Researchers at Wuhan University (China), the National Research Council of Canada (Ottawa), and the Center for Functional Genomics (Albany, NY, USA) introduced recombinant HSA protein promoters into brown rice plants of the genus Oryza sativa, commonly known as Asian rice. Using Agrobacterium, they developed 25 transgenic plants, nine of which were able to breed. The researchers then succeeded in producing recombinant (HSA) (OsrHSA) from the transgenic rice, with levels reaching 10.58% of the total soluble protein of the rice grain. Physical and biochemical characterization of the OsrHSA revealed it to be equivalent to plasma-derived HSA (pHSA).

Furthermore, in murine models, the efficiency of OsrHSA in promoting cell growth and treating liver cirrhosis was similar to that of pHSA, as well as displaying similar in vitro and in vivo immunogenicity. According to the researchers, the results suggest that a rice seed bioreactor could produce cost-effective recombinant HSA that is safe and could help satisfy an increasing worldwide demand for HSA. Large-scale production of OsrHSA with a purity of over 99% could be consistently done, with a productivity rate of 2.75 grams of albumin per one kilogram of brown rice. The study was published in the November 22, 2011, issue of the Proceeding of the National Academy of Sciences (PNAS).

“Our results suggest that a rice seed bioreactor produces cost-effective recombinant HSA that is safe and can help to satisfy an increasing worldwide demand for human serum albumin,” concluded lead author Yang He, PhD, and colleagues of the Engineering Research Center for Plant Biotechnology and Germplasm Utilization. “More research is needed to evaluate the safety of the rice-derived protein in animals and humans before it can be considered for the market.”

HSA is widely used in clinical and cell culture applications, including the manufacture of vaccines and drugs. The worldwide demand for the blood protein is about 500 tons per year, and China has faced worrying shortages in the past, since conventional production of HSA from human blood is limited by the availability of blood donation. Concerns have also been raised about the potential for the transmission of hepatitis and HIV, since the protein comes from human blood, with a high risk of viral transmission from donors.

Related Links:
Wuhan University
National Research Council of Canada
Center for Functional Genomics