Dysfonctionnement systémique de la différenciation ostéoblastique des cellules souches adipeuses des patients atteints de myélome multiple

International audienceMultiple myeloma is characterized by bone lesions linked to increased osteoclast and decreased osteoblast activities. In particular, the osteoblast differentiation of bone marrow-derived stem cells (MSC) is impaired. Among the potential therapeutic tools for counteracting bone lesions, adipose-derived stem cells (ASC) could represent an appealing source for regenerative medicine due to their similar characteristics with MSC. Our study is among the first giving detailed insights into the osteoblastogenic capacities of ASC isolated by fat aspiration from myeloma patients (MM-ASC) compared to healthy subjects (HD-ASC). We showed that MM-ASC and HD-ASC exhibited comparable morphology, proliferative capacity, and immunophenotype. Unexpectedly, although normal in adipocyte differentiation, MM-ASC present a defective osteoblast differentiation, as indicated by less calcium deposition, decreased alkaline phosphatase activity, and downregulation of RUNX2 and osteocalcin. Furthermore, these ASC-derived osteoblasts displayed enhanced senescence, as shown by an increased β-galactosidase activity and cell cycle inhibitors expression (p16 INK4A , p21 WAF1/CIP1 .), associated with a markedly increased expression of DKK1, a major inhibitor of osteoblastogenesis in multiple myeloma. Interestingly, inhibition of DKK1 attenuated senescence and rescued osteoblast differentiation, highlighting its key role. Our findings show, for the first time, Cells 2019, 8, 441 2 of 16 that multiple myeloma is a systemic disease and suggest that ASC from patients would be unsuitable for tissue engineering designed to treat myeloma-associated bone disease.Le myélome multiple est caractérisé par des lésions osseuses liées à une augmentation de l'activité ostéoclastique et à une diminution de l'activité ostéoblastique. En particulier, la différenciation ostéoblastique des cellules souches issues de la moelle osseuse (CSM) est altérée. Parmi les outils thérapeutiques potentiels pour contrer les lésions osseuses, les cellules souches dérivées de l'adipeux (CSA) pourraient représenter une source intéressante pour la médecine régénérative en raison de leurs caractéristiques similaires à celles des cellules MSC. Notre étude est l'une des premières à donner un aperçu détaillé des capacités ostéoblastogènes de l'ASC isolée par aspiration graisseuse chez les patients atteints de myélome (MM-ASC) par rapport aux sujets sains (HD-ASC). Nous avons montré que le MM-ASC et le HD-ASC présentaient une morphologie, une capacité proliférative et un immunophénotype comparables. De façon inattendue, bien que normal dans la différenciation adipocytaire, le MM-ASC présente une différenciation ostéoblastique défectueuse, comme l'indiquent la diminution des dépôts de calcium, la diminution de l'activité des phosphatases alcalines et la régulation négative de RUNX2 et de l'ostéocalcine. De plus, ces ostéoblastes dérivés de l'ASC présentaient une sénescence accrue, comme en témoigne l'augmentation de l'activité de la β-galactosidase et de l'expression des inhibiteurs du cycle cellulaire (p16 INK4A, p21 WAF1/CIP1 .), associée à une expression nettement accrue du DKK1, un inhibiteur majeur de l'ostéoblastogenèse dans les myélomes multiples. Il est intéressant de noter que l'inhibition du DKK1 a atténué la sénescence et sauvé la différenciation des ostéoblastes, soulignant son rôle clé. Nos résultats montrent, pour la première fois, que le myélome multiple est une maladie systémique et suggèrent que les cellules 2019, 8, 441 2 sur 16 ne conviennent pas au génie tissulaire conçu pour traiter les maladies osseuses associées au myélome

Adipose Tissue Is a Neglected Viral Reservoir and an Inflammatory Site during Chronic HIV and SIV Infection

International audienceTwo of the crucial aspects of human immunodeficiency virus (HIV) infection are (i) viral persistence in reservoirs (precluding viral eradication) and (ii) chronic inflammation (directly associated with all-cause morbidities in antiretroviral therapy (ART)-controlled HIV-infected patients). The objective of the present study was to assess the potential involvement of adipose tissue in these two aspects. Adipose tissue is composed of adipocytes and the stromal vascular fraction (SVF); the latter comprises immune cells such as CD4+ T cells and macrophages (both of which are important target cells for HIV). The inflammatory potential of adipose tissue has been extensively described in the context of obesity. During HIV infection, the inflammatory profile of adipose tissue has been revealed by the occurrence of lipodystrophies (primarily related to ART). Data on the impact of HIV on the SVF (especially in individuals not receiving ART) are scarce. We first analyzed the impact of simian immunodeficiency virus (SIV) infection on abdominal subcutaneous and visceral adipose tissues in SIVmac251 infected macaques and found that both adipocytes and adipose tissue immune cells were affected. The adipocyte density was elevated, and adipose tissue immune cells presented enhanced immune activation and/or inflammatory profiles. We detected cell-associated SIV DNA and RNA in the SVF and in sorted CD4+ T cells and macrophages from adipose tissue. We demonstrated that SVF cells (including CD4+ T cells) are infected in ART-controlled HIV-infected patients. Importantly, the production of HIV RNA was detected by in situ hybridization, and after the in vitro reactivation of sorted CD4+ T cells from adipose tissue. We thus identified adipose tissue as a crucial cofactor in both viral persistence and chronic immune activation/inflammation during HIV infection. These observations open up new therapeutic strategies for limiting the size of the viral reservoir and decreasing low-grade chronic inflammation via the modulation of adipose tissue-related pathway

Inhibition of FGF receptor signalling in Xenopus oocytes: differential effect of Grb7, Grb10 and Grb14

AbstractThe role of Grb7 adapters, Grb7, Grb10, and Grb14, was investigated in Xenopus oocytes expressing fibroblast growth factor receptors (FGFR). FGF-induced maturation of FGFR-expressing oocytes was blocked by previous injection of Grb7 or Grb14, but not Grb10. This effect correlated with Grb7/14 binding to the receptor, and inhibition of the Ras-dependent pathway. Interestingly, the phosphorylated insulin receptor interacting region (PIR) and Src 2 homology domains (SH2) of Grb7 and Grb14 were differently implicated in the inhibition of FGFR signalling. This study provided further evidence for specificity of the biological action of the Grb7 adapters on receptor tyrosine kinase signalling

Contribution of Adipose Tissue to the Chronic Immune Activation and Inflammation Associated With HIV Infection and Its Treatment

International audienceWhite adipose tissue (AT) contributes significantly to inflammation - especially in the context of obesity. Several of AT's intrinsic features favor its key role in local and systemic inflammation: (i) large distribution throughout the body, (ii) major endocrine activity, and (iii) presence of metabolic and immune cells in close proximity. In obesity, the concomitant pro-inflammatory signals produced by immune cells, adipocytes and adipose stem cells help to drive local inflammation in a vicious circle. Although the secretion of adipokines by AT is a prime contributor to systemic inflammation, the lipotoxicity associated with AT dysfunction might also be involved and could affect distant organs. In HIV-infected patients, the AT is targeted by both HIV infection and antiretroviral therapy (ART). During the primary phase of infection, the virus targets AT directly (by infecting AT CD4 T cells) and indirectly (via viral protein release, inflammatory signals, and gut disruption). The initiation of ART drastically changes the picture: ART reduces viral load, restores (at least partially) the CD4 T cell count, and dampens inflammatory processes on the whole-body level but also within the AT. However, ART induces AT dysfunction and metabolic side effects, which are highly dependent on the individual molecules and the combination used. First generation thymidine reverse transcriptase inhibitors predominantly target mitochondrial DNA and induce oxidative stress and adipocyte death. Protease inhibitors predominantly affect metabolic pathways (affecting adipogenesis and adipocyte homeostasis) resulting in insulin resistance. Recently marketed integrase strand transfer inhibitors induce both adipocyte adipogenesis, hypertrophy and fibrosis. It is challenging to distinguish between the respective effects of viral persistence, persistent immune defects and ART toxicity on the inflammatory profile present in ART-controlled HIV-infected patients. The host metabolic status, the size of the pre-established viral reservoir, the quality of the immune restoration, and the natural ageing with associated comorbidities may mitigate and/or reinforce the contribution of antiretrovirals (ARVs) toxicity to the development of low-grade inflammation in HIV-infected patients. Protecting AT functions appears highly relevant in ART-controlled HIV-infected patients. It requires lifestyle habits improvement in the absence of effective anti-inflammatory treatment. Besides, reducing ART toxicities remains a crucial therapeutic goal

Metabolic complications affecting adipose tissue, lipid and glucose metabolism associated with HIV antiretroviral treatment

International audienceIntroduction: Efficient antiretroviral-treatment (ART) generally allows control of HIV infection. However, persons-living-with-HIV (PLWH), when aging, present a high prevalence of metabolic diseases.Area covered: Altered adiposity, dyslipidemias, insulin resistance, diabetes, and their consequences are prevalent in PLWH and could be partly related to ART.Expert opinion: At first, personal and lifestyle factors are involved in the onset of these complications. The persistence of HIV in tissue reservoirs could synergize with some ART and enhance metabolic disorders. Altered fat repartition, diagnosed as lipodystrophy, has been related to first-generation nucleoside-reverse-transcriptase-inhibitors (NRTIs) (stavudine zidovudine) and some protease inhibitors (PIs). Recently, use of some integrase-inhibitors (INSTI) resulted in weight/fat gain, which represents a worrisome unresolved situation. Lipid parameters were affected by some first-generation NRTIs, non-NRTIs (efavirenz) but also PIs boosted by ritonavir, with increased total and LDL-cholesterol and triglycerides. Insulin resistance is common associated with abdominal obesity. Diabetes incidence, high with first-generation-ART (zidovudine, stavudine, didanosine, indinavir) has declined with contemporary ART close to that of the general population. Metabolic syndrome, a dysmetabolic situation with central obesity and insulin resistance, and liver steatosis are common in PLWH and could indirectly result from ART-associated fat gain and insulin resistance. All these dysmetabolic situations increase the atherogenic cardiovascular risk

The Adapter Protein ZIP Binds Grb14 and Regulates Its Inhibitory Action on Insulin Signaling by Recruiting Protein Kinase Cζ

Grb14 is a member of the Grb7 family of adapters and acts as a negative regulator of insulin-mediated signaling. Here we found that the protein kinase Cζ (PKCζ) interacting protein, ZIP, interacted with Grb14. Coimmunoprecipitation experiments demonstrated that ZIP bound to both Grb14 and PKCζ, thereby acting as a link in the assembly of a PKCζ-ZIP-Grb14 heterotrimeric complex. Mapping studies indicated that ZIP interacted through its ZZ zinc finger domain with the phosphorylated insulin receptor interacting region (PIR) of Grb14. PKCζ phosphorylated Grb14 under in vitro conditions and in CHO-IR cells as demonstrated by in vivo labeling experiments. Furthermore, Grb14 phosphorylation was increased under insulin stimulation, suggesting that the PKCζ-ZIP-Grb14 complex is involved in insulin signaling. The PIR of Grb14, which also interacts with the catalytic domain of the insulin receptor (IR) and inhibits its activity, was preferentially phosphorylated by PKCζ. Interestingly, the phosphorylation of Grb14 by PKCζ increased its inhibitory effect on IR tyrosine kinase activity in vitro. The role of ZIP and Grb14 in insulin signaling was further investigated in vivo in Xenopus laevis oocytes. In this model, ZIP potentiated the inhibitory action of Grb14 on insulin-induced oocyte maturation. Importantly, this effect required the recruitment of PKCζ and the phosphorylation of Grb14, providing in vivo evidences for a regulation of Grb14-inhibitory action by ZIP and PKCζ. Together, these results suggest that Grb14, ZIP, and PKCζ participate in a new feedback pathway of insulin signaling

Human lipodystrophies: genetic and acquired diseases of adipose tissue.

International audienceHuman lipodystrophies represent a heterogeneous group of diseases characterized by generalized or partial fat loss, with fat hypertrophy in other depots when partial. Insulin resistance, dyslipidemia and diabetes are generally associated, leading to early complications. Genetic forms are uncommon: recessive generalized congenital lipodystrophies result in most cases from mutations in the genes encoding seipin or the 1-acyl-glycerol-3-phosphate-acyltransferase 2(AGPAT2). Dominant partial familial lipodystrophies result from mutations in genes encoding the nuclear protein lamin A/C or the adipose transcription factor PPARgamma. Importantly, lamin A/Cmutations are also responsible for metabolic laminopathies, resembling the metabolic syndrome and progeria, a syndrome of premature aging. A number of lipodystrophic patients remain undiagnosed at the genetic level. Acquired lipodystrophy can be generalized, resembling congenital forms, or partial, as the Barraquer-Simons syndrome, with loss of fat in the upper part of the body contrasting with accumulation in the lower part. Although their etiology is generally unknown, they could be associated with signs of autoimmunity. The most common forms of lipodystrophies are iatrogenic. In human immunodeficiency virus-infected patients, some first-generation antiretroviral drugs were strongly related with peripheral lipoatrophy and metabolic alterations. Partial lipodystrophy also characterize patients with endogenous or exogenous long-term corticoid excess. Treatment of fat redistribution can sometimes benefit from plastic surgery. Lipid and glucose alterations are difficult to control leading to early occurrence of diabetic, cardiovascular and hepatic complications

Prolonged Antiretroviral Treatment Induces Adipose Tissue Remodelling Associated with Mild Inflammation in SIV-Infected Macaques

During chronic SIV/HIV infection, adipose tissue (AT) is the target of both antiretroviral treatment (ART) and the virus. AT might subsequently contribute to the low-grade systemic inflammation observed in patients on ART. To evaluate the inflammatory profile of AT during chronic SIV/HIV infection, we assayed subcutaneous and visceral abdominal AT from non-infected (SIV−, control), ART-naïve SIV-infected (SIV+) and ART-controlled SIV-infected (SIV+ART+) cynomolgus macaques for the mRNA expression of genes coding for factors related to inflammation. Significant differences were observed only when comparing the SIV+ART+ group with the SIV+ and/or SIV− groups. ART-treated infection impacted the metabolic fraction (with elevated expression of PPARγ and CEBPα), the extracellular matrix (with elevated expression of COL1A2 and HIF-1α), and the inflammatory profile. Both pro- and anti-inflammatory signatures were detected in AT, with greater mRNA expression of anti-inflammatory markers (adiponectin and CD163) and markers associated with inflammation (TNF-α, Mx1, CCL5 and CX3CL1). There were no intergroup differences in other markers (IL-6 and MCP-1). In conclusion, we observed marked differences in the immune and metabolic profiles of AT in the context of an ART-treated, chronic SIV infection; these differences were related more to ART than to SIV infection per se