The Key Role of the Blood Supply to Bone

Abstract

The importance of the vascular supply for bone is well-known to orthopaedists but is still rather overlooked within the wider field of skeletal research. Blood supplies oxygen, nutrients and regulatory factors to tissues, as well as removing metabolic waste products such as carbon dioxide and acid. Bone receives up to about 10% of cardiac output, and this blood supply permits a much higher degree of cellularity, remodelling and repair than is possible in cartilage, which is avascular. The blood supply to bone is delivered to the endosteal cavity by nutrient arteries, then flows through marrow sinusoids before exiting via numerous small vessels that ramify through the cortex. The marrow cavity affords a range of vascular niches that are thought to regulate the growth and differentiation of hematopoietic and stromal cells, in part via gradients of oxygen tension. The quality of vascular supply to bone tends to decline with age and may be compromised in common pathological settings, including diabetes, anaemias, chronic airway diseases and immobility, as well as by tumours. Reductions in vascular supply are associated with bone loss. This may be due in part to the direct effects of hypoxia, which blocks osteoblast function and bone formation but causes reciprocal increases in osteoclastogenesis and bone resorption. Common regulatory factors such as parathyroid hormone or nitrates, both of which are potent vasodilators, might exert their osteogenic effects on bone via the vasculature. These observations suggest that the bone vasculature will be a fruitful area for future research.

Skeletal Blood Flow in Bone Repair and Maintenance

“…As a consequence of this environment, the blood vessels in bone are highly active, not simply a passive source for the delivery of nutrients (2). Readers are referred to recent publications for more information about the active processes of the vasculature not covered in this review, including the vascular niche and hypoxia-driven signaling pathways (3)(4).…”

Effects of hibernation on bone marrow transcriptome in thirteen-lined ground squirrels

“…1). During torpor, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) have adapted to prolonged periods of immobility, hypometabolism, hypothermia, and oxidative stress, each capable of reducing bone marrow activity (49,53). In one study, irradiation of hibernating ground squirrels showed a delay in bone marrow damage until after the animals had aroused (14).…”

Hypoxia and Bone Metastatic Disease

“…Although the vasculature does not indicate absolute oxygenation, it can give valuable insight into the oxygen availability in a particular region of the bone. As previously proposed [40], arteries enter the bone through the cortex, run centrally along the diaphysis and branch into smaller arterial vessels near the endosteal surface [41, 35]. Here arterial vessels give rise to sinusoids that coalesce as a central sinus at the center of the diaphysis.…”