Vol.98 No.7 contentsPRACTICA OTO-RHINO-LARYNGOLOGICA
Vol. 98 No. 7 July 2005
Frefront of Regenerative Medicine
Shin-ichi Kanemaru
(Graduate School of Medicine, Kyoto University)
Regenerative medicine has made remarkable progress. This has been supported by the development of tissue engineering that was a combination of medicine and engineering. Tissue engineering applies the principles and methods of engineering, material science, and cell and molecular biology toward the development of viable substitutes which restore, maintain, or improve the function of human tissues.
According to the theories of tissue engineering, tissues and organs can be regenerated by manipulating three elements: cells, scaffold and regulation factors. In this field, cells mean stem cells that posses both capabilities of self-renewal and differentiation into various tissue-specific cells. Stem cells are divided into two groups: embryonic stem cells (ES cells) and somatic stem cells. Although ES cells are the best cell-source having the omni potency to generate all tissues, ethical problems and rejections by the immune system remains to be resolved. On the other hand, somatic stem cells are promising cell-sources because they are free of the above problems. Actually, almost all clinical applications of regenerative medicine have been performed using somatic stem cells or progenitor cells. Mesenchymal stem cells (MSCs) belonging to somatic stem cells are defined as pluripotent progenitor cells with the ability to generate bone, cartilage, muscle, tendon, ligament and fat. Moreover, in some kind of conditions, MSCs can be differentiated into other lineages: nerve, epithelium and so on. These properties have generated great interest in the potential use of MSCs to replace damaged tissues. Mesenchymal stem cells could be cultured to expand their numbers, or seeded in/on shaped biomimetic scaffold to generate appropriate tissue constructs, then transplanted to the injured site.
A scaffold that sustains cells is necessary to regenerate injured tissues and organs. Owe to the development of biotechnology and polymer chemistry, we can create more desirable biomaterial scaffolds with appropriate mechanical properties that can be modified to incorporate biological activity, such as growth factors and structural adhesive proteins. It is no exaggeration to say that successful regeneration of tissues and organs depends on how to establish an appropriate scaffold in the injured site.
Regulation factors also play an important role in tissue regeneration. They can induce angiogenesis, which promotes a sufficient supply of oxygen and nutrients to effectively maintain the biological functions of cells transplanted for organ substitution. Therefore, if we do not understanding and manipulate the complex relationships among cells, scaffolds and regulation factors, we cannot repair and/or regenerate tissues and organs.
This article discusses the basic principles of tissue engineering and introduces some of the clinical practices in regenerative medicine.
Key words : regenerative medicine, tissue engineering, ES cells, mesenchymal stem cells, scaffold, regulation factor