1.
Ap.박명희 / R4 이승진
Endogenous VEGF Is Required for Visual Function: Evidence for a Survival Role on Müller Cells and Photoreceptors Magali Saint-Geniez, Arindel S. R. Maharaj, Tony E. Walshe, Budd A. Tucker, Eiichi Sekiyama, Tomoki Kurihara, Diane C. Darland, Michael J. Young, Patricia A. D’Amore PLoS ONE November 2008 | Volume 3 | Issue 11 | e3554

2. Introduction Two independent vascular beds,
; inner retinal vasculature (Blood tissue barrier)
; outer choroidal circulation (fenestrated capillary)
VEGF is expressed by various cell during deveopment
; astrocytes in GCL, Müller Cells, RPE cells

3. Introduction Normal VEGF function during development
Deletion of VEGF in RPE results in failure of choroidal development
Hyperoxia during development ->suppresses VEGF production(ROP)
Normal retianal V. required specific VEGF isoforms
Pathologic VEGF function
VEGF is upregulated in severeal ocular pathologies.
; AMD, PDR….

4. Introduction Function in the normal adults is unclear
Variety of target cell
; neuronal stem cells, ependymal cell, neuronal cell in CNS
Avastin inj. -> increased incidence of retinal tear
preeclalmpsia -> elevated level of soluble form of VEGF R
-> systemic VEGF neutralization
; choroidal ischemia and RD

5. Introduction Hypothesis
VEGF plays a role in maintenance and function of the adult retina.

6. Systemic VEGF neutralization does not affect retinal vasculature
;Adenovirus expressing sFlt1
(sFlt1 – soluble form of VEGFR1)
- Prior reports
: role for VEGF in maintenance of microvasculature of various organ (trachea, pancreas, thyroid)
-> Changes in retinal vasculature?
Systemic VEGF 중화를 avastin 보다 사용한 것은 장기적인 영향을 알고 싶었기 때문 -

7. Systemic VEGF neutralization does not affect retinal vasculature
Expressing sFlt1 for 14 days revealed no gross changes in retinal vasculature
(flat mounted, fluorescein perfused)
No gross abnormalities or perfusion defects
No changes in capillary density in the inner retina

8. Systemic VEGF neutralization does not affect retinal vasculature
No difference in overlay of collagen IV at inner retinal vessels
-> normal perfusion
No reduction in the number of perfused vessels

9. Systemic VEGF neutralization does not affect retinal vasculature
No change in ultrastructure of choriocapillaris (especially, fenestration)
다른 연구와 달리
Capillary 의 fenestration이 감소하지 않은 것은
Fenestration의 감소가 일시적이어서 관찰되지 않았을지도 모른다고 설명

10. Significant reduction in the thickness of the INL and ONL
VEGF neutralization leads to neuroretinal cell apoptosis and loss of retinal function
Significant reduction in the thickness of the INL and ONL
Examination of retinal cryosections from mice expressing sFlt1 for 14 days revealed significant apoptosis in both the INL and ONL

11. Scotopic ERG revealed a marked reduction of both a and b wave
VEGF neutralization leads to neuroretinal cell apoptosis and loss of retinal function
Apototic cells
Müller cell Amacrine cell photorecepter cell
Scotopic ERG revealed a marked reduction of both a and b wave

12. Autocrine VEGF signaling plays a role in Müller cell survival
76% reduction in VEGF mRNA(day3) 94% reduction in VEGF protein (day3)
FACS analysis demonstrated increase of apoptotic cells in siVEGF transfected cells compared to siControl

13. Autocrine VEGF signaling plays a role in Müller cell survival
Significant up-regulation of the pro-apoptotic gene, bax, and
by the increase of the Bax/Bcl-2 ratio

14. VEGF is a direct survival factor for photoreceptors
Significant decreased in the number of apoptotic photoreceptors in presence of VEGF (ONL explants)
Serum이 없으면 photoreceptorcell이 금방 죽지만 VEGF를 첨가하니 더 살아남았다.
Decreased the number of dead cells identified by trypan blue staining
(in serum free condition)

15. Discussion VEGF effects are not specific to the vasculature
(proliferation, differentiation, survival via VEGFR2)
Glial cell, neuronal cells of retina
And photoreceptor cell, Müller cell ->VEGFR2

16. Discussion Autocrine role of VEGF in Müller cells in vivo
VEGF autocrine signal promotes Müller cell survival
No changes in the level of expression of Bcl-2, Bcl-xl
Decreased level of Bax
-> VEGF regulates Müller cell apoptosis
by control of p53 expression and Bax expression

17. Discussion
The requirement of glial and neuronal cells for VEGF as a survival factor under normal conditions
Dependence on VEGF signaling may be due to the high metabolic rates of retinal neurons and their extreme sensitivity to hypoxia

18. Discussion
VEGF neutralization interferes with endogenous survival signals, leading to unexpected neural toxicity
The absence of NV in the normal retina c VEGF
; dose, localization, opposite factor like TGF-β, angiopoietin-1
VEGF may find use as a neural survival factor for degenerative retinal pathologies.