Tissue Preparation

Frozen tissue is typically mounted in OCT blocks following fixation and cryoprotection. For formalin-fixed tissue that will be embedded in paraffin blocks (FFPE tissue), we process the tissue through graded alcohols and xylenes for dehydration, followed by infiltration with paraffin wax. We use an automated tissue processor which handles large numbers of tissue samples and provides consistent processing. 

The dehydrated and paraffin-infiltrated tissues provided by our automated tissue processor are then embedded into paraffin blocks. We use a paraffin embedding station to properly orient the tissue in molds, and then fill the molds with paraffin wax with appropriate melting point and hardness to facilitate high quality tissue sectioning and subsequent staining.

We use digital microtomes for tissue sectioning. These highly accurate instruments allow for sectioning at a wide range of thicknesses. For FFPE tissue, we typically section at 5 µm thickness. We couple our microtomes with cooling/freezing stages. This strategy not only allows us to rapidly cut FFPE tissue, but also provides an excellent set-up for frozen tissue sectioning. We typically section frozen tissue at 20-30 µm thickness.