A combination of CNTF and BDNF rescues rd photoreceptors but changes rod differentiation in the presence of RPE in retinal explants.
OBJECTIVE
To gather information regarding the combination of ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF), compared with the individual factors when used as a treatment to retard photoreceptor cell loss in rd mouse retina explants and to investigate the observation that the retinal pigment epithelium (RPE) influences rod differentiation by this treatment.


METHODS
Postnatal day (PN)2 or PN7 control and rd mouse retinas were grown with attached retinal pigment epithelium (RPE). The explants were kept in culture up to PN28. During this culture period CNTF, BDNF, CNTF+BDNF, or vehicle were continuously administered to the culture medium. The nontrophic factors cyclosporin A and N:-CBZ-aspartic acid-glutamic acid-valine-aspartic acid-fluoromethyl ketone (z-DEVD-fmk) were also used. The number of photoreceptor nuclei remaining in the outer nuclear layer (ONL) was analyzed in hematoxylin and eosin-stained sections. Rod- and cone-specific antibodies were used to determine identity and state of differentiation of the photoreceptors.


RESULTS
Compared with vehicle treatment, BDNF or CNTF resulted in 1.4- or 2-fold more surviving cell rows in the ONL, respectively. However, when CNTF and BDNF were applied together, surviving ONL cell counts in the rd explants were approximately 3 times those in vehicle-treated explants. In the presence of CNTF or CNTF+BDNF, opsin and arrestin expression in rods was decreased compared with rods without attached RPE. Cyclosporin A and z-DEVD-fmk did not show rescue of rd photoreceptor cells.


CONCLUSIONS
CNTF or BDNF treatment of rd retinal explants delays photoreceptor cell loss to some extent. However, when these agents are combined, photoreceptor rescue is much more effective. The quenching of opsin and arrestin expression caused by treatment suggests that simultaneous with rod rescue, rod differentiation is depressed. Regarding retinal degeneration, the results from the selective inhibitors of apoptosis rank the CNTF+BDNF combination treatment as the most consistent and effective experimental pharmacologic intervention currently available.
Caffé
A R
AR
Department of Zoology, Göteborg University, Sweden.
Söderpalm
A K
AK
Holmqvist
I
I
van Veen
T
T
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019393:Arrestin / Q000378:metabolism; D019208:Brain-Derived Neurotrophic Factor / Q000627:therapeutic use*; D002454:Cell Differentiation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D020934:Ciliary Neurotrophic Factor / Q000627:therapeutic use*; D018920:Coculture Techniques; D004359:Drug Therapy, Combination; D007124:Immunoenzyme Techniques; D051379:Mice; D008809:Mice, Inbred C3H; D009924:Organ Culture Techniques; D020419:Photoreceptor Cells, Vertebrate / Q000187:drug effects; D010857:Pigment Epithelium of Eye / Q000473:pathology*; D012162:Retinal Degeneration / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism / Q000473:pathology*; D017299:Rod Opsins / Q000378:metabolism
D019393:Arrestin; D019208:Brain-Derived Neurotrophic Factor; D020934:Ciliary Neurotrophic Factor; D017299:Rod Opsins