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A growth-promoting influence from the mesonephros during limb outgrowth
1Department of Biology, University of Iowa, Iowa City 52242.
Abstract:
It has been suggested that the mesonephros has a role in normal limb development. This hypothesis was directly tested by removing the mesonephros adjacent to the presumptive limb region of stage 12-18 chick embryos using microsurgery or laser ablation. The experimental manipulation resulted in reduced limb outgrowth on the operated side. The poor limb outgrowth was correlated with either the lack of or the presence of a rudimentary mesonephros on the operated side. Furthermore, the presence of nephric tissue in limb bud organ culture enhanced growth and morphological differentiation of cartilage formed in culture. In vivo, the influence of the mesonephros resulted in significantly higher cell proliferation in the adjoining medial half of the limb mesoderm compared with the lateral half. The removal of the mesonephros adjoining the prospective limb region reduced the number of dividing cells in the medial mesoderm. The higher proliferation in the medial limb mesoderm is significant to limb outgrowth since grafting experiments showed that most of the cells that form the limb are derived from the medial mesoderm. The results suggest that the influence from the mesonephros may provide some signal for limb outgrowth.
Insights
The mesonephros plays a crucial role in chick embryo limb development. Its removal stunts limb growth by reducing cell proliferation in the medial limb mesoderm.
Area of Science:
- Developmental Biology
- Embryology
- Regenerative Medicine
Background:
- The mesonephros, a transient kidney in embryonic development, has been hypothesized to influence limb formation.
- Understanding the precise role of the mesonephros in limb development is essential for insights into congenital limb abnormalities.
Purpose of the Study:
- To experimentally investigate the direct role of the mesonephros in embryonic chick limb development.
- To determine if the mesonephros influences cell proliferation and outgrowth in the developing limb.
Main Methods:
- Microsurgery and laser ablation were used to remove the mesonephros adjacent to the limb bud in stage 12-18 chick embryos.
- Limb bud organ cultures were performed with and without adjacent nephric tissue to assess growth and differentiation.
- Cell proliferation was quantified in medial and lateral limb mesoderm following mesonephros removal or presence.
Main Results:
- Removal of the mesonephros led to significantly reduced limb outgrowth.
- The presence of mesonephric tissue in vitro enhanced limb bud cartilage growth and differentiation.
- Mesonephros removal decreased cell proliferation in the medial limb mesoderm, a region critical for limb formation.
Conclusions:
- The mesonephros exerts a positive influence on chick limb outgrowth.
- This influence appears to be mediated, at least in part, by promoting cell proliferation in the medial limb mesoderm.
- The findings suggest the mesonephros provides essential signals for normal limb development.