【Zhonghong Boyuan】-Immune Deficiency Animal Model--Nude Mouse
中洪博元,裸鼠,动物模型
z-bo
2020-07-23
572
In the field of medical and biological research, especially in the safety assessment of tumors, immunity, drugs, biologics, and preclinical screening of effective drugs, NudeMouse ("naked mice") has always been an indispensable experimental animal. Being a role model plays an important role in other ways.
Nude mice were born in the early 1960s and were first discovered by Dr. Grist of the Institute of Virology, Ruchel Hospital, Glasgow, England in the albino population (close relatives). Information about this mutant mouse was published in Mouseewsletter in 1962. Obviously, Dr. Gris was not very interested in this kind of nude mouse, nor did he conduct an in-depth analysis of him. Four years later, Flanagan of the Edinburgh Institute of Animal Genetics obtained three nude mice from Grist and analyzed their genetic and biological characteristics. One hairless individual (male) of the three nude mice had no offspring before death. After mating, two other mice with coats (one male and one male) produced two of the 23 offspring. After crossing and using these offsprings of flanmann, hairless individuals appear in one offspring of the pair. Separate the data based on the characteristics of the offspring, and the parents determine that the parents are heterozygous. Flanagan used a pair of heterozygotes and their offspring to establish a population of nude mice, named the mutant gene "naked", abbreviated as nu. Flanagan found that female nude mice had a very low fertilization rate. After 46 female nude mice were paired with normal coated male mice, only 4 pairs became pregnant, and the female nude mice could not be fertilized due to poor breast development and lack of milk. done. Raise offspring. Flanagan also studied the growth of nude mice, hair development, and the connection between the nu gene and known mutant genes, and published the results in 1966. Unfortunately, he did not discover the most important feature of athymic glands in nude mice. Before the emergence of nude mice, drugs were usually used to inhibit the production of mouse T cells or surgically removed the thymus for cellular immunological research. As early as 1944, scientists discovered that removing the thymus of AKR (hyperleukemia) mice as early as possible can reduce the risk of leukemia in mice. Removal of C58 mouse thymus can prevent chemical or radiation leukemia. After thymectomy, not only the circulating lymphocytes decrease, but also the production of antibodies. These findings indicate that the thymus plays a key role in the immune response, making thymectomy a routine method for preparing immunodeficiency animal models. However, thymectomy has fatal disadvantages. This is because young animals died within 1-3 weeks after thymectomy infection and eating, or the experiment failed due to incomplete thymectomy. At the same time, the modeling process inevitably brings pain to experimental animals.
Further analysis by Petty Lewis found that the white blood cell count in nude mice was significantly lower than that in normal mice, only one-fourth of that of wild-type mice in the same litter. Since nude mice have no thymus, they are expected to replace thymectomized mice and become animal models of congenital immunodeficiency. This is a discovery that is much more important than the naked phenotype, so it attracted the attention of the scientific community shortly after reporting the work of petty bourgeois Lewis. But before nude mice can become widely available animal models, they need to improve their reproductive capacity and survivability. Flanagan found that when analyzing the biological characteristics of nude mice, the growth rate of homozygous nude mice was 30% slower than that of wild or heterozygous nests. In addition, nude mice have small ovaries, lack of corpus luteum, poor sperm motility, and curled tails, indicating that there are problems with the fertility of nude mice. At the same time, the survival rate of nude mice is also a big problem. In the 1960s, there were no animal husbandry facilities without SPF, and it was impossible to control the contamination of various pathogenic microorganisms in animal populations. The immunodeficiency of nude mice prevents them from resisting these pathogens. Therefore, when nude mice were first discovered, more than half of the people died at 2 weeks of age, and only 10% of the animals were able to live to 12 weeks. If the above problems are not resolved, nude mice cannot truly become a viable animal model. By putting
Nude mice mate with other mice. We hope to screen and establish highly prolific strains carrying nu genes. The research was first conducted by pathologists Regard and Povison of the Danish Institute of Pathology and Anatomy at the Root Harco Institute. Interestingly, we conducted experiments to verify the "tumor immune surveillance theory" proposed at that time. To this end, they crossed nude mice obtained from the Edinburgh Institute of Animal Genetics with pure BALB/c, C3H and C57BL/6 mice, and obtained three newly inbred inbred nude mouse species. Continue to choose and multiply. This work was completed between 1969 and 1972. Introducing nu genes into inbred mice with different genetic backgrounds can improve the biological characteristics of nude mice, but cannot overcome the problems of low fertility and short survival time. .. It was not until 1974 that the NIH Hansen team introduced the nu gene of the BALB/c background strain into the SwissNIH inbred line. After the establishment of nude mice inbred lines, their fecundity and disease resistance have been significantly improved. Female and male mice homozygous for u and nu are used for mating and reproduction. After the introduction of the SPF feeding system, the chance of nude mice being infected by pathogenic microorganisms is greatly reduced, and the life span of nude mice has been extended to a level similar to that of conventional inbred mice.
▲ 25-day-old NMR Inu/nu mice (right) and Zayin's nest (left). The u/nu mouse is small and uncoated, but has a sparse beard (as shown by the arrow and illustration). By 1996, a mutant gene that determines the phenotype of nude mice was also discovered. This is due to a point mutation in the Foxn1 gene, which leads to the early termination of the encoded protein and the formation of a truncated, non-functional protein Foxn1nu. Obviously, the Foxn1 gene is pleiotropic, which will affect the hair and thymus development of mice. Nudity is caused by the inability of the hair shaft of the hair follicle to grow from the epidermis of individuals carrying the homozygous Foxn1nu. Nudity is a phenotype that is easy to observe and detect, but it is rarely related to immunodeficiency. Flanagan systematically analyzed the biological characteristics of nude mice, but missed the important feature of nude mice thymus hypoplasia. Seven years after the mutation appeared in nude mice, Pettilise was lucky to discover this important biological characteristic. We are fortunate to be able to maintain this mutation under the conditions of storage and reproduction at the time, as well as in nude mice with low fertility and low survival. In the absence of athymic glands, nude mice may quickly disappear from the scientists' sight. Although the naked phenotype is very clear, the discovery of abnormal thymus development requires the attention of the observer and little luck, which is the attraction of scientific research.
