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Impressum
Adhesion molecules in Bruch´s membrane
1,2,3Hermans P.; 2Wojtecki S.; 1,2Heiligenhaus A.; 2Bornfeld N.; 1Pauleikhoff D.
1Ophtha-Lab, Dept. of Ophthalmology at St. Franziskus-Hospital, Hohenzollernring 72/74, 48145 Münster, GER; 2Univ. Eye Hosp. Essen, Hufelandstr.55, 44122 Essen, GER; 3Inst. of Zool. & Gen. Westf.- Wilhelms-Univ. Münster, Schlossplatz 5, 48149 Münster, GER
Purpose: The purpose of the study was to investigate the normal
composition of the adhesion complex in Bruch´s membrane (BM) composed
of extra cellular matrix (ECM) proteins and of cellular adhesion molecules
especially different integrins in the basal laminae (BL) at the retinal
pigment epithelium (RPE) and Choriocapillaris (CC) and the changes with
age.
Methods: Cryo sections of 60 donor eyes (4-95y) were processed
with immunoperoxidase staining for ECM proteins laminin, fibronectin,
vitronectin, collagen type IV. To investigate the integrin composition
the subunits alpha 2, 3, 4, 5, 6, V, beta 1, 2 and the heterodimers alpha5beta1,
alphaVbeta3 and alphaVbeta5 were processed. Staining intensity was classified
into three classes: positive, weak positive and negative and results were
compared between three age groups: <39y; 40-69y, >70y.
Results: In donors<39y laminin, fibronectin, vitronectin, and
collagen IV could be observed in both BL of BM. In donors 40-69y and >70y
laminin, fibronectin and collagen IV showed a decreased positive staining
in the RPE BL but less in the BL of CC. Only vitronectin was detectable
in specimen of all age groups in both BL. In respect to different integrins
in the RPE BL alpha V is the dominant integrin subunit in all age groups.
The other integrin visible in young specimen is the alpha5beta1 heterodimer
with regression in the older age groups. The dominant integrin in the
BL of the CC was alpha5 as heterodimer alpha5beta1 but no changes with
age could be observed.
Discussion: These results show that the ECM and the adhesive complex
of both BL of BM consists of specific patterns of integrin subunits associated
with specific ECM proteins as ligands. Only the RPE BL showed a regression
of laminin and fibronectin connected to collagen IV combined with a regression
of the associated integrin subunits, while vitronectin and his associated
integrins are always present. These specific change of the integrin and
ECM proteins in the RPE BL may result in functional insufficient adhesive
properties of this structure producing a "cleavage edge" for
splitting of BM between the RPE BL and the inner collagenous layer of
BM as visible in different AMD (age related macular degeneration) changes.
Supported by the Deutsche Forschungsgemeinschaft (DFG Pa 357/5-1)