TUNEL Staining: Identifying Apoptotic Cells via DNA Fragmentation

Overview

TUNEL staining (Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling) is a widely used method for detecting apoptosis by labeling DNA strand breaks in tissue sections. This technique provides direct evidence of cell death due to programmed apoptosis, as opposed to necrosis or mechanical damage.

At iHisto, our optimized TUNEL staining service offers clear, accurate identification of apoptotic nuclei in FFPE or frozen tissue samples — enabling researchers to quantify cell death across organs, models, and treatment groups.

TUNEL is commonly used in toxicology, neuroscience, cancer research, and drug efficacy studies.

How TUNEL Staining Works

The TUNEL assay uses the enzyme TdT (Terminal deoxynucleotidyl transferase) to add labeled nucleotides to the exposed 3’-OH ends of fragmented DNA. These labeled nucleotides are then detected using chromogenic or fluorescent methods.

Detection Formats:

• Chromogenic TUNEL: Produces a brown or red nuclear signal (e.g., DAB, Fast Red)

• Fluorescent TUNEL: Emits green, red, or far-red signals depending on the dye used

Color Results (Chromogenic):

• Apoptotic nuclei: Brown or red depending on substrate

• Background tissue: Clear or counterstained blue (hematoxylin)

Step-by-Step TUNEL Staining Process

1. Fixation and Sectioning
   FFPE or frozen tissue is prepared and mounted on positively charged slides.

2. Permeabilization
   Proteinase K or detergent treatment allows enzyme access to DNA.

3. TdT Reaction
   Terminal transferase adds labeled nucleotides to DNA breaks.

4. Detection
   Signal is visualized using either chromogen (e.g., DAB) or fluorescence.

5. Counterstaining
   Hematoxylin or DAPI enhances nuclear contrast and visualization.

6. Mounting
   Slides are coverslipped using aqueous or resin media depending on the detection method.

Our Optimized Workflow

iHisto performs TUNEL staining using commercial kits (e.g., Roche, Promega, Abcam) and proprietary optimization steps to ensure:

• ✅ Low background signal

• ✅ High sensitivity to DNA fragmentation

• ✅ Compatibility with a wide range of tissues

• ✅ Both chromogenic and fluorescent detection options

• ✅ Optional dual labeling with IHC or IF markers

We offer flexible TUNEL protocols for standard apoptosis screening or advanced multiplex detection.

Applications of TUNEL Staining

TUNEL staining is used to detect and quantify apoptotic cell death in both normal and pathological conditions.

Common use cases:

• Neurodegeneration models (e.g., Alzheimer’s, Parkinson’s)

• Oncology – Evaluating treatment-induced apoptosis

• Cardiotoxicity or hepatotoxicity studies

• Developmental biology and tissue remodeling

• Preclinical drug efficacy and safety testing

Whether you're studying targeted therapy, organ toxicity, or cell clearance, TUNEL provides sensitive apoptosis detection.

Advantages of iHisto’s TUNEL Staining Services

• ✅ High-sensitivity apoptosis labeling

• ✅ Chromogenic and fluorescent detection formats

• ✅ Works with human, rodent, NHP, and xenograft tissue

• ✅ Optional dual-staining with IHC or IF

• ✅ Digitized slide delivery and cell quantification available

Our experienced histology team ensures reliable TUNEL staining for single-sample studies or full-scale toxicologic programs.

FAQs

• What does TUNEL staining detect?
  It detects DNA fragmentation, a hallmark of apoptosis, by labeling free 3’-OH ends of broken DNA strands.

• Is TUNEL staining the same as cell death?
  It detects apoptotic cell death, not necrosis. Combined markers may be used to distinguish between death types.

• Can TUNEL be combined with IHC?
  Yes. We can perform dual-staining (e.g., TUNEL + NeuN, TUNEL + CD3) to co-label apoptotic and phenotypic markers.

• Do you offer digital analysis of apoptotic cells?
  Absolutely. We provide slide scanning and can perform automated or manual apoptosis counts upon request.

Ready to Visualize Apoptosis Accurately?

At iHisto, we offer high-quality TUNEL staining services with flexible formats, rapid turnaround, and expert support. Whether you're investigating neurotoxicity, drug efficacy, or tumor regression, we help you detect apoptosis clearly and confidently.

📩 Contact us to request a quote or consultation.