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Minireviews on bone: introductory remarks
Matrix Biology 19 Ž2000. 83
Mini Review
Minireviews on bone: introductory remarks Received 28 December 1999; accepted 4 January 2000
Bone Biology is a field that is receiving increasing attention. This is partly driven by the fact that one of the major medical problems today, osteoporosis, results from alterations in the bones leading to impaired mechanical properties and much increased fracture risk. Indeed a large proportion of fractures in the elderly results from an osteoporotic skeleton. A large number of patients thus have clinical fractures while others may only experience pain in, e.g. the back due to subclinical collapse of vertebral structures. The numbers are increasing where one factor is the growing number of elderly. The burden to society is exemplified by the number of hip fractures that already in 1990 were 1.7 million, a number that is predicted to increase to 6.3 million by the year 2050. In this respect it is worth noting that available information indicates that the number of vertebrate fracture is three times higher. Over recent years novel approaches for therapy and procedures for identifying patients at risk have been introduced. Yet, these approaches are from a biological point of view still at infancy. Our increasing knowledge of the various events in bone biology, particularly at the molecular level including signaling pathways, will promote the development of more efficient agents that target specific events in the very dynamic tissue that bone represents. In short, the problems related to the bone loss in osteoporosis are driven by the necessity to remove
fatigued bone created by the continuous dynamic loading of the tissue. To achieve this, via a complex system of signals, bone cells, are recruited to the affected area and induce differentiation of the osteoclast which forms an acidic environment uniquely permitting the resorption of the targeted fatigued bone. When the cell has accomplished this it will leave and expose a hole, a resorption pit. Cells of osteoblastic nature will be recruited to this pit and induced to form new bone. The problem arises when the new bone formed does not quite match the excavation and there is net loss at each such remodeling cycle. Therapeutic activities today include estrogen supplementation and bisphosphonates that target the resorption phase. Although the detailed mechanisms are only now becoming unravelled, as of today much information that will prove essential for future approaches has been accumulating. The four mini-reviews cover essential areas including what we know about the factors governing osteoclast formation and activity and what we know about the factors important for osteoblast formation and bone production. Dick Heinegard ˚ Lund University, Lund, Sweden
0945-053Xr00r$ - see front matter 䊚 2000 Elsevier Science B.V.rInternational Society of Matrix Biology. All rights reserved. PII: S 0 9 4 5 - 0 5 3 X Ž 0 0 . 0 0 0 4 9 - 4
Mini Review
Minireviews on bone: introductory remarks Received 28 December 1999; accepted 4 January 2000
Bone Biology is a field that is receiving increasing attention. This is partly driven by the fact that one of the major medical problems today, osteoporosis, results from alterations in the bones leading to impaired mechanical properties and much increased fracture risk. Indeed a large proportion of fractures in the elderly results from an osteoporotic skeleton. A large number of patients thus have clinical fractures while others may only experience pain in, e.g. the back due to subclinical collapse of vertebral structures. The numbers are increasing where one factor is the growing number of elderly. The burden to society is exemplified by the number of hip fractures that already in 1990 were 1.7 million, a number that is predicted to increase to 6.3 million by the year 2050. In this respect it is worth noting that available information indicates that the number of vertebrate fracture is three times higher. Over recent years novel approaches for therapy and procedures for identifying patients at risk have been introduced. Yet, these approaches are from a biological point of view still at infancy. Our increasing knowledge of the various events in bone biology, particularly at the molecular level including signaling pathways, will promote the development of more efficient agents that target specific events in the very dynamic tissue that bone represents. In short, the problems related to the bone loss in osteoporosis are driven by the necessity to remove
fatigued bone created by the continuous dynamic loading of the tissue. To achieve this, via a complex system of signals, bone cells, are recruited to the affected area and induce differentiation of the osteoclast which forms an acidic environment uniquely permitting the resorption of the targeted fatigued bone. When the cell has accomplished this it will leave and expose a hole, a resorption pit. Cells of osteoblastic nature will be recruited to this pit and induced to form new bone. The problem arises when the new bone formed does not quite match the excavation and there is net loss at each such remodeling cycle. Therapeutic activities today include estrogen supplementation and bisphosphonates that target the resorption phase. Although the detailed mechanisms are only now becoming unravelled, as of today much information that will prove essential for future approaches has been accumulating. The four mini-reviews cover essential areas including what we know about the factors governing osteoclast formation and activity and what we know about the factors important for osteoblast formation and bone production. Dick Heinegard ˚ Lund University, Lund, Sweden
0945-053Xr00r$ - see front matter 䊚 2000 Elsevier Science B.V.rInternational Society of Matrix Biology. All rights reserved. PII: S 0 9 4 5 - 0 5 3 X Ž 0 0 . 0 0 0 4 9 - 4