Biological Scaffolds

Biological scaffolds are produced by the decellularisation of tissues and organs. The extracellular matrix (ECM) is isolated from native cells and genetic material, leaving a scaffold. The ECM scaffold ideally retains its inherent structure and can be recellularised to produce a functional tissue or organ.

Some clinical products composed of decellularised tissues already in use are porcine heart valves, human pericardium used in ophthalmology and bovine pericardium used in dentistry (Crapo et al., 2011, Biomaterials 32, 3233 – 3243).

Various decellularisation methods have been developed. They are roughly classified into three groups as follows: chemical treatments (e.g., detergents, acids and bases, and alcohols), biological treatments (e.g., enzymes), and physical treatments (e.g., freezing and thawing, pressurization, and electroporation) (Nakamura, N., et al., ACS Biomater. Sci. Eng. 2017, 3, 1236−1244).

One recent application of tissue decellularisation is that of decellularised human elastic cartilage for future use in ear reconstruction. Ear reconstruction is challenging due to the complex structure of the ear. Currently costal cartilage grafts are used for the reconstruction but the mechanical properties are different from those of elastic cartilage.  A study by Rahman et al. has identified a successful process for producing an acellular elastic cartilage ECM. This study incorporated the use of trypsin in the process. The results showed that collagen, which is vital for biomechanical strength of the scaffold as well as guiding chondrogenic differentiation, was retained in the ecm. Glycosaminoglycans however were reduced but not completely lost – this allows for greater cellular infiltration if recellularisation is attempted.

Reference

Rahman,S., Griffin,M., Naik,A., Szarko,M. and Butler,P.E.M. (2018) Optimising the decellularization of human elastic cartilage with trypsin for future use in ear reconstruction. Scientific reports 8, 3097.