Biomedical subjects

Seth C Gamradt

Publications and source records attributed to Seth C Gamradt.

9 recordsLinked to original sources

PubMed2006

Tracking expression of virally mediated BMP-2 in gene therapy for bone repair.

Ex vivo gene therapy using stem cells transduced with viral vectors is a useful method for delivering a therapeutic protein to augment bone repair in animal models. However, the duration of cell-mediated protein production and the fate of the transduced cells are unknown. We constructed an adenoviral vector encoding Myc epitope tagged bone morphogenetic protein (BMP)-2 gene (AdBMP-2). Rat bone marrow cells transduced with this vector produced biologically active BMP-2 protein, which was confirmed by Western blot analysis and alkaline phosphatase assay. Implantation of bone marrow cells infected ex vivo with AdBMP-2 caused orthotopic bone formation in mouse hindlimbs and bony union of critical-sized mouse radial defects. Immunohistochemical analysis revealed that rBMCs expressed Myc epitope-tagged BMP-2 protein for 14 days in vivo and became incorporated in the endochondral fracture callus. This novel adenovirus encoding for epitope-tagged BMP-2 can be used for immunohistochemical tracking of transduced cells in ex vivo gene therapy for bone repair.

Adenoviridae↗

PubMed2005

Overexpression of noggin inhibits BMP-mediated growth of osteolytic prostate cancer lesions.

INTRODUCTION: Although a majority of metastatic prostate cancer lesions are osteoblastic in nature, some are mixed or lytic; and, osteoblastic lesions require osteolytic activity in order to progress. The role of BMPs in the formation of prostate cancer metastases to bone remains unknown. We hypothesized that BMPs influence the development and progression of osteolytic prostate cancer lesions. METHODS: RT-PCR and Western blot analysis were used to determine BMP receptor expression on the osteolytic prostate cancer cell line PC-3. Migration, invasion, and cellular proliferation assays were performed on PC-3 cells to quantify the effects of BMP-2, -4, and -7. In vivo, PC-3 cells were injected alone, with an empty retroviral vector, or with a retroviral vector overexpressing noggin, into the tibias of SCID mice. The animals were followed for 8 weeks, and histologic and radiographic analysis were performed at 2, 4, 6, and 8 weeks. RESULTS: BMP receptors are expressed on PC-3 cells, suggesting that they would be responsive to host BMP secretion. BMP-2, and to a lesser extent, BMP-4, stimulated PC-3 cell migration and invasion in a dose-dependent fashion. Noggin inhibited cellular migration and invasion of BMP-2 and -4 stimulated PC-3 cells. BMP-2 alone stimulated PC-3 cell proliferation, but BMP-4 had no effect. BMP-7 had no effect on proliferation, migration, or invasion. PC-3 cells implanted into SCID mouse tibias formed osteolytic lesions as early as 2 weeks and completely destroyed the proximal tibia by 8 weeks. Overexpression of noggin in PC-3 cells inhibited the expansion of the lesion in vivo. CONCLUSIONS: BMPs influence the formation of the osteolytic prostate cancer metastases, and treatment modalities that inhibit BMP activity may limit the progression of the lytic component of prostate cancer metastases.

Animals↗

PubMed2005

Influence of BMPs on the formation of osteoblastic lesions in metastatic prostate cancer.

UNLABELLED: The purpose of this study was to evaluate the role of BMPs on the formation of metastatic prostate cancer lesions to bone. Our results show that BMPs influence the development and progression of osteoblastic lesions and suggest that therapies that inhibit BMP activity may reduce the formation and progression of osteoblastic lesions. INTRODUCTION: Prostate adenocarcinoma is the leading cause of cancer in North American men. The formation of skeletal metastases affects approximately 70% of patients with advanced disease, and a majority of these patients have osteoblastic lesions. Although BMPs have been found to be expressed in multiple oncogenic cell lines, their role in the formation of metastatic osteoblastic lesions remains uncharacterized. We hypothesized that BMPs influence the development of metastatic osteoblastic lesions associated with prostate cancer. MATERIALS AND METHODS: Western blot analysis and RT-PCR was used to determine BMP receptor expression on osteoblastic prostate cancer cell lines LAPC-4 and LAPC-9. Migration, invasion, and cellular proliferation assays were used to quantify the effects of BMP-2, -4, and -7 on LAPC-4 cells in vitro. LAPC-9 cells alone or transfected with a retrovirus overexpressing noggin were injected into the tibias of SCID mice, and the animals were followed for 8 weeks. Tumor size was determined by radiographs and direct measurement. Histology was performed at the time of death. RESULTS: We determined that BMP receptor mRNA and protein was expressed on osteoblastic prostate cancer cell lines LAPC-4 and LAPC-9. In vitro studies showed that BMP-2 and -7 stimulated cellular migration and invasion of prostate cancer cells in a dose-dependent fashion, although BMP-4 had no effect. Noggin inhibited cellular migration and invasion of BMP-2- and -7-stimulated LAPC-4 cells. LAPC-9 cells implanted into immunodeficient mouse tibias formed an osteoblastic lesion with sclerotic bone at 8 weeks. Formation of osteoblastic lesions was inhibited by overexpression of noggin by prostate cancer cells transduced with a retrovirus containing the cDNA for noggin. CONCLUSIONS: BMPs are critical in the formation of the osteoblastic lesions associated with prostate cancer metastases, and future treatment strategies that inhibit local BMP activity may reduce the formation and progression of osteoblastic lesions.

Animals↗

PubMed2005

The effects of RANK blockade and osteoclast depletion in a model of pure osteoblastic prostate cancer metastasis in bone.

Adenocarcinoma of the prostate exhibits a clear propensity for bone and is associated with the formation of osteoblastic metastases. It has previously been suggested that osteoclast activity may be necessary for the development of these osteoblastic metastases based on data from lytic and mixed lytic-blastic tumors. Here we investigate the effects of complete in vivo osteoclast depletion via the blockade of receptor activator of NF:kappaB (RANK) on the establishment and progression of purely osteoblastic (LAPC-9 cells) bone lesions induced by human prostate cancer cells using a SCID mouse intratibial injection model. The subcutaneous administration of the RANK antagonist (15 mg/kg) RANK:Fc did not prevent the formation of purely osteoblastic lesions, indicating that osteoclasts may not be essential to the initial development of osteoblastic metastases. However, RANK:Fc protein appeared to inhibit the progression of established osteoblastic lesions, suggesting that osteoclasts may be involved in the subsequent growth of these tumors once they are already present. In contrast, RANK:Fc treatment effectively blocked the establishment and progression of purely osteolytic lesions formed by PC-3 cells, which served as a positive control. These results indicate that in vivo RANK blockade may not be effective for the prevention of osteoblastic metastasis but may potentially represent a novel therapy that limits the growth of established metastatic CaP lesions in bone.

Animals↗

PubMed2004

Genetic modification of stem cells to enhance bone repair.

Orthopaedic surgeons are often faced with difficult bone loss problems. Conventional bone grafting is usually accomplished with autogenous iliac crest bone graft that provides osteogenic cells, osteoinductive growth factors, and an osteoconductive matrix. Cadaveric bone allograft and bone graft substitutes are inferior to autogenous bone graft because they fail to supply osteogenic cells or a significant amount of osteoinductive growth factors. Recombinant growth factors such as bone morphogenetic protein-2 and osteogenic protein-1 are currently in clinical use but these proteins require supraphysiologic dosing and considerable expense while failing to provide a sustained osteoinductive signal at the implantation site. Mesenchymal stem cells capable of differentiating into mesodermal tissues have been isolated and expanded in culture from several different sources including bone marrow, adipose tissue, and muscle. In the presence of appropriate growth factors these cells can differentiate into osteoblast lineage cells that will form bone in vitro and in vivo. Recent attention has focused on genetic modification of mesenchymal stem cells to both produce and respond to osteogenic growth factors with the goal of developing a tissue engineering strategy for bone repair. This review examines the current potential and limitations of these cellular systems for bone repair.

Animals↗

PubMed2003

Perioperative complications of threaded cylindrical lumbar interbody fusion devices: anterior versus posterior approach.

Few data are available to evaluate approach-related differences in perioperative complications with lumbar interbody fusion devices. Complications occurring in the intraoperative and immediate postoperative period were identified and categorized for 31 consecutive posterior lumbar interbody fusions (PLIFs) and 88 consecutive anterior lumbar interbody fusions (ALIFs). In this study, all lumbar interbody fusions were conducted with threaded cylindrical devices as stand-alone internal fixation devices. Multivariate analysis was used to account for potential covariates and identify factors associated with an increased complication risk. Twenty-two percent of the patients had a perioperative complication. The relative risk of having a perioperative complication was 4.75 times higher for the PLIF group. All intraoperative complications occurred in the PLIF group. The relative risk of having a major postoperative complication was 6.8 times higher in the PLIF group than the ALIF group. Anterior approached patients tended to have visceral (ileus, 6%) and vascular (deep venous thrombosis, 2%) complications. In the posterior group, complications were neurologic and dura related (pseudomeningocele, 16%; epidural hematoma, 3%) and occurred most frequently in patients that had had previous posterior lumbar surgery (31% with major complication).

Adult↗

PubMed2003

Bone graft for revision hip arthroplasty: biology and future applications.

Revision total hip arthroplasty often presents surgeons with difficult bone loss problems. The selection of an appropriate bone graft is influenced by the size of the bone defect, the location, the biology of the bone graft site, and whether the graft is required for structural support. Autogenous bone graft remains the gold standard bone graft material but there only is a limited amount available and there is morbidity associated with the harvesting of these grafts. The most frequently used bone graft materials include autogenous iliac crest bone graft, cancellous allograft chips, demineralized bone matrix, and bulk structural allografts (femoral head, distal or proximal femoral allograft, whole acetabuli, and femoral strut grafts). It often is difficult to determine on plain radiographs whether nonstructural grafts actually incorporate into the host bone. Recently, attention has focused on the use of new materials for bone grafting including: new demineralized bone matrices, ceramics, autologous platelet concentrates, recombinant proteins, and stem cells. The purpose of this review was to assess the biologic potential of these nonstructural grafts in revision hip arthroplasty and their limitations. Are these agents actually incorporating into host bone? Future bone graft options, including tissue engineering and gene therapy will be discussed briefly.

Arthroplasty, Replacement, Hip↗

PubMedDate not supplied

Lumbar disc arthroplasty.

BACKGROUND CONTEXT: Painful lumbar disc degeneration is one of the most common ailments treated by spine surgeons. Currently, early disc disease and herniation are often treated with microdiscectomy. Late disc degeneration is usually treated with arthrodesis. With the advent of new technology and techniques in lumbar disc arthroplasty, interest in preserving spinal motion at degenerated motion segments has increased. The goals of lumbar disc arthroplasty are to provide long-term pain relief at the degenerated disc level, to restore disc height to protect neural elements and to preserve motion to prevent posterior facet arthropathy and adjacent segment disease. PURPOSE: The purpose of this review is to examine the anatomy and biomechanics of the lumbar motion segment to determine the features that successful disc arthroplasty prosthesis must possess. In addition, the early clinical results of three prostheses currently being used in humans are reviewed. STUDY DESIGN/SETTING: Review of the literature. METHODS: A systematic review of Medline for articles related to lumbar disc arthroplasty was conducted up to and including journal articles published in August 2003. In addition, the abstracts from the annual meetings of the North American Spine Society and Scoliosis Research Society from 1998 to 2003 were searched. The literature was then reviewed and summarized. RESULTS/CONCLUSIONS: Short-term results of lumbar disc arthroplasty as measured by pain relief and disability are good in some studies. Implants are relatively safe in the short term, and with newer designs complications are usually related to the surgical approach rather than early implant failure. Recovery times appear to be shorter than arthrodesis. Despite the relatively good early clinical results of these devices, questions remain about the long-term efficacy in pain relief and maintenance of motion, the results of randomized comparative trials with fusion and the life span of the devices. In addition, late sequelae and revision options are unknown. Current indications for lumbar disc arthroplasty are in the setting of a Food and Drug Administration trial in young, nonosteoporotic patients with one or two level symptomatic disc degeneration without severe facet arthropathy, segmental instability or neural element compression requiring a posterior decompression.

Arthroplasty, Replacement↗

PubMedDate not supplied

The effect of cyclooxygenase-2 (COX-2) inhibition on human prostate cancer induced osteoblastic and osteolytic lesions in bone.

BACKGROUND: The mechanism of bone formation by osteoblastic prostate cancer metastases is not well defined. Using knockout mice, it has been demonstrated that prostaglandins produced by COX-2 are critical for fracture repair. Therefore, our aim was to determine if COX-2 plays a role in the bone formation in osteoblastic prostate cancer metastases in bone. MATERIALS AND METHODS: We assessed the influence of pharmacologic COX-2 inhibition in a SCID mouse intratibial injection model of bone metastasis using two human prostate cancer cell lines that produce either osteoblastic lesions (LAPC-9) or osteolytic lesions (PC-3, negative control). SC-58236, a COX-2 specific inhibitor, was used at a dose of 3 mg/Kg intraperitoneally 3 times per week in the Treatment groups for 8 weeks until sacrifice. RESULTS: Western blot for COX-2 demonstrated that LAPC-9 cells expressed high levels of COX-2 while PC-3 cells did not. Treatment with SC-58236 significantly reduced the size of osteoblastic lesions after LAPC-9 injection based on both radiographic and histomorphometric criteria compared to the control group. In contrast, large osteolytic lesions were seen in both control and SC-58236 treated animals after PC-3 cell injections. The results of this study indicate that COX-2 inhibition can decrease the size of osteoblastic lesions produced by LAPC-9, a human prostate cancer cell line that expresses high levels of COX-2. This treatment had no effect on the osteolytic activity of PC-3 cells. CONCLUSION: These findings suggest that the progression of osteoblastic metastases induced by human prostate cancer cells may be limited by COX-2 inhibitors.

Animals↗