Human SERPINA1 mRNA

Alpha-1-antitrypsin (AAT) deficiency is a genetic disease resulting in inactivation/deficiency of AAT due to mutations in the SERPINA1 gene encoding AAT. The disease is associated with reduced AAT activity in the lungs and excess deposition of defective AAT protein in the liver. AAT lung disease is often treated with one of a number of serum protein replacements. However, there are no long-term studies on the effectiveness of SerpinA1 replacement therapy, and the therapy has not been shown to reduce liver damage in patients with AAT deficiency. mRNA therapy may act on both the liver and lungs of patients with AAT deficiency. mRNA encoding SERPINA1 was transfected into AAT patient fibroblasts and AAT patient fibroblast-derived hepatocytes, and SerpinA1 expression in the cell culture medium was measured. The data showed that the culture medium of treated AAT patient fibroblasts and AAT patient fibroblast-derived hepatocytes had increased levels of SerpinA1 protein. In vivo studies in wild-type mice showed that SERPINA1 mRNA was biodistributed in the liver and lungs, while SerpinA1 protein was expressed in these two target organs, which are severely affected by AAT deficiency. Taken together, these data suggest that SerpinA1 mRNA therapy has the potential to benefit patients with AAT deficiency.

The researchers evaluated the expression of human SerpinA1 protein in wild-type C57bl/6 mice. As expected, human SerpinA1 mRNA was observed in the liver (Figure 1a), since SERPINA1 mRNA was encapsulated in lipid nanoparticles, which usually deliver a large amount of drug to the liver. An interesting finding was that SERPINA1 mRNA was also detected in the lungs of mice (Figure 1b). The expression of SerpinA1 protein was detected using a human-specific SerpinA1 antibody. SerpinA1 protein was expressed in both the liver (Figure 1c) and lungs (Figure 1d). The sinusoidal distribution pattern of SerpinA1 protein expression in the liver suggests that SerpinA1 protein may be secreted into the blood by hepatocytes.

Figure 1. In vivo human SERPINA1 mRNA biodistribution in liver (a) and the lungs (b) of WT mice 24h after i.v. injection was detected byISH. Red dots in the image represent mRNA. SerpinA1 protein was visualized in liver (c) and lungs (d) by IHC. (Connolly B, et al., 2018)