Osteoblastogenesis and Role of Osteoblasts in Calcıum Homeostasis and Remodeling of Bone
Journal Title: Turkish Journal of Endocrinology and Metabolism - Year 2008, Vol 12, Issue 1
Abstract
Bone remodeling is very important for repair of microfractures and fatigue damage and prevention of excessive aging and its consequences. Bone remodeling lasts for about 6-9 months. During this period osteoclasts resorb damaged bone and osteoblasts synthesize new bone. The lifespan of mature osteoclasts is about 15 days and for osteoblasts 3 months. Therefore, the time required for the remodeling of a given segement of bone is much longer than the lifespan of its cells which perform remodeling. A supply of new osteoblasts and osteoclasts are therefore needed for succesful remodeling by the basic multicellular unit. The major event that triggers osteogenesis is the transition of mesenchymal stem cells into bone differentiating osteoblast cells. Osteoblast commitment and differentation are controlled by complex activities. Many factors are involved in the regulation of osteoblastogenesis. Bone morphogenetic proteins and the Wnt glycoproteins play crucial roles in signaling osteoblast commitment and differentiation, and are the only known factors capable of initiating osteoblastogenesis from uncommitted progenitors. They can initiate commitment of mesenchymal cells to osteoblastic lineage. The initial cell division is asymmetric, giving rise to another stem cell and a committed osteoprogenitor. After commitment to the osteoblastic lineage, a osteoprogenitor cell gives rise to the transit-amplifying compartment. At this stage osteoprogenitor cells proliferate intensively. After this stage, the cells are more differentiated and give rise to preosteoblasts which express both STRO1, alkaline phosphatase, pyrophosphate, and type 1 collagen. Preosteoblasts are committed to the osteoblast lineage with extensive replicative capacity, but have no self-renewal capacity. Preosteoblasts form the intermediate stage of osteoblastogenesis. The mature osteoblasts express osteopontin, alkaline phosphatase, bone sialoprotein, and osteocalcin. This stage is responsible for the laying down of bone. Mature osteoblasts have limited replicative potential. About 65% of mature osteoblasts and a proportion of cells in the transient amplifying compartment terminate in apoptosis. Apoptosis is a critical determinant of osteoblast number in the basic multicellular unit. The terminal stage of the bone lineage is the post-mitotic osteocyte which is embedded within the advancing osteoid. A minor component of mature osteoblasts differentiate into lining cells of the bone. Lining cells line the quiscent bone with no remodeling activity. Bone morphogenetic proteins, Wnt glycoproteins, Hedgehog proteins, PPARgama ligands, and transcription factors such as Runx 2 and Osterix play important roles in these critical steps of osteoblastogenesis and bone remodelling. Turk Jem 2008; 12: 18-22
Authors and Affiliations
Neslihan Tütüncü
Keywords
Related Articles
- EP ID EP82883
- DOI -
- Views 187
- Downloads 0
Graves Hastalarında Tiroid Nodülü Varlığı İleri Yaş ve Ilımlı Tirotoksikoz ile İlişkilidir
Amaç: Bu çalışmanın birincil amacı Graves Hastalığı’ndaki (GH) nodüler guatr belirleyicilerinin ortaya konmasıdır. Gereç ve Yöntemler: Çalışmaya 202 ardışık hasta dahil edildi (ortalama yaş: 45, 145 kadın). Tüm hastalar...
The Association of Dehydroepiandrosterone and Dehydroepiandrosterone Sulfate with Obesity, Waist-hip Ratio, and Insulin Resistance in Postmenopausal Women
Recent studies revealed that oral dehydroepiandrosterone (DHEA) reduced weight gain in genetically obese mice without affecting their food intake. We aimed to compare the association of DHEA and dehydroepiandrosterone su...
The Level of Antithrombin III (AT III) in Turkish Diabetics
A natural anti-coagulant AT III plays a defensive role against intravascular coagulation and regulates blood hemostasis. Diabetes is associated with hypercoagulable state. The level of blood AT III levels in the Turkish...
Lithium lntoxication in Type 2 Diabetic Patient After Concurrent Use of Lisinopril and Lithium
Concurrent use of lithium with diuretics, ACE inhibitors and non-steroid antiinflammatory drugs may result in elevated serum lithium levels and lithium intoxication. We present here a case of lithium intoxication in a 75...
Effects of Progressively Increasing Work Rate Exercise on Body Substrat Utilisation
During steady-state of moderate intensity exercise tests, respiratory quotient (RQ) provides an accurate reflection of body substrate utilisation. The body and muscle RQ can be estimated from the increase of CO2 output r...