Ldlr KO (em) Mice

The Ldlr gene is located on mouse chromosome 9, and exon 4 of the gene was selected as the target region for gene editing.

The Ldlr KO mice can be used in research on atherosclerosis, macular tumor and coronary artery disease, familial hypercholesterolemia (FHCL1), and other metabolic and cardiovascular diseases, and screening of vasodilator drugs.

1. Protein expression

Figure 1. Detection of LDLR protein in the liver of Ldlr KO(em) and wild-type (WT) mice. Western Blot results show that there is no expression of LDLR protein in the liver of Ldlr KO(em) mice.

2. The growth curve

Figure 2. Detection of body weight in male wild-type and Ldlr KO (em) mice. Mice were grouped and given different diets, and their body weights in male wild-type mice (WT-M) and male Ldlr KO mice (LDLR-/--M) were measured weekly under common and high-fat diets. The results showed similar trends in body weight between male Ldlr KO mice and male wild-type mice under a common diet (CD) and high-fat diet (HFD) similar trends with no significant differences.

3. The growth curve

Figure 3. Detection of body weight in female wild-type and Ldlr KO (em) mice. Mice were grouped and given different diets, and their body weights in female wild-type mice (WT-F) and female Ldlr KO mice (LDLR-/--F) were measured weekly under a common diet and high-fat diet. The results showed similar trends in body weight between female Ldlr KO mice and female wild-type mice under a common diet (CD) and high-fat diet (HFD) with no significant differences.

4. Biochemical indexes of blood lipids in male mice

Figure 4. Biochemical indexes of blood lipids in male wild-type and male Ldlr KO (em) mice. Mice were grouped and given different diets, and lipid metabolism indexes were measured at the 6^th, 8^th, 12^th, 16^th, and 20^th weeks of feeding. The results showed that compared to male wild-type mice (WT-M), male Ldlr KO mice (LDLR-/--M) showed a slight increase in lipid levels under a common diet, while Ldlr KO mice were significantly elevated in all lipid indexes under high-fat diet (HFD). (CHOL: cholesterol; TRIG: triglycerides; HDL: high-density lipoprotein; LDL: low-density lipoprotein. The same as below.）

5. Biochemical indexes of blood lipids in female mice

Figure 5. Biochemical indexes of blood lipids in female wild-type and female Ldlr KO (em) mice. Mice were grouped and given different diets, and lipid metabolism indexes were measured at the 6^th, 8^th, 12^th, 16^th, and 20^th weeks of feeding. The results showed that compared to female wild-type mice (WT-F), female Ldlr KO mice (LDLR-/--F) showed a slight increase in lipid levels under a common diet, while Ldlr KO mice were significantly elevated in all lipid indexes under high-fat diet (HFD). The results of this assay were identical to those of male Ldlr KO mice, indicating that a hyperlipidemic phenotype can occur in Ldlr KO mice of both sexes under a high-fat diet.

6. Aortic pathology

Figure 6. Detection of aortic plaque formation in wild-type mice and Ldlr KO (em) mice. Mice were grouped and given different diets and aortas were taken for observation at the 16th week of feeding. Compared with other control groups, both male Ldlr KO mice in the G7 HFD and female Ldlr KO mice in the G8 HFD developed pathological plaques in the aorta, indicating that a high-fat diet can successfully induce the development of atherosclerosis in Ldlr KO mice. (G1: male WT mice + common diet; G2: female WT mice + common diet; G3: male WT mice + high-fat diet; G4: female WT mice + high-fat diet; G5: male Ldlr KO mice + common diet; G6: female Ldlr KO mice + common diet; G7: male Ldlr KO mice + high-fat diet; G8: female Ldlr KO mice + high-fat diet. Same as below.)

7. Progression of aortic plaque formation in Ldlr KO (em) mice

Figure 7. Detection of aortic plaque pathological process in Ldlr KO (em) mice. The observations of aortic plaque at different periods showed that aortic plaque formation was more pronounced in Ldlr KO mice fed high-fat for 20 weeks compared to mice fed high-fat for 16 weeks, and their plaque formation was further expanded. These changes were consistent with the trend in male and female mice.

8. Oil red O staining of the aortic arch in Ldlr KO (em) mice

Figure 8. Pathologic sections of the aorta in Ldlr KO (em) mice. Mice were grouped and given different diets and aortas were taken for observation at the 20th week of feeding. Compared with other control groups, both male Ldlr KO mice in the G7 HFD and female Ldlr KO mice in the G8 HFD had thickening of the inner wall of the aorta, and lipid attachment occurred at the thickening part, indicating that a high-fat diet can successfully induce the development of atherosclerosis in Ldlr KO mice.

9. Summary

Ldlr KO mice were constructed by knockout of the Ldlr gene and induced hypercholesterolemia by high-fat diet feeding. The results showed that the model was characterized by hyperlipidemia and hypercholesterolemia, and the levels of blood lipid indexes such as CHOL, TRLG, LDL, and HDL of Ldlr KO mice were significantly increased after high-fat diet feeding compared with control mice. Ldlr KO (em) mice had thickening of the inner wall of the aorta and lipid attachment. Also, aortic plaque formation was present in this model after high-fat diet feeding, and the size and distribution of pathological plaques increased with the increase of high-fat feeding time.

In summary, Ldlr KO (em) mice can be used for the model of hypercholesterolemia, providing a strong and effective tool for the construction of the model of cardiovascular metabolic diseases and the study of related human diseases.

• Temperature: 20-26°C
• Humidity: 40%-70%
• Bedding: Change high-pressure sterilized bedding weekly.
• Normal Chow Diet: Standard Maintenance Diet (Jiangsu Xietong Pharmaceutical Bio-engineering, catalog number: SWC9101).
• High-fat Diet: HFD Diet (R&D, catalog number: D12109C; Medicience, catalog number: MD12017).
• Recommended Modeling Period: Start high-fat feeding from 5-8 weeks of age. After one week of adaptive feeding with a high-fat diet (as shown in Table 1), switch to full high-fat and high-cholesterol diet. After 6 weeks of high-fat feeding, hyperlipidemia and hypercholesterolemia phenotypes can be observed. After 16 weeks of induction, aortic atherosclerotic lesions can be detected.

Table 1: Adaptive feeding conditions for a high-fat diet