Identification and Purification of Mesodermal Progenitor Cells From Human Adult Bone Marrow

Abstract

Bone marrow–derived mesodermal stem cells may differentiate toward several lines and are easily cultured in vitro. Some putative progenitors of these cells have been described in both humans and mice. Here, we describe a new mesodermal progenitor population [mesodermal progenitors cells (MPCs)] able to differentiate into mesenchymal cells upon appropriate culture conditions. When cultured in presence of autologous serum, these cells are strongly adherent to plastic, resistant to trypsin detachment, and resting. Mesodermal progenitor cells may be pulsed to proliferate and differentiate by substituting autologous serum for human cord blood serum or fetal calf serum. By these methods cells proliferate and differentiate toward mesenchymal cells and thus may further differentiate into osteoblats, chondrocytes, or adipocytes. Moreover MPCs are capable to differentiate in endothelial cells (ECs) showing characteristics similar to microvessel endothelium cells. Mesodermal progenitors cells have a defined phenotype and carry embryonic markers not present in mesenchymal cells. Moreover MPCs strongly express aldehyde dehydrogenase activity, usually present in hematopoietic precursors but absent in mesenchymal cells. When these progenitors are pulsed to differentiate, they lose these markers and acquire the mesenchymal ones. Interestingly, mesenchymal cells may not be induced to back differentiate into MPCs. Our results demonstrate the adult serum role in maintaining pluripotent mesodermal precursors and allow isolation of these cells. After purification, MPCs may be pulsed to proliferate in a very large scale and then induced to differentiate, thus possibly allowing their use in regenerative medicine.

Isolating Mesangiogenic Progenitor Cells (MPCs) from Human Bone Marrow

“…The selective culture conditions described here have allowed the isolation of a novel adherent and almost monomorphic cell population as 1.0% of the hBM-MNCs (0.5 -2.0 x 10 6 hBM-MNCs from 5 -10 ml of fresh BM samples) 5,6 . We identified these large (40 -60 µm in diameter), rounded, quiescent, Ki-67-negative cells as MPCs 5 .…”

“…We identified these large (40 -60 µm in diameter), rounded, quiescent, Ki-67-negative cells as MPCs 5 . Morphologically, they are characterized by a distinctive fried egg-shape with a thick core region surrounded by a flat thin periphery showing lots of filopodia at higher magnification power (white arrows in Figure 1 A.1).…”

“…The MPCs showed to be nestin-positive, slow in cycling, Ki-67-negative, and with chromosomes characterized by long telomeres 5 . They expressed pluripotency-associated transcription factors Oct-4 and Nanog rather than MSC master regulators Runx2 and Sox9…”

“…These cells were morphologically and phenotypically different from MSCs and showed a distinctive gene expression profile as well as characteristic growing/adhesion properties. They retained both mesengenic and angiogenic potential and therefore were named Mesodermal Progenitor Cells (MPCs) 5 . Subsequently, we were able to define selective and reproducible culture conditions to generate MPCs at high grade of purity 6 .…”

Skeletogenesis and the Hematopoietic Niche

“…These plastic adherent colonies have been thought to contain mesenchymal progenitor cells, and likely mesodermal progenitor cells as well (Petrini et al 2009). This would account for recent data indicating that marrow derived progenitor cells generate adipocytes, chondrocytes and osteoblasts, traditional mesenchymal cell types, as well as fibroblasts, smooth muscle cells, endothelial cells, and pericytes/subendothelial cells (Bentley and Foidart 1980;Muguruma et al 2006;Sacchetti et al 2007;Crisan et al 2008;Kalajzic et al 2008;Augello et al 2010;Mendez-Ferrer et al 2010).…”