Demineralized Bone Matrix-Induced Ectopic Bone Formation in Rats:In VivoStudy with Follow-up by Magnetic Resonance Imaging, Magnetic Resonance Angiography, and Dual-Energy X-Ray Absorptiometry

Abstract

The aim of this study was to further explore the use of magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and dual-energy X-ray absorptiometry (DEXA) to assess bone formation and blood circulation in a pedicled bone graft substitute. In 14 Wistar rats, initially 10 weeks old, heterogeneous demineralized femur bone matrix implants were wrapped in pedicled adductor thigh muscle flaps. One rat died after surgery. Subsequently, bone formation and maintenance of blood vessel functionality were evaluated in six rats 6 weeks postimplantation by means of in vivo MRI/MRA and postmortem histomorphometry. The other seven rats were left for 12 weeks, whereafter bone formation was evaluated by in vivo DEXA and postmortem histomorphometry. The results demonstrated that after 6 weeks bone formation was present in four of six animals, quantified as 42 (؎35)% and 25 (؎19)% by means of MRI and histomorphometry, respectively. MRA was able to show patency of the pedicles of these four rats only, which suggests that the lack of blood supply in the other two rats is the cause of the failure to form bone. In the 12-week group, histology showed increased bone formation without signs of osteolysis, which was quantified histomorphometrically to be as high as 48 (؎15)%. DEXA failed to show bone formation. It is concluded that in vivo MRI proved to be a reliable method for monitoring ectopic bone formation in a rat model, whereas in vivo DEXA was unable to detect the implants. Furthermore, in vivo MRA proved to be a useful technique for studying the circulation of muscle flaps in this animal model.

Effect of hydrogel porosity on marrow stromal cell phenotypic expression

“…Since MRI contrast is sensitive to the molecular environment through changes in relaxation times T1 and T2, and apparent diffusion coefficient ADC, it can provide images and information that are not available using other techniques [19]. This technique has also been used in vitro and in vivo to study engineered tissues such as cartilage, heart valves, and ectopic bone [20,21].…”

Analysis of osteochondro-induction using growth and differentiation factor-5 in rat muscle

“…Some studies reported that ectopic bone induction was confirmed by implanting GDF-5 on the rat demineralized bone matrix carrier into the subcutaneous tissue (Chang et al, 1994) or muscle pouch of rats (Hotten et al, 1996). However, since the demineralized bone matrix itself has ectopic osteoinduction activity (Jergesen et al, 1991;Garraway et al, 1998;Hartman et al, 2004), it is not clear whether these results purely reflect the ectopic osteoinduction activity of GDF-5. Moreover, no studies have examined the correlation between the in vivo chondroosteoinduction ability of GDF-5 and the amount of induction.…”

Magnetic Resonance Monitoring of Opaque Temperature-Sensitive Polymeric Scaffolds

“…For instance, we have previously shown that temperature-responsive biomaterials based on poly­( N -isopropylacrylamide) (PiPAA) can be used in vitro as microcarriers of encapsulated cells to improve the retention and survival of delivered cardiomyocytes . In the field of regenerative medicine, noninvasive techniques are critical to identify and monitor cell implantation sites, degradation degree, and compatibility of implanted materials with the surrounding tissue. − Therefore, the idea of an injectable hydrogel that can be continuously visualized in vivo in real time offers many advantages, such as the use of minimally invasive procedures and the possibility to dispense with cell labeling.…”