Characterization of human mesenchymal stem cell secretome at early steps of adipocyte and osteoblast differentiation

<p>Abstract</p> <p>Background</p> <p>It is well established that adipose tissue plays a key role in energy storage and release but is also a secretory organ and a source of stem cells. Among different lineages, stem cells are able to differentiate into adipocytes and osteoblasts. As secreted proteins could regulate the balance between both lineages, we aimed at characterizing the secretome of human multipotent adipose-derived stem cell (hMADS) at an early step of commitment to adipocytes and osteoblasts.</p> <p>Results</p> <p>A proteomic approach, using mono-dimensional electrophoresis and tandem mass spectrometry, allowed us to identify a total of 73 proteins at day 0 and day 3 of adipocyte and osteoblast differentiation. Analysis of identified proteins showed that 52 % corresponded to classical secreted proteins characterized by a signal peptide, that 37 % previously described in the extracellular compartment were devoid of signal peptide and that 11 % neither exhibited a signal peptide nor had been previously described extracellularly. These proteins were classified into 8 clusters according to their function. Quantitative analysis has been performed for 8 candidates: PAI-1, PEDF, BIGH3, PTX3, SPARC, ENO1, GRP78 and MMP2. Among them, PAI-1 was detected at day 0 and day 3 of osteoblast differentiation but never in adipocyte secretome. Furthermore we showed that PAI-1 mRNA was down-regulated in the bone of ovariectomized mice.</p> <p>Conclusion</p> <p>Given its regulation during the early events of hMADS cell differentiation and its status in ovariectomized mice, PAI-1 could play a role in the adipocyte/osteoblast balance and thus in bone diseases such as osteoporosis.</p

Dystrophy-associated caveolin-3 mutations reveal that caveolae couple IL6/STAT3 signaling with mechanosensing in human muscle cells

Caveolin-3 is the major structural protein of caveolae in muscle. Mutations in the CAV3 gene cause different types of myopathies with altered membrane integrity and repair, expression of muscle proteins, and regulation of signaling pathways. We show here that myotubes from patients bearing the CAV3P28L and R26Q mutations present a dramatic decrease of caveolae at the plasma membrane, resulting in abnormal response to mechanical stress. Mutant myotubes are unable to buffer the increase in membrane tension induced by mechanical stress. This results in impaired regulation of the IL6/STAT3 signaling pathway leading to its constitutive hyperactivation and increased expression of muscle genes. These defects are fully reversed by reassembling functional caveolae through expression ofcaveolin-3. Our study reveals that under mechanical stress the regulation of mechan-oprotection by caveolae is directly coupled with the regulation of IL6/STAT3 signaling inmuscle cells and that this regulation is absent in Cav3-associated dystrophic patients

Neuropeptide Y modulates olfactory mucosa responses to odorant in fasted rat

International audienc

Neuropeptide Y enhances olfactory mucosa responses to odorant in hungry rats

International audienceNeuropeptide Y (NPY) plays an important role in regulating appetite and hunger in vertebrates. In the hypothalamus, NPY stimulates food intake under the control of the nutritional status. Previous studies have shown the presence of NPY and receptors in rodent olfactory system, and suggested a neuroproliferative role. Interestingly, NPY was also shown to directly modulate olfactory responses evoked by a food-related odorant in hungry axolotls. We have recently demonstrated that another nutritional cue, insulin, modulates the odorant responses of the rat olfactory mucosa (OM). Therefore, the aim of the present study was to investigate the potential effect of NPY on rat OM responses to odorants, in relation to the animal’s nutritional state. We measured the potential NPY modulation of OM responses to odorant, using electro-olfactogram (EOG) recordings, in fed and fasted adult rats. NPY application significantly and transiently increased EOG amplitudes in fasted but not in fed rats. The effects of specific NPY-receptor agonists were similarly quantified, showing that NPY operated mainly through Y1 receptors. These receptors appeared as heterogeneously expressed by olfactory neurons in the OM, and western blot analysis showed that they were overexpressed in fasted rats. These data provide the first evidence that NPY modulates the initial events of odorant detection in the rat OM. Because this modulation depends on the nutritional status of the animal, and is ascribed to NPY, the most potent orexigenic peptide in the central nervous system, it evidences a strong supplementary physiological link between olfaction and nutritional processes

Modulation des réponses olfactives de la muqueuse de rats à jeun par le NPY

National audienc

Is the internal status able to modify olfactory message at the OM level ?

National audienc

Sensory-metabolic neuroendocrine crosstalk in the rat olfactory epithelium and buld

International audienceOlfaction influences food choice and intake. Conversely, the nutritional and metabolic status modifies odour detection. In an effort to understand the olfactory-metabolic crosstalk, we have localized orexigenic and anorexigenic hormones and their receptors in the olfactory epithelium and bulb of rats, and looked for their effect on the olfactory signal. 1) Concerning the orexigenic hormones: - in fasted rats, transcription of orexins (A & B) and their receptors (1 & 2) increased in the olfactory epithelium and, in the bulb, in mitral, periglomerular and granular cells. An orexin antagonist decreased locomotor activity of fasted animals, their time spent sniffing and bulb cells c-Fos response. Orexins also enhanced the amplitude of the olfactory epithelium electroolfactogram. - similarly, NPY enhanced the electroolfactogram amplitude (30%) in fasted rats, mainly through Y1 receptors and less through Y5. 2) Concerning the anorexigenic hormones: - in the olfactory epithelium, the transcription of leptin and its receptor (long and short forms) were enhanced by fasting. In fasted rats, leptin decreased locomotor activity, time spent sniffing and bulb cells c-Fos response, as well as electroolfactogram amplitude. - fasting induced an increase in the number of receptors in the olfactory epithelium, together with an increase in local insulin production. Interestingly, insulin decreased the electroolfactogram amplitude of the olfactory epithelium by 30%. These results are consistent with an enhanced interest, especially for food odours, in fasted animals, in contrast to decreased odour stimulation in satiated ones. Endly, we analyzed the olfactory epithelium transcriptome of fasted vs satiated rats. Fasting decreased transcription of immunity-related genes, perhaps in connection with stress, while it increased some transcripts related to cell-dynamics or signal transduction. Thus transcriptomic data were largely correlated with enhanced olfactory activity upon fastin

NPY effect is mimicked by Y₁ receptor agonist.

<p>Effects of MS or MS + Y₁R agonist (A), Y₂R agonist (B) or Y₅R agonist (C) treatments (1 µM) on the time course of EOG amplitudes in response to IA in fasted rats. Mean ± SEM values (n = 10, 5 and 10 rats, respectively for Y₁, Y₂ and Y₅ agonist) are expressed as % of control EOG recordings prior to treatment. (*P<0.05; **P<0.01).</p