Biomedical Engineering Reference
In-Depth Information
3
Bone repair and regeneration
N. B a l d i N i, E . C E N N i , G. C i a p E t t i,
d. GraNChi and l. S ava r i N o,
istituto ortopedico rizzoli, italy
Abstract
: Bone tissue has remarkable repair capacity, and generally heals
by regeneration. this unique potential, expressed during remodelling and
bone fracture healing, is tuned by a complex interplay of active factors and
responding cells, which resides on an informative extracellular matrix and
acts under a strict genetic control and different mechanical stimuli. the
coordinated interaction of these elements is increasingly understood thanks
to progress in cellular and molecular biology. this chapter deals with the
sequential events leading to bone repair, with special attention given to the
role of mesenchymal stem cells in regenerating bone. the genetic control
of bone healing, the pathways underlying such process and the regulation
by a variety of growth factors and cytokines are outlined according to the
recent literature. Understanding the key elements of bone regeneration and
their cross-talk is not merely a theoretical advancement in the knowledge
of the physiological turnover of bone tissue, but offers practical tools for
increasing the efficacy of orthopaedic procedures, such as the delivery of
pro-osteogenic growth factors or mesenchymal stem cells.
Key words
: bone, bone marrow, bone morphogenetic proteins, bone repair,
fracture, growth factor, mesenchymal stem cells, osteoblast, regeneration.
3.1 Introduction
Bone is a dynamic, vascular, living tissue that undergoes constant remodeling
throughout life. Constant remodelling provides a mechanism for scar-free
healing and regeneration of damaged bone tissue. this property applies not
only to the sequence of events that are initiated in response to injury, such
as fracture, but also to the healing of bone around and within endosseous
implants. Notably, the molecular mechanisms that regulate skeletal tissue
formation during embryological development are recapitulated during
bone repair.
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Multiple factors, including growth and differentiation factors,
hormones, cytokines and extracellular matrix, interact with different cell
types, including mesenchymal stem cells (MSCs), bone and cartilage forming
cells, endothelial cells and bone resorbing cells that are recruited at the
injury site. these factors regulate intracellular and extracellular molecular
signalling for bone induction and conduction through various processes
such as migration, proliferation, chemotaxis, differentiation and extracellular
protein synthesis.
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