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Project

Hyaluronic acid (HA) is a naturally occurring linear polymer of repeating disaccharide units of β-1,3-N-acetyl glucosamine and β-1,4-glucoronic acid. It combines attractive functional properties including a unique viscoelasticity, excellent moisture retention capacity and high biocompatibility. Thus, HA finds various applications in cosmetics and biomedical industries. The primary objective of our iGEM project is the broadening of this field of application by producing HA derivatives with promising new features. A possible candidate is the high molecular mass hyaluronic acid (HMM-HA) of the naked mole-rat, which is five times larger than human or mouse HA. It has recently been shown, that this special form of HA mediates the cancer resistance of naked mole rat fibroblasts. HMM-HA binding to the CD44 receptor could be identified on molecular level as crucial part for the inhibitory effect on carcinogenesis in this tissue. Corresponding effects on human fibroblasts have not been tested since the HMM-HA is not commercially available yet.

Therefore the initial step of our project is the first ever production of the naked mole rat HMM-HA. We are going to integrate the HA synthase gene 2 (HAS2) of the naked mole rat in a Bacillus megaterium based expression system. The main advantage of this expression system lies in the already established biosynthetic pathway of the HA precursors since β-1,3-N-acetyl glucosamine and β-1,4-glucoronic acid are also essential components for cell wall synthesis in gram positive bacteria. Nevertheless we want to genetically engineer the biosynthetic pathway for the HA precursors in order to optimise the cost effectiveness and the yield of HA production, especially in regards of a future profitable biotechnological production. Through comparison of homologues against the published B. megaterium genome sequence our team already identified eight potential genes for this optimisation process.

After extraction and purification of the naked mole rat HMM-HA we want to test and further characterise its inhibitory effect on carcinogenesis of selected human cancer cell lines. The experiments will be carried out on both physiological and molecular level. HMM-HA is supposed to cause early contact inhibition (ECI) in naked mole rat fibroblasts by binding to the CD44 receptor. Corresponding proliferation and migration assays with human cancer cell lines supplemented with HMM-HA could be a fast and easy way to prove the inhibitory effect on malignant cell growth. Furthermore we plan to identify the signalling molecules involved in the CD44 pathway. Possible activation of single components of the CD44 pathway can be identidied by real-time PCR quantification. We will focus on the main tumour suppressor gene P53, as it is the crucial regulator of cell cycle progression and genomic stability.

The originality of our project lies in the choice of our experimental models: we use the naked mole rat, an uncommon model organism in scientific research, although it possesses very promising properties. We preferred B. megaterium to the more common model organism E. coli because of its larger size, which permits the storage of more HA, an important factor considering the length of naked mole rat HMM-HA.

We hope that the use of HMM-HA instead of the shorter HA can bolster the properties of HA in cosmetics, eczema treatment as well as treatment for osteoarthritis, and could for this reason be used more efficiently. Our interest lies first and primary on in the application of HA and potentially HMM-HA in cancer treatment.