Semi-Automated Isolation of the Stromal Vascular Fraction from Murine White Adipose Tissue Using a Tissue Dissociator

The in vitro study of white, brown, and beige adipocyte differentiation enables the investigation of cell-autonomous functions of adipocytes and their ...

the university of tokyo

The differential diagnosis of acute abdomen is typically extremely broad in range, with vasculitis posing a rare but potentially life-threatening cause of acute abdomen. Here, we report a case of acute abdomen with bowel wall thickening limited to jejunum, accompanied by unexplained renal dysfunction. Later, the patient was diagnosed as having polyarteritis nodosa based on surgically resected jejunal necrosis. Despite aggressive treatment, including the use of steroid pulse therapy and continuous hemodiafiltration, the patient died. Although polyarteritis nodosa is extremely rare in patients with acute abdomen, acute abdomen is relatively common manifestation of that. And it is reported that involvement of small intestine suggests poorer prognosis. Our case highlights the importance of vasculitis as a differential diagnosis of patients with atypical acute abdomen. In this report, we not only review possible clues that might have led to an earlier diagnosis in this case, but also attempt to draw some lessons for treating similar cases in the future.

Polyarteritis nodosa diagnosed by surgically resected jejunal necrosis following acute abdomen.

Brown fat dissipates energy as heat and protects against obesity. Here, we identified nuclear factor I-A (NFIA) as a transcriptional regulator of brown fat by a genome-wide open chromatin analysis of murine brown and white fat followed by motif analysis of brown-fat-specific open chromatin regions. NFIA and the master transcriptional regulator of adipogenesis, PPARγ, co-localize at the brown-fat-specific enhancers. Moreover, the binding of NFIA precedes and facilitates the binding of PPARγ, leading to increased chromatin accessibility and active transcription. Introduction of NFIA into myoblasts results in brown adipocyte differentiation. Conversely, the brown fat of NFIA-knockout mice displays impaired expression of the brown-fat-specific genes and reciprocal elevation of muscle genes. Finally, expression of NFIA and the brown-fat-specific genes is positively correlated in human brown fat. These results indicate that NFIA activates the cell-type-specific enhancers and facilitates the binding of PPARγ to control the brown fat gene program.

NFIA co-localizes with PPARγ and transcriptionally controls the brown fat gene program.

The transcription factor nuclear factor I-A (NFIA) is a regulator of brown adipocyte differentiation. Here we show that the C-terminal 17 amino acid residues of NFIA (which we call pro#3 domain) are required for the transcriptional activity of NFIA. Full-length NFIA-but not deletion mutant lacking pro#3 domain-rescued impaired expression of PPARγ, the master transcriptional regulator of adipogenesis and impaired adipocyte differentiation in NFIA-knockout cells. Mechanistically, the ability of NFIA to penetrate chromatin and bind to the crucial Pparg enhancer is mediated through pro#3 domain. However, the deletion mutant still binds to Myod1 enhancer to repress expression of MyoD, the master transcriptional regulator of myogenesis as well as proximally transcribed non-coding RNA called DRReRNA, via competition with KLF5 in terms of enhancer binding, leading to suppression of myogenic gene program. Therefore, the negative effect of NFIA on the myogenic gene program is, at least partly, independent of the positive effect on PPARγ expression and its downstream adipogenic gene program. These results uncover multiple ways of action of NFIA to ensure optimal regulation of brown and beige adipocyte differentiation.

NFIA differentially controls adipogenic and myogenic gene program through distinct pathways to ensure brown and beige adipocyte differentiation.

Thermogenic brown and beige adipocytes counteract obesity by enhancing energy dissipation via uncoupling protein-1 (Ucp1). However, the effect of genetic variation on these cells, a major source of disease susceptibility, has been less well studied. Here we examined beige adipocytes from obesity-prone C57BL/6J (B6) and obesity-resistant 129X1/SvJ (129) mouse strains and identified a -regulatory variant rs47238345 that is responsible for differential Ucp1 expression. The alternative T allele of rs47238345 at the  -12kb enhancer in 129 facilitates the allele-specific binding of nuclear factor I-A (NFIA) to mediate allele-specific enhancer-promoter interaction and  transcription. Furthermore, CRISPR-Cas9/Cpf1-mediated single nucleotide polymorphism (SNP) editing of rs47238345 resulted in increased Ucp1 expression. We also identified Lim homeobox protein 8 (Lhx8), whose expression is higher in 129 than in B6, as a acting regulator of Ucp1 in mice and humans. These results demonstrate the - and acting effects of genetic variation on Ucp1 expression that underlie phenotypic diversity.

NFIA determines the -effect of genetic variation on Ucp1 expression in murine thermogenic adipocytes.

Although inflammation plays critical roles in the development of atherosclerosis, its regulatory mechanisms remain incompletely understood. Perivascular adipose tissue (PVAT) has been reported to undergo inflammatory changes in response to vascular injury. Here, we show that vascular injury induces the beiging (brown adipose tissue-like phenotype change) of PVAT, which fine-tunes inflammatory response and thus vascular remodeling as a protective mechanism. In a mouse model of endovascular injury, macrophages accumulate in PVAT, causing beiging phenotype change. Inhibition of PVAT beiging by genetically silencing PRDM16, a key regulator to beiging, exacerbates inflammation and vascular remodeling following injury. Conversely, activation of PVAT beiging attenuates inflammation and pathological vascular remodeling. Single-cell RNA sequencing reveals that beige adipocytes abundantly express neuregulin 4 (Nrg4) which critically regulate alternative macrophage activation. Importantly, significant beiging is observed in the diseased aortic PVAT in patients with acute aortic dissection. Taken together, vascular injury induces the beiging of adjacent PVAT with macrophage accumulation, where NRG4 secreted from the beige PVAT facilitates alternative activation of macrophages, leading to the resolution of vascular inflammation. Our study demonstrates the pivotal roles of PVAT in vascular inflammation and remodeling and will open a new avenue for treating atherosclerosis.

Beiging of perivascular adipose tissue regulates its inflammation and vascular remodeling.

Chromatin immunoprecipitation (ChIP) experiments with differentiated adipocytes are challenging because lipid droplets interfere with immunoprecipitation efficiency. Here, the author describes optimized procedures to minimize the burden of lipid droplets by using hypotonic buffer to enrich nuclear fraction before formaldehyde crosslinking, thus increasing the sensitivity and specificity of ChIP experiments with differentiated adipocytes. The author also describes steps after fixation, including sonication, immunoprecipitation, washing, reverse-crosslinking, and purification. This protocol is compatible with ChIP-qPCR and ChIP-seq of various transcription factors and histone modifications. For complete details on the use and execution of this protocol, please refer to Hiraike et al. (2022)..

Yuta Hiraike

Division for Health Service Promotion,
Department of Diabetes and Metabolic Diseases,
Graduate School of Medicine,
The University of Tokyo Excellent Young Researcher Program,
Department of Diabetes and Metabolic Diseases, Graduate School of Medicine

the university of tokyo

Semi-Automated Isolation of the Stromal Vascular Fraction from Murine White Adipose Tissue Using a Tissue Dissociator