Figure 4. DKK2 promotes angiogenesis and improves tissue recovery in animal models of hind limb ischemia and MI.

(A and B) Intramuscular injection of DKK2 increased blood perfusion and reduced the probability of necrosis in the ischemic hind limb in mice. Tissue perfusion rate (%/min) was defined as the fraction of blood exchanged per minute in the vascular volume by time-series analysis of indocyanine green dye. Blood perfusion rate of the hind limb was measured at postoperative day 0 (POD 0). Correlation between regional perfusion rates of the ischemic hind limbs at POD 0 and limb necrosis levels at POD 3 was determined. The x axis shows the regional perfusion rate of the ischemic hind limbs (poor perfusion rate: 0%~30%/min; moderate perfusion rate: 30%~100%/min; good perfusion rate: 100 < %/min). Normal hind limbs typically demonstrate a perfusion rate above 400%/min. (C–J) Increase of myocardial repair after DKK2 injection. Myocardial injection of DKK2 decreased the LV infarct size as assessed by TTC staining at 1 week after MI (C and D). Representative images taken from a Masson’s trichrome–stained section (muscle is stained red, collagen is stained blue) (E and F). Microvessel staining with CD31 (G) and the TUNEL assay (I) on cardiac muscle tissues. Scale bars: 50 μm. Quantitative analysis of microvessel density and the TUNEL assay (H and J). Area with yellow broken lines (C) indicates the infarct region. Red arrows (G and I) indicate microvessels and apoptotic cells, respectively. (K) Effective improvement of cardiac function by DKK2 injection. Cardiac functions were measured with 2D conventional parameters: FS and LVEF at 3 weeks after injection of DKK2 into MI rats. FS (%) = ([LVEDD – LVESD]/LVEDD) × 100 (%). LVEDV = 7.0 × LVEDD3/(2.4 + LVEDD), LVESV = 7.0 × LVESD3/(2.4 + LVESD), and LVEF (%) = (LVEDV – LVESV)/LVEDV × 100. *P < 0.05; **P < 0.01; ***P < 0.001. S; Sham, V; VEGF, D2; DKK2. Data represent mean ± SD.