Squamous metaplasia occurs in severe ocular surfaces diseases (e.g., Stevens-Johnson syndrome (SJS), ocular cicatricial pemphigoid (OCP) and Sjogren's syndrome (SS)) that present some of the most challenging clinical cases facing eye care providers today. By definition, squamous metaplasia is a phenotypic change whereby epithelial cells initiate synthesis of specialized, squamous cell-specific proteins like small proline- rich protein 1B (SPRR1B) to form the cornified envelope (keratinization). While SPRR1B expression is a normal feature of external squamous tissues like the skin, it is a sign of pathology when present in mucosal tissues such as the ocular surface. Very little is known about the molecular mechanisms triggering squamous metaplasia and efforts to inhibit it have so far been unsuccessful. Interestingly, the presence of squamous metaplasia has been extensively correlated with proinflammatory activity of the ocular surface, but the possibility that proinflammatory cytokines released from infiltrating cells actually contribute to squamous metaplasia has never been examined. Based on this, we propose to examine the hypothesis that inflammatory mediators are key regulators of pathological keratinization. Our preliminary data support this possibility and identify IL-1beta as a key participant in this process.
In Specific Aim 1, we will validate the use of SPRR1B as a clinical marker for squamous metaplasia in human subjects. SPRR1B expression will be correlated with the levels of inflammatory mediators at the ocular surface using impression cytology and tear samples collected from human patients with SS in collaboration with the Sjogren's International Collaborative Clinical Alliance (SICCA) group at UCSF.
In Specific Aim 2, we will examine the role of IL-1beta as a major inducer of squamous metaplasia in a murine model of SS that is lacking the autoimmune regulator (AIRE) gene. Squamous metaplasia in AIRE-deficient mice will be assessed following competitive inhibition and genetic ablation of IL-1 signaling. We will then attempt to reestablish the squamous phenotype through topical application of IL-1beta.
In Specific Aim 3, we will use SPRR1B to define gene elements mediating the induction of squamous metaplasia by IL-1beta. This will include traditional luciferase reporter assays and electrophoretic mobility shift assays to identify IL-1beta -response elements on the SPRR1B promoter and bound transcription factors. This combination of translational and molecular approaches will improve our understanding of the pathogenesis of squamous metaplasia and will open the possibility of developing novel treatments to prevent pathological keratinization in human patients.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
3R01EY016203-04S1
Application #
7905471
Study Section
Special Emphasis Panel (ZRG1-BDCN-H (93))
Program Officer
Shen, Grace L
Project Start
2006-08-01
Project End
2011-08-31
Budget Start
2009-09-01
Budget End
2011-08-31
Support Year
4
Fiscal Year
2009
Total Cost
$366,127
Indirect Cost
Name
University of California San Francisco
Department
Ophthalmology
Type
Organized Research Units
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
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