Endoprosthetic replacement of the proximal tibia for oncological conditions

Aims

The proximal tibia (PT) is the anatomical site most frequently affected by primary bone tumours after the distal femur. Reconstruction of the PT remains challenging because of the poor soft-tissue cover and the need to reconstruct the extensor mechanism. Reconstructive techniques include implantation of massive endoprosthesis (megaprosthesis), osteoarticular allografts (OAs), or allograft-prosthesis composites (APCs).

Methods

This was a retrospective analysis of clinical data relating to patients who underwent proximal tibial arthroplasty in our regional bone tumour centre from 2010 to 2018.

Results

A total of 76 patients fulfilled the inclusion criteria and were included in the study. Mean age at surgery was 43.2 years (12 to 86 (SD 21)). The mean follow-up period was 60.1 months (5.4 to 353). In total 21 failures were identified, giving an overall failure rate of 27.6%. Prosthesis survival at five years was 75.5%, and at ten years was 59%. At last follow-up, mean knee flexion was 89.8° (SD 36°) with a mean extensor lag of 18.1° (SD 24°). In univariate analysis, factors associated with better survival of the prosthesis were a malignant or metastatic cancer diagnosis (versus benign), with a five- and ten-year survival of 78.9% and 65.7% versus 37.5% (p = 0.045), while in-hospital length of stay longer than nine days was also associated with better prognosis with five- and ten-year survival rates at 84% and 84% versus 60% and 16% (p < 0.001). In multivariate analysis, only in-hospital length of stay was associated with longer survival (hazard ratio (HR) 0.23, 95% confidence interval (CI) 0.08 to 0.66).

Conclusion

We have shown that proximal tibial arthroplasty with endoprosthesis is a safe and reliable method for reconstruction in patients treated for orthopaedic oncological conditions. Either modular or custom implants in this series performed well.

Cite this article: Bone Jt Open 2022;3(9):733–740.

Extra-abdominal desmoid tumor fibromatosis: a multicenter EMSOS study

Background

Extra-abdominal desmoid tumor fibromatosis (DTF) is a rare, locally aggressive soft tissue tumour. The best treatment modality for this patient cohort is still object of debate.

Questions/purpose

This paper aimed to (1) to compare the outcomes of DTF after different treatment modalities, (2) to assess prognostic factors for recurrence following surgical excision, and (3) to assess prognostic factors for progression during observation.

Methods

This was a retrospective multicenter study under the patronage of the European Musculoskeletal Oncology Society (EMSOS). All seven centres involved were tertiary referral centres for soft tissue tumours. Baseline demographic data was collected for all patients as well as data on the diagnosis, tumour characteristics, clinical features, treatment modalities and whether they had any predisposing factors for DTF.

Results

Three hundred eighty-eight patients (240 female, 140 male) with a mean age of 37.6 (±18.8 SD, range: 3–85) were included in the study. Two hundred fifty-seven patients (66%) underwent surgical excision of ADF, 70 patients (18%) were observed without therapy, the residual patients had different conservative treatments. There were no significant differences in terms of tumour recurrence or progression between the different treatment groups. After surgical excision, younger age, recurrent disease and larger tumour size were risk factors for recurrence, while tumours around the shoulder girdle and painful lesions were at risk of progression in the observational group.

Conclusion

Local recurrence rate after surgery was similar to progression rates under observation. Hence, observation in DTF seems to be justified, considering surgery in case of dimensional progression in 2 consecutive controls (3 and 6 months) and in painful lesions, with particular attention to lesions around the shoulder girdle.

Multimodal Treatment in Pelvic Ewing Sarcoma: A Prognostic Factor Analysis

BACKGROUND

Although multidisciplinary therapies have improved local control and overall survival in Ewing sarcoma (ES), the prognosis of pelvic lesions remains markedly worse than that of limb ES.

METHODS

We retrospectively evaluated the influence of the type of local treatment, margins, necrosis and sacrum involvement on overall survival (OS) and disease-free survival (DFS) in a series of 21 non-metastatic pelvic ES.

RESULTS

The average follow-up was 46.3 months (range 3-156). Only one patient had recurrence, at 11 months after surgery. Eight patients showed pulmonary metastasis and five showed bone metastases. Necrosis was the only significant prognostic factor for overall survival at 5 years (p=0.0132) and disease-free survival (p=0.0086). Overall survival at 5 years was 40.1%.

CONCLUSION

Local control in pelvic Ewing sarcoma is comparable for patients treated with surgery (S), surgery plus radiotherapy (S/RT), or definitive radiotherapy (RT). The combination of surgery plus radiotherapy could be indicated in cases of large tumor, a poor necrosis response (< 90%), or an inadequate margin with involvement of the sacrum. A poor response to neoadjuvant therapy is a significant risk factor for both local control and overall survival.

Liposarcoma: Clinico-pathological analysis, prognostic factors and survival in a series of 307 patients treated at a single institution

BACKGROUND AND OBJECTIVES

Liposarcoma (LPS) is a malignant mesenchymal tumor and the most common soft tissue sarcoma. Four different subtypes are described: well differentiated (WD) LPS or atypical lipomatous tumor (ALT), dedifferentiated (DD) LPS, myxoid LPS, and pleomorphic LPS (PLS). The objective of the study was to investigate prognostic factors and clinical outcome of liposarcoma.

METHODS

We retrospectively examined the clinico-pathological features of a series of 307 patients affected by Liposarcoma at a mean follow-up of 69 months (range 6-257). ALT/WD LPS were analyzed separately. The influence of site, size, type of presentation, grading, histotype and local recurrence on local and systemic control and survival was assessed.

RESULTS

The statistical analysis indicated that only surgical margins represented a significant prognostic factor for local recurrence in ALT/WD LPS (P = 0.0007) and other subtypes of LPS (P = 0.0055). In myxoid, PLS and DD LPS, significant prognostic factors for metastasis free survival (MFS) were surgical margins (P = 0.0009), size of the tumor (P = 0.0358), histology (P = 0.0117) and local recurrence (P = 0.0015). In multivariate analysis, surgical margins (0.0180), size (0.0432) and local recurrence (0.0288) correlated independently with MFS. Margins (P = 0.0315), local recurrence (P = 0.0482) and metastases (P < 0.0001) were prognostic factors for overall survival (OS).

CONCLUSION

Marginal surgery can be an accepted treatment for ALT/WD LPS. In other liposarcoma subtypes (Myxoid, DD, PLS) wide or radical surgery is recommended as the margins significantly influence local recurrence-free survival (LRFS), metastasis-free survival (MFS) and overall survival (OS). Local recurrence and metastases were significant prognostic factors for OS.

Allograft Reconstruction of the Extensor Mechanism after Resection of Soft Tissue Sarcoma

INTRODUCTION

Soft tissue tumors around the knee joint still pose problems for the excision and subsequent reconstruction.

METHODS

In the 6 included patients the soft tissue sarcoma has its base on the anterior surface of the extensor mechanism and expands towards the skin. The entire extensor apparatus (quadriceps tendon, patella, and patellar tendon) was resected and replaced by a fresh-frozen allograft.

RESULTS

The mean follow-up was 6.7 years (range: 2-12.4 years). In two patients a local recurrence occurred, resulting in a 5-year local recurrence-free rate of 66.7% (95% CI: 19.5%-90.4%). Distant metastases were found in 4 patients resulting in a 5-year metastasis-free rate of 33.3% (95% CI: 4.6%-67.5%). Two patients underwent at least one revision surgery, including one patient in whom the allograft had to be removed. According to the ISOLS function score 24.7 points (range: 19-28 points) were achieved at the last follow-up. The mean active flexion of the knee joint was 82.5° (range: 25-120°) and a mean extension lag of 10° (range: 0-30°) was observed.

CONCLUSIONS

The replacement of the extensor mechanism by an allograft is a reasonable option, allowing wide margins and restoration of active extension in most patients.

TRIAL REGISTRATION

The presented study is listed on the ISRCTN registry with trial number ISRCTN63060594.

Allograft-prosthetic composite versus megaprosthesis in the proximal tibia-What works best?

Modular megaprosthesis (MP) and allograft-prosthetic composite (APC) are the most commonly used reconstructions for large bone defects of the proximal tibia. The primary objective of this study was to compare the two different techniques in terms of failures and functional results. A total of 42 consecutive patients with a mean age of 39.6 years (range 15-81 years) who underwent a reconstruction of the proximal tibia between 2001 and 2012 were included. Twenty-three patients were given an MP, and 19 patients received an APC. There were nine reconstruction failures after an average follow-up of 62 months: five in the MP group and four in the APC group (p=0.957). The 10-year implant survival rate was 78.8% for the MP and 93.7% for the APC (p=0.224). There were no relevant differences between the two groups in functional results. Both MP and APC are valid and satisfactory reconstructive options for massive bone defects in the proximal tibia. In high-demanding patients with no further risk factors, an APC should be considered to provide the best possible functional result for the extensor mechanism.

Pre-operative diclofenac HPβCD for pain control of needle biopsy in musculoskeletal neoplasm: preliminary results

Needle biopsy is the main standard method used for diagnosis of musculoskeletal tumors of the limbs and superficial trunk. Pain control during this procedure is through the use of Local Anaestetic (L.A.). In order to achieve a complete pain control in our cases, recently we started using diclofenac HPβCD 50 mg via s.c. preoperativly. We present the clinical results of a non-randomized study of two eterogeneous groups of patients: "Experimental" Group (1): diclofenac HPβCD 50 mg via s.c. one hour before surgical procedure, local anesthesia and ev. diclofenac HPβCD 50 mg via s.c. 12 hours postoperative; "Conventional" Group (2): local anesthesia and ev. postoperative tramadol 100 mg via oral for pain control. In October 2014, at the Department of Orthopedic Oncology and Reconstructive Surgery of Florence, 37 musculoskeletal biopsies for a bone or a soft tissue lesion were performed. Exclusion criteria for this study were: known allergies to lidocaine, diclofenac, tramadol; known gastric or duodenal ulcers; known gastrointestinal bleed or perforation; refusal of the patients to collaborate. For one or more of these reasons, 6 patients were excluded from this study. In the Group 1, 10 patients (59%) referred no pain during the surgical procedure (8/14 biopsies on soft tissue and 2/3 on bone). In 5 cases (29%) no exacerbation of previous chronic pain, and in 2 cases (12%) a progression of local pain after biopsy (average 1 points higher in the VAS). In Group 2, only 6 patients (42%) did not have any pain during the procedure, 4 (29%) no exacerbation of previous chronic pain and 4 (29%) a progression of local pain (average 2 points higher in the VAS). Despite similar results in both Groups, Group 1 seemed to have a mild better control of perioperative pain. The use of diclofenac HPβCD 50 mg preoperative seems to be a rational approach for minimizing perioperative pain and the preliminary data of our study seem encouraging. Obviously many bias are present in this study (small numbers of cases, heterogeneity of diseases, association with local anesthetic, non-randomized study, comparison between preoperative versus postoperative treatment) and this cannot absolutely be considerate as definitive conclusions.

Comparison between single-and double-bundle anterior cruciate ligament reconstruction: a prospective, randomized, single-blinded clinical trial

BACKGROUND

Double-bundle ACL reconstruction popularity is increasing with the aim to reproduce native ACL anatomy and improve ACL reconstruction outcome. However, to date, only a few randomized clinical studies have been published.

PURPOSE

The aim of this study was to prospectively compare the clinical results of single- and double-bundle ACL reconstruction.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Seventy patients with a chronic unilateral ACL rupture who underwent arthroscopically assisted ACL reconstruction using a hamstring graft were randomized to receive a single- (SB) or double-bundle (DB) reconstruction. Both groups were comparable with regard to preoperative data. A double-incision surgical technique was adopted in both groups. The graft was fixed by looping the hamstring tendons around a bony (DB) or a metallic (SB) bridge on the tibial side and with interference screws reinforced with a staple on the femur. The same rehabilitation protocol was adopted. Outcome assessment was performed by a blinded, independent observer using the visual analog scale (VAS) score, the new International Knee Documentation Committee (IKDC) form, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and KT-1000 arthrometer evaluation.

RESULTS

All the patients reached a minimum follow-up of 2 years. No differences between the 2 groups were observed in terms of KOOS and IKDC subjective score. A statistically significant difference in favor of the DB group was found with the VAS (P < .03). The objective IKDC final scores showed statistically significantly more "normal knees" in the DB group than in the SB group (P = .03). There was 1 stability failure in the DB group and 3 in the SB group. The KT-1000 arthrometer data showed a statistically significant decrease in the average anterior tibial translation in the DB group (1.2 mm DB vs 2.1 mm SB; P < .03). The incidence of a residual pivot-shift glide was 14% in DB and 26% in SB (P = .08).

CONCLUSION

In the 2-year minimum follow-up, DB ACL reconstructions showed better VAS, anterior knee laxity, and final objective IKDC scores than SB. However, longer follow-up and accurate instrumented in vivo rotational stability assessment are needed.

Rotational position of femoral and tibial components in TKA using the femoral transepicondylar axis

Proper femoral and tibial component rotational positioning in TKA is critical for outcomes. Several rotational landmarks are frequently used with different advantages and limitations. We wondered whether coronal axes in the tibia and femur based on the transepicondylar axis in the femur would correlate with anteroposterior deformity. We obtained computed tomography scans of 100 patients with arthritis before they underwent TKA. We measured the posterior condylar angle on the femoral side and the angle between Akagi's line and perpendicular to the projection of the femoral transepicondylar axis on the tibial side. On the femoral side, we found a linear relationship between the posterior condylar angle and coronal deformity with valgus knees having a larger angle than varus knees, ie, gradual external rotation increased with increased coronal deformity from varus to valgus. On the tibial side, the angle between Akagi's line and the perpendicular line to the femoral transepicondylar axis was on average approximately 0 degrees , but we observed substantial interindividual variability without any relationship to gender or deformity. A preoperative computed tomography scan was a useful, simple, and relatively inexpensive tool to identify relevant anatomy and to adjust rotational positioning. We do not, however, recommend routine use because on the femoral side, we found a relationship between rotational landmarks and coronal deformity.

The effects of different tensioning strategies on knee laxity and graft tension after double-bundle anterior cruciate ligament reconstruction

BACKGROUND

Double-bundle anterior cruciate ligament reconstruction replicates the 2 functional bundles of the native ligament, the posterolateral and the anteromedial, to control anteroposterior and rotational laxity.

HYPOTHESIS

Double-bundle anterior cruciate ligament reconstruction laxity should be affected by the way grafts are tensioned.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fourteen intact cadaveric knees were instrumented in a 6 degree of freedom rig, and kinematics throughout flexion-extension were recorded with an electromagnetic system under a 90-N anterior force or a 5-N.m internal rotation torque. Anteromedial and posterolateral bundle bovine extensor tendon grafts were fixed to load cells on the tibia, and tension was adjusted to match the intact knee anteroposterior laxity with 3 different protocols: (1) anteromedial bundle first and then posterolateral bundle at 90 degrees and 20 degrees of flexion, respectively; (2) posterolateral bundle first and then anteromedial bundle at 20 degrees and 90 degrees of flexion, respectively; and (3) both bundles together at 20 degrees of flexion. Finally, a single-bundle graft positioned at 10 o'clock was tensioned at 20 degrees of flexion.

RESULTS

Lower graft tensions were required to match intact knee laxity in double-bundle anterior cruciate ligament reconstruction. Tension patterns with knee flexion were independent from the tensioning protocol. Protocols 1 and 2 overconstrained anteroposterior laxity, whereas protocol 3 matched intact knee anteroposterior laxity throughout the range of motion. The single-bundle reconstructions had excess anteroposterior laxity in flexion. Rotations were better restored with double-bundle protocols 2 and 3.

CONCLUSION

Knee laxity after double-bundle anterior cruciate ligament reconstruction is affected by the sequence in which the grafts are tensioned.

CLINICAL RELEVANCE

Double-bundle anterior cruciate ligament reconstruction ensures better laxity restoration than does single bundle when both bundles are fixed together.

Double-bundle "anatomic" anterior cruciate ligament reconstruction: a cadaveric study of tunnel positioning with a transtibial technique

PURPOSE

The aim of this study was to examine whether a double-bundle anterior cruciate ligament (ACL) reconstruction with a transtibial approach could position the tibial and femoral tunnels accurately in the native bundle attachments.

METHODS

In 21 fresh-frozen knees the tibial and femoral attachments of the anteromedial (AM) and posterolateral (PL) bundles were outlined. The AM tibial tunnel guidewire was drilled with the 65 degree Howell tibial guide (Arthrotek, Warsaw, IN) located against the femur in the extended knee. The PL tibial wire was drilled through a prototype attachment to the Howell guide. Of the knees, 14 were available for the femoral part of the study. The AM femoral guidewire used an aimer offset 3 mm from the over-the-top position. The PL wire was drilled transtibially at 70 degrees of flexion, with external rotation and posterior drawer loads being applied. The plateaus and condyles were photographed and the wire positions measured.

RESULTS

With regard to the tibia, 17 of 21 AM wires were in the AM bundle attachment (at 61% and 36% of the natural ACL posteroanterior and mediolateral length, respectively) and 19 of 21 PL wires were in the PL bundle attachment (at 28% and 36% of the posteroanterior and mediolateral length, respectively). With regard to the femur, 12 of 14 AM wires and 9 of 14 PL wires were in the correct native bundle attachment. The AM wire was 3% more shallow than the center of the AM attachment (P = .03) and 6% more superior (P < .001), where 100% was the diameter of the posterior lateral condyle. The PL wire was 4% more shallow than the center of the PL attachment (P = .026) and 6% more superior (P < .001).

CONCLUSIONS

Anatomic and reproducible tibial guidewire positioning was achieved. Femoral wires were reproducibly positioned, but both were superior to and more shallow than the natural ACL bundle attachments, so further development or a different approach is appropriate.

CLINICAL RELEVANCE

The double-bundle reconstruction aims to restore anterior drawer and rotational stability. This technique ensures anatomic tibial positioning. Further improvements are needed with regard to the femur.

Single-and double-incision double-bundle ACL reconstruction

Double-bundle anterior cruciate ligament (ACL) reconstruction is intended to replicate the anatomy and the function of the anteromedial and posterolateral bundles of the native ACL to improve patients' satisfaction and knee stability. We prospectively assigned 75 consecutive patients with an isolated ACL lesion to one of three sequential groups of 25 patients each. Group I received a single-bundle, single-incision transtibial ACL reconstruction. Groups II and III received a double-bundle reconstruction with a single-incision transtibial technique or a double-bundle, twoincision outside-in technique, respectively. We obtained subjective International Knee Documentation Committee and Knee Injury and Osteoarthritis Outcome Score evaluations and objective International Knee Documentation Committee scores and KT-1000 measurements preoperatively and at followup. All patients reached a minimum followup of 2 years. KT side-to-side difference in Groups I, II, and III were 2.4, 1.6 and 1.4 mm, respectively. Group III had fewer patients with a positive pivot shift than Group I. The double-bundle double-incision outside-in ACL reconstruction resulted in improved anteroposterior stability and less residual pivot shift than single-incision single-bundle technique.

High volume and low concentration of anaesthetic solution in the perivascular interscalene sheath determines qualityof block and incidence of complications

BACKGROUND AND OBJECTIVE

In the perivascular sheath of the brachial plexus, the volume of anaesthetic solution determines the quality of anaesthetic cover. Fibrous septa may divide the perivascular space into compartments, leading to inadequate diffusion of the anaesthetic solution. The aim of our study was to obtain good anaesthesia and less complications using high volume of low concentration anaesthetic solution, overcoming the obstacle of the septa with a double approach to the scalene sheath.

METHODS

Sixty patients scheduled for shoulder capsuloplasty received both Winnie interscalene brachial plexus block and Pippa proximal cranial needle approach. The patients were randomly assigned to two groups. A constant dose of local anaesthetic was administered to each group: Group I (30 patients) received high volume (60 mL of anaesthetic solution) and Group II (30 patients) received low volume of solution (30 mL of anaesthetic solution). Sensory and motor block in the upper limb and complications were evaluated.

RESULTS

In all the patients the quality of anaesthesia obtained at the surgical site was excellent. In Group I also the areas supplied by the medial cutaneous nerves of the arm and forearm, ulnar, median and radial nerves were blocked (P < 0.002). Complications were only observed in Group II and consisted of bradycardia and hypotension (66% of the patients) and phrenic nerve paresis (27% of the patients).

CONCLUSIONS

The lower concentration of the anaesthetic solution avoids complications while increased volume provides good analgesic cover. The combination of the Winnie interscalene plexus block and the Pippa proximal cranial needle approach should contribute to fill up the scalene sheath overcoming the septa obstacles.

Femoral attachment of the anterior cruciate ligament

Endoscopic anterior cruciate ligament (ACL) reconstruction is one of the most popular orthopaedic procedures. Correct tunnel positioning is a prerequisite to success. Current surgical techniques are unable to duplicate the complex anatomy and function of the native ACL. Surgery mainly aims at restoring anteroposterior laxity. The ACL is not isometric and only a few fibers are nearly isometric over the full range of motion. However, a nearly isometric behaviour of the ACL graft is desirable. Isometry is mainly influenced by femoral attachment; thus the femoral tunnel position has a greater effect than the tibial on graft length changes. The purpose of this article is to describe the anatomy of the femoral ACL insertion and to discuss the surgical techniques used to replicate it.

Validation of the 65 degrees Howell guide for anterior cruciate ligament reconstruction

PURPOSE

To study in cadaver knees the position of the tibial tunnel in anterior cruciate ligament (ACL) reconstruction using the 65 degrees Howell guide (Arthrotek, Ontario, CA).

TYPE OF STUDY

Controlled laboratory study in vitro.

METHODS

Twenty-one fresh-frozen cadaver knees were used. The ACL was resected and its tibial attachment was demarcated. To drill the guidewire, we used the Howell 65 degrees tibial guide, which references off of the intercondylar roof in extension to avoid impingement. The intra-articular position of the wire was digitized with a digital camera and referred to a transverse axis passing through the over-the-back position and a sagittal axis passing through the lateral aspect of the medial spine. The percentage position of the wire within the ACL attachment was also calculated, taking the posterior and medial limits as the 0% positions.

RESULTS

All the wires were within the ACL attachment: 17 were in the ACL posterolateral bundle attachment and the other 4 in the anteromedial. The average distance of the wire from the transverse and sagittal axes was 12 mm (SD, 3 mm) anterior and 1 mm (SD, 1 mm) lateral, respectively. The wire was positioned at 38% (SD, 16%) of the length of the ACL attachment and at 40% (SD, 17%) of the width. Eighty percent of the wires were positioned at between 35% and 48% of the attachment length.

CONCLUSIONS

The 65 degrees Howell guide, which positions the tibial tunnel in extension to avoid roof impingement, ensures anatomic positioning of the graft on the tibial side and reproducibility can be expected.

CLINICAL RELEVANCE

This study proves that a commonly used drill guide succeeds in placing the ACL graft in the tibial anatomic attachment.

Anterior cruciate ligament reconstruction with double-looped semitendinosus and gracilis tendon graft directly fixed to cortical bone: 5-year results

Forty-three patients who had undergone an anterior cruciate ligament (ACL) reconstruction using a doubled semitendinosus and gracilis graft were prospectively reviewed at 5-year follow-up. All had suffered subacute or chronic tears of the ligament. At surgery, the femoral tunnel was drilled first through the antero-medial portal. The correct position of the femoral and tibial guide wire was checked fluoroscopically. A cortical fixation to the bone was achieved in the femur with a Mitek anchor, directly passing the two tendons in the slot of the anchor, and in the tibia with an RCI screw, supplemented with a spiked washer and bicortical screw. Rehabilitation was aggressive, controlled and without braces. The International Knee Documentation Committee (IKDC) form, KT-1000 arthrometer, and Cybex dynamometer were employed for clinical evaluation. A radiographic study was also performed. At the 5-year follow-up all the patients had recovered full range of motion and 2% of them complained of pain during light sports activities. Four patients (9.5%) reported giving-way symptoms. The KT-1000 side-to-side difference was on average 2.1 mm at 30 lb, and 68% of the knees were within 2 mm. The final IKDC score showed 90% satisfactory results. There was no difference between the 2-year and 5-year evaluations in terms of stability. Extensor and flexor muscle strength recovery was almost complete (maximum deficit 5%). Radiographic study showed a tunnel widening in 32% of the femurs and 40% of the tibias. A correlation was found between the incidence of tibial tunnel widening and the distance of the RCI screw from the joint (the closer the screw to the joint, the lower the incidence of widening). In conclusion, we can state that, using a four-strand hamstring graft and a cortical fixation at both ends, we were able to achieve satisfactory 5-year results in 90% of the patients.

Type I interferons and IL-12: convergence and cross-regulation among mediators of cellular immunity

Therapeutic use of type I IFN (IFN-alpha/beta) has become common. Many of the diverse diseases targeted are marked by pathogenetic abnormalities in cell-mediated immunity (CMI), these cellular immune responses either causing injury to the host, lacking sufficient vigor for virus or tumor clearance, or both. In general, therapeutic efficacy is limited. It is thus notable that the pleiotropic effects of type I IFN on CMI remain poorly understood. We characterized the effects of type I IFN on the production of IL-12, the central immunoregulatory cytokine of the CD4(+) T cell arm of CMI. We show that type I IFN are potent inhibitors of IL-12 production by human monocytes/macrophages. The underlying mechanism involves transcriptional inhibition of the IL-12p40 gene, marked by down-regulation of PU.1 binding activity at the upstream Ets site of the IL-12p40 promoter. Type I IFN have previously been shown to be able to substitute for IL-12 in driving IFN-gamma production from T and NK cells. The ability of IFN-alpha/beta to suppress IL-12 production while up-regulating IFN-gamma production suggests a possible mechanistic basis for the difficulties of employing these cytokines in diseases involving abnormalities of CMI.

Potent suppression of IL-12 production from monocytes and dendritic cells during endotoxin tolerance

Endotoxin tolerance, the down-regulation of a subset of endotoxin-driven responses after an initial exposure to endotoxin, may provide protection from the uncontrolled immunological activation of acute endotoxic shock. Recent data suggest, however, that the inhibition of monocyte/macrophage function associated with endotoxin tolerance can lead to an inability to respond appropriately to secondary infections in survivors of endotoxic shock. IL-12 production by antigen-presenting cells is central to the orchestration of both innate and acquired cell-mediated immune responses to many pathogens. IL-12 has also been shown to play an important role in pathological responses to endotoxin. We therefore examined the regulation of IL-12 during endotoxin tolerance. Priming doses of lipopolysaccharide ablate the IL-12 productive capacity of primary human monocytes. This suppression of IL-12 production is primarily transcriptional. Unlike the down-regulation of TNF-alpha under such conditions, the mechanism of IL-12 suppression during endotoxin tolerance is not dependent upon IL-10 or transforming growth factor-beta, nor is IL-12 production rescued by IFN-gamma or granulocyte-macrophage colony-stimulating factor. Of note, human dendritic cells also undergo endotoxin tolerance, with potent down-regulation of IL-12 production. Endotoxin tolerance-related suppression of IL-12 production provides a likely mechanism for the anergy seen during the immunological paralysis which follows septic shock.

Kinesin movement on glutaraldehyde-fixed microtubules

Glutaraldehyde-cross-linked microtubules were investigated as substrates for kinesin motility. Microtubules, formed in vitro from chicken brain tubulin, were stabilized with Taxol and chemically fixed with glutaraldehyde. The degree of tubulin monomer cross-linking as a function of time and glutaraldehyde concentration was characterized using polyacrylamide gel electrophoresis. Atomic force microscopy of fixed microtubules indicated that the cross-linking is sufficient to stabilize the gross structure of the microtubules against air drying or a distilled water challenge. Kinesin movement on immobilized, fixed microtubules was determined using a kinesin-coated bead motility assay observed with differential interference contrast microscopy. Within measurement error, kinesin bead movement velocities were independent of the degree of microtubule cross-linking. Binding affinity, however, decreased with increased cross-linking. Although air- and water-challenged microtubules did not support kinesin motility, a dilute suspension of glutaraldehyde-fixed microtubules in buffer supported kinesin motility for at least 2 days without any substantial degradation of activity. Fixed microtubules may be useful for several applications, including affinity purification of microtubule-associated proteins and motility measurements under extreme conditions of temperature and other variables.