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Stem Cells in Endocrinology - part 8

Tu sửa là thành phần cuối cùng cho quá trình chữa bệnh gãy xương. Các tu sửa "mô tả các sự kiện năng động kết hợp với tái tạo xương và cân bằng nội môi trong bộ xương trưởng thành. Mô hình liên quan đến quá trình tương tự như điêu khắc của xương trước khi đóng cửa các tấm đầu xương. | Chapter 10 Bone Repair With Mesenchymal Stem Cells 189 2.3. Remodeling Remodeling is the final component to the fracture healing process. The term remodeling describes the dynamic events associated with bone regeneration and homeostasis in the mature skeleton. Modeling involves processes similar to the sculpting of bone before the closure of the epiphyseal plates. Homeostatic remodeling can be envisioned as an activation-resorption-formation process. Activation occurs by stimulating osteoblasts with signaling factors such as parathyroid hormone to vacate an area of bone. After the bone is vacated osteoclasts take residence become stimulated attach resorb and eventually cease resorbing and deattach. Other signals are present in Howship s lacunae osteoclastic resorptive pits that attract osteoblasts that secrete osteoid which on calcification restores bone. This dynamic alternating interaction between osteoblasts and osteoclasts has been described as the basic multicellular bone unit and the resulting bone is the basic structural unit 34 . This activation-resorption-formation process occurs over a 4- to 6-month time frame. 2.4. Fracture Healing Mechanisms to Direct the Development of New Technologies The knowledge gained in deciphering the mechanisms and time course of fracture healing provides the physiologic directive for developing rational therapeutics. For a successful regenerative process cells extracellular matrix blood vessels and signaling molecules extracellular and intracellular must be systematically arranged in space and time to ensure and sustain the delicate balance needed for bone regeneration. For most regenerative applications the autogenous graft is the benchmark that alternatives should be judged against. Autografts and allogeneic banked bone provide patients with bone deficiencies the greatest chance for regeneration. Successful clinical outcome from autografts can exceed 80 whereas allogeneic preparations are generally less successful 52 53 . .