Center/Research Area Affiliations
Dr. Zieske is interested in understanding the mechanisms involved in corneal wound repair. The corneal epithelium is the outermost layer of the eye and is seven cell layers thick. It is considered the first line of defense against foreign materials and therefore, must heal quickly in order to prevent the entry of foreign materials. Currently, his laboratory is investigating how the stroma and epithelium interact during corneal fibrosis and regeneration. He has found that expression of integrin avb6 in the epithelium after wounding appears to play a major role in directing the fibrotic response in the cornea. The current focus of his laboratory is the role of exosomes on cell-cell communication and the stimulation of fibrosis.
Download his CV or biosketch [PDF] for more information.
Ph.D., Biological Chemistry, University of Michigan (1981)
Research Fellowship, Cell Surface Glycoproteins and Epidermal Differentiation, University of Michigan (1981-1982)
Research Fellowship, Cell Surface Proteins in Corneal Epithelium, Schepens Eye Research Institute of Mass. Eye and Ear (1982-1984)
With continuous support from the National Eye Institute since 1984, Dr. James Zieske’s research aims to better understand the mechanisms involved in corneal wound repair. To date, his laboratory has published more than 90 peer-reviewed articles in this area.
The Zieske laboratory is currently investigating how the stroma and epithelium interact during corneal fibrosis and regeneration. Fibrosis, or scarring, is an evolutionarily developed method to rapidly close and repair a wound. Excessive deposition of extracellular matrix and the generation of contractile fibroblasts (myofibroblasts) characterize fibrosis. In the cornea, severe wounds that damage the basement membrane heal using fibrosis. However, in contrast to other tissues where function is maintained, fibrosis in the cornea leaves an opaque cornea that can impair vision.
During the past two years, Dr. Zieske and his laboratory members have made the exciting observation that expression of integrin avb6 in the epithelium after wounding appears to play a major role in directing the fibrotic response in the cornea. Integrin avb6 binds to matrix components, but more importantly also has the ability to activate TGF-Beta 1 (T1) and -Beta 3 (T3). These isoforms of TGF-b have been linked to stimulating (T1) and blunting (T3) fibrosis. Interestingly, the preliminary data indicate that a single application of T3 after wounding almost completely blunts the scarring response.
The hypotheses the Zieske laboratory is currently testing are:
- Corneal epithelium stimulates human corneal fibroblasts to undergo fibrosis in the absence of a basement membrane
- Integrin avb6 upregulation in the epithelium is a key component in the stimulation of a fibrotic response in the stromal cells
- Activation of TGF-b3 blunts this fibrotic response
The Zieske laboratory is also currently addressing three questions:
- Does corneal epithelium stimulate a fibrotic response by the stromal fibroblasts in the absence of a basement membrane via the release of exosomes?
- Is avb6 expression required for the stimulation of a fibrotic response?
- Does T3 inhibit fibrosis in corneal wounds?
Mechanisms involved in corneal wound repair
Phosphorylation of the EGFR (erbB) Family During Corneal Wound Repair
Dr. Zieske and colleagues have shown that EGFR (erbB-1) is activated during corneal epithelial wound repair. However, recent discoveries have shown that erbB-1 frequently forms heterodimers with other members of the erbB family and that different heterodimers may allow enhanced or differential biological responses. Since they and others have found that other members of the erbB family are present in the corneal epithelium, it is possible that heterodimers are formed. Information regarding dimer formation may be important in that it may indicate which members of the family of erbB ligands and receptors are actually stimulating the healing response. We have also observed that EGF, in combination with TGF-b1, stimulates T b R-II expression and that inhibition of erbB-1 kinase activity by AG1478 appears to block T b R-II expression. Dr. Zieske is currently testing the following hypotheses
- ErbB heterodimers are formed and activated during corneal wound repair.
- Activation of erbB homo- or heterodimers stimulates the expression of T b R-II, helping to generate the non-proliferative migratory phenotype.
Role of Exosomes in Corneal Wound Repair
Over the past two years, Dr. Zieske and colleagues made the exciting observation that the epithelium releases exosomes that stimulate fibrosis in human corneal fibroblasts (HCF). Exosomes are nanovesicles (30-100nm) that are released from most cells and are part of a larger group of vesicles released from cells, termed extracellular vesicles (EVs). EVs have been the subject of intense research efforts in the past five years after the discovery that they carry “cargo” consisting of proteins, mRNA, and miRNA, which can affect the behavior of adjacent cells. Indeed, this appears to be a major mechanism in the initiation of cancer, where EVs from cancer cells invade host cells and stimulate them to secrete matrix that supports the cancer cells. While examining EVs from the cornea, Dr. Zieske and colleagues made several interesting observations: 1) All three major cell types of the cornea release EVs; 2) EVs isolated from human corneal epithelial cells stimulate the expression of alpha-smooth muscle actin (a marker of fibrosis) in HCF; 3) Epithelial EVs do not appear to penetrate the epithelial basement membrane; and 4) EVs from unwounded corneal epithelial cells do not appear to stimulate fibrosis, but EVs from wounded epithelium do stimulate fibrosis in HCF. These observations suggest that the cargo in EVs released by wounded epithelium is altered compared to those that are not wounded.
These observations lead us to Dr. Zieske's current hypothesis that EV cargo from epithelial cells is altered during wound repair to contain proteins that stimulate fibrosis in HCF. Over the course of the next few years, they will examine several aspects of EV biology in the cornea:
- Compare proteins, and possibly mRNA and/or miRNA, in the cargo of EVs isolated from wounded and unwounded corneal epithelial cells, as well as examine the effect of matrix using our 3-dimensional HCF constructs.
- Examine if EV cargo is altered in keratocytes compared to myofibroblasts, and if the EVs from myofibroblasts contain cargo that enhance the fibrotic response
- Use time-lapse microscopy to examine migration characteristics of the EVs in the cornea.
During this time, several questions will be examined, including:
- Do epithelial EVs penetrate the epithelial basement membrane?
- What are the dynamics of EV penetration into the cornea?
- Do endothelial EVs penetrate the Descemet’s membrane?
Dr. Zieske's preliminary findings indicate that epithelial EVs interact with stromal cells and endothelial EVs do penetrate the Descemet’s membrane. The overall goal is to understand the interactions of EVs in the cornea. In the process, if he find sthat topically applied EVs can alter corneal activities, this would have great clinical potential, as EVs could be loaded with cargo that could blunt fibrosis or other corneal diseases.
Current Research Funding
||NIH/NEI R01 EY005665: Principal Investigator
Corneal epithelial-stromal interactions during regeneration and fibrosis
$1 million: total direct costs for current funding cycle, beginning in 2013
The goal of this project is to understand the mechanisms involved in αvβ6 activation of fibrosis, if αvβ6 is required to stimulate fibrosis, and if TGF-β3 blunts the scarring response.
Current Members of Dr. Zieske’s Laboratory
Xiaoqing Guo, Ph.D.
Senior Research Assistant/Laboratory Manager
Audrey E.K. Hutcheon, B.S.
More than 15 trainees have worked in Dr. James Zieske’s laboratory. To view the complete list of alumni, download his CV [PDF].