The third passage cells were induced by lineage-specific induction factor to osteoprogenitor cells
(OC-AD-MSCs) according to ALVES et al.
The ability to form new bone via BMA transplantation has been confirmed in basic experiments  and is thought to depend on mesenchymal stem cells (MSCs) or osteoprogenitor cells
. The bone marrow is a source of MSCs, which have the potential to differentiate into mesenchymal tissues such as bone, cartilage, and fat .
[sup],, It has been demonstrated that chitosan can improve the proliferation, the differentiation and the mineralization of osteoprogenitor cells
, osteoblasts as well as new bone formation.
It seems that some factors, including bone morphogenetic protein, platelet-derived growth factor, and transforming growth factor-beta have the ability to be chemotactic for fibroblasts and may have some role in aggregating osteoprogenitor cells
at sites of heterotopic ossification.
Guillemot, Laser-assisted bioprinting for creating on-demand patterns of human osteoprogenitor cells
and nano-hydroxyapatite, Biofabrication, 3, 11-17 (2011).
(5) revealed the osteogenic potential of NPY, showing that osteoblast phenotype markers were significantly enhanced in osteoprogenitor cells
stimulated by NPY, probably due to down-regulation of the Y1 receptor.
Four theories of pathogenesis have been suggested in the literature, 1) displacement of bony fragments into adjacent soft tissues and hematoma with subsequent proliferation, 2) detachment of periosteal fragments into surrounding tissues with proliferation of osteoblasts, 3) migration of subperiosteal osteoprogenitor cells
into adjacent soft tissues through periosteal tears due to trauma, and 4) metaplasia of extraosseous cells exposed to growth factors derived from the breakdown of bone fragments displaced within soft tissue during trauma.
The mixture of autogenous cancellous bone and hydroxyapatite contained viable osteoblasts and osteoprogenitor cells
which are essential for the mechanisms of osteogenesis and osteoinduction.21
It is known that the nerve growth factor has a regulatory role in neuroimmune and endocrine interaction and it has been found in periosteal osteoprogenitor cells
. Changes in the functions of these cells may be a facilitating factor in skeletal involvement in patients with CIPA.
For example, polymethylmethacrylate (PMMA) particles have been previously shown to inhibit the osteogenic differentiation both in the bone marrow stromal cells  and in murine MC3T3 osteoprogenitor cells
Skeletal unloading causes resistance of osteoprogenitor cells
to parathyroid hormone and to insulin-like growth factor-1.
In the adult bone marrow microenvironment, hematopoietic stem/progenitor cells (HSPCs) associate closely with osteoblasts or osteoprogenitor cells