Senescence Increases Choroidal Endothelial Stiffness and Susceptibility to Complement Injury: Implications for Choriocapillaris Loss in AMD.
OBJECTIVE
Age-related macular degeneration (AMD) commonly causes blindness in the elderly. Yet, it is untreatable in the large fraction of all AMD patients that develop the early dry form. Dry AMD is marked by the deposition of membrane attack complex (MAC) on choriocapillaris (CC), which is implicated in CC degeneration and subsequent atrophy of overlying retinal pigment epithelium. Since MAC is also found on the CC of young eyes, here we investigated whether and how aging increases choroidal endothelial susceptibility to MAC injury.


METHODS
Monkey chorioretinal endothelial cells (ECs, RF/6A) were cultured to high passages (>P60) to achieve replicative senescence. We treated ECs with complement-competent human serum to promote MAC deposition and injury, which were assessed by flow cytometry and trypan blue exclusion assay, respectively. Stiffness of EC was measured by atomic force microscopy indentation while Rho GTPase activity was quantified by Rho G-LISA assay.


RESULTS
Our findings reveal that senescent ECs are significantly stiffer than their normal counterparts, which correlates with higher cytoskeletal Rho activity in these cells and their greater susceptibility to complement (MAC) injury. Importantly, inhibition of Rho activity in senescent ECs significantly reduced cell stiffness and MAC-induced lysis.


CONCLUSIONS
By revealing an important role of senescence-associated choroidal EC stiffening in complement injury, these findings implicate CC stiffening as an important determinant of age-related CC atrophy seen in dry AMD. Future studies are needed to validate these findings in appropriate animal models so new therapeutic targets can be identified for treatment of dry AMD.
Department of Bioengineering, University of California, Riverside, California, United States.
Andrea P
AP
Cabrera
Department of Bioengineering, University of California, Riverside, California, United States.
Arun
A
Bhaskaran
Department of Physics and Astronomy, University of California, Riverside, California, United States.
Jun
J
Xu
Department of Bioengineering, University of California, Riverside, California, United States.
Xiao
X
Yang
Department of Bioengineering, University of California, Riverside, California, United States.
Harry A
HA
Scott
Department of Physics and Astronomy, University of California, Riverside, California, United States.
Umar
U
Mohideen
Department of Bioengineering, University of California, Riverside, California, United States.
Kaustabh
K
Ghosh
D000368:Aged; D000818:Animals; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D002829:Choroid / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D015938:Complement Membrane Attack Complex / Q000378:metabolism / Q000502:physiology*; D003165:Complement System Proteins / Q000494:pharmacology*; D042783:Endothelial Cells / Q000187:drug effects* / Q000502:physiology; D000882:Haplorhini; D006801:Humans; D008268:Macular Degeneration / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D018625:Microscopy, Atomic Force; D012160:Retina / Q000166:cytology
D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins