W. Richter (Heidelberg, DE)
Orthopaedic University Hospital Heidelberg Research Centre for Experimental OrthopaedicsPresenter Of 1 Presentation
12.2.6 - Sulfation of Glycosaminoglycan Hydrogels Instructs Chondral Versus Endochondral Lineage Decision of Mesenchymal Stroma Cells In Vivo
Abstract
Purpose
Exit from multipotency and lineage commitment of mesenchymal stroma cells (MSC) depends on microenvironmental cues from the stem-cell niche but steering cell-fate into the desired lineage in vivo remains a challenge. Increasing evidence suggests that glycosaminoglycans can be used to activate or sequester growth factors with the specific action depending on sulfation levels. We postulated that differentially sulfated biomaterials can aid developmental lineage instruction of MSC to guide tissue morphogenesis in vivo.
Methods and Materials
Injectable TGFβ-loaded-hydrogels designed at selected different sulfation status of the covalently coupled glycosaminoglycan, to grow true articular-cartilage-like tissue from MSC in vivo, were implanted into subcutaneous pouches of immunodeficient mice. The chondrogenic differentiation, hypertrophy and mineralization were investigated on day-28 and 56 explants by histology, ELISA, qPCR, WB and µCT analysis.
Results
By application of a new injectable TGFβ-loaded-hydrogel we here gained the ability to control skeletal stem-cell fate in vivo down the chondral versus the endochondral pathway depending on the sulfation status of the covalently coupled glycosaminoglycan. High sulfation allowed for long-term TGFβ-retention and silencing of Hedgehog-, BMP- and WNT-pathways and installed pro-chondrogenic and anti-hypertrophic cues in MSC. This permitted in vivo growth of permanent, collagen-type-II-rich neocartilage with long-term resistance to calcification and bone formation. Reduction of sulfation supported Hedgehog/BMP/WNT-signaling switching lineage commitment into endochondral differentiation with strong hypertrophic/osteogenic marker expression, tissue calcification and bone formation.
Conclusion
Our work identifies glycosaminoglycan sulfation as crucial niche instruction signal to determine the chondral stem-cell fate via silencing of prohypertrophic growth factor pathways providing the first proof-of-principle how glycosaminoglycan modification-patterns can determine cell lineage-choice during tissue morphogenesis in vivo.