Lens fibre transdifferentiation in cultured larval Xenopus lae7is outer cornea under the influence of neural retina-conditioned medium (original) (raw)
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Cellular and Molecular Life Sciences, 1997
The outer cornea of larval Xenopus lae6is basophilia), cell elongation, gradual loss of basophilic properties and acquisition of acidophilic properties for can reprogram cell differentiation when cultured in medium conditioned by X. lae6is neural retina crystallin synthesis and accumulation. These events were completely dependent on XRCM or RRCM, (XRCM) or by Rana esculenta neural retina (RRCM). Under these experimental conditions corneal cells suggesting that the neural retina secretes a factor(s) which initiates and sustains lens fibre transdifferentia-showed the same series of cytological changes of fibre cell differentiation observed during ontogenesis and in tion of the corneal epithelial cells. This culture system vivo lens regeneration: enlargement of nuclei and nu-appears to be a suitable one for investigating the concleoli, increase of ribosomal population (cytoplasm trol of lens fibre transdifferentiation in vitro.
Development, Growth and Differentiation, 1993
After lentectomy of larval Xenopus laevis, the outer cornea undergoes tissue transformation resulting in formation of a new lens. This lens regeneration is triggered and sustained by neural retina. In the present study, lens-forming transformation of the outer cornea was completed in vitfo when the outer cornea was cultured within the lentectomized eye-cup. Well-differentiated lens fiber cells, which showed positive immunofluorescence for total crystallins, were also formed when the outer cornea was cultivated with the retina. No lens tissue was formed when the cornea was cultured alone. Lens-forming transformation, originating from the cornea three and five days after lentectomy, completely regressed when the tissue was isolated in vitro. Fom the present and previous findings, we concluded that, the interaction of corneal cells with the retina plays a decisive role in lens regeneration in situ.
The optic vesicle promotes cornea to lens transdifferentiation in larval Xenopus laevis
Journal of Anatomy, 2008
The outer cornea and pericorneal epidermis (lentogenic area) of larval Xenopus laevis are the only epidermal regions competent to regenerate a lens under the influence of the retinal inducer. However, the head epidermis of the lentogenic area can acquire the lens-regenerating competence following transplantation of an eye beneath it. In this paper we demonstrate that both the outer cornea and the head epidermis covering a transplanted eye are capable of responding not only to the retinal inducer of the larval eye but also to the inductive action of the embryonic optic vesicle by synthesizing crystallins. As the optic vesicle is a very weak lens inductor, which promotes crystallin synthesis only on the lens biased ectoderm of the embryo, these results indicate that the lens-forming competence in the outer cornea and epidermis of larval X. laevis corresponds to the persistence and acquisition of a condition similar to that of the embryonic biased ectoderm.
Tissue interactions and lens-forming competence in the outer cornea of larvalXenopus laevis
Journal of Experimental Zoology, 2003
After lentectomy through the pupillary hole, the outer cornea of larval Xenopus laevis can undergo transdifferentiation to regenerate a new lens. This process is elicited by inductive factor(s) produced by the neural retina and accumulated into the vitreous chamber. During embryogenesis, the outer cornea develops from the outer layer of the presumptive lens ectoderm (PLE) under the influence of the eye cup and the lens. In this study, we investigated whether the capacity of the outer cornea to regenerate a lens is the result of early inductive signals causing lensforming bias and lens specification of the PLE, or late inductive signals causing cornea formation or both signals. Fragments of larval epidermis or cornea developed from ectoderm that had undergone only one kind of inductive signals, or both kinds of signals, or none of them, were implanted into the vitreous chamber of host larvae. The regeneration potential and the lens-forming transformations of the implants were tested using an antisense probe for pax6 as an earlier marker of lens formation and a monoclonal antibody anti-lens as a definitive indicator of lens cell differentiation. Results demonstrated that the capacity of the larval outer cornea to regenerate a lens is the result of both early and late inductive signals and that either early inductive signals alone or late inductive signals alone can elicit this capacity.
Development, Growth and Differentiation, 1980
The effects of three different culture media (Eagle's MEM, F-12 and L-15) on the transdifferentiation of 8-day chick embryonic neural retina into lens cells, were examined with respect to the expression of two phenotypes. One type referred to neuronal specificity (as represented by the level of cholineacetyl-transferase, CAT, activity) and the other to lens specificity (as represented by the content of n-and d-crystallin). In 7-day cell cultures before the visible differentiation of lentoid bodies, CAT activity was detected in all media. But, its level was about 9 times higher in cultures with L-15 than in those with MEM and 3 times higher than in F-12. In 26-day cultures, CAT activity was practically undetectable. The production of a-and d-crystallin was detected in cultures at 26 days. There were quantitative differences in the crystallin content with different media, and it was highest in cultures with L-15. The results indicate that conditions most favourable to the maintenance of the neuronal specificity in cell cultures of neural retina, can also support the most extensive transdifferentiation. The possibility of direct transdifferentiation of once neuronally specified cells into lens cells in cultures with L-15 has been suggested to explain the present results.
Inhibition of lens regeneration in larvalXenopus laevis
Journal of Experimental Zoology, 1982
The present research aims at showing the role played by the lens in inhibiting lens-forming transformations of the outer cornea of Xenopus laevis tadpoles. Two types of experiment were carried out: 1) lentectomy and insertion of a Millipore filter disk at the side of the lens, and 2) lentectomy and insertion of a Millipore disk with a central hole. Results indicate that when the lens is replaced by a mechanical obstacle capable of preventing direct communication between vitreous and anterior chambers, definite inhibition of the lens-forming transformations of the outer cornea occurs. These data strongly suggest that the inhibition exerted by the lens on lens-forming transformations of the outer cornea in Xenopus laevis eyes is mechanical rather than chemical in nature.
Journal of Experimental Zoology, 1985
Fragments of iris ring, spleen, kidney, tail, tail blastema, tentacle, tentacle blastema, and spinal cord were implanted between the outer and the inner cornea in normal eyes of Xenopus laeuis tadpoles at stage 50 (according to Nieuwkoop and Faber, '56). Results show that tail blastema, tentacle blastema, and spinal cord can induce varying degrees of lens-forming transformations in the outer cornea, while the iris ring, spleen, kidney, tail, and tentacle do not produce any significant response from the cornea, thus demonstrating that the lens-inducing capacity is not widely distributed in the larval tissues of Xenopus. The causes of the different degrees of lens-inducing capacity in the various larval tissues are discussed.
Role of the neural retina in newt (Notophthalmus viridescens) lens regeneration in vitro
Journal of Experimental Zoology - J EXP ZOOL, 1986
Removal of the lens from the eye of an adult newt (Notophthalmus viridescens) is followed by regeneration of a new lens from the dorsal iris epithelial cells at the pupillary margin. This process is dependent upon the neural retina for its normal completion in vivo and in vitro. To examine the relationship between the retina and lens regeneration, we have conducted experiments that delimit the time period during which the retinal presence is critical (in vivo) and have investigated the influence of extracts of the retina on the progress of regeneration (in vitro). In vivo, removal of the retina at day 11 seriously retards further progression of regeneration while removal of the retina at day 15 does not retard regeneration significantly. This defines a "critical period" in regeneration of the lens during which the retina is required. Explantation of regenerates 11 or 12 days after lentectomy to organ culture medium enriched with either crude retinal homogenate or extracts prepared from chick or bovine retinas according to Courty et al. ('85, Biochimie, 67:265-269) reveals that the progress of regeneration can be supported in culture by the crude extract. This is the first demonstration of complete iris-lens transformation in culture in the presence of retinal extract. It is possible that the retina acts indirectly by promoting passage of the iris epithelial cells through the critical number of mitoses required before redifferentiation into lens cells can occur (as proposed by Yamada, '77, Monogr. Dev. Biol., 13:126). It is also possible that the retina acts by directly instructing the iris cells to redifferentiate. Our experiments provide some indirect support for the first possibility but do not distinguish between them at this time.
Journal of Experimental Zoology, 1984
Lumbar ganglia innervating regenerating and normal hindlimbs were removed from larval Xenopus laevis at stage 56-57 (according to Nieuwkoop and Faber, '56) and implanted between the outer and inner corneas of larvae of the same species at stage 50. The control experiments consisted of implanting fragments of liver beneath the outer cornea or of merely separating the two corneas. Results show that the ganglia innervating regenerating limbs and normal ganglia can induce visible lens-forming transformations in the outer cornea, although the percentage of successful cases obtained after the implant of normal ganglia is noticeably lower than that of the ganglia that innervate regenerating limbs. The results are interpreted as due to the action of a neurotrophic factor capable of replacing the action of the retinal factor(s) and produced either by ganglion cells that innervate regenerating limbs or by normal ganglion cells. Nevertheless, normal ganglia are thought to produce less of this substance than ganglia innervating regenerating limbs. No lensforming transformations have ever been found in the controls.
Development, Growth and Differentiation, 1981
Embryonic chick neuroretinal cells transdifferentiate into lens cells during culture in media containing foetal calf serum (F). This process is largely inhibited if horse serum plus supplementary glucose (Hg) is substituted for F. This paper explores the effect of medium changeover (from F to Hg or vice versa) on the subsequent appearance of lens-specific 6-crystallin. If cultures are changed from Hg to F up to 12 days of culture, 6-production at 40 days is similar to that for controls maintained in F throughout. Changeovers between 14 and 17 days progressively inhibit subsequent 6 production, and after 19 days in Hg, lens transdifferentiation cannot be induced by F. Conversely, if cultures are maintained in F for up to 17 days, a changeover to Hg blocks transdifferentiation, whereas similar transfers performed after 19 days give increased 6 production. These results suggest that some retinal cells which will eventually form lens in vitro become so determined between the 12th and 20th days of culture. A mixture of 50% Hg and 50% F medium (FHg) does not support 6 production even after 60 days, but in the absence of supplementary glucose (FH), 6 appears in considerable amounts by 30 days. Both lens and pigment cells are formed extensively during prolonged culture of embryonic neuroretinal (NR) cells in media containing foetal calf serum (