Stem cells that reside in the lining of bone and serve as precursors for future osteoblasts are called which?

• A. Fibroblasts
• B. Chondrocytes
• C. Osteoprogenitor cells
• D. Osteoblasts

Answer: (C)

The main idea is that osteoprogenitor cells are the bone-lining stem cells that give rise to osteoblasts. These cells reside on bone surfaces, in the periosteum and endosteum, and are committed to the osteoblast lineage. When bone formation or repair is needed, they proliferate and differentiate into osteoblasts, the cells that synthesize and secrete the bone matrix. They’re often called preosteoblasts and are derived from mesenchymal stem cells, sitting upstream of osteoblasts in the development pathway.

Fibroblasts are general connective tissue cells, not specific precursors to bone-forming cells. Chondrocytes are cartilage cells, not bone-forming cells. Osteoblasts are the mature bone-forming cells that result from the action of these progenitors, rather than the progenitors themselves. So the studier-friendly term for the lining-resident cells that will become osteoblasts is osteoprogenitor cells.