Higher Osteoblastic Activity Research Articles

Synthesis and antiosteoclast activity of Di(1-oxo/thioxoperhydro-1λ5-[1,3,2] diazaphospholo [1,5-a]pyridine-1-yl) (4-substituted phenyl) boronates

A new family of di(1-oxo/thioxoper-hydro-1λ5-[1,3,2]diazaphospholo[1,5-a]pyridine-1-yl)(4-substituted phenyl) boronates (4a–j) has been synthesized in a two-step process. A reaction of (±)-piperidin-2-yl-methanamine (1) phosphoryl/phosphorothioyl chloride in the presence of triethylamine in dry tetrahydrofuran formed the intermediate monochloride (2), which on condensation with p-substituted phenylboronic acids (3a–j) afforded the titled compounds (4a–j). They were characterized by elemental, IR, 1H, 13C, 31P NMR, and mass spectral analyses. All these compounds showed moderate to high antiosteoclast and osteoblast activity. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:247–253, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21010

Human Extramedullary Bone and Bone Marrow in Mice: First In Vivo Model of a Genetically Controlled Hematopoietic Environment

Abstract 1323The importance of the tumor microenvironment for cancer development, progression and resistance to treatment has recently been recognized. Our group was first to report the contribution of bone marrow (BM) derived mesenchymal stromal cells (MSCs) for tumor development and metastasis. BM is also the dynamic microenvironment (niche) for normal and malignant hematopoietic stem cells (HSC) with high local concentrations of growth factors, chemokines and cytokines. The maintenance of HSCs quiescence and normal hematopoiesis require complex bidirectional interactions between the BM niches and HSCs. Accumulating evidence has shown that the BM microenvironment also plays a pivotal role in the pathophysiology and propagation of leukemia. Leukemia cells undergo spontaneous apoptosis once they are removed from the in vivo microenvironment and placed in suspension cultures without supportive stroma. The understanding of the interactions between leukemic cells and their BM niche is also critically important for leukemia therapy. We here describe a novel artificial bone and bone marrow model mimicking the human hematopoietic microenvironment by using human BM derived MSCs and endothelial colony-forming cells (ECFCs). MSCs and ECFCs were isolated from heparinized human bone marrow or peripheral blood through an initial adhesion step, grown in specific media and then subcutaneously injected into the flanks of the NOD/SCID/IL-2r-gammanull mice, where they developed into bone-like tissues with high osteoblast activity after 10 weeks (Figure 1). Histochemical stains confirmed the bone structures and also showed that these artificial bones contained typical bone marrow cavities constituting a robust hematopoietic environment. In vivo imaging with Osteosense confirmed the presence of hydroxylapatite, and luciferase imaging of firefly luciferase labeled human leukemic cells demonstrated the engraftment of MOLM13/Luc/GFP leukemic cells in the extramedullary BM sites. The extramedullary BM was markedly hypoxic, as shown by Pimonidazole staining, another critical feature of the BM microenvironment. Factors critical for MSC to support the normal and leukemic hematopoiesis are largely unknown and cannot be studied since human MSC do not engraft reliably in xenograft models. We therefore investigated the possibility of genetically modifying MSC in this system and found a significant reduction (50 ± 6%, p<0.001) in MOLM13 cell engraftment in extramedullary BM generated with HIF1-alpha knockdown MSCs (1449 ± 194 cells/mm2), compared to vector controls (3037 ± 496 cells/mm2). This finding indicates that the HIF1-alpha expression in stromal cells is a critical component for the engraftment of leukemic cells in the physiologically hypoxic BM microenvironment. These results, for the first time, establish an in vivo bone and bone marrow model with a genetically controlled human microenvironment. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Novel Natural Transdermal Otoliths/Collagen/Bacterial Cellulose Patch for Osteoporosis Treatment

In the present work, we report the novel natural transdermal otoliths/collagen/bacterial cellulose patch for osteoporosis treatment. This biomaterial is an osteoinductor, or be, stimulates the bone regeneration, enabling bigger migration of the cells for formation of the bone fabric. Otolith is a typical biomaterial that is composed of calcium carbonate and organic matrix. Otoliths are calcareous concrescences present in the inner ear of fishes. Since they are rich in minerals, they are considered essential to the bone mineralization process on a protein matrix (otolin). The objective in this study was to analyze the regeneration capacity of bone defects treated with otoliths network preparation. Collagen and nano-otoliths influences in bacterial cellulose was analyzed using transmission infrared spectroscopy (FTIR). In vivo analysis shows bone surface tissue with high regularity, higher osteoblast activity, and osteo-reabsorption activities areas. These results indicated that the transdermal permeation of otollith using this patch system was sufficient for the treatment of bone diseases. These findings indicate that our novel transdermal delivery system for otolith/collagen/bacterial cellulose is a promising approach to improve compliance and quality of life of patients in the treatment of bone diseases.

First Otoliths/Collagen/Bacterial Cellulose Nanocomposites as a Potential Scaffold for Bone Tissue Regeneration

In the present work, we report the first bionanocomposite material formed by otoliths/ collagen/ bacterial cellulose (BC) networks (OCBC). This biomaterial is an osteoinductor or be, stimulates the bone regeneration, enabling bigger migration of the cells for formation of the bone tissue regeneration mainly because nanotolith are rich in minerals considered essential to the bone mineralization process on a protein matrix (otolin). The objective in this study was to analyze the regeneration capacity of bone defects treated with this bionanocomposite. Histological experiments shows bone tissue formation with high regularity, higher osteoblast activity and osteo-reabsorption activities areas. The results suggest the potential for this new biomaterial as a scaffold for bone tissue regeneration.

Enhanced osteoblastic activity and bone regeneration using surface‐modified porous bioactive glass scaffolds

The potential use as a bone substitute material of a three-dimensional bioactive glass fiber scaffold composed of Na(2)O-K(2)O-MgO-CaO-B(2)O(3)-P(2)O(5)-SiO(2) (BG1) was investigated in this work. Scaffolds were pre-treated with simulated body fluid (SBF) to promote the formation of two different bone-like apatite layers on their surfaces. The topography and roughness of the deposited layers were assessed by scanning electron microscopy (SEM), while the chemical composition and structure using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, respectively. Based on surface analysis, the bioactive glass surfaces were ranked from smoothest to roughest: 0 SBF (untreated), 1x SBF and 2x SBF. A calcium-deficient carbonated hydroxyapatite (HCA) layer was present on both SBF-treated scaffolds, with higher number and larger bone-like apatite nodule formation in the 2x SBF case. MC3T3-E1 preosteoblasts showed a more flattened morphology and higher cell proliferation on the nontreated scaffolds; whereas, cells were more elongated and had higher osteoblastic activity on SBF-treated samples. In vivo results in a rabbit calvarial bone defect model showed enhanced bone formation with SBF pretreated scaffolds, compared with untreated ones, commercially available Perioglass particles and empty defects. Our findings demonstrate that the formation of a rough HCA layer on bioactive glass porous scaffolds enhanced preosteoblast maturation in vitro, as well as bone formation in vivo.

Histomorphometric comparison between continuous and discontinuous distraction osteogenesis

Experimental research on optimising the distraction protocol has been performed extensively in the past. However, relatively little research has been done on the rhythm of distraction. Findings in the orthopaedic literature showed that the outcome of distraction osteogenesis (DO) is positively influenced by increasing the rhythm of distraction. The aim of this study is to quantitatively compare continuous with discontinuous rhythms of distraction in rabbits. Tissue blocks of regenerated bone were harvested from thirty-eight young adult female New-Zealand White rabbits. After a latency period of three days, rabbits were subjected for eleven days to either single daily activation of the distractor at a rate of 0.9 mm/d, or triple daily activation at a rate of 0.9 mm/d, or continuous activation at a rate of 0.9 mm/d. After three weeks of consolidation, bone regenerates were analysed using histomorphometry. The continuous DO group showed significantly (p<.01) more regenerate bone volume in the central part of the regenerate than the discontinuous DO groups. Higher osteoblastic activity was seen, as well as more blood vessels (p<.05). Bone volume and the number of blood vessels correlated significantly in the central part of the regenerate (p<.05). Also, the early mineral apposition rate (MAR) was higher than the late MAR (p<.05). Continuous DO significantly accelerates bone formation when compared with discontinuous DO.

32 wk old C3H/HeJ mice actively respond to mechanical loading

Numerous studies indicate that C3H/HeJ (C3H) mice are mildly responsive to mechanical loading compared to C57BL/6J (C57) mice. Guided by data indicating high baseline periosteal osteoblast activity in 16 wk C3H mice, we speculated that simply allowing the C3H mice to age until basal periosteal bone formation was equivalent to that of 16 wk C57 mice would restore mechanoresponsiveness in C3H mice. We tested this hypothesis by subjecting the right tibiae of 32 wk old C3H mice and 16 wk old C57 mice to low magnitude rest-inserted loading (peak strain: 1235 μɛ) and then exposing the right tibiae of 32 wk C3H mice to low (1085 μɛ) or moderate (1875 μɛ) magnitude cyclic loading. The osteoblastic response to loading on the endocortical and periosteal surfaces was evaluated via dynamic histomorphometry. At 32 wk of age, C3H mice responded to low magnitude rest-inserted loading with significantly elevated periosteal mineralizing surface, mineral apposition rate and bone formation compared to unloaded contralateral bones. Surprisingly, the periosteal bone formation induced by low magnitude rest-inserted loading in C3H mice exceeded that induced in 16 wk C57 mice. At 32 wk of age, C3H mice also demonstrated an elevated response to increased magnitudes of cyclic loading. We conclude that a high level of basal osteoblast function in 16 wk C3H mice appears to overwhelm the ability of the tissue to respond to an otherwise anabolic mechanical loading stimulus. However, when basal surface osteoblast activity is equivalent to that of 16 wk C57 mice, C3H mice demonstrate a clear ability to respond to either rest-inserted or cyclic loading.

Efeitos da radioterapia no tecido ósseo

OBJETIVO: Avaliar os efeitos da radioterapia e a acurácia da mensuração do nível de cinza do tecido ósseo em imagens radiográficas. MATERIAIS E MÉTODOS: Quatro ratos Wistar foram submetidos a radioterapia externa (dose única de 3.000 cGy) em uma área de 2 cm × 2 cm na perna direita. Os animais foram sacrificados seis semanas após a radioterapia, e tanto as pernas irradiadas quanto as contralaterais (não-irradiadas) foram avaliadas na sua espessura, radiografadas de forma padronizada e processadas histologicamente (hematoxilina-eosina e picrossírius). As radiografias foram digitalizadas e a média dos níveis de cinza foi mensurada no programa Image Tool®. RESULTADOS: A espessura do fêmur foi maior na perna contralateral do que na irradiada (p &lt; 0,05). Radiograficamente, observou-se maior quantidade de tecido ósseo na perna contralateral em relação à perna irradiada, porém sem diferença estatística significante (p &gt; 0,05). Histologicamente, foi possível observar, na perna irradiada, diminuição do número de osteócitos e dos canais de Havers, porém sem diferença estatística significante (p &gt; 0,05). Por outro lado, foi observado aumento significante de adipócitos, com conseqüente diminuição de tecido medular na perna irradiada (p &lt; 0,05) e maior atividade osteoblástica na perna contralateral (p &lt; 0,05). CONCLUSÃO: A radioterapia, na dose aplicada, determinou diminuição da atividade de remodelação óssea, que pôde ser detectada radiograficamente na maioria dos espécimes avaliados.

The use of 18F-fluoride and 18F-FDG PET scans to assess fracture healing in a rat femur model

Currently available diagnostic techniques can be unreliable in the diagnosis of delayed fracture healing in certain clinical situations, which can lead to increased complication rates and costs to the health care system. This study sought to determine the utility of positron emission tomography (PET) scanning with (18)F-fluoride ion, which localizes in regions of high osteoblastic activity, and (18)F-fluorodeoxyglucose (FDG), an indicator of cellular glucose metabolism, in assessing bone healing in a rat femur fracture model. Fractures were created in the femurs of immunocompetent rats. Animals in group I had a fracture produced via a manual three-point bending technique. Group II animals underwent a femoral osteotomy with placement of a 2-mm silastic spacer at the fracture site. Fracture healing was assessed with plain radiographs, (18)F-fluoride, and (18)F-FDG PET scans at 1, 2, 3, and 4-week time points after surgery. Femoral specimens were harvested for histologic analysis and manual testing of torsional and bending strength 4 weeks after surgery. All fractures in group I revealed abundant callus formation and bone healing, while none of the nonunion femurs were healed via assessment with manual palpation, radiographic, and histologic evaluation at the 4-week time point. (18)F-fluoride PET images of group I femurs at successive 1-week intervals revealed progressively increased signal uptake at the union site during fracture repair. In contrast, minimal tracer uptake was seen at the fracture sites in group II at all time points after surgery. Data analysis revealed statistically significant differences in mean signal intensity between groups I and II at each weekly interval. No significant differences between the two groups were seen using (18)F-FDG PET imaging at any time point. This study suggests that (18)F-fluoride PET imaging, which is an indicator of osteoblastic activity in vivo, can identify fracture nonunions at an early time point and may have a role in the assessment of longitudinal fracture healing. PET scans using (18)F-FDG were not helpful in differentiating metabolic activity between successful and delayed bone healing.

Bone Regeneration from Frozen Marrow Mesenchymal Cells/Recombinant Human Bone Morphogenetic Protein/Hydroxyapatite Transplantation

Introduction: Marrow mesenchymal cells contain stem cells and can regenerate tissues. We previously reported the clinical application of autologous cultured bone to regeneration therapy. However, in cases with low numbers of active cells, culture is often unsatisfactory. If frozen marrow cells retain their osteogenic potential, we could clinically use them in regeneration therapy as alternatives to high active cells obtained from youngsters. Here, we examined osteogenic potential of frozen human mesenchymal stem cells in combination with recombinant human bone morphogenetic protein (rhBMP) using biochemical and histological analyses. Method: Marrow fluid was aspirated from the human iliac bone of a 46-year-old man with lumbar canal stenosis during surgery. Two weeks after primary culture in standard medium, bone marrow mesenchymal stem cells (BMSCs) were trypsinized for the preparation of a cell suspension, and cells were concentrated to 106 cells/ml by centrifugation. Cells were kept at – 80 °C until use. To impregnate porous hydroxyapatite (HA) with rhBMP, 1 3g rhBMP/20 3l 0.1 % trifluoroacetic acid was applied on HA, and then desiccated under vacuum. In the present study, we used 4 subgroups: BMSC/rhBMP/HA, BMSC/HA, rhBMP/HA, and HA only. HA constructs from the 4 subgroups were implanted at subcutaneous sites on the back of 5-week-old nude mice (BALB/cA Jcl-nu). Eight weeks after implantation, implanted HA constructs were harvested, and biochemical and histological analyses were performed. Alkaline phosphatase activity (ALP) and human osteocalcin (hOs) levels were measured. Results and Discussion: ALP activity and hOs in the BMSC/BMP/HA subgroup were 2 or 3 times that in the BMSC/HA subgroup. Histological analysis showed that significant bone formation was observed in these two subgroups, and supported biochemical data. However, in the BMP/HA and HA only subgroups, significant bone formation could not be detected histologically nor biochemically. These results indicated that a combination of rhBMP and BMSCs, and only with a minimal amount of 1 3g rhBMP, allowed successful generation of human bone. In the human body, rhBMP in the order of milligrams is necessary for bone formation. However, by combining BMSCs, HA and rhBMP, only a small amount of rhBMP was needed to dramatically enhance osteogenic potential. As we reported here, cryopreserved BMSCs also showed high osteoblastic activity. In conclusion, this study provided histological and biochemical evidence that combination of cryopreserved BMSCs, BMP, and porous HA could enhance osteogenic potential.

High Osteoblastic Activity In C3H/HeJ Mice Compared to C57BL/6J Mice Is Associated with Low Apoptosis in C3H/HeJ Osteoblasts

This study sought to confirm that osteoblasts of C3H/HeJ (C3H) mice, which have higher differentiation status and bone-forming ability compared to C57BL/6J (B6) osteoblasts, also have a lower apoptosis level and to test whether the higher differentiation status and bone-forming ability of C3H osteoblasts were related to the lower apoptosis. C3H mice had 50% fewer (P < 0.01) apoptotic osteoblasts on the endocortical bone surface than B6 mice as determined by the TUNEL assay. Primary C3H osteoblasts in cultures also showed a 50% (P < 0.05) lower apoptosis level than B6 osteoblasts assayed by acridine orange/ethidium bromide staining of apoptotic osteoblasts. The lower apoptosis in C3H osteoblasts was accompanied by 22% (P < 0.05) and 56% (P < 0.001) reduction in the activity of total caspases and caspases 3/7, respectively. C3H osteoblasts also displayed greater alkaline phosphatase (ALP) activity (P < 0.001) and higher expression of Cbfa1, type-1 collagen, osteopontin, and osteocalcin genes (P < 0.05 for each). To assess if an association existed between population apoptosis and the differentiation status (ALP-specific activity) and/or bone-forming activity (insoluble collagen synthesis), C3H and B6 osteoblasts were treated with several apoptosis enhancers (tumor necrosis factor-alpha, dexamethasone, lipopolysaccharide, etoposide) and inhibitors (parathyroid hormone, insulin-like growth factor I, transforming growth factor beta1, estradiol). Both ALP (r = -0.61, P < 0.001) and insoluble collagen synthesis (r = -0.61, P < 0.001) were inversely correlated with apoptosis, suggesting that differentiation (maturation) and/or bone-forming activity of these mouse osteoblasts were inversely associated with apoptosis. In conclusion, these studies support the premise that higher bone density and bone formation rate in C3H mice could be due in part to lower apoptosis in C3H osteoblasts.

Tissue Engineering Approach to the Treatment of Bone Tumors: Three Cases of Cultured Bone Grafts Derived From Patients’ Mesenchymal Stem Cells

A novel approach to the treatment of bone tumors using tissue-engineered implants is reported in this study. The number of mesenchymal stem cells (MSCs) obtained from each patient's bone marrow cells was first increased, and the MSCs were forced to differentiate into osteoblasts followed by bone matrix formation on hydroxyapatite (HA) ceramics. The strong osteogenic ability of the implants, as evidenced by high osteoblastic activity, was confirmed. Consequently, the HA surface was covered with the patient's derived cultured osteoblast/bone matrix. The tissue-engineered HA was used to fill the patient's bone cavity after tumor curettage. Immediate healing potential was found by serial plain radiographs and computed tomograhy images, and no adverse reactions were noted in these patients. The results indicate that tissue-engineered osteogenic ceramics might be an alternative to autologous bone grafts.

In Vitro Bone Formation Induced by Immunosuppressive Agent Tacrolimus Hydrate (FK506)

When rat bone marrow cells were cultured with an immunosuppressive agent, tacrolimus hydrate (FK506), as well as with beta-glycerophosphate and vitamin C, numerous cell clusters became positive for alkaline phosphatase activity. Scanning electron microscopy revealed mineralized bone matrix in the cell clusters, which was identical to that of living bone. High levels of alkaline phosphatase (ALP), indicating osteoblastic activity, and high levels of osteocalcin (Oc) and calcium were found in the mature bone matrix of the cultures. There was significantly increased expression of mRNAs for ALP and Oc. These results indicate that the cultures contained both bone matrix and high osteoblastic activity, suggesting that FK506 induces ossification.

In vivo and in vitro evidence that the high osteoblastic activity in C3H/HeJ mice compared to C57BL/6J mice is intrinsic to bone cells

Two inbred mouse strains, C3H/HeJ (C3H) and C57BL/6J (B6), displayed a profound difference in femoral peak bone density. We have previously shown that the difference could be attributed to a greater bone formation rate (BFR) that was due to a higher osteoblastic activity [measured by a mineral apposition rate (MAR)] in the C3H (high density) than B6 (low density) mice. The present study sought to determine (1) whether the BFR/MAR differences between the two mouse strains present in weight-loaded endochondral bones are also seen in less weight-loaded membranous bones and (2) whether the difference in osteoblastic activity was seen in vitro in the absence of systemic factors. To address the first objective, we performed histomorphometric measurements on the weakly loaded membranous bones (i.e., parietal bones of the calvaria) to determine if there were similar differences in MAR and BFR of membranous bones as those of highly loaded, endochondral bones. The parietal bones of adult C3H mice showed similar increases in MAR and BFR as the endochondral bones, compared to B6 mice of same age, suggesting that the differences in the MAR and BFR in the two mouse strains are probably not related to differences in mechanical strain. These findings also suggest that the gene(s) responsible for the difference in MAR between strains may not be a mechanical response gene. With respect to the second objective, we isolated osteoblasts from the parietal bones and determined their differentiation status (i.e., ALP-specific activity) and bone-forming ability (i.e., mineralized nodule formation) in vitro. Consistent with the premise that C3H osteoblasts have an intrinsic, higher differentiation status and bone-forming ability than B6 osteoblasts, osteoblasts isolated from C3H mice as compared with those from B6 mice had a significantly greater ALP-specific activity and a greater ability to form mineralized nodules in vitro in the absence of systemic factors. Because differences in ALP activity, bone-forming ability, cortical bone width, and osteoblastic activity were detected at birth, the different MAR/BFR phenotypes develop at very early life and even perhaps during embryogenesis. In conclusion, we have for the first time provided evidence that the genetic differences responsible for the observed MAR/BFR phenotype in the C3H-B6 strains are intrinsic to osteoblasts and might not depend on responses to mechanical loading and/or alterations in systemic factors.

Intérêt de l'électrophorèse des isophosphatases alcalines chez l'insuffisant rénal hémodialysé

The aim of the study is to prove the usefulness of an electrophoretic technic for multiple forms of alkaline phosphatase semi-automatised on Hydrasys (Sebia) in renal osteodystrophy. This technology allows to identify a bone variant associated with high osteoblastic activity. Electrophoresis and immunofluorometric determination of bone fraction (Ostase) were realised in 105 hemodialysed patients treated by 1.25 (OH)2 vit D when PTH was >150 pg/ml. We frequently observe in this population a high activity for intestinal, hepatic and macromolecular forms. A bone variant is observed among 10% of the patients. The bone fraction in electrophoresis is well correlated ( r:95) with Ostase. For 103 patients, radiographic examination were performed before and after the analyses. We observed lesions of hyperparathyroidism in 42% of patients. Sensitivity, specificity, positive predictive value, negative predictive value are respectively 31%, 92%, 72%, 65% for an abnormal electrophoresis, 14%, 88%, 46%, 58% for an out of range value of Ostase and 25%, 85%, 59%, 58% for PTH>150 pg/ml.

Proceedings: Pathogenesis and Treatment of Renal Osteodystrophy

Renal osteodystrophy is the term used to describe the many different patterns of the skeletal abnormalities that occur in patients with chronic kidney disease. The main two conditions are osteitis fibrosa, characterized by high bone turnover, increased osteoclastic and osteoblastic activity, and high levels of circulating parathyroid hormone (PTH) and adynamic bone disease characterized by low bone turnover and low levels of circulating PTH. Retention of phosphorus, decreased levels of calcitriol in blood, decreased levels of serum ionized calcium, reduced numbers of vitamin D receptors and calcium sensors in the parathyroid gland, and skeletal resistance to the calcemic action of PTH play a major role in the development of renal osteodystrophy. This review will describe the current approach for the treatment of renal osteodystrophy.

Histopathological and biochemical changes in the sutural region in craniosynostosis

Histopathological observations and biochemical analysis of sutural bones in nine patients with craniosynostosis were compared with control subjects of the same age range. Microscopic examination in craniosynostosis showed formation of an active osseous front, with higher osteoblastic activity than in controls. Biochemical analysis revealed higher calcium, phosphorus, alkaline phosphatase, phospholipids and chondroitin sulphate-A contents in sutural bones of the same patients. The present study systematically establishes a premature increase in osteogenesis in the sutures of craniosynostosis patients.

Analysis of gene expression in osteogenic cultured marrow/hydroxyapatite construct implanted at ectopic sites: A comparison with the osteogenic ability of cancellous bone

We investigated the in vivo osteogenic ability of cultured marrow cells subcultured in porous hydroxyapatite. This osteogenic ability was compared with that of cancellous bone grafts. Fresh marrow cells were obtained from young adult rat femora and cultured in a standard medium for 10 days, then trypsinized and used to make constructs of porous hydroxyapatite (HA) and cultured marrow cells. An additional 2-week culture (subculture) was performed for the construct in standard medium with and without the addition of dexamethasone (Dex). The 2-week subcultured constructs then were implanted into subcutaneous sites of syngeneic rats. These implants and the rat cancellous bone were harvested and prepared for gene expression analysis of alkaline phosphatase (ALP) and osteocalcin (OC) as well as for histological analysis. ALP and OC mRNAs could be detected in Dex-treated subcultured constructs 1 week after implantation, with an increase at 2 weeks, comparable to the observation in cancellous bone. Histological analysis showed active bone formation even 1 week postimplantation. In contrast, the subcultured constructs without the addition of Dex did not show bone formation, and only small levels of ALP and OC mRNAs were found. These results indicate that the bone tissue formed by grafting the Dex-treated construct of cultured marrow cells and hydroxyapatite possesses a high osteoblastic activity comparable to that of viable cancellous bone. Thus the prefabricated osteogenic subcultured marrow/HA construct may be applicable in bone reconstructive surgery. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 568–573, 1998.

The subchondral bone in osteoarthritis and rheumatoid arthritis of the knee. A histological and microradiographical study.

Specimens of the joint surfaces of the tibia from patients with OA and RA were exposed were examined for bone mineralization, bone formation, osteoid tissue and bone resorption. Judging from the appearance of the osteoblasts in OA the sclerotic changes are mainly focal with relatively little osteogenesis. No osteoclasia was seen in the sclerotic areas. Breakdown of the mineralized cartilage is followed by the development of cysts with highly cellular connective tissue with high osteoblastic activity and osteoclasia. Osteoid tissue is relatively sparse. The changes in RA are more diffuse with a more active osteoblastic activity and widespread zones of osteoid tissue as well as resorption by osteoclasts. It appears as if the increased uptake of 85Sr in OA is more dependent on the occurrence of relatively inert osteosclerosis than on a rapid turnover of the bone tissue.