Hypoxia Inducible Factor-1α Deficiency Affects Chondrogenesis of Adipose-Derived Adult Stromal Cells

Abstract

Increased cartilage-related disease, poor regeneration of cartilage tissue, and limited treatment options have led to intense research in tissue engineering of cartilage. Adipose-derived adult stromal cells (ADAS) are a promising cell source for skeletal tissue engineering; understanding ADAS cellular signaling and chondrogenesis will advance cell-based therapies in cartilage repair. Chondrocytes are unique-they are continuously challenged by a hypoxic microenvironment. Hypoxia inducible factor-1-alpha (HIF-1alpha), a critical mediator of a cell's response to hypoxia, plays a significant role in chondrocyte survival, growth arrest, and differentiation. By using an established in vitro 3-dimensional micromass system, we investigated the role of HIF-1alpha in chondrogenesis. Targeted deletion of HIF-1alpha in ADAS substantially inhibited the chondrogenic pathway specifically. In marked contrast, deletion of HIF-1alpha did not affect osteogenic differentiation but enhanced adipogenic differentiation. This study demonstrates the critical and specific interplay between HIF-1alpha and chondrogenesis in vitro.

Analysis of the material properties of early chondrogenic differentiated adipose-derived stromal cells (ASC) using an in vitro three-dimensional micromass culture system

“…Alcian blue and collagen II staining indicated the progression of chondrogenesis in the 3D micromasses. In addition to the histology, we have assessed sulfated glycosaminoglycan (sGAG) quantities to evaluate this micromass culture system [33]. Gene expression data demonstrated that ASC underwent early chondrogenesis and obtained the characteristics of prechondrocytes: such as significantly higher levels of Sox-9, the critical transcription factor of chondrogenesis; elevated aggrecan and type II collagen, major components of chondrogenesis [11,20].…”

Environmental preconditioning rejuvenates adult stem cells' proliferation and chondrogenic potential

“…One study has shown that murine ASCs, when differentiated at 2% oxygen, exhibited increased proliferation and fewer chondrogenic markers compared to those differentiated in 21% oxygen [51]. Interestingly, the same investigators later showed that, when murine ASCs were expanded in 2% oxygen, then differentiated at normoxic levels, some chondrogenic markers [GAG content and COL2A1 (type II collagen) expression, but not expression of SOX9 or ACAN ( aggrecan )] were increased compared to those expanded in 21% oxygen [52]. The differences between these two reports could have been a result of reactive oxygen species (ROS) accumulation during long-term exposure to hypoxic conditions in differentiation, which would have led to cell damage and decreased chondrogenic potential [35].…”

Cartilage Tissue Engineering Using Dermis Isolated Adult Stem Cells: The Use of Hypoxia during Expansion versus Chondrogenic Differentiation

“…A study by Mizuno et al . [34] showed enhanced chondrogenesis of immature dermal fibroblasts seeded on collagen/demineralized bone powder sponges in low oxygen (5% O 2 ), and increased production of hypoxia inducible factor-1α (HIF-1α), a known regulator of hypoxic chondrogenic differentiation [35]. Others have elucidated the mechanism of hypoxia-induced chondrogenic differentiation in stem cells [26], [36]–[38], therefore it is the aim of this study to characterize the functional outcomes of DIAS cell exposure to hypoxia.…”