Targeted disruption of mouse fibroblast activation protein.

Human fibroblast activation protein (FAP), a member of the serine prolyl oligopeptidase family, is a type II cell surface glycoprotein selectively expressed by fibroblastic cells in areas of active tissue remodeling, such as the embryonic mesenchyme, areas of wound healing, the gravid uterus, and the reactive stroma of epithelial cancers. Homologues of FAP have been identified in the mouse and Xenopus laevis. FAP is a dual-specificity enzyme that acts as a dipeptidyl peptidase and collagenase in vitro. To explore the role of FAP in vivo, Fap(-/-) mice were generated by homologous recombination. RNase protection analysis and reverse transcription-PCR confirmed the absence of full-length Fap transcripts in mouse embryonic tissues. No FAP protein was detected in Fap(-/-) animals by immunohistochemistry, and no FAP-specific dipeptidyl peptidase activity was found. We report that Fap(-/-) mice are fertile, show no overt developmental defects, and have no general change in cancer susceptibility.

[Spontaneous osteonecrosis of the knee joint: MRT compared to CT, scintigraphy and histology]. / Spontane Osteonekrose des Kniegelenkes: MRT im Vergleich zur CT, Szintigraphie und Histologie.

PURPOSE: We compared MR imaging with scintigraphy and CT in eight patients with spontaneous osteonecrosis of the knee. The histological changes accounting for the MR signal abnormalities were evaluated. METHODS: Eight patients with spontaneous osteonecrosis of the knee joint underwent MR imaging before and after i.v. administration of Gd-DTPA. Nuclear scintigraphy was performed in all 8 patients, three patients also had CT scans of the knee area. Histologic correlation was available in three patients. RESULTS: Increased radionuclide uptake was observed in all patients. In one patient, however, scintigraphy showed increased radionuclide uptake consistent with osteonecrosis only in the medial femoral condyle, while MR imaging demonstrated osteonecrosis both in the medial as well as the lateral femoral condyles. MR demonstrated areas of low signal intensity on precontrast T1-weighted images in the femoral condyle in all patients. All these areas showed high signal intensity on T2-weighted images. On postcontrast T1-weighted images, signal intensity increase was either homogeneous throughout the lesion or it was seen at the periphery of the lesion in a band-like pattern. Histologically, the areas of high signal intensity on T2-weighted and on postcontrast T1-weighted images corresponded to granulation tissue. CONCLUSION: MR imaging detects granulation tissue adjacent to the necrotic zone. Using morphological and signal intensity criteria, MR imaging can be utilised to differentiate spontaneous osteonecrosis of the knee from osteochondritis dissecans, degenerative osteoarthritis, and other conditions affecting the knee joint.

Acute fracture of the femoral neck: assessment of femoral head perfusion with gadopentetate dimeglumine-enhanced MR imaging.

OBJECTIVE: Evaluation of the perfusion and viability of the femoral head after fracture of the femoral neck is important because the outcome of conservative treatment or joint-preserving surgery is adversely affected by the development of capital osteonecrosis. We evaluated the use of MR imaging, before and after IV administration of gadopentetate dimeglumine, for assessing perfusion of the femoral head in 13 patients with acute fracture of the femoral neck. SUBJECTS AND METHODS: Multiecho (1600/30-240 [TR/TE]) MR images were obtained before contrast administration and gradient-echo (315/14, 90 degrees flip angle) MR images were obtained both before and after contrast administration. MR findings were correlated with findings on superselective digital subtraction angiograms of the vessels supplying the femoral head and with clinical-radiographic follow-up for at least 12 months. RESULTS: Digital subtraction angiography showed impaired blood supply to the femoral head in five patients. On contrast-enhanced MR images of these patients, the femoral head did not enhance and was lower in signal intensity than were the enhancing femoral shaft and neck distal to the fracture and the enhancing femoral head on the unaffected side. In the patients with persistent perfusion, contrast-enhanced MR images showed a uniform increase in signal intensity in the femoral shaft and neck as well as the femoral head; the femoral head on the fractured side showed contrast enhancement similar to that on the healthy side. CONCLUSION: These preliminary results indicate that contrast-enhanced MR imaging may be useful for noninvasive evaluation of femoral head perfusion after fracture of the femoral neck. MR findings also may aid the clinician in deciding between joint-preserving therapy and hip arthroplasty.

[Intracranial tumor-like lesions in children and young adults with multiple sclerosis]. / Intrakranielle tumorähnliche Läsionen bei Kindern und jungen Erwachsenen mit multipler Sklerose.

Atypical early manifestations of multiple sclerosis (MS) are common in children and young adults. 6 patients (aged 5 to 33 years) were examined by MR because of confusing neurological manifestations. In addition to small MS lesions there were also large intracerebral lesions which, however, did not occupy additional space but which looked more like tumours or abscesses. The lesions were sharply demarcated cystic formations with margins that enhanced with contrast. The diagnosis of these lesions presents difficulties, the differential diagnosis including MS and its variants, neoplastic, infectious and vascular processes. MR can provide valuable diagnostic information.

[Magnetic resonance tomography in orthotopic liver transplantation]. / Magnetische Kernresonanztomographie bei orthotoper Lebertransplantation.

14 patients with orthotopic liver transplantation were prospectively studied with MR imaging. MR imaging demonstrated a perivascular collar surrounding central portal venous branches in 14 patients. The perivascular collar had low signal intensity on T1-weighted and high signal intensity on T2-weighted images. In 10 of the 14 patients, a perivascular collar was also observed around peripheral portal venous branches. The perivascular collar is probably caused by intraoperative interruption of hepatic lymph vessels and resultant impaired lymph drainage. It is a normal postoperative phenomenon in hepatic transplants. MR imaging is particularly useful in the distinction of postoperative hematoma from other intra- and extrahepatic fluid collections and may provide a noninvasive assessment of liver transplant rejection.