Project Description and Rationale:
Amyotrophic Lateral Sclerosis (ALS) is the most common adult motor neuron disease, affecting 30,000 people in the US and the typical age of onset is in the mid-50s or slightly younger. ALS is a degenerative neural disease in which the damage and death of neurons results in progressive loss of the body’s functions until death, which is usually in 3-5 years of diagnosis. Current ALS treatments are primarily supportive, and providing excellent clinical care is essential for patients with ALS; however, there is an urgent need for treatments that significantly change the disease course. The only Food and Drug Administration approved, disease-specific medication for treatment of ALS is Rilutek (riluzole); which demonstrated only a modest effect on survival (up to 3 months) in clinical trials.
The ALS Disease Team/Early Translational project is focused on developing an ALS therapy based on human embryonic stem cell (ESC) derived neural stem cells (NSC) and/or astrocyte precursor cells transplanted into the ventral horn of the spinal cord. Several lines of evidence strongly support the approach of transplanting cells that exhibit the capacity to migrate, proliferate and mature into normal healthy astrocytes which can provide a neuroprotective effect for motor neurons and reduce or prevent neural damage and disease progression in ALS.
Year 2 Progress Summary:
The longer-term, larger-scale in vivo safety and efficacy studies using the lines that showed the most promise during previous screening studies (UCSF4 and ESI-017 NSCs) have been completed. The safety studies were performed in immunodeficient rats to evaluate the survival, migration, differentiation, function and tumorigenicity of implanted NSCs at 3 weeks, 2 months and 6 months post implant. The efficacy studies were conducted in a transgenic SOD1G93A ALS rat model to evaluate safety and cell fate in the background of disease, as well as, to evaluate disease-modifying activity (e.g. neural protection/proof-of-concept) of the implanted NSCs.
NOTE: A labeling error occurred during expansion and banking of the ESCs at UC Davis, and the cell line labeled as UCSFB7 (aka UCSF4.3) was determined by DNA fingerprinting to actually be ESI-017. Previous NSC generation, characterization and in vivo screening data was reported for cell line UCSFB7 (aka UCSF4.3), which was actually for ESI-017.
Both UCSF4 and ESI-017 NSCs were deemed acceptable in 2 out of 3 of the minimal acceptance criteria:
1) Long-term survival in nude and SOD1G93A rats
2) No formation of tumors or other unwanted structures when implanted into nude or SOD rats.
The third criterion: at least 10% greater α-motor neuron counts in cell-injected animals as compared to medium injected controls (or cell-injected side compared to the non-injected, or contralateral side) was not met due to a) variability of α-motor neuron counts and b) the aggressive nature of the current SOD1G93A rat ALS model and resulting very short 2 month treatment window which exceeds the length of time for the migration, expansion, differentiation and maturation of sufficient astrocytes to provide a neural protective effect in all implanted animals.
UCSF4 NSCs were originally selected as the developmental candidate, however, there are compelling reasons to reconsider ESI-017 NSCs: 1) UC Davis has found ESI-017 NSCs relatively easy to generate and is having difficulty generating UCSF4 NSCs; and 2) recent hisotological evaluations suggest that ESI-017 NSCs produce mature astrocytes earlier in vivo than UCSF4 NSCs. We are working with UC Davis on generation of UCSF4 NSCs and are quantifying astrocyte maturation histology (e.g. GFAP) to make a well-supported developmental candidate selection.
In parallel, mRNA sequencing has been performed 1) on cells produced in the course of this project to identify potential markers predictive of in vivo fate, 2) on naïve SOD1G93A rats to explore markers of disease onset and progression that could potentially be used as surrogate markers of disease modulation in place of motor neuron counts, and 3) on NSCs implanted into nude and SOD1G93A rats to identify potential markers of long-term post-transplant NSC cell fate and host response.