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Development and regeneration of the zebrafish maxillary barbel: a novel study system for vertebrate tissue growth and repair.

LeClair EE, Topczewski J - PLoS ONE (2010)

Bottom Line: Barbels are integumentary sense organs found in fishes, reptiles and amphibians.Finally, we show that the maxillary barbel can regenerate after repeated injury and also in senescent fish (>2 years old).Although the teleost barbel has no human analog, the cell types it contains are highly conserved.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, DePaul University, Chicago, Illinois, United States of America. eleclair@depaul.edu

ABSTRACT

Background: Barbels are integumentary sense organs found in fishes, reptiles and amphibians. The zebrafish, Danio rerio, develops paired nasal and maxillary barbels approximately one month post fertilization. Small in diameter and optically clear, these adult appendages offer a window on the development, maintenance and function of multiple cell types including skin cells, neural-crest derived pigment cells, circulatory vessels, taste buds and sensory nerves. Importantly, barbels in other otophysan fishes (e.g., catfish) are known to regenerate; however, this capacity has not been tested in zebrafish.

Methodology/principal findings: We describe the development of the maxillary barbel in a staged series of wild type and transgenic zebrafish using light microscopy, histology and immunohistochemistry. By imaging transgenic zebrafish containing fluorescently labeled endothelial cells (Tg(fli1a:EGFP)), we demonstrate that the barbel contains a long ( approximately 2-3 mm) closed-end vessel that we interpret as a large lymphatic. The identity of this vessel was further supported by live imaging of the barbel circulation, extending recent descriptions of the lymphatic system in zebrafish. The maxillary barbel can be induced to regenerate by proximal amputation. After more than 750 experimental surgeries in which approximately 85% of the barbel's length was removed, we find that wound healing is complete within hours, followed by blastema formation ( approximately 3 days), epithelial redifferentiation (3-5 days) and appendage elongation. Maximum regrowth occurs within 2 weeks of injury. Although superficially normal, the regenerates are shorter and thicker than the contralateral controls, have abnormally organized mesenchymal cells and extracellular matrix, and contain prominent connective tissue "stumps" at the plane of section--a mode of regeneration more typical of mammalian scarring than other zebrafish appendages. Finally, we show that the maxillary barbel can regenerate after repeated injury and also in senescent fish (>2 years old).

Conclusions/significance: Although the teleost barbel has no human analog, the cell types it contains are highly conserved. Thus "barbology" may be a useful system for studying epithelial-mesenchymal interactions, angiogenesis and lymphangiogenesis, neural pathfinding, wound healing, scar formation and other key processes in vertebrate physiology.

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Maxillary barbel taste bud development.A) 150 µm barbel. Whole-mount immunohistochemistry (anti-calretinin) shows numerous differentiated taste buds (red) on the ventral surface and distal tip of the early barbel bud. Nuclei are counterstained blue (DAPI stain). B) 400 µm barbel. Teardrop-shaped clusters of calretinin positive cells line the ventral surface. C) Magnification of the maxillary barbel tip. D) Ventral view of the mature maxillary barbel. Teardrop-shaped taste buds (white dots) are arranged in pairs along the ventral surface. Scattered solitary chemosensory cells (SCCs, white arrows) are visible between the taste bud clusters.
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pone-0008737-g006: Maxillary barbel taste bud development.A) 150 µm barbel. Whole-mount immunohistochemistry (anti-calretinin) shows numerous differentiated taste buds (red) on the ventral surface and distal tip of the early barbel bud. Nuclei are counterstained blue (DAPI stain). B) 400 µm barbel. Teardrop-shaped clusters of calretinin positive cells line the ventral surface. C) Magnification of the maxillary barbel tip. D) Ventral view of the mature maxillary barbel. Teardrop-shaped taste buds (white dots) are arranged in pairs along the ventral surface. Scattered solitary chemosensory cells (SCCs, white arrows) are visible between the taste bud clusters.

Mentions: The maxillary barbel bud appears well supplied with taste cells from the earliest stages of outgrowth, having numerous calretinin-positive cells on the ventral side and distal tip (Fig. 6A). As the barbel extends, these areas remain closely packed with onion-shaped clusters of immunoreactive cells (Fig. 6B,C); dorsally, few or no calretinin-positive cells are seen. In ventral view, the taste bud clusters of the maxillary barbel have a roughly paired arrangement (Fig. 6D), similar to the pattern of taste buds on catfish barbels [20]. At higher magnifications, two types of calretinin-positive cells are visible; cells arranged in clusters, but also the finger-like projections of solitary chemosensory cells (SCCs) [53].


Development and regeneration of the zebrafish maxillary barbel: a novel study system for vertebrate tissue growth and repair.

LeClair EE, Topczewski J - PLoS ONE (2010)

Maxillary barbel taste bud development.A) 150 µm barbel. Whole-mount immunohistochemistry (anti-calretinin) shows numerous differentiated taste buds (red) on the ventral surface and distal tip of the early barbel bud. Nuclei are counterstained blue (DAPI stain). B) 400 µm barbel. Teardrop-shaped clusters of calretinin positive cells line the ventral surface. C) Magnification of the maxillary barbel tip. D) Ventral view of the mature maxillary barbel. Teardrop-shaped taste buds (white dots) are arranged in pairs along the ventral surface. Scattered solitary chemosensory cells (SCCs, white arrows) are visible between the taste bud clusters.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2806924&req=5

pone-0008737-g006: Maxillary barbel taste bud development.A) 150 µm barbel. Whole-mount immunohistochemistry (anti-calretinin) shows numerous differentiated taste buds (red) on the ventral surface and distal tip of the early barbel bud. Nuclei are counterstained blue (DAPI stain). B) 400 µm barbel. Teardrop-shaped clusters of calretinin positive cells line the ventral surface. C) Magnification of the maxillary barbel tip. D) Ventral view of the mature maxillary barbel. Teardrop-shaped taste buds (white dots) are arranged in pairs along the ventral surface. Scattered solitary chemosensory cells (SCCs, white arrows) are visible between the taste bud clusters.
Mentions: The maxillary barbel bud appears well supplied with taste cells from the earliest stages of outgrowth, having numerous calretinin-positive cells on the ventral side and distal tip (Fig. 6A). As the barbel extends, these areas remain closely packed with onion-shaped clusters of immunoreactive cells (Fig. 6B,C); dorsally, few or no calretinin-positive cells are seen. In ventral view, the taste bud clusters of the maxillary barbel have a roughly paired arrangement (Fig. 6D), similar to the pattern of taste buds on catfish barbels [20]. At higher magnifications, two types of calretinin-positive cells are visible; cells arranged in clusters, but also the finger-like projections of solitary chemosensory cells (SCCs) [53].

Bottom Line: Barbels are integumentary sense organs found in fishes, reptiles and amphibians.Finally, we show that the maxillary barbel can regenerate after repeated injury and also in senescent fish (>2 years old).Although the teleost barbel has no human analog, the cell types it contains are highly conserved.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, DePaul University, Chicago, Illinois, United States of America. eleclair@depaul.edu

ABSTRACT

Background: Barbels are integumentary sense organs found in fishes, reptiles and amphibians. The zebrafish, Danio rerio, develops paired nasal and maxillary barbels approximately one month post fertilization. Small in diameter and optically clear, these adult appendages offer a window on the development, maintenance and function of multiple cell types including skin cells, neural-crest derived pigment cells, circulatory vessels, taste buds and sensory nerves. Importantly, barbels in other otophysan fishes (e.g., catfish) are known to regenerate; however, this capacity has not been tested in zebrafish.

Methodology/principal findings: We describe the development of the maxillary barbel in a staged series of wild type and transgenic zebrafish using light microscopy, histology and immunohistochemistry. By imaging transgenic zebrafish containing fluorescently labeled endothelial cells (Tg(fli1a:EGFP)), we demonstrate that the barbel contains a long ( approximately 2-3 mm) closed-end vessel that we interpret as a large lymphatic. The identity of this vessel was further supported by live imaging of the barbel circulation, extending recent descriptions of the lymphatic system in zebrafish. The maxillary barbel can be induced to regenerate by proximal amputation. After more than 750 experimental surgeries in which approximately 85% of the barbel's length was removed, we find that wound healing is complete within hours, followed by blastema formation ( approximately 3 days), epithelial redifferentiation (3-5 days) and appendage elongation. Maximum regrowth occurs within 2 weeks of injury. Although superficially normal, the regenerates are shorter and thicker than the contralateral controls, have abnormally organized mesenchymal cells and extracellular matrix, and contain prominent connective tissue "stumps" at the plane of section--a mode of regeneration more typical of mammalian scarring than other zebrafish appendages. Finally, we show that the maxillary barbel can regenerate after repeated injury and also in senescent fish (>2 years old).

Conclusions/significance: Although the teleost barbel has no human analog, the cell types it contains are highly conserved. Thus "barbology" may be a useful system for studying epithelial-mesenchymal interactions, angiogenesis and lymphangiogenesis, neural pathfinding, wound healing, scar formation and other key processes in vertebrate physiology.

Show MeSH
Related in: MedlinePlus