Caspase dependence of the death of neonatal retinal ganglion cells induced by axon damage and induction of autophagy as a survival mechanism

We examined the degeneration of post-mitotic ganglion cells in ex-vivo neonatal retinal explants following axon damage. Ultrastructural features of both apoptosis and autophagy were detected. Degenerating cells reacted with antibodies specific for activated caspase-3 or -9, consistent with the presence of caspase activity. Furthermore, peptidic inhibitors of caspase-9, -6 or -3 prevented cell death (100 µM Ac-LEDH-CHO, 50 µM Ac-VEID-CHO and 10 µM Z-DEVD-fmk, respectively). Interestingly, inhibition of autophagy by 7-10 mM 3-methyl-adenine increased the rate of cell death. Immunohistochemistry data, caspase activation and caspase inhibition data suggest that axotomy of neonatal retinal ganglion cells triggers the intrinsic apoptotic pathway, which, in turn, is counteracted by a pro-survival autophagic response, demonstrated by electron microscopy profiles and pharmacological autophagy inhibitor.

Prometeo: regeneración tisular: pifias de la naturaleza y esperanzas de la ciencia / Prometheus: tissue regeneration: natural errors and scientific hope

En el movisimo campo de las células troncales ("stem cell") y la medicina regenerativa, la búsqueda del Santo Grial de la investigación científica, es la recreacion o la inducción del renacimiento de un órgano funcional, llamese hígado, retina o riñon. En un extremo el hígado de Prometeo, de inherente capacidad para regenerarse, la demanda del órgano excede en mucho la disponibilidad de donantes. En Estados Unidos de America, 9% de los pacientes con insuficiencia hepática fallecen a la espera de un trasplante, así que la investigación en tratamientos regenerativos nunca ha tenido más fundamento y adquirido más énfasis que en estos tiempos. En el otro extremo, la retina, inexplicable olvido de la naturaleza, como otras neuronas del sistema nervioso incapaz de regenerarse a sí misma y hasta ahora, inmune a la neuroprotección y reparación después de una injuria. No obstante en un futuro no muy lejano será posible preservar y restaurar la visión en personas en las que se encuentre amenazada o se haya perdido por enfermedad o injuria del nervio óptico

In the newest field of stem cells and regenerative medicine, the quest for the Holy Grail of scientific research is the recreation or induction of rebirth of a functional organism, such as the liver, retina o kidney. At one end liver of Prometheus with its inherent capacity to regenerate, has a demand that greatly exceeds the availability of donors. In the United States of America, 9% of patients with liver failure die waiting for a transplant, so research in regenerative treatment has never had more importance or acquired greater emphasis than at this time. At the other end, the retina, inexplicable oblivion of nature, is, as other neurons of the central nervous system, unable to regenerate itself and so far, immune to neuroprotection and repair after an injury. Nevertheless, in the future it will be possible, however, to preserve and restore vision in people whose optic nerve are threatened or have been lost due to illness or injury

Asymmetry Analysis of the Retinal Nerve Fiber Layer Thickness in Normal Eyes using Optical Coherence Tomography

PURPOSE: To investigate the asymmetry of the retinal nerve fiber layer thickness (RNFLT) with respect to the horizontal and vertical meridian and between the right and left eye in normal subjects. METHODS: The RNFLT was measured in 121 normal volunteers by optical coherence tomography (OCT). The RNFLT was analyzed by dividing the circle scanning area (diameter 3.4 mm) around the optic disc into 4 quadrants and 12 sectors. RESULTS: There was a significant difference between the RNFLT of the nasal and temporal quadrant in individual eyes. There was a significant difference between the RNFLT of corresponding sectors with respect to the vertical or horizontal meridian in individual eyes. The nasal and temporal RNFLTs were asymmetrical between the right and left eye in the quadrant and sector analysis. The RNFLT of the nasal and temporal quadrant was thicker in the right eye. The nasal and inferior RNFLT measured by OCT had a significant correlation with degree of refractive error. CONCLUSIONS: In normal subjects without significant anisometropia, there was significant asymmetry of the RNFLT for each eye as well as between the right and left eye.

Organización topográfica y áreas especializadas en la retina de callopistes palluma: capa de células ganglionares / Topographic organization and specialized areas in the retina of callopistes palluma: ganglion cell layer

En este trabajo se analizan la distribución topográfica y el tamaño de los elementos neuronales (células ganglionares y amacrinas desplazadas) ubicadas en la capa 8 de la retina de un saurio chileno, Callopistes palluma, utilizando montajes in toto teñidos con técnica de Nissl. Callopistes palluma presenta una retina afoveada, con un área central donde la densidad de células ganglionares y amacrinas desplazadas es de 20.000 y 7.000 cell/mm², respectivamente. La densidad neuronal cae gradualmente hacia la periferia, extendiéndose en el eje naso-temporal de la retina, estableciéndose para ambos tipos neuronianos una banda horizontal de mayor densidad. En las diferentes zonas de la retina, las células amacrinas desplazadas comprenden entre el 25 y el 30 por ciento de la población neuronal total de la capa 8. El análisis del tamaño celular revela que a nivel del área central se observan neuronas de tamaño pequeño con medianas de 32 µm² para las amacrinas desplazadas. En la retina periférica se aprecia un incremento en el tamaño celular y las medianas suben a 42 µm² y 12 µm² de área celular para las ganglionares y amacrinas, respectivamente. En el texto se discute la correlación entre características retinianas y estilos de caza

NF-kappa B activation following optic nerve transection

In order to elucidate in vivo neuronal cell death in the retina, and involvement of NF-kappa B in this process, we studied the degeneration of retinal ganglion cells (RGCs) and the activation of NF-kappa B after transection of the optic nerve of adult rat at 5 mm from the eyeball. The morphology of dying ganglion cells in the retinal ganglion cell layer was observed by light and electron microscopy, the activation of NF-kappa B was investigated immunohistochemically. Seven and 14 days post-axotomy, dying cells contained pyknotic nuclei. The death of retinal ganglion cells involved apoptosis, activation of NF-kappa B (p50 and p65) was prominent in a time dependent manner. We observed axotomy-induced NF-kappa B activation, which may mediate apoptosis of retinal ganglion cells.

Axon orientation and axo-dendritic polarity of retinal ganglion cells during postnatal development in the rat

The axon orientation and axo-dendritic polarities of ganglion cells were investigated in the retinae of developing and adult rats labeled with retrograde tracers. The cells were classified as either regular, if both parameters corresponded to those found among the majority of ganglion cells in the retina of adult rats, or irregular, if either axon orientation or axo-dentritic polarity, or both to follow the norm of adult retinae. The number of regular cells declined from 118,000 to the adult value of 63,000 during the first 5 days following birth, while the number of irregular cells remained stable at 90,000-100,000 during this period and declined thereafter to 46,000. These data suggest that the geometry of neurites within the retina affect the selective elimination of ganglion cells during postnatal development in rats

The neurons of the retinal ganglion cell layer of the Guinea pig: quantitative analysis of their distribution and size

The topographical distribution of ganglion cells and displaced amacrine cells in the guinea pig retina is described. Neurons were counted in the ganglion cell layer of retinal whole mounts stained by the method of Nissl or retrogradely labeled with horseradish peroxidase. Neuronal soma size was estimated from samples taken from different retinal regions. We estimated that a total of 295,000 neurons comprise the guinea pig ganglion cell layer and they consist of 159,000 ganglion cells and 136,000 displaced amacrine cells. The visual streak is poorly differentiated. Ganglion cell density reaches a peak of 2,272 cells/mm* in a temporal expansion of the visual streak, 4-5 mm toward the optic disk. The visual streak temporal expansion may represent the analogue of the area centralis for this species. The ventral hemi-retina has a higher ganglion cell density than the dorsal hemi-retina. The displaced amacrine cells are more uniformly distributed than the ganglion cells. The present paper provides relevant data concerning the number and distribution of the neurons of the retinal ganglion cell which were not available or were very contradictory in the literature