Liposuction Preserves the Morphological Integrity of the Microvascular Network: Flow Cytometry and Confocal Microscopy Evidence in a Controlled Study.

BACKGROUND: Liposuction is a very popular technique in plastic surgery that allows for the taking adipose tissue (AT) on large surfaces with little risk of morbidity. Although liposuction was previously shown to preserve large perforator vessels, little is known about the effects of liposuction on the microvasculature network. OBJECTIVES: The aim of this study was to analyze the effect of liposuction on the preservation of microvessels at tissue and cellular levels by flow cytometry and confocal microscopy following abdominoplasty procedure. METHODS: Percentage of endothelial cells in AT from liposuction and en bloc AT was determined by multicolor flow cytometry. Moreover, vessel density and adipocyte content were analyzed in situ in 3 different types of AT (en bloc, from liposuction, and residual AT after liposuction) by confocal microscopy. RESULTS: Flow cytometric analysis showed that en bloc AT contained 30.6% ± 12.9% and AT from liposuction 21.6% ± 9.9% of endothelial cells (CD31(pos)/CD45(neg)/CD235a(neg)/CD11b(neg)) (P = .009). Moreover, analysis of paired AT from the same patients (n = 5) confirmed a lower percentage of endothelial cells in AT from liposuction compared to en bloc AT (17.7% ± 4.5% vs 21.9% ± 3.3%, P = .031). Likewise, confocal microscopy showed that en bloc AT contained 8.2% ± 6.3%, AT from liposuction only 1.6% ± 1.0% (P < .0001), and AT after liposuction 8.9% ± 4.1% (P = .111) of CD31(pos) vessels. Conversely, adipocyte content was 39.5% ± 14.5% in the en bloc AT, 45% ± 18.4% in AT from liposuction (P = .390), and 18.8 ± 14.8% in AT after liposuction (P = .011). CONCLUSIONS: For the first time, we demonstrate that liposuction preserves the microvascular network. Indeed, a low percentage of endothelial cells was found in AT from liposuction and we confirm the persistence of microvessels in the tissue after liposuction.

Regionalization of browning revealed by whole subcutaneous adipose tissue imaging.

OBJECTIVE: White and brown adipose tissues play a major role in the regulation of metabolic functions. With the explosion of obesity and metabolic disorders, the interest in adipocyte biology is growing constantly. While several studies have demonstrated functional differences between adipose fat pads, especially in their involvement in metabolic diseases, there are no data available on possible heterogeneity within an adipose depot. METHODS: This study investigated the three-dimensional (3-D) organization of the inguinal fat pad in adult mice by combining adipose tissue clearing and autofluorescence signal acquisition by confocal microscopy. In addition, the study analyzed the expression of genes involved in adipocyte biology and browning at the mARN and protein levels in distinct areas of the inguinal adipose tissue, in control conditions and after cold exposure. RESULTS: Semiautomated 3-D image analysis revealed an organization of the fat depot showing two regions: the core was structured into segmented lobules, whereas the periphery appeared unsegmented. Perilipin immunostaining showed that most of the adipocytes located in the core region had smaller lipid droplets, suggesting a brown-like phenotype. qPCR analysis showed a higher expression of the browning markers Ucp1, Prdm16, Ppargc1a, and Cidea in the core region than at the periphery. Finally, cold exposure induced upregulation of thermogenic gene expression associated with an increase of UCP1 protein, specifically in the core region of the inguinal fat depot. CONCLUSIONS: Altogether, these data demonstrate a structural and functional heterogeneity of the inguinal fat pad, with an anatomically restricted browning process in the core area.

Mouse adipose tissue stromal cells give rise to skeletal and cardiomyogenic cell sub-populations.

We previously reported that adipose tissue could generate cardiomyocyte-like cells from crude stromal vascular fraction (SVF) in vitro that improved cardiac function in a myocardial infarction context. However, it is not clear whether these adipose-derived cardiomyogenic cells (AD-CMG) constitute a homogenous population and if AD-CMG progenitors could be isolated as a pure population from the SVF of adipose tissue. This study aims to characterize the different cell types that constitute myogenic clusters and identify the earliest AD-CMG progenitors in vitro for establishing a complete phenotype and use it to sort AD-CMG progenitors from crude SVF. Here, we report cell heterogeneity among adipose-derived clusters during their course of maturation and highlighted sub-populations that exhibit original mixed cardiac/skeletal muscle phenotypes with a progressive loss of cardiac phenotype with time in liquid culture conditions. Moreover, we completed the phenotype of AD-CMG progenitors but we failed to sort them from the SVF. We demonstrated that micro-environment is required for the maturation of myogenic phenotype by co-culture experiments. These findings bring complementary data on AD-CMG and suggest that their emergence results from in vitro events.

Browning of white adipose cells by intermediate metabolites: an adaptive mechanism to alleviate redox pressure.

The presence of brown adipose tissue (BAT) in human adults opens attractive perspectives to treat metabolic disorders. Indeed, BAT dissipates energy as heat via uncoupling protein (UCP)1. Brown adipocytes are located in specific deposits or can emerge among white fat through the so-called browning process. Although numerous inducers have been shown to drive this process, no study has investigated whether it could be controlled by specific metabolites. Here, we show that lactate, an important metabolic intermediate, induces browning of murine white adipose cells with expression of functional UCP1. Lactate-induced browning also occurs in human cells and in vivo. Lactate controls Ucp1 expression independently of hypoxia-inducible factor-1α and PPARα pathways but requires active PPARγ signaling. We demonstrate that the lactate effect on Ucp1 is mediated by intracellular redox modifications as a result of lactate transport through monocarboxylate transporters. Further, the ketone body ß-hydroxybutyrate, another metabolite that impacts redox state, is also a strong browning inducer. Because this redox-dependent increase in Ucp1 expression promotes an oxidative phenotype with mitochondria, browning appears as an adaptive mechanism to alleviate redox pressure. Our findings open new perspectives for the control of adipose tissue browning and its physiological relevance.

Assessing the role of cell-surface molecules in central synaptogenesis in the Drosophila visual system.

A hallmark of the central nervous system is its spatial and functional organization in synaptic layers. During neuronal development, axons form transient contacts with potential post-synaptic elements and establish synapses with appropriate partners at specific layers. These processes are regulated by synaptic cell-adhesion molecules. In the Drosophila visual system, R7 and R8 photoreceptor subtypes target distinct layers and form en passant pre-synaptic terminals at stereotypic loci of the axonal shaft. A leucine-rich repeat transmembrane protein, Capricious (Caps), is known to be selectively expressed in R8 axons and their recipient layer, which led to the attractive hypothesis that Caps mediates R8 synaptic specificity by homophilic adhesion. Contradicting this assumption, our results indicate that Caps does not have a prominent role in synaptic-layer targeting and synapse formation in Drosophila photoreceptors, and that the specific recognition of the R8 target layer does not involve Caps homophilic axon-target interactions. We generated flies that express a tagged synaptic marker to evaluate the presence and localization of synapses in R7 and R8 photoreceptors. These genetic tools were used to assess how the synaptic profile is affected when axons are forced to target abnormal layers by expressing axon guidance molecules. When R7 axons were mistargeted to the R8-recipient layer, R7s either maintained an R7-like synaptic profile or acquired a similar profile to r8s depending on the overexpressed protein. When R7 axons were redirected to a more superficial medulla layer, the number of presynaptic terminals was reduced. These results indicate that cell-surface molecules are able to dictate synapse loci by changing the axon terminal identity in a partially cell-autonomous manner, but that presynapse formation at specific sites also requires complex interactions between pre- and post-synaptic elements.

Seven-pass transmembrane cadherins: roles and emerging mechanisms in axonal and dendritic patterning.

The Flamingo/Celsr seven-transmembrane cadherins represent a conserved subgroup of the cadherin superfamily involved in multiple aspects of development. In the developing nervous system, Fmi/Celsr control axonal blueprint and dendritic morphogenesis from invertebrates to mammals. As expected from their molecular structure, seven-transmembrane cadherins can induce cell-cell homophilic interactions but also intracellular signaling. Fmi/Celsr is known to regulate planar cell polarity (PCP) through interactions with PCP proteins. In the nervous system, Fmi/Celsr can function in collaboration with or independently of other PCP genes. Here, we focus on recent studies which show that seven-transmembrane cadherins use distinct molecular mechanisms to achieve diverse functions in the development of the nervous system.

Golden Goal collaborates with Flamingo in conferring synaptic-layer specificity in the visual system.

Neuronal connections are often organized in layers that contain synapses between neurons that have similar functions. In Drosophila, R7 and R8 photoreceptors, which detect different wavelengths, form synapses in distinct medulla layers. The mechanisms underlying the specificity of synaptic-layer selection remain unclear. We found that Golden Goal (Gogo) and Flamingo (Fmi), two cell-surface proteins involved in photoreceptor targeting, functionally interact in R8 photoreceptor axons. Our results indicate that Gogo promotes R8 photoreceptor axon adhesion to the temporary layer M1, whereas Gogo and Fmi collaborate to mediate axon targeting to the final layer M3. Structure-function analysis suggested that Gogo and Fmi interact with intracellular components through the Gogo cytoplasmic domain. Moreover, Fmi was also required in target cells for R8 photoreceptor axon targeting. We propose that Gogo acts as a functional partner of Fmi for R8 photoreceptor axon targeting and that the dynamic regulation of their interaction specifies synaptic-layer selection of photoreceptors.