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Developing Clinical Trials for Novel Approaches to Repairing Corneal Scarring With Corneal Stromal Stem Cells and Exosomes

May 10, 2021

The Funderburgh Laboratory in the Department of Ophthalmology, has made seminal discoveries in corneal biology and has developed an approach to repair damaged or scarred corneal tissue. In 2005, The Funderburgh Laboratory, led by the late James L. Funderburgh, PhD, along with colleague Yiqin Du, MD, PhD, were the first to identify and characterize stem cells resident within the connective tissue of the corneal stroma. Subsequently, Dr. Funderburgh and colleagues determined that the corneal stromal stem cells (CSSCs) they discovered could successfully regenerate and restore corneal transparency in animal models of corneal scarring. Carrying this work forward, in 2014, the group was able to use human CSSCs to prevent corneal scarring in an animal model. Using the approach developed by the Funderburgh Laboratory, registered clinical trials in India have successfully treated more than 80 patients with acute and chronic corneal opacities. However, data from these trials are still pending publication.

The Cornea Task Force in the Department of Ophthalmology has dedicated its work to develop and launch clinical trials at the University of Pittsburgh using the protocols and techniques established by the Funderburgh Laboratory. The goal of the Corneal Task Force is to complete all of the necessary preparatory work, protocols, clinical grade cell line manufacturing, and institutional and regulatory approvals by the end of 2023 in order to launch the first human trials in the United States soon thereafter.

The Cornea Task Force and the Funderburgh Corneal Regeneration Project is currently led by Gary Yam, PhD, Deepinder K. Dhaliwal, MD, L.AcVishal Jhanji, MD, and Dr. Du. 

Dr. Yam has recently been recruited from Singapore and is a basic scientist interested in studying the biology of the corneal stroma, epithelium, and endothelium. He directs the Corneal Regeneration Laboratory in the Department of Ophthalmology, which focuses on understanding the biological processes that produce and maintain the corneal stroma, as well as studying the pathological changes that occur in corneas in the setting of injury, wound healing, and diseases.

Work done by Dr. Yam before joining the University of Pittsburgh involved developing a cell-based approach using an intrastromal injection of corneal stromal keratocytes to repair corneal opacities. Corneal stromal keratocytes are the differentiated product of CSSCs. Dr. Yam's work and the previous work of Dr. Funderburgh's are, in essence, two sides of the same coin: one designed to use the CSSCs via topical application to regenerate damaged stomal tissue; the other using the mature keratocytes in an injectable formulation to achieve the same result: transparent corneas. Dr. Yam's work in Singapore before joining the University of Pittsburgh also discovered a novel type of corneal endothelial progenitors4 which could produce the corneal endothelium. This work is another active line of investigation in his laboratory.

“Our team is actively working on bringing this work to fruition in human clinical trials in the United States. We are developing a GMP-compliant protocol version of Dr. Funderburgh’s cell platforms in order to  test his corneal wound healing methodology in human subjects,” says Dr. Yam. “This will then allow us to subsequently expand our trials to study the use of our keratocyte injection method. Further down the road, our goal is to test other corneal tissue regeneration mechanisms that are evolving with the use of cell-free therapies such as exosomes and microRNA approaches,” says Dr. Yam

Cell-Free Therapies: Exosomes and Corneal Tissue Regeneration

The therapeutic approaches developed by Dr. Funderburgh, Yam, and colleagues require the use of human tissues and cells – CSSCs or keratocytes. However, there are limited amounts of donor tissues available to use for transplantation and to generate clinical grade stromal cell products. Also a factor is the complication of potential risk of rejection of the transplanted cells and the fate of cells in the new stromal environment.

“Dr. Funderburgh published findings several years ago5 showing that extracellular vesicles in part mediated CSSC regeneration – exosomes delivering microRNAs – and that when applying just the secreted exosomes onto the corneas of injured models, the tissue underwent the same regenerative process as in the CSSC method," says Dr. Yam. “One of our longer-term goals is to develop this approach further and test it in animals before human trials.”

Not only would this cell-free approach essentially eliminate the issue of tissue rejection and immune response by the host, but the method could also be applied via topical eye drop to the cornea by the patient themselves, simplifying the process.

Read more about the Department of Ophthalmology, Cornea Task Force, the Funderburgh Project and Dr. Funderburgh’s legacy, and ongoing work of Dr. Yam in the Corneal Regeneration Laboratory.


1. Du Y, Funderburgh ML, Mann MM, SundarRaj N, Funderburgh JL. Multipotent Stem Cells in Human Corneal Stroma. Stem Cells. 2005; 23(9): 1266-1275.

2. Du Y, Carlson EC, Funderburgh ML, Birk DE, Pearlman E, Guo N, Kao WW, Funderburgh JL. Stem Cell Therapy Restores Transparency to Defective Murine Corneas. Stem Cells. 2009; 27(7): 1635-1642.

3. Basu S, Hertsenberg AJ, Funderburgh ML, Burrow MK, Mann MM, Du Y, Lathrop KL, Syed-Picard FN, Adams SM, Birk De, Funderburgh JL. Human Limbal Biopsy-Derived Stromal Stem Cells Prevent Corneal Scarring. Sci Transl Med. 2014; 6(266): 266ra172.

4. Yam GH, Seah X, Yusoff NZ, Setiawan M, Wahlig S, Htoon HM, Peh GSL, Kocaba V, Mehta JS. Characterization of Human Transition Zone Reveals a Putative Progenitor-Enriched Niche of Corneal Endothelium. Cells. 2019; 8(10): 1244.

5. Shojaati G, Khandaker I, Funderburgh ML, Mann MM, Basu R, Stolz DB, Geary ML, Dos Santos A, Deng SX, Funderburgh JL. Mesenchymal Stem Cells Reduce Corneal Fibrosis and Inflammation Via Extracellular Vesicle-Mediated Delivery of miRNA. Stem Cells Transl Med. 2019; 8(11): 1192-1201.