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Updated: Oct 9, 2026
Detection and Analysis of DNA Damage in Mouse Skeletal Muscle In Situ Using the TUNEL Method
Published on: December 16, 2014
False-positive apoptosis signal in mouse kidney and liver detected with TUNEL assay
K J Pulkkanen1, M O Laukkanen, J Naarala
1Department of Molecular Medicine, A.I.Virtanen Institute, Kuopio University Hospital, University of Kuopio, Finland.
Abstract:
Apoptosis is a physiological, programmed process for the elimination of cells from living organisms. Currently, one of the most frequently used methods to detect apoptosis is TUNEL assay. It has provided valuable information about apoptosis in various tissues. However, the sensitivity and the specificity of TUNEL technique have also been criticized. We detected an intense false-positive apoptotic signal in nude and Balb/c mice kidney and liver. In kidney the signal was confined to the proximal, distal and collecting tubular cells, and in liver to hepatocytes. Both tissues appeared normal in light microscopy, and no DNA ladder formation or increase in caspase-3 enzyme activity was detected. BrdU labelling and Ki-67 immunostaining did not reveal increased cell proliferation in these tissues. On the other hand, false-positive signal was not detected in testis, spleen, pancreas or renal cell carcinoma from the same animals. Also, no false-positive signal was seen in human liver or kidney samples. Although factors known to produce false-positive staining related to sample harvesting, preparation and staining protocols were eliminated, the cause of the false- positive apoptotic signal remains unknown. We conclude that caution must be exercised when examining apoptosis in mouse tissues with TUNEL assay.
Insights
The TUNEL assay, a common method for detecting apoptosis, can produce false-positive signals in mouse kidney and liver tissues. Researchers recommend caution when using this assay for apoptosis detection in mouse samples.
Area of Science:
- Cell Biology
- Histology
Background:
- Apoptosis is a critical physiological process for cell elimination.
- The Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay is widely used to detect apoptosis.
- Concerns exist regarding the sensitivity and specificity of the TUNEL assay.
Purpose of the Study:
- To investigate the reliability of the TUNEL assay in detecting apoptosis in mouse tissues.
- To identify potential sources of false-positive signals in TUNEL staining.
Main Methods:
- TUNEL assay was performed on kidney and liver tissues from nude and Balb/c mice.
- Histological examination, DNA laddering, caspase-3 activity assays, BrdU labeling, and Ki-67 immunostaining were utilized.
- TUNEL staining was also performed on testis, spleen, pancreas, renal cell carcinoma, and human liver/kidney samples.
Main Results:
- Intense false-positive apoptotic signals were observed in mouse kidney and liver tissues.
- These tissues showed no signs of DNA fragmentation, increased caspase-3 activity, or elevated cell proliferation.
- False-positive signals were absent in other tested mouse tissues and human samples.
- Standard protocols to eliminate known causes of false positives were followed.
Conclusions:
- The TUNEL assay can yield false-positive results in mouse kidney and liver tissues.
- The underlying cause of these false-positive signals remains undetermined.
- Careful interpretation is necessary when using the TUNEL assay for apoptosis assessment in mouse tissues.
