Research Article

The Unusual Circulation of the Newt Heart after Ventricular Injury and Its Implications for Regeneration

Figure 4

Regeneration after needle puncture. (a) Chondrogenesis is shown based on toluidine blue staining. (b) New vessels are shown by CD31 immunohistological staining. (c) Formation of a fistula (toluidine blue). (d) There is loss of cardiomyocytes after needle puncture (trichrome stain). (e) Regenerating cardiomyocytes 7 days after needle puncture. Note that the epicardial layer where regeneration starts is significantly thickened (box 1, HE stain) compared with areas where there is no regeneration (box 2, HE stain). (f) Regenerating cardiomyocytes 14 days after needle puncture. The rectangular box shows regenerating cardiomyocytes. (g) Panel 1 is a magnification of the rectangular space-1 in (e). The red arrows indicate the blood vessels (trichrome stain). Immunohistological analysis showed that CD31 is expressed in the tip of the epicardial bud (panel 2). Cardiomyocyte regeneration required more time in the endocardial layer (panel 3, HE stain). Magnification: ((d), (e) and (f)) × 40; ((a), (b), (c) and (all panels of g)) × 100.