title: Hyperosmolarity and hypoxia induce chondrogenesis of adipose-derived stem cells in a collagen type 2 hydrogel.
abstract: Apart from soluble growth factors, various other biophysicochemical cues are known to promote chondrogenesis. Under physiological conditions, cartilage in the joint comprises a hyperosmotic and hypoxic environment. Therefore, in this study, we examined the inductive effects of hyperosmotic and/or hypoxic conditions on adipose stem cells (ASCs) and compared them with conventional TGFβ1-induction. After encapsulation in collagen type II hydrogels and specific induction, ASCs were assessed for viability, proliferation, morphology and chondrogenic differentiation potential. Viability was similar under all conditions, with low proliferative activity. After 4 days, hypoxia and/or hyperosmolarity did not affect round cell morphology, while cells were mainly stretched in the TGFβ1-induced group. At 21 days, the TGFß1-treated group had aggregated into a cell nodule. Hyperosmolarity mimicked this aggregation to a lesser extent, whereas cells under hypoxia stretched out after 21 days, with a combined effect in the hypoxic/hyperosmotic group. Both individual and combined hyperosmotic and/or hypoxic conditions significantly upregulated SOX5, SOX9, COMP and Link-p gene expression compared with the non-induced group, and to similar levels as the TGFβ1-induced group. GAG synthesis in both hydrogel and medium was increased under hypoxic conditions, whereas hyperosmolarity decreased GAG formation in the hydrogels, but increased GAG formation in the medium. We conclude that in a joint mimicking the three-dimensional (3D) micro-environment, a combination of hyperosmolarity and hypoxia is able to induce chondrogenesis to the same extent as TGFβ1. This might lead to an interesting alternative when considering short-term triggering in a one-step surgical procedure for the treatment of cartilaginous defects.
authors.affiliation: Department of Plastic, Reconstructive and Hand Surgery, VU University Medical Centre, Amsterdam, The Netherlands.
authors.forename: Wouter J F M
authors.initials: WJ
authors.lastname: Jurgens
authors.forename: Zufu
authors.initials: Z
authors.lastname: Lu
authors.forename: Behrouz
authors.initials: B
authors.lastname: Zandieh-Doulabi
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Kuik
authors.forename: Marco J P F
authors.initials: MJ
authors.lastname: Ritt
authors.forename: Marco N
authors.initials: MN
authors.lastname: Helder
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D000818:Animals; D015687:Cell Hypoxia / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002645:Chickens; D020219:Chondrogenesis / Q000187:drug effects* / Q000235:genetics; D024043:Collagen Type II / Q000494:pharmacology*; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D009994:Osmolar Concentration; D013194:Staining and Labeling; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D013314:Stress, Mechanical; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
chemical_list: D024043:Collagen Type II; D053773:Transforming Growth Factor beta1; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate