ABSTRACT
The rd mouse retina is an animal model for human retinal dystrophy in which the rod photoreceptors undergo apoptosis during the first 4 weeks in vivo or in organ culture. We have examined the effect of different families of trophic factors on the survival of rd mouse photoreceptors in organ culture. Retinas were harvested from rd mice at postnatal day 2 and grown in organ culture for 27 days in vitro (DIV) in DMEM with 10% fetal calf serum. Ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF), fibroblast growth factor-2 (FGF2), glial cell line-derived neurotrophic factor (GDNF), neurturin, and persephon were added individually or in combination to the medium at a dose of 50 ng/ml or less. CNTF + BDNF in combination resulted in photoreceptor survival comparable to wild-type retinas after 27 DIV. CNTF + FGF2 or CNTF + GDNF produced a partial prevention of photoreceptor death. Photoreceptor degeneration was not blocked by any of the trophic factors added individually. A significant increase in photoreceptor survival was seen with forskolin added to CNTF, but not to BDNF, FGF2, or GDNF. These results demonstrate that trophic factors promote photoreceptor survival through a synergistic interaction. Increased understanding of receptor interactions and signaling pathways may lead to a potential therapeutic role for combinatorial trophic factors in treatment of photoreceptor dystrophies.
Subject(s)
Growth Substances/pharmacology , Nerve Growth Factors/pharmacology , Photoreceptor Cells, Vertebrate/pathology , Retinal Degeneration/pathology , Animals , Brain-Derived Neurotrophic Factor/pharmacology , Cell Survival/drug effects , Ciliary Neurotrophic Factor/pharmacology , Disease Models, Animal , Drug Interactions , Fibroblast Growth Factor 2/pharmacology , Glial Cell Line-Derived Neurotrophic Factor , Homozygote , Humans , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Nerve Tissue Proteins/pharmacology , Neurturin , Organ Culture Techniques , Photoreceptor Cells, Vertebrate/cytology , Photoreceptor Cells, Vertebrate/drug effects , Retina/pathology , Retinal Degeneration/genetics , Time FactorsABSTRACT
Organ culture systems of the central nervous system have proven to be useful tools for the study of development, differentiation, and degeneration. Some studies have been limited by the inability to maintain the cultures over an extended period. Here we describe an organ culture technique for the mouse retina. This method uses commercially available supplies and reproducible procedures to maintain healthy retinas with normal architecture for 4 weeks in vitro. The system is amenable to quantitative analysis. It can be used with both normal and retinal degeneration (rd) retinas to study of the role of various factors in photoreceptor degeneration in retinal cell fate determination and development.
Subject(s)
Animals, Newborn/physiology , Organ Culture Techniques/methods , Retina/growth & development , Animals , Cell Survival/physiology , Mice , Mice, Inbred C57BL , Microscopy, Electron , Retina/anatomy & histology , Retina/cytologyABSTRACT
Mice homozygous for a defect of the tub (rd5) gene exhibit cochlear and retinal degeneration combined with obesity, and resemble certain human autosomal recessive sensory deficit syndromes. To establish the progressive nature of sensory cell loss associated with the tub gene, and to differentiate tub-related losses from those associated with the C57 background on which tub arose, we evaluated cochleas and retinas from tub/tub, tub/+, and +/+ mice, aged 2 weeks to 1 year by light and electron microscopy. Cochleas from mice of all three genotypes show progressive inner (IHC) and outer hair cell (OHC) loss. Relative to tub/+ and +/+ animals, however, tub homozygotes show accelerated OHC loss, affecting the extreme cochlear base (hook region) by 1 month, and the apex by 6 months. IHC loss in tub/tub animals is accelerated in the basal half of the cochlea, affecting the hook region by 6 months. Spiral ganglion cell losses were observed only in tub/tub mice, and only in the cochlear base. Retinas of tub/tub mice are abnormal at maturity, exhibiting shortened photoreceptor outer segments by 2 weeks, and progressive photoreceptor loss thereafter. Because the tub mutation causes degeneration of sensory cells in the ear and eye but has no other neurological effects, tubby mice hold unique promise for the study of human syndromic sensory loss.
Subject(s)
Cochlea/pathology , Retinal Degeneration/pathology , Animals , Hair Cells, Auditory/pathology , Hearing Loss, Sensorineural/genetics , Hearing Loss, Sensorineural/pathology , Homozygote , Mice , Neurons, Afferent/pathology , Photoreceptor Cells/physiology , Point Mutation , Spiral Ganglion/pathology , SyndromeABSTRACT
A number of autosomal recessive syndromes feature both sensorineural hearing loss and retinal degeneration. The mouse mutant tubby also combines hearing loss with progressive retinal degeneration, and thus may constitute a useful model of one form of human sensorineural deafness/retinal dystrophic syndrome. It has not been directly demonstrated that the hearing loss in this mouse involves the cochlea, however. We have examined the cochleas of adult tubby mice using light microscopy. The tubby cochlea shows pronounced degeneration of the organ of Corti and loss of afferent neurons in the base, with relative sparing of the apex. Our findings support the tubby mouse as a model of human sensorineural deafness/retinal dystrophic syndrome. Possible human counterparts include Usher's, Alstrom's, and Bardet-Biedl syndromes.
