Enzyme Digestion
Collagenase (150 U/ml) and hyaluronidase (100 U/ml) (Sigma Aldrich) were
added to the homogenized tissue to break up the extracellular matrix. The mixturewas incubated overnight at 37°C with shaking. The particle-spiked tissue was then sonicated using an Ultrasonic Processor (Cole-Parmer, Vernon Hills, Illinois) for20 seconds (2 sec bursts). To further break down the proteins we incubated the tissue with 200 μg/ml Proteinase K (Sigma Aldrich) in 0.5% SDS for 2 hrs at 65°C.