Identification of biomarkers indicative of functional skeletal stem cells

Abstract

Structured Abstract Objectives Skeletal stem cells (SSCs) are characterized by expression of cell surface biomarkers and their ability to differentiate into bone, cartilage and fat. However, the current biomarkers used to identify these cell populations are not cell‐type‐specific or indicative of the differentiation status of these cells and are therefore unreliable. Our objective was to identify alternative cell surface biomarkers and transcription factors shared between SSCs isolated from the bone marrow (BM) and those derived from pluripotent stem cells (PSC). Materials and Methods Human PSCs were induced into SSCs. FACS and qRT‐PCR were used to determine differences in expression of cell surface biomarkers and transcription factors between SSCs derived from PSCs and isolated from BM, in differentiating cells, in cells from early and late passage, and in fibroblasts. Results A significant reduction in proliferation and capacity of SSCs to differentiate into adipocytes and osteoblasts was observed after 3 passages. Protein and mRNA analysis indicated that commonly used biomarkers remain highly expressed in cells that lost capacity for differentiation. However, integrin α6 (CD49f) and transcription factors GATA6, PRDM16, SIM2 and SOX11 were significantly upregulated in SSCs compared to fibroblasts. In early stages of adipogenic and osteogenic differentiation, the expression of CD49f, GATA6 and SIM2 was reduced in later passage cells, which have limited proliferation and differentiation capabilities. Conclusions Our results suggest that CD49f and transcription factors GATA6 and SIM2 identify functional SSCs.

Isolation and Culture of Human Stem Cells from Apical Papilla under Low Oxygen Concentration Highlight Original Properties

“…CD49f is associated with multipotency and maintenance of stemness in umbilical cord blood-derived MSCs through regulation of Oct4 and Sox2 [47]. It is also upregulated in skeletal stem cells (SSC) as compared to fibroblasts and this marker has been associated with functional SSCs [58]. However, CD49f-positive BM-MSCs showed higher clonogenicity and differentiation capacity in vitro than CD49f-negative BM-MSCs [59], a property not observed in SCAPs mainly at late passage.…”

Cell-controlled dynamic surfaces for skeletal stem cell growth and differentiation

“…These surfaces act to reduce SSC adhesion formation compared to planar surfaces resulting in changes in mitogen related signalling (e.g., extracellular signal-related kinase, ERK1/2, and c-jun n-terminal kinase, Jnk) 7 – 9 . Integrins, transmembrane receptors that form cell adhesions and that ligate to peptide motifs in the extracellular matrix, such as RGD, link to signalling proteins such as focal adhesion kinase, FAK, and the actin cytoskeleton to effect phenotype-linked signalling pathways 10 – 12 . These mitogens are well known for their roles in SSC differentiation along with Rho A kinase signalling to facilitate adipogenesis where lack of spreading results in low levels of mitogen stimulation and lack of intracellular tension or to drive osteogenesis through mitogen activation of transcription factors such as runt related transcription factor 2 (RUNX2) and adhesion-driven spreading providing high levels of intracellular tension 13 – 15 .…”