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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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Repeated amputation can induce secondary regeneration.A) Two maxillary barbels regenerated from the same stump. The original barbel (not shown) was amputated at site 1 and the stump allowed to regenerate for one month. The resulting appendage (primary regenerate, top) was then amputated again slightly distal to the first amputation plane (site 2). A secondary regenerate (bottom) grew that was similar in size, shape and pigmentation to the primary regenerate. B) A magnification of the two surgical sites in A. Primary and secondary scars are visible approximately 0.5 mm apart. Note that the epithelial surface and melanophore patterning are largely normal. C) A secondary regenerate with more extreme scarring and swelling at the primary (1) and secondary (2) surgical sites. D–E) Failure of secondary regeneration. Secondary regenerates often failed to grow, elongating either slightly (D) or not at all (E) past the secondary surgical site (2).
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pone-0008737-g012: Repeated amputation can induce secondary regeneration.A) Two maxillary barbels regenerated from the same stump. The original barbel (not shown) was amputated at site 1 and the stump allowed to regenerate for one month. The resulting appendage (primary regenerate, top) was then amputated again slightly distal to the first amputation plane (site 2). A secondary regenerate (bottom) grew that was similar in size, shape and pigmentation to the primary regenerate. B) A magnification of the two surgical sites in A. Primary and secondary scars are visible approximately 0.5 mm apart. Note that the epithelial surface and melanophore patterning are largely normal. C) A secondary regenerate with more extreme scarring and swelling at the primary (1) and secondary (2) surgical sites. D–E) Failure of secondary regeneration. Secondary regenerates often failed to grow, elongating either slightly (D) or not at all (E) past the secondary surgical site (2).

Mentions: Of the 78 fish challenged to undergo secondary regeneration, 66% (57/78) grew back a secondary maxillary barbel. Large secondary regenerates were patterned normally in terms of pigment cells, gross organization of the vasculature and taste bud distribution, and could be of comparable size to the primary regenerates (Fig. 12A). Notably, the internal scarring seen in primary regenerates was repeated in the secondary regenerates. In most cases, two separate scars were observed, one distal to the first (Fig. 12 B,C).


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)

Repeated amputation can induce secondary regeneration.A) Two maxillary barbels regenerated from the same stump. The original barbel (not shown) was amputated at site 1 and the stump allowed to regenerate for one month. The resulting appendage (primary regenerate, top) was then amputated again slightly distal to the first amputation plane (site 2). A secondary regenerate (bottom) grew that was similar in size, shape and pigmentation to the primary regenerate. B) A magnification of the two surgical sites in A. Primary and secondary scars are visible approximately 0.5 mm apart. Note that the epithelial surface and melanophore patterning are largely normal. C) A secondary regenerate with more extreme scarring and swelling at the primary (1) and secondary (2) surgical sites. D–E) Failure of secondary regeneration. Secondary regenerates often failed to grow, elongating either slightly (D) or not at all (E) past the secondary surgical site (2).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0008737-g012: Repeated amputation can induce secondary regeneration.A) Two maxillary barbels regenerated from the same stump. The original barbel (not shown) was amputated at site 1 and the stump allowed to regenerate for one month. The resulting appendage (primary regenerate, top) was then amputated again slightly distal to the first amputation plane (site 2). A secondary regenerate (bottom) grew that was similar in size, shape and pigmentation to the primary regenerate. B) A magnification of the two surgical sites in A. Primary and secondary scars are visible approximately 0.5 mm apart. Note that the epithelial surface and melanophore patterning are largely normal. C) A secondary regenerate with more extreme scarring and swelling at the primary (1) and secondary (2) surgical sites. D–E) Failure of secondary regeneration. Secondary regenerates often failed to grow, elongating either slightly (D) or not at all (E) past the secondary surgical site (2).
Mentions: Of the 78 fish challenged to undergo secondary regeneration, 66% (57/78) grew back a secondary maxillary barbel. Large secondary regenerates were patterned normally in terms of pigment cells, gross organization of the vasculature and taste bud distribution, and could be of comparable size to the primary regenerates (Fig. 12A). Notably, the internal scarring seen in primary regenerates was repeated in the secondary regenerates. In most cases, two separate scars were observed, one distal to the first (Fig. 12 B,C).

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