A new study from researchers at the University of Pecs, Hungary used cell secretions known as exosomes to regenerate one of the most important organs in the body- the Thymus.

The Thymus shrinks as we grow older

After puberty, the thymus begins to slow down and becomes replaced by fat. The hormone produced by the Thymus is called Thymosin and this stimulates the development of disease fighting T-Cells.

It should be borne in mind that the Thymus is only active until puberty, but it still plays a long-term significant role in overall health with its other function as an endocrine and lymphatic gland.

Over time, researchers have tested multiple approaches to regenerate the thymus, causing it to regrow and resume efficient T cell production; some of these methods are still on going. Although, this study takes an original approach, as it encourages the thymus to regrow using exosomes.

Exosomes – what are they?

Exosomes are found in nearly all eukaryotic fluids (the fluids that live in cells and surround the nucleus and organelles). They are small vesicles which contain proteins and other molecules, and they are essential as they enable a wide range of important cellular functions. This includes the transfer of RNA, DNA and proteins to other body cells.

The Study

Researchers used EVs, specifically exosomes to seek out the thymus and encourage thymic tissue rejuvenation. To achieve this, they focused on activating the transcription factor FOXN1, the master regulator of thymus organogenesis and identity, which ensures that new cells become T-cell producing tissue rather than fat.

FOXN1 is directly targeted by the glycolipoprotein Wnt4 in order to activate it, which makes Wnt4 critical for thymus growth during development and for maintaining the organ during adulthood. However, as we age our thymic epithelial cells produce less Wnt4. Meaning that they begin to lose thymic identity and instead turn into fat cells; this causes the thymus to begin involution and T cell production to decrease.

This study presents that exosomes gathered from the transgenic thymic epithelial cells were able to counter gene expression changes in other thymic epithelial cells exposed to them, thus preserving thymic cell identity and preventing those cells from changing into mesenchymal or adipose cells, which leads to thymus involution and loss of T cell production.

Conclusion

Remarkably, the exosomes from the thymic epithelial cells hadn’t previously been linked to thymus regeneration, until now. These results show that their contributions to the growth, maintenance and regeneration of the organ are significant.

Further Reading:

1. ‘Transgenic Exosomes for Thymus Regeneration’, Banfai, Garai, Ernzst et al. Front. Immunol., 24 April 2019 | https://doi.org/10.3389/fimmu.2019.00862
2. An overview of the Thymus: https://www.endocrineweb.com/endocrinology/overview-thymus
3. What are Exosomes? https://bioinformant.com/what-are-exosomes/