Z Schwartz

Caveolin-1 knockout mice have increased bone size and stiffness

The skeletal phenotype of the cav‐1−/− mouse, which lacks caveolae, was examined. μCT and histology showed increased trabecular and cortical bone caused by the gene deletion. Structural changes were accompanied by increased mechanical properties. Cell studies showed that cav‐1 deficiency leads to increased osteoblast differentiation. These results suggest that cav‐1 helps to maintain osteoblast progenitors in a less differentiated state.

Membrane Estrogen Signaling Enhances Tumorigenesis and Metastatic Potential of Breast Cancer Cells via Estrogen Receptor-α36 (ERα36)

Background: ERα36 is present in ERα-negative breast cancer and mediates rapid responses. Results: Estrogen promoted cell survival and increased metastatic factors in breast cancer through membrane ERα36. Conclusion: ERα36 plays a major role in estrogen responses of ERα-negative breast cancers. Significance: Examining the role of ERα36 in ERα-negative breast cancer is essential for understanding the negative effects of estrogen in breast cancer. Protein kinase C (PKC) signaling can be activated rapidly by 17β-estradiol (E2) via nontraditional signaling in ERα-positive MCF7 and ERα-negative HCC38 breast cancer cells and is associated with tumorigenicity. Additionally, E2 has been shown to elicit anti-apoptotic effects in cancer cells counteracting pro-apoptotic effects of chemotherapeutics. Supporting evidence suggests the existence of a membrane-associated ER that differs from the traditional receptors, ERα and ERβ. Our aim was to identify the ER responsible for rapid PKC activation and to evaluate downstream effects, such as proliferation, apoptosis, and metastasis. RT-PCR, Western blot, and immunofluorescence were used to determine the presence of ER splice variants in multiple cell lines. E2 effects on PKC activity were measured with and without ER-blocking antibodies. Cell proliferation was determined by [3H]thymidine incorporation, and cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, (MTT) whereas apoptosis was determined by DNA fragmentation and TUNEL. Quantitative RT-PCR and sandwich ELISA were used to determine the effects on metastatic factors. The role of membrane-dependent signaling in cancer cell invasiveness was examined using an in vitro assay. The results indicate the presence of an ERα splice variant, ERα36, in ERα-positive MCF7 and ERα-negative HCC38 breast cancer cells, which localized to plasma membranes and rapidly activated PKC in response to E2, leading to deleterious effects such as enhancement of proliferation, protection against apoptosis, and enhancement of metastatic factors. These findings propose ERα36 as a novel target for the development of therapies that can prevent progression of breast cancer in the primary tumor as well as during metastasis.

Response of musculoskeletal cells to biomaterials.

&NA; Many of our current therapies are based on information obtained in cell cultures using substrates that have little in common with the substrates the cells will encounter in vivo. To produce materials that are clinically valuable, we must analyze more deeply how musculoskeletal cells interact with the physical features of their environments. An increasing body of information has examined the mechanisms by which osteoblasts interact with their substrate. The underlying substrate, particularly in bone, also has structural features that can alter the mechanical environment experienced by the cells. These structural features modulate the nature of cell attachment and the resulting cell shape, affecting cell proliferation and differentiation. The chemistry, surface energy, and microarchitecture of a material all influence the kinds of proteins that adsorb onto the surface, which in turn affects integrinmediated attachment. Signaling via integrins initiates the transfer of information to the cell about the microenvironment. Cells can differentiate between crystallinities of the same chemistry and distinguish complex differences in surface structure. These differences in the in vitro response correspond to differences in clinical effectiveness. By designing biomaterials that maximally enhance mesenchymal cell attachment, migration, proliferation, and differentiation, the value of these materials for tissue repair will be markedly increased. The goal is to provide materials that are capable of supporting tissue regeneration in vivo, often at sites compromised by infection and loss of structure.

Are calcium phosphate ceramics 'smart' biomaterials?

Autologous bone grafts are the gold standard repair strategy for large defects of bone, but a growing body of evidence suggests that synthetic biomaterials designed to have osteoinductive properties could provide an alternative approach.

Biphasic fusion of the murine posterior frontal suture

Background: Craniosynostosis is the premature fusion of cranial sutures early in development. Mice are commonly used to study the mechanisms driving both normal and pathologic cranial suture development. Despite their frequency of use as a model, the time course of bone formation and mineralization during fusion of mouse posterior frontal suture is not well defined. Methods: To address this, C57Bl/6J mice were euthanized at ages ranging from 6 to 107 days, and the posterior frontal sutures were imaged using micro–computed tomography. Scans were analyzed with an image-processing algorithm that was previously validated with serial histology to quantify both suture fusion and mineral content. The expression profile of genes associated with key developmental time points was examined using real-time polymerase chain reaction in both the bone and the dura. Results: Results demonstrate that the bones of the posterior frontal suture come together during days 10 to 20 and then increase in mineral content and volume between days 21 and 45. The onset of posterior frontal suture fusion was associated with an increase in cartilage-associated genes on day 12. Later mineralization of the suture was associated with an increase in mRNAs for osteoblast differentiation markers, bone morphogenetic proteins, and bone morphogenetic protein inhibitors. Conclusions: Complete analysis fusion posterior frontal suture shows that it occurs in a discontinuous biphasic manner. The first phase is from days 10 to 20 and involves production of cartilage. A second mineralization phase from days 21 to 45 was seen with both the imaging algorithm and changes in gene expression.

Abstract 33P: Rapid Re-Synostosis in Mice is Both Location and Age Dependent

Background: Craniosynostosis is the premature fusion of the cranial sutures and commonly requires complex calvarial reconstruction. In up to 40% of cases, the bones re-fuse resulting in re-synostosis that requires subsequent surgical intervention associated with a high incidence of serious complications. The objective of this study was to determine if the regenerative ability of a murine cranial defect varies with age and location.