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Cornea Lab
Die Arbeitsgruppe um Prof. Cursiefen und Dr. Bock beschäftigt sich mit den Mechanismen der
Transplantatabstoßung nach Hornhaut-Transplantation. Hierbei wird der Focus vor allem auf die Rolle
der Lymphgefäße gelegt. Die Hornhaut besitzt ein sogenanntes „angiogenes Privileg“, wodurch die
gesunde Hornhaut von Blut- und Lymphgefäßen freigehalten wird. Dieses System ist durch viele
molekulare Mechanismen gestützt, die selbst noch greifen, wenn invasive Therapien wie Refraktive
Chirurgie an der Hornhaut angewandt werden.
Nichts desto trotz kann es durch Infektionen, Verbrennungen oder auch durch vorangegangene
Transplantationen zum Einwachsen von klinisch sichtbaren Blutgefäßen und klinisch unsichtbaren
Lymphgefäßen kommen. Unsere Arbeitsgruppe untersucht mit verschiedenen Techniken sowohl die
Entstehung und Interaktion der Lymphgefäße mit anderen Zellen des Immunsystems als auch
Möglichkeiten, das Wachstum und die Interaktionen zu beeinflussen oder zu verhindern.
Angewandte Methoden sind die Immunhistochemie, Molekularbiologische Methoden wie qPCR und
Westen Blot, FACS Analyse, Zellkultur und intravitale Multiphotonenmikroskopie in Zusammenarbeit mit
der AG Augenoberfläche.
Die Arbeitsgruppe steht in engen Kontakt zur Klinik und ist daher stark in den Prozess "From Bench to
Bedside and back" eingebunden, so dass klinikrelevante Themen bearbeitet werden.
Univ.-Prof. Dr. Claus Cursiefen
Profil
Sekretariat: Marie Seifert
Telefon +49 221 478-4300
E-Mail [email protected]
Dr. Felix Bock
Telefon +49 221 478-97789
Telefax +49 221 478-97836
E-Mail [email protected]
Our Team
Wissenschaftler
Prof. Dr. Claus Cursiefen
Prof. Dr. Björn Bachmann
Priv.-Doz. Dr. rer. nat. Felix Bock
Dr. rer. nat. Maria Notara
Dr. rer. nat.Thomas Clahsen
Dr. Deniz Hos
Dr. Franziska Bucher
Anna Lentzsch
Doktoranden
Yanghong Hou
Dr. Viet Nhat Hung Le
Alex Doulis
Ann-Charott Schneider
Anne Bukowiecki
MTA
Sara Behboudifard
Gabriele Braun
Marie-Luise Dreisow
Tim Gabriele
The role of lymphatic vessels in transplant rejection
Immune-mediated graft rejections remain the most common cause for graft failure after organ and
tissue transplantation. There exists a great unmet medical need for pharmacologic strategies to promote
graft survival without unduly compromising the health of the recipient.
The three structural components of the immune system allowing for immune responses against foreign
tissue after transplantation are afferent lymphatic vessels (“afferent arm of the immune reflex arc”),
regional lymph nodes (“central processing unit”) and efferent blood vessels (“efferent arm of the
immune reflex arc”).
Lymphatic vessels allow the transport of antigen-presenting cells with foreign tissue antigens and
soluble antigenic material to the regional lymph node and thereby constitute one of the earliest events
in the immune-cascade leading to rejection. The precise relative importance of lymphatic vessels
(“afferent arm”) versus blood vessels (“efferent arm”) for immune reactions after transplantation is yet
unclear. But every solid organ or vascularized tissue transplantation is accompanied by angiogenesis
and lymphangiogenesis across the wound edges. In fact, lymphatic vessels have been identified in
allogeneic grafts after heart and kidney transplantation where their presence seems to be related to
graft rejection.
Corneal hem- and lymphangiogenesis occurring both prior to as well as after corneal transplantation
significantly increase the risk for immune rejection: The rate of immune rejections in patient eyes with
avascular graft beds is approximately 10%, whereas the rate of immune rejections increases in prevascularized, so called high-risk patient eyes to 50-100%. Lymphatic vessels and blood vessels override
the so called immune privilege of the normally avascular cornea.
A combined modulation of hemangiogenesis and lymphangiogenesis by VEGF-TrapR1R2 after normalrisk corneal transplantation can improve graft survival in the murine model of corneal transplantation.
Blocking preferentially lymphangiogenesis over hemangiogenesis leads to inhibition of the induction of
an immune response and at the same time blood vessels can still support the graft with nutrients and
enable wound healing. The high-risk status of corneal allografts in vascularized host beds is defined by
the lymphatic vessels and the preferential inhibition of lymphangiogenesis prior to transplantation is
able to improve graft survival by interfering with sensitization and immune rejection.
Therefore it is important to identify ways to preferentially block lymphangiogenesis to promote graft
survival.
Lymphatic vessels in dry eye diseases
Dry eye disease (DED) is the most common disease in ophthalmology. Up to 63% of the general public
suffer from this malfunction of the precorneal tear film. A dysfunctional tear layer leads to ocular pain
and serious vision impairment. DED can be induced by inflammatory diseases like autoimmune
destruction of the lacrimal gland in Sjörgen´s Syndrom (5.1) as well as by desiccation, androgen
deprivation or ageing. Independent of the underlying cause a secondary ocular surface inflammation
occurs in most patients with DED. Recently we observed in a murine model of DED in Sjörgen´s syndrom
(5.1) a spontenous and selective outgrowth of lymphatic vessels together with an increase of immune
cells in the normally avascular cornea (5.3). This unexpected finding may suggest a novel
pathomechanism in DED implicating lymphatic vessel-mediated sensitization.(5.2). The important role of
lymphatic vessels in other immunological reactions in the cornea like corneal transplant rejection was
recently approved by our group.
Genetic Heterogeneity of Lymphangiogenesis in Different Mouse Strains
Contrary to angiogenesis, where substantial progress in understanding the molecular mechanisms and
regulation-pathways was gained in the last decades, lymphangiogenesis research was long hampered by
the absence of specific molecular markers. This changed with the discovery of specific molecular
markers, such as LYVE-1, Podoplanin, Prox1, and VEGFR-3 and various in vitro and in vivo models in the
last few years.
However, available information concerning the field of lymphangiogenesis research still lags behind
hemangiogenesis (e.g., in the field of genetic diversity). Genetic heterogeneity of angiogenesis in mice
was first reported in 2000 by Rohan et al., who showed that—dependent on the genetic
background—the response to growth factor–induced angiogenesis varies significantly between different
inbred mouse strains. Strain-dependent differences were also published for the density and surface area
of the resting limbal vessels after bFGF-induced neovascularization in the cornea. Genetic diversity
influencing angiogenesis-regulating genes is implicated in altering the susceptibility to angiogenesisdependent diseases like cancer, diabetic retinopathy, psoriasis, and others. In contrast to the evidence
for genetic heterogeneity on angiogenesis, to date little is known in this context about
lymphangiogenesis.
In different inbred and wild–derived mouse strains (Balb/cAnNCrl, C57BL/6NCrl, 129S1/SvImJ, SJL/JCrl,
Cast/EiJ, FVB/NCrl), significant differences in the lymphangiogenic response were detected: the
lymphvascularized area varied up to 2-fold between “low-responder” strains and the “high-responder”
strains. Furthermore, the preexisting lymphatic vessels in the limbal region, which supports the
avascular cornea with nutrients and is the origin of new blood and lymphatic vessels in the case of
inflammation, are significantly different between low- and high-responders.
Anti-inflammatory and a specific antilymphangiogenic therapies induce different responsiveness to
antilymphangiogenic treatments area in different mouse strains.
There are significant differences in the lymphangiogenic response of several mouse strains and
underlying genetic factors influence the lymphangiogenic response. These considerations need to be
taken into account when using different mouse strains to study lymphangiogenesis and can also explain
different success of antilymphangiogenic treatments in tumor patients.
The role of limbal epithelial stem cells in maintaining corneal avascularity and in the
pathogenesis of UV-induced pterygium
Corneal clarity is essential for vision. It’s avascularity is mediated by a dynamic balance of pro and antiangiogenic signals. An intact corneal epithelium is necessary for transparency and refraction. This
epithelial layer is constantly maintained by a limbal epithelial stem cell (LESC) population residing in the
basal epithelial layer of the limbus. Dysfunction or depletion of limbal epithelial stem cells (limbal stem
cell deficiency [LESCD]) results in persistent corneal inflammation and epithelial breakdowns, corneal
surface conjunctivalisation and corneal neovascularisation. Conditions leading to LESCD and therefore
neovascularization are chemical and thermal burns, inflammatory eye diseases, persistent hypoxia
(contact lens wear) as well as genetic disorders such as aniridia (pax6 haplodeficiency). Patients with
LESCD suffer from photophobia, reduced visual acuity and pain due to recurrent ocular surface defects.
In severe cases LESCD can result to blindness.
UV radiation (UVR) is damaging on various ocular structures leading to a reduction or even loss of visual
function. The use of UV protecting eyewear such as sunglasses and more recently UV blocking clear
lenses and contact lenses is recommended as a prophylactic measure against these harmful effects and
there have been efforts to assess the effectiveness of UV-blocking eyewear more rigorously. The cornea
is particularly susceptible to UV irradiation due to its natural transparency as well as to its shape which
is contributing to a peripheral light focusing effect, affecting the nasal limbus where UV irradiation is 20fold strongest (A). This is the typical site for the onset of pterygium, a non-cancerous growth of the
cornea, usually bilateral, which is occupying the corneal equator (B). The pterygium breaks the limbal
barrier which separates the cornea from the conjunctiva and centripetally invades the cornea surface. It
is characterised by squamous hyperplasia and goblet cell hyperplasia. In advanced cases, the visual axis
may be covered by vascularised opaque tissue thus leading to discomfort and decrease or loss of vision.
Histological findings have led to the hypothesis that pterygium may be initiated by transformed basal
limbal epithelial cells including LESCs which contribute to hyperplasia, tissue remodelling and
vascularisation associated with the disease.
Our research focuses on the underlying molecular mechanisms by which LESCs contribute to corneal
avascularity and how this is tampered following LESC niche exposure to UV. This research aims to
understand the effect of UV to the cellular components of the limbal niche as well as to open up new
treatment avenues against pterygium recurrence by developing preventative treatments against DNA
damage and targeting immune cell recruitment-mediated prolymphangiogenesis.
Current projects
1. The effect of UVA and UVB on the limbal niche and pro-inflammatory and proangiogenic events
UV irradiation causes cumulative DNA damage and has an effect in the functionality of limbal
epithelial cells and fibroblasts (viability, proliferation and migration). The expression of putative
stem cell markers is also affected while proteomic assessment shows changes in proangiogenic, prolymph-angiogenic growth factors and cytokines as well as an upregulation of
molecules which are known to contribute to immune cell recruitment (IFNγ, TNFα, MCP-1).
2. DNA damage in the limbal niche
LESCs are long cycling and therefore can accumulate DNA damage, direct or oxidative. For
these studies, different types of DNA damage as well as strategies for its prevention and
treatment are explored.
3. The protective effect of UV blocking contact lenses to the LESC niche
In collaboration with VISCTAKON® we investigate the potential benefits of a UV blocking
contact lens against UV-induced changes in LESCs. This research has been supported by an
independent research grant from J&J Vision Care.
4. The effect of different antiangiogenic treatments in LESCs
Pharmaceutical approaches of targeting pro-angiogenic and pro-inflammatory molecules are
used clinically to treat and prevent corneal neovascularization. In these projects we investigate
the effect of these treatments to the phenotype and functionality of LESCs.
Support
DFG (FOR 2240; Cu47/41-; 47/6-1); EU (Horizon 2020 Arrest Blindness; STRONG FP7; COST BM1302),
Bayer Graduate Program Pharmacology
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