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Biomedical subjects

D J Simmons

Publications and source records attributed to D J Simmons.

At least 19 recordsLinked to original sources
PubMed1999

Expression of BMP-2 by rat bone marrow stromal cells in culture.

To investigate the role of bone morphogenetic protein (BMP-2) in ossifying rat bone marrow stromal cell cultures, we determined the population of fibroblast-like stromal cells that expressed BMP-2 immunocytochemically (anti-rhBMP-2 monoclonal antibody), and compared that to alkaline phosphatase (AP) and collagen synthesis formed in culture over a 4-week period in control and dexamethasone-supplemented mineralizing media. In control media, the percentage of BMP-2-positive stromal cells (BMP-2(+)) increased from 12 to 25% within the first 4 days of culture. In mineralizing media, the level of BMP-2(+) cells was significantly increased (43-44%). The intensity of immunostaining gradually increased with time. The levels of AP were undetectable at 1 week in both control and mineralizing media, but increased gradually over the next 2 weeks and peaked at 3 weeks. ALP levels were significantly greater in cultures grown in mineralizing medium (P < 0.05 at 3 weeks, P < 0.01 at 4 weeks). Collagen synthesis peaked and was significantly greater at 3 weeks (P < 0.05) in cultures grown in mineralizing medium. The levels of AP and collagen synthesis most closely reflected the changes in the percentage of BMP-2(+) cells from 7 to 28 days. Though these changes may reflect a primary action of BMP-2 on marrow osteoprogenitor-like stromal cells, they do not exclude a mechanism that involves the induction of other members of the BMP family known to stimulate AP and collagen synthesis. We conclude that BMP-2 expression in cultures of fibroblast-like marrow stromal cells is enhanced when those cells are induced to become osteoblasts by exposure to dexamethasone.

Animals↗
PubMed1999

Transforming growth factor-beta2 mRNA level in unloaded bone analyzed by quantitative in situ hybridization.

The effects of tail suspension hypokinesia on the gene expression for TGF-beta2 at different sites within bone were evaluated. TGF-beta2 mRNA signal levels were determined quantitatively by an image analysis system. The osteopenia induced by tail suspension was verified by histomorphometry. In the periosteum of nonsuspended control rats, TGF-beta2 mRNA was highly expressed in the preosteoblasts and osteoblast-rich cambial layers; very little signal was present within the middle and outer fibroblastic layers. Gene expression was significantly reduced in suspended rats, and this was evident both in terms of the number of silver grains in unit area or length of tissue and in each osteoblast and preosteoblast. Hypokinesia also reduced the expression of TGF-beta2 mRNA level in cortical and trabecular bone osteocytes, but did not adversely affect the mRNA level in chondrocytes in growth plate. The results affirm the site-specific response of TGF-beta2 gene expression in rats, and suggest that the cortical and trabecular bone osteopenia associated with hypokinesia in rats may be associated with a deficit in osteoblastic and osteocytic TGF-beta2 level.

Animals↗
PubMed1999

Long-term remodeling of vascularized and nonvascularized onlay bone grafts: a macroscopic and microscopic analysis.

The present study was performed to compare vascularized and nonvascularized onlay bone grafts to investigate the potential effect of graft-to-recipient bed orientation on long-term bone remodeling and changes in thickness and microarchitectural patterns of remodeling within the bone grafts. In two groups of 10 rabbits each, bone grafts were raised bilaterally from the supraorbital processes and placed subperiosteally on the zygomatic arch. The bone grafts were oriented parallel to the zygomatic arch on one side and perpendicular to the arch on the contralateral side. In the first group, vascularized bone grafts were transferred based on the auricularis anterior muscle, and in the second group nonvascularized bone grafts were transferred. Fluorochrome markers were injected during the last 3 months of animal survival, and animals were killed either 6 or 12 months postoperatively. The nonvascularized augmented zygoma showed no significant change in thickness 6 months after bone graft placement and a significant decrease in thickness 1 year after graft placement (p < 0.01). The vascularized augmented zygoma showed a slight but statistically significant decrease in thickness 6 months after graft placement (p < 0.003), with no significant difference relative to its initial thickness 1 year after graft placement. In animals killed 6 months after bone graft placement, both the rate of remodeling and the bone deposition rate measured during the last 3 months of survival were significantly higher in the vascularized bone grafts compared with their nonvascularized counterparts (p < 0.02). By 1 year postoperatively, there were no significant differences in thickness, mineral apposition rate, or osteon density between bone grafts oriented perpendicular and parallel to the zygomatic arch. These findings indicate that the vascularity of a bone graft has a significant effect on long-term thickness and histomorphometric parameters of bone remodeling, whereas the direction of placement of a subperiosteal graft relative to the recipient bed has minimal effect on these parameters. In vascularized bone grafts, both bone remodeling and deposition are accelerated during the initial period following graft placement. Continued bone deposition renders vascularized grafts better suited for the long-term maintenance of thickness and contour relative to nonvascularized grafts.

Animals↗
PubMed1998

Positively charged dextran resin inhibits trabecular bone repair in the rabbit tibial physis.

Because exposure to positively charged dextran resin (PCDR) inhibits the growth of cultured rat and human bone cells, we tested the hypothesis that PCDR might inhibit bone repair in vivo. Central physeal defects were created by drilling 3.0-mm holes from the proximal tibial plateau into the metaphysis. The defects in left tibiae were packed with neutral resin (control); those in right tibiae were filled with PCDR. At the end of the 1st, 2nd, 3rd, and 10th postoperative weeks, the outcomes were quantitated by documenting the percent trabecular bone volume within the defect. The PCDR-filled defects showed a significant decrease in trabecular bone formation as early as the 2nd week. By the 10th postoperative week, formation of trabeculae had been reduced by nearly 40%. The inhibition conferred by PCDR suggests that the resin could be used as a suppressive interpositional material.

Animals↗
PubMed1998

Prevention of corticosteroid-induced bone loss with alendronate.

The putitive bone-sparing effect of alendronate was tested in two animal models of osteopenia: estrogen-deficient female rats and glucocorticoid-treated male rats. In the first study, 18 female Sprague-Dawley rats, 4 months of age, were ovariectomized (OVX), and an additional 6 rats were sham-operated. The OVX rats were treated with either vehicle, 17beta-estradiol (E2) (100 microg/rat/week, s.c.), or alendronate (1 mg/kg/day, on alternate days, orally). In the second study, 24 8-month-old male Wistar rats were treated with either vehicle, methyl prednisolone (7 mg/kg once a week, s.c.), prednisolone plus testosterone (16 mg/kg once every 3 weeks, i.m.), or prednisolone plus alendronate (20 microg/kg twice a week, s.c.). Prior to treatment and at the end of the 6-week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy x-ray absorptiometry, and mean femur weights were calculated. The OVX rats had subnormal BMD (-3.91 +/- 1.0% vs control +5.19 +/- 3.92%, P < 0.05) and femur weights (720 +/- 6 mg vs %; 746 +/- 11 mg, P < 0.05). OVX-induced bone loss was completely abolished by the administration of E2 (7.01 +/- 2.32%, P < 0.005; 748 +/- 6 mg, P < 0.01), or alendronate (24.2 +/- 2.73%, P < 0.0001; 779 +/- 11 mg, P < 0.001). In the second study in older male rats, glucocorticoids significantly decreased BMD (-9.70 +/- 3.44% vs -1.10 +/- 1.75%, P < 0.05), and femur weight (1070 +/- 14 mg vs 1180 +/- 24 mg, P < 0.01). Concomitant administration of testosterone (BMD 4.23 +/- 1.84%, P < 0.005; femur weight 1260 +/- 56 mg, P < 0.02), or alendronate (BMD 8.18 +/- 1.36%, P < 0.001; femur weight 1360 +/- 50 mg) with prednisolone, abolished the corticosteroid-induced bone loss. Bone histomorphometry showed a 34% loss of trabecular bone volume in glucocorticoid-treated rats (P < 0.05), which was prevented with both testosterone and alendronate therapies. However, at the doses used in both models, alendronate was more efficacious than either E2 or testosterone in increasing BMD and femur weight. In summary, this study demonstrated that alendronate therapy is highly effective in counteracting the osteopenia of OVX and glucocorticoid therapy.

Adrenal Cortex Hormones↗
PubMed1998

Torsional injury resulting in disc degeneration: I. An in vivo rabbit model.

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.

Animals↗
PubMed1998

Torsional injury resulting in disc degeneration in the rabbit: II. Associative changes in dorsal root ganglion and spinal cord neurotransmitter production.

The mechanism mediating the chronic pain associated with lumbar disc degeneration may involve neurotransmitters elaborated by dorsal root ganglion (DRG). This hypothesis has been tested in an applicable rabbit model of disc degeneration. Twenty control male rabbits underwent a soft-tissue release; 20 experimental rabbits sustained a facetectomy and capsulotomy and received an acute torsional lumbar injury. The levels of calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P were measured in the DRG, spinal cord, and disc at 10, 30, 60, and 90 days postoperatively. Torsional injury was associated with a statistically significant increase in most DRG and spinal cord neurotransmitter values after 60-90 days. These points in time marked the periods of maximum biomechanical instability and disc narrowing. Such data support concepts about the association between chronic lumbar spinal instability, disc degeneration, and pain.

Animals↗
PubMed1997

Antitumor effect of positively charged resin in the hamster cheek pouch model.

Following the signal observation that contact with positively charged dextran resin (PCDR) inhibited the growth of cultured mammary (Hs578T and MDA-MB-231), pancreatic (H2T), and myeloma (RR-658) tumor cell lines, studies were developed in the hamster cheek pouch model using hamster H2T pancreatic tumor cells to determine if the antiproliferative effect of PCDR could inhibit tumorigenesis. In these studies, the control population represented groups injected with H2T cells alone or in combination with either neutral or negatively charged resin. When cells (5 x 10(2) to 1 x 10(5)) and PCDR were administered simultaneously, the tumor incidence (percent engraftment) and growth of tumors that already had been established were significantly reduced. When PCDR was injected into already established 1-35-mm2 H2T tumors (engraftment for 21 days = 96%), the resin suppressed the growth of the smallest tumors (< 10 mm2). In none of these trials was the somatic growth of the host hamsters affected. PCDR contact with H2T cells in vitro for 4 days or used to treat growing solid tumors for 72 days significantly reduced cellular ornithine decarboxylase activity. While the mechanism of PCDR action has not been established, the observations have implications for in vivo tumor therapeutic models.

Animals↗
PubMed1997

The origin of bone formed by heterotopic periosteal autografts.

PURPOSE: This study tested the hypothesis that a significant amount of the new bone produced by heterotopic periosteal autografts is derived osteoinductively because proliferating periosteal cells express the bone morphogenetic protein (BMP). MATERIALS AND METHODS: Rabbit ulnar and radial periosteum were autografted as free grafts (FGs) to the forelimb musculature, and as millipore diffusion chambers grafts (MDCGs) to the rectus abdominus muscle. The grafts were recovered at 3, 5, 7, 14, and 28 days postoperation, fixed in 4% paraformaldehyde, demineralized in 0.6N HCL, and 4.0 microns paraffin-embedded sections were immunostained with monoclonal antibody against recombinant human (rh) BMP-2. RESULTS: Sections from FGs recovered 5 to 28 days postoperatively exhibited cartilage and bone; fibrous tissue, cartilage, bone, and osteochondroid differentiated within MDCGs. Although BMP-2 was expressed by mesenchymal cells, osteoblasts, osteocytes, and osteoclasts, none of the MDCGs produced the osteoinductive signature of transmembrane bone formation. CONCLUSIONS: These observations indicated that the larger fraction of the new bone produced by heterotopic periosteal autografts is derived from the graft cells.

Animals↗
PubMed1997

Prevention of corticosteroid-induced bone loss with nitric oxide donor nitroglycerin in male rats.

Nitric oxide (NO) has been reported to inhibit osteoclastic bone resorption. We examined the bone sparing effect of NO on prevention of corticosteroid-induced bone loss in older male rats. Recently, we demonstrated that NO donor nitroglycerin (NG) can alleviate ovariectomy-induced bone loss, and the protective effects of estrogens on bone are mediated through NO [Bone 18(4):301-304; 1996]. Therefore, we chose to study a different model (i.e., steroid-induced osteoporosis in males) to evaluate whether NG can inhibit the bone loss associated with corticosteroid therapy. Twenty-five 32-week-old male Wistar rats were randomly assigned to five groups (n = 5/group). They received either vehicle, methylprednisolone (7 mg/kg per week), NO synthase inhibitor L-NAME (25 mg/kg per day), NO donor nitroglycerin (NG, 0.2 mg twice daily), a combination of prednisolone+NG, or prednisolone plus L-NAME, respectively. Prior to treatment and at the end of the 6 week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy X-ray absorptiometry scanning. Administration of prednisolone significantly decreased BMD (-9.50%, p < 0.05). The group receiving NG with prednisolone (-2.34%) and the group treated with NG alone (-0.36%) were not statistically different from the control group (-0.11%). Similar to the changes in BMD, femur weights were also significantly lower in prednisolone-treated rats (1.09 +/- 0.01 g vs. 1.17 +/- 0.03 in controls; p < 0.05). However, the rats receiving prednisolone together with NG were able to maintain their femur weights (1.13 +/- 0.02). There was a reduction of 9.5% of BMD (p < 0.05) and 7.8% of femoral weight (p < 0.05) in rats treated with L-NAME. A 50%-70% reduction of the percentage trabecular bone volume in the proximal tibia and distal femur and a 50% reduction of the midshaft cortical area was seen after corticosteroid therapy, and these too were prevented by administration of NG. Here, we demonstrate, for the first time, that supplementation with a NO donor compound can counteract prednisolone-induced bone loss.

Absorptiometry, Photon↗
PubMed1996

The histomorphologic changes in vascularized bone transfer and their interrelationship with the recipient sites: a 1-year study.

In 13 New Zealand White rabbits with a mean age of 6 months, vascularized bone transfers incorporated as paired auricular anterior myo-osseous flaps were harvested; they were placed in either an inlay or an onlay position relative to the zygomatic arch. The onlay bone transfers were placed either in full contact or in partial contact with the zygomatic arch. The animals were sacrificed 1 year after transfer. At 1 year, the inlay transfer simulated the adjacent zygoma in width and thickness. Onlay full contact transfers maintained significant aug mentation in thickness of the zygoma, while the onlay partial contact transfers did not; the thickness of the augmented zygoma in the onlay full contact subgroup was significantly greater than that in the onlay partial contact transfers. The onlay partial contact grafts had remodeled into the zygoma in bone contact, where the orientation of mismatched osteons within the bone transfers had transformed to match that of the native zygoma. In areas of bone contact between the onlay and the host bone, full-thickness conversion from a cortical to a trabecular architecture had occurred in both the transfer and host bones. These findings have numerous implications regarding mechanisms that could be exploited clinically to optimize the survival of a bone transfer; they also raise questions regarding alteration of the recipient bed after placement of an onlay bone transfer.

Animals↗
PubMed1995

Rat tail suspension reduces messenger RNA level for growth factors and osteopontin and decreases the osteoblastic differentiation of bone marrow stromal cells.

We previously reported that bone marrow stromal cells produce insulin-like growth factors (IGF-I and -II), and that medium conditioned by marrow stromal cells stimulates osteoblast proliferation in vitro. The present study employed the rat tail-suspension model to unload the hindlimbs. It was designed to test the hypothesis that the development of osteopenia or osteoporosis could be due to a deficit in the osteogenic function of marrow stromal cells. Although tail suspension suppressed body weight during the first 3 days of an 11-day pair-fed study, the overall weight gain recorded by these animals was normal. Nevertheless, bone growth was inhibited by suspension. Similarly, the total adherent marrow stromal cell population harvested from the femurs and tibias was decreased by tail suspension, and only half the normal number of fibroblastic stromal cell colonies grew when they were cultured. The proliferation of alkaline-phosphatase-positive cells in the stroma was also inhibited. Northern hybridization revealed that the messenger RNA level for transforming growth factor-beta 2 and IGF-II in stromal cell was reduced by tail suspension. The production of IGF-II by marrow stromal cells was also decreased. The steady-state level of five different transcript sizes of IGF-I mRNA was altered differentially by tail suspension. Osteopontin mRNA was also reduced in marrow stromal cells from tail-suspended rats compared with the normal rats. These data suggest that skeletal unloading not only alters the mRNA level for growth factors and peptide production, but also affects the proliferation and osteogenic differentiation of marrow stromal cells. These changes may be responsible for the reduced bone formation in osteopenia and osteoporosis.

Animals↗
PubMed1995

Expression of selected osteogenic markers in the fibroblast-like cells of rat marrow stroma.

The fibroblast-like cells in the marrow stromal system were separated from endothelial cells and macrophages by negative selection of magnetic beads. Immunocytochemistry confirmed that these fibroblast-like cells expressed fibronectin and collagen Type III, but not Factor VIII and epithelial membrane antigen (endothelial cell markers) or Mac I (macrophage marker). The fibroblast-like stromal cells (FSC) synthesized the insulin-like growth factors (IGF)-I and -II in amounts equivalent to that produced by unfractionated marrow stromal cells (UMSC); in both, the concentration of IGF-II was 10 times higher than that of IGF-I. Northern analysis revealed that FSC and UMSC expressed identical patterns of mRNAs for IGF-I and transforming growth factor (TGF) -beta 2, for osteopontin, and for procollagen Types I and III (Type I > Type III). Type II procollagen mRNA was not expressed in both cell populations. The TGF-beta 2 gene mRNA was expressed at a lower level by the FSC than UMSC. The pattern of gene expression in these cells is consistent with an osteoprogenitor phenotype. Both FSCs and UMSCs express parathyroid hormone (PTH) and estrogen receptor genes (rtPCR technique). The study provides additional evidence that fibroblast-like marrow stromal cells have an osteoblast signature, and that they are largely responsible for the osteogenic performance of cells in unfractionated marrow.

Animals↗
PubMed1995

Effects of C-terminal parathyroid hormone-related peptide on osteoblasts.

A C-terminal analog of parathyroid hormone-related peptide (PTHrP), PTHrP(107-139), was found to stimulate cAMP production in three osteoblast cell preparations. The effect was studied most extensively in ROS 17/2.8 cells. The effect was dose-related and comparable in magnitude to that produced by PTHrP(1-34), but potency was lower. The functional significance of the cAMP effect is unknown, but preliminary findings indicated that PTHrP(107-139) also inhibited osteopontin mRNA levels in ROS 17/2.8 cells treated with peptide for 48 h. The results suggest that the carboxy-terminal region of PTHrP may play a role in bone metabolism by influencing osteoblast activity.

Animals↗
PubMed1994

Negatively charged resins stimulate bone formation in subperiosteal sites in rats. The effect of age.

The osteogenic response to subperiosteal injection of negatively charged ion exchange resins was compared in the tibiae of one-month and 16- to 22-month-old rats. The resins were administered either in the form of beads (CM Sephadex) or as particles (CM cellulose, carboxymethylcellulose), and the animals were killed at two weeks and at one month after injection. Histologically, the resins did not produce an inflammatory response. Periosteal bone formation was observed wherever resin was in contact with bone, and in the resin bed the connective tissues that invested the charged materials ossified within the first month. Marrow spaces commonly formed where periosteal growth was most rapid. The osteogenic effect was independent of resin conformation, and it was more pronounced in the younger rats.

Aging↗
PubMed1994

The healing of grafts combining freeze-dried and demineralized allogeneic bone in rabbits.

The adjunctive role of demineralized bone matrix (DBM) in enhancing the incorporation of segmental freeze dried (FD)-allogeneic bone grafts has been studied in the rabbit ulna and fibula. The studies compared the healing patterns of fresh segmental autografts, FD-allografts, DBM-allografts, and FD-allografts supplemented at the graft-host junctions with FD- or DBM-allografts as particulates (ulna) or as segmental struts (fibula). The outcome was evaluated at five and ten weeks by a radiologic score, by biomechanical properties (breaking strength, energy to failure, stiffness), and histology. The ulnar autografts healed most rapidly (ten weeks = 100%), followed by DBM allografts (60%). By all criteria, FD-allografts were poorly incorporated (20-40%), and the process was not improved by supplements of FD- or DBM-particulate/strut bone. Histologically, the DBM component of composite fibular strut grafts was osteoinductive and united with host tissues within 35 days. The contiguous FD-allograft struts were not incorporated, showing fibrocartilaginous nonunions and resorptive foci. While the addition of DBM does not protect FD-allograft integrity in the rabbit, segmental mineralized FD-allografts could provide mechanical support for some intervals until, in such composite grafts, osteoinductive processes produced biomechanically competent new bone.

Animals↗
PubMed1993

Effects of aluminum on rat bone cell populations.

Aluminum (Al) loading is associated with reduced bone formation and osteomalacia in human and certain animal models. However, uncertainty exists as to the cellular effect(s) of Al as both inhibition and stimulation of osteoblast proliferation have been reported. Furthermore, the extent to which Al affects osteoprogenitor cell populations is unknown. To determine the cellular effects of Al in the rat, an animal model in which Al bone disease has been produced, we compared the in vitro effect of 10-50 microns Al on the proliferation and hydroxyproline collagen formation of marrow osteoprogenitor stromal cell populations and perinatal rat calvarial osteoblasts. In subconfluent cultures, Al suppressed proliferation of both marrow fibroblast-like stromal cells and calvarial osteoblasts. In confluent cultures, however, Al selectively stimulated periosteal fibroblast and osteoblast DNA synthesis and collagen (hydroxyproline) production, both in the presence or absence of 1,25-dihydroxyvitamin D. Osteocalcin was not detected in osteoblast-conditioned media or extracellular matrix. These observations suggest that the bone formation defect associated with Al toxicity in growing rats may be a function of impaired patterns of osteoprogenitor/osteoblast proliferation. Furthermore, the Al-stimulated increase in collagen formation is consistent with the development of osteomalacia in Al-toxic humans and animals. The mechanism by which Al stimulated DNA synthesis and collagen production in more mature cultures awaits further study.

Aluminum↗