Abstract
Microenvironment plays an important role for stem cell proliferation and differentiation. Macromolecular crowding (MMC) was recently shown to assist stem cells in forming their own matrix microenvironment in vitro. The ability of MMC to support adipose stem cell (ASC) proliferation, metabolism, and multilineage differentiation was studied under different conditions: fetal bovine serum- (FBS-) and human serum- (HS-) based media and xeno- and serum-free (XF/SF) media. Furthermore, the immunophenotype of ASCs under MMC was evaluated. The proliferative capacity of ASCs under MMC was attenuated in each condition. However, osteogenic differentiation was enhanced under MMC, shown by increased deposition of mineralized matrix in FBS and HS cultures. Likewise, significantly greater lipid droplet accumulation and increased collagen IV deposition indicated enhanced adipogenesis under MMC in FBS and HS cultures. In contrast, chondrogenic differentiation was attenuated in ASCs expanded under MMC. The ASC immunophenotype was maintained under MMC with significantly higher expression of CD54. However, MMC impaired metabolic activity and differentiation capacity of ASCs in XF/SF conditions. Both the supportive and inhibitory effects of MMC on ASC are culture condition dependent. In the presence of serum, MMC maintains ASC immunophenotype and enhances adipogenic and osteogenic differentiation at the cost of reduced proliferation.
Highlights
Inside the human body, cells are surrounded by a microenvironment that is physiologically crowded with soluble factors, other cells, and extracellular matrix
adipose stem cell (ASC) showed low to moderate expression for hematopoietic progenitor stem cell marker CD34
Careful characterization of ASC behavior with regard to clinically relevant in vitro culture conditions is highly important for the progress of cell-based therapies
Summary
Cells are surrounded by a microenvironment that is physiologically crowded with soluble factors, other cells, and extracellular matrix. The typical in vitro serum protein concentration is 1–10 g/L, and the composition is maintained plain and simple with only the most essential components, for example, attachment and growth factors provided [1]. This poorly corresponds to the original tissue microenvironments. Macromolecular crowders function by way of the excluded volume effect (EVE) [3].
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