The perivascular phenotype and behaviors of dedifferentiated cells derived from human mature adipocytes

Plasminogen activator inhibitor type-1 is a negative regulator of hematopoietic regeneration in the adipocyte-rich bone marrow microenvironment

Bone marrow adipocytes (BMAs) have recently been recognized as a niche component with a suppressive function. Obese individuals with abundant BMAs exhibit impaired hematopoietic regeneration after hematopoietic stem cell transplantation (HSCT). We hypothesized that plasminogen activator inhibitor type-1 (PAI-1), an adipokine that regulates the fibrinolytic system, contributes to impaired hematopoiesis in bone marrow (BM) microenvironment with abundant BMAs. We demonstrated that BMAs differentiated in vitro could secrete PAI-1 and were positive for PAI-1 in vivo. In addition, the abundance of BMAs was associated with high levels of PAI-1 expression. The BMA-rich microenvironment exhibited impaired hematopoietic regeneration after HSCT when compared with a BMA-less microenvironment. The impaired hematopoietic regeneration in BMA-rich microenvironment was significantly alleviated by PAI-1 knockout or PAI-1 inhibitor treatment. Obese mice with abundant BMAs, compared with normal-weight mice, exhibited higher bone marrow PAI-1 concentrations, increased fibrinolytic system suppression, and lower stem cell factor (SCF) concentrations after HSCT. PAI-1 inhibitor administration significantly activated the fibrinolytic system in obese mice, contributing to the higher SCF concentration. Moreover, PAI-1 inhibitor treatment significantly alleviated the impaired hematopoietic regeneration in obese mice both after 5-fluorouracil injection and HSCT. These results indicate that PAI-1 hinders hematopoietic regeneration in BMA-rich microenvironments. The blockade of PAI-1 activity could be a novel therapeutic means of facilitating hematopoietic reconstitution in BMA-rich patients.

Current challenges in dedifferentiated fat cells research

Dedifferentiated fat cells show great promises as a novel cell source for stem cell research. It has many advantages when used for cell-based therapeutics including abundance, pluripotency, and safety. However, there are many obstacles researchers need to overcome to make the next big move in DFAT cells research. In this review, we summarize the current main challenges in DFAT cells research including cell culture purity, phenotypic properties, and dedifferentiation mechanisms. The common methods to produce DFAT cells as well as the cell purity issue during DFAT cell production have been introduced. Current approaches to improve DFAT cell purity have been discussed. The phenotypic profile of DFAT cells have been listed and compared with other stem cells. Further studies on elucidating the underlying dedifferentiation mechanisms will dramatically advance DFAT cell research.

Subsets of Visceral Adipose Tissue Nuclei with Distinct Levels of 5-Hydroxymethylcytosine

The reprogramming of cellular memory in specific cell types, and in visceral adipocytes in particular, appears to be a fundamental aspect of obesity and its related negative health outcomes. We explored the hypothesis that adipose tissue contains epigenetically distinct subpopulations of adipocytes that are differentially potentiated to record cellular memories of their environment. Adipocytes are large, fragile, and technically difficult to efficiently isolate and fractionate. We developed fluorescence nuclear cytometry (FNC) and fluorescence activated nuclear sorting (FANS) of cellular nuclei from visceral adipose tissue (VAT) using the levels of the pan-adipocyte protein, peroxisome proliferator-activated receptor gamma-2 (PPARg2), to distinguish classes of PPARg2-Positive (PPARg2-Pos) adipocyte nuclei from PPARg2-Negative (PPARg2-Neg) leukocyte and endothelial cell nuclei. PPARg2-Pos nuclei were 10-fold enriched for most adipocyte marker transcripts relative to PPARg2-Neg nuclei. PPARg2-Pos nuclei showed 2- to 50-fold higher levels of transcripts encoding most of the chromatin-remodeling factors assayed, which regulate the methylation of histones and DNA cytosine (e.g., DNMT1, TET1, TET2, KDM4A, KMT2C, SETDB1, PAXIP1, ARID1A, JMJD6, CARM1, and PRMT5). PPARg2-Pos nuclei were large with decondensed chromatin. TAB-seq demonstrated 5-hydroxymethylcytosine (5hmC) levels were remarkably dynamic in gene bodies of various classes of VAT nuclei, dropping 3.8-fold from the highest quintile of expressed genes to the lowest. In short, VAT-derived adipocytes appear to be more actively remodeling their chromatin than non-adipocytes.