Colony-Stimulating Factor-1 Promotes Kidney Growth and Repair via Alteration of Macrophage Responses

Colony-stimulating factor (CSF)-1 controls the survival, proliferation, and differentiation of macrophages, which are recognized as scavengers and agents of the innate and the acquired immune systems. Because of their plasticity, macrophages are endowed with many other essential roles during development and tissue homeostasis. We present evidence that CSF-1 plays an important trophic role in postnatal organ growth and kidney repair. Notably, the injection of CSF-1 postnatally enhanced kidney weight and volume and was associated with increased numbers of tissue macrophages. Moreover, CSF-1 promotes postnatal renal repair in mice after ischemia-reperfusion injury by recruiting and influencing macrophages toward a reparative state. CSF-1 treatment rapidly accelerated renal repair with tubular epithelial cell replacement, attenuation of interstitial fibrosis, and functional recovery. Analysis of macrophages from CSF-1-treated kidneys showed increased expression of insulin-like growth factor-1 and anti-inflammatory genes that are known CSF-1 targets. Taken together, these data suggest that CSF-1 is important in kidney growth and the promotion of endogenous repair and resolution of inflammatory injury.Macrophages are versatile cells that have been long recognized as immune effectors where their recruitment to sites of injury is a fundamental feature of inflammation. Although their role in host defense has been well documented, macrophages and their precursors are also important during embryogenesis, normal tissue maintenance, and postnatal organ repair.^1,2 Almost all developing organs contain a population of resident monocytes that infiltrate very early during organogenesis and persist throughout adult life.^3–6 In addition to their phagocytic capabilities during tissue remodeling-associated apoptosis,^5,7 fetal macrophages have many trophic effects that promote tissue and organ growth.^6,8,9Colony-stimulating factor (CSF)-1 controls the differentiation, proliferation, and survival of macrophages by binding to a high-affinity cell-surface tyrosine kinase receptor (CSF-1R), encoded by the c-fms proto-oncogene that is expressed on macrophages and their progenitors.⁶ CSF-1 is critical for both adult and embryonic macrophage development. This is manifested by multiple organ growth deficiencies observed in osteopetrotic (Csf1^op/Csf1^op) mice that have a spontaneous mutation in the csf-1 gene. These mice show growth restriction and developmental abnormalities of the bones, brain, and reproductive and endocrine organs,^10–13 a phenotype that can be rescued by injection of exogenous CSF-1 or insertion of a csf-1 transgene.^14–16In adult organs, there is considerable heterogeneity of monocytes and macrophages with distinct subsets defined by phenotype, function, and the differential expression of cell surface markers.^17–19 Subpopulations of macrophages directly contribute to wound healing and tissue repair, supporting the concept that some macrophage phenotypes can promote organ regeneration after a pro-inflammatory state of injury.²⁰ The concept of macrophage polarization states has emerged; the M1 “classically activated” pro-inflammatory cell type apparently opposed by an M2 “alternatively activated” immune regulatory macrophage.¹⁸ In general, these two states are thought to be analogous to the opposing T helper 1 and T helper 2 immune responses, although in both cases this model is probably too simplistic. Functionally, it is more likely that distinct subpopulations of macrophages may exist in the same tissue and play critical roles in both the injury and recovery phases of inflammatory scarring.²⁰Our previous study provided evidence that the addition of CSF-1 to a developing murine kidney promotes a growth and differentiation response that is accompanied by increased numbers of macrophages.³ Furthermore, with the use of expression profiling we demonstrated that fetal kidney, lung, and brain macrophages share a characteristic gene expression profile that includes the production of factors important in the suppression of inflammation and the promotion of proliferation.³ Embryonic macrophages appear to play a positive trophic role that may have parallel reparative functions in many adult tissues undergoing repair and cellular replacement.^1,20 A number of studies have suggested that infiltrating macrophages along with the trophic factors they release participate in tissue repair of the kidney,^20–22 brain,²³ skin,^24,25 lung,²⁶ liver,²⁷ heart,²⁸ gastrointestinal tract,^29,30 and skeletal muscle.^31,32 Indeed, the pleiotrophic roles for CSF-1 in reproduction, development of multiple organ systems, and maternal-fetal interactions during pregnancy by macrophage-mediated processes have also been well defined.^2,33,34To determine the physiological relevance of CSF-1 as a component of the mammalian growth regulatory axis, CSF-1 was administered to neonatal mice. We report that CSF-1 administration to newborn mice increased body weight and kidney weight and volume and was associated with increased numbers of macrophages. Our results also establish that CSF-1 injection into mice after ischemia-reperfusion (IR) injury promoted endogenous repair with characteristic rapid re-epithelialization of the damaged tubular epithelium, leading to functional recovery. Flow cytometric and gene expression analyses were used to delineate the macrophage profile present in the kidneys during the early and resolution phase of IR injury with and without CSF-1 therapy. We thus provide evidence that CSF-1 recruits macrophages to the reparative site and influences their phenotype, partly through an insulin-like growth factor (IGF)-1 signaling response. Therefore, macrophages under the stimulus of CSF-1 in an acute setting of renal disease markedly accelerate renal cell replacement and tissue remodeling while attenuating downstream interstitial extracellular matrix accumulation.     

Microglia/macrophages migrate through retinal epithelium barrier by a transcellular route in diabetic retinopathy: role of PKCζ in the Goto Kakizaki rat model

Diabetic retinopathy is associated with ocular inflammation, leading to retinal barrier breakdown, macular edema, and visual cell loss. We investigated the molecular mechanisms involved in microglia/macrophages trafficking in the retina and the role of protein kinase Cζ (PKCζ) in this process. Goto Kakizaki (GK) rats, a model for spontaneous type 2 diabetes were studied until 12 months of hyperglycemia. Up to 5 months, sparse microglia/macrophages were detected in the subretinal space, together with numerous pores in retinal pigment epithelial (RPE) cells, allowing inflammatory cell traffic between the retina and choroid. Intercellular adhesion molecule-1 (ICAM-1), caveolin-1 (CAV-1), and PKCζ were identified at the pore border. At 12 months of hyperglycemia, the significant reduction of pores density in RPE cell layer was associated with microglia/macrophages accumulation in the subretinal space together with vacuolization of RPE cells and disorganization of photoreceptors outer segments. The intraocular injection of a PKCζ inhibitor at 12 months reduced iNOS expression in microglia/macrophages and inhibited their migration through the retina, preventing their subretinal accumulation. We show here that a physiological transcellular pathway takes place through RPE cells and contributes to microglia/macrophages retinal trafficking. Chronic hyperglycemia causes alteration of this pathway and subsequent subretinal accumulation of activated microglia/macrophages.     

Thrombolyse intraveineuse par rt-PA des accidents vasculaires cérébraux ischémiques : l’expérience de l’unité neurovasculaire de Nice

Introduction

Intravenous thrombolysis with rt-Pa in stroke has been approved in France since 2002. We report an evaluation of our practice. We have tried to identify predictive factors of dependence and death, and to compare our results with the data of the literature.

Patients and method

All patients treated with intravenous rt-PA within the first 270 min after the stroke onset were included. Univariate, then multivariate analyses were performed to determine the variables influencing the functional outcome at 3 months follow-up, according to a dichotomy established from the modified Rankin scale.

Results

One hundred and forty-two patients were included in this study (mean initial National Institute of Health Stroke Scale [NIHSS]: 15). Fifty percent had a Rankin score higher than 2 at 3 months follow-up. NIHSS above 12, glycemia of at least 120 mg/l, and systolic blood pressure above 160 mmHg at admission were identified as independent predictive factors of poor functional outcome. Less than 4 points decrease of NIHSS proved to be a simple and early predictor of poor functional outcome at 3 months follow-up.

Conclusions

In terms of safety and efficacy the data issuing from the daily activity of our stroke unit are comparable with those of clinical trials.     

Genetic Variant in HK1 Is Associated With a Proanemic State and A1C but Not Other Glycemic Control�CRelated Traits

OBJECTIVE

A1C is widely considered the gold standard for monitoring effective blood glucose levels. Recently, a genome-wide association study reported an association between A1C and rs7072268 within HK1 (encoding hexokinase 1), which catalyzes the first step of glycolysis. HK1 deficiency in erythrocytes (red blood cells [RBCs]) causes severe nonspherocytic hemolytic anemia in both humans and mice.

RESEARCH DESIGN AND METHODS

The contribution of rs7072268 to A1C and the RBC-related traits was assessed in 6,953 nondiabetic European participants. We additionally analyzed the association with hematologic traits in 5,229 nondiabetic European individuals (in whom A1C was not measured) and 1,924 diabetic patients. Glucose control–related markers other than A1C were analyzed in 18,694 nondiabetic European individuals. A type 2 diabetes case-control study included 7,447 French diabetic patients.

RESULTS

Our study confirms a strong association between the rs7072268–T allele and increased A1C (β = 0.029%; P = 2.22 × 10⁻⁷). Surprisingly, despite adequate study power, rs7072268 showed no association with any other markers of glucose control (fasting- and 2-h post-OGTT–related parameters, n = 18,694). In contrast, rs7072268–T allele decreases hemoglobin levels (n = 13,416; β = −0.054 g/dl; P = 3.74 × 10⁻⁶) and hematocrit (n = 11,492; β = −0.13%; P = 2.26 × 10⁻⁴), suggesting a proanemic effect. The T allele also increases risk for anemia (836 cases; odds ratio 1.13; P = 0.018).

CONCLUSIONS

HK1 variation, although strongly associated with A1C, does not seem to be involved in blood glucose control. Since HK1 rs7072268 is associated with reduced hemoglobin levels and favors anemia, we propose that HK1 may influence A1C levels through its anemic effect or its effect on glucose metabolism in RBCs. These findings may have implications for type 2 diabetes diagnosis and clinical management because anemia is a frequent complication of the diabetes state.Type 2 diabetes is a major source of early excess morbidity and mortality, which result from lack of adequate blood glucose control in most diabetic patients (1). In the absence of widely available continuous glucose monitoring, the A1C assay has become the most popular index to evaluate the efficiency of type 2 diabetes treatments on long-term blood glucose control (2,3). A1C, which is formed through the nonenzymatic attachment of glucose to the NH₂-terminal of the β-chain of hemoglobin, is indeed commonly considered a surrogate marker of mean blood glucose concentration over the previous 8–12 weeks (i.e., a 120-day life span of erythrocytes) (4). Furthermore, the A1C assay is often used for confirming type 2 diabetes diagnosis when fasting plasma glucose (FPG) is in the pre-diabetes range (6.1 ≤ FPG <7.0 mmol/l, defining normal glycemia and overt diabetes, respectively [2]), as postprandial or post–glucose load measurements of blood glucose are difficult to widely apply in clinical practice. However, the A1C measurement displays well-known caveats, such as genetically inherited hemoglobin defects or erythrocyte (red blood cell [RBC]) life span heterogeneity in hematologically normal people, that would oblige the use of more complex measurement of glycated serum proteins or fructosamine as a surrogate of blood glucose levels (5,6).Thus far, several genome-wide association (GWA) studies have identified 22 genes or loci, increasing the risk for type 2 diabetes or modulating FPG levels (7–19). Recently, Pare et al. (20) reported a single nucleotide polymorphism (SNP), rs7072268, at the hexokinase 1 (HK1) locus (chr10q22) that strongly associates with increased A1C in a nondiabetic population. The four isozymes of the hexokinase family (HK1, HK2, HK3, and glucokinase) contribute to commit glucose to the glycolytic pathway. The predominant HK1 isozyme is expressed in the vast majority of cells and tissues, including cells that are strictly dependent on glucose uptake for their metabolic needs (21). Importantly, while most tissues express more than one HK isozyme, RBC glucose metabolism only depends on HK1 activity (22). In humans, mutations including nonsynonymous substitutions in the active site of HK1 and intragenic deletions have been shown to cause HK1 enzymatic deficiency associated with autosomal recessive severe nonspherocytic hemolytic anemia (21,23–25). A similar phenotype has been described in the Downeast Anemia (dea) mice displaying HK1 deficiency (22).Based on these observations, we postulated that HK1 genetic variation may modulate the maintenance of the RBC pool and thus indirectly alter A1C measurements independently of the ambient blood glucose concentration. We evaluated this hypothesis by assessing the impact of HK1 rs7072268 on A1C, other glucose control-related traits, type 2 diabetes risk, and RBC-related parameters in several prospective and case-control European cohorts. Our data suggest that HK1 variation through its anemic effect impairs A1C assays, which may have important clinical implications for both type 2 diabetes diagnosis and management because anemia is commonly associated with diabetes.     

Hypertension in people with diabetes and the metabolic syndrome: Pathophysiologic insights and therapeutic update

Hypertension (HTN) and type 2 diabetes mellitus (T2DM) are emerging as epidemics of the 21st century and are important components of the metabolic syndrome (MS). Evidence demonstrates a relationship between HTN, T2DM, and several vascular and metabolic abnormalities that are components of the MS. HTN affects nearly 70 million Americans and over one billion worldwide; likewise, the MS affects 44% of the US population above the age of 60 years and is rapidly increasing. HTN associated with the MS has certain pathophysiologic characteristics that provide clinical challenges. There is growing evidence that tissue activation of the renin-angiotensin system contributes to endothelial dysfunction, microalbuminuria, insulin resistance, and subsequent increased risk for cardiovascular and chronic kidney disease. The notion that HTN is a metabolic as well as a vascular disease provides a new treatment paradigm.     

Inhaled corticosteroids in chronic obstructive pulmonary disease

The effectiveness of inhaled corticosteroids (ICS) in patients with chronic obstructive pulmonary disease (COPD) remains controversial. Randomized controlled trials, meta-analyses, medication withdrawal studies, and observational reports have examined this question, with mixed results. Observational studies have been subject to criticism because of study design involving immortal time bias. Some randomized controlled trials suggest small benefits in lung function and health status, and a reduction in the rate of acute exacerbations of COPD and mortality, but their incomplete follow-up and statistical methods have been criticized. The greatest benefits of ICS in COPD have been reported with use of ICS and long-acting beta-agonist combination therapy, although no benefit was found for the primary outcome studied under the most rigorous methodology by the recent TORCH and Optimal randomized trials. Thus, although future randomized trials will need to be conducted with the most rigorous methodology for all outcomes, much uncertainty remains regarding the potential benefits of ICS in COPD.     

Multidetector computed tomography for the detection of left atrial appendage thrombus: a comparative study with transesophageal echocardiography

OBJECTIVE: To determine the diagnostic performance of multidetector computed tomography (MDCT) for the detection of left atrial appendage (LAA) thrombus as compared with transesophageal echocardiography. METHODS: Multidetector computed tomography was evaluated in 43 patients qualitatively for the presence or absence of a filling defect in the LAA and compared with transesophageal echocardiography. Additionally, a ratio of the mean computed tomographic attenuation in the LAA apex to the mean computed tomographic attenuation in the aortic root was used for quantitative evaluation. RESULTS: A filling defect visualized in the LAA by MDCT corresponded to a sensitivity of 70% (7/10), a specificity of 82% (27/33), and a negative predictive value of 90% (27/30) for detection of LAA thrombus. When using quantitative parameters, MDCT demonstrated a sensitivity of 80% (8/10), a specificity of 73% (24/33), and a negative predictive value of 92% (24/26). Multidetector computed tomography was not able to differentiate LAA thrombus from spontaneous echo contrast by either visual evaluation or by quantitative parameters. CONCLUSIONS: Multidetector computed tomography remains limited for the detection of LAA thrombus. However, a subgroup of patients at very high risk for LAA thrombus may benefit from the high negative predictive value of cardiac MDCT.