Aldehyde Dehydrogenase Activity in Adipose Tissue: Isolation and Gene Expression Profile of Distinct Sub-population of Mesenchymal Stromal Cells

Thanks to their relative abundance and easier collection, adipose tissue (AT) is considered an alternative source for the isolation of mesenchymal stromal cells (MSCs). MSCs have great therapeutic values and are thus under investigations for several clinical indications such as regenerative medicine and immunomodulation. In this work, we aimed to identify, isolate and characterize AT-MSCs based on their aldehyde dehydrogenase (ALDH) activity known to be a classical feature of stem cells. FACS technology allowed to isolate two different populations of AT-MSCs according to their ALDH activity (referred as ALDH⁺ and ALDH^-). Depending on their ALDH activity, the transcriptome analysis of both cell populations demonstrated a differential pattern of genes related to the main properties of MSCs (proliferation, response to hypoxia, angiogenesis, phenotype, stemness, multilineage, hematopoiesis, immunomodulation). Based on these profiling, both AT-MSC populations could differ in terms of biological responses and functionalities. Collectively, the use of ALDH for isolating and identifying sub-populations of MSCs with specific gene profile may represent an alternative method to provide solutions for targeted therapeutic applications.

Global profiling of the gene expression and alternative splicing events during hypoxia-regulated chondrogenic differentiation in human cartilage endplate-derived stem cells

The intervertebral disc (IVD) degeneration is initiated by cartilage endplate (CEP) degeneration and is characterised by reduced chondrification. Cartilage endplate-derived stem cells (CESCs) with chondrogenic differentiation abilities are responsible for the restoration of cartilage. CEP remains in an avascular and hypoxic microenvironment. In this study, we observed that the physiological hypoxia greatly promotes the chondrogenic differentiation of CESCs. This tissue specificity of the differentiation fate of CESCs in response to the hypoxic microenvironment was physiologically significant for the CEP to maintain the chondrification status. To investigate the mechanisms underlying the hypoxia-regulated chondrogenic differentiation of CESCs, we adopted a high-throughput scanning technology to detect the global profiling of gene expression and alternative splicing (AS) event changes during chondrogenic differentiation under hypoxia in CESCs compared to those induced under normoxia. An Affymetrix Human Transcriptome Array 2.0 was used to identify the differentially expressed genes (DEGs) and alternatively spliced genes (ASGs). After RT-PCR validation, GO and KEGG pathway analyses of both the DEGs and ASGs were performed. The enrichment of the GO functional terms and signalling pathways provided referential direction of the mechanism to study the gene expression and AS in the hypoxia-regulated chondrogenesis promotion, which could be helpful in understanding this physiological phenomenon, and it could also be instrumental in finding targets for CEP degeneration therapy.

Signaling Interplay between Bone Marrow Adipose Tissue and Multiple Myeloma cells

In the year 2000, Hanahan and Weinberg (1) defined the six Hallmarks of Cancer as: self-sufficiency in growth signals, evasion of apoptosis, insensitivity to antigrowth mechanisms, tissue invasion and metastasis, limitless replicative potential, and sustained angiogenesis. Eleven years later, two new Hallmarks were added to the list (avoiding immune destruction and reprograming energy metabolism) and two new tumor characteristics (tumor-promoting inflammation and genome instability and mutation) (2). In multiple myeloma (MM), a destructive cancer of the plasma cell that grows predominantly in the bone marrow (BM), it is clear that all these hallmarks and characteristics are in play, contributing to tumor initiation, drug resistance, disease progression, and relapse. Bone marrow adipose tissue (BMAT) is a newly recognized contributor to MM oncogenesis and disease progression, potentially affecting MM cell metabolism, immune action, inflammation, and influences on angiogenesis. In this review, we discuss the confirmed and hypothetical contributions of BMAT to MM development and disease progression. BMAT has been understudied due to technical challenges and a previous lack of appreciation for the endocrine function of this tissue. In this review, we define the dynamic, responsive, metabolically active BM adipocyte. We then describe how BMAT influences MM in terms of: lipids/metabolism, hypoxia/angiogenesis, paracrine or endocrine signaling, and bone disease. We then discuss the connection between BMAT and systemic inflammation and potential treatments to inhibit the feedback loops between BM adipocytes and MM cells that support MM progression. We aim for researchers to use this review to guide and help prioritize their experiments to develop better treatments or a cure for cancers, such as MM, that associate with and may depend on BMAT.