Vertebral blood perfusion reduction associated with vertebral bone mineral density reduction: A dynamic contrast‐enhanced MRI study in a rat orchiectomy model

Abstract

Purpose: To investigate the relationship between vertebral blood perfusion and vertebral bone mineral density (BMD) in a rat orchiectomy (ORX) model. Materials and Methods:Nine 6-month-old male WistarKyoto rats were used. Computed tomography (CT) bone densitometry and dynamic MRI were performed at baseline and four weeks post-ORX. MRI was performed on a 1.5T clinical MR scanner with a small surface coil placed under the rat lumbar spine region. A sagittal midsection of the lumbar spine was prescribed. Dynamic MRI was performed after a bolus injection of gadolinium-tetraazacyclododecane tetraacetic acid (Gd-DOTA) (0.3 mmol/kg) administered through a tail vein cannula. At a temporal resolution of 0.6 seconds, 800 images were acquired. Regions-of-interest were drawn comprising the medullary component of lumbar vertebrae L3-L6. Maximum enhancement was analyzed.Results: Satisfactory CT and MRI data for analysis was obtained in all animals. Vertebral BMD decreased by 16.6% at four weeks post-ORX (1.134 Ϯ 0.035 vs. 0.946 Ϯ 0.027 g/cm 3 , P ϭ 0.008). MRI maximum enhancement decreased by 17% at four weeks post-ORX (151.5 Ϯ 12.0% vs. 125.8 Ϯ 9.9%, P ϭ 0.015). Conclusion:Vertebral blood perfusion reduction is associated with vertebral BMD reduction in a male rat osteoporosis model. Perfusion MRI provides a new investigative technique for osteoporosis experimental research.

Changes in Bone Metabolism in Young Castrated Male Rats

“…According to laboratory research reported so far, osteoporosis after orchiectomy occurs via three mechanisms: 1) a decrease in calcium reabsorption and an imbalance in bone metabolism following sex hormone deprivation can lead to lowered BMD, 2) an increase in receptor activators of nuclear factor kappa-B ligand (RANKL) in bone marrow (which upregulates free soluble RANKL in the bone marrow of aged rats) can stimulate bone metabolism,22 particularly increased bone turnover in association with increased serum ALP and osteocalcin levels, 2324 and 3) loss of spinal BMD after orchiectomy is correlated with a decrease in spinal blood flow 25…”

Evaluation of perfusion-related and true diffusion in vertebral bone marrow: a preliminary study

“…Concerning the relationship between BMD and bone perfusion, several authors have reported that MRI-derived perfusion parameters of vertebral bone marrow were decreased significantly in osteoporotic subjects compared with those of normal subjects [17][18][19][20][21][22]. These results suggest that a decrease in vertebral blood flow may be associated with a decrease in the BMD.…”

“…Bone demineralization depends on various factors, such as bone perfusion, metabolism of bone cells, and the structure of the bone matrix [19]. Thus, being able to predict these factors noninvasively before significant bone loss occurs would help to prevent BMD decline in postmenopausal women and, consequently, to lower their incidence of compression fractures [7].…”

Compromised perfusion in femoral head in normal rats: distinctive perfusion MRI evidence of contrast washout delay

“…Osteotomy of the proximal femur reduces intra-osseous pressure and pain in patients with osteoarthritis of the hip [14]. MR signal changes observed via DCE MRI can be due to a combination of, among other things, capillary permeability, tissue blood perfusion and interstitial tissue pressure [11,[16][17][18]. In the DCE MRI study, washout is related to the back-flow of contrast agent from interstitial space to the bloodstream and the elimination of contrast agent from the body via the kidneys.…”