Elevating the expression level of biologically active recombinant human alpha 1-antitrypsin in Pichia pastoris

Background: Human alpha 1-antitrypsin (AAT) is a potent inhibitor of multiple serine proteases, and protects tissues against their harmful effects. Individuals with reduced or abnormal production of this inhibitor need intravenous administration of exogenous protein. In this study, we employed the methylotrophic (methanol utilizing) yeast Pichia pastoris (P. pastoris) as a preferential host for efficient production and secretion of recombinant AAT. Furthermore, we examined different strategies to maximize the yield of the secreted protein. Results: Our findings revealed that optimizing the codon usage of AAT gene for P. pastoris had positive effects on the level of secreted AAT under the control of inducible alcohol oxidase 1 (AOX1) and constitutive glycerol aldehyde phosphate dehydrogenase (GAP) promoters. Compared to AOX1, the GAP promoter increased the yield of AAT by more than two fold. It was also demonstrated that the human AAT native signal sequence was more effective than the well-known yeast signal sequence, alpha mating factor (α-MF). Doubling gene dosage nearly doubled the production of AAT, though dosages exceeding this limit had negative effects on the yield. Conclusion: P. pastoris is shown to be an efficient expression system for production of recombinant and biologically active AAT. Also different strategies could be used to elevate the amount of this secretable protein.

Transplantation of retinoic acid treated murine embryonic stem cells & behavioural deficit in Parkinsonian rats.

Background & objectives: Stem cell therapy has been considered as an ideal option for the treatment of Parkinson’s disease. Murine embryonic stem cells (mESCs)-derived dopaminergic (DA) neurons may substitute the degenerated neurons in the brain. In this study we generated highly enriched cultures of neural progenitors from mESCs and grafted them into the striatum of Parkinsonian rats to evaluate their ability to improve impaired function. Methods: An animal model was developed for Parkinson’s disease in rats, using 6- hydroxy dopamine. The animals were divided into two groups: (i) the control group treated with culture medium only, and (ii) the experimental group, which was treated with a murine ESC cell-line (CCE). Transplanted cells were labelled with bromodeoxyuridine (BrdU), exposed to retinoic acid and then engrafted within the striatum of the rat model. Results: Treated ES cells by retinoic acid were found to relieve apomorphine-induced asymmetric motor behaviour. Immunohistochemistry results revealed tyrosine hydroxlase immunoreactivity in engrafted cells 15 days after transplantation. Further, the ultrastructural examination along with cresyl violet staining confirmed that the cells gained neuronal and glial appearance. Interpretation & conclusions: Our data demonstrate that retinoic acid treatment and transplanting ESC cells to the lessioned brain can lead to the generation of putative dopaminergic neurons and functional recovery in parkinsonian rat model with.