Figure 2.
Summary of important intracellular pathways of signal transduction during osteoblastic differentiation. Cytomechanic stimuli, BMPs and inflammatory stimuli, in particular, encourage osteoblastic differentiation. The expression of some of the listed KO-factors, such as Lef1/Tcf7,13 decreases towards the end of osteogenic differentiation. On the other hand, other expression factors (e.g. Lef1▽N), increase in terminal osteoblastic differentiation.14 The differentiation paths of adipoblasts and osteoblasts from a common progenitor cell separate relatively late, whereby adipose tissue in addition to human bone marrow is suitable as the original tissue used in cell therapies for bone regeneration.15 Due to the small or even lack of expression of MHC-II, mesenchymal progenitor cells have a low immunogenetic potential.16 Moreover, in contrast to other cell types, they have an immunosuppressive effect on neighboring cells. ALK: activin receptor-like kinase; ALP: alkaline phosphatase; APC: activated protein C; BMP: bone morphogenic protein; cbfa: core binding factor; Cdk: cyclin-dependent kinases; CHOP: CCAAT enhancer-binding protein (C/EBP) homologous protein; CTGF: connective tissue growth factor; cAMP: cyclic adenosine monophosphate; COX: cyclo-oxygenase; ERK: extracellular signal-related kinase; LRP: LDL receptor-related protein; MAP: mitogen-activated protein kinase; MHC: major histocompatibility complex; OAZ: Olf-1/EBF-associated zinc finger; PG: prostaglandin(s); PPAR: peroxisome proliferator activated receptor; SF: short form; SnoN: Ski-related novel oncogene; STAT: transducer and activator of transcription; Tob: transducer of erbB2; VEGF: vascular derived growth factor; Wnt: wingless gene; sFRP: secreted frizzled related protein, Lef: lymphoid enhancer binding factor.