The formalin fixed samples were paraffin embedded and sectioned (5 μm thickness). The tissue orientation resulted in a radial cross section of the scaffold allowing for clear identification of the biomaterial-tissue interface. Sections were stained for hematoxylin and eosin (H&E) and Masson’s trichrome for examination of tissue structure and inflammation. Immunostains for CD31 were performed to identify blood vessels as described previously.[38 (link)] Briefly, slides were deparaffinized and rehydrated by a washing with a series of xylene and ethanol washes. Rehydrated slides underwent antigen retrieval using Dako target retrieval solution. Slides were incubated with rabbit anti-human CD31 (Santa Cruz Biotechnology, Santa Cruz, CA) and kept overnight, followed by staining with anti-rabbit secondary antibody using Vectastain Elite ABC Kit (Vector Labs, Burlingame, CA). Sections were imaged using an Axiovert 200 inverted microscope (20x objective, 0.27 μm/pixel). Vessels stained positive for CD31 were manually counted using Axiovision AC (Carl Zeiss, Germany). Blood vessel density was calculated using the following formula: vessel density = (number of CD31 stained vessels)/(tissue area).