Subcutaneous islet transplantation is a promising treatment for severe diabetes; however, poor engraftment hinders its prevalence. We previously revealed that a gelatin hydrogel nonwoven fabric (GHNF) markedly improved subcutaneous islet engraftment in comparison with intraportal islet transplantation. We herein investigated whether the duration of pretreatment using GHNF affected the outcome of subcutaneous islet transplantation. A silicone spacer with GHNF was implanted into the subcutaneous space of healthy mice at 2, 4, 6, or 8 weeks before transplantation, and then diabetes was induced 7 days before transplantation. Syngeneic islets were transplanted into the pretreated space. Blood glucose, intraperitoneal glucose tolerance, immunohistochemistry, inflammatory mediators, and gene expression were evaluated. The 6-week group showed significantly better blood glucose changes than the other groups ( P < 0.05). The cure rate of the 6-week group (60.0%) was the highest among the groups (2-week = 0%, 4-week = 50.0%, 8-week = 15.4%). The number of von Willebrand factor (vWF)–positive vessels in the 6-week group was significantly higher than in the other groups at pre-islet and post-islet transplantation ( P < 0.01 [vs 2-and 4-week groups] and P < 0.05 [vs all other groups], respectively). Notably, this beneficial effect was also observed when GHNF was implanted into diabetic mice injected with streptozotocin 7 days before GHNF implantation. The positive rates for laminin, collagen III, and collagen IV increased as the duration of pretreatment became longer and were significantly higher in the 8-week group ( P < 0.01). Inflammatory mediators, including interleukin (IL)-1b, granulocyte colony-stimulating factor (G-CSF), and interferon (IFN)-γ, were gradually downregulated according to the duration of GHNF pretreatment and re-elevated in the 8-week group. Taken together, the duration of GHNF pretreatment apparently had an impact on the outcomes of subcutaneous islet transplantation, and 6 weeks appeared to be the ideal duration. Islet graft revascularization, extracellular matrix compensation of the islet capsule, and the inflammatory status at the subcutaneous space would be crucial factors for successful subcutaneous islet transplantation.

Clenbuterol (CB) is one of the β 2 -adrenergic receptor agonists with powerful muscle anabolic and lipolytic effects, and is prohibited as a doping drug for athletes. However, it is one of the candidate countermeasures for aging-related diseases. Previously we reported that CB induced muscular hypertrophy, but inhibited the longitudinal growth of bones in young male rats. However, the mechanism of the inhibitory effect on bone growth is not yet clear. CB is manufactured as a 1:1 racemic mixture of 2 isomers of (-)-R and (+)-S enantiomers, and only the (-)-R enantiomer may have pharmacological activity. We examined the effects of two CB enantiomers, (+)-S-CB and (-)-R-CB, on growth of striated muscle and bone in young male rats. Eighteen male Sprague-Dawley rats (8-wk-old) were randomly assigned to a control (CONT, n = 6) and two CB enantiomers groups ((+)-S-CLEB: n=6, (-)-R-CLEB: n=6). Each CB enantiomer of 2 mg/kg body weight was daily administered subcutaneously for 2 weeks. After treatment, heart and the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles and bones were analyzed. The muscle wet weights of SOL and EDL muscles significantly increased in (+)-S-CLEB (HEART: +28%, SOL: +25%, EDL: +28%) and (-)-R-CLEB (HEART: +27%, SOL: +29%, EDL: +35%). Both (+)-S-CB and (-)-R-CB induced striated muscle hypertrophy (heart, SOL, and EDL). Concerning bones, (+)-S-CB induced decreased tibia length (-1.2%) and decreased femur BMD (-5.8%), and (-)-R-CB induced decreased femur BMD (-8.2%). These results show that (+)-S-CB and (-)-R-CB might work differently at times.

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