Increase In Bone Blood Flow Research Articles

Possible participation of prostaglandins in the increase in the bone blood flow in oophorectomized female rats.

The aim of this study was to verify the possible role of prostaglandin (PG) in the increase in the bone blood flow of female rats after oophorectomy (OOX). In two experiments we determined blood flow in the tibia and distal femur (85Sr-microspheres) and 24-h incorporation of 45Ca and 3H-proline. Acetylosalicyclic acid (ASA, 0.13% in the food for 4 weeks) was used to suppress the production of PG. There was an increase in the bone blood flow after OOX (performed 4 weeks prior to the experiment), no change after ASA alone and significant reduction by ASA of the OOX-induced increase in the bone blood flow. In both groups of OOX females there was a decrease in tibial bone density and ash weight. The changes in 45Ca incorporation were similar to those in the blood flow while the changes in 3H-proline incorporation were not significant. Thus, the effect of ASA, i.e. suppression of the OOX-induced increase in the bone blood flow, is consistent with the possible role of PG (probably PGE2) in the increase in bone blood flow of OOX female rats.

OP-1 injection increases VEGF expression but not angiogenesis in a rabbit model of distraction osteogenesis

We have previously shown that a single injection of rhBMP-7 (OP-1) applied to the regenerate early during distraction accelerates bone consolidation in a rabbit model of distraction osteogenesis. In the present study, we hypothesised that the injection of OP-1 improves bone consolidation by increasing blood flow to the distracted site. Blood flow into the regenerate of a rabbit model was measured and vascular endothelial growth factor (VEGF) expression was tested using semi-quantitative PCR. Immunohistochemistry was used for assessing the temporal and spatial expression of platelet endothelial cell adhesion molecule (PECAM), VEGF and its receptors following OP-1 injection. We observed a higher expression of VEGF and its receptors in the regenerate with OP-1 treatment. However, there was no difference in the increase in bone blood flow nor PECAM expression between the treated and control groups of animals. Interestingly, the increased expression of VEGF and its receptors was associated with chondrocyte and fibroblast-like cells, but not with endothelial cells. These results suggest that accelerated ossification by OP-1 may depend on a non-vascular mechanism, possibly involving a non-angiogenic function of VEGF signalling.

Bone blood flow after spinal paralysis in the rat

The goal of this study was to investigate the acute and chronic effects of paralysis induced by spinal cord section or sciatic neurotomy on bone blood flow in the rat. Regional bone blood flow was measured in the early stage with the hydrogen washout technique and the change of whole bone blood flow was measured in the early and the late stages with the radioactive microsphere technique. Four to 6 h after cordotomy at the level of the 13th thoracic vertebra, the regional bone blood flow in the denervated tibia increased significantly (p less than 0.01). After hemicordotomy with rhizotomy at the same level, the regional bone blood flow in the denervated tibia increased significantly (p less than 0.05) 6 h postoperatively. The whole bone blood flow in the denervated tibia had also increased significantly (p less than 0.05) at 6 h and at 4 and 12 weeks postoperatively. After sciatic neurotomy, the regional and the whole bone blood flow in the paralytic tibia did not change significantly. The present study demonstrated that monoplegic paralysis caused an increase in bone blood flow in the denervated hind limb from a very early stage. It was suggested that the spinal nervous system contributed to the control of bone blood flow.

Effect of muscle flap coverage on bone blood flow following devascularization of a segment of tibia: an experimental investigation in the dog.

Severe tibial fractures may be associated with soft tissue loss, devascularization of cortical bone, and significant morbidity. Local rotational muscle flap coverage is used to obtain coverage of acute open tibial fractures and to treat chronic osteomyelitis of the tibia. The purpose of this study was to determine (a) the longitudinal and cross-sectional regional blood flow characteristics of the canine tibia and (b) whether a muscle flap was superior to vascularized skin coverage in restoring blood flow to devascularized canine tibial cortex. A 2.5-cm segment of tibia between two standardized osteotomies was devascularized. The segment was replaced anatomically and stabilized with a plate. The animals were divided into two experimental groups: (a) skin coverage (n = 8), and (b) muscle flap coverage (n = 8). Thirty-one days postoperatively Ce141 microspheres were injected to measure bone blood flow. The tibial diaphysis was divided into proximal, middle (devascularized), and distal segments. The unoperated leg was used as a control. In the control tibiae, the middle segment was less vascular than either the proximal or distal segment and no difference between anterior and posterior cortical blood flow was observed. Blood flow to the devascularized segment of tibia was significantly greater when it was covered with a muscle flap (p less than 0.025). The most significant increase in bone blood flow in the muscle flap coverage group versus the skin coverage group occurred in the anterior cortex of the tibia (p less than 0.005). This may be clinically important since the soft tissues over the anterior tibia are commonly deficient following open fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone loss and bone blood flow in paraplegic rats treated with calcitonin, diphosphonate, and indomethacin.

Sham-operated (SO) and paraplegic rats were treated from the day of operation during a period of 4 or 6 weeks with salmon calcitonin 4 IU/kg/day or a diphosphonate (APD) 1mM/kg/day or indomethacin 2.5 mg/kg/day. The consequence of spinal cord section on the femur and tibia is a loss of mineral which affects predominantly trabecular bone (-24 and -13% in calcium content for the tibial metaphysis and the whole bone, respectively, when compared with the SO controls), a twofold increase in bone blood flow as measured by the technique of the microspheres trapping, a moderate decrease of the 72 hour 45Ca accretion rate in the bone shaft, and an increase in the number of metaphyseal osteoclasts in the tibia. In paraplegics, all three drugs inhibit bone loss to some degree, calcitonin and indomethacin being mostly effective on the cortical bone of the shaft, and APD tremendously increasing the trabecular network of the metaphysis. APD is the only drug to exhibit a significant effect on the calcium content of the bones of the SO controls, but some effect is apparent for calcitonin on X-rays and histological preparations. The increase in bone blood flow in paraplegics is unaffected, this point being discussed in view of the hypothesis of the resorptive action of prostaglandins produced by newly formed vessels. 45Ca accretion rate increases in the shaft of calcitonin-treated paraplegics, whereas it decreases in APD-treated controls and paraplegics. The number of osteoclasts decreases in paraplegics treated with calcitonin and indomethacin, and increases in both controls and paraplegics treated with APD.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of orchidectomy on bone metabolism in aging rats.

We have shown that orchidectomy in postpubertal 55-day-old rats led beyond 2 months to a decrease in bone growth and loss of weight. At 1 month postorchidectomy, we observed a three-fold increase in bone blood flow, an increase in calcium accretion rate, and an increase in the number of osteoclasts in the metaphysis. In the present experimental study, orchidectomy was performed in 1-year-old rats when bone growth in length was no longer measurable. In the tibia and femur we observed a decrease in bone volume, a still more rapid decrease of bone calcium during the first postoperative month, a thinning of the cortical width, an initial increase in calcium accretion rate (+20% when compared to 31 days controls) followed by a decrease at 120 days (-22% and -11% when compared to controls for tibia and femur respectively), a 29% increase in bone blood flow, and an increase in the number of osteoclasts. We conclude that androgen deprivation in young and old animals leads to a modified bone architecture, independent of the androgen impact on bone growth.

The role of skeletal blood flow in determining the uptake of 99mTc-methylene diphosphonate.

The increased uptake of bone-seeking radionuclides following a fracture has been stated to be due to an increase in bone blood flow, resulting in an increase in capillary surface area available for exchange. This paper examines the relationship between the maximum instantaneous extraction of 99mTc-MDP and blood flow in normal canine tibia. The findings, consistent with the model of capillary action proposed for muscle by Renkin and Crone, are applicable to bone. There is no evidence that in normal bone the surface area available for exchange responds to an increase in bone blood flow.

Bone Marrow Reactions to Trauma Stimulation of Erythropoietic Marrow by Mechanical Disruption, Fracture or Endosteal Curettage

AbstractThe present series of studies were designed to examine the effect of artificially altered bone blood flow on activity of the contained marrow. In normal animals bone blood flow was increased locally by fracture, endosteal curettage, and following mechanical disruption of the marow. Local stimulation of erythropoietic marrow was demonstrated following each procedure. Local injury to bone circulation followed high doses of radiation and resulted in permanent marrow aplasia.Attempts to apply the implications of these studies to therapy of two patients with marrow failure produced inconclusive results. One patient with severe anemia due to idiopathic myelofibrosis improved abruptly and significantly following endosteal curettage of one femur. Unexpectedly there was no demonstrable increase in blood flow in the operated bone and improvement in marrow occurred in skeletal areas other than the operative site.In a second patient with severe anemia and Fanconi's syndrome, endosteal curettage of one femur resulted in a marked local increase in bone blood flow with no evidence of stimulation of marrow locally or at other sites and no improvement in clinical condition until institution of androgen therapy.Further clinical trials of endosteal curettage as a therapeutic measure would appear to be justified.

Effect of Increased Bone Blood Flow on Bone Metabolism

A primary increase in effective bone blood flow, as detected by the distribution of intravenously injected 86Rb, was produced in the bones of one lower extremity by unilateral sympathectomy in immature sheep. Animals studied at various intervals during the 18 days after sympathectomy revealed no measurable alteration in the physical bone density (Gm/cc of dried bone), percentage of ash, number or size of cortical blood vessels or, as determined by quantitative microradiography, in the percentage of surface on which formation and resorption were occurring. The experimental results suggest that a temporary primary increase in bone blood flow does not cause measurable alterations in the metabolism of the bone.