Miller, Dylan V.

Chordoma is a tumor of the axial skeleton that is distinctly uncommon in children and adolescents. Previous observations have suggested that chordomas in pediatric patients differ from adult chordomas in presentation, morphology, and behavior. This study examines the clinical and histologic features of chordomas in young patients (≤25 years old). All cases from the Mayo Clinic files were graphed according to age and a bimodal distribution was observed. The 35 cases representing the youngest population were selected for review. Histopathology ranged from low cellularity tumors with lobulated architecture and abundant myxoid matrix (conventional chordoma), to those with varying amounts of chondroid matrix (chondroid chordoma), to more cellular tumors (atypical chordoma), and finally to neoplasms with high-grade spindle-cell differentiation (dedifferentiated chordoma). Over an average follow-up period of 129 months (range 1 to 501 months), there were 13 deaths (37%) and 3 patients with metastasis. This survival rate was slightly better than the reported mortality rate for adults with chordoma, but there was a subset of young patients (those with atypical chordoma) that had a significantly worse survival rate, suggesting that histologic subtyping may be predictive of prognosis.

Atherosclerosis is the major cause of adult mortality in the developed world, and a significant contributor to atherosclerotic plaque progression involves smooth muscle cell recruitment to the intima of the vessel wall. Controversy currently exists on the exact origin of these recruited cells. Here we use sex-mismatched bone marrow transplant subjects to show that smooth muscle cells throughout the atherosclerotic vessel wall can derive from donor bone marrow. We demonstrate extensive recruitment of these cells in diseased compared with undiseased segments and exclude cell–cell fusion events as a cause for this enrichment. These data have broad implications for our understanding of the cellular components of human atherosclerotic plaque and provide a potentially novel target for future diagnostic and therapeutic strategies.

Background— Recent studies have identified cardiomyocytes of extracardiac origin in transplanted human hearts, but the exact origin of these myocyte progenitors is currently unknown. Methods and Results— Hearts of female subjects (n=4) who had undergone sex-mismatched bone marrow transplantation (BMT) were recovered at autopsy and analyzed for the presence of Y chromosome–positive cardiomyocytes. Four female gender-matched BMT subjects served as controls. Fluorescence in situ hybridization (FISH) for the Y chromosome was performed on paraffin-embedded sections to identify cells of bone marrow origin with concomitant immunofluorescent labeling for α-sarcomeric actin to identify cardiomyocytes. A total of 160 000 cardiomyocyte nuclei were analyzed approximating 20 000 nuclei per patient. The mean percentage of Y chromosome–positive cardiomyocytes in patients with sex-mismatched BMT was 0.23±0.06%. Not a single Y chromosome–positive cardiomyocyte was identified in any of the control patients. Immunofluorescent costaining for laminin and chromosomal ploidy analysis with FISH showed no evidence of either pseudonuclei or cell fusion in any of the chimeric cardiac myocytes identified. Conclusions— These data establish for the first time human bone marrow as a source of extracardiac progenitor cells capable of de novo cardiomyocyte formation.