The influence of nitric oxide synthase 2 on cutaneous wound angiogenesis.

BACKGROUND: Inducible nitric oxide synthase (nitric oxide synthase 2, NOS 2) inhibition significantly suppresses chronically ischaemic skin flap survival, possibly because of reduced angiogenesis. OBJECTIVES: To investigate the effect of genetic NOS 2 inhibition on cutaneous wound angiogenesis in two in vivo murine models. The impact of NOS 2 manipulation on vascular endothelial growth factor (VEGF)-A stimulated and fibroblast growth factor (FGF)-2 stimulated angiogenesis was also investigated in the Matrigel(®) plug assay. METHODS: (i) Matrigel plugs/incisional wounds: two groups of NOS 2-/- mice and two groups of wild-type (WT) mice had bilateral Matrigel plugs containing 500 ng mL(-1) VEGF-A or 1000 ng mL(-1) FGF-2 injected subcutaneously in the abdomen. A 2·5 cm long dorsal incisional skin wound was created and sutured closed in the same animals. Wounds and plugs were explored at 7 or 12 days. (ii) Excisional wounds: dorsal 0·5 × 1·0 cm excisional skin wounds were created in four groups (two NOS 2-/- and two WT) and explored at 7 or 14 days. Wounds and Matrigel plugs were examined histologically and morphometrically for determination of percentage vascular volume (PVV). RESULTS: The PVV in NOS 2-/- incisional wounds and excisional wounds was significantly less than in WT wounds (P = 0·05 and P < 0·001, respectively). The PVV was significantly less in VEGF-A stimulated Matrigel plugs compared with FGF-2 stimulated plugs in NOS 2-/- mice (P < 0·01), but not in WT mice. CONCLUSIONS: NOS 2 is significantly involved in angiogenic signalling in healing skin wounds, particularly within the first 7 days. However, Matrigel plug vascularization suggests that the role of NOS 2 in angiogenesis is related to VEGF-A but not FGF-2 stimulated angiogenesis.

Vascularized tissue-engineered chambers promote survival and function of transplanted islets and improve glycemic control.

We have developed a chamber model of islet engraftment that optimizes islet survival by rapidly restoring islet-extracellular matrix relationships and vascularization. Our aim was to assess the ability of syngeneic adult islets seeded into blood vessel-containing chambers to correct streptozotocin-induced diabetes in mice. Approximately 350 syngeneic islets suspended in Matrigel extracellular matrix were inserted into chambers based on either the splenic or groin (epigastric) vascular beds, or, in the standard approach, injected under the renal capsule. Blood glucose was monitored weekly for 7 weeks, and an intraperitoneal glucose tolerance test performed at 6 weeks in the presence of the islet grafts. Relative to untreated diabetic animals, glycemic control significantly improved in all islet transplant groups, strongly correlating with islet counts in the graft (P<0.01), and with best results in the splenic chamber group. Glycemic control deteriorated after chambers were surgically removed at week 8. Immunohistochemistry revealed islets with abundant insulin content in grafts from all groups, but with significantly more islets in splenic chamber grafts than the other treatment groups (P<0.05). It is concluded that hyperglycemia in experimental type 1 diabetes can be effectively treated by islets seeded into a vascularized chamber functioning as a "pancreatic organoid."