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Simplifying the preservation at very low temperature of tissues used in ophthalmology

Researchers have compared the effects of −28 °C (standard freezer) and −80 °C preservation on human amniotic membrane, which is commonly used in ophthalmic surgery. 

According to the World Health Organisation, corneal disorders are the fourth leading cause of blindness worldwide. [1, 2] The treatment of corneal blindness requires clean rooms, well-run tissue banks and surgical expertise to combine cultured cells with an amniotic membrane, which is used as a graft to facilitate eye healing. [2] 

 

Indeed, the transplantation of human amniotic membrane (AM) has been increasingly used for a variety of ocular pathologies. The role of an amniotic membrane transplantation in the ophthalmic setting is usually to support damaged tissue, protect and shield defects from further degeneration or breakdown due to external factors and promote re-cellularisation. This is possible due to a myriad of biological properties, including: anti-angiogenic (i.e. slows or stops tumours from growing), anti-inflammatory, anti-scarring, anti-microbial, etc. These biological properties support and facilitate wound healing. [3] In a nutshell, microscopically, the AM closely resembles damaged ocular tissue and can be used as a patch to help the body regenerate. [4] 

 

Preservation at −80 °C is the most commonly used method for storing human amniotic membrane. However, this method requires an ultra-deep-freezing facility, which can be too expensive to buy and maintain in developing countries. A team of German researchers have investigated whether storage at −28 °C (using a standard household freezer) could be shown to preserve the clinically relevant properties of human AM in the same way as storage at −80°C. Using eight samples of human AM stored at −80 °C or −28 °C for an average of 8.2 months, they found no overt disadvantages to preservation at −28°C compared to −80°C. Indeed, the essential characteristics of AM were preserved. [5] 

 

For more details on the impact of cryopreservation on the clinical properties of AM, please read the study published in the Journal of Clinical Medicine.   

 

 

Sources 

[1] Blindness and vision impairment. WHO (2021). https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment 

[2] Seeing the light: Using regenerative medicine to cure blindness in developing countries. https://www.sheffield.ac.uk/research/features/regenerative-medicine-cure-blindness  

[3] Walkden, A. (2020). Amniotic membrane transplantation in ophthalmology: An updated perspective. Clinical Ophthalmology (Auckland, NZ), 14, 2057. https://doi.org/10.2147%2FOPTH.S208008  

[4] Synthetic Amniotic Membrane. https://gtr.ukri.org/projects?ref=104650#/tabOverview  

[5] Witt J, Grumm L, Salla S, Geerling G, Menzel-Severing J. Cryopreservation in a Standard Freezer: −28 °C as Alternative Storage Temperature for Amniotic Membrane Transplantation. Journal of Clinical Medicine. 2022; 11(4):1109. https://doi.org/10.3390/jcm11041109