Tissue lithography: Microscale dewaxing to enable retrospective studies on formalin-fixed paraffin-embedded (FFPE) tissue sections

PLoS One. 2017 May 11;12(5):e0176691. doi: 10.1371/journal.pone.0176691. eCollection 2017.

Abstract

We present a new concept, termed tissue lithography (TL), and its implementation which enables retrospective studies on formalin-fixed paraffin-embedded tissue sections. Tissue lithography uses a microfluidic probe to remove microscale areas of the paraffin layer on formalin-fixed paraffin-embedded biopsy samples. Current practices in sample utilization for research and diagnostics require complete deparaffinization of the sample prior to molecular testing. This imposes strong limitations in terms of the number of tests as well as the time when they can be performed on a single sample. Microscale dewaxing lifts these constraints by permitting deprotection of a fraction of a tissue for testing while keeping the remaining of the sample intact for future analysis. After testing, the sample can be sent back to storage instead of being discarded, as is done in standard workflows. We achieve this microscale dewaxing by hydrodynamically confining nanoliter volumes of xylene on top of the sample with a probe head. We demonstrate micrometer-scale, chromogenic and fluorescence-based immunohistochemistry against multiple biomarkers (p53, CD45, HER2 and β-actin) on tonsil and breast tissue sections and microarrays. We achieve stain patterns as small as 100 μm × 50 μm as well as multiplexed immunostaining within a single tissue microarray core with a 20-fold time reduction for local dewaxing as compared to standard protocols. We also demonstrate a 10-fold reduction in the rehydration time, leading to lower processing times between different stains. We further show the potential of TL for retrospective studies by sequentially dewaxing and staining four individual cores within the same tissue microarray over four consecutive days. By combining tissue lithography with the concept of micro-immunohistochemistry, we implement each step of the IHC protocol-dewaxing, rehydration and staining-with the same microfluidic probe head. Tissue lithography brings a new level of versatility and flexibility in sample processing and budgeting in biobanks, which may alleviate current sample limitations for retrospective studies in biomarker discovery and drug screening.

MeSH terms

  • Convection
  • Fluorescence
  • Formaldehyde / chemistry*
  • Humans
  • Immunohistochemistry
  • Microfluidics / methods*
  • Paraffin Embedding*
  • Retrospective Studies
  • Staining and Labeling
  • Tissue Fixation*

Substances

  • Formaldehyde

Grants and funding

This work was supported by the European Research Council (ERC) Starting Grant, under the 7th Framework Program (Project No. 311122, BioProbe) (URL: http://www.bioprobe.eu/). IBM Research – Zurich provided support in the form of salaries for authors JFC, AK, AFK, and GVK, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.