Osteogenic Differentiation Capacity of Human Skeletal Muscle-Derived Progenitor Cells

Abstract

Heterotopic ossification (HO) is defined as the formation of ectopic bone in soft tissue outside the skeletal tissue. HO is thought to result from aberrant differentiation of osteogenic progenitors within skeletal muscle. However, the precise origin of HO is still unclear. Skeletal muscle contains two kinds of progenitor cells, myogenic progenitors and mesenchymal progenitors. Myogenic and mesenchymal progenitors in human skeletal muscle can be identified as CD56+ and PDGFRα+ cells, respectively. The purpose of this study was to investigate the osteogenic differentiation potential of human skeletal muscle-derived progenitors. Both CD56+ cells and PDGFRα+ cells showed comparable osteogenic differentiation potential in vitro. However, in an in vivo ectopic bone formation model, PDGFRα+ cells formed bone-like tissue and showed successful engraftment, while CD56+ cells did not form bone-like tissue and did not adapt to an osteogenic environment. Immunohistological analysis of human HO sample revealed that many PDGFRα+ cells were localized in proximity to ectopic bone formed in skeletal muscle. MicroRNAs (miRNAs) are known to regulate many biological processes including osteogenic differentiation. We investigated the participation of miRNAs in the osteogenic differentiation of PDGFRα+ cells by using microarray. We identified miRNAs that had not been known to be involved in osteogenesis but showed dramatic changes during osteogenic differentiation of PDGFRα+ cells. Upregulation of miR-146b-5p and -424 and downregulation of miR-7 during osteogenic differentiation of PDGFRα+ cells were confirmed by quantitative real-time RT-PCR. Inhibition of upregulated miRNAs, miR-146b-5p and -424, resulted in the suppression of osteocyte maturation, suggesting that these two miRNAs have the positive role in the osteogenesis of PDGFRα+ cells. Our results suggest that PDGFRα+ cells may be the major source of HO and that the newly identified miRNAs may regulate osteogenic differentiation process of PDGFRα+ cells.

Osteogenic lineage commitment of mesenchymal stem cells from patients with ossification of the posterior longitudinal ligament

“…However, the process for the spontaneous phenotypic differentiation of MSCs into osteoprogenitor cells or osteoblasts has not been clearly elucidated. Some authors suggest that miRNA and epigenetic alterations regulate osteogenic differentiation of progenitor cells in muscle sites and in vitro [23,24]. We, too, hypothesize that genetic and epigenetics aspects are major factors controlling lineage commitment of MSCs.…”

Macrophage-derived oncostatin M contributes to human and mouse neurogenic heterotopic ossifications

“…In muscles from HDs, a subpopulation of CD90 -MSCs is reportedly capable of differentiating into osteoblasts, adipocytes, and chondrocytes under appropriate conditions in contrast to CD90 + MSCs, which have limited adipogenic and chondrogenic differentiation potential (21). PDGFRα + cells, which exhibited an in vitro and in vivo osteogenic differentiation potential in normal muscles, have been observed on histological sections proximal to the HO-muscle interface in one trauma patient (18). In our study, patient-derived NHO-MDSCs expressed the classical CD73, CD105, and CD90 mesenchymal markers, and, similar to BM-MSCs, they could differentiate toward osteogenic and adipogenic lineages.…”

“…Indeed, Tie2 + P-DGFRα + Sca-1 + progenitors that reside in the murine skeletal muscle interstitium generated ectopic bone in a similar BMP-2-dependent model of HO (17). Osteogenic differentiation capacity of PDGFRα + cells isolated from healthy human skeletal muscles was confirmed in vivo when they were implanted subcutaneously on hydroxyapatite scaffolds (18). A third possible source of precursors is a cell population with a CD73 + CD105 + CD90 + MSC phenotype, capable of in vitro adipogenic, osteogenic, and chondrogenic (AOC) differentiation, which was isolated from combat-injured muscle from wounded military personnel; however, there is no functional in vivo study to prove that these cells were at the origin of combat injury-induced HOs (19).…”

Understanding heterotopic ossification after spinal cord injury

“…Two types of mesenchymal progenitor cells were found locally in the muscles: satellite cells and interstitial cells [100]. In the series of experiment we have shown that muscle interstitial to regenerate myofibers in vivo following muscle injury [100,278], were all capable of osteogenic differentiation in vitro as previously reported in mouse [109] and human [250].…”

“…Although this remains to be demonstrated genetically with lineage tracking experiments, muscle satellite cell, interstitial cells or MPCs sorted from the muscle of naïve mice, which all have the potential to regenerate myofibers in vivo following muscle injury [101], were all capable of osteogenic differentiation in vitro as previously reported in mouse [109] and human [250]. It has been proposed that substance P might be one of systemic factors responsible for HO in mouse models of FOP [36,126].…”