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Factors affecting the yield of microRNAs from laser microdissectates of formalin-fixed tissue sections

ABSTRACT: Sixth generation Exiqon® locked nucleic acid miRCURY™ LNA microarrays were used to profile in duplicate the expression of microRNAs in 250 or 400 ng of RNA isolated from a laser microdissectate of a formalin-fixed and paraffin-embedded human non-small cell lung cancer tumor. Laser microdissection was performed on a hematoxylin-eosin-stained, 8 um-thick section of formalin-fixed and paraffin-embedded tissue. The microdissectate was treated with proteinase K overnight at 55 ºC. Total RNA from the lysate was then extracted using FFPE RNA Isolation Kit from Norgen Biotek® (Thorold, Canada). RiboGreen assay was used to quantify RNA in the preparation. Two-hundred-fifty or 400 ng of RNA was used in duplicate for dual-channel microarray-based microRNA expression profiling. Sample RNA was labeled with the Cy3-like Hy3™ dye, mixed with a human universal reference RNA (product number AM6000, Ambion®, Austin, TX) labeled with the Cy5-like Hy5™ dye, and hybridized to the two-color miRCURY™ arrays.

ORGANISM(S): Homo sapiens

SUBMITTER: Patnaik Santosh

PROVIDER: S-ECPF-GEOD-31946 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description: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.

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Factors affecting the yield of microRNAs from laser microdissectates of formalin-fixed tissue sections

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