This is a literature review of the current status of tissue engineering related to ocular and oculoplastic reconstructive surgery. The authors describe the process of bioengineering for tissue reconstruction. The aim is to reproduce functional tissue by the use of scaffold materials in combination with either a stem cell or precursor cell population. The scaffold should provide structural support, be biocompatible and porous, support tissue growth and be biodegradable as it needs to provide both mechanical support and an environment which allows tissue regrowth. Various scaffold materials have been described in the literature, with the aim of matching the host tissue it is replacing as closely as possible. Different scaffolds are therefore required depending on the mechanical and biological properties of the tissue they are repairing. Both synthetic and natural polymers have been used. Poly(lactic-co-glycolic) acid (PLGA) is a biodegradable synthetic polymer approved by the US Food & Drug Administration (FDA) for human use. Artificial corneal matrices composed of recombinant human collagen have been used in humans as cell free implants which become integrated demonstrating regeneration of the corneal epithelium, stroma and nerves.
There are a few animal studies of tissue-engineered implants for conjunctival replacement including successful seeding of human fibroblasts onto a modified PLGA scaffold, and attempts to produce secreting implants for severe dry eye. Bioresorbable implants have been used successfully in blow-out fracture repairs in humans, and research is continuing into combining synthetic scaffolds with periosteal cells, cultured osteoblasts and bone marrow to facilitate bone regeneration. Polyhydroxyalkanoates have been used as a tarsal plate substitute in an animal model, but elicited a strong inflammatory response. It is postulated that preimplantation of cultured native cells may improve the biocompatibility of the synthetic materials and the authors refer to their own work with cultured fibroblasts derived from human skin. This is an interesting paper summarising the developments in tissue engineering as it relates to ophthalmology. There is significant progress occurring in this new and exciting field with the hope of increasing use of bioengineered tissues on the horizon.
