Marci D. Jones

Runx2 Protein Expression Utilizes the Runx2 P1 Promoter to Establish Osteoprogenitor Cell Number for Normal Bone Formation

The Runt-related transcription factor, Runx2, is essential for osteogenesis and is controlled by both distal (P1) and proximal (P2) promoters. To understand Runx2 function requires determination of the spatiotemporal activity of P1 and P2 to Runx2 protein production. We generated a mouse model in which the P1-derived transcript was replaced with a lacZ reporter allele, resulting in loss of P1-derived protein while simultaneously allowing discrimination between the activities of the two promoters. Loss of P1-driven expression causes developmental defects with cleidocranial dysplasia-like syndromes that persist in the postnatal skeleton. P1 activity is robust in preosteogenic mesenchyme and at the onset of bone formation but decreases as bone matures. Homozygous Runx2-P1lacZ/lacZ mice have a normal life span but exhibit severe osteopenia and compromised bone repair in adult mice because of osteoblastic defects and not increased osteoclastic resorption. Gene expression profiles of bone, immunohistochemical studies, and ex vivo differentiation using calvarial osteoblasts and marrow stromal cells identified mechanisms for the skeletal phenotype. The findings indicate that P1 promoter activity is necessary for generating a threshold level of Runx2 protein to commit sufficient osteoprogenitor numbers for normal bone formation. P1 promoter function is not compensated via the P2 promoter. However, the P2 transcript with compensatory mechanisms from bone morphogenetic protein (BMP) and Wnt signaling is adequate for mineralization of the bone tissue that does form. We conclude that selective utilization of the P1 and P2 promoters enables the precise spatiotemporal expression of Runx2 necessary for normal skeletogenesis and the maintenance of bone mass in the adult.

A Proteasome Inhibitor, Bortezomib, Inhibits Breast Cancer Growth and Reduces Osteolysis by Downregulating Metastatic Genes

Purpose: The incidence of bone metastasis in advanced breast cancer (BrCa) exceeds 70%. Bortezomib, a proteasome inhibitor used for the treatment of multiple myeloma, also promotes bone formation. We tested the hypothesis that proteasome inhibitors can ameliorate BrCa osteolytic disease. Experimental Design: To address the potentially beneficial effect of bortezomib in reducing tumor growth in the skeleton and counteracting bone osteolysis, human MDA-MB-231 BrCa cells were injected into the tibia of mice to model bone tumor growth for in vivo assessment of treatment regimens before and after tumor growth. Results: Controls exhibited tumor growth, destroying trabecular and cortical bone and invading muscle. Bortezomib treatment initiated following inoculation of tumor cells strikingly reduced tumor growth, restricted tumor cells mainly to the marrow cavity, and almost completely inhibited osteolysis in the bone microenvironment over a 3- to 4-week period as shown by [18F]fluorodeoxyglucose positron emission tomography, micro–computed tomography scanning, radiography, and histology. Thus, proteasome inhibition is effective in killing tumor cells within the bone. Pretreatment with bortezomib for 3 weeks before inoculation of tumor cells was also effective in reducing osteolysis. Our in vitro and in vivo studies indicate that mechanisms by which bortezomib inhibits tumor growth and reduces osteolysis result from inhibited cell proliferation, necrosis, and decreased expression of factors that promote BrCa tumor progression in bone. Conclusion: These findings provide a basis for a novel strategy to treat patients with BrCa osteolytic lesions, and represent an approach for protecting the entire skeleton from metastatic bone disease. Clin Cancer Res; 16(20); 4978–89. ©2010 AACR.

Sonography and Sonoarthrography of the Scapholunate and Lunotriquetral Ligaments and Triangular Fibrocartilage Disk Initial Experience and Correlation With Arthrography and Magnetic Resonance Arthrography

The purpose of this study was to determine the utility of sonography and sonoarthrography in evaluation of dorsal bands of the scapholunate ligament (SLL), lunotriquetral ligament (LTL), and triangular fibrocartilage (TFC) disk in correlation with arthrography and magnetic resonance arthrography (MRA).

Increased Complications in Trapeziectomy With Ligament Reconstruction and Tendon Interposition Compared With Trapeziectomy Alone.

Background: In the treatment of basal joint arthritis of the thumb, recent studies suggest equivalent outcomes with regard to long-term pain, mobility, and strength, in patients undergoing either trapeziectomy alone or trapeziectomy with ligament reconstruction and tendon interposition (LRTI). The goal of this study was to investigate risk factors for complications in carpometacarpal (CMC) arthroplasty. Methods: We conducted a retrospective chart review of 5 surgeons at a single institution performing CMC arthroplasties from November 2006 to November 2012. A total of 200 thumbs in 179 patients underwent simple trapeziectomy with or without LRTI and with or without Kirschner wire stabilization, or a Weilby procedure. The average follow-up was 11.6 months (range = 1-69 months). Data collection included sex, age, history of smoking or diabetes, and any other surgeries performed on the hand at the time of arthroplasty. Furthermore, we collected outcomes involving any adverse events, paying attention to those necessitating reoperation, antibiotics, or those who developed complex regional pain syndrome. Results: Seventy hands had a postoperative complication. Ten of these complications were considered major, defined as requiring antibiotics, reoperation, or other aggressive interventions. On multivariate analysis, risk of total complications was significantly greater only in patients undergoing either trapeziectomy with LRTI or Weilby procedure in comparison with trapeziectomy with K-wire stabilization (odds ratio = 4.30 and 6.73, respectively). Conclusions: Patients undergoing trapeziectomy with LRTI or Weilby had a greater incidence of reported complications when compared with trapeziectomy alone. These results suggest an advantage of simple trapeziectomy; however, further study is warranted.

Self-measured wrist range of motion by wrist-injured and wrist-healthy study participants using a built-in iPhone feature as compared with a universal goniometer

STUDY DESIGN Cross-sectional cohort. INTRODUCTION Smartphone gyroscope and goniometer applications have been shown to be a reliable way to measure wrist ROM when used by researchers or trained staff. If wrist-injured patients could reliably measure their own ROM, rehabilitation efforts could be more effectively tailored. PURPOSE OF THE STUDY To assess agreement of self-measured ROM by wrist-injured and wrist-healthy study participants using a built-in iPhone 5 level feature as compared to researcher-measured ROM using a universal goniometer (UG). METHODS Thirty wrist-healthy and 30 wrist-injured subjects self-measured wrist flexion, extension, supination, and pronation ROM using the built-in preinstalled digital level feature on an iPhone 5. Simultaneously a researcher measured ROM with a UG. RESULTS Average absolute deviation between the self-measured iPhone 5 level feature and researcher-measured UG ROM was less than 2° for all 4 movements individually and combined was found to be 1.6° for both populations. Intraclass correlation coefficient showed high correlation with values over 0.94 and Bland-Altman plots showed very strong agreement. There was no statistical difference in the ability of wrist-injured and healthy patients to self-measure wrist ROM. DISCUSSION Both populations showed very high agreement between their self-measured ROM using the built-in level feature on an iPhone 5 and the researcher-measured ROM using the UG. Both populations were able to use the iPhone self-measurement equally well and the injury status of the subject did not affect the agreement results. CONCLUSION Wrist-healthy and wrist-injured subjects were able to reliably and independently measure ROM using a smartphone level feature.

Regulation of the murine PHEX gene by vitamin D3

Introduction: The mechanism for normal bone mineralization is complex and has not been fully elucidated, however it is known to be influenced by factors such as stress, systemic factors (e.g. estrogen) and local factors such as bone morphogenic proteins and interleukins. Osteomalacia is characterized by defective bone mineralization, with increased unmineralized matrix. The PHEX gene (Phosphate encoding gene with Homologies to Endopeptidases on the X chromosome) is abnormal in X-linked hypophosphatemic rickets (XLH) aka “Phosphate Diabetes.” This manifests as hypophosphatemia, low or inappropriately normal 1,25 (OH)2 vitamin D3 (D3) levels, high serum alkaline phosphatase and osteomalacia. PHEX is mainly expressed in osteoblasts, and is theorized to regulate an osteoblast derived factor termed “phosphatonin” that modulates mineralization of the extracellular matrix. D3 has been shown to downregulate PHEX in primary and cultured mouse osteoblasts. PHEX deficient osteoblasts have an altered response to D3 treatment ; further, D3 decreases PHEX mRNA levels and protein synthesis in normal osteoblast culture, with preliminary evidence indicating that this decrease is at the transcriptional level. The murine PHEX promoter has been previously cloned by our laboratory and its functionality was demonstrated in rat osteoblast-like (UMR-106) cells . Examination of this sequence for the presence of putative cis-acting elements identified multiple binding sites, including those for estrogen and glucocorticoid receptors; a putative binding site for vitamin D receptor was not identified. The present study was undertaken to confirm that D3 regulates PHEX at a transcriptional level both in vivo and in vitro, and to determine the promoter region responsible for this regulation.