Measurement of fracture callus material properties via nanoindentation.

In bone fracture healing, the extent to which the injured bone regains stability and strength depends on the mechanical properties of the tissues that are formed during healing. While many techniques have been used to quantify the overall mechanical behavior of fracture calluses, few data exist on the material properties of individual callus tissues. The overall goal of this study was to quantify these material properties. Nanoindentation was performed at multiple locations across thin (200mum), longitudinal sections of rat fracture callus at 35 days post fracture. Following indentation, sections were stained with alizarin red S and alcian blue to obtain semi-quantitative estimates of tissue mineral content and proteoglycan content, respectively. Indentation moduli varied over three orders of magnitude (0.61-1010MPa) throughout the callus. Much of this variation was due to the presence of multiple tissue types: the indentation moduli of granulation tissue, chondroid tissue and woven bone ranged 0.61-1.27MPa (median=0.99MPa), 1.39-4.42MPa (median=2.89MPa) and 26.92-1010.00MPa (median=132.00MPa), respectively. In regions of alizarin red staining, the indentation modulus was correlated (r=0.62, P=0.04) with stain intensity, suggesting a positive correlation between modulus and mineral content in woven bone. In addition, the indentation modulus of woven bone along the periosteal aspect of the cortex increased with distance from the fracture gap (P=0.004). These results demonstrate the usefulness of nanoindentation in characterizing the elastic properties of the heterogeneous mixture of tissues present in bone fracture callus.

Detection of head and neck squamous cell carcinoma among exfoliated oral mucosal cells by microsatellite analysis.

Prompt detection of head and neck squamous cell carcinoma (HNSCC) is vital to successful patient management. In this feasibility study, we used microsatellite analysis to detect tumor-specific genetic alterations in exfoliated oral mucosal cell samples from patients with known cancer. Exfoliated mucosal cells in pretreatment oral rinse and swab samples were collected from 44 HNSCC patients and from 43 healthy control subjects (20 nonsmokers and 23 smokers). We tested a panel of 23 informative microsatellite markers to assay DNA from the matched lymphocyte, tumor (from cancer cases), and oral test samples. Loss of heterozygosity or microsatellite instability of at least one marker was detected in 38 (86%) of 44 primary tumors. Identical alterations were found in the saliva samples in 35 of these 38 cases (92% of those with markers; 79% overall) including 12 of 13 cases with small primaries [stage Tt or Tx (occult primary)] and 4 of 4 cases of patients that had undergone prior radiation. Microsatellite instability was detectable in the saliva in 24 (96%) of 25 cases in which it was present in the tumor, and loss of heterozygosity was identified in the test sample in 19 (61%) of 31 cases. No microsatellite alterations were detected in any of the samples from the healthy control subjects. This approach must now be refined and validated for the detection of clinically occult disease. Microsatellite analysis of oral samples may then become a valuable method for detecting and monitoring HNSCC.

Second esophageal tumors in patients with head and neck squamous cell carcinoma: an assessment of clonal relationships.

Patients with squamous cell carcinoma of the head and neck (HNSCC) often develop second carcinomas elsewhere in the upper aerodigestive tract. Some of these paired tumors share a common origin, reflecting the ability of a single progenitor cell to replicate, expand, and populate contiguous regions of the upper aerodigestive tract-a process referred to as clonal expansion. The geographical limitations of clonal expansion, however, have not been adequately addressed. For example, it is not known whether a neoplastic clone from the oral cavity, pharynx, or larynx can migrate to the esophagus. We compared paired tumors from 16 patients with HNSCC and a second squamous cell carcinoma of the esophagus (ESCC) for patterns of allelic loss on chromosomal arms 3p, 9p, and 17p. Losses at these loci occur early during neoplastic transformation of the respiratory tract. In 14 cases (87%), the paired tumors had discordant patterns of allelic loss, suggesting that these tumors were not clonally related. Conversely, two (13%) of the 16 paired tumors had identical genetic alterations, which suggests clonal expansion as the mechanism underlying tumor multifocality. One clone spread from the hypopharynx into the cervical esophagus, and the other spread from the tonsil to the distal esophagus. Although most second ESCCs appear to arise as independent neoplasms, a clonal population of neoplastic cells is capable of traveling across substantial distances to give rise to second tumors at different anatomical sites.