**5. Future prospects**

#### **5.1 Organ bioengineering and regenerative medicine**

The field of tissue engineering is evolving rapidly and is opening new horizons for novel treatment opportunities. Tissue engineering and regenerative medicine includes artificial and biological materials.

Whole organ decellularization and recellularization have gained importance in recent years. Decellularization, as the name implies, means the removal of all cellular components from the organ and at the same time, the micro and macro anatomy of the extracellular matrix is preserved. These scaffolds are repopulated with patient- derived cells or stem cells to construct an individual specific organ. Consequently immunosuppression is no more needed. Bioreactors are used for decellularization and recellularization [24].

The technology used for organ bioengineering includes seeding cells on supporting scaffolding materials. The cell-scaffold technology uses adult cells, various progenitor cells, and progenitor cells that may differentiate into specific adult cells. Bioreactors are used for uniform scaffold distribution, nutrient supply, and waste removal. The regeneration process takes place in the bioreactors and consequently, bioengineered tissues and organs can be harvested for analysis and implantation. Bioreactors facilitate, monitor, and control biochemical and biophysical processes [25].

Mostly used scaffolds are decellularized allogeneic extracellular matrix which in turn is recellularized by autologous or stem cells. A wide variety of human tissues and organs have been decellularized for tissue engineering. These include cartilage, bone, skeletal muscle, tendon, adipose tissue, heart, arteries and veins, gingiva, cornea, vocal folds, peripheral nerves, intestine, liver, pancreas, kidney, bladder, male and female reproductive systems, products of child birth and complex composite structures. Decellularization requires efficient removal of immunogenic cellular materials and maintenance of nonimmunogenic extracellular matrix. Human tissues are harvested from cadavers and surgery. An advantageous point is the fact that
