Expression of cell surface markers by cryopreserved feline adipose-derived mesenchymal stem cells (aMSCs). Feline aMSCs expanded from cryopreserved adipose were passaged three times in culture, then collected by trypsinization and immunostained for assessment of cell surface marker expression by flow cytometry, as described in Methods. Feline aMSCs expressed high surface levels of CD90 (A) and CD44 (B) but did not express major histocompatibility complex (MHC) class II (C) or CD4 (D). Isotype controls are represented in red and unstained MSCs are represented in blue. Similar results were obtained with aMSCs from three donor cats (E).