Chondrocyte apoptosis after simulated intraarticular fracture: a comparison of histologic detection methods

Balloon tibioplasty for tibial plateau fractures

BACKGROUND

Tibial plateau fractures are complex intra-articular injuries. The aim of treatment is to restore joint congruity and alignment. Balloon tibioplasty is a novel, minimally invasive technique to reduce the fracture and restore the continuity of the articular surface. A systematic review was performed according to the PRISMA guidelines in order to assess the outcomes from this procedure.

SOURCES OF DATA

The online databases of Pubmed, Google scholar, the Cochrane Library, EMBASE and CINAHL were searched. Articles of interest were retrieved and evaluated, including case series, randomised controlled trials and cadaver studies.

AREAS OF AGREEMENT

Eight studies (one randomised controlled trial, four case series and three cadaver studies) were included in the final review. The studies demonstrated adequate fracture reduction with favourable clinical and imaging outcomes from balloon tibioplasty. Very few complications were described.

AREAS OF CONTROVERSY

There is a small volume of literature currently available on balloon tibioplasty with an overall low level of evidence. The overall number of reported cases is also small.

GROWING POINTS

Further research is necessary, with adequately powered randomised controlled trials. Further areas of research include type of bone substitute and the use of arthroscopically assisted surgery.

Superficial zone cellularity is deficient in mice lacking lubricin: a stereoscopic analysis

Background

Lubricin, a mucinous glycoprotein secreted by synoviocytes and chondrocytes plays an important role in reducing the coefficient of friction in mammalian joints. Elevated cartilage surface friction is thought to cause chondrocyte loss; however, its quantification and methodological approaches have not been reported. We adapted a stereological method and incorporated vital cell staining to assess cellular loss in superficial and upper intermediate zones in lubricin deficient mouse cartilage.

Methods

The femoral condyle cartilage of the intact knees from lubricin wild type (Prg4^+/+), heterozygote (Prg4^+/-), and knockout (Prg4^-/-) mice was imaged using fluorescein diacetate (FDA), propidium iodide (PI), and Hoechst staining, and confocal microscopy. Three dimensional reconstructions of confocal images to a depth of 14 μm were analyzed using Matlab to determine the volume fraction occupied by chondrocytes in cartilage of both medial and lateral femoral condyles. Living chondrocyte volume fraction was defined as FDA stained chondrocyte volume/total volume of superficial + upper intermediate zone. Living and dead (total) chondrocyte volume fraction was defined as FDA + PI stained chondrocyte volume/total volume of superficial + upper intermediate zone. MicroCT provided an orthogonal measure of cartilage thickness. Immunohistology for activated caspase-3 and TUNEL staining were performed to evaluate the presence of apoptotic chondrocytes in Prg4 mutant mice.

Results

Living chondrocyte volume fraction of the medial femoral condyle was significantly lower in Prg4^-/- mice compared to Prg4^+/+ (p = 0.002) and Prg4^+/- (p = 0.002) littermates. There was no significant difference in medial condyle chondrocyte volume fraction between Prg4^+/+ and Prg4^+/- mice (p = 0.82). No significant differences were observed for the chondrocyte volume fraction for the lateral condyle (p > 0.26). Cartilage thickness increased in the medial condyle for Prg4^-/- mice compared to Prg4^+/+ (p = 0.02) and Prg4^+/- (p = 0.03) littermates, and the lateral condyle for Prg4^-/- mice compared to Prg4^+/+ (p < 0.0001) and Prg4^+/- (p < 0.0001) littermates, indicating that a multi-dimensional increase in cartilage volume did not artifactually lower the chondrocyte volume fraction in the medial condyle. Significantly higher number of caspase-3 positive cells were observed in the superficial and upper intermediate zone cartilage of the medial femoral condyle of Prg4^-/- mice compared to Prg4^+/+ (p = 0.01) and Prg4^+/- (p = 0.04) littermates, and the lateral femoral condyle of Prg4^-/- mice compared to Prg4^+/+ (p = 0.02) and Prg4^+/- (p = 0.02) littermates. There were no significant differences in TUNEL staining among different Prg4 genotypes in both condyles (p > 0.05 for all comparisons).

Conclusions

Increased Caspase-3 activation is observed in Prg4 deficient mice compared to Prg4 sufficient littermates. Absence of Prg4 induces loss of chondrocytes in the superficial and upper intermediate zone of mouse cartilage that is quantifiable by a novel image processing technique.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0967-4) contains supplementary material, which is available to authorized users.

Balloon tibioplasty for reduction of depressed tibial plateau fractures: Preliminary radiographic and clinical results

PURPOSE

In vitro studies have shown promising results for balloon-guided inflation tibioplasty. It was our hypothesis that this technique may be safe and effective for use in depressed lateral tibial plateau fracture.

METHODS

We performed a prospective study of all patients suffering from a depressed lateral tibial plateau fracture, managed in our institution with inflation tibioplasty and a resorbable calcium phosphate bone substitute injection, between January 2012 and December 2013. Twenty patients, mean age 54.3 ± 12. 8 years, suffering from a depressed lateral tibial plateau fracture (Schatzker type II and III) were included. We then aimed to evaluate at a minimum follow-up of one year: (1) the rate of complications, (2) the clinical outcome (Knee Injury and Osteoarthritis Outcome (KOO) and 12-Item Short Form Health Survey (SF-12) scores); and (3) the radiographic outcome (evaluated by CT-scan).

RESULTS

No peri-operative complications occurred. In one patient, calcium phosphate substitute was found in the infrapatellar fat pad on post-operative radiography with no clinical or radiographic consequences at one year. At one year after surgery, the KOO subscores were: Pain 80 (range 64-93), other symptoms 81.3 (69-93), daily living activities 81.9 (46-99), sport 65.83 (20-100), and quality of life 67.04 (31-100). The SF-12 activity component was 40.4 (28.6-52.2) and SF-12 mental component 47.71 (28 - 67.1). The mean depressed step-off of the lateral joint decreased from 10.7 ± 4.8 mm pre-operatively to 2.7 ± 1.7 mm post-operatively (p < 0.0001).

CONCLUSION

Our observations suggest that the use of balloon-guided inflation tibioplasty with injection of a resorbable bone substitute is safe, and results in a high rate of anatomic reduction and good clinical outcomes in patients with depressed tibial plateau fractures.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Biomarkers of Chondrocyte Apoptosis and Autophagy in Osteoarthritis

Cell death with morphological and molecular features of apoptosis has been detected in osteoarthritic (OA) cartilage, which suggests a key role for chondrocyte death/survival in the pathogenesis of OA. Identification of biomarkers of chondrocyte apoptosis may facilitate the development of novel therapies that may eliminate the cause or, at least, slow down the degenerative processes in OA. The aim of this review was to explore the molecular markers and signals that induce chondrocyte apoptosis in OA. A literature search was conducted in PubMed, Scopus, Web of Science and Google Scholar using the keywords chondrocyte death, apoptosis, osteoarthritis, autophagy and biomarker. Several molecules considered to be markers of chondrocyte apoptosis will be discussed in this brief review. Molecular markers and signalling pathways associated with chondroycte apoptosis may turn out to be therapeutic targets in OA and approaches aimed at neutralizing apoptosis-inducing molecules may at least delay the progression of cartilage degeneration in OA.

Effect of hyaluronic acid on chondrocyte apoptosis

OBJECTIVE:

To determine the percentage of apoptotic cells in a contusion model of osteoarthritis (OA) and to assess whether intra-articular injection of high doses of hyaluronic acid (HA) immediately after trauma reduces chondrocyte apoptosis.

METHODS:

Forty knees from adult rabbits were impacted thrice with a 1 kg block released through a 1 meter tall cylinder (29.4 Joules). Subsequently, 2 mL of HA was injected in one knee and 2 mL saline in the contra-lateral knee. Medication were administered twice a week for 30 days, when animals were sacrificed. Specimens were prepared for optical microscopy exam and terminal deoxynucleotidyl transferase end labeling assay (TUNEL).

RESULTS:

The apoptosis rate in the contusion model was 68.01% (± 19.73%), a higher rate than previously described. HA significantly reduced the rate of apoptosis to 53.52% (± 18.09) (p <0.001).

CONCLUSION:

Intra-articular HA administration started immediately after trauma reduces impact-induced chondrocyte apoptosis rates in rabbits.

Level of Evidence I, Experimental Study.

Inhibition of chondrocyte and synovial cell death after exposure to commonly used anesthetics: chondrocyte apoptosis after anesthetics

BACKGROUND

An intra-articular injection of local anesthetics is a common procedure for diagnostic and therapeutic purposes. It has been shown that these agents are toxic to articular cartilage and synovial tissue in a dose- and time-dependent fashion, and in some cases, they may lead to postarthroscopic glenohumeral chondrolysis (PAGCL). However, the role of apoptosis in cell death is still unclear, and the potential role of apoptosis inhibition in minimizing chondrocyte and synovial cell death has not been reported.

PURPOSE

(1) To quantify the degree of apoptotic cell death in chondrocytes and synovial cells exposed to local anesthetics, and (2) to determine whether caspase inhibition could reduce cell death.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human chondrocytes and synovial cells were expanded in vitro and exposed to normal saline, 0.5% bupivacaine, 0.5% ropivacaine, 1% lidocaine, or 1:1000 epinephrine for 90 minutes. Apoptosis was then detected at 1, 3, 5, and 7 days after exposure using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and immunohistochemistry. Apoptosis was then inhibited using the pan-caspase inhibitor z-vad-fmk. Results were normalized to normal saline controls and analyzed by generalized regression models and pairwise confidence intervals.

RESULTS

Analysis of cumulative chondrocyte apoptosis relative to controls after anesthetic exposure demonstrated more than 60% cell death with 0.5% bupivacaine and 1:1000 epinephrine. The greatest chondroprotective effect of caspase inhibition occurred with 0.5% ropivacaine. Similarly, in synovial cells, epinephrine was also very cytotoxic; however, 1% lidocaine induced the most apoptosis. Synovial cells exposed to 0.5% ropivacaine were again most sensitive to protective caspase inhibition.

CONCLUSION

Local anesthetics induce chondrocyte and synovial cell apoptosis in a time-dependent fashion, with peak apoptosis occurring 5 days after exposure. Both chondrocytes and synovial cells are most sensitive to caspase inhibition after exposure to 0.5% ropivacaine.

CLINICAL RELEVANCE

Apoptosis inhibition may be an effective strategy in minimizing chondrocyte and synovial cell death after exposure to anesthetics. Further investigation is clinically warranted.

A rat model of chondrocyte death after closed intra-articular fracture

OBJECTIVE

The development of osteoarthritis after intra-articular fractures has been described for decades, although the exact mechanical and cellular changes that occur remain poorly understood. There are several animal models to study this phenomenon, but they are mechanistically different from physiologic fractures in several important ways. This article describes a novel model that recreates the kinematics present in high-energy trauma and intra-articular fractures.

METHODS

We designed a "drop tower" for the creation of intercondylar femoral fractures in rats and tested it on cadaveric rats to determine the optimal kinetic parameters. Intra-articular fractures were then created in live rats and the animals were killed at 0, 24, and 72 hours after the fracture. Cartilage samples were obtained for live/dead staining, and the relationships among fracture time, cartilage depth, and cell viability were evaluated.

RESULTS

The model reproduced intra-articular fractures very similar to those seen in high-energy trauma, although we required significantly higher energies (3600 mJ) than those reported in other fracture models (40-200 mJ). Cartilage viability decreased with time (68% immediately after the fracture and 46% at 72 hours, P = 0.02) and increased with depth from the articular surface (47% at the surface vs. 66% in the deepest layer, P = 0.001).

CONCLUSIONS

This model is a physiologically relevant reliable method for creating intra-articular fractures in rats and can produce meaningful data about the biologic changes occurring in cartilage after injury. Cell viability decreases with time postfracture and with proximity to the articular surface.

Minocycline reduces articular cartilage damage following osteochondral injury

INTRODUCTION

Secondary injury pathways activated after chondral and osteochondral injury represent a potential target for therapies designed to minimize articular cartilage loss. The primary objective of this study was to test the potential chondroprotective effects of intra-articular minocycline following osteochondral injury.

METHODS

In vitro experiments were first performed with rabbit femoral condyles explants using an osteochondral drill injury model. Data from these in vitro experiments showed that minocycline at concentrations of 10-1000 nM decreased chondrocyte apoptosis in a dose-dependent manner. In vivo experiments were then conducted using the same injury model, studying the effects of intra-articular minocycline on chondrocyte apoptosis, chondrocyte cell number, and cartilage thickness.

RESULTS

Four days after injury, minocycline delivered daily directly into the rabbit knee joints decreased acute chondrocyte apoptosis by 56% compared to controls. Analysis performed six weeks after injury demonstrated superior chondrocyte cell number, cartilage thickness, and cartilage repair in animals receiving short-term (one-week) minocycline treatment compared to controls.

CONCLUSIONS

These data support a therapeutic approach utilizing drugs like minocycline for the acute treatment of osteochondral injuries.

Inflation osteoplasty: in vitro evaluation of a new technique for reducing depressed intra-articular fractures of the tibial plateau and distal radius

Background

Anatomic reduction of intra-articular fractures of the tibial plateau and distal radius can be difficult to achieve. Treatment goals are centered on restoring the native anatomy and articular congruency. Several surgeons in the USA have begun using an inflatable bone tamp to reduce these fracture patterns. The concept is built on the success of the tamp in kyphoplasty of the spine, but it has yet to be tested in the lab for use in the extremities. We performed an investigation into the safety and efficacy of using an inflatable bone tamp for intra-articular fracture reduction of the tibial plateau and distal radius.

Materials and methods

Paired cadaveric specimens were obtained for a total of six proximal tibias and six distal radii. Intra-articular depression-type fractures were created in all specimens. The inflatable bone tamp was then used to reduce the depression. For comparison, the tibias were fractured on the medial and lateral side and a conventional metal tamp was used on the contralateral side of the balloon. Fine-cut micro-computed tomography (CT) scans were performed on all intact specimens, which were then fractured, and again after fracture reduction. CT data was used to measure the amount of restoration of the normal anatomy and to compare the effectiveness of the balloon to conventional methods.

Results

The inflatable bone tamp was equivalent to conventional methods in large, minimally displaced fracture fragments and proved superior when comminution was present at the articular surface. No instances of overreduction or penetration into the joint were encountered with the balloon, whereas this was a common occurrence with conventional metal tamps. The inflatable tamp was successful in reducing all distal radius fractures without complication.

Conclusion

Anatomic reduction of impacted articular fractures should be the goal of any treating surgeon. In our cadaveric models, we have shown the inflatable bone tamp to be safe and effective in reducing depressed articular fractures around the tibial plateau and distal radius. The balloon offers the advantage of being minimally invasive and creating a symmetric, contained defect to hold bone filler for subchondral support.

Cryopreservation increases apoptosis in human menisci

PURPOSE

Removal of the meniscus leads to progressive degenerative arthritis of the knee on a long-term basis; therefore, meniscal allograft transplantation has been proposed as an alternative to meniscectomy. Preservation methods are required to build up operational stocks and to provide living grafts of a practical size at the right time for patients. Methods for meniscus preservation have been published, and relevant literature confirms that using standard cryopreservation, the chondrocyte survival in situ is inadequate and extremely variable and the cryoinjury mechanisms are not completely established. The aim of the present study is to further investigate possible cellular injury caused by cryopreservation by analysing apoptosis and ultrastructural damage to menisci.

METHODS

Seven human menisci that were cryopreserved by standard method were used. All tissue samples were processed simultaneously for routine light microscopy, scanning and transmission electron microscopy as well as apoptosis assessment by the use of ISOL method.

RESULTS

With respect to cellularity, significant differences (P < 0.05) between the fresh (14.6 ± 3.5) (mean ± SD) and cryopreserved menisci (9.2 ± 2.8) (mean ± SD) were observed. Apoptosis using ISOL method was observed in fibrochondrocytes of fresh and cryopreserved menisci. The quantitative analysis revealed significant differences (P < 0.05) between fresh meniscus samples, where the apoptotic index was 0.8 ± 2.3% (mean ± SD), and cryopreserved meniscus samples, where this index was 50 ± 18.1% (mean ± SD).

CONCLUSION

The results suggest that apoptosis occurs during meniscus cryopreservation. The major findings of this study are cellular damage in meniscus cryopreservation suggesting apoptosis-mediated cell loss. The findings reported herein encourage to further investigations in preservation procedures to enhance maximum long-term clinical survival.

TNF-alpha mediates diabetes-enhanced chondrocyte apoptosis during fracture healing and stimulates chondrocyte apoptosis through FOXO1

To gain insight into the effect of diabetes on fracture healing, experiments were carried out focusing on chondrocyte apoptosis during the transition from cartilage to bone. Type 1 diabetes was induced in mice by multiple low-dose streptozotocin injections, and simple transverse fractures of the tibia or femur was carried out. Large-scale transcriptional profiling and gene set enrichment analysis were performed to examine apoptotic pathways on total RNA isolated from fracture calluses on days 12, 16, and 22, a period of endochondral bone formation when cartilage is resorbed and chondrocyte numbers decrease. Tumor necrosis factor alpha (TNF-alpha) protein levels were assessed by ELISA and caspase-3 by bioactivity assay. The role of TNF was examined by treating mice with the TNF-specific inhibitor pegsunercept. In vitro studies investigated the proapoptotic transcription factor FOXO1 in regulating TNF-induced apoptosis of chondrogenic ATDC5 and C3H10T1/2 cells as representative of differentiated chondrocytes, which are important during endochondral ossification. mRNA profiling revealed an upregulation of gene sets related to apoptosis in the diabetic group on day 16 when cartilage resorption is active but not day 12 or day 22. This coincided with elevated TNF-alpha protein levels, chondrocyte apoptosis, enhanced caspase-3 activity, and increased FOXO1 nuclear translocation (p < .05). Inhibition of TNF significantly reduced these parameters in the diabetic mice but not in normoglycemic control mice (p < .05). Silencing FOXO1 using siRNA in vitro significantly reduced TNF-induced apoptosis and caspase activity in differentiated chondrocytes. The mRNA levels of the proapoptotic genes caspase-3, caspase-8, caspase-9, and TRAIL were significantly reduced with silencing of FOXO1 in chondrocytic cells. Inhibiting caspase-8 and caspase-9 significantly reduced TNF-induced apoptosis in chondrogenic cells. These results suggest that diabetes causes an upregulation of proapoptotic genes during the transition from cartilage to bone in fracture healing. Diabetes increased chondrocyte apoptosis through a mechanism that involved enhanced production of TNF-alpha, which stimulates chondrocyte apoptosis and upregulates mRNA levels of apoptotic genes through FOXO1 activation.

Joint aging and chondrocyte cell death

Articular cartilage extracellular matrix and cell function change with age and are considered to be the most important factors in the development and progression of osteoarthritis. The multifaceted nature of joint disease indicates that the contribution of cell death can be an important factor at early and late stages of osteoarthritis. Therefore, the pharmacologic inhibition of cell death is likely to be clinically valuable at any stage of the disease. In this article, we will discuss the close association between diverse changes in cartilage aging, how altered conditions influence chondrocyte death, and the implications of preventing cell loss to retard osteoarthritis progression and preserve tissue homeostasis.