In situ hybridization demonstration of albumin mRNA in B6C3F1 murine liver and hepatocellular neoplasms

A fast and efficient polymerase chain reaction-based method for the preparation of in situ hybridization probes

AIMS

In situ hybridization (ISH) is the method of choice for analysis of the local distribution of gene expression in tissue samples at the cellular level. In this study we present a rapid and efficient protocol for the generation of labelled cRNA probes.

METHODS AND RESULTS

The protocol is based on the preparation of DNA in vitro transcription templates using polymerase chain reaction (PCR), using primers that include RNA polymerase promoter sequences and size-based purification of PCR fragments containing the target gene-specific cDNA and promoter elements for T7 and SP6 RNA polymerase. The optimized purification protocols ensure high transcription efficiency and target specificity of the labelled cRNA. The cRNA hybridization probes obtained are compatible with established in situ hybridization protocols.

CONCLUSIONS

Purified PCR fragment-based in vitro transcription enables preparation of in situ hybridization probes which allow the rapid detection of gene expression distribution in tissue slices from any gene of interest.

Expression of surfactant protein mRNA in normal and neoplastic lung of B6C3F1 mice as demonstrated by in situ hybridization

The localization of surfactant protein (SP), A, B, C, and D mRNAs was examined in B6C3F1 mice in the normal lung, and in a range of spontaneous proliferative lung lesions using nonisotopic in situ hybridization (ISH). The aim was to develop diagnostic markers, and if possible, throw further light on the histogenesis of these lesions. Tissues from 21 animals were examined, the lesions studied were: 4 alveolar epithelial hyperplasias, 12 alveolar/bronchiolar (A/B) adenomas, and 5 A/B carcinomas. Lung metastases of hepatocellular carcinoma (HCC) were used as controls. In the nonneoplastic lung, staining for SP A, B, and C mRNA was observed in normal and hyperplastic type II cells but not in the bronchiolar epithelium. SP mRNAs were present in all lung tumors, with SPs A, B, and C being coexpressed in 10/12 (83%) of adenomas and 4/ 5 (80%) of carcinomas in both solid and tubulopapillary areas. No signals for SP D mRNA were noted in normal or neoplastic lung. Additionally, no staining for any SP transcript was observed in the HCC metastases examined. In summary, ISH for SP A, B, or C mRNA was a helpful aid in the diagnosis of proliferative lesions of the murine lung, enabling differentiation from hepatocellular metastases. Furthermore, this work provides strong support for the proposal that spontaneous lung tumors in B6C3F1 mice are of alveolar, not bronchiolar origin, and consistently show type II cell differentiation. We suggest that such tumors should be referred to as alveolar adenomas and carcinomas.