(A) Representative Western blot analysis for BM eNOS. Diabetic mice demonstrated decreased phosphorylated eNOS compared with nondiabetic controls. Insulin failed to restore impaired eNOS phosphorylation. Quantification of phospho-eNOS (p-eNOS). Results are based on 4 experiments and show the amount of phospho-eNOS relative to total eNOS and β-actin. Nondiabetic controls are used as the standard (value set at 100). *P < 0.01. (B) Changes in cell composition in BM of diabetic mice. EPC (VEGFR2/CXCR4) and HSC (CD34/CD45) populations are unchanged, while mesenchymal stromal (CD73/CD44) and inflammatory cell (SSC/CD3/CD45RA) populations are slightly decreased in diabetic mice compared with nondiabetic mice. Percentages indicate positive cells in total BM cells counted. (C) Quantification of the number of Tie2⁺/VEGFR2⁺ EPCs/μl of peripheral blood in Tie2-GFP mice by flow cytometry at 7 days following STZ treatment. A substantial reduction in circulating EPCs was found in diabetic compared with nondiabetic mice. (D and E) NO production in the BM cavity of diabetic and nondiabetic mice during 10 minutes of HBO treatment. Baseline NO levels were obtained 5 minutes prior to onset of pressurization at 100% O₂ (gray bar). Solid lines represent mean values, with surrounding gray or black shading representing SEM. (D) Hyperoxia increases BM NO levels significantly, but the NO response is attenuated in diabetic mice compared with nondiabetic animals (P < 0.05). Insulin did not reverse the impairment of NO production. (E) Total iNOS and nNOS proteins were upregulated in diabetic mice. –, nondiabetic mice; +, diabetic mice. (F) Complete inhibition of BM NO production in diabetic and nondiabetic mice undergoing HBO treatment after pretreatment with l-NAME.