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Mechanisms of lymphatic regeneration after tissue transfer.

Yan A, Avraham T, Zampell JC, Aschen SZ, Mehrara BJ - PLoS ONE (2011)

Bottom Line: Patterns of VEGF-C expression and macrophage infiltration were temporally and spatially associated with lymphatic regeneration.When compared to mice treated with excision only, there was a 4-fold decrease in tail volumes, 2.5-fold increase in lymphatic transport by lymphoscintigraphy, 40% decrease in dermal thickness, and 54% decrease in scar index in skin-grafted animals, indicating that tissue transfer could bypass damaged lymphatics and promote rapid lymphatic regeneration.This process is temporally and spatially associated with VEGF-C expression and macrophage infiltration.

View Article: PubMed Central - PubMed

Affiliation: The Division of Plastic and Reconstructive Surgery, Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America.

ABSTRACT

Introduction: Lymphedema is the chronic swelling of an extremity that occurs commonly after lymph node resection for cancer treatment. Recent studies have demonstrated that transfer of healthy tissues can be used as a means of bypassing damaged lymphatics and ameliorating lymphedema. The purpose of these studies was to investigate the mechanisms that regulate lymphatic regeneration after tissue transfer.

Methods: Nude mice (recipients) underwent 2-mm tail skin excisions that were either left open or repaired with full-thickness skin grafts harvested from donor transgenic mice that expressed green fluorescent protein in all tissues or from LYVE-1 knockout mice. Lymphatic regeneration, expression of VEGF-C, macrophage infiltration, and potential for skin grafting to bypass damaged lymphatics were assessed.

Results: Skin grafts healed rapidly and restored lymphatic flow. Lymphatic regeneration occurred beginning at the peripheral edges of the graft, primarily from ingrowth of new lymphatic vessels originating from the recipient mouse. In addition, donor lymphatic vessels appeared to spontaneously re-anastomose with recipient vessels. Patterns of VEGF-C expression and macrophage infiltration were temporally and spatially associated with lymphatic regeneration. When compared to mice treated with excision only, there was a 4-fold decrease in tail volumes, 2.5-fold increase in lymphatic transport by lymphoscintigraphy, 40% decrease in dermal thickness, and 54% decrease in scar index in skin-grafted animals, indicating that tissue transfer could bypass damaged lymphatics and promote rapid lymphatic regeneration.

Conclusions: Our studies suggest that lymphatic regeneration after tissue transfer occurs by ingrowth of lymphatic vessels and spontaneous re-connection of existing lymphatics. This process is temporally and spatially associated with VEGF-C expression and macrophage infiltration. Finally, tissue transfer can be used to bypass damaged lymphatics and promote rapid lymphatic regeneration.

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Related in: MedlinePlus

Lymphatic regeneration after tissue transfer is associated with infiltration of macrophages.A. F4/80 localization in skin-grafted tails 2 weeks after surgery. Representative low power (2x; upper panel) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse-tail are shown. High power (20x) views of the distal and proximal junctions between recipient tissues and skin grafts are shown below. Dashed box delineates skin-grafted area. B. F4/80 localization in skin-grafted tails 6 weeks after surgery. Representative low power (2x; upper panel) and high power (20x) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse tails are shown. Dashed box delineates skin-grafted area. Note small amount of wound/skin graft contracture after repair. C. Cell counts per high power field of F4/80+ cells in various regions of the tail 2 and 6 weeks after surgery. Cell counts are means ± SD of at least 4 high power fields/mouse/time point. At least 6 mice were analyzed in each group (*p<0.05).
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pone-0017201-g005: Lymphatic regeneration after tissue transfer is associated with infiltration of macrophages.A. F4/80 localization in skin-grafted tails 2 weeks after surgery. Representative low power (2x; upper panel) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse-tail are shown. High power (20x) views of the distal and proximal junctions between recipient tissues and skin grafts are shown below. Dashed box delineates skin-grafted area. B. F4/80 localization in skin-grafted tails 6 weeks after surgery. Representative low power (2x; upper panel) and high power (20x) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse tails are shown. Dashed box delineates skin-grafted area. Note small amount of wound/skin graft contracture after repair. C. Cell counts per high power field of F4/80+ cells in various regions of the tail 2 and 6 weeks after surgery. Cell counts are means ± SD of at least 4 high power fields/mouse/time point. At least 6 mice were analyzed in each group (*p<0.05).

Mentions: Macrophages are critical cells that regulate wound repair and produce VEGF-C during lymphatic regeneration in the mouse tail. In addition, they are thought to directly contribute to lymphangiogenesis by trans-differentiating into lymphatic endothelial cells.[23] Immunohistochemical staining with F4/80 revealed a similar expression pattern as that of VEGF-C with a large number of F4/80+ cells localized at the periphery of the graft at the 2 week time point (Figures 5A, C). Similar to our findings of VEGF-C expression, the greatest number of macrophages was noted at the distal margin of the wound (44±7 in distal portion vs. 16±5 or 20±5 in middle or proximal areas; p<0.05). Co-localization of F4/80 and LYVE-1 suggested that some of the newly formed lymphatic channels in the skin graft may have formed as a result of trans-differentiation of macrophages into lymphatic endothelial cells (Figure 6). In addition, scattered, isolated F4/80+/LYVE-1+ cells that had not formed tubules could be seen within the wound sections. Newly formed lymphatics with trans-differentiating macrophages were recipient-derived since they also expressed LYVE-1. By 6 weeks, the number of macrophages had decreased in the distal margin of the graft and a more uniform distribution was noted throughout the grafted area (Figures 5B-C). In addition, we could not find any F4/80+/LYVE-1+ vessels at this time point indicating loss of F4/80 expression with vessel remodeling (not shown).


Mechanisms of lymphatic regeneration after tissue transfer.

Yan A, Avraham T, Zampell JC, Aschen SZ, Mehrara BJ - PLoS ONE (2011)

Lymphatic regeneration after tissue transfer is associated with infiltration of macrophages.A. F4/80 localization in skin-grafted tails 2 weeks after surgery. Representative low power (2x; upper panel) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse-tail are shown. High power (20x) views of the distal and proximal junctions between recipient tissues and skin grafts are shown below. Dashed box delineates skin-grafted area. B. F4/80 localization in skin-grafted tails 6 weeks after surgery. Representative low power (2x; upper panel) and high power (20x) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse tails are shown. Dashed box delineates skin-grafted area. Note small amount of wound/skin graft contracture after repair. C. Cell counts per high power field of F4/80+ cells in various regions of the tail 2 and 6 weeks after surgery. Cell counts are means ± SD of at least 4 high power fields/mouse/time point. At least 6 mice were analyzed in each group (*p<0.05).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040774&req=5

pone-0017201-g005: Lymphatic regeneration after tissue transfer is associated with infiltration of macrophages.A. F4/80 localization in skin-grafted tails 2 weeks after surgery. Representative low power (2x; upper panel) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse-tail are shown. High power (20x) views of the distal and proximal junctions between recipient tissues and skin grafts are shown below. Dashed box delineates skin-grafted area. B. F4/80 localization in skin-grafted tails 6 weeks after surgery. Representative low power (2x; upper panel) and high power (20x) photomicrographs encompassing the skin-grafted area and distal/proximal portions of the recipient mouse tails are shown. Dashed box delineates skin-grafted area. Note small amount of wound/skin graft contracture after repair. C. Cell counts per high power field of F4/80+ cells in various regions of the tail 2 and 6 weeks after surgery. Cell counts are means ± SD of at least 4 high power fields/mouse/time point. At least 6 mice were analyzed in each group (*p<0.05).
Mentions: Macrophages are critical cells that regulate wound repair and produce VEGF-C during lymphatic regeneration in the mouse tail. In addition, they are thought to directly contribute to lymphangiogenesis by trans-differentiating into lymphatic endothelial cells.[23] Immunohistochemical staining with F4/80 revealed a similar expression pattern as that of VEGF-C with a large number of F4/80+ cells localized at the periphery of the graft at the 2 week time point (Figures 5A, C). Similar to our findings of VEGF-C expression, the greatest number of macrophages was noted at the distal margin of the wound (44±7 in distal portion vs. 16±5 or 20±5 in middle or proximal areas; p<0.05). Co-localization of F4/80 and LYVE-1 suggested that some of the newly formed lymphatic channels in the skin graft may have formed as a result of trans-differentiation of macrophages into lymphatic endothelial cells (Figure 6). In addition, scattered, isolated F4/80+/LYVE-1+ cells that had not formed tubules could be seen within the wound sections. Newly formed lymphatics with trans-differentiating macrophages were recipient-derived since they also expressed LYVE-1. By 6 weeks, the number of macrophages had decreased in the distal margin of the graft and a more uniform distribution was noted throughout the grafted area (Figures 5B-C). In addition, we could not find any F4/80+/LYVE-1+ vessels at this time point indicating loss of F4/80 expression with vessel remodeling (not shown).

Bottom Line: Patterns of VEGF-C expression and macrophage infiltration were temporally and spatially associated with lymphatic regeneration.When compared to mice treated with excision only, there was a 4-fold decrease in tail volumes, 2.5-fold increase in lymphatic transport by lymphoscintigraphy, 40% decrease in dermal thickness, and 54% decrease in scar index in skin-grafted animals, indicating that tissue transfer could bypass damaged lymphatics and promote rapid lymphatic regeneration.This process is temporally and spatially associated with VEGF-C expression and macrophage infiltration.

View Article: PubMed Central - PubMed

Affiliation: The Division of Plastic and Reconstructive Surgery, Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America.

ABSTRACT

Introduction: Lymphedema is the chronic swelling of an extremity that occurs commonly after lymph node resection for cancer treatment. Recent studies have demonstrated that transfer of healthy tissues can be used as a means of bypassing damaged lymphatics and ameliorating lymphedema. The purpose of these studies was to investigate the mechanisms that regulate lymphatic regeneration after tissue transfer.

Methods: Nude mice (recipients) underwent 2-mm tail skin excisions that were either left open or repaired with full-thickness skin grafts harvested from donor transgenic mice that expressed green fluorescent protein in all tissues or from LYVE-1 knockout mice. Lymphatic regeneration, expression of VEGF-C, macrophage infiltration, and potential for skin grafting to bypass damaged lymphatics were assessed.

Results: Skin grafts healed rapidly and restored lymphatic flow. Lymphatic regeneration occurred beginning at the peripheral edges of the graft, primarily from ingrowth of new lymphatic vessels originating from the recipient mouse. In addition, donor lymphatic vessels appeared to spontaneously re-anastomose with recipient vessels. Patterns of VEGF-C expression and macrophage infiltration were temporally and spatially associated with lymphatic regeneration. When compared to mice treated with excision only, there was a 4-fold decrease in tail volumes, 2.5-fold increase in lymphatic transport by lymphoscintigraphy, 40% decrease in dermal thickness, and 54% decrease in scar index in skin-grafted animals, indicating that tissue transfer could bypass damaged lymphatics and promote rapid lymphatic regeneration.

Conclusions: Our studies suggest that lymphatic regeneration after tissue transfer occurs by ingrowth of lymphatic vessels and spontaneous re-connection of existing lymphatics. This process is temporally and spatially associated with VEGF-C expression and macrophage infiltration. Finally, tissue transfer can be used to bypass damaged lymphatics and promote rapid lymphatic regeneration.

Show MeSH
Related in: MedlinePlus