Corneal transplantation has experienced great evolution in the past decade, thanks to the advancements in endothelial transplantation techniques. However, corneal stroma rehabilitation is still limited by the drawbacks of penetrating (PK) and deep anterior lamellar keratoplasty (DALK) techniques: slow visual recovery, rejection risk for PK, shortage of donor tissue and long learning curve for DALK.
Despite the great efforts made in recent years to replicate the corneal stroma in the laboratory to find an alternative to classical corneal transplantation, this has not yet been accomplished – due largely to the extreme difficulty in mimicing the highly complex ultrastructure of the corneal stroma; obtaining substitutes with either insufficient transparency or insufficient strength.
Cellular therapy of the corneal stroma is currently being investigated as a possible treatment option to alleviate corneal stroma opacities. Extraocular mesenchymal stem cells (those derived from the adult adipose tissue) are an ideal source of autologous stem cells, since the tissue is easily accessible, there is high cell retrieval efficiency, and the cells are able to differentiate in multiple cell types (keratocytes, osteoblasts, chondroblasts, myoblasts, hepatocytes, neurons, etc).1
This has been demonstrated in animal models, as recorded by several authors, including reports from our own research group.2-4 We have seen that ocular and extraocular mesenchymal stem cells are able not only survive to and differentiate into adult human keratocytes in xenogeneic scenarios without inducing any inflammatory reaction, but also to produce new collagen within the host stroma.2,5
The cells can also modulate pre-existing scars by corneal stroma remodelling6,7 and improve corneal transparency in animal models for corneal dystrophies by collagen reorganisation as well as in animal models for metabolopathies by the catabolism of the accumulated proteins.8-11
Mesenchymal stem cells have also shown immunomodulatory properties in syngeneic, allogeneic and even xenogeneic scenarios.11,12