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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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Scanning electron microscopy of early barbel regenerates.A, B) Immediately after amputation (zero hours post surgery, or 0 hps), the barbel stump is an open wound exposing the central core. A) Barbel stump in lateral view; proximal is to the left. B) End-on view of the same specimen. C, D) Two separate specimens collected at three hours post surgery (3 dps). The adjacent epithelium has closed the wound completely. Note the “purse string” lines of contraction within the epithelial sheet (C). Erythrocytes, dying cells, and matrix debris adhere to the distal surface (D). E,F) After 72 hours, the barbel stump swells distally, becoming bulbous (E). The tip epithelium carries newly differentiating taste bud hillocks, complete with protruding apical villi (F, magnified from E). G,H) By 7 days post surgery (7 dps), the maxillary barbel is a smaller version of the original appendage. Several millimeters long, it has a tapered distal end that carries a dense cluster of taste buds (H, magnified from G).
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pone-0008737-g008: Scanning electron microscopy of early barbel regenerates.A, B) Immediately after amputation (zero hours post surgery, or 0 hps), the barbel stump is an open wound exposing the central core. A) Barbel stump in lateral view; proximal is to the left. B) End-on view of the same specimen. C, D) Two separate specimens collected at three hours post surgery (3 dps). The adjacent epithelium has closed the wound completely. Note the “purse string” lines of contraction within the epithelial sheet (C). Erythrocytes, dying cells, and matrix debris adhere to the distal surface (D). E,F) After 72 hours, the barbel stump swells distally, becoming bulbous (E). The tip epithelium carries newly differentiating taste bud hillocks, complete with protruding apical villi (F, magnified from E). G,H) By 7 days post surgery (7 dps), the maxillary barbel is a smaller version of the original appendage. Several millimeters long, it has a tapered distal end that carries a dense cluster of taste buds (H, magnified from G).

Mentions: Barbels fixed immediately after surgery showed a ragged, cut surface exposing blood-filled sinuses and the central rod (Fig. 8A,B). After 3 hours, however, these wounds were completely closed although covered with dead or dying epithelial cells, scattered erythrocytes and cell debris (Fig. 8C,D). Sheets of skin appeared to converge medially and pucker over the wound, suggesting a “purse-string” action similar to that observed in SEMs of Xenopus wound closure [54]. One day after surgery, the distal surface of the regenerate was smooth and rounded, with no dead cells or surface debris (not shown). The length of the barbel was not increased, and the skin at the distal end showed no special epithelial characteristics. By 3 days post surgery the distal end of the barbel shaft became enlarged and bulbous, with several incipient taste bud hillocks at the distal tip (Fig. 8E). Each hillock was formed by the elevation of 3–4 epithelial cells topped by a crown of apical cilia (Fig. 8F). Seven days after surgery, regenerated barbels showed significant increases in length, having grown well past the original plane of section. Each carried at its distal end a cluster of 8–10 differentiated taste buds (Fig. 8G,H).


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)

Scanning electron microscopy of early barbel regenerates.A, B) Immediately after amputation (zero hours post surgery, or 0 hps), the barbel stump is an open wound exposing the central core. A) Barbel stump in lateral view; proximal is to the left. B) End-on view of the same specimen. C, D) Two separate specimens collected at three hours post surgery (3 dps). The adjacent epithelium has closed the wound completely. Note the “purse string” lines of contraction within the epithelial sheet (C). Erythrocytes, dying cells, and matrix debris adhere to the distal surface (D). E,F) After 72 hours, the barbel stump swells distally, becoming bulbous (E). The tip epithelium carries newly differentiating taste bud hillocks, complete with protruding apical villi (F, magnified from E). G,H) By 7 days post surgery (7 dps), the maxillary barbel is a smaller version of the original appendage. Several millimeters long, it has a tapered distal end that carries a dense cluster of taste buds (H, magnified from G).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0008737-g008: Scanning electron microscopy of early barbel regenerates.A, B) Immediately after amputation (zero hours post surgery, or 0 hps), the barbel stump is an open wound exposing the central core. A) Barbel stump in lateral view; proximal is to the left. B) End-on view of the same specimen. C, D) Two separate specimens collected at three hours post surgery (3 dps). The adjacent epithelium has closed the wound completely. Note the “purse string” lines of contraction within the epithelial sheet (C). Erythrocytes, dying cells, and matrix debris adhere to the distal surface (D). E,F) After 72 hours, the barbel stump swells distally, becoming bulbous (E). The tip epithelium carries newly differentiating taste bud hillocks, complete with protruding apical villi (F, magnified from E). G,H) By 7 days post surgery (7 dps), the maxillary barbel is a smaller version of the original appendage. Several millimeters long, it has a tapered distal end that carries a dense cluster of taste buds (H, magnified from G).
Mentions: Barbels fixed immediately after surgery showed a ragged, cut surface exposing blood-filled sinuses and the central rod (Fig. 8A,B). After 3 hours, however, these wounds were completely closed although covered with dead or dying epithelial cells, scattered erythrocytes and cell debris (Fig. 8C,D). Sheets of skin appeared to converge medially and pucker over the wound, suggesting a “purse-string” action similar to that observed in SEMs of Xenopus wound closure [54]. One day after surgery, the distal surface of the regenerate was smooth and rounded, with no dead cells or surface debris (not shown). The length of the barbel was not increased, and the skin at the distal end showed no special epithelial characteristics. By 3 days post surgery the distal end of the barbel shaft became enlarged and bulbous, with several incipient taste bud hillocks at the distal tip (Fig. 8E). Each hillock was formed by the elevation of 3–4 epithelial cells topped by a crown of apical cilia (Fig. 8F). Seven days after surgery, regenerated barbels showed significant increases in length, having grown well past the original plane of section. Each carried at its distal end a cluster of 8–10 differentiated taste buds (Fig. 8G,H).

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