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Kruppel-like factor KLF4 facilitates cutaneous wound healing by promoting fibrocyte generation from myeloid-derived suppressor cells.

Ou L, Shi Y, Dong W, Liu C, Schmidt TJ, Nagarkatti P, Nagarkatti M, Fan D, Ai W - J. Invest. Dermatol. (2015)

Bottom Line: Myeloid-derived suppressor cells (MDSCs) accumulate as a result of inflammation and promote cutaneous wound healing by mechanisms that are not fully understood.Recently, MDSCs have been shown to differentiate into fibrocytes, which serve as emerging effector cells that enhance cell proliferation in wound healing.In the current study, by using full-thickness and PU mouse models, we found that Kruppel-like factor 4 (KLF4) deficiency resulted in decreased accumulation of MDSCs and fibrocytes, and wound healing was significantly delayed.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, South Carolina, USA [2] Department of Biopharmaceuticals, School of Biotechnology, Southern Medical University, Guangzhou, People's Republic of China.

ABSTRACT
Pressure ulcers (PUs) are serious skin injuries whereby the wound healing process is frequently stalled in the inflammatory phase. Myeloid-derived suppressor cells (MDSCs) accumulate as a result of inflammation and promote cutaneous wound healing by mechanisms that are not fully understood. Recently, MDSCs have been shown to differentiate into fibrocytes, which serve as emerging effector cells that enhance cell proliferation in wound healing. We postulate that in wound healing MDSCs not only execute their immunosuppressive function to regulate inflammation but also stimulate cell proliferation once they differentiate into fibrocytes. In the current study, by using full-thickness and PU mouse models, we found that Kruppel-like factor 4 (KLF4) deficiency resulted in decreased accumulation of MDSCs and fibrocytes, and wound healing was significantly delayed. Conversely, KLF4 activation by the plant-derived product Mexicanin I increased the number of MDSCs and fibrocytes and accelerated the wound healing. Collectively, our study revealed a previously unreported function of MDSCs in cutaneous wound healing and identified Mexicanin I as a potential agent to accelerate PU wound healing.

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Delayed wound healing in bone marrow KLF4 knockout mice and compromised accumulation of CCR2+MDSCs and fibrocytes(a). Chimeric mice receiving bone marrow cells from Rosa26CreER/KLF4(flox)/β-actin-EGFP donor mice were used. Quantification of the wound size in each group of mice is shown (n=10). (b). Single cells from the skin wound were gated by EGFP. They were examined by CD11b and Ly6G antibodies, followed by further analysis using a CCR2 antibody. Representative contour plots in each group are shown. (c). Similar to (b) except COL1A1, CD45, and CD11b antibodies were used to analyze the fibrocytes. (d). Representative immunofluorescent staining of the wounds with α-SMA and COL1A1 antibodies. Yellow arrows indicate EGFP/α-SMA or EGFP/COL1A1 co-expressing cells (Scale bars: 50 μm).
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Figure 2: Delayed wound healing in bone marrow KLF4 knockout mice and compromised accumulation of CCR2+MDSCs and fibrocytes(a). Chimeric mice receiving bone marrow cells from Rosa26CreER/KLF4(flox)/β-actin-EGFP donor mice were used. Quantification of the wound size in each group of mice is shown (n=10). (b). Single cells from the skin wound were gated by EGFP. They were examined by CD11b and Ly6G antibodies, followed by further analysis using a CCR2 antibody. Representative contour plots in each group are shown. (c). Similar to (b) except COL1A1, CD45, and CD11b antibodies were used to analyze the fibrocytes. (d). Representative immunofluorescent staining of the wounds with α-SMA and COL1A1 antibodies. Yellow arrows indicate EGFP/α-SMA or EGFP/COL1A1 co-expressing cells (Scale bars: 50 μm).

Mentions: To test the possibility that the KLF4 deficiency-induced delay of cutaneous wound healing is attributable to bone marrow cells, we performed full-thickness wound healing experiments using chimeric mice. These mice were generated by transplanting bone marrow cells from RosaCre26ER/KLF4(flox)/β-actin-EGFP triple transgenic mice into wild type C57BL/6 mice. The percentage of EGFP positivity in circulating leukocytes of the chimeric mice was more than 90% as assessed by flow cytometry in tamoxifen-induced mice (data not shown), suggesting a successful bone marrow reconstitution. The wound-closure kinetics showed that wound healing was significantly delayed in the bone marrow KLF4−/− group (Figure 2a). In addition, while the total population of MDSCs in BM, spleen and the skin wound site was not significantly different before and after KLF4 bone marrow knockout by tamoxifen induction (data not shown), CCR2+ MDSCs in the skin wound site decreased from 3.29±0.45% in the BM KLF4+/+ group to 1.61±0.20% in the BM KLF4−/− group (p<0.05, Figure 2b).


Kruppel-like factor KLF4 facilitates cutaneous wound healing by promoting fibrocyte generation from myeloid-derived suppressor cells.

Ou L, Shi Y, Dong W, Liu C, Schmidt TJ, Nagarkatti P, Nagarkatti M, Fan D, Ai W - J. Invest. Dermatol. (2015)

Delayed wound healing in bone marrow KLF4 knockout mice and compromised accumulation of CCR2+MDSCs and fibrocytes(a). Chimeric mice receiving bone marrow cells from Rosa26CreER/KLF4(flox)/β-actin-EGFP donor mice were used. Quantification of the wound size in each group of mice is shown (n=10). (b). Single cells from the skin wound were gated by EGFP. They were examined by CD11b and Ly6G antibodies, followed by further analysis using a CCR2 antibody. Representative contour plots in each group are shown. (c). Similar to (b) except COL1A1, CD45, and CD11b antibodies were used to analyze the fibrocytes. (d). Representative immunofluorescent staining of the wounds with α-SMA and COL1A1 antibodies. Yellow arrows indicate EGFP/α-SMA or EGFP/COL1A1 co-expressing cells (Scale bars: 50 μm).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4402119&req=5

Figure 2: Delayed wound healing in bone marrow KLF4 knockout mice and compromised accumulation of CCR2+MDSCs and fibrocytes(a). Chimeric mice receiving bone marrow cells from Rosa26CreER/KLF4(flox)/β-actin-EGFP donor mice were used. Quantification of the wound size in each group of mice is shown (n=10). (b). Single cells from the skin wound were gated by EGFP. They were examined by CD11b and Ly6G antibodies, followed by further analysis using a CCR2 antibody. Representative contour plots in each group are shown. (c). Similar to (b) except COL1A1, CD45, and CD11b antibodies were used to analyze the fibrocytes. (d). Representative immunofluorescent staining of the wounds with α-SMA and COL1A1 antibodies. Yellow arrows indicate EGFP/α-SMA or EGFP/COL1A1 co-expressing cells (Scale bars: 50 μm).
Mentions: To test the possibility that the KLF4 deficiency-induced delay of cutaneous wound healing is attributable to bone marrow cells, we performed full-thickness wound healing experiments using chimeric mice. These mice were generated by transplanting bone marrow cells from RosaCre26ER/KLF4(flox)/β-actin-EGFP triple transgenic mice into wild type C57BL/6 mice. The percentage of EGFP positivity in circulating leukocytes of the chimeric mice was more than 90% as assessed by flow cytometry in tamoxifen-induced mice (data not shown), suggesting a successful bone marrow reconstitution. The wound-closure kinetics showed that wound healing was significantly delayed in the bone marrow KLF4−/− group (Figure 2a). In addition, while the total population of MDSCs in BM, spleen and the skin wound site was not significantly different before and after KLF4 bone marrow knockout by tamoxifen induction (data not shown), CCR2+ MDSCs in the skin wound site decreased from 3.29±0.45% in the BM KLF4+/+ group to 1.61±0.20% in the BM KLF4−/− group (p<0.05, Figure 2b).

Bottom Line: Myeloid-derived suppressor cells (MDSCs) accumulate as a result of inflammation and promote cutaneous wound healing by mechanisms that are not fully understood.Recently, MDSCs have been shown to differentiate into fibrocytes, which serve as emerging effector cells that enhance cell proliferation in wound healing.In the current study, by using full-thickness and PU mouse models, we found that Kruppel-like factor 4 (KLF4) deficiency resulted in decreased accumulation of MDSCs and fibrocytes, and wound healing was significantly delayed.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, South Carolina, USA [2] Department of Biopharmaceuticals, School of Biotechnology, Southern Medical University, Guangzhou, People's Republic of China.

ABSTRACT
Pressure ulcers (PUs) are serious skin injuries whereby the wound healing process is frequently stalled in the inflammatory phase. Myeloid-derived suppressor cells (MDSCs) accumulate as a result of inflammation and promote cutaneous wound healing by mechanisms that are not fully understood. Recently, MDSCs have been shown to differentiate into fibrocytes, which serve as emerging effector cells that enhance cell proliferation in wound healing. We postulate that in wound healing MDSCs not only execute their immunosuppressive function to regulate inflammation but also stimulate cell proliferation once they differentiate into fibrocytes. In the current study, by using full-thickness and PU mouse models, we found that Kruppel-like factor 4 (KLF4) deficiency resulted in decreased accumulation of MDSCs and fibrocytes, and wound healing was significantly delayed. Conversely, KLF4 activation by the plant-derived product Mexicanin I increased the number of MDSCs and fibrocytes and accelerated the wound healing. Collectively, our study revealed a previously unreported function of MDSCs in cutaneous wound healing and identified Mexicanin I as a potential agent to accelerate PU wound healing.

Show MeSH
Related in: MedlinePlus