Reporting of Mammary Tumours in Indigenously developed Spontaneous NIN/Sprague Dawley Mutant (Nude) Rat Strain

Abstract Background: Breast cancer has been linked with many causes including nutrition. However spontaneous mammary tumour rodent model will unlock many such mechanisms. The past five decades, the ICMR-NIN animal facility has diligently maintained a colony of Sprague Dawley rats. Around a decade ago, a spontaneous mutation emerged within this colony. This mutation, rather than being discarded, was intentionally nurtured to comprehend its phenotype and its potential utility as a research model. This manuscript is dedicated to presenting significant insights into its immunological and histological characteristics. Materials and Methods: Selective breeding of nude rats (SD/NIN hr−/− animals) was carried out by maintaining and crossing them with both their heterozygous phenotype (SD/NIN hr+/− ) and homozygous phenotype (SD/NIN hr−/− ). Throughout their entire life cycles, these animals were closely monitored for any development of abnormalities or distinctive traits. The spontaneous development of tumours was recorded under close observation of 24 animals to detect the extent of tumours. Apart from routine body composition, animals were evaluated for their serum biochemistry and CD 4/8 profile. Results and Discussion: No significant alterations were observed in the vital organs when compared to the heterozygous animals. Nevertheless, both the homozygous (nude) animals and the heterozygous rats exhibited the spontaneous development of fibroadenomas in the mammary glands during the adult stage, as opposed to the parent colony of NIN/SD rat. Interestingly, the biochemical and T/B cell profiles displayed no correlation with the presence of these tumours. The tumour presented histological pattern similar to mammary tumour in human. Conclusion: This unique hairless SD rat model has the capacity to be a suitable choice for research focused on cancer, particularly in the area of mammary tumours. It possesses an immunocompetent nature, mirroring real-life human scenarios, and it has been developed locally, adding to its distinct advantages.