half-life. An effective controlled-release system of bFGF is, therefore, desired in clinical settings. To investigate the efficacy of a bFGF-loaded nanosheet for wound healing, focusing on the controlled-release of bFGF, bFGF-loaded poly(lactic-co-glycolic acid) (PGLA) nanosheets were developed, and their in vitro release profile of bFGF and their in vivo efficacy for wound healing were examined. A polyion complex of positively charged human recombinant bFGF and negatively charged alginate was sandwiched between PLGA nanosheets (70 nm thick for each layer). The resulting bFGF-loaded nanosheet robustly adhered to silicon skin by observation using a microscratch test. bFGF was gradually and continuously released over three days in an in vitro incubation study. Treatment with the bFGF-loaded nanosheets (every 3 day for 15 days) as well as with a conventional bFGF spray effectively promoted wound healing of mouse dorsal skin defects with accelerated tissue granulation and angiogenesis, although the dose of bFGF used in the treatment with the bFGF nanosheets was approximately 1/20 of the sprayed bFGF. In conclusion, we developed a bFGF-loaded nanosheet that sustained a continuous release of bFGF over three days and effectively promoted wound healing in mice.

Sustainable antimicrobial effect of silver sulfadiazine-loaded nanosheets on infection in a mouse model of partial-thickness burn injury.

Partial-thickness burn injury has the potential for reepithelialization and heals within 3weeks. If the wound is infected by bacteria before reepithelization, however, the depth of disruption increases and the lesion easily progresses to the full-thickness dermal layers. In the treatment of partial-thickness burn injury, it is important to prevent the wound area from bacterial infection with an antimicrobial dressing. Here, we have tested the antimicrobial properties of polymeric ultra-thin films composed of poly(lactic acid) (termed "PLA nanosheets"), which have high flexibility, adhesive strength and transparency, and silver sulfadiazine (AgSD), which exhibits antimicrobial efficacy. The AgSD-loaded nanosheet released Ag(+) for more than 3days, and exerted antimicrobial efficacy against methicillin-resistant Staphylococcus aureus (MRSA) in an in vitro Kirby-Bauer test. By contrast, a cell viability assay indicated that the dose of AgSD used in the PLA nanosheets did not show significant cytotoxicity toward fibroblasts. In vivo evaluation using a mouse model of infection in a partial-thickness burn wound demonstrated that the nanosheet significantly reduced the number of MRSA bacteria on the lesion (more than 10(5)-fold) and suppressed the inflammatory reaction, thereby preventing a protracted wound healing process.

[A rare case of disseminated Mycobacterium kansasii infection].

Mycobacterium kansasii infection has been reported to be about 20 percent of non-tuberculous mycobacteriosis, and its disseminated type is uncommon and the prognosis is reported to be generally poor. We experienced one case of disseminated Mycobacterium kansasii infection. A 81 year-old man who had been short-bowel syndrome due to the operation for superior mesenteric artery occlusion since 1998 was admitted on April 24th, 2001 to our hospital because of slowly progressive consciousness disturbance and anorexia. He had shown progressive productive cough and respiratory failure and laboratory findings were C-reactive protein elevation and pancytopenia. Human immunodeficiency virus (HIV) antibody was negative. Chest X-ray and computed tomography showed diffuse miliary nodules and infiltrative shadow. Sputum examination was positive for mycobacteria. The cultured isolate was identified as Mycobacterium kansasii. Bone marrow aspirations revealed inflammatory granuloma with necrosis. He was diagnosed as disseminated Mycobacterium kansasii infection and heart failure, and was treated by anti-tuberculosis drugs and diuretics. Treatment was very effective and Chest X-ray findings and respiratory failure had been completely improved. In this case we speculated that the malnutrition due to short-bowel syndrome could be one of the most suspected reasons of Mycobacterium kansasii dissemination. Disseminated Mycobacterium kansasii infection has been rarely reported comparing with the other mycobacterial infections in Japan. However, due to the increasing numbers of immunocompromised hosts with aging, HIV infection, cancer, and steroid therapy, this type of infection will become more common and its earlier diagnosis and adequate treatment will be important to improve the prognosis.