osteoblasti

Osteoblasts are bone-forming cells of mesenchymal origin that synthesize and mineralize the organic component of the bone matrix. They line active bone surfaces, including the periosteal and endosteal surfaces, and are central to osteogenesis, the process by which bone tissue is produced and maintained. In some languages or contexts, these cells may be referred to as osteoblasti.

Osteoblasts arise from mesenchymal stem cells in the periosteum and endosteum and differentiate under the control of transcription factors such as Runx2 and Osterix. They proliferate and secrete a protein-rich organic matrix known as osteoid, which primarily consists of type I collagen and non-collagenous proteins like osteocalcin and bone sialoprotein. The enzyme alkaline phosphatase released by osteoblasts contributes to mineral deposition by increasing local phosphate concentration.

As mineralization proceeds, osteoblasts become embedded in the matrix they secrete, differentiating into osteocytes within lacunae or remaining on bone surfaces as bone-lining cells. This transition links the formation of new bone with the maintenance and signaling functions of mature bone cells.

Osteoblast activity is closely coupled to bone remodeling. They regulate osteoclast differentiation and activity through signaling molecules such as RANKL and osteoprotegerin (OPG). Hormonal and mechanical factors modulate their function; parathyroid hormone, vitamin D, estrogen, and mechanical loading influence formation rates, while estrogen helps limit excessive resorption.

In development and growth, osteoblasts participate in both intramembranous and endochondral ossification, laying down osteoid and driving the mineralization that forms mature bone, which is later organized into lamellar bone through remodeling.