Purpose: To determine whether combined modality Positron Emission Tomography and Computed Tomography (PET-CT) imaging can pre-operatively identify de-differentiated areas within well-differentiated liposarcomas/ atypical lipomatous neoplasms. Well-differentiated lipo-sarcomas show a reasonably homogeneous lesion with fat signal characteristics on MRI and are managed with surgical excision or regular observation. They can recur locally, but never metastasize. Up to 5% of well-differentiated liposarcomas will contain a de-differentiated component that is not apparent on MRI. When present, this de-differentiated component carries a much worse prognosis and requires more aggressive local management. Currently this is only identified after surgical resection. Pre-operative identification of a de-differentiated component within the lesion by PET-CT would allow for better treatment planning. However, PET-CT is an expensive investigation and has not been reported in this application before, although it has been used for imaging of soft tissue tumours.

Method: We have prospectively enrolled 40 subjects into this study. Eligible subjects presented with a > 8cm and deep well-differentiated liposarcoma in the extremities or retroperitoneum, which was confirmed by MRI. Subjects underwent a pre-operative PET-CT scan to look for areas of de-differentiation within the lesion. The PET-CT results were compared to the final pathological analysis of the surgical specimen. When necessary for diagnostic purposes, cytogenetic analysis was also completed.

Results: Thirty-one of the 40 subjects enrolled have had PET-CT scan and surgery. Seven subjects are waiting for PET-CT and surgery by December 2009. Two subjects were withdrawn from the study: one because the PET-CT scan could not be scheduled prior to surgery, and one because the subject ultimately declined surgery. Of the 31 lesions excised, 2 contained de-differentiated areas within the lesion. The PET-CT detected a small area of low to moderate FDG uptake (thigh lesion, max Standard Uptake Value (SUV) 3.6) for one of these patients; however no uptake on PET-CT was seen for the other (retroperitoneal lesion, max SUV 1.7).

Conclusion: PET-CT does not appear to reliably detect de-differentiated areas within well-differentiated lipo-sarcomas. Our data does not support the use of PET-CT for this purpose as it may be misleading and wasteful of resources.

Purpose: Chondral injuries of the knee are commonly seen at arthroscopy, yet there is no consensus on the most appropriate treatment method. However, untreated cartilage injury predisposes to osteoarthritis contributing to pain and disability. For cell-based cartilage repair strategies, an ex-vivo expansion phase is required to obtain sufficient numbers of cells needed for therapy. Although recent reports demonstrated the central role of oxygen for the function and differentiation of chondrocytes, little is known of the effect of physiological low oxygen concentrations during the expansion of the cells and whether this alters their chondrogenic capacity.

Method: Initial studies of chondrocyte expansion were performed in mature mice, with cells expanded at either atmospheric oxygen tension (21%) or 5% 02 in monolayer cultures. Chondrogenic differentiation was subsequently assessed via micromass culture. Having determined that oxygen tension influences murine chondrocyte expansion and differentiation, similar studies were conducted using adult human chondrocytes taken from knee arthroplasty off-cuts, with mRNA expression of select genes involved in the chondrogenic program analyzed by q-PCR.

Results: Cellular morphology was improved in hypoxic culture, with a markedly more fibroblastic appearance seen after greater than 2 passages in 21% O2. Micromass cultures maintained in hypoxic conditions demonstrated stronger staining with Alcian blue, indicating stronger expression of cartilaginous glycosaminoglycans. Collagen type II mRNA expression was two-fold higher in cells expanded at 5% as compared to expansion at 21% O2. Micromass cultures grown at 21% O2 showed up to a twofold increase in the tissue content of glycosaminoglycans when formed with cells expanded at 5% instead of 21% O2. However, no differences in the mRNA expression or staining for collagen type II protein were observed in these micromass cultures. Hypoxia (5% O2) applied during micromass cultures gave rise to tissues with low contents of glycosaminoglycans.

Conclusion: In-vivo, chondrocytes are adapted to a hypoxic environment. Taking this into account, applying 5% O2 in the expansion phase in the course of cell-based cartilage repair strategies, may result in a repair tissue with higher quality by increasing the content of glycosaminoglycans.