Sealing effect of hydroxyapatite coating on peri-implant migration of particles

We have studied the beneficial effects of a hydroxyapatite (HA) coating on the prevention of the migration of wear debris along the implant-bone interface. We implanted a loaded HA-coated implant and a non-coated grit-blasted titanium alloy (Ti) implant in each distal femoral condyle of eight Labrador dogs. The test implant was surrounded by a gap communicating with the joint space and allowing access of joint fluid to the implant-bone interface. We injected polyethylene (PE) particles into the right knee three weeks after surgery and repeated this weekly for the following five weeks. The left knee received sham injections. The animals were killed eight weeks after surgery. Specimens from the implant-bone interface were examined under plain and polarised light.

Only a few particles were found around HA-coated implants, but around Ti implants there was a large amount of particles. HA-coated implants had approximately 35% bone ingrowth, whereas Ti implants had virtually no bone ingrowth and were surrounded by a fibrous membrane.

Our findings suggest that HA coating of implants is able to inhibit peri-implant migration of PE particles by creating a seal of tightly-bonded bone on the surface of the implant.

A multicentre phase II pilot study of epirubicin and Taxol (paclitaxel) in patients with advanced breast cancer

Anthracyclines are the gold standard monotherapy for metastatic breast cancer. Higher response rates are seen with drug combinations, especially with newer agents such as taxanes. The purpose of this study was to evaluate the toxicity and activity of the combination of paclitaxel and epirubicin in patients with advanced breast cancer. Thirty-five women with locally advanced or metastatic breast cancer (first and second relapse) were treated with epirubicin 75 mg/m2 and paclitaxel 200 mg/m2 3-weekly. Six centres recruited 35 patients; 34 (97%) were assessable for response. Eighteen had undergone prior chemotherapy, including six (17%) with anthracycline-containing regimens. Grade 4 neutropenia was found in 33 patients (94%), which was of 4 days' average duration; however, infective complications were rare, with only nine cycles (6%) complicated by neutropenic sepsis. There were two sepsis-related deaths. Symptomatic cardiotoxicity was infrequent, although a >15% decline in cardiac function was recorded in five patients (14%). Grade 3 peripheral neuropathy occurred in three patients (9%). The overall response rate was 50% (95% confidence interval 33-67) (complete response 12%; partial response 38%), with a median duration of response of 31 weeks. The median time to progression was 27 weeks, with a median survival of 48 weeks. This regimen appears to be a relatively safe, tolerable and effective treatment for advanced breast cancer. A United Kingdom Co-ordinating Committee for Cancer Research Phase III trial (AB-01) comparing this combination of epirubicin and paclitaxel with cyclophosphamide and paclitaxel completed accrual in November 1999.

In vitro reaction to orthopaedic biomaterials by macrophages and lymphocytes isolated from patients undergoing revision surgery

Periprosthetic tissues observed at sites of loose total joint implants exhibit abundant macrophages, lymphocytes, fibroblasts and particulate debris. Macrophages phagocytose orthopaedic debris and release proinflammatory cytokines, chemokines, matrix metalloproteinases and other substances. In addition, other cell types present in tissues harvested from the bone-implant interface are thought to influence periprosthetic bone resorption. The present study examined the effects of polymethylmethacrylate (PMMA), cobalt chrome molybdenum alloy (CoCr), and titanium-alloy particle challenge on macrophages co-cultured with lymphocytes in vitro. Potential synergistic effects of lymphocytes on macrophage activation were determined by measuring interleukin-6 and tumor necrosis factor-alpha release following exposure to orthopaedic biomaterial particles. Exposure of macrophages or macrophages co-cultured with lymphocytes to all three types of particles resulted in increased release of interleukin-6 and tumor necrosis factor-alpha at 48 h, when compared to macrophages or macrophages co-cultured with lymphocytes, respectively, cultured in the absence of particles. Lymphocytes isolated from periprosthetic tissues secreted increased basal levels of cytokines relative to peripheral blood lymphocytes. Higher doses of PMMA and titanium-alloy particles stimulated increased levels of cytokine release in the macrophage and macrophage/lymphocyte groups. In contrast, a higher dose of CoCr particles (0.075% v/v) was not as effective as the 0.015% v/v dose, indicating probable CoCr toxicity. The macrophage/lymphocyte co-culture did not show synergism between the two types of cells with respect to cytokine release. T-cells at the bone-implant interface may alter the biological response to particulate debris.

The influence of human intervertebral disc tissue on the metabolism of osteoblast-like cells

Extensive studies have been performed to evaluate different factors that may affect on spinal interbody fusion, but the role of intervertebral disc tissue in the fusion process remains unclear. To study the influence of intervertebral disc tissue on osteoblast metabolism, we harvested disc tissue from patients who had undergone spinal surgery. The nucleus pulposus and annulus fibrosus were separately co-cultured with osteoblast-like cells SaOS-2 by means of culture inserts or organ culture. We assayed alkaline phosphoatase activity, 3H-thymidine incorporation into the DNA, and production of collagen type I, IL-1beta, IL-6, IL-10, and TNF-alpha. Exposure of the nucleus pulposus (NP) to osteoblast-like cells revealed stimulation of alkaline phosphatase production, 3H-thymidine incorporation and collagen type I production. Exposure of the annulus fibrosus (AF) stimulated 3H-thymidine incorporation and collagen type I production, but did not affect ALP activity. IL-6 was detected after application of NP and AF. Interleukin IL-10, IL-1beta and TNF-alpha were all below detection levels after application of disc tissue. Our findings show that frozen disc tissue stimulates the metabolism of osteoblast-like cells in vitro.

Monocyte migration inhibitory factor synthesis and gene expression in particle-activated macrophages

This study analysed MIF mRNA and protein expression in human macrophages exposed in vitro to polymethylmethacryate and titanium alloy particles. MIF levels released from macrophages without exposure to particles were in the range of 2-4 ng/ml. Exposure of macrophages to particles as demonstrated increased MIF release at 0. 075%-0.225% v/v particle concentration, which was maximal at 12-24 h. MIF mRNA signal levels in cells with and without particles at a concentration of 0.075% showed no significant differences in a time course experiment. The profile of MIF release in response to increasing particle concentration coincided with increased release of lactate dehydrogenase. The viability of the cells was unchanged by the addition of particles as determined by 3H-thymidine uptake. These data suggest that MIF expression may represent an independent macrophage response to locally high particle concentrations.

Chemotaxis and activation of particle-challenged human monocytes in response to monocyte migration inhibitory factor and C-C chemokines

Cytokines that regulate monocyte migration were found in membrane tissue surrounding loosened prosthetic implants. Monocyte migration inhibition factor (MIF) is able to inhibit macrophage migration. Monocyte chemoattractant protein (MCP) and macrophage inflammatory protein (MIP) are potent macrophage chemoattractants. These cytokines may be expressed as part of the foreign body response to prosthetic particulate debris. Chemotaxis analysis and macrophage activation experiments were performed to determine the effects of MIF, MCP-1, and MIP-1alpha on macrophage migration and activation in vitro. We demonstrated that MIF had its maximal migration inhibitory effect for unchallenged and particle challenged macrophages at 1 ng/mL. MCP-1 and MIP-1alpha stimulated macrophage chemotaxis maximally at 1 to 10 ng/mL. Dose-response studies with MIF, MCP-1, and MIP-1alpha demonstrated that these cytokines did not modulate activation of unchallenged or particle challenged macrophages as evaluated by IL-6 and TNF-alpha release. However, these cytokines do not appear to affect macrophage release of proinflammatory mediators in vitro.

Osteogenic protein 1 device stimulates bone healing to hydroxyapaptite-coated and titanium implants

This study evaluated the effects of osteogenic protein 1 (OP-1) placed in a gap around uncoated and hydroxyapatite (HA)-coated implants. Unloaded cylindrical titanium alloy implants were inserted in the femoral condyles of 16 skeletally mature dogs surrounded by a 3-mm gap. The gap around the implants was filled with 325 microg OP-1 in 130 mg bovine collagen type I as carrier (OP-1 device) or collagen carrier alone or left empty. All groups were tested with both HA-coated and uncoated implants, and the animals were sacrificed after 6 weeks. Implant fixation was determined by push-out test. Bone ongrowth and bone formation were evaluated by quantitative histomorphometry. OP-1 device enhanced mechanical fixation of uncoated and HA-coated implants, resulting in a higher shear strength than implants with collagen matrix and control implants. Bone ingrowth and bone formation in the gap were also stimulated 3-fold for OP-1 groups when compared with empty controls, but no difference was found between OP-1 groups and collagen matrix groups. This study suggests that the OP-1 device placed in a gap around uncoated and HA-coated implants is capable of enhancing mechanical fixation and periimplant bone formation. The collagen carrier alone also enhanced bone ongrowth and fixation significantly.

Deterioration of intraoral recognition of shapes after treatment of oral and pharyngeal cancer

Thirty patients with diagnosed malignant tumors of the oral cavity or pharynx were tested in regards to intraoral shape recognition at 4 test occasions: before all treatment, after radiotherapy, 6 months after surgery, and 1 year after surgery. They were compared within groups as well as with a group of healthy reference individuals of the same age who underwent the same test procedure at a 2-month interval. The tumor itself did not influence the capability of shape recognition. The reference individuals demonstrated significantly better results on the second test occasion, which is known as a learning effect. Learning improvement was not seen in the patients whose second test occasions were after radiotherapy, implying an impediment amounting to the magnitude of the learning effect. At 6 months after surgery the patients' capabilities of shape recognition had deteriorated significantly with no difference between the oral cancer group and the pharyngeal cancer group. No spontaneous rehabilitation had taken place 1 year after surgery. The presence or absence of surgical lingual nerve damage did not influence the results. The nonoperated side does not compensate for the operated one. It is plausible that decreased oral sensory acuity in recognizing the shape of the bolus contributes to postoperative swallowing problems.

Conceptual design of industrial process displays

Today, process displays used in industry are often designed on the basis of piping and instrumentation diagrams without any method of ensuring that the needs of the operators are fulfilled. Therefore, a method for a systematic approach to the design of process displays is needed. This paper discusses aspects of process display design taking into account both the designer's and the operator's points of view. Three aspects are emphasized: the operator tasks, the display content and the display form. The distinction between these three aspects is the basis for proposing an outline for a display design method that matches the industrial practice of modular plant design and satisfies the needs of reusability of display design solutions. The main considerations in display design in the industry are to specify the operator's activities in detail, to extract the information the operators need from the plant design specification and documentation, and finally to present this information. The form of the display is selected from existing standardized display elements such as trend curves, mimic diagrams, ecological interfaces, etc. Further knowledge is required to invent new display elements. That is, knowledge about basic visual means of presenting information and how humans perceive and interpret these means and combinations. This knowledge is required in the systematic selection of graphical items for a given display content. The industrial part of the method is first illustrated in the paper by a simple example from a plant with batch processes. Later the method is applied to develop a supervisory display for a condenser system in a nuclear power plant. The differences between the continuous plant domain of power production and the batch processes from the example are analysed and broad categories of display types are proposed. The problems involved in specification and invention of a supervisory display are analysed and conclusions from these problems are made. It is concluded that the design method proposed provides a framework for the progress of the display design and is useful in pin-pointing the actual problems. The method was useful in reducing the number of existing displays that could fulfil the requirements of the supervision task. The method provided at the same time a framework for dealing with the problems involved in inventing new displays based on structured analysis. However the problems in a systematic approach to display invention still need consideration.

Interleukin-4 inhibits granulocyte-macrophage colony-stimulating factor, interleukin-6, and tumor necrosis factor-alpha expression by human monocytes in response to polymethylmethacrylate particle challenge in vitro

The outcome of total joint arthroplasty is determined by biological events at the bone-implant interface. Macrophages phagocytose implant or wear debris at the interface and release proinflammatory mediators such as interleukins 1 and 6, tumor necrosis factor-alpha, and prostaglandin E2. These mediators are thought to contribute to the resorption of periprosthetic bone. Previous studies of tissues harvested from the bone-implant interface of failed orthopaedic implants demonstrated a possible role for two other cytokines, granulocyte-macrophage colony-stimulating factor and interleukin-4. The present study examined the effects of in vitro challenge with polymethylmethacrylate particles on the expression of granulocyte-macrophage colony-stimulating factor by primary human monocytes/macrophages and the role of interleukin-4 in regulating this expression. The polymethylmethacrylate particles caused a dose-dependent release of granulocyte-macrophage colony-stimulating factor at 48 hours. This release was accompanied by increased expression of interleukins 6 and 1beta and tumor necrosis factor-alpha. Release of the lysosomal enzyme hexosaminidase also increased in response to the particles. Interleukin-4 inhibited the expression of granulocyte-macrophage colony-stimulating factor, interleukin-6, and tumor necrosis factor-alpha at 48 hours in a dose-dependent manner. The data presented in this study confirm the hypothesis that interleukin-4 downregulates particle-induced activation of macrophages, as demonstrated by the decreased release of proinflammatory mediators.

Home care for stem cell transplantation patients

Following high-dose chemotherapy patients need to undergo bone marrow rescue through stem cell transplantation. Patients who received stem cell transplantation at home expressed satisfaction with this form of therapy. Performing stem cell transplantation in the home can reduce both costs and the risk of infection.

A review of ceramic coatings for implant fixation

The present series of eight studies was performed in order to investigate the effect of various clinically relevant factors on bone ingrowth in relation to hydroxyapatite (HA) and titanium-alloy (Ti) coating when subjected to pathological and mechanical conditions mimicking the clinical situation. HA- and Ti-coated implants were inserted into the femoral condyles of mature dogs and one study was performed on humans. The observation period ranged from 4 to 52 weeks, and the results were evaluated by mechanical push-out testing, histomorphometric analysis, polarized light microscopy, UV fluorescence microscopy and collagen analysis. There were no complications related to the operative procedures, and all dogs were killed according to the original time schedule. Two studies focused on in vivo mechanisms and factors influencing resorption of HA coating. The overall conclusions from these studies are that HA coatings do resorb in vivo, that micromotion accelerates resorption, and that resorbed HA is partly replaced by newly formed bone, suggesting that implants fixation is durable. The other studies focused on the significance of mechanical stabilization and loading conditions of the implant immediately after surgery. From these studies, it can be concluded that HA-coating has a positive effect on bone-implant fixation in various situations, i.e., under stable loaded conditions and under unstable mechanical conditions. The most striking effect of HA coating was that it enhanced bone growth across a gap around the implant both during stable and unstable mechanical conditions; it even converted a motion-induced fibrous membrane to bony anchorage.

Interferon-gamma exacerbates polymethylmethacrylate particle-induced interleukin-6 release by human monocyte/macrophages in vitro

Periprosthetic membranes commonly observed at sites of total joint implant loosening exhibit abundant macrophages and particulate debris. Macrophages phagocytose orthopedic debris and release the pro-inflammatory mediators interleukin-1, interleukin-6, tumor necrosis factor-alpha, and prostaglandin E2. In addition, other immunologic agents, such as interferon-gamma, are present in tissues harvested from the bone-implant interface of failed orthopedic implants. The present study examined the effects of interferon-gamma on polymethylmethacrylate (PMMA) particle-challenged monocyte/macrophages in vitro. The effects of interferon-gamma were determined by measuring interleukin-6 and tumor necrosis factor-alpha release by primary human monocyte/macrophages following exposure to PMMA particles. Exposure of the monocyte/macrophages to PMMA particles resulted in a dose-dependent release of interleukin-6 and tumor necrosis factor-alpha at 48 h. The interleukin-6 release in response to PMMA particle challenge was stimulated by 76% and 127% in the presence of 1.0 and 10.0 ng/mL of interferon-gamma, respectively. Interferon-gamma challenge alone did not alter interleukin-6 release relative to controls. In contrast to interleukin-6, interferon-gamma challenge stimulated tumor necrosis factor-alpha release in a dose-dependent manner. In the presence of particles, addition of 1.0 and 10.0 ng/mL of interferon-gamma resulted in 17% and 171% increases in the levels of tumor necrosis factor-alpha release, respectively, relative to cultures challenged solely with particles. Blocking antibody to IFN-gamma inhibited the effect of IFN-gamma on particle-induced interleukin-6 and tumor necrosis factor-alpha release. The data presented in this study demonstrate that the immunologic modulator interferon-gamma exacerbates monocyte/macrophage release of the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-alpha in response to PMMA particle challenge in vitro.

Phase II studies of RMP-7 and carboplatin in the treatment of recurrent high grade glioma. RMP-7 European Study Group

The selective bradykinin analogue, RMP-7, transiently increases the permeability of the blood brain barrier and the delivery of hydrophilic agents into brain tumours. In 87 recurrent glioma patients (WHO Grade III/IV, median age 46, Karnofsky 70%) clinical and Magnetic Resonance Imaging (MRI) responses to i.v. cycles (q 28 days) of RMP-7 (300 ng/kg given as a 10 min infusion) and carboplatin (AUC 4-9) were assessed. 45 of these patients were chemotherapy naive (CN-RMP) and 42 had received one prior course of chemotherapy (CP-RMP). Neurological impairment, performance status and steroid use were measured prior to dosing at each cycle and tumour volume by 3-D MRI at the end of cycles 2, 4, 6, 9 and 12. Clinical evaluation of response demonstrated that 61% of CN-RMP patients were either stable or improved whilst this was 39% for CP-RMP patients, of which 37% and 8% improved respectively. Radiological evaluation showed 79% of CN-RMP patients were either stable, partial or complete responses and 24% for CP-RMP patients, of which 32% and 5% were CR or PR respectively. The median duration of response was 30.3 weeks in CN-RMP patients and 19.6 weeks in the CP-RMP group. Lack of response was associated with substantial baseline tumour volume. Drug toxicity was as previously reported for carboplatin. 11 patients had treatment-associated transient focal seizures. These results indicate that RMP-7 and carboplatin have significant activity in recurrent malignant glioma following radiotherapy.

The influence of crystallinity of the hydroxyapatite coating on the fixation of implants

We inserted two hydroxyapatite (HA)-coated implants with crystallinities of either 50% (HA-50%) or 75% (HA-75%) bilaterally into the medial femoral condyles of the knees of 16 dogs. The implants were allocated to two groups with implantation periods of 16 and 32 weeks. They were weight-bearing and subjected to controlled micromovement of 250 μm during each gait cycle. After 16 weeks, mechanical fixation of the HA-50% implants was increased threefold as compared with the HA-75% implants. After 32 weeks there was no difference between HA-50% and HA-75%. Fixation of HA-75% increased from 16 to 32 weeks whereas that of HA-50% was unchanged. HA-50% implants had 100% more bone ingrowth than HA-75% implants after 16 weeks. More HA coating was removed on HA-50% implants compared with HA-75% implants after both 16 and 32 weeks. No further loss of the HA coating was shown from 16 to 32 weeks.

Our study suggests that the crystallinity of the HA coating is an important factor in its bioactivity and resorption during weight-bearing conditions. Our findings suggest two phases of coating resorption, an initial rapid loss, followed by a slow loss. Resorbed HA coating was partly replaced by bone ingrowth, suggesting that implant fixation will be durable.

The influence of crystallinity of the hydroxyapatite coating on the fixation of implants. Mechanical and histomorphometric results

We inserted two hydroxyapatite (HA)-coated implants with crystallinities of either 50% (HA-50%) or 75% (HA-75%) bilaterally into the medial femoral condyles of the knees of 16 dogs. The implants were allocated to two groups with implantation periods of 16 and 32 weeks. They were weight-bearing and subjected to controlled micromovement of 250 microm during each gait cycle. After 16 weeks, mechanical fixation of the HA-50% implants was increased threefold as compared with the HA-75% implants. After 32 weeks there was no difference between HA-50% and HA-75%. Fixation of HA-75% increased from 16 to 32 weeks whereas that of HA-50% was unchanged. HA-50% implants had 100% more bone ingrowth than HA-75% implants after 16 weeks. More HA coating was removed on HA-50% implants compared with HA-75% implants after both 16 and 32 weeks. No further loss of the HA coating was shown from 16 to 32 weeks. Our study suggests that the crystallinity of the HA coating is an important factor in its bioactivity and resorption during weight-bearing conditions. Our findings suggest two phases of coating resorption, an initial rapid loss, followed by a slow loss. Resorbed HA coating was partly replaced by bone ingrowth, suggesting that implant fixation will be durable.

Improved bone anchorage of hydroxypatite coated implants compared with tricalcium-phosphate coated implants in trabecular bone in dogs

Tricalcium phosphate (TCP) and hydroxyapatite (HA) ceramic coatings are bioactive coatings that have been shown to stimulate bone apposition onto ceramic-coated implants. TCP and HA ceramics have well-documented differences in physical properties, but both types of ceramics are used for stimulation of bone ongrowth to cementless endo-prosthetic components clinically. However, little is known about the difference in osteoconductive properties between these coatings when inserted into trabecular bone in a controlled experimental situation. Unloaded cylindrical gritblasted titanium (Ti-6A1-4V) implants (6 x 10 mm) coated with either hydroxyapatite (HA) or tricalcium phosphate (TCP) ceramic were inserted into the proximal humerus of 20 skeletally mature dogs. The implants were initially surrounded by a 2 mm gap. Each animal received one HA-coated implant and one TCP-coated implant. All dogs were sacrificed 6 weeks after surgery. Results were evaluated by histomorphometry and mechanical push-out test. Push-out tests demonstrated that HA-coated implants were 10-fold stronger fixated in comparison to TCP-coated implant. Bone ongrowth was significantly higher for HA-coated implants compared to TCP-coated implants. Bone volume in the gap showed a tendency to less bone volume around HA-coated implants compared to TCP-coated implants but this difference was insignificant. As expected almost all of the TCP coating were resorbed after 6 weeks and almost none of the HA coating. HA-coated implants with a grit-blasted surface provide a favorable early mechanical implant anchorage most likely due to superior ceramic stability compared to TCP-coated implants.

Pharmacokinetically guided dose escalation of carboplatin in epithelial ovarian cancer: effect on drug-plasma AUC and peripheral blood drug-DNA adduct levels

BACKGROUND

Platinum based drugs are active agents in epithelial ovarian cancer and increased platinum drug dose intensity is thought to lead to improved survival, because of the largely untested assumption that increased dose intensity results in an increased interaction of the platinum drug with its target, DNA. In a previously reported phase I trial (Lind et al., J Clin Oncol 1996; 14: 800-5), carboplatin dose intensity was increased by the use of G-CSF to support the bone marrow and using pharmacokinetically-guided carboplatin dosing. The objectives of this study were to validate the carboplatin dosing formula during high dose intensity therapy and evaluate the relationship between systemic carboplatin exposure and Pt-DNA adduct levels in peripheral blood leucocytes.

PATIENTS AND METHODS

A total of 17 patients were studied over four levels of dose intensification. The carboplatin dose was calculated using the 'Calvert formula'. Levels of drug-target interaction in peripheral blood leukocytes were measured using an immunoassay based on a monoclonal antibody that recognises DNA-platinum adducts. Pharmacokinetic measurements were carried out using a previously validated single sample method.

RESULTS

The area under the curve of concentration of unbound carboplatin in plasma versus time (AUC) for target AUC values of 5, 7 and 9 mg/ml x min were: 5.6 +/- 1.0, 7.3 +/- 0.7 and 9.8 +/- 0.5 mg/ml x min (mean +/- S.D.). There was a good correlation between target and achieved dose intensities (r2 = 0.899) and the slope of the linear regression line was 0.95 (+/- 0.09 SD) not significantly different to 1.0 (P > 0.6). The levels of immunoreactive DNA adducts were not detectable at a target AUC of 5 mg/ml x min but increased progressively at the higher AUC levels. Accumulation of adducts between courses was not detected.

CONCLUSIONS

Pharmacokinetically-based carboplatin dosing during high intensity therapy accurately predicted the dose required to achieve a target AUC and resulted in consistent patient exposure to active drug. During the dose escalation study, peripheral blood leucocyte DNA platinum-DNA adduct levels were positively related to drug dose and drug AUC.

Carboplatin and paclitaxel, alone and in combination: dose escalation, measurement of renal function, and role of the p53 tumor suppressor gene

In this pharmacokinetic and dose-escalation study of the carboplatin/paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) combination, patients were randomly assigned to receive paclitaxel either as a 1-hour or a 3-hour infusion. The 1-hour infusion was feasible, with maximum tolerated doses similar to those previously reported for a 3-hour infusion. Using patients' age, height, plasma creatinine, and plasma creatine kinase provided an improved estimate of the glomerular filtration rate compared with the more traditional creatinine-based formulas according to population analysis of data derived from glomerular filtration rate estimates performed by an isotope method. Studies of the p53 gene sequence of ovarian tumors at diagnosis suggest that p53 mutations are a potent predictor of response to subsequent treatment with carboplatin.

Can autologous bone culture predict spinal fusion capacity?

The capacity of the individual patient to initiate osteoblast proliferation as a predictor for successful lumbar spinal fusion has not yet been reported. The objectives of this study were, first, to analyze the relationship between in vitro osteoblast proliferation and clinical bony fusion in the individual patient in order to predict the fusion outcome and, second, to measure the effect of preoperative tobacco smoking on osteoblast proliferation. Sixty-one patients (mean age 46 years) underwent posterolateral lumbar fusion in the period 1994-1995. Thirty-eight patients received CD pedicle screw implants and 23 received posterolateral fusions alone. During surgery, autogenous iliac bone was harvested and 1 g of trabecular bone without blood or bone marrow was then isolated for cell culturing. The cultures were classified as excellent (confluence within 4 weeks), good (confluence between 4 and 6 weeks) and poor (no or poor growth). Spine fusion was evaluated by two independent observers from plain anterior-posterior, lateral, and flexion/extension radiographs taken 1 year postoperatively, and the functional outcome was measured by the Dallas Pain Questionnaire (DPQ). Twenty-three patients had excellent, 19 good, and 19 poor in vitro osteoblast proliferation. Bony fusion was obtained in 77% of patients: 83% in the CD instrumentation group and 70% in the non-instrumentation group (NS). There was no significant correlation between osteoblast proliferation and spinal fusion or functional outcomes when analyzing the CD instrumentation and non-instrumentation groups together or separately. Elderly patients had a significantly poorer osteoblast proliferation than younger patients (P < 0.008). Preoperative tobacco consumption had no discernible effect on osteoblast proliferation, and no correlation between smoking and fusion was found. Further refinement of autologous osteoblast culturing may provide a biological tool for selection of patients who require biological enhancement of their bone fusion capacity. The poorer osteoblast proliferation related to advanced age supports the important negative biological influence of age on bony fusion. However, with more sensitive testing and better discrimination, other results are possible - or can in any event not be excluded.

Growth factor stimulation of bone healing. Effects on osteoblasts, osteomies, and implants fixation

Bone tissue has been shown to contain numerous cell-to-cell signalling peptides called growth factors. These growth factors are thought to have important regulating effects for bone remodeling and bone healing, due to their potent effects on bone cell metabolism. In vivo studies over the last half decade have demonstrated that growth factors candidates for future clinical use in orthopedic surgery. In numerous clinical situations enhanced bone formation and bone healing could lead to improved results of surgical procedures. This thesis describes the most important bone growth factors and their actions in vitro and in vivo. In vitro investigations of growth factor effects on osteoblast chemotaxis and metabolism are described as well as in vivo studies with growth factor stimulation of fracture healing and bone healing to prosthetic-like implants. In vitro results: Several growth factors exhibited chemotactic effects towards human osteoblasts. TGF-beta 1 and PDGF-BB had the strongest chemotactic effects, whereas PDGF-AA, IGF-1, and IGF-2 had less but significant chemotactic effects towards human osteoblasts. TGF-beta 1 exhibited the highest chemotactic potency with maximal activity at 100 pg/mL, whereas the other growth factors had maximal effects at 10-100 ng/mL. BMP-2 was found to have chemotactic effects toward human osteoblasts, human bone marrow osteoprogenitor cells, and U2-OS osteosarcoma cells. BMP-4 and BMP-6 were without any chemotactic effects towards these celltypes. Human bone marrow osteoprogenitor cells were the most responsive celltype to BMP-2 stimulation. Growth factor combinations resulted in synergic stimulative effects on different metabolic functions on human osteoblasts. Combinations with TGF-beta 1 and PDGF-BB strongly stimulated proliferation and chemotaxis. Combinations with TGF-beta 1, PDGF-BB and BMP-2 strongly stimulated an osteoblast differentiation parameter (alkaline phosphatase activity). The different growth factor combinations had no effect on collagen synthesis in human osteoblasts. In vivo results: Continuous application of 1 and 10 micrograms natural TGF-beta to a plated tibial osteotomy in rabbits increased mechanical bending strength and callus formation at 6 weeks observation. Diaphyseal cortical bone remodeling was not affected by the local growth factor application. In a dog model with unloaded implants surrounded by a gap, 0.3 microgram rhTGF-beta 1 adsorbed to gritblasted tricalcium phosphate coated implants, was able to enhance mechanical fixation, bone ingrowth and gap bone formation. 3.0 micrograms rhTGF-beta 1 had less but significant stimulative effect. In a weight-loaded model, 0.3 microgram rhTGF-beta 1, adsorbed to gritblasted tricalcium phosphate coated implants, was able to enhance bone ingrowth, without enhancement of mechanical fixation. In the unloaded model, 0.3 microgram rhTGF-beta 1, adsorbed to gritblasted hydroxyapatite coated implants, was able to enhance bone ingrowth, without enhancement of mechanical fixation. 3.0 micrograms rhTGF-beta 1 had no stimulative effects. The establishment of a biological implant fixation concept with growth factor absorbed to ceramic coatings of implants was successful. These data are promising for a possible future clinical usage of growth factors, especially for enhancement of bone healing to cementless prosthetic components.

Effects of particulate debris on macrophage-dependent fibroblast stimulation in coculture

The interactions between the different cell types in periprosthetic tissue are still unclear. We used a non-contact coculture model to investigate the effects of polymethylmethacrylate (PMMA) particles and human macrophage-derived soluble mediators on fibroblast activation. Macrophages were either exposed or not exposed to phagocytosable PMMA particles, but fibroblasts were not. Increasing numbers of macrophages were tested in cocultures in which the fibroblast cell number was held constant and cultures of macrophages alone were used for comparison of cytokine release. We used the release of interleukin-1 beta (IL-1beta), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha), lysosomal enzyme and metalloproteinase activity to assess the cultivation of macrophages and fibroblasts. In cocultures, IL-6 release was increased 100-fold for both unchallenged and particle-challenged cultures when compared with macrophage cultures alone. Furthermore, particle-challenged cocultures had threefold higher IL-6 levels than unchallenged cocultures. Release of TNF-alpha was similar in cocultures and in macrophage cultures. IL-1beta release in cocultures was independent of the macrophage-fibroblast ratio. Lysosomal enzyme activity and metalloproteinase activity were increased in cocultures. Our data show that macrophages and fibroblasts in coculture significantly increase the release of IL-6 and to a less degree other inflammatory mediators; particle exposure accentuates this effect. This suggests that macrophage accumulation in fibrous tissue may lead to elevated IL-6 levels that are much higher than those caused by particle activation of macrophages alone. This macrophage-fibroblast interaction represents a novel concept for the initiation and maintenance of the inflammatory process in periprosthetic membranes.

Effects of particulate debris on macrophage-dependent fibroblast stimulation in coculture

The interactions between the different cell types in periprosthetic tissue are still unclear. We used a non-contact coculture model to investigate the effects of polymethylmethacrylate (PMMA) particles and human macrophage-derived soluble mediators on fibroblast activation. Macrophages were either exposed or not exposed to phagocytosable PMMA particles, but fibroblasts were not. Increasing numbers of macrophages were tested in cocultures in which the fibroblast cell number was held constant and cultures of macrophages alone were used for comparison of cytokine release. We used the release of interleukin-1 beta (IL-1β), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-α), lysosomal enzyme and metalloproteinase activity to assess the cultivation of macrophages and fibroblasts.

In cocultures, IL-6 release was increased 100-fold for both unchallenged and particle-challenged cultures when compared with macrophage cultures alone. Furthermore, particle-challenged cocultures had threefold higher IL-6 levels than unchallenged cocultures. Release of TNF-α was similar in cocultures and in macrophage cultures. IL-1β release in cocultures was independent of the macrophage-fibroblast ratio. Lysosomal enzyme activity and metalloproteinase activity were increased in cocultures.

Our data show that macrophages and fibroblasts in coculture significantly increase the release of IL-6 and to a less degree other inflammatory mediators; particle exposure accentuates this effect. This suggests that macrophage accumulation in fibrous tissue may lead to elevated IL-6 levels that are much higher than those caused by particle activation of macrophages alone. This macrophage-fibroblast interaction represents a novel concept for the initiation and maintenance of the inflammatory process in periprosthetic membranes.

Randomized comparison of progenitor-cell mobilization using chemotherapy, stem-cell factor, and filgrastim or chemotherapy plus filgrastim alone in patients with ovarian cancer

PURPOSE

This was the first randomized study to investigate the efficacy of peripheral-blood progenitor cell (PBPC) mobilization using stem-cell factor (SCF) in combination with filgrastim (G-CSF) following chemotherapy compared with filgrastim alone following chemotherapy.

PATIENTS AND METHODS

Forty-eight patients with ovarian cancer were treated with cyclophosphamide and randomized to receive filgrastim 5 microg/kg alone or filgrastim 5 microg/kg plus SCF. The dose of SCF was cohort-dependent (5, 10, 15, and 20 microg/kg), with 12 patients in each cohort, nine of whom received SCF plus filgrastim and the remaining three patients who received filgrastim alone. On recovery from the WBC nadir, patients underwent a single apheresis.

RESULTS

SCF in combination with filgrastim following chemotherapy enhanced the mobilization of progenitor cells compared with that produced by filgrastim alone following chemotherapy. This enhancement was dose-dependent for colony-forming unit-granulocyte-macrophage (CFU-GM), burst-forming unit-erythrocyte (BFU-E), and CD34+ cells in both the peripheral blood and apheresis product. In the apheresis product, threefold to fivefold increases in median CD34+ and progenitor cell yields were obtained in patients treated with SCF 20 microg/kg plus filgrastim compared with yields obtained in patients treated with filgrastim alone. Peripheral blood values of CFU-GM, BFU-E, and CD34+ cells per milliliter remained above defined threshold levels longer with higher doses of SCF. The higher doses of SCF offer a greater window of opportunity in which to perform the apheresis to achieve high yields.

CONCLUSION

SCF (15 or 20 microg/kg) in combination with filgrastim following chemotherapy is an effective way of increasing progenitor cell yields compared with filgrastim alone following chemotherapy.

In vitro, in vivo, and tissue retrieval studies on particulate debris

The biologic effects of wear debris are an important factor limiting the longevity of total joint replacements. In vivo, in vitro, and tissue retrieval studies have underlined a central role for the macrophage in the etiology of loosening and periprosthetic osteolysis. Wear particles from the materials used for total joint replacement activate macrophages to secrete proinflammatory factors. Complex interactions between macrophages and other cells stimulate bone resorption and suppress bone formation at the prosthetic interface. To improve the long term outcome of joint replacements, future research must find innovative approaches to minimize the production and biologic effects of wear debris.