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Updated: Jun 24, 2026
MicroRNA Amplification and Recognition through Locked-nucleic-acid In situ Hybridization as a Novel Detection and Quantification Method
Published on: October 7, 2025
In situ detection of mature microRNAs by labeled extension on ultramer templates
Gerard Nuovo1, Eun Joo Lee, Sean Lawler
1Department of Pathology, Ohio State University Medical Center, Columbus, OH 43210, USA. gnuovomd@pol.net
Abstract:
We describe a new method for the in situ detection of a mature microRNA (miRNA) in formalin-fixed, paraffin-embedded tissues. The method involves the labeled extension of miRNA hybridized to an approximately 100-nucleotide-long ultramer template containing the complementary sequence of the miRNA at its 3' terminus. Pretreatment of the tissue involves incubation with protease to expose the genomic DNA to DNase digestion, thereby eliminating the ultramer-independent DNA synthesis process inherent in paraffin-embedded tissue. By direct comparison with real-time reverse transcriptase (RT)-PCR, RT in situ PCR, and standard in situ hybridization using a locked nucleic acid (LNA) probe, it was evident that the ultramer extension method detects only the mature miRNA, is easier to optimize, results generally in a stronger signal, and is much less expensive than the LNA probe method currently used.
Insights
This study introduces a novel ultramer extension method for detecting mature microRNA (miRNA) in fixed tissues. This technique offers a simpler, more sensitive, and cost-effective alternative to current methods for miRNA detection.
Area of Science:
- Molecular Biology
- Biotechnology
- Histology
Background:
- Accurate detection of mature microRNA (miRNA) in formalin-fixed, paraffin-embedded (FFPE) tissues is crucial for research and diagnostics.
- Current in situ hybridization methods, such as those using locked nucleic acid (LNA) probes, can be complex, expensive, and may lack specificity.
Purpose of the Study:
- To develop and validate a novel, cost-effective, and highly sensitive method for the in situ detection of mature miRNA in FFPE tissues.
- To compare the performance of the new method against established techniques like RT-PCR and LNA probe-based in situ hybridization.
Main Methods:
- A new ultramer extension method was developed, involving a labeled 100-nucleotide ultramer template complementary to the target miRNA.
- Tissue pretreatment included protease incubation followed by DNase digestion to eliminate non-specific DNA synthesis.
- The method was validated by direct comparison with real-time reverse transcriptase (RT)-PCR, RT in situ PCR, and LNA probe in situ hybridization.
Main Results:
- The ultramer extension method specifically detects mature miRNA, distinguishing it from precursor forms.
- The new method demonstrated superior ease of optimization and generally produced stronger signals compared to LNA probes.
- Cost analysis revealed the ultramer extension method to be significantly less expensive than the LNA probe method.
Conclusions:
- The ultramer extension method provides a sensitive, specific, and economical approach for mature miRNA detection in FFPE tissues.
- This technique offers a valuable alternative for researchers and clinicians working with archival tissue samples.
- The method's simplicity and effectiveness make it suitable for widespread adoption in molecular pathology and miRNA research.
