No Effect of Dietary Fish Oil Supplementation on the Recruitment of Brown and Brite Adipocytes in Mice or Humans under Thermoneutral Conditions.

SCOPE: Brown and brite adipocytes within the mammalian adipose organ provide non-shivering thermogenesis and thus, have an exceptional capacity to dissipate chemical energy as heat. Polyunsaturated fatty acids (PUFA) of the n3-series, abundant in fish oil, have been repeatedly demonstrated to enhance the recruitment of thermogenic capacity in these cells, consequently affecting body adiposity and glucose tolerance. These effects are scrutinized in mice housed in a thermoneutral environment and in a human dietary intervention trial. METHODS AND RESULTS: Mice are housed in a thermoneutral environment eliminating the superimposing effect of mild cold-exposure on thermogenic adipocyte recruitment. Dietary fish oil supplementation in two different inbred mouse strains neither affects body mass trajectory nor enhances the recruitment of brown and brite adipocytes, both in the presence and absence of a ß3-adrenoreceptor agonist imitating the effect of cold-exposure on adipocytes. In line with these findings, dietary fish oil supplementation of persons with overweight or obesity fails to recruit thermogenic adipocytes in subcutaneous adipose tissue. CONCLUSION: Thus, the authors' data question the hypothesized potential of n3-PUFA as modulators of adipocyte-based thermogenesis and energy balance regulation.

The Rosmarinus Bioactive Compound Carnosic Acid Is a Novel PPAR Antagonist That Inhibits the Browning of White Adipocytes.

Thermogenic brown and brite adipocytes convert chemical energy from nutrients into heat. Therapeutics that regulate brown adipocyte recruitment and activity represent interesting strategies to control fat mass such as in obesity or cachexia. The peroxisome proliferator-activated receptor (PPAR) family plays key roles in the maintenance of adipose tissue and in the regulation of thermogenic activity. Activation of these receptors induce browning of white adipocyte. The purpose of this work was to characterize the role of carnosic acid (CA), a compound used in traditional medicine, in the control of brown/brite adipocyte formation and function. We used human multipotent adipose-derived stem (hMADS) cells differentiated into white or brite adipocytes. The expression of key marker genes was determined using RT-qPCR and western blotting. We show here that CA inhibits the browning of white adipocytes and favors decreased gene expression of thermogenic markers. CA treatment does not affect ß-adrenergic response. Importantly, the effects of CA are fully reversible. We used transactivation assays to show that CA has a PPARα/γ antagonistic action. Our data pinpoint CA as a drug able to control PPAR activity through an antagonistic effect. These observations shed some light on the development of natural PPAR antagonists and their potential effects on thermogenic response.

A Novel N-Substituted Valine Derivative with Unique Peroxisome Proliferator-Activated Receptor γ Binding Properties and Biological Activities.

A proprietary library of novel N-aryl-substituted amino acid derivatives bearing a hydroxamate head group allowed the identification of compound 3a that possesses weak proadipogenic and peroxisome proliferator-activated receptor γ (PPARγ) activating properties. The systematic optimization of 3a, in order to improve its PPARγ agonist activity, led to the synthesis of compound 7j (N-aryl-substituted valine derivative) that possesses dual PPARγ/PPARα agonistic activity. Structural and kinetic analyses reveal that 7j occupies the typical ligand binding domain of the PPARγ agonists with, however, a unique high-affinity binding mode. Furthermore, 7j is highly effective in preventing cyclin-dependent kinase 5-mediated phosphorylation of PPARγ serine 273. Although less proadipogenic than rosiglitazone, 7j significantly increases adipocyte insulin-stimulated glucose uptake and efficiently promotes white-to-brown adipocyte conversion. In addition, 7j prevents oleic acid-induced lipid accumulation in hepatoma cells. The unique biochemical properties and biological activities of compound 7j suggest that it would be a promising candidate for the development of compounds to reduce insulin resistance, obesity, and nonalcoholic fatty liver disease.

Oxytocin Controls Chondrogenesis and Correlates with Osteoarthritis.

This study investigated the relationship of oxytocin (OT) to chondrogenesis and osteoarthritis (OA). Human bone marrow and multipotent adipose-derived stem cells were cultured in vitro in the absence or presence of OT and assayed for mRNA transcript expression along with histological and immunohistochemical analyses. To study the effects of OT in OA in vivo, a rat model and a human cohort of 63 men and 19 women with hand OA and healthy controls, respectively, were used. The baseline circulating OT, interleukin-6, leptin, and oestradiol levels were measured, and hand X-ray examinations were performed for each subject. OT induced increased aggrecan, collagen (Col) X, and cartilage oligomeric matrix protein mRNA transcript levels in vitro, and the immunolabelling experiments revealed a normalization of Sox9 and Col II protein expression levels. No histological differences in lesion severity were observed between rat OA groups. In the clinical study, a multivariate analysis adjusted for age, body mass index, and leptin levels revealed a significant association between OA and lower levels of OT (odds ratio = 0.77; p = 0.012). Serum OT levels are reduced in patients with hand OA, and OT showed a stimulatory effect on chondrogenesis. Thus, OT may contribute to the pathophysiology of OA.

Identification of a Paracrine Signaling Mechanism Linking CD34high Progenitors to the Regulation of Visceral Fat Expansion and Remodeling.

Accumulation of visceral (VIS) is a predictor of metabolic disorders and insulin resistance. This is due in part to the limited capacity of VIS fat to buffer lipids allowing them to deposit in insulin-sensitive tissues. Mechanisms underlying selective hypertrophic growth and tissue remodeling properties of VIS fat are not well understood. We identified subsets of adipose progenitors (APs) unique to VIS fat with differential Cd34 expression and adipogenic capacity. VIS low (Cd34 low) APs are adipogenic, whereas VIS high (Cd34 high) APs are not. Furthermore, VIS high APs inhibit adipogenic differentiation of SUB and VIS low APs in vitro through the secretion of soluble inhibitory factor(s). The number of VIS high APs increased with adipose tissue expansion, and their abundance in vivo caused hypertrophic growth, fibrosis, inflammation, and metabolic dysfunction. This study unveils the presence of APs unique to VIS fat involved in the paracrine regulation of adipogenesis and tissue remodeling.

Positive Association of High Leptin Level and Abdominal Aortic Calcification in Men　- The Prospective MINOS Study.

BACKGROUND: Severe abdominal aortic calcification (AAC) points to high cardiovascular risk and leptin stimulates arterial calcification; however, clinical data on their association are scarce. We studied the link between serum leptin and AAC severity and progression, and the effect of smoking and lipid levels, on this association in men. Methods and Results: At baseline, 548 community-dwelling men aged 50-85 years underwent blood collection and lateral lumbar spine radiography. In 448 men, X-ray was repeated after 3 and 7.5 years. AAC was assessed using Kauppila's semiquantitative score. In multivariable models, high leptin was associated with higher odds of severe AAC (odds ratio [OR]=1.71 per SD, 95% confidence interval [CI]: 1.22-2.40). The odds of severe AAC were the highest in men who had elevated leptin levels and either were ever-smokers (OR=9.22, 95% CI: 3.43-24.78) or had hypertriglyceridemia (vs. men without these characteristics). Higher leptin was associated with greater AAC progression (OR=1.34 per SD, 95% CI: 1.04-1.74). The risk of AAC progression was the highest in men who had elevated leptin levels and either were current smokers or had high low-density lipoprotein-cholesterol levels (OR=5.91, 95% CI: 2.46-14.16 vs. men without these characteristics). These links remained significant after adjustment for baseline AAC and in subgroups defined according to smoking and low-density lipoprotein-cholesterol levels. CONCLUSIONS: In older men, high leptin levels are associated with greater severity and rapid progression of AAC independent of smoking, low-density lipoprotein-cholesterol or triglycerides.

Small non coding RNAs in adipocyte biology and obesity.

Obesity has reached epidemic proportions world-wide and constitutes a substantial risk factor for hypertension, type 2 diabetes, cardiovascular diseases and certain cancers. So far, regulation of energy intake by dietary and pharmacological treatments has met limited success. The main interest of current research is focused on understanding the role of different pathways involved in adipose tissue function and modulation of its mass. Whole-genome sequencing studies revealed that the majority of the human genome is transcribed, with thousands of non-protein-coding RNAs (ncRNA), which comprise small and long ncRNAs. ncRNAs regulate gene expression at the transcriptional and post-transcriptional level. Numerous studies described the involvement of ncRNAs in the pathogenesis of many diseases including obesity and associated metabolic disorders. ncRNAs represent potential diagnostic biomarkers and promising therapeutic targets. In this review, we focused on small ncRNAs involved in the formation and function of adipocytes and obesity.

An AMP-activated protein kinase-stabilizing peptide ameliorates adipose tissue wasting in cancer cachexia in mice.

Cachexia represents a fatal energy-wasting syndrome in a large number of patients with cancer that mostly results in a pathological loss of skeletal muscle and adipose tissue. Here we show that tumor cell exposure and tumor growth in mice triggered a futile energy-wasting cycle in cultured white adipocytes and white adipose tissue (WAT), respectively. Although uncoupling protein 1 (Ucp1)-dependent thermogenesis was dispensable for tumor-induced body wasting, WAT from cachectic mice and tumor-cell-supernatant-treated adipocytes were consistently characterized by the simultaneous induction of both lipolytic and lipogenic pathways. Paradoxically, this was accompanied by an inactivated AMP-activated protein kinase (Ampk), which is normally activated in peripheral tissues during states of low cellular energy. Ampk inactivation correlated with its degradation and with upregulation of the Ampk-interacting protein Cidea. Therefore, we developed an Ampk-stabilizing peptide, ACIP, which was able to ameliorate WAT wasting in vitro and in vivo by shielding the Cidea-targeted interaction surface on Ampk. Thus, our data establish the Ucp1-independent remodeling of adipocyte lipid homeostasis as a key event in tumor-induced WAT wasting, and we propose the ACIP-dependent preservation of Ampk integrity in the WAT as a concept in future therapies for cachexia.

IP-receptor and PPARs trigger the conversion of human white to brite adipocyte induced by carbaprostacyclin.

Brite adipocytes recently discovered in humans are of considerable importance in energy expenditure by converting energy excess into heat. This property could be useful in the treatment of obesity, and nutritional aspects are relevant to this important issue. Using hMADS cells as a human cell model which undergoes a white to a brite adipocyte conversion, we had shown previously that arachidonic acid, the major metabolite of the essential nutrient Ω6-linoleic acid, plays a major role in this process. Its metabolites PGE2 and PGF2 alpha inhibit this process via a calcium-dependent pathway, whereas in contrast carbaprostacyclin (cPGI2), a stable analog of prostacyclin, activates white to brite adipocyte conversion. Herein, we show that cPGI2 generates via its cognate cell-surface receptor IP-R, a cyclic AMP-signaling pathway involving PKA activity which in turn induces the expression of UCP1. In addition, cPGI2 activates the pathway of nuclear receptors of the PPAR family, i.e. PPARα and PPARγ, which act separately from IP-R to up-regulate the expression of key genes involved in the function of brite adipocytes. Thus dual pathways are playing in concert for the occurrence of a browning process of human white adipocytes. These results make prostacyclin analogs as a new class of interesting molecules to treat obesity and associated diseases.

The inward rectifier potassium channel Kir2.1 is required for osteoblastogenesis.

Andersen's syndrome (AS) is a rare and dominantly inherited pathology, linked to the inwardly rectifying potassium channel Kir2.1. AS patients exhibit a triad of symptoms that include periodic paralysis, cardiac dysrhythmia and bone malformations. Some progress has been made in understanding the contribution of the Kir2.1 channel to skeletal and cardiac muscle dysfunctions, but its role in bone morphogenesis remains unclear. We isolated myoblast precursors from muscle biopsies of healthy individuals and typical AS patients with dysmorphic features. Myoblast cultures underwent osteogenic differentiation that led to extracellular matrix mineralization. Osteoblastogenesis was monitored through the activity of alkaline phosphatase, and through the hydroxyapatite formation using Alizarin Red and Von Kossa staining techniques. Patch-clamp recordings revealed the presence of an inwardly rectifying current in healthy cells that was absent in AS osteoblasts, showing the dominant-negative effect of the Kir2.1 mutant allele in osteoblasts. We also found that while control cells actively synthesize hydroxyapatite, AS osteoblasts are unable to efficiently form any extracellular matrix. To further demonstrate the role of the Kir2.1 channels during the osteogenesis, we inhibited Kir2.1 channel activity in healthy patient cells by applying extracellular Ba(2+) or using adenoviruses carrying mutant Kir2.1 channels. In both cases, cells were no longer able to produce extracellular matrixes. Moreover, osteogenic activity of AS osteoblasts was restored by rescue experiments, via wild-type Kir2.1 channel overexpression. These observations provide a proof that normal Kir2.1 channel function is essential during osteoblastogenesis.

MicroRNA-26 family is required for human adipogenesis and drives characteristics of brown adipocytes.

Adipose tissue contains thermogenic adipocytes (i.e., brown and brite/beige) that oxidize nutrients at exceptionally high rates via nonshivering thermogenesis. Its recent discovery in adult humans has opened up new avenues to fight obesity and related disorders such as diabetes. Here, we identified miR-26a and -26b as key regulators of human white and brite adipocyte differentiation. Both microRNAs are upregulated in early adipogenesis, and their inhibition prevented lipid accumulation while their overexpression accelerated it. Intriguingly, miR-26a significantly induced pathways related to energy dissipation, shifted mitochondrial morphology toward that seen in brown adipocytes, and promoted uncoupled respiration by markedly increasing the hallmark protein of brown fat, uncoupling protein 1. By combining in silico target prediction, transcriptomics, and an RNA interference screen, we identified the sheddase ADAM metallopeptidase domain 17 (ADAM17) as a direct target of miR-26 that mediated the observed effects on white and brite adipogenesis. These results point to a novel, critical role for the miR-26 family and its downstream effector ADAM17 in human adipocyte differentiation by promoting characteristics of energy-dissipating thermogenic adipocytes.

Co-expressed genes prepositioned in spatial neighborhoods stochastically associate with SC35 speckles and RNA polymerase II factories.

Chromosomally separated, co-expressed genes can be in spatial proximity, but there is still debate about how this nuclear organization is achieved. Proposed mechanisms include global genome organization, preferential positioning of chromosome territories, or gene-gene sharing of various nuclear bodies. To investigate this question, we selected a set of genes that were co-expressed upon differentiation of human multipotent stem cells. We applied a novel multi-dimensional analysis procedure which revealed that prior to gene expression, the relative position of these genes was conserved in nuclei. Upon stem cell differentiation and concomitant gene expression, we found that co-expressed genes were closer together. In addition, we found that genes in the same 1-µm-diameter neighborhood associated with either the same splicing speckle or to a lesser extent with the same transcription factory. Dispersal of speckles by overexpression of the serine-arginine (SR) protein kinase cdc2-like kinase Clk2 led to a significant drop in the number of genes in shared neighborhoods. We demonstrate quantitatively that the frequencies of speckle and factory sharing can be explained by assuming stochastic selection of a nuclear body within a restricted sub-volume defined by the original global gene positioning present prior to gene expression. We conclude that the spatial organization of these genes is a two-step process in which transcription-induced association with nuclear bodies enhances and refines a pre-existing global organization.

Chondrogenic potential of stem cells derived from adipose tissue: a powerful pharmacological tool.

Chondrogenesis has been widely investigated in vitro using bone marrow-derived mesenchymal stromal cells (BM-MSCs) or primary chondrocytes. However, their use raises some issues partially circumvented by the availability of Adipose tissue-derived MSCs. Herein; we characterized the chondrogenic potential of human Multipotent Adipose-Derived Stem (hMADS) cells, and their potential use as pharmacological tool. hMADS cells are able to synthesize matrix proteins including COMP, Aggrecan and type II Collagen. Furthermore, hMADS cells express BMP receptors in a similar manner to BM-MSC, and BMP6 treatment of differentiated cells prevents expression of the hypertrophic marker type X Collagen. We tested whether IL-1ß and nicotine could impact chondrocyte differentiation. As expected, IL-1ß induced ADAMTS-4 gene expression and modulated negatively chondrogenesis while these effects were reverted in the presence of the IL-1 receptor antagonist. Nicotine, at concentrations similar to those observed in blood of smokers, exhibited a dose dependent increase of Aggrecan expression, suggesting an unexpected protective effect of the drug under these conditions. Therefore, hMADS cells represent a valuable tool for the analysis of in vitro chondrocyte differentiation and to screen for potentially interesting pharmacological drugs.

Activation of protein kinase A and exchange protein directly activated by cAMP promotes adipocyte differentiation of human mesenchymal stem cells.

Human mesenchymal stem cells are primary multipotent cells capable of differentiating into several cell types including adipocytes when cultured under defined in vitro conditions. In the present study we investigated the role of cAMP signaling and its downstream effectors, protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac) in adipocyte conversion of human mesenchymal stem cells derived from adipose tissue (hMADS). We show that cAMP signaling involving the simultaneous activation of both PKA- and Epac-dependent signaling is critical for this process even in the presence of the strong adipogenic inducers insulin, dexamethasone, and rosiglitazone, thereby clearly distinguishing the hMADS cells from murine preadipocytes cell lines, where rosiglitazone together with dexamethasone and insulin strongly promotes adipocyte differentiation. We further show that prostaglandin I(2) (PGI(2)) may fully substitute for the cAMP-elevating agent isobutylmethylxanthine (IBMX). Moreover, selective activation of Epac-dependent signaling promoted adipocyte differentiation when the Rho-associated kinase (ROCK) was inhibited. Unlike the case for murine preadipocytes cell lines, long-chain fatty acids, like arachidonic acid, did not promote adipocyte differentiation of hMADS cells in the absence of a PPARγ agonist. However, prolonged treatment with the synthetic PPARδ agonist L165041 promoted adipocyte differentiation of hMADS cells in the presence of IBMX. Taken together our results emphasize the need for cAMP signaling in concert with treatment with a PPARγ or PPARδ agonist to secure efficient adipocyte differentiation of human hMADS mesenchymal stem cells.

Oxytocin and bone remodelling: relationships with neuropituitary hormones, bone status and body composition.

PURPOSE: There is growing evidence that oxytocin, which regulates appetite, plays a role in bone remodelling and improves osteoporosis. We previously showed a significant decrease in circulating oxytocin levels in postmenopausal osteoporotic women compared to healthy controls. However, factors involved in the pathophysiology of osteoporosis, such as estrogens and leptin, are known to regulate oxytocin secretion. Herein, we evaluated the relationships between oxytocin and other hormonal factors known to regulate bone remodeling and body composition in postmenopausal osteoporotic women, compared to healthy controls. METHODS: In 20 postmenopausal women with severe osteoporosis compared to 16 healthy controls, we measured serum levels of oxytocin, high sensitive estradiol, testosterone, FSH, LH, SHBG, TSH, osteocalcin, serum type I collagen carboxy-terminal telopeptide, leptin. Bone mineral density and body composition were also measured with DXA. RESULTS: Osteoporotic women had significantly lower oxytocin, leptin and LH serum levels and higher CTX and SHBG; all other biological parameters were similar in both groups. Fat mass and lean mass were significantly decreased in osteoporotic women. Oxytocin serum levels were significantly correlated to bone mineral density but not to any other measured parameter, including leptin, estradiol and age. In a logistic regression analysis, osteoporosis remained significantly correlated to oxytocin, regardless of age. CONCLUSIONS: Low oxytocin serum levels appeared to be associated with severe osteoporosis, independently of other factors associated with osteoporosis or known to regulate oxytocin serum levels, such as estradiol or leptin, reinforcing the concept that oxytocin may be involved in the pathophysiology of postmenopausal osteoporosis.

microRNA miR-27b impairs human adipocyte differentiation and targets PPARgamma.

Obesity has emerged as a global health problem with more than 1.1 billion adults to be classified as overweight or obese, and is associated with type 2 diabetes, cardiovascular disease, and several cancers. Since obesity is characterized by an increased size and/or number of adipocytes, elucidating the molecular events governing adipogenesis is of utmost importance. Recent findings indicate that microRNAs (miRNAs) - small non-protein-coding RNAs that function as post-transcriptional gene regulators - are involved in the regulatory network of adipogenesis. Whereas only a single human miRNA is known so far to be functional in adipogenesis as pro-adipogenic, several mouse miRNAs have been identified very recently as adipogenic regulators, thereby stimulating demand for studying the functional role of miRNAs during adipogenesis in human. Here, we demonstrate that miR-27b abundance decreased during adipogenesis of human multipotent adipose-derived stem (hMADS) cells. Overexpression of miR-27b blunted induction of PPARgamma and C/EBPalpha, two key regulators of adipogenesis, during early onset of adipogenesis and repressed adipogenic marker gene expression and triglyceride accumulation at late stages. PPARgamma has a predicted and highly conserved binding site in its 3'UTR and was indeed confirmed to be a direct target of miR-27b. Thus, these results suggest that the anti-adipogenic effect of miR-27b in hMADS cells is due, at least in part, to suppression of PPARgamma.

Stathmin-like 2, a developmentally-associated neuronal marker, is expressed and modulated during osteogenesis of human mesenchymal stem cells.

Stathmin-like 2 (STMN2) protein, a neuronal protein of the stathmin family, has been implicated in the microtubule regulatory network as a crucial element of cytoskeletal regulation. Herein, we describe that STMN2 expression increases at both mRNA and protein levels during osteogenesis of human mesenchymal stem cells derived from adipose tissue (hMADS cells) and bone marrow (hBMS cells), whereas it decreases to undetectable levels during adipogenesis. STMN2 protein is localized in both Golgi and cytosolic compartments. Its expression appears modulated in osteoblasts by nerve growth factor, dexamethasone or RhoA kinase inhibitor Y-27632 which are known effectors of osteogenesis. Thus STMN2 appears a novel marker of osteogenesis and osteoblast per se, that could play a role in the regulation of the adipocyte/osteoblast balance.

Oxytocin controls differentiation of human mesenchymal stem cells and reverses osteoporosis.

Osteoporosis constitutes a major worldwide public health burden characterized by enhanced skeletal fragility. Bone metabolism is the combination of bone resorption by osteoclasts and bone formation by osteoblasts. Whereas increase in bone resorption is considered as the main contributor of bone loss that may lead to osteoporosis, this loss is accompanied by increased bone marrow adiposity. Osteoblasts and adipocytes share the same precursor cell and an inverse relationship exists between the two lineages. Therefore, identifying signaling pathways that stimulate mesenchymal stem cells osteogenesis at the expense of adipogenesis is of major importance for developing new therapeutic treatments. For this purpose, we identified by transcriptomic analysis the oxytocin receptor pathway as a potential regulator of the osteoblast/adipocyte balance of human multipotent adipose-derived stem (hMADS) cells. Both oxytocin (OT) and carbetocin (a stable OT analogue) negatively modulate adipogenesis while promoting osteogenesis in both hMADS cells and human bone marrow mesenchymal stromal cells. Consistent with these observations, ovariectomized (OVX) mice and rats, which become osteoporotic and exhibit disequilibrium of this balance, have significant decreased OT levels compared to sham-operated controls. Subcutaneous OT injection reverses bone loss in OVX mice and reduces marrow adiposity. Clinically, plasma OT levels are significantly lower in postmenopausal women developing osteoporosis than in their healthy counterparts. Taken together, these results suggest that plasma OT levels represent a novel diagnostic marker for osteoporosis and that OT administration holds promise as a potential therapy for this disease.

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

BACKGROUND: 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. RESULTS: 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. CONCLUSION: 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.

Human adipose tissue-derived multipotent stem cells differentiate in vitro and in vivo into osteocyte-like cells.

Cell-based therapies are used to treat bone defects. We recently described that human multipotent adipose-derived stem (hMADS) cells, which exhibit a normal karyotype, self renewal, and the maintenance of their differentiation properties, are able to differentiate into different lineages. Herein, we show that hMADS cells can differentiate into osteocyte-like cells. In the presence of a low amount of serum and EGF, hMADS cells express specific molecular markers, among which alkaline phosphatase, CBFA-1, osteocalcin, DMP1, PHEX, and podoplanin and develop functional gap-junctions. When loaded on a hardening injectable bone substitute (HIBS) biomaterial and injected subcutaneously into nude mice, hMADS cells develop mineralized woven bone 4 weeks after implantation. Thus hMADS cells represent a valuable tool for pharmacological and biological studies of osteoblast differentiation in vitro and bone development in vivo.