FIG. 3.

Transplantation assays comparing L-MSCS and BM-MSCs retention and evidence for phagocytosis (day 4), early survival (2 h), and in vitro assay to explore potential mechanism for survival (anoikis resistance). (A) Retention of PKH26-labeled lung (L-MSCs) versus bone marrow (BM-MSCs)-derived multipotential stromal cells (1×10⁶ cells in 200 μL by tail vein, n=11 mice/group; *P<0.05 vs. L-MSCs or ‘L’). L-MSCs were retained in the lung at a significantly higher rate than BM-MSCs (P<0.001), whether cultured L-MSCs were harvested at log or stationary phase and independent of whether recipient mice were elastase injured or not; phagocytosis as evidenced by CD45 or CD11b (Mac-1) was lower for L-MSCs at 4 days after injection. (B) Two hours after injection, the total percentage of L-MSCs that were viable was greater than the percentage of viable BM-MSCs (*P<0.05) and there was a trend (^†P=0.07) toward a lower proportion of L-MSCs that were apoptotic (Annexin V positive); in vitro assay of anoikis resistance: cells were cultured for up to 4 h in suspension (37°C, 5% CO₂); samples (4/time point) were analyzed throughout this period. (C) Viability was significantly (*P<0.05) higher for L-MSCs than for BM-MSCs 2 and 4 h after start of incubation; L-MSCs showed no decrement in viability during this period. (D) Apoptosis was significantly greater (*P<0.05) in BM-MSCs than in L-MSCs; both cell types showed a significant increase in apoptosis over time (†P<0.05 vs. 1–2 h).