Frozen sections at 6 μm were stained with a protocol established in our laboratory.44 (link), 45 (link) Images were captured using a Zeiss 710 Meta Confocal Laser Scanning Microscope and analyzed using the Zeiss Zen 2010 software (Carl Zeiss Microscopy, LLC, Thornwood, NY). TUNEL assay was performed using TUNEL Apoptosis Detection kit (EMD Millipore, inc. Darmstadt, Germany) to determine cell apoptosis.