Hypoxic conditions increase hypoxia-inducible transcription factor 2α and enhance chondrogenesis in stem cells from the infrapatellar fat pad of osteoarthritis patients

Abstract

Stem cells derived from the infrapatellar fat pad (IPFP) are a potential source of stem cells for the repair of articular cartilage defects. Hypoxia has been shown to improve chondrogenesis in adult stem cells. In this study we investigated the effects of hypoxia on gene expression changes and chondrogenesis in stem cells from the IPFP removed from elderly patients with osteoarthritis at total knee replacement. Adherent colonyforming cells were isolated and cultured from the IPFP from total knee replacement. The cells at passage 2 were characterised for stem cell surface epitopes, and then cultured for 14 days as cell aggregates in chondrogenic medium under normoxic (20% oxygen) or hypoxic (5% oxygen) conditions. Gene expression analysis, DNA and glycosoaminoglycan assays and immunohistochemical staining were determined to assess chondrogenesis. IPFP-derived adherent colony-forming cells stained strongly for markers of adult mesenchymal stem cells, including CD44, CD90 and CD105, and they were negative for the haematopoietic cell marker CD34 and for the neural and myogenic cell marker CD56. Cell aggregates of IPFP cells showed a chondrogenic response. In hypoxic conditions there was increased matrix accumulation of proteoglycan but less cell proliferation, which resulted in 3.5-fold more glycosoaminoglycan per DNA after 14 days of culture. In hypoxia there was increased expression of hypoxia-inducible transcription factor (HIF)2α and not HIF1α, and the expression of key transcription factors SOX5, SOX6 and SOX9, and that of aggrecan, versican and collagens II, IX, X and XI, was also increased. These results show that cells with stem cell characteristics were isolated from the IPFP of elderly patients with osteoarthritis and that their response to chondrogenic culture was enhanced by lowered oxygen tension, which upregulated HIF2α and increased the synthesis and assembly of matrix during chondrogenesis. This has important implications for tissue engineering applications of cells derived from the IPFP.

Metabolic programming of mesenchymal stromal cells by oxygen tension directs chondrogenic cell fate

“…In particular, chondrogenic differentiation under hypoxic conditions results in enhanced cartilage formation and suppresses hypertrophic differentiation (15). In contrast, chondrogenic differentiation under normoxic conditions yields less cartilage, which has a clear hypertrophic signature (11,18,19). Here, we demonstrate that oxygen tension can, in fact, metabolically program the chondrogenic fate of MSCs into different subtypes of hyaline cartilage.…”

Viability and neural differentiation of mesenchymal stem cells derived from the umbilical cord following perinatal asphyxia

“…In patients with osteoarthritis, for example, hypoxia has been demonstrated to stimulate the commitment of stem cells in the infrapatellar fat pad to chondrogenesis. 29 Although hypoxia stimulates MSCs to differentiate, in general, the determination of cell lineage is dependent on the environmental milieu through mechanisms that are still incompletely understood. It is equally unclear why the absence of in vitro neural differentiation was observed in cells Cord mesenchymal stem cells following asphyxia H Aly et al collected from preterm infants.…”

Local transplantation of human multipotent adipose-derived stem cells accelerates fracture healing via enhanced osteogenesis and angiogenesis

“…Previous reports revealed expression of angiogenic cytokines (HGF, VEGF), hematopoietic cytokines (G-CSF, SCF) and pro-inflammatory cytokines (IL-6, LIF, TNFa), [42][43][44] as well as secretion of hypoxia-inducible transcription factor (HIF) in fat-derived stem cells under a hypoxic condition. 45 As HIF-2a has been shown to be upregulated under a hypoxic condition in vitro, hMADS cells might also produce HIF which is one of the upstream molecules of VEGF and angiopoietin-1 signaling pathway. This hypothesis is based on the fact that the non-union fracture model used in this study was created with cauterizing periosteum, leading to an ischemic/hypoxic condition around the fracture sites (see LDPI findings).…”