Harvard Catalyst Profiles

I am an ophthalmologist and immunologist whose principal research interest is determining the molecular and cellular regulation of corneal and ocular surface immunity. In particular, we focus on the role of cytokines and chemokines in induction of antigen-specific corneal immunology, recruitment and activation of ocular antigen-presenting cells, and the interface of lymphangiogenesis and corneal inflammation. The principal venue of my research activities is in my laboratory at the Schepens Eye Research Institute, but is complemented with extensive ‘clinic-to-lab’ and translational ‘lab-to-clinic’ research activities that are performed in conjunction with my academic clinical subspecialty practice at the Massachusetts Eye and Ear Infirmary (see further below for details).

To address the principal objectives of our research program, we optimized the orthotopic model of corneal transplantation in the mouse to determine specific mechanisms involved in: (i) antigen-presenting cell (APC) mobilization in the cornea, (ii) APC-blood and –lymph vessel interactions, (iii) APC mobilization from eye to lymphoid organs including regional draining lymph nodes, and (iv) APC sensitization of T cells in transplantation and autoimmunity. Our work has been instrumental in delineating the precise mechanisms by which pro-inflammatory cytokines work in concert to upregulate specific chemokines and cell adhesion molecules that mediate trans-endothelial migration of APCs from the intravascular compartment into the corneo-limbal matrix. We have shown that this process of APC mobilization into the corneal matrix can be effectively suppressed, with concomitant blunting in the activation of cornea-specific immunity, with topical blockade of relevant cytokines and chemokines. We subsequently showed that once mobilized, these antigen-laden APCs can migrate from the graft to regional lymph nodes to induce T helper-1 type immunity through an interleukin-12-dependent mechanism. This pathway which becomes activated in states of high inflammation is distinct from the normal (default) migration of “tolerogenic” ocular APC to the spleen where they can promote a specific form of immune unresponsiveness termed anterior chamber-associated immune deviation, explaining how the eye, an immune privileged organ, can also be susceptible to destructive immunity. We have also shown the T cell response generated differs considerably between transplants and in chronic autoimmunity (the latter as seen in dry eye disease).

Our work led to important novel and unexpected discoveries. My lab was the first to discover several distinct populations of uniformly MHC class II— highly immature APCs (including epithelial Langerhans cells and stromal CD11b+ myeloid CD11c+ dendritic cells) in the central cornea, breaking a longstanding dogma that the cornea was devoid of any antigen-presenting cell population. We also showed that these immature/precursor populations can mature to acquire high CD40, CD80, and MHC class II expression as they egress the eye through selective upregulation of specific receptors (e.g. CCR7) to prime naïve T cells under conditions of inflammation, including after corneal transplantation. We have also determined a novel role for the tyrosine kinase receptor vascular endothelial growth factor receptor-3 (VEGFR-3), which is known to be a growth factor for lymphatic (and to some extent budding blood vessel) endothelia. We have determined that this receptor is expressed by mature MHC class IIhi dendritic cells in the cornea, and mediates their chemotactic mobilization into lymphatics, thereby allowing their egress from the eye. Importantly, we showed that blockade of this pathway can suppress the trafficking of APC from the eye to regional lymph nodes and suppress the induction of delayed hypersensitivity to corneal transplants—a finding we published in Nature Medicine. We have also successfully demonstrated that disruption of the ‘eye-lymphatic axis’ pharmacologically can suppress generation of autoimmune dry eye disease.

Our work has also shed light onto one of the oldest mysteries in ophthalmic biology—namely, how the cornea maintains its avascular structure, and thereby allows for light to be focused on the retina with minimal interference. We have shown high constitutive and ectopic expression of VEGFR-3 by the corneal epithelium serves as a “sink” mechanism for VEGF-C/D, preventing their ligation of vascular endothelial VEGFR-2, and thereby functioning as a critical mechanism for maintaining corneal avascularity (PNAS). More recently, we have shown that IL-17 can promote lymphatic development through upregulation of VGEF-D (Blood).

Our work in corneal transplantation immunology permitted us since 2006 to launch a broad and productive program determining the immunopathogenesis of dry eye disease, a chronic autoimmune disease whose precise pathogenesis was barely understood even a few years earlier. We developed, and validated, a novel preclinical model for dry eye disease that did not rely on gene deletion or transgenic technology and used it in our basic research program to focus on the molecular mechanisms that mediate (i) selective growth of neolymphatics into dry eye corneas, (ii) induction of T helper-1 (Th1) and Th17 autoimmunity, (iii) development of Th17 cell resistance to Treg suppression, and (iv) the expression of autoreactive T cell homing chemokines on the ocular surface. These studies have been complemented with a number of ‘proof of concept’ therapeutic strategies in preclinical models of dry eye, such as antagonism of cytokines (IL-1, IL-17), prolymphangiogenic factors (VEGF-C/D, VEGFR-3), T cell homing chemokines (CCR5), and leukocyte recruitment mechanisms such as integrins (VLA-4). More recently, we have shown that development of chronic ocular surface/dry eye disease is linked to development of effector memory IL-17 secreting cells, whose function amplifies autoimmunity by suppressing regulatory T cells pathways.

These basic investigation efforts have been complemented with an active program in clinical and translational research. We created the Cornea Research department at the Mass Eye and Ear in 2007 and the Ocular Surface Imaging Center in 2009; these are staffed by several full-time staff, where a large number of investigator-initiated studies are performed. Studies have focused on novel strategies to manage high-risk corneal and stem cell transplants, pathological corneal angiogenesis, dry eye, and in vivo corneal immuno- and neuro-imaging. Our group has been one of the first to develop and clinically test biologic approaches in the management of corneal and ocular surface diseases. These studies have been facilitated by 8 successful FDA IND approvals received by our group since 2008. In all, the combined research efforts of the Dana group have led to over 200 peer-reviewed publications.

In addition to research, I have focused extensively on education, both clinical and research. This has included teaching of postdoctoral research fellows, clinical fellows and residents, and medical students and graduate students enrolled in various Harvard Medical School curricula—I have served as primary mentor to over 80 trainees from 29 countries. In addition to my considerable efforts to contribute to the investigation-based peer-reviewed literature, I served as one of the editors to the 14-volume American Academy of Ophthalmology Basic and Clinical Science Course (the principal educational tool of US and Canadian residents for Board certification), responsible for content in corneal inflammation and immunity. Finally, as a strong believer in the importance of clinical scientists in bridging the wide gap between basic science and clinical applications, I direct the Harvard-Vision Clinical Scientist Development Program funded by the NIH K12 mechanism- with the express intent of recruiting, training, and retaining the brightest young minds to Harvard to contribute to our research efforts. I have served as PI/Director for this program since its inception at Harvard Ophthalmology in 2004, and successfully received refunding in 2010 to continue the program. The $7M+ we have received for this program since 2004 has led to recruitment of numerous clinician-scientists to the Harvard Department of Ophthalmology.