Characterization and comparison of adipose tissue‐derived cells from human subcutaneous and omental adipose tissues

Different fat depots contribute differently to disease and function. These differences may be due to the regional variation in cell types and inherent properties of fat cell progenitors. To address the differences of cell types in the adipose tissue from different depots, the phenotypes of freshly isolated adipose tissue‐derived cells (ATDCs) from subcutaneous (SC) and omental (OM) adipose tissues were compared using flow cytometry. Our results showed that CD31^?CD34⁺CD45^?CD90^‐CD105^?CD146⁺ population, containing vascular smooth muscle cells and pericytes, was specifically defined in the SC adipose tissue while no such population was observed in OM adipose tissue. On the other hand, CD31^?CD34⁺CD45^?CD90^?CD105^?CD146^? population, which is an undefined cell population, were found solely in OM adipose tissue. Overall, the SC adipose tissue contained more ATDCs than OM adipose tissue, while OM adipose tissue contained more blood‐derived cells. Regarding to the inherent properties of fat cell progenitors from the two depots, adipose‐derived stem cells (ADSCs) from SC had higher capacity to differentiate into both adipogenic and osteogenic lineages than those from OM, regardless of that the proliferation rates of ADSCs from both depots were similar. The higher differentiation capacity of ADSCs from SC adipose tissue suggests that SC tissue is more suitable cell source for regenerative medicine than OM adipose tissue. Copyright © 2009 John Wiley & Sons, Ltd.     

VEGF receptor Flk-1 plays an important role in c-kit expression in adipose tissue derived stem cells

It is known that c-kit(+) cells are increased in heart after infarction. The exact origins of the cardiac c-kit(+) cells remain to be determined. We asked whether adipose tissue could be a potential source of c-kit(+) cells. Our data show that the number of c-kit(+) cells increased in adipose tissue derived stem cells when cultured with conditioned medium from neonatal cardiomyocytes grown under serum deprivation and hypoxia condition. We also found that VEGF receptor Flk-1 is involved in c-kit up regulation via ERK-mediated pathway.     

Dynamic survey of mitochondria by ubiquitin

Ubiquitin is a post‐translational modifier with proteolytic and non‐proteolytic roles in many biological processes. At mitochondria, it performs regulatory homeostatic functions and contributes to mitochondrial quality control. Ubiquitin is essential for mitochondrial fusion, regulates mitochondria‐ER contacts, and participates in maternal mtDNA inheritance. Under stress, mitochondrial dysfunction induces ubiquitin‐dependent responses that involve mitochondrial proteome remodeling and culminate in organelle removal by mitophagy. In addition, many ubiquitin‐dependent mechanisms have been shown to regulate innate immune responses and xenophagy. Here, we review the emerging roles of ubiquitin at mitochondria.     

BNIP3L/NIX-dependent mitophagy regulates cell differentiation via metabolic reprogramming

Macroautophagy/autophagy is the process by which cellular components are degraded and recycled within the lysosome. These components include mitochondria, the selective degradation of which is known as mitophagy. Mitochondria are dynamic organelles that constantly adapt their morphology, function, and number to accommodate the metabolic needs of the cell. Extensive metabolic reconfiguration occurs during cell differentiation, when mitochondrial activity increases in most cell types. However, our data demonstrate that during physiologic retinal ganglion cell (RGC) development, mitophagy-dependent metabolic reprogramming toward glycolysis regulates numbers of RGCs, which are the first neurons to differentiate in the retina and whose axons form the optic nerve. We show that during retinal development tissue hypoxia triggers HIF1A/HIF-1 stabilization, resulting in increased expression of the mitophagy receptor BNIP3L/NIX. BNIP3L-dependent mitophagy results in a metabolic shift toward glycolysis essential for RGC neurogenesis. Moreover, we demonstrate that BNIP3L-dependent mitophagy also regulates the polarization of proinflammatory/M1 macrophages, which undergo glycolysis-dependent differentiation during the inflammatory response. Our results uncover a new link between hypoxia, mitophagy, and metabolic reprogramming in the differentiation of several cell types in vivo. These findings may have important implications for neurodegenerative, metabolic and other diseases in which mitochondrial dysfunction and metabolic alterations play a prominent role.     

Clinical grade adult stem cell banking

There has been a great deal of scientific interest recently generated by the potential therapeutic applications of adult stem cells in human care but there are several challenges regarding quality and safety in clinical applications and a number of these challenges relate to the processing and banking of these cells ex-vivo. As the number of clinical trials and the variety of adult cells used in regenerative therapy increases, safety remains a primary concern. This has inspired many nations to formulate guidelines and standards for the quality of stem cell collection, processing, testing, banking, packaging and distribution. Clinically applicable cryopreservation and banking of adult stem cells offers unique opportunities to advance the potential uses and widespread implementation of these cells in clinical applications. Most current cryopreservation protocols include animal serum proteins and potentially toxic cryoprotectant additives (CPAs) that prevent direct use of these cells in human therapeutic applications. Long term cryopreservation of adult stem cells under good manufacturing conditions using animal product free solutions is critical to the widespread clinical implementation of ex-vivo adult stem cell therapies. Furthermore, to avoid any potential cryoprotectant related complications, reduced CPA concentrations and efficient post-thaw washing to remove CPA are also desirable. The present review focuses on the current strategies and important aspects of adult stem cell banking for clinical applications. These include current good manufacturing practices (cGMPs), animal protein free freezing solutions, cryoprotectants, freezing & thawing protocols, viability assays, packaging and distribution. The importance and benefits of banking clinical grade adult stem cells are also discussed.     

谷氨酸对大鼠脂肪干细胞诱导分化神经细胞的影响及机制

目的:研究谷氨酸(Glu)对大鼠脂肪干细胞Adipose-derived stem cells(ADCSs)诱导分化神经细胞的作用及机制。方法:取成年大鼠腹股沟脂肪组织进行体外细胞培养,采用免疫组化方法检测证实为ADSCs。对照组为正常培养的ADSCs并诱导分化神经细胞,谷氨酸(Glu)处理组加入不同浓度的Glu,MTT比色法观察脂肪干细胞的存活率。结果:从ADSCs诱导分化的细胞包括神经元及神经胶质细胞,免疫组化结果显示神经元特异性烯醇化酶(NSE)染色阳性和胶质纤维酸性蛋白(GFAP)染色阳性。Glu处理组给药24h后,与对照组比较ADSCs存活率明显降低,50μmol·L-1Glu组细胞存活率为83.98%,与对照组比较差异无显著性(P>0.05);100及1000μmol·L-1Glu组干细胞存活率(分别为66.82%和17.08%)低于对照组(P<0.05,P<0.01)。结论:Glu对ADSCs有损伤作用,随着Glu剂量的增加,ADSCs的存活率逐渐降低,二者呈剂量依赖关系。     

Mitophagy in hematopoietic stem cells

Hematopoietic stem cells (HSCs) are inherently quiescent and self-renewing, yet can differentiate and commit to multiple blood cell types. Intracellular mitochondrial content is dynamic, and there is an increase in mitochondrial content during differentiation and lineage commitment in HSCs. HSCs reside in a hypoxic niche within the bone marrow and rely heavily on glycolysis, while differentiated and committed progenitors rely on oxidative phosphorylation. Increased oxidative phosphorylation during differentiation and commitment is not only due to increased mitochondrial content but also due to changes in mitochondrial cytosolic distribution and efficiency. These changes in the intracellular mitochondrial landscape contribute signals toward regulating differentiation and commitment. Thus, a functional relationship exists between the mitochondria in HSCs and the state of the HSCs (i.e., stemness vs. differentiated). This review focuses on how autophagy-mediated mitochondrial clearance (i.e., mitophagy) may affect HSC mitochondrial content, thereby influencing the fate of HSCs and maintenance of hematopoietic homeostasis.     

Protein N-terminal Acetylation by the NatA Complex Is Critical for Selective Mitochondrial Degradation

Mitophagy is an evolutionarily conserved autophagy pathway that selectively degrades mitochondria. Although it is well established that this degradation system contributes to mitochondrial quality and quantity control, mechanisms underlying mitophagy remain largely unknown. Here, we report that protein N-terminal acetyltransferase A (NatA), an enzymatic complex composed of the catalytic subunit Ard1 and the adaptor subunit Nat1, is crucial for mitophagy in yeast. NatA is associated with the ribosome via Nat1 and acetylates the second amino acid residues of nascent polypeptides. Mitophagy, but not bulk autophagy, is strongly suppressed in cells lacking Ard1, Nat1, or both proteins. In addition, loss of NatA enzymatic activity causes impairment of mitochondrial degradation, suggesting that protein N-terminal acetylation by NatA is important for mitophagy. Ard1 and Nat1 mutants exhibited defects in induction of Atg32, a protein essential for mitophagy, and formation of mitochondria-specific autophagosomes. Notably, overexpression of Atg32 partially recovered mitophagy in NatA-null cells, implying that this acetyltransferase participates in mitophagy at least in part via Atg32 induction. Together, our data implicate NatA-mediated protein modification as an early regulatory step crucial for efficient mitophagy.