RESUMEN
Amyotrophic lateral sclerosis (ALS) still depicts an incurable and devastating disease. Drug development efforts are mostly based on superoxide dismutase 1 gene (SOD1)-G93A mice that present a very strong and early phenotype, allowing only a short time window for intervention. An alternative mouse model is available, that is based on the same founder line but has a reduced SOD1-G93A copy number, resulting in a weaker and delayed phenotype. To be able to use these SOD1-G93A/low mice for drug testing, we performed a characterization of ALS-typical pathologies. All analyses were performed compared to non-transgenic (ntg) littermates of the same sex and age. In vivo analysis of SOD1-G93A/low mice was performed by weekly body weight measurements, analysis of the survival rate, and measurement of the muscle strength of 24-30 weeks old female and male SOD1-G93A/low mice. Immunofluorescent labeling of SOD1, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba1) protein was performed in the cervical, thoracic, and lumbar ventral horn of the spinal cord of 24-30 weeks old male and female SOD1-G93A/low mice. The musculus gastrocnemius of male SOD1-G93A/low mice was labeled with fluorophore-conjugated α-bungarotoxin and antibodies against phosphorylated neurofilaments. Fluorescent labeling was detected and quantified by macro-based image analysis. Although SOD1 protein levels were highly increased in both sexes and all age groups, levels strongly peaked in 30 weeks old male SOD1-G93A/low mice. Astrocytosis and activated microglia in the spinal cord ventral horn and phosphorylated neurofilaments in the motor unit of the musculus gastrocnemius progressively increased, while muscle strength progressively decreased in male SOD1-G93A/low mice. In female SOD1-G93A/low mice, only activated microglia increased progressively, while muscle strength was constantly reduced starting at 26 weeks. These differences result in a shorter survival time of male SOD1-G93A/low mice of about 3 weeks compared to female animals. The results suggest that male SOD1-G93A/low mice present a stronger pathology and are, therefore, better suitable to evaluate the efficacy of new drugs against ALS as most pathological features are developing progressively paralleled by a survival time that allows treatment to start before symptom onset.
RESUMEN
Huntington's disease is known to be a purely genetic disease based on an expansion of a CAG base triplet repeat in the coding region of the Huntingtin gene. Some years ago, researchers were able to introduce the extensive full-length gene sequence of the mutant huntingtin gene into a rodent model. The resulting BACHD rat is already well characterized for behavioral deficits. So far, all analyses in this preclinical rat model were performed in male hemizygous animals. As homozygosity of transgenic models often causes an amplification of the phenotype and female HD patients present a stronger phenotype compared to men, we established a homozygous breeding colony and tested 2 and 5 months old homozygous male and female BACHD rats in a behavioral test battery. The tests included the grip strength test, Rota Rod, elevated plus maze, passive avoidance, and Barnes maze test. Our results show strong deficits in young female homozygous BACHD rats including increased body weight, motor deficits, muscle weakness, reduced anxiety and hypoactivity, as well as learning and memory deficits. Analysis of male homozygous BACHD rats showed only weak disease symptoms, similar compared to male hemizygous BACHD rats of already published studies. Evaluation of the breeding success showed that homozygous BACHD have a reduced number of pups at the time of birth that even decreases until weaning. Our results suggest that the phenotype of homozygous male BACHD rats barely differs from already published results of hemizygous BACHD rats while female homozygous BACHD rats display strong and early alterations.