Evidence for tissue-resident mesenchymal stem cells in human adult lung from studies of transplanted allografts
J. Clin. Invest. Vibha N. Lama, et al. 117:989 doi:10.1172/JCI29713 [Go to this article.]

Figure 3
Mesenchymal cells isolated from BAL fluid of lung transplant recipients differentiate to multiple connective tissue lineages. (A) Cultured mesenchymal cells from 15 BAL samples and 10 individual CFU-Fs were investigated for in vitro multilineage differentiation capacity. Osteocytic differentiation was indicated by calcium deposition as demonstrated by alizarin red staining (red) in treated cells (bottom left). This was absent in control untreated cells (top left). Accumulation of lipid droplets (indicating adipocytic differentiation) was demonstrated by staining with oil red O in treated cells (bottom center; untreated control is shown in top center). Immunofluorescence staining with anti-human aggrecan polyclonal antibody demonstrates the presence of the extracellular matrix proteoglycan aggrecan, indicative of chondrocytic differentiation in treated cells (bottom right panel; aggrecan-FITC: green; DAPI: blue). A contiguous section stained with control IgG antibody is shown (top right). (B) RT-PCR was performed to analyze the expression of mRNAs specifically related to adipogenic, chondrogenic, and osteogenic activity under inductive culture conditions. Ten cell lines generated from individual CFU-Fs were cultured in either control or differentiation-inducing conditions. Expression of PPARγ and aP2 (indicative of adipogenic activity), type II collagen and type IX collagen (Coll. type II and IX; indicative of chondrogenic activity), and osteopontin (indicative of osteogenic activity) was upregulated in treated cells. Lanes demonstrate RNA isolated from untreated cells, RNA isolated from cells undergoing differentiation, and RNase-Free Distilled Water (UltraPure; Invitrogen), respectively. B2M, β₂-microglobulin. (C) Real-time PCR provided a quantitative analysis of increased relative expression of mRNAs specifically related to adipogenic, chondrogenic, and osteogenic activity under inductive culture conditions.