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journal homepage: www.JournalofSurgicalResearch.com

CXCL12/CXCR4 axis promotes mesenchymal stem cellmobilization to burn wounds and contributes to wound repair

Changjiang Hu, PhD,a,b,1 Xin Yong, PhD,a,b,1 Changzhu Li, PhD,a,* Muhan Lu, PhD,b

Dengqun Liu, PhD,c Lin Chen, PhD,b Jiongyu Hu, PhD,a Miao Teng, PhD,a

Dongxia Zhang, PhD,a Yahan Fan, PhD,b and Guangping Liang, PhDa,**a Institute of Burn Research, Southwest Hospital, Third Military Medical University, Chongqing, P.R. Chinab Institute of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, P.R. Chinac Institute of Combined Injury, State Key Laboratory of Trauma, Burn and Combined Injury, College of Preventive Medicine, Third Military

Medical University, Chongqing, P.R. China

a r t i c l e i n f o

Article history:

Received 19 September 2012

Received in revised form

16 December 2012

Accepted 10 January 2013

Available online xxx

Keywords:

Bone marrowederived

mesenchymal stem cells

Burn wound

CXCL12

CXCR4

* Corresponding author. Institute of Burn ReTel.: þ86 023 68754149; fax: þ86 023 6546039** Corresponding author. Institute of Burn ReTel.: þ86 023 68754149; fax: þ86 023 6546039

E-mail addresses: changzhu.li@163.com (1 Changjiang Hu and Xin Yong contributed

0022-4804/$ e see front matter ª 2013 Elsevhttp://dx.doi.org/10.1016/j.jss.2013.01.019

a b s t r a c t

Background: Bone marrowederived mesenchymal stem cells (BM-MSCs) play a crucial role

in tissue repair. Their role in thermal burn wound regeneration and the relevant mecha-

nism, however, is rarely studied.

Methods: BM-MSCs from green fluorescent protein transgenic male mice were transfused to

irradiated recipient female C57BL/6 mice. Twenty-one days later, the female mice were

inflicted with burn wounds. The size of the burned area was measured by an in vivo fluo-

rescence imaging system, and BM-MSC chemotaxis and epithelialization were estimated by

fluorescence in situ hybridization and immunofluorescence technology. The expression of

CXCL12 and CXCR4 in the wound margin was detected by enzyme-linked immunosorbent

assay and immunohistochemistry. The importance of CXCL12/CXCR4 signaling in BM-MSC

chemotaxis was further estimated by blocking CXCR4 in vivo and in vitro.

Results: In vivo imaging results showed that BM-MSCs migrated to the injured margins.

Fluorescence in situ hybridization and immunofluorescence technology revealed that Y

chromosomeepositive cells derived from green fluorescent protein transgenic mice were

detected to be colocalized with keratin protein. Enzyme-linked immunosorbent assay

revealed increased levels of CXCL12 and CXCR4 protein in the wound sites of BM-MSC-

treated chimeric mice after burn. Immunohistochemistry also disclosed that CXCL12

levels were elevated at postburn day 7 compared with day 0. Furthermore, pretreatment of

the BM-MSCs with the CXCR4 antagonist AMD3100 significantly inhibited the mobilization

of BM-MSCs in vitro and in vivo, which attenuated wound closure.

Conclusion: BM-MSC migration to the burned margins promotes the epithelialization of the

wound, and mobilization of BM-MSCs is mediated by CXCL12/CXCR4 signaling.

ª 2013 Elsevier Inc. All rights reserved.

search, Southwest Hospital, Third Military Medical University, Chongqing 400038, China.8.search, Southwest Hospital, Third Military Medical University, Chongqing 400038, China.8.C. Li), gpl12@yahoo.cn (G. Liang).equally to this study.

ier Inc. All rights reserved.

j o u rn a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8e2

1. Introduction 2. Materials and methods

Bone marrowederived mesenchymal stem cells (BM-MSCs)

are a subset of nonhematopoietic cells in bone marrow char-

acterized by their capacity for self-renewal and differentiation

intomultiple cell types, including osteoblasts, adipocytes, and

chondrocytes [1]. It has been widely accepted that tissue

repair of injuries is primarily advanced by bone marrow stem

cells that migrate to the site of damage and undergo differ-

entiation, promoting structural and functional repair [2].

Studies have demonstrated that intravenous delivery of BM-

MSCs leads to their migration to the injured site of bone or

cartilage fracture [3], myocardial infarction [4], and ischemic

cerebral injury [5].

BM-MSCs can mobilize and migrate to target sites to

participate in tissue repair and regeneration. Many studies

have focused on the mechanisms of how BM-MSCs migrate to

injured tissues, and some key molecules involved in several

signaling pathways have been reported to participate in this

process, such as the CXCL12/CXCR4 pathway, whichmediates

BM-MSC migration and enhances wound healing, damage

repair, and regeneration. CXCL12 (also known as SDF-1) is

a member of a large family that promotes chemotaxis. It was

first identified as a lymphocyte- and monocyte-specific che-

moattractant under both normal and inflammatory condi-

tions [6]. Wynn et al. demonstrated that CXCR4, the receptor

for CXCL12, was highly expressed in BM-MSCs and that the

CXCL12/CXCR4 axis was involved in the migration of BM-

MSCs [7]. The CXCR4 antagonist significantly inhibited the

chemotaxis of BM-MSCs to CXCL12 [8]. In addition, the

CXCL12/CXCR4 pathwaywas shown tomediate the homing of

transplanted BM-MSCs to injured sites in the brain, and it was

shown that BM-MSCs migrated toward a CXCL12 gradient in

a dose-dependent manner [5]. These studies suggest that the

CXCL12/CXCR4 axis is required for BM-MSC migration.

Burn injuries, which are characterized by heat-induced

tissue coagulation at the time of injury, constitute a world-

wide public health problem [9]. Compared with incisional

wounds, burn wounds heal more slowly because of edema,

extensive necrosis, and relative hypoxia of the burn wound

[10]. Furthermore, it has been well established that large burn

injuries induce systemic immune dysfunction, which

endangers the patient’s life [11,12]. Advances in the field of

burn wound healing remain limited but are necessary. BM-

MSCs have shown the capacity to accelerate the healing

process of incisional wounds [13]. However, to date, there

have been few studies regarding the role of BM-MSCs in the

repair process of burns, and the related mechanism is even

less understood. In the present study, we investigated the

detailed localization and effects of BM-MSCs in burn wound

healing using a deep burn model of chimeric C57BL/6 mice

and examined the role of CXCL12/CXCR4 signaling in BM-

MSC migration. Our results showed that the transplanted

BM-MSCs primarily distributed in the hair follicles and

epidermis of the wound margin, accelerating the epithelial-

ization of the wound. The CXCL12/CXCR4 axis promoted BM-

MSC mobilization to burn wounds, which suggests that the

CXCL12/CXCR4 axis would be a novel therapeutic target for

the treatment of burn wounds.

2.1. Irradiation and transplantation

All animal experiments were approved by the Animal Care

and Use Committee of the Third Military Medical University

and were performed in compliance with the “Guide for the

Care and Use of Laboratory Animals” published by the

National Institutes of Health. Eight-week-old female C57BL/6

mice were obtained from the Third Military Medical Univer-

sity. They were housed in autoclaved cages and treated with

antibiotics (280 mg erythromycin and 320 mg gentamicin

sulfate per liter of deionized drinking water) for 10 d before

irradiation and 2 wk after irradiation. Recipient mice were

exposed to 10 Gy whole-body irradiation using a Cobalt-60

source (Theratron-780 model; MDS Nordion, Ottawa, ON,

Canada), which is a method that has been widely used to

destroy marrow [14,15]. Four hours after irradiation, 1 � 106

BM-MSCs from male green fluorescent protein (GFP) trans-

genic C57BL/6 mice (Cyagen Biosciences, Guangzhou, China)

were injected into the tail vein of female recipient mice.

2.2. Quantitative real-time polymerase chain reaction(RT-PCR) for confirmation of the chimeric model

Mouse chimerismwas evaluatedbydetecting themale-specific

gene Sry in the peripheral blood harvested from recipient mice

20 d after BM-MSC transplantation. The expression of Sry from

theperipheral bloodofmalemicewasusedasapositive control

and that from wild-type female mice as a negative control.

Genomic DNA was extracted from mouse blood with the

DNeasy Blood and Tissue Kit (Tiangen, Beijing, China) accord-

ing to the manufacturer’s instructions. Quantitative real-time

PCR was performed as described previously [16]. The primer

sequences were as follows: Sry (forward), 50-GGAGGCACAGAGATTGAAGA-30; Sry (reverse), 50-ACTCCAGTCTTGCCTGTATG;GAPDH (forward), 50-ACCCATCAC CATCTTCCAGGAG-30; and

GAPDH (reverse), 50-GAAGGGGCGGAGATGATGA C-30.

2.3. Animal burn model

A burn injury model was established 21 d after BM-MSC

transplantation, as described previously [17]. Briefly, the mice

were anesthetized by intraperitoneal injection of pentobarbital

sodium(75mg/kg). Then, a total of 1.75 cm2bodysurfaceareaof

the mouse dorsum was exposed to a 100�C water bath for 8 s.

On days 1, 3, 7, 14, 21, and 28, the entire wound area, including

the adjacent 2-mm skin margins, was collected for further

analysis of fluorescence in situ hybridization (FISH), immuno-

fluorescence (IF), enzyme-linked immunosorbent assay

(ELISA), and immunohistochemistry (IHC).

2.4. In vivo fluorescence imaging

In vivo fluorescence imaging was performed on days 1, 3, 7, 14,

21, and 28 post wounding using a Maestro In Vivo Imaging

System (Cambridge Research & Instrumentation, Boston, MA).

The excitation filter for GFP was 445e490 nm. The tunable

j o u r n a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8 e3

filter was automatically stepped in 10-nm increments from

500e750 nm with an exposure time of 300 ms for the images

captured at each wavelength. The animals were placed on the

microscope stage, and then the images were taken in both

true color and pseudo color. The measurements of the burn

area were analyzed using the Maestro 2.10.0 software, which

is part of the Maestro In Vivo Imaging System. Measurements

of the wound area were taken three times by two independent

experimenters.

2.5. FISH and IF analysis

The FISH and IF analyses were performed according to the

methods described by Sato et al. [18]. In brief, cryostat sections

were incubated with primary anti-pancytokeratin antibody

(DakoCytomation, Carpinteria, CA; 1:50). After dehydration,

the tissue sections were incubated with Cy3-labeled Y chro-

mosome probes (Star*FISH; Cambio, Dry Drayton, UK) over-

night. The sections were then washed and incubated with the

anti-pancytokeratin antibody again at a 1:50 dilution. After

washing, the slides were mounted in 40, 6-diamidino-2-

phenylindole (DAPI; Invitrogen, Carlsbad, CA). The sections

were viewed with a confocal laser scanning fluorescence

microscope (Leica Biosystems, Wetzlar, Germany).

2.6. ELISA

The expression of CXCR4 and CXCL12 in the woundmargin of

mice at different times after burns was assessed by ELISA

analysis. The tissues collected from the wound of chimeric

C57BL/6mice on postburn days 1, 3, 7, 14, 21, and 28were lysed

as previously described [19]. The levels of CXCR4 and CXCL12

weremeasured using a mouse CXCR4 and CXCL12 Quantikine

Kit (R&D Systems, Minneapolis, MN) according to the manu-

facturer’s protocol.

2.7. IHC

The tissues collected from chimeric C57BL/6 mice after burns

were harvested in PBS-buffered formaldehyde, embedded in

paraffin, and sliced into 4-mm thick sections. Monoclonal anti-

bodies against CXCL12 (Abcam, Cambridge, UK) were used for

the analysis. Immunoreactivity was detected using a horse-

radish peroxidasee30-, 30-diaminobenzidine kit (Beyotime,

Shanghai, China), followed by counterstaining with hematox-

ylin, dehydration, and mounting. The representative areas

containing CXCL12-positive tissue were captured by a micro-

scope (Olympus, Tokyo, Japan) with 200� magnification.

2.8. In vitro and in vivo chemotaxis analysis blockingCXCR4

For in vitro chemotaxis analysis, 100 mL BM-MSCs (5� 105 cells/

mL) were incubated with CXCR4 antagonist AMD3100

(Cayman Chemical, Ann Arbor, MI; 5 mg/mL) or PBS as

a vehicle in the upper chamber (Corning, Corning, NY). a-MEM

medium containing both 10% (vol/vol) FBS and CXCL12 (R&D

Systems; 50 ng/mL) was in the lower well. After a 24-h incu-

bation, the migration cells were stained with 0.5% (wt/vol)

crystal violet (Beyotime) and counted in five random fields

using a light microscope at 40� magnification (Olympus). For

in vivo chemotaxis analysis, 1 � 106 BM-MSCs were pre-

incubated with AMD3100 (5 mg/mL) or PBS for 30 min and

injected into the tail veins of bone marrowedestroyed female

C57BL/6 mice. The burned model was created by the same

method described above. FISH and IF were conducted at

postburn day 14, and the wound areas were also tested using

the same method described above.

2.9. Statistical analysis

SPSS version 17.0 software (SPSS for Windows, Inc, Chicago,

IL) was used for all statistical analysis. The area measure-

ments and counts of the migrated cells were all accomplished

by two experimenters at three independent times. For the

repeatability between the two raters, the Supplementary

Table shows the intraclass correlation coefficient (ICC) of the

raters. There is no statistical difference between the raters. All

results are expressed as themean� SEM. Student paired t-test

was used to compare the differences between 2 groups, while

one-way analysis of variance was used to analyze of the data

among three or more groups. P < 0.05 was considered as

significant difference.

3. Results

3.1. Successful establishment of the chimeric mousemodel using MSCs from GFP transgenic mice

To establish the chimeric mouse model, we first identify the

GFP-labeled MSCs from GFP transgenic mice. The morphology

of the MSCs from male GFP transgenic mice was spindle-

shaped under a light microscope (Fig. 1A), and its green fluo-

rescence was observed using fluorescence imaging (Fig. 1A).

Moreover, the MSCs were positive for SCA-1, CD29, CD34, and

CD44 but negative for CD117 using flow cytometry analyses

(FACSAria cell sorter; BD, San Jose, CA; Fig. 1B). The capacity of

these MSCs to differentiate into adipocytes, osteoblasts, and

chondrocytes was confirmed in a previous study [20]. After

irradiation, the recipient female mice were transfused with

these MSCs. Sry gene, which rarely exists in wild-type female

mice, was detected in the peripheral blood of all recipients 20

d after BM-MSC transplantation (Fig. 1C). These results

showed that the bonemarrow function of the chimeric mouse

was successfully re-established.

3.2. BM-MSCs were primarily recruited around thewound margin and promoted wound healing

To investigate the distribution of the GFP-MSCs from the re-

established bone marrow, an in vivo fluorescence imaging

systemwas used to observe the localization of these cells post

burn. Figure 2A shows the images of the GFP-MSCs in the

mouse and the corresponding wound in pseudo color. It was

clearly shown that the GFP-labeled BM-MSCs migrated to the

wound site at postburn day 1, and the BM-MSCs were mainly

localized around the wound margin. The wound area gradu-

ally decreased from postburn day 1 to day 28 (Fig. 2B). These

Fig. 1 e Identification of BM-MSCs and the chimeric mouse model. (A) The morphology of BM-MSCs from male GFP

transgenic mice was observed under light microscopy (a) and fluorescence imaging (b). (B) The BM-MSCs were positive for

SCA-1, CD29, CD34, and CD44, but negative for CD117, by flow cytometry analysis. (C) Recipient mice were exposed to 10 Gy

whole-body irradiation using a Cobalt-60 source. Four hours after irradiation, 1 3 106 BM-MSCs from male GFP transgenic

C57BL/6 mice were injected into the tail veins of recipient mice. Sry gene expression in peripheral blood cells of mice was

determined using real-time quantitative RT-PCR 20 d after the BM-MSC transplantation. The expression levels were

normalized to GAPDH. The results represent the mean ± SEM of three independent experiments. *P < 0.01 versus negative

control (wild-type female mice).

j o u rn a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8e4

results suggest that BM-MSCs may be involved in wound

regeneration.

3.3. BM-MSCs were located in the epidermis and hairfollicles of wound

It has been clearly shown by the above study that BM-MSCs

were primarily recruited around the wound margin, so we

Fig. 2 e BM-MSCs were primarily recruited around the woundma

was established 21 d after BM-MSC transplantation. Then in vivo

room on days 1, 3, 7, 14, 21, and 28 post-wounding using an in

pseudo color were taken. (B) The wound area was measured at

mean ± SEM (*P < 0.05, **P < 0.01, #P < 0.001 versus day 1).

hypothesize that the MSCs may promote the epithelialization

of wounded skin. Because the Y chromosomeepositive cells

were from the male mice and could represent the BM-MSC

and because pancytokeratin is a special marker of the

epithelium, we used FISH to detect the Y chromosomee

positive cells and IF to detect the pan-cytokeratin-positive

cells. As revealed in Figure 3, Y chromosomeepositive cells

were found to colocalize with pan-cytokeratin in the

rgin and promoted wound healing. (A) A burn injurymodel

fluorescence imaging was performed in a completely dark

vivo imaging system. The images in both true color and

different days post-wound. The results represent the

Fig. 3 e BM-MSCs were located in the epidermis and hair follicles of the wound. The tissue sections at wound sites were

collected on days 1, 3, 7, 14, 21, and 28 after wounding and Y chromosome-positive cells were detectedwith Y-FISH and pan-

cytokeratin (Pan-CK) were detected with IF. The nuclei were stained blue (DAPI). Then the images were merged. Bar, 50 mm.

j o u r n a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8 e5

epidermis and hair follicles of the wound margin on postburn

day 1. Both the amount of the Y-chromosomeepositive cells

and the pan-cytokeratin-positive cells were increased in the

wound in a time-dependent manner. Together, these results

indicated that the BM-MSCs were recruited to the epidermis

and hair follicles, which ultimately promoted the expression

of pancytokeratin and the formation of epithelialization.

3.4. CXCL12-CXCR4 signaling was important for thechemotaxis of BM-MSCs

Because the CXCL12-CXCR4 axis is one of the most important

signals in the progression for the mobilization of cancer cells

and inflammatory cells, we hypothesize that this axis also

participates in the movement of the transplanted BM-MSCs.

We examined the expression levels of CXCL12 and CXCR4 in

the tissues from the wound margins by ELISA and IHC. As

shown in Figure 4A, the expression of CXCR4 and CXCL12

protein in the wound margins was significantly elevated at

day 7 post burn. In addition, using IHC analysis, CXCL12 was

found to be primarily expressed in the basal layer of the

epidermis and hair follicles with IHC. IHC showed that the

levels of CXCL12 were significantly elevated in BM-MSC-

treated mice at day 7 (Fig. 4D) compared with those at day

0 post burn (Fig. 4C), which is consistent with the ELISA result.

3.5. Inhibition of CXCR4 decreased BM-MSCmobilization and attenuated wound healing

To further confirm the importance of CXCL12-CXCR4 signaling

in themovement of MSCs, we observed the chemotaxis of BM-

MSCs in vitro and in vivo using the CXCR4 inhibitor. First,

Fig. 4 e CXCL12-CXCR4 signaling was important for the chemotaxis of BM-MSCs. (A,B) ELISA was used to detect the CXCR4

(A) and CXCL12 (B) protein levels in the tissue of wounded mice at different times post wounding. The data are the

mean ± SEM from three independent experiments (*P< 0.05 comparedwith day 0). (C,D) IHCwas used to analyze the CXCL12

protein expression level and localization in wound sites at postburn day 0 (C) and day 7 (D). The bar indicates 200 mm.

j o u rn a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8e6

AMD3100 effectively inhibited the directional migration of

BM-MSCs in vitro compared with the control group (P < 0.05;

Fig. 5A and B). Second, the Y chromosome and pancytokeratin

double-positive epidermal cells and hair follicle cells at the

wound margins were notably decreased in the AMD3100

group, indicating that AMD3100 inhibited the mobilization of

BM-MSCs and, their ability to participate in wound repair

(Fig. 5C). Moreover, as shown in Figure 5D and E, treatment

with AMD3100 significantly attenuated wound closure

compared with the control group (PBS).

4. Discussion

Burn injury remains a challenge in the field of cutaneous

woundhealing [9]. Superficial burnsusually healwithminimal

scarring, but treatments for second- and third-degree burn

injuries remain far from optimal [21,22]. In the present study,

we demonstrated that BM-MSCs promoted the healing of

thermal burned skin using a novel model (chimeric C57BL/6

mice). After we successfully constructed the chimeric mouse

model, we found that BM-MSCsmigrated to the burn sites and

were mainly recruited to the epidermis and hair follicles.

A previous study reported that BM-MSCs accelerated the

recovery of homeostasis and promoted healing of thermal

burn wounds in a patient with an extensive skin burn [23];

however, the distribution and detailed localization of the

MSCs is not clear. This study was the first to use an in vivo

imaging system to observe the distribution of the GFP-labeled

stem cells, which clearly provided a real-time and dynamic

image of the movement of the labeled cells in vivo after burns.

We thus provided evidence that the transplanted BM-MSCs

mainly directionally migrated to the wound margin and

that their distribution was primarily around the wound.

Furthermore, we showed that Y chromosomeepositive cells

were colocalized with pan-cytokeratin-positive cells in the

hair follicles and epidermis of the wound margin. These

results indicate that MSCs accelerate skin epithelialization

after burn andmay provide clues for the clinical application of

BM-MSCs in burn wound treatment.

The possible mechanisms by which MSCs promote cuta-

neous wound repair and regeneration contain the following

aspects: paracrine action, immunomodulation, immunosup-

pression, self-differentiation, and cell fusion [24]dbut which

aspects play primary roles remains controversial. During our

study, we found that the BM-MSCs promoted the epithelial-

ization of wounded skin. However, it has yet to be determined

whether the Y chromosomeepositive cells are due to the self-

differentiation of the BM-MSCs or cell fusion. Besides, the

expression level of the soluble factors, including keratinocyte

growth factor, angiopoietin 1, and interleukin 10, may have

increased in the plasma after the BM-MSC transplantation,

especially around the wound. It is interesting and significant

to demonstrate which of the soluble factors is the most

abundant and important in further study.

Studies have shown that binding CXCL12 to its cognate

receptor, CXCR4, plays an important role in the migration of

human umbilical cord blood MSCs in vitro [25]. CXCL12 is

expressed/secreted by several tissues/organs in the body. The

most important sources of SDF-1 are bone marrow-, lymph

node-, muscle- and lung-derived fibroblasts. SDF-1 is also

secreted by liver and kidney cells and in several regions of the

centralnervoussystem[26].CXCL12expressionhasbeenshown

toincreaseunderstressconditionsandmaythusservetoattract

stem cells to sites of tissue injury [27]. It has been reported that

various organs respond to tissue damage, such as from irradi-

ation, hypoxia, or toxic agents, by increasing the expression/

secretionofCXCL12 [28,29]. Fewstudieshave focusedontherole

Fig. 5 e Inhibition of CXCR4 decreased BM-MSC mobilization and attenuated wound healing. (A) The transwell assays

showed the migration capacity of MSCs co-cultured with PBS (a) or AMD3100 (b). Bar, 100 mm. (B) The number of migrated

MSCs in two different conditions (n [ 3, *P < 0.05). (CeF) 1 3 106 BM-MSCs were pre-incubated with AMD3100 (5 mg/mL) or

PBS for 30 min and injected into the tail veins of bone marrowedestroyed female C57BL/6 mice. Next, the mice were

exposed to deep burn and then the tissue sections at wound sites were collected 21 d after the burn. (C) IF was used to detect

the pan-cytokeratin (Pan-CK) and Y-FISH was used to reveal the Y chromosomeepositive cells. Bar, 75 mm. (D) Wound size

was measured. (E) Alteration of the wound size shown by in vivo fluorescence imaging.

j o u r n a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8 e7

of BM-MSCs in the healing of burn wounds in vivo. In our study,

we demonstrated that the expression levels of CXCL12 and

CXCR4 proteins at the injured sites of BM-MSC-treated mice

afteraburn increasedsignificantlypostburnandreachedapeak

at 7 d post burn. However, the CXCR4-selective antagonist

AMD3100significantly inhibited themobilizationofBM-MSCsto

the wounded skin, therefore prolonging the wound closure.

These data demonstrated that CXCL12/CXCR4 signaling medi-

ated the mobilization of murine BM-MSCs to wound sites for

participation in the wound repair process.

In conclusion, we showed that the BM-MSCs migrated to

the injured sites and localized in the epidermis and hair

follicles of the burned skin. They significantly enhanced burn

wound healing by epithelialization, and the mobilization of

the BM-MSCs was mediated by CXCL12/CXCR4 signaling.

Thus, our data suggest that administration of MSCs to the

injured wound in a proper manner and that the enhancement

of CXCL12/CXCR4 axis would be novel therapeutic strategies

for the treatment of burn wounds.

Acknowledgment

This study was supported by a grant from the National Nature

Science Foundation of China (NSFC30772252) and Science

Fund from the State Key Laboratory (SKLKF 200923).

Supplementary Data

Supplementarydata associatedwith this article canbe found in

the online version at http://dx.doi.org/10.1016/j.jss.2013.01.019.

j o u rn a l o f s u r g i c a l r e s e a r c h -- ( 2 0 1 3 ) e 1ee 8e8

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