David Hughes - Academia.edu (original) (raw)
Papers by David Hughes
Tissue Engineering, 2007
Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone... more Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone growth. To produce a bone-inductive material such as hypertrophic cartilage for clinical use, we have conditionally immortalized hypertrophic chondrocytic cells from human femur and expanded them in vitro through more than 145 divisions. The clonal cell lines generated by this process consistently express signals that induce both rat and human marrow cells to differentiate in vitro into osteoblastic cells. Further, implantation of the cell-free extracellular matrix from the immortalized chondrocytic cells causes vascularized bone to form in vivo in bony defects, but not in ectopic sites such as skeletal muscle. This study shows that molecular techniques can be used to generate bespoke human cell lines for bone tissue engineering. It also demonstrates that matrix material generated from human immortalized hypertrophic chondrocytic cells may provide an abundant, efficacious, and safer alternative to bone autograft--the currently preferred material for fracture repair.
Journal of Experimental Medicine, 2000
Branch points and flexures in the high pressure arterial system have long been recognized as site... more Branch points and flexures in the high pressure arterial system have long been recognized as sites of unusually high turbulence and consequent stress in humans are foci for atherosclerotic lesions. We show that mice that are homozygous for a null mutation in the gene encoding an endogenous antiinflammatory cytokine, interleukin 1 receptor antagonist (IL-1ra), develop lethal arterial inflammation involving branch points and flexures of the aorta and its primary and secondary branches. We observe massive transmural infiltration of neutrophils, macrophages, and CD4 ϩ T cells. Animals appear to die from vessel wall collapse, stenosis, and organ infarction or from hemorrhage from ruptured aneurysms. Heterozygotes do not die from arteritis within a year of birth but do develop small lesions, which suggests that a reduced level of IL-1ra is insufficient to fully control inflammation in arteries. Our results demonstrate a surprisingly specific role for IL-1ra in the control of spontaneous inflammation in constitutively stressed artery walls, suggesting that expression of IL-1 is likely to have a significant role in signaling artery wall damage.
Journal of Bone and Mineral Research, 2009
Bisphosphonates inhibit bone resorption and are therapeutically effective in diseases of increase... more Bisphosphonates inhibit bone resorption and are therapeutically effective in diseases of increased bone turnover, such as Paget's disease and hypercalcemia of malignancy. The mechanisms by which they act remain unclear. Proposed mechanisms include inhibition of osteoclast formation from precursors and inhibitory or toxic effects on mature osteoclasts. We have developed a new in vitro model to study osteoclast survival and in this paper present in vitro and in vivo evidence that may explain both the observed reduction in osteoclast numbers and in bone resorption by mature osteoclasts, namely that bisphosphonates induce programmed cell death (apoptosis). Three bisphosphonates (risedronate, pamidronate, and clodronate) caused a 4-to 24-fold increase in the proportion of osteoclasts showing the characteristic morphology of apoptosis in vitro. This observation was confirmed in vivo in normal mice, in mice with increased bone resorption, and in nude mice with osteolytic cancer metastases, with similar-fold increases to those observed in vitro. Of the three compounds, risedronate, the most potent inhibitor of bone resorption in vivo, was the strongest inducer of osteoclast apoptosis in vitro. Osteoclast apoptosis may therefore be a major mechanism whereby bisphosphonates reduce osteoclast numbers and activity, and induction of apoptosis could be a therapeutic goal for new antiosteoclast drugs.
Journal of Bone and Mineral Research, 2009
bone remodeling requires the con-L tinual production of relatively short-lived cells, and for bot... more bone remodeling requires the con-L tinual production of relatively short-lived cells, and for both processes manipulation of cell production is more important than manipulation of differentiated cell function, and regulates supply in relation to demand.'" In the adult skeleton, the demand for osteoblasts is created by bone resorption, but the demand for osteoclasts is governed by the purposes of bone remodeling. Most therapeutic agents used for the prevention and treatment of osteoporosis are referred to as inhibitors of bone resorption, but this vague term obscures the important distinction between inhibition of the recruitment of new osteoclasts and inhibition of the function of existing osteoclasts.'" Although bisphosphonates as a class have been studied for more than 25 years, their mode of action as inhibitors of bone resorption is still unclear and is probably different for different members of the class.'" In the intact organism, tetracycline-based histomorphometric studies indicate a major long-term effect of bisphosphonate administration to reduce the rate at which new cycles of bone remodeling are initiated, or activation frequency,(4,') an expression of reduced osteoclast recruitment and the basis for the reduction in whole body bone turnover shown by biochemical But in vitro studies have demonstrated powerful inhibitory effects of bisphosphonates on the function of existing osteoclasts'3.x-"'' with minor or conflicting effects on osteoc I ast recruit men t .'-3, ' I. ') *Presented in poster form at the XI1 International Conference on Calcium Regulatory Hormones (Parfitt AM, Mundy GR, Roodman GD, Hughes DE, Boycc B I995 A new model for the effects of bisphosphonates on bone remodeling. XIIth International Conference on Calcium Regulating Hormones. Melbourne, Australia. Bone 16 (Suppl I):216S).
Tissue Engineering, 2007
Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone... more Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone growth. To produce a bone-inductive material such as hypertrophic cartilage for clinical use, we have conditionally immortalized hypertrophic chondrocytic cells from human femur and expanded them in vitro through more than 145 divisions. The clonal cell lines generated by this process consistently express signals that induce both rat and human marrow cells to differentiate in vitro into osteoblastic cells. Further, implantation of the cell-free extracellular matrix from the immortalized chondrocytic cells causes vascularized bone to form in vivo in bony defects, but not in ectopic sites such as skeletal muscle. This study shows that molecular techniques can be used to generate bespoke human cell lines for bone tissue engineering. It also demonstrates that matrix material generated from human immortalized hypertrophic chondrocytic cells may provide an abundant, efficacious, and safer alternative to bone autograft--the currently preferred material for fracture repair.
The Journal of Foot and Ankle Surgery, 2011
Although well reported in the literature, fractures of the os peroneum are uncommon and can be di... more Although well reported in the literature, fractures of the os peroneum are uncommon and can be difficult to differentiate from symptomatic multipartite sesamoids. The location of the os peroneum within the tendon of peroneus longus can make it difficult to excise without compromising or sacrificing the tendon, and, subsequently, necessitating reconstruction or tenodesis to peroneus brevis. In this article, we describe the case of an adult female who presented with a fractured os peroneum that radiographically appeared bipartite, and necessitated excision with reconstruction of the peroneus longus. In retrospect, with the benefit of histology and careful review of the preoperative magnetic resonance image scans, simple excision of the medial fragment of the ossicle may have obviated the need for tendon reconstruction by maintaining the integrity of the peroneus longus tendon.
Journal of Bone and Mineral Research, 2009
Recombinant human interleukin-6 (1L-6) was assessed for its ability to stimulate bone resorption ... more Recombinant human interleukin-6 (1L-6) was assessed for its ability to stimulate bone resorption in prelabeled mouse calvariae in vitro. IL-6 had no effect on bone resorption at concentrations ranging from 300 to 10,000 U/ml (3-1000 pg/ml). Neither the presence of indomethacin nor prolonged incubation periods (96 h) affected this result. IL-6 did not affect resorption stimulated by human recombinant IL-ltu (rIL-la) but inhibited resorption stimulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D, [1,25-(OH),D1]. rIL-la, PTH, and 1,25-(OH),D, induced IL-6 release by calvariae. We conclude from these studies that IL-6 does not stimulate bone resorption in neonatal mouse calvariae. However, it may act as a locally produced inhibitor and therefore a paracrine regulator of bone resorption induced by osteotropic hormones. IL-6 could also function as a long-range stimulator of systemic reactions and acute-phase responses to local inflammatory and neoplastic lesions in bone.
British Journal of Haematology, 2008
Bone, 1995
In this short review, some regulatory mechanisms that are involved in the control of normal bone ... more In this short review, some regulatory mechanisms that are involved in the control of normal bone formation are proposed, based on several in vivo and in vitro models our group has utilized recently to study osteoblast differentiation and mineralized bone matrix formation. Of course, these proposals must be assessed in the light of the limitations of the models, which probably represent a simplification of the complex and different ways in which normal mammalian bone is formed at different sites. Nevertheless, it is likely that the same general types of control mechanisms are active in each of the different types of bone formation. In adult humans, bone formation predominantly occurs by remodeling, the process by which bone which has recently been resorbed by osteoclasts is replaced by teams of osteoblasts. Other types of bone formation such as endochondral bone formation and appositional bone formation are also important, particularly during growth and adolescence. The end results of each of these processes are the same, namely a complex mineralized proteinaceous bone matrix. These processes are modulated by systemic hormonal influences, which are particularly important with respect to pituitary hormones and sex steroids during growth and adolescence, and by local cellular microenvironmental differences. The former will not be discussed here. Rather, we will concentrate on the local events and factors which are likely involved in the bone formation process occurring during normal bone remodeling.
Arthritis Research & Therapy, 2010
The Lancet Oncology, 2010
Tissue Engineering, 2007
Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone... more Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone growth. To produce a bone-inductive material such as hypertrophic cartilage for clinical use, we have conditionally immortalized hypertrophic chondrocytic cells from human femur and expanded them in vitro through more than 145 divisions. The clonal cell lines generated by this process consistently express signals that induce both rat and human marrow cells to differentiate in vitro into osteoblastic cells. Further, implantation of the cell-free extracellular matrix from the immortalized chondrocytic cells causes vascularized bone to form in vivo in bony defects, but not in ectopic sites such as skeletal muscle. This study shows that molecular techniques can be used to generate bespoke human cell lines for bone tissue engineering. It also demonstrates that matrix material generated from human immortalized hypertrophic chondrocytic cells may provide an abundant, efficacious, and safer alternative to bone autograft--the currently preferred material for fracture repair.
Journal of Experimental Medicine, 2000
Branch points and flexures in the high pressure arterial system have long been recognized as site... more Branch points and flexures in the high pressure arterial system have long been recognized as sites of unusually high turbulence and consequent stress in humans are foci for atherosclerotic lesions. We show that mice that are homozygous for a null mutation in the gene encoding an endogenous antiinflammatory cytokine, interleukin 1 receptor antagonist (IL-1ra), develop lethal arterial inflammation involving branch points and flexures of the aorta and its primary and secondary branches. We observe massive transmural infiltration of neutrophils, macrophages, and CD4 ϩ T cells. Animals appear to die from vessel wall collapse, stenosis, and organ infarction or from hemorrhage from ruptured aneurysms. Heterozygotes do not die from arteritis within a year of birth but do develop small lesions, which suggests that a reduced level of IL-1ra is insufficient to fully control inflammation in arteries. Our results demonstrate a surprisingly specific role for IL-1ra in the control of spontaneous inflammation in constitutively stressed artery walls, suggesting that expression of IL-1 is likely to have a significant role in signaling artery wall damage.
Journal of Bone and Mineral Research, 2009
Bisphosphonates inhibit bone resorption and are therapeutically effective in diseases of increase... more Bisphosphonates inhibit bone resorption and are therapeutically effective in diseases of increased bone turnover, such as Paget's disease and hypercalcemia of malignancy. The mechanisms by which they act remain unclear. Proposed mechanisms include inhibition of osteoclast formation from precursors and inhibitory or toxic effects on mature osteoclasts. We have developed a new in vitro model to study osteoclast survival and in this paper present in vitro and in vivo evidence that may explain both the observed reduction in osteoclast numbers and in bone resorption by mature osteoclasts, namely that bisphosphonates induce programmed cell death (apoptosis). Three bisphosphonates (risedronate, pamidronate, and clodronate) caused a 4-to 24-fold increase in the proportion of osteoclasts showing the characteristic morphology of apoptosis in vitro. This observation was confirmed in vivo in normal mice, in mice with increased bone resorption, and in nude mice with osteolytic cancer metastases, with similar-fold increases to those observed in vitro. Of the three compounds, risedronate, the most potent inhibitor of bone resorption in vivo, was the strongest inducer of osteoclast apoptosis in vitro. Osteoclast apoptosis may therefore be a major mechanism whereby bisphosphonates reduce osteoclast numbers and activity, and induction of apoptosis could be a therapeutic goal for new antiosteoclast drugs.
Journal of Bone and Mineral Research, 2009
bone remodeling requires the con-L tinual production of relatively short-lived cells, and for bot... more bone remodeling requires the con-L tinual production of relatively short-lived cells, and for both processes manipulation of cell production is more important than manipulation of differentiated cell function, and regulates supply in relation to demand.'" In the adult skeleton, the demand for osteoblasts is created by bone resorption, but the demand for osteoclasts is governed by the purposes of bone remodeling. Most therapeutic agents used for the prevention and treatment of osteoporosis are referred to as inhibitors of bone resorption, but this vague term obscures the important distinction between inhibition of the recruitment of new osteoclasts and inhibition of the function of existing osteoclasts.'" Although bisphosphonates as a class have been studied for more than 25 years, their mode of action as inhibitors of bone resorption is still unclear and is probably different for different members of the class.'" In the intact organism, tetracycline-based histomorphometric studies indicate a major long-term effect of bisphosphonate administration to reduce the rate at which new cycles of bone remodeling are initiated, or activation frequency,(4,') an expression of reduced osteoclast recruitment and the basis for the reduction in whole body bone turnover shown by biochemical But in vitro studies have demonstrated powerful inhibitory effects of bisphosphonates on the function of existing osteoclasts'3.x-"'' with minor or conflicting effects on osteoc I ast recruit men t .'-3, ' I. ') *Presented in poster form at the XI1 International Conference on Calcium Regulatory Hormones (Parfitt AM, Mundy GR, Roodman GD, Hughes DE, Boycc B I995 A new model for the effects of bisphosphonates on bone remodeling. XIIth International Conference on Calcium Regulating Hormones. Melbourne, Australia. Bone 16 (Suppl I):216S).
Tissue Engineering, 2007
Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone... more Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone growth. To produce a bone-inductive material such as hypertrophic cartilage for clinical use, we have conditionally immortalized hypertrophic chondrocytic cells from human femur and expanded them in vitro through more than 145 divisions. The clonal cell lines generated by this process consistently express signals that induce both rat and human marrow cells to differentiate in vitro into osteoblastic cells. Further, implantation of the cell-free extracellular matrix from the immortalized chondrocytic cells causes vascularized bone to form in vivo in bony defects, but not in ectopic sites such as skeletal muscle. This study shows that molecular techniques can be used to generate bespoke human cell lines for bone tissue engineering. It also demonstrates that matrix material generated from human immortalized hypertrophic chondrocytic cells may provide an abundant, efficacious, and safer alternative to bone autograft--the currently preferred material for fracture repair.
The Journal of Foot and Ankle Surgery, 2011
Although well reported in the literature, fractures of the os peroneum are uncommon and can be di... more Although well reported in the literature, fractures of the os peroneum are uncommon and can be difficult to differentiate from symptomatic multipartite sesamoids. The location of the os peroneum within the tendon of peroneus longus can make it difficult to excise without compromising or sacrificing the tendon, and, subsequently, necessitating reconstruction or tenodesis to peroneus brevis. In this article, we describe the case of an adult female who presented with a fractured os peroneum that radiographically appeared bipartite, and necessitated excision with reconstruction of the peroneus longus. In retrospect, with the benefit of histology and careful review of the preoperative magnetic resonance image scans, simple excision of the medial fragment of the ossicle may have obviated the need for tendon reconstruction by maintaining the integrity of the peroneus longus tendon.
Journal of Bone and Mineral Research, 2009
Recombinant human interleukin-6 (1L-6) was assessed for its ability to stimulate bone resorption ... more Recombinant human interleukin-6 (1L-6) was assessed for its ability to stimulate bone resorption in prelabeled mouse calvariae in vitro. IL-6 had no effect on bone resorption at concentrations ranging from 300 to 10,000 U/ml (3-1000 pg/ml). Neither the presence of indomethacin nor prolonged incubation periods (96 h) affected this result. IL-6 did not affect resorption stimulated by human recombinant IL-ltu (rIL-la) but inhibited resorption stimulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D, [1,25-(OH),D1]. rIL-la, PTH, and 1,25-(OH),D, induced IL-6 release by calvariae. We conclude from these studies that IL-6 does not stimulate bone resorption in neonatal mouse calvariae. However, it may act as a locally produced inhibitor and therefore a paracrine regulator of bone resorption induced by osteotropic hormones. IL-6 could also function as a long-range stimulator of systemic reactions and acute-phase responses to local inflammatory and neoplastic lesions in bone.
British Journal of Haematology, 2008
Bone, 1995
In this short review, some regulatory mechanisms that are involved in the control of normal bone ... more In this short review, some regulatory mechanisms that are involved in the control of normal bone formation are proposed, based on several in vivo and in vitro models our group has utilized recently to study osteoblast differentiation and mineralized bone matrix formation. Of course, these proposals must be assessed in the light of the limitations of the models, which probably represent a simplification of the complex and different ways in which normal mammalian bone is formed at different sites. Nevertheless, it is likely that the same general types of control mechanisms are active in each of the different types of bone formation. In adult humans, bone formation predominantly occurs by remodeling, the process by which bone which has recently been resorbed by osteoclasts is replaced by teams of osteoblasts. Other types of bone formation such as endochondral bone formation and appositional bone formation are also important, particularly during growth and adolescence. The end results of each of these processes are the same, namely a complex mineralized proteinaceous bone matrix. These processes are modulated by systemic hormonal influences, which are particularly important with respect to pituitary hormones and sex steroids during growth and adolescence, and by local cellular microenvironmental differences. The former will not be discussed here. Rather, we will concentrate on the local events and factors which are likely involved in the bone formation process occurring during normal bone remodeling.
Arthritis Research & Therapy, 2010
The Lancet Oncology, 2010