Abstract 19152: Lamin A/C-Deficient Bone Marrow-Derived Mesenchymal Stem Cells Exhibit Spontaneous Pre-Adipogenic Conversion
Laminopathies are disorders that affect multiple tissues including skeletal muscle as in Emery-Dreifuss muscular dystrophy (EDMD) and cardiac as in dilated cardiomyopathy (DCM). They arise from mutations in the LMNA gene that encodes the nuclear envelope proteins lamins A/C. To date, the underlying mechanisms are poorly understood. Recently, several studies established a link between lamin A and dysfunction of adult stem cells. Considering that muscular laminopathies adversely affect tissues of mesenchymal origin, we rationalized that this may be in part attributed to altered differentiation of MSCs. Our aim is to characterize the differentiation of MSCs isolated from an EDMD (Lmna-/-) mouse model which also develops DCM. Marrow aspirates from age- and gender- matched Lmna+/- and Lmna+/+ littermates were used as controls. After limited passages in tissue culture, we noted that a large proportion of the Lmna-/- MSCs readily differentiated into fat-containing cells without pre-stimulation with adipogenic supplements. Grown under similar conditions, we did not observe any changes in the control groups. Absorbance measurements of Oil Red O stain alcohol extracts showed significantly higher quantities of fat-containing droplets in Lmna-/- MSCs (2.209 ± 0.039) compared to wild-type (0.095 ± 0.019) and heterozygous controls (0.062 ± 0.001); (mean OD520 ± SEM); p<0.01. Likewise, we observed similar PPAR-gamma -dependent pre-adipogenic conversion in Lmna-/- mouse embryo fibroblasts (MEFs) grown to over-confluence in monolayers in vitro. Real-Time PCR quantification showed no significant induction in the expression of the transcriptional regulators SREBP-1 and FAS post adipogenic stimulation in MEFs, but both had higher baseline expression in Lmna-/- compared to controls. IHC staining of paraffin-embedded tissue sections of de-calcified bone marrow showed elevated expression of FABP-4 in Lmna-/- mice compared to controls, suggesting an in vivo predisposition of Lamin A/C - deficient marrow - derived MSCs to spontaneous adipogenic conversion. Research is underway to characterize the expression of other transcriptional regulators in MSCs and in bone marrow sections from Lamin A/C - deficient mice.
- © 2013 by American Heart Association, Inc.