S.Sharareh Mahdavi - Chemical Engineering Department/Sharif University of Technology, Tehran, Iran.
Mohammad j. Abdekhodaie - Chemical Engineering Department/Sharif University of Technology, Tehran, Iran.
Shohreh Mashayekhan - Chemical Engineering Department/Sharif University of Technology, Tehran, Iran.
Alireza Baradaran-Rafii - Ocular Tissue Engineering Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Cornea is known as a window of the eye. It contains three main layers of epithelium, stroma, and endothelium. Moreover, adjustment and control of the arrival light are two of its important tasks. Therefore, any injury to each layer of it can cause remarkable effect on the visual acuity. Besides, aging is another reason for corneal degeneration. Nowadays, depending on the level of the injury, eye drops and donor tissue transplantation are the most prevalent treatments for corneal diseases. However, lack of the donor tissue, risk of infection and rejection attracts scientists to use tissue engineering for corneal regeneration. This approach is basically divided into four main categories: cell or stem cell injection, scaffold based cell carriers, growth factor injection, and artificial cornea. In the two first methods, different types of cells such as mesenchymal stem cells, embryonic stem cells, and allogeneic or autologous corneal cells are either injected directly or delivered using biocompatible scaffolds to the injured area. It is expected that delivered cells migrate and integrate in the host tissue and restore vision. Growth factor delivery also has shown promising results for corneal surface regeneration. Moreover, the latter mostly contains synthetic biomaterials as an alternative for donor tissue.In this article, the available literatures on each of the mentioned approaches have been reviewed. The diversity of cells and materials used for treating various corneal diseases has been studied. Finally, both advantages and disadvantages of different methods have been discussed to accomplish a proper strategy for corneal regeneration.

Corneal regeneration, Cell delivery, Scaffolds, Growth factor.