Biomedical subjects

William A Kuziel

Publications and source records attributed to William A Kuziel.

At least 19 recordsLinked to original sources

PubMed2006

Fat accumulation with altered inflammation and regeneration in skeletal muscle of CCR2-/- mice following ischemic injury.

Chemokines recruit inflammatory cells to sites of injury, but the role of the CC chemokine receptor 2 (CCR2) during regenerative processes following ischemia is poorly understood. We studied injury, inflammation, perfusion, capillary formation, monocyte chemotactic protein-1 (MCP-1) levels, muscle regeneration, fat accumulation, and transcription factor activation in hindlimb muscles of CCR2-/- and wild-type (WT) mice following femoral artery excision (FAE). In both groups, muscle injury and restoration of vascular perfusion were similar. Nevertheless, edema and neutrophil accumulation were significantly elevated in CCR2-/- compared with WT mice at day 1 post-FAE and fewer macrophages were present at day 3. MCP-1 levels in post-ischemic calf muscle of CCR2-/- animals were significantly elevated over baseline through 14 days post-FAE and were higher than WT mice at days 1, 7, and 14. In addition, CCR2-/- mice exhibited impaired muscle regeneration, decreased muscle fiber size, and increased intermuscular adipocytes with similar capillaries/mm(2) postinjury. Finally, the transcription factors, MyoD and signal transducers of and activators of transcription-3 (STAT3), were significantly increased above baseline but did not differ significantly between groups at any time point post-FAE. These findings suggest that increases in MCP-1, and possibly, MyoD and STAT3, may modulate molecular signaling in CCR2-/- mice during inflammatory and regenerative events. Furthermore, alterations in neutrophil and macrophage recruitment in CCR2-/- mice may critically alter the normal progression of downstream regenerative events in injured skeletal muscle and may direct myogenic precursor cells in the regenerating milieu toward an adipogenic phenotype.

Adipocytes↗

PubMed2006

Alveolar epithelial cells direct monocyte transepithelial migration upon influenza virus infection: impact of chemokines and adhesion molecules.

Influenza A virus pneumonia is characterized by severe lung injury and high mortality. Early infection elicits a strong recruitment of monocytes from the peripheral blood across the endo-/epithelial barrier into the alveolar air space. However, it is currently unclear which of the infected resident lung cell populations, alveolar epithelial cells or alveolar macrophages, elicit monocyte recruitment during influenza A virus infection. In the current study, we investigated whether influenza A virus infection of primary alveolar epithelial cells and resident alveolar macrophages would elicit a basal-to-apical monocyte transepithelial migration in vitro. We found that infection of alveolar epithelial cells with the mouse-adapted influenza A virus strain PR/8 strongly induced the release of monocyte chemoattractants CCL2 and CCL5 followed by a strong monocyte transepithelial migration, and this monocytic response was strictly dependent on monocyte CCR2 but not CCR5 chemokine receptor expression. Analysis of the adhesion molecule pathways demonstrated a role of ICAM-1, VCAM-1, integrin-associated protein (CD47), and junctional adhesion molecule-c on the epithelial cell surface interacting with monocyte beta(1) and beta(2) integrins and integrin-associated protein in the monocyte transmigration process. Importantly, addition of influenza A virus-infected alveolar macrophages further enhanced monocyte transmigration across virus-infected epithelium in a TNF-alpha-dependent manner. Collectively, the data show an active role for virus-infected alveolar epithelium in the regulation of CCL2/CCR2-dependent monocyte transepithelial migration during influenza infection that is essentially dependent on both classical beta(1) and beta(2) integrins but also junctional adhesion molecule pathways.

Animals↗

PubMed2006

Chemokine CC receptor 2 is important for acute control of cardiac parasitism but does not contribute to cardiac inflammation after infection with Trypanosoma cruzi.

The CC chemokine ligand 2 (CCL2) and CC chemokine receptor 2 (CCR2) are expressed in the heart after infection with Trypanosoma cruzi, suggesting that they play an important role in host defense. Infection of CCR2-deficient (CCR2(-/-)) mice with T. cruzi resulted in increased cardiac parasitism, yet the severity of cardiac inflammation was not affected. In addition, expression of interferon- gamma and inducible NO synthase in the heart, which are associated with effective killing of trypomastigotes, was not affected in CCR2(-/-) mice. These observations reveal that CCR2 signaling plays a distinct role that is separate from that of influencing either chemotaxis or previously defined anti-trypomastigote mechanisms for the control of T. cruzi's replication in the heart.

Animals↗

PubMed2006

CC chemokine receptor (CCR)-2 prevents arthritis development following infection by Mycobacterium avium.

The host factors that influence autoimmune arthritides such as rheumatoid arthritis have not been fully elucidated. We previously found that genetic inactivation of CC chemokine receptor 2 (CCR2) in the arthritis-prone DBA/1j mouse strain significantly increases the susceptibility of this strain to autoimmune arthritis induced by immunization with collagen type II (CII) and complete Freund's adjuvant (CFA). Here, we show that following intradermal infection with Mycobacterium avium, a similar arthritis phenotype was detected in Ccr2-null mice in the DBA/1j, but not in the BALB/c background. The failure to develop arthritis in Ccr2-null BALB/c mice occurred in the face of high bacterial burdens and low interferon gamma (IFNgamma) production. By contrast, Ccr2-null DBA/1j mice had low bacterial burdens, produced normal amounts of IFNgamma, and had high titers of autoantibodies against CII. Thus, the Ccr2-null state in an arthritic-prone genetic background leads to increased arthritis susceptibility following infectious (M. avium) and noninfectious (CII/CFA) challenges. Because CCR2 serves as a negative regulator of murine arthritis, caution might need to be exercised while testing CCR2 blockers in human arthritis or other diseases. These findings also indicate that Ccr2-null DBA/1j mice might serve as a valuable model system to uncover the immunological determinants of arthritis and to test novel antiarthritic agents.

Animals↗

PubMed2006

Endotoxin induced peritonitis elicits monocyte immigration into the lung: implications on alveolar space inflammatory responsiveness.

BACKGROUND: Acute peritonitis developing in response to gram-negative bacterial infection is known to act as a trigger for the development of acute lung injury which is often complicated by the development of nosocomial pneumonia. We hypothesized that endotoxin-induced peritonitis provokes recruitment of monocytes into the lungs, which amplifies lung inflammatory responses to a second hit intra-alveolar challenge with endotoxin. METHODS: Serum and lavage cytokines as well as bronchoalveolar lavage fluid cells were analyzed at different time points after intraperitoneal or intratracheal application of LPS. RESULTS: We observed that mice challenged with intraperitoneal endotoxin developed rapidly increasing serum and bronchoalveolar lavage fluid (BALF) cytokine and chemokine levels (TNFalpha, MIP-2, CCL2) and a nearly two-fold expansion of the alveolar macrophage population by 96 h, but this was not associated with the development of neutrophilic alveolitis. In contrast, expansion of the alveolar macrophage pool was not observed in CCR2-deficient mice and in wild-type mice systemically pretreated with the anti-CD18 antibody GAME-46. An intentional two-fold expansion of alveolar macrophage numbers by intratracheal CCL2 following intraperitoneal endotoxin did not exacerbate the development of acute lung inflammation in response to intratracheal endotoxin compared to mice challenged only with intratracheal endotoxin. CONCLUSION: These data, taken together, show that intraperitoneal endotoxin triggers a CCR2-dependent de novo recruitment of monocytes into the lungs of mice but this does not result in an accentuation of neutrophilic lung inflammation. This finding represents a previously unrecognized novel inflammatory component of lung inflammation that results from endotoxin-induced peritonitis.

Animals↗

PubMed2006

Deficiency in CCR5 but not CCR1 protects against neointima formation in atherosclerosis-prone mice: involvement of IL-10.

The chemokine RANTES has been implicated in neointimal hyperplasia after arterial injury. We analyzed the differential role of the RANTES receptors CCR1 and CCR5 by genetic deletion in apolipoprotein E-deficient mice. Deficiency in CCR5 significantly reduced neointimal area after arterial wire injury, associated with a decrease in macrophages, CD3(+) T lymphocytes, and CCR2(+) cells. In contrast, CCR1 deficiency did not affect neointimal area or cell content. Deletion of CCR5 entailed an up-regulation of the anti-inflammatory cytokine interleukin 10 (IL-10) in neointimal smooth muscle cells, and its antibody blockade reversed effects in CCR5(-/-) mice. Conversely, proinflammatory interferon gamma was increased in the neointima of CCR1(-/-) mice, and its blockade unmasked a reduction in macrophage recruitment. Our data indicate that CCR5 is more crucial than CCR1 for neointimal plaque formation, and that its attenuation in CCR5(-/-) mice is due to an atheroprotective immune response involving IL-10. This harbors important implications for targeting chemokine receptors in vascular remodeling.

Animals↗

PubMed2006

Attenuated liver tumor formation in the absence of CCR2 with a concomitant reduction in the accumulation of hepatic stellate cells, macrophages and neovascularization.

The liver parenchyma is populated by hepatocytes and several nonparenchymal cell types, including Kupffer cells and hepatic stellate cells. Both Kupffer cells and hepatic stellate cells are responsive to the chemokine CCL2, but the precise roles of CCL2 and these cells in liver tumor formation remain undefined. Hence, we investigated the effects of the lack of the major CCL2 receptor, CCR2, on liver tumor formation induced by intraportal injection of the murine colon adenocarcinoma cell line, colon 26. Wild-type mice showed macroscopic tumor foci in the liver 10 days after injection of colon 26 cells. After 10 days, CCL2 proteins were detected predominantly in tumor cells, coincident with increased intratumoral macrophage and hepatic stellate cell numbers. Although tumor formation occurred at similar rates in wild-type and CCR2-deficient mice up to 10 days after tumor cell injection, the number and size of tumor foci were significantly attenuated in CCR2-deficient mice relative to wild-type mice thereafter. Moreover, neovascularization and matrix metalloproteinase 2 expression were diminished in CCR2-deficient mice with a concomitant reduction in the accumulation of macrophages and hepatic stellate cells. Furthermore, matrix metalloproteinase 2 was detected predominantly in hepatic stellate cells but not in macrophages. We provided the first definitive evidence that the absence of CCR2-mediated signals can reduce the trafficking of hepatic stellate cells, a main source of matrix metalloproteinase 2, and consequently can diminish neovascularization during liver tumor formation.

Adenocarcinoma↗

PubMed2006

Abnormal immune response of CCR5-deficient mice to ocular infection with herpes simplex virus type 1.

Ocular herpes simplex virus type 1 (HSV-1) infection elicits a strong inflammatory response that is associated with production of the beta chemokines CCL3 and CCL5, which share a common receptor, CCR5. To gain insight into the role of these molecules in ocular immune responses, the corneas of wild-type (WT) and CCR5-deficient (CCR5-/-) mice were infected with HSV-1 and inflammatory parameters were measured. In the absence of CCR5, the early infiltration of neutrophils into the cornea was diminished. Associated with this aberrant leukocyte recruitment, neutrophils in CCR5-/- mice were restricted to the stroma, whereas in WT mice, these cells trafficked to the stroma and epithelial layers of the infected cornea. Virus titres and cytokine/chemokine levels in the infected tissue of these mice were similar for the first 5 days after infection. However, by day 7 post-infection, the CCR5-/- mice showed a significant elevation in the chemokines CCL2, CCL5, CXCL9 and CXCL10 in the trigeminal ganglion and brainstem, as well as a significant increase in virus burden. The increase in chemokine expression was associated with an increase in the infiltration of CD4 and/or CD8 T cells into the trigeminal ganglion and brainstem of CCR5-/- mice. Surprisingly, even though infected CCR5-/- mice were less efficient at controlling the progression of virus replication, there was no difference in mortality. These results suggest that, although CCR5 plays a role in regulating leukocyte trafficking and control of virus burden, compensatory mechanisms are involved in preventing mortality following HSV-1 infection.

Animals↗

PubMed2006

MCP-1/CCR2 signalling pathway regulates hyperoxia-induced acute lung injury via nitric oxide production.

To clarify the role of the monocyte chemoattractant protein-1 (MCP-1)/C-C chemokine receptor 2 (CCR2) signalling pathway in hyperoxia-induced acute lung injury, CCR2-deficient (CCR2-/-) and wild-type (CCR2+/+) mice were exposed to 85% O(2) for up to 6 days. At day 3, body weight significantly decreased and total protein concentration in bronchoalveolar lavage fluid (BALF) was higher in CCR2-/- mice compared with CCR2+/+ mice. Cumulative survivals were significantly lower in CCR2-/- mice than in CCR2+/+ mice. However, the two groups showed no significant differences in both histological changes and number of macrophages in BALF. Real-time reverse transcriptase-polymerase chain reaction revealed increased mRNA levels of MCP-1, interleukin-1beta thioredoxin-1, and inducible nitric oxide synthase (iNOS) in lung tissues in CCR2-/- mice compared with CCR2+/+ mice. Increased iNOS mRNA levels in alveolar macrophages exposed to 85% O(2) for 48 h in vivo or in vitro were significantly higher in CCR2-/- mice than in CCR2+/+ mice. These results suggest that the MCP-1/CCR2 signalling pathway is protective against hyperoxia-induced tissue injury by suppressing induction of iNOS and consequent production of reactive oxygen species by activated alveolar macrophages.

Acute Disease↗

PubMed2006

The CC chemokine receptor 5 is important in control of parasite replication and acute cardiac inflammation following infection with Trypanosoma cruzi.

Infection of susceptible mice with the Colombiana strain of Trypanosoma cruzi results in an orchestrated expression of chemokines and chemokine receptors within the heart that coincides with parasite burden and cellular infiltration. CC chemokine receptor 5 (CCR5) is prominently expressed during both acute and chronic disease, suggesting a role in regulating leukocyte trafficking and accumulation within the heart following T. cruzi infection. To better understand the functional role of CCR5 and its ligands with regard to both host defense and/or disease, CCR5(-/-) mice were infected with T. cruzi, and the disease severity was evaluated. Infected CCR5(-/-) mice develop significantly higher levels of parasitemia (P < or = 0.05) and cardiac parasitism (P < or = 0.01) during acute infection that correlated with reduced survival. Further, we show that CCR5 is essential for directing the migration of macrophages and T cells to the heart early in acute infection with T. cruzi. In addition, data are provided demonstrating that CCR5 does not play an essential role in maintaining inflammation in the heart during chronic infection. Collectively, these studies clearly demonstrate that CCR5 contributes to the control of parasite replication and the development of a protective immune response during acute infection but does not ultimately participate in maintaining a chronic inflammatory response within the heart.

Acute Disease↗

PubMed2006

CC chemokine receptor-2 deficiency attenuates oxidative stress and infarct size caused by myocardial ischemia-reperfusion in mice.

BACKGROUND: Monocyte chemoattractant protein-1 (MCP-1) and its major receptor, CC chemokine receptor 2 (CCR2), have been shown to contribute to left ventricular remodeling after myocardial infarction. However, it is unknown whether CCR2 deficiency protects the myocardium after myocardial ischemia-reperfusion. The purpose of the present study was to investigate the effects of CCR2 deficiency on myocardial ischemia-reperfusion injury in mice. METHODS AND RESULTS: Experiments were performed in CCR2(-/-) and wild-type mice subjected to 45 min of ischemia followed by reperfusion. Macrophage infiltration in ischemic lesions was markedly reduced in CCR2(-/-) mice compared with wild-type mice (p<0.01). The infarct size was significantly reduced in CCR2(-/-) mice compared with wild-type mice at 3 days after reperfusion (p<0.001). In situ zymography revealed augmented gelatinolytic activity at 3 days after reperfusion in wild-type mice, but significantly less activity in CCR2(-/-) mice. NADPH oxidase activity, the intensity of nitrotyrosine staining and expression of inducible nitric oxide synthase and thioredoxin-1 were significantly increased in ischemic myocardium in wild-type mice compared with CCR2(-/-) mice, indicating a role for CCR2 in oxidative stress after ischemia-reperfusion. CONCLUSIONS: Inhibition of the MCP-1/CCR2 pathway may be a useful strategy for attenuating myocardial ischemia-reperfusion injury.

Animals↗

PubMed2005

Perturbation of chemokine networks by gene deletion alters the reinforcing actions of ethanol.

Microarray analysis of human alcoholic brain and cultured cells exposed to ethanol showed significant changes in expression of genes related to immune or inflammatory responses, including chemokines and chemokine receptors. To test the hypothesis that chemokines exhibit previously undiscovered pleiotropic effects important for the behavioral actions of ethanol, we studied mutant mice with deletion of the Ccr2, Ccr5, Ccl2 or Ccl3 genes. Deletion of Ccr2, Ccl2 (females) or Ccl3 in mice resulted in lower preference for alcohol and consumption of lower amounts of alcohol in a two-bottle choice test as compared with wild-type mice. Ethanol treatment (2.5 g/kg, i.p.) induced stronger conditioned taste aversion in Ccr2, Ccl2 or Ccl3 null mutant mice than in controls. Ccr2 and Ccr5 null mutant mice did not differ from wild-type mice in ethanol-induced loss of righting reflex (LORR), but mice lacking Ccl2 or Ccl3 showed longer LORR than wild-type mice. There were no differences between mutant strains and wild-type mice in severity of ethanol-induced withdrawal. Genetic mapping of chromosome 11 for the Ccl2 and Ccl3 genes (46.5 and 47.6 cM, respectively) revealed that an alcohol-induced LORR QTL region was contained within the introgressed region derived from 129/SvJ, which may cause some behavioral phenotypes observed in the null mice. On the contrary, known QTLs on Chr 9 are outside of 129/SvJ region in Ccr2 and Ccr5 (71.9 and 72.0 cM, respectively) null mutant mice. These data show that disruption of the chemokine network interferes with motivational effects of alcohol.

Alcohol Drinking↗

PubMed2005

CCR2 expression by brain microvascular endothelial cells is critical for macrophage transendothelial migration in response to CCL2.

While the expression of chemokine receptors by endothelial cells is now well established, little is known of the function of these receptors at this cellular locale. However, given that chemokines are instrumental in directing leukocytes to specific parenchymal sites, one possibility is that endothelial chemokine receptors play a role in the process of leukocyte extravasation. To test this hypothesis, we investigated the contribution of CCR2, the major cognate receptor for the chemokine CCL2 (formerly known as MCP-1), to CCL2-stimulated transendothelial migration of macrophages (mØ) across cultured brain microvascular endothelial cells (BMEC). Specifically, we prepared both BMEC and mØ from wild-type (WT) mice and mice deficient in CCR2; i.e., CCR2 (-/-), and compared the ability of WT and CCR2 (-/-) BMEC to support CCL2-stimulated transendothelial migration of WT and CCR2 (-/-) mØ. In response to CCL2, WT mØ, but not CCR2 (-/-) mØ, were stimulated to migrate across WT BMEC, consistent with the recognized obligatory role for CCR2 in mediating CCL2-stimulated responses. Remarkably, however, neither WT nor CCR2 (-/-) mØ were stimulated by CCL2 to migrate across CCR2 (-/-) BMEC. In contrast, both types of mØ were able to migrate similarly across both types of BMEC in response to another chemokine--CCL3 (formerly known as MIP-1alpha)--which utilizes receptors other than CCR2. Lastly, CCL2-induced mØ transendothelial migration was blocked by treatment of WT BMEC with pertussis toxin, suggesting that CCR2 is functionally coupled to the inhibitory G protein Galphai, much as it is in other cell types. These results highlight a heretofore-unrecognized role for endothelial CCR2 in mediating transendothelial migration.

Animals↗

PubMed2005

Recruitment of Gr-1+ monocytes is essential for control of acute toxoplasmosis.

Circulating murine monocytes comprise two largely exclusive subpopulations that are responsible for seeding normal tissues (Gr-1-/CCR2-/CX3CR1high) or responding to sites of inflammation (Gr-1+/CCR2+/CX3CR1lo). Gr-1+ monocytes are recruited to the site of infection during the early stages of immune response to the intracellular pathogen Toxoplasma gondii. A murine model of toxoplasmosis was thus used to examine the importance of Gr-1+ monocytes in the control of disseminated parasitic infection in vivo. The recruitment of Gr-1+ monocytes was intimately associated with the ability to suppress early parasite replication at the site of inoculation. Infection of CCR2-/- and MCP-1-/- mice with typically nonlethal, low doses of T. gondii resulted in the abrogated recruitment of Gr-1+ monocytes. The failure to recruit Gr-1+ monocytes resulted in greatly enhanced mortality despite the induction of normal Th1 cell responses leading to high levels of IL-12, TNF-alpha, and IFN-gamma. The profound susceptibility of CCR2-/- mice establishes Gr-1+ monocytes as necessary effector cells in the resistance to acute toxoplasmosis and suggests that the CCR2-dependent recruitment of Gr-1+ monocytes may be an important general mechanism for resistance to intracellular pathogens.

Acute Disease↗

PubMed2005

The complex role of the chemokine receptor CCR2 in collagen-induced arthritis: implications for therapeutic targeting of CCR2 in rheumatoid arthritis.

CCR2 has been widely considered as a potential therapeutic target for autoimmune disease, particularly rheumatoid arthritis, and various CCR2 blocking agents have been developed, some of which have entered clinical trials. In this review, we examine the relevant information regarding the role of CCR2, and to a lesser extent of the closely related chemokine receptor CCR5, in the immunopathogenesis of collagen-induced arthritis, an animal model of rheumatoid arthritis. Experimental evidence showing that CIA is accelerated and exacerbated when CCR2 is genetically inactivated (knockout mice) or blocked with specific antibodies warrant additional investigations before the relevance of the findings in rodent models can be applied to human patients with RA.

Animals↗

PubMed2005

Constitutive homing of mast cell progenitors to the intestine depends on autologous expression of the chemokine receptor CXCR2.

Homing of mast cell progenitors (MCps) to the mouse small intestine involves the interaction of alpha4beta7 integrin with mucosal addressin cellular adhesion molecule-1 (MAdCAM-1). We now demonstrate the dependence of this process on CXC chemokine receptor 2 (CXCR2) and vascular cell adhesion molecule-1 (VCAM-1) using null strains and mice sublethally irradiated and bone marrow (BM) reconstituted (SIBR) with wild-type or null BM or with wild-type BM followed by administration of blocking antibody. The intestinal MCp concentration in CXCR2(-/-) mice was reduced by 67%, but was unaltered in CC chemokine receptor 2(-/-) (CCR2(-/-)), CCR3(-/-), or CCR5(-/-) mice. SIBR mice given CXCR2(-/-) BM had an intestinal MCp concentration that was 76% less than that in BALB/c BM reconstituted mice. Antibody blockade of VCAM-1 or of CXCR2 in SIBR mice reduced intestinal MCp reconstitution, and mice lacking endothelial VCAM-1 also had a marked reduction relative to wild-type mice. Finally, the half-life of intestinal MCps in wild-type mice was less than one week on the basis of a more than 50% reduction by administration of anti-alpha4beta7 integrin or anti-CXCR2. Thus, the establishment and maintenance of MCps in the small intestine is a dynamic process that requires expression of the alpha4beta7 integrin and the alpha-chemokine receptor CXCR2.

Animals↗

PubMed2005

Monocyte chemoattractant protein-1 and CCR2 interactions are required for IFN-alpha/beta-induced inflammatory responses and antiviral defense in liver.

IFN-alpha/beta-mediated functions promote production of MIP-1alpha (or CCL3) by mediating the recruitment of MIP-1alpha-producing macrophages to the liver during early infection with murine CMV. These responses are essential for induction of NK cell inflammation and IFN-gamma delivery to support effective control of local infection. Nevertheless, it remains to be established if additional chemokine functions are regulated by IFN-alpha/beta and/or play intermediary roles in supporting macrophage trafficking. The chemokine MCP-1 (or CCL2) plays a distinctive role in the recruitment of macrophages by predominantly stimulating the CCR2 chemokine receptor. Here, we examine the roles of MCP-1 and CCR2 during murine CMV infection in liver. MCP-1 production preceded that of MIP-1alpha during infection and was dependent on IFN-alpha/beta effects for induction. Resident F4/80(+) liver leukocytes were identified as primary IFN-alpha/beta responders and major producers of MCP-1. Moreover, MCP-1 deficiency was associated with a dramatic reduction in the accumulation of macrophages and NK cells, as well as decreased production of MIP-1alpha and IFN-gamma in liver. These responses were also markedly impaired in mice with a targeted disruption of CCR2. Furthermore, MCP-1- and CCR2-deficient mice exhibited increased viral titers and elevated expression of the liver enzyme alanine aminotransferase in serum. These mice also had widespread virus-induced liver pathology and succumbed to infection. Collectively, these results establish MCP-1 and CCR2 interactions as factors promoting early liver inflammatory responses and define a mechanism for innate cytokines in regulation of chemokine functions critical for effective localized antiviral defenses.

Animals↗

PubMed2004

Chemokine receptor CCR2 involvement in skeletal muscle regeneration.

Chemokines, signaling through the CCR2 receptor, are highly expressed in injured skeletal muscle. Their target specificity depends on the cellular expression of the specific receptors. Here we demonstrate that, in freeze-injured muscle, CCR2 co-localized with Mac-3, a marker of activated macrophages as well as with myogenin, a marker of activated muscle precursor cells. The degeneration/regeneration process in skeletal muscle of CCR2-/- and wild-type mice was not significantly different at day 3. However in contrast to the regenerated muscle of the wild-type mice, the muscle from CCR2-/- mice was characterized by impaired regeneration, inflammation, and fibrotic response at day 14, increased fat infiltration, fibrosis, and calcification at day 21, and impaired strength recovery until at least 28 days post-injury. Consistently, the increased expression of Mac-1 and TNF-alpha was prolonged in the injured muscle of CCR2-/- mice. The expression pattern of the myogenic factors MyoD and myogenin was similar for both types of mice, while NCAM, which is associated with the initiation of fusion of muscle precursor cells, was more increased in the injured muscle of CCR2-/- mice. In conclusion, the study delineates that signaling through CCR2 is involved in muscle precursor cell activities necessary for complete and rapid regeneration of injured skeletal muscle.

Adipose Tissue↗