Billions of people rely on rice as a staple crop. Now here’s another reason to grow it: scientists have figured out a way to use the grain to produce a key component of human blood.
The blood protein is called human serum albumin, or HSA, which is normally produced by the liver and helps ferry hormones, steroids and fatty acids in the bloodstream. HSA is also used in drug and vaccine production, and to treat patients in hemorrhagic shock or with serious burns, cirrhosis or other conditions.
The HSA used for therapeutic purposes is largely harvested the conventional way, from human blood donations. But that doesn’t produce nearly enough HSA to meet the yearly global demand, which exceeds 500 tons per year. Hence, the efforts to grow the protein another way.
Scientists have been using plants like potatoes and tobacco to produce HSA for two decades, but the yield has been low. So researchers in China, where health officials have struggled with contaminated blood supplies and HSA shortages, decided to try rice. Rice seeds have already been useful for making other human proteins, including lysozyme and lactoferrin, which are found in breast milk, saliva and other bodily fluids.
Led by Daichang Yang, a plant biotechnologist at Wuhan University in China, scientists successfully used bacteria to insert the HSA gene into Oryza sativa rice plants. Nature News reported:
Yang and his colleagues inserted the gene encoding HSA into their rice plants in such a way that the gene was activated during seed production, and the resulting protein was stored in the rice grain along with nutrients normally used to help nurture a germinating embryo. The final product was a crop of rice seeds in which HSA made up more than 10% of the seeds’ total soluble protein — one of the best yields of recombinant protein from plants to date. …
The rice-derived protein was shown to be functionally equivalent to the version found in human blood plasma. Not only were the two chemically and physically identical, but they were also similar when tested for medical efficacy and immune reactivity. In rats with liver disease, both types of HSA proved equally effective in relieving symptoms associated with cirrhosis. And rats that were given rice-derived HSA showed no stronger immune reaction than animals that had been given the plasma-derived version.
The researchers said they were able to extract HSA from rice efficiently, reporting that they got 2.75 g of HSA from every kilogram of brown rice — a sufficient yield to scale up the process for commercial production, they said. If it works, using rice to make HSA could be not only cost efficient, but also safer than extracting it from plasma, since it would not be vulnerable to the infections that can be transmitted by blood.
Next, lead researcher Yang hopes to test the rice-derived protein in humans. He’s submitted an application to the U.S. Food and Drug Administration (FDA) for a clinical trial.
The new study was published online Monday by the Proceedings of the National Academy of Sciences.