Figure 5: Chondrogenic pellet culture of normal and OA-derived stem cells. Stem cell lines were cultured in high density pellets in chondrogenic media for 28 days then processed for histology. [A] Stem cell pellets from normal donors exhibited extensive labelling for Safranin-O, that stains proteoglycan glycosaminoglycan chains in the extracellular matrix. [B] OA-derived stem cell pellets were anemic in comparison.