Hairless mice are laboratory animals known for their lack of fur. Their appearance, a smooth, pinkish skin, is a direct result of specific genetic alterations. They serve as valuable models in scientific investigations, offering insights into human health and disease.
Defining Hairless Mice
Their hairlessness primarily stems from spontaneous genetic mutations. Two common mutations are `nu` (for nude mice) and `hr` (for hairless or rhino mice). The `hr` gene, located on mouse chromosome 14, encodes a transcriptional co-repressor highly expressed in mammalian skin. Mutations in this gene lead to hairlessness in homozygous animals, characterized by hair loss after an initial cycle of relatively normal hair growth.
For instance, some hairless strains develop a normal coat for about 10 days before losing hair, starting from the head, until they become completely hairless by five weeks of age. This spontaneous recessive mutation of the hairless gene was identified and propagated in laboratory settings.
Applications in Research
Hairless mice are widely employed in scientific research due to their distinct biological features. Their lack of fur simplifies the application of topical agents and allows for easy visualization of cutaneous responses, which is beneficial for dermatological studies. For example, studies on wound healing, acute photobiological responses, and skin carcinogenesis are extensively conducted using strains like SKH1 hairless mice, an outbred, unpigmented, and immunocompetent variety.
Certain hairless strains, such as nude mice, possess compromised immune systems due to the `nu` mutation, which affects the development of the thymus gland and, consequently, T-cell production. This immunodeficiency makes them ideal for immunology research, particularly in studies involving transplantation where immune rejection is a factor. In cancer research, hairless mice are frequently used as xenograft models, allowing researchers to implant human tumor cells and study tumor growth and the efficacy of new therapies without the mouse’s immune system rejecting the foreign cells. The ease of observing tumors on their hairless skin also contributes to their utility in these studies.
Unique Physiological Characteristics
The absence of fur leads to distinct physiological consequences impacting their well-being and care. One significant challenge is thermoregulation, as fur provides insulation that helps maintain body temperature. Without this natural insulation, hairless mice have difficulty retaining body heat and are more susceptible to cold stress, requiring warmer ambient temperatures in their housing.
Their exposed skin also makes them more prone to dehydration and increases their susceptibility to skin infections or irritation. The skin of some hairless strains, like the FVB hairless mouse, can develop hyperkeratosis, a thickening of the outermost layer of the skin, and may show cyst formation, dilated sebaceous gland ducts, and dermal inflammation. These unique characteristics necessitate specialized care protocols in laboratory settings, including careful monitoring of environmental conditions and skin health, to ensure their welfare and the reliability of research outcomes.