Tissue decellularization methods

The use of decellularized tissues and organs can be very interesting for tissue engineering applications as they mimic both the shape and biochemical composition of native tissues. However, a challenge associated with the application of some decellularized tissues is their limited potential for recellularization, as healthy cells need to be incorporated into the ECM to generate a functional and viable tissue for successful tissue engineering approaches. 1

As a solution to this problem, decellularized biomaterials can be used as hydrogels for cell encapsulation and distribution. Check this article to learn more about decellularized extracellular matrix-based hydrogels. The decellularization technique involves removing cellular tissue components so that only the ECM remains. The way this technique is performed can alter the composition of the ECM and thus change the properties of the hydrogels. The various methods for decellularization can be divided into three main categories: physical, chemical, and biological, which can be used in combination or not with each other, depending on the strategy used to achieve a high level of decelularization while keeping ECM integrity. 1

Figure 1: Decellularization methods.

Physical methods of decellularization include freeze-thaw cycles, high hydrostatic pressure, or supercritical CO2 (scCO2). Treatment with scCO2 results in sterile acellular tissues, which is advantageous because it eliminates additional sterilization steps. According to recent reviews, the application of decellularization via supercritical CO2 reveals that most treatment protocols took only 1 hour to achieve complete decellularization, offering an advantage over conventional methods in terms of time. 2

Chemical methods generally involve detergents that are used to solubilize cell membranes and dissociate their internal structure. These detergents can be ionic or non-ionic. Ionic detergents, such as sodium dodecyl sulfate, are effective in removing nuclear remnants and they can completely solubilize cell and nucleic membranes and fully denature proteins. Non-ionic detergents, such as Triton X-100, the most commonly used detergent in decellularization processes, aim to destroy lipid-lipid and lipid-protein interactions but leaving the protein-protein interaction intact. In addition to detergents, saline solutions such as sodium chloride; and acids and bases, such as ammonium hydroxide, are also used as chemical methods. 1 3 4

As biological methods, enzymes such as trypsin, dispase, and phospholipase A2 are the most used. Furthermore, nucleases, such as DNAse, are used to promote the fragmentation of residual DNA into smaller fragments to allow maximum cell removal and minimize immune responses. 1

Decellularization can be achieved from different tissues but must be designed according to the properties of the target tissue and the intended approach. Whether physical, chemical, or biological, each type of method affects the biochemical composition, tissue ultrastructure, and mechanical behavior of the remaining ECM; all of these factors affect the cell's response to the material, as well as its mechanical performance. 5 6

REFERENCES

1. Fernández-Pérez, J. & Ahearne, M. The impact of decellularization methods on extracellular matrix derived hydrogels. Sci. Rep. 9, 14933 (2019).

2. Topuz, B., Günal, G., Guler, S. & Aydin, H. M. Use of supercritical CO2 in soft tissue decellularization. Methods Cell Biol. 157, 49–79 (2020).

3. Mendibil, U. et al. Tissue-Specific Decellularization Methods: Rationale and Strategies to Achieve Regenerative Compounds. Int. J. Mol. Sci. 21, (2020).

4. White, L. J. et al. The impact of detergents on the tissue decellularization process: A ToF-SIMS study. Acta Biomater. 50, 207–219 (2017).

5. Blaudez, F., Ivanovski, S., Hamlet, S. & Vaquette, C. An overview of decellularisation techniques of native tissues and tissue engineered products for bone, ligament and tendon regeneration. Methods 171, 28–40 (2020).

6. Gilbert, T. W., Sellaro, T. L. & Badylak, S. F. Decellularization of tissues and organs. Biomaterials 27, 3675–3683 (2006).