Local proliferation of macrophages in adipose tissue during obesity-induced inflammation

Aims/hypothesis

Obesity is frequently associated with low-grade inflammation of adipose tissue (AT), and the increase in adipose tissue macrophages (ATMs) is linked to an increased risk of type 2 diabetes. Macrophages have been regarded as post-mitotic, but recent observations have challenged this view. In this study, we tested the hypothesis that macrophages proliferate within AT in diet-induced obesity in mice and humans.

Methods

We studied the expression of proliferation markers by immunofluorescence, PCR and flow cytometry in three different models of mouse obesity as well as in humans (n?=?239). The cell fate of dividing macrophages was assessed by live imaging of AT explants.

Results

We show that ATMs undergo mitosis within AT, predominantly within crown-like structures (CLS). We found a time-dependent increase in ATM proliferation when mice were fed a high-fat diet. Upregulation of CD206 and CD301 in proliferating ATMs indicated preferential M2 polarisation. Live imaging within AT explants from mice revealed that macrophages emigrate out of the CLS to become resident in the interstitium. In humans, we confirmed the increased expression of proliferation markers of CD68⁺ macrophages in CLS and demonstrated a higher mRNA expression of the proliferation marker Ki67 in AT from obese patients.

Conclusions/interpretation

Local proliferation contributes to the increase in M2 macrophages in AT. Our data confirm CLS as the primary site of proliferation and a new source of ATMs and support a model of different recruitment mechanisms for classically activated (M1) and alternatively activated (M2) macrophages in obesity.     

Mitochondrial hexokinase II (HKII) and phosphoprotein enriched in astrocytes (PEA15) form a molecular switch governing cellular fate depending on the metabolic state

The metabolic state of a cell is a key determinant in the decision to live and proliferate or to die. Consequently, balanced energy metabolism and the regulation of apoptosis are critical for the development and maintenance of differentiated organisms. Hypoxia occurs physiologically during development or exercise and pathologically in vascular disease, tumorigenesis, and inflammation, interfering with homeostatic metabolism. Here, we show that the hypoxia-inducible factor (HIF)-1-regulated glycolytic enzyme hexokinase II (HKII) acts as a molecular switch that determines cellular fate by regulating both cytoprotection and induction of apoptosis based on the metabolic state. We provide evidence for a direct molecular interactor of HKII and show that, together with phosphoprotein enriched in astrocytes (PEA15), HKII inhibits apoptosis after hypoxia. In contrast, HKII accelerates apoptosis in the absence of PEA15 and under glucose deprivation. HKII both protects cells from death during hypoxia and functions as a sensor of glucose availability during normoxia, inducing apoptosis in response to glucose depletion. Thus, HKII-mediated apoptosis may represent an evolutionarily conserved altruistic mechanism to eliminate cells during metabolic stress to the advantage of a multicellular organism.     

Orbital floor reconstruction with resorbable polydioxanone implants

Many different materials are proposed for reconstruction of traumatic orbital floor defects. Donor-site morbidity of autologous transplants and infections or extrusions of nonresorbable implants lead to a widespread use of resorbable, alloplastic materials such as polydioxanone (PDS). The goal of this study was to evaluate the prevalence of orbital floor fracture-related problems after surgical treatment using PDS. Ophthalmologic and clinical examinations were performed at 194 patients before orbital floor reconstruction, 14 days and 6 months after surgery (approximate defect sizes: <1 cm2, n=50; 1-2 cm2, n=97; >2 cm2, n=47). Clinical findings including the ocular motility, the sensibility of the infraorbital nerve, and the position of the globe were evaluated. For statistical analysis of categorical data, confidence intervals of percentages were determined. Linear relationships between 2 variables were assessed with Pearson correlation analysis. A reduced ocular motility was diagnosed in 60 patients (31%) before surgery; in 14 patients (7%), 2 weeks; and in 10 patients (5%), 6 months after surgery. Infraorbital hypesthesia was found in 120 patients (62%) before surgery; in 47 patients (24%), 2 weeks; and in 35 patients (18%), 6 months after surgery. An enophthalmos was present in 10 patients (5%) before surgery, and in 4 patients (2%), 6 months after surgery. Our data suggest that PDS is a suitable implant for orbital floor reconstruction with acceptable low rates of infraorbital hypesthesia, bulbus motility disturbances, and enophthalmos. Polydioxanone can also be used for orbital floor defects exceeding 2 cm2.     

On the symmetry of siblings: automated single-cell tracking to quantify the behavior of hematopoietic stem cells in a biomimetic setup

The interplay between hematopoietic stem and progenitor cells (HSPC) and their local microenvironment is a key mechanism for the organization of hematopoiesis. To quantitatively study this process, a time-resolved analysis of cellular dynamics at the single-cell level is an essential prerequisite. One way to generate sufficient amounts of appropriate data is automatic single-cell tracking using time-lapse video microscopy. We describe and apply newly developed computational algorithms that allow for an automated generation of high-content data of single-cell characteristics at high temporal and spatial resolution, together with the reconstruction and statistical evaluation of complete genealogical histories. This methodology has been applied to the particular example of purified primary human HSPCs in bioengineered culture conditions. The combination of genealogical information and dynamic profiles of cellular properties identified a marked symmetry between sibling HSPCs regarding cell cycle time, but also migration speed and growth kinetics. Furthermore, we demonstrate that this symmetry of HSPC siblings can be altered by exogenous cues of the local biomimetic microenvironment. Using the example of HSPC growth in biomimetic culture systems, we show that our approach provides a valuable tool for the quantitative analysis of dynamic single-cell features under defined in?vitro conditions, allowing for integration of functional and genealogical data. The efficiency and accuracy of our approach pave the way for new and intriguing insights into the organizational principles of developmental patterns and the respective influence of exogenous cues not limited to the study of primary HSPCs.     

Treatment with Thalidomide and Cyclophosphamide (TCID) is Superior to Vincristine (VID) and to Vinorelbine (VRID) Regimens in Patients with Refractory or Recurrent Multiple Myeloma

Treatment of relapsed or refractory multiple myeloma remains a challenge and novel treatment regimen are required. Here, a matched pair analysis was performed comparing TCID (thalidomide, cyclophosphamide, idarubicin, dexamethasone) treatment to the treatment of patients with VID (vincristine, idarubicin, dexamethasone) or with VRID (vinorelbine, idarubicin, dexamethasone) for relapsed or refractory multiple myeloma. In total, 197 patients were enrolled in multicenter trials. After matching for important prognostic variables 46 matched-pairs (total of 138 patients) could be analysed with regard to survival, toxicity and efficacy. Interestingly, a significant improvement of overall response rate (ORR) for TCID treatment compared to VID and VRID was found. In addition, TCID treatment also led to a significantly higher overall survival (OS) as well as progression-free survival (PFS) compared to VID and VRID. In conclusion, TCID treatment appears to be superior to VRID and VID treatment in patients with progressive or refractory myeloma.     

Severe case and literature review of primary erythromelalgia: novel SCN9A gene mutation

Erythromelalgia is a rare clinical syndrome characterized by intermittent heat, redness, swelling and pain more commonly affecting the lower extremities. Symptoms are mostly aggravated by warmth and are eased by a cold temperature. In some cases, symptoms can be very severe and disabling. Erythromelalgia can be classified as either familial or sporadic, with the familial form inherited in an autosomal dominant manner. Recently, there has been a lot of progress in studying Na(v)1.7 sodium channels (expressed mostly in the sympathetic and nociceptive small-diameter sensory neurons of the dorsal root ganglion) and different mutations affecting the encoding SCN9A gene that leads to channelopathies responsible for some disorders, including primary erythromelalgia. We present a severe case of progressive primary erythromelalgia caused by a new de novo heterozygous missense mutation (c.2623C>G) of the SCN9A gene which substitutes glutamine 875 by glutamic acid (p.Q875E). To our knowledge, this mutation has not been previously reported in the literature. We also provided a short literature review about erythromelalgia and Na(v) sodium channelopathies.