FIG. 2.

Retention of L-MSCs versus BM-MSCs was evaluated 32 days after syngeneic transplantation (1×10⁶ cells IV) in a murine model of emphysema. (A) Representative flow cytometry plots showing higher frequency of PKH-positive (FL2) cells after L-MSCs transplantation. (B) Based on flow cytometry retention of L-MSCs was significantly greater than BM-MSCs (*P<0.001, n=11/group). (C) Phagocytosis evidenced by CD45 expression was significantly lower in L-MSCs than BM-MSCs. (D) Appearance of PKH-positive (red) clusters of L-MSCs around both injured and noninjured zones on day 32 after transplantation (top panels), and example of CD45^pos cells adjacent to CD45^neg PKH^pos L-MSCs (lower left panel); BM-MSCs (lower right panel) were rarer and appeared as single cells rather than clusters (100–400×). (E) Flow cytometry analysis of PKH-positive cells in mice injected with L-MSCs showing low expression of hematopoietic markers (CD45 and CD11b) and endothelial markers (CD31 and Sca-1) but enrichment for markers found in L-MSCs in vitro (CD73 and CD105). (F) Cryosections containing PKH-labeled L-MSCs were co-stained for a variety of phenotypic markers: PKH stained in close proximity to vimentin, CD31, laminin, col IV, and aqp5, but pixel-by-pixel analysis showed high correlation coefficients (>0.5) only for vimentin with PKH (Pearson r=0.82) or beta-actin with PKH (r=0.71). BM-MSCs, bone marrow-derived mesenchymal stromal cells. Color images available online at www.liebertonline.com/scd