Lifetime risk and genetic predisposition to post-traumatic OA of the knee in the UK Biobank

OBJECTIVE

Acute knee injury is associated with post-traumatic OA (PTOA). Very little is known about the genome-wide associations of PTOA when compared with idiopathic OA (iOA). Our objective was to describe the development of knee OA after a knee injury and its genetic associations in UK Biobank (UKB).

DESIGN

Clinically significant structural knee injuries in those ≤50 years were identified from electronic health records and self-reported data in 502,409 UKB participants. Time-to-first knee osteoarthritis (OA) code was compared in injured cases and age-/sex-matched non-injured controls using Cox Proportional Hazards models. A time-to-OA genome-wide association study (GWAS) sought evidence for PTOA risk variants 6 months to 20 years following injury. Evidence for associations of two iOA polygenic risk scores (PRS) was sought.

RESULTS

Of 4233 knee injury cases, 1896 (44.8%) were female (mean age at injury 34.1 years [SD 10.4]). Over a median of 30.2 (IQR 19.5-45.4) years, 1096 (25.9%) of injured cases developed knee OA. The overall hazards ratio (HR) for knee OA after injury was 1.81 (1.70,1.93), P = 8.9 × 10-74. Female sex and increasing age at injury were associated with knee OA following injury (HR 1.15 [1.02,1.30];1.07 [1,07,1.07] respectively). OA risk was highest in the first 5 years after injury (HR 3.26 [2.67,3.98]), persisting for 40 years. In 3074 knee injury cases included in the time-to-OA GWAS, no variants reached genome-wide significance. iOA PRS was not associated with time-to-OA (HR 0.43 [0.02,8.41]).

CONCLUSIONS

Increasing age at injury and female sex appear to be associated with future development of PTOA in UKB, the risk of which was greatest in the 5 years after injury. Further international efforts towards a better-powered meta-analysis will definitively elucidate genetic similarities and differences of PTOA and iOA.

Evaluating Nuclear Factor NF-κB Activation following Bone Trauma: A Pilot Study in a Wistar Rats Model

The present study investigated the moment of peak NF-kB activation and its dissipation in the cortical bone in the femur of Wistar rat stimulated by surgical trauma. Sixty-five Wistar rats were divided into 13 groups (n = 5 per group): eight experimental groups (expG 1–8) divided based on the euthanasia time point (zero, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h and 24 h) and five sham control groups (conG 1–5) killed at zero, 1 h, 2 h, 4 h and 6 h, respectively. A 1.8-mm-diameter defect was generated 0.5 mm from the femur proximal joint using a round bur to induce the surgical trauma. Overall, the activation peak of NF-κB in the cortical bone was 6 h (expG5 group) independent of the evaluated position; this peak was significantly different compared to those in the other groups (p < 0.05). The surgical trauma resulted in a spread of immune markings throughout the cortical bone with an accentuation in the knee region. The present study provides the first evidence that the NF-κB activation peak was established after 6 hours in the cortical bone of Wistar rats. The signs from a surgical trauma can span the entire cortical bone and are not limited to the damaged region.

Identification of Suitable Reference Genes for Investigating Gene Expression in Anterior Cruciate Ligament Injury by Using Reverse Transcription-Quantitative PCR

The anterior cruciate ligament (ACL) is one of the most frequently injured structures during high-impact sporting activities. Gene expression analysis may be a useful tool for understanding ACL tears and healing failure. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) has emerged as an effective method for such studies. However, this technique requires the use of suitable reference genes for data normalization. Here, we evaluated the suitability of six reference genes (18S, ACTB, B2M, GAPDH, HPRT1, and TBP) by using ACL samples of 39 individuals with ACL tears (20 with isolated ACL tears and 19 with ACL tear and combined meniscal injury) and of 13 controls. The stability of the candidate reference genes was determined by using the NormFinder, geNorm, BestKeeper DataAssist, and RefFinder software packages and the comparative ΔCt method. ACTB was the best single reference gene and ACTB+TBP was the best gene pair. The GenEx software showed that the accumulated standard deviation is reduced when a larger number of reference genes is used for gene expression normalization. However, the use of a single reference gene may not be suitable. To identify the optimal combination of reference genes, we evaluated the expression of FN1 and PLOD1. We observed that at least 3 reference genes should be used. ACTB+HPRT1+18S is the best trio for the analyses involving isolated ACL tears and controls. Conversely, ACTB+TBP+18S is the best trio for the analyses involving (1) injured ACL tears and controls, and (2) ACL tears of patients with meniscal tears and controls. Therefore, if the gene expression study aims to compare non-injured ACL, isolated ACL tears and ACL tears from patients with meniscal tear as three independent groups ACTB+TBP+18S+HPRT1 should be used. In conclusion, 3 or more genes should be used as reference genes for analysis of ACL samples of individuals with and without ACL tears.

Sex-steroid regulation of relaxin receptor isoforms (RXFP1 & RXFP2) expression in the patellar tendon and lateral collateral ligament of female WKY rats

The incidence of non-contact knee injury was found higher in female than in male and is related to the phases of the menstrual cycle. This raised the possibility that female sex-steroids are involved in the mechanism underlying this injury via affecting the expression of the receptors for relaxin, a peptide hormone known to modulate ligament laxity. Therefore, this study aims to investigate the effect of sex-steroids on relaxin receptor isoforms (RXFP1 & RXFP2) expression in the ligaments and tendons of the knee.

METHODS

Ovariectomized adult female WKY rats were treated with different doses of estrogen (0.2, 2, 20 μg/kg), progesterone (4mg) and testosterone (125 & 250μg/kg) for three consecutive days. At the end of the treatment, the animals were sacrificed and the patellar tendon and lateral collateral ligament were harvested for mRNA and protein expression analyses by Real Time PCR and Western blotting respectively.

RESULTS

RXFP1, the main isoform expressed in these knee structures and RXFP2 showed a dose-dependent increase in expression with estrogen. Progesterone treatment resulted in an increase while testosterone caused a dose-dependent decrease in the mRNA and protein expression of both relaxin receptor isoforms.

DISCUSSION

Progesterone and high dose estrogen up-regulate while testosterone down-regulates RXFP1 and RXFP2 expression in the patellar tendon and lateral collateral ligament of rat's knee.

CONCLUSION

Relaxin receptor isoforms up-regulation by progesterone and high dose estrogen could provide the basis for the reported increase in knee laxity while down-regulation of these receptor isoforms by testosterone could explain low incidence of non-contact knee injury in male.

Mechanical injury of bovine cartilage explants induces depth-dependent, transient changes in MAP kinase activity associated with apoptosis

OBJECTIVE

To characterize mitogen activated protein (MAP) kinase activity and chondrocyte apoptosis in an in vitro model of cartilage mechanical injury as a function of tissue depth and time post-injury.

DESIGN

Mechanically injured osteochondral explants were assessed for cell viability, MAP kinase and caspase-3 activity over 15 days using immunofluorescence microscopy and Western blot. Zonal distributions of cell viability and apoptosis were quantified in the presence of specific mitogen activated protein kinase inhibitors.

RESULTS

Viability rapidly decreased post-injury, most significantly in the superficial zone, with some involvement of the middle and deep zones, which correlated with increased caspase-3 activity. Transient and significant increases in extracellular-regulated protein kinase (ERK) activity were observed in middle and deep zones at 1 and 6 days post-injury, while c-Jun-amino terminal protein kinase activity increased in the deep zone at 1 and 6 days compared to uninjured controls. Changes in p38 activity were particularly pronounced, with significant increases in all three zones 30 min post-injury, but only in the middle and deep zones after 1 and 6 days. Inhibition of ERK and p38 increased chondrocyte viability which correlated with decreased apoptosis.

CONCLUSIONS

Spatiotemporal patterns of MAP kinase signalling in cartilage after mechanical injury strongly correlate with changes in cell viability and chondrocyte apoptosis. Importantly, these signals may be pro-survival or pro-apoptotic depending on zonal location and time post-injury. These data yield mechanistic insights which may improve the diagnosis and treatment of cartilage injuries.

Enhanced meniscal repair by overexpression of hIGF-1 in a full-thickness model

The importance of the menisci to the well-being of the normal knee is well-documented. However, there is no ideal repair or reconstructive approach for damaged menisci. Gene therapy provides one promising alternative strategy, especially when combined with injectable tissue engineering to achieve minimally invasive clinical application. We asked whether the introduction of human insulin-like growth factor 1 (hIGF-1) gene could improve the repair of full-thickness meniscal defects. We created full-thickness meniscal defects in the "white area" of the anterior horn in 48 goats. Bone marrow stromal cells with the transfection of hIGF-1 gene and injectable calcium alginate gel were mixed together to repair the defects; three control groups included cells without transfection, gel without cells, and defects left empty. After 4, 8, and 16 weeks, the animals were euthanized and the excised defects were examined by macroscopic assessment, histological analysis, electron microscopy, proteoglycan determination, and MRI. Sixteen weeks after surgery the repaired meniscal defects were filled with white tissue similar to that in normal meniscal fibrocartilage. The repair tissue was composed of cells embedded within matrix that filled the spaces of the fibers. The proteoglycan content in the gene-enhanced tissue engineering group was higher than those in the control groups, and less than that in the normal meniscus. The results suggest full-thickness meniscal defects in regions without blood supply can be reconstructed with hIGF-1-enhanced injectable tissue engineering.

Tendon and ligament injuries: the genetic component

Tendons and ligaments within the upper and lower limbs are some of the more common sites of musculoskeletal injuries during physical activity. Several extrinsic and intrinsic factors have been shown to be associated with these injuries. More recently, studies have suggested that there is also, at least in part, a genetic component to the Achilles tendon, rotator cuff and anterior cruciate ligament injuries. However, specific genes have not been suggested to be associated with rotator cuff or anterior cruciate ligament injuries. Sequence variants of the tenascin C (TNC) gene, on the other hand, have been shown to be associated with Achilles tendinopathies and Achilles tendon ruptures, whereas a variant of the collagen V alpha 1 (COL5A1) gene has also been shown to be associated with Achilles tendinopathies. Both genes encode for important structural components of tendons and ligaments. The COL5A1 gene encodes for a component of type V collagen, which has an important role in regulating collagen fibre assembly and fibre diameters. The TNC gene, on the other hand, encodes for TNC, which regulates the tissue's response to mechanical load. To date, only variants in two genes have been shown to be associated with Achilles tendon injuries. In addition, although specific genes have not been identified, investigators have suggested that there is also a genetic component to both rotator cuff and anterior cruciate ligament injuries. In future, specific genotypes associated with increased risk of injury to specific tendons and ligaments can prevent these injuries by identifying individuals at higher risk.

Understanding and preventing noncontact anterior cruciate ligament injuries: a review of the Hunt Valley II meeting, January 2005

The incidence of noncontact anterior cruciate ligament injuries in young to middle-aged athletes remains high. Despite early diagnosis and appropriate operative and nonoperative treatments, posttraumatic degenerative arthritis may develop. In a meeting in Atlanta, Georgia (January 2005), sponsored by the American Orthopaedic Society for Sports Medicine, a group of physicians, physical therapists, athletic trainers, biomechanists, epidemiologists, and other scientists interested in this area of research met to review current knowledge on risk factors associated with noncontact anterior cruciate ligament injuries, anterior cruciate ligament injury biomechanics, and existing anterior cruciate ligament prevention programs. This article reports on the presentations, discussions, and recommendations of this group.

The effects of exercise on human articular cartilage

The effects of exercise on articular hyaline articular cartilage have traditionally been examined in animal models, but until recently little information has been available on human cartilage. Magnetic resonance imaging now permits cartilage morphology and composition to be analysed quantitatively in vivo. This review briefly describes the methodological background of quantitative cartilage imaging and summarizes work on short-term (deformational behaviour) and long-term (functional adaptation) effects of exercise on human articular cartilage. Current findings suggest that human cartilage deforms very little in vivo during physiological activities and recovers from deformation within 90 min after loading. Whereas cartilage deformation appears to become less with increasing age, sex and physical training status do not seem to affect in vivo deformational behaviour. There is now good evidence that cartilage undergoes some type of atrophy (thinning) under reduced loading conditions, such as with postoperative immobilization and paraplegia. However, increased loading (as encountered by elite athletes) does not appear to be associated with increased average cartilage thickness. Findings in twins, however, suggest a strong genetic contribution to cartilage morphology. Potential reasons for the inability of cartilage to adapt to mechanical stimuli include a lack of evolutionary pressure and a decoupling of mechanical competence and tissue mass.

The familial predisposition toward tearing the anterior cruciate ligament: a case control study

PURPOSE

A study of 171 surgical cases and 171 matched controls was conducted to investigate whether a familial predisposition toward tearing the anterior cruciate ligament of the knee exists.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

Patients who were diagnosed with an anterior cruciate ligament tear were matched by age (within 5 years), gender, and primary sport to subjects without an anterior cruciate ligament tear. All 342 subjects completed a questionnaire detailing their family history of anterior cruciate ligament tears.

RESULTS

When controlling for subject age and number of relatives, participants with an anterior cruciate ligament tear were twice as likely to have a relative (first, second, or third degree) with an anterior cruciate ligament tear compared to participants without an anterior cruciate ligament tear (adjusted odds ratio = 2.00; 95% confidence interval, 1.19-3.33). When the analysis was limited to include only first-degree relatives, participants with an anterior cruciate ligament tear were slightly greater than twice as likely to have a first-degree relative with an anterior cruciate ligament tear compared to participants without an anterior cruciate ligament tear (adjusted odds ratio = 2.24; 95% confidence interval, 1.24-4.00).

CONCLUSIONS

Findings are consistent with a familial predisposition toward tearing the anterior cruciate ligament.

CLINICAL RELEVANCE

Future research should concentrate on identifying the potentially modifiable risk factors that may be passed through families and developing strategies for the prevention of anterior cruciate ligament injuries.

Functional Tissue Engineering for Ligament Healing: Potential of Antisense Gene Therapy

Traumatic knee injuries frequently involve the disruption of multiple ligaments, such as a complete tear of the medial collateral ligament (MCL) together with a rupture of the anterior cruciate ligament (ACL) (Miyasaka, K., D. M. Daniel, M. L. Stone, and P. Hirshman. Am. J. Knee Surg. 4:3-8, 1991). Despite the high incidence, clinical management of this type of injury is still debated. Laboratory studies have shown that the ACL and MCL share the responsibility of stabilizing the knee, especially in response to valgus and other rotatory torques as well as anterior tibial loads (Inoue, M., E. McGurk-Burleson, J. M. Hollis, and S. L-Y. Woo. Am. J. Sports Med. 15:15-21, 1987; Kanamori, A., M. Sakane, J. Zeminski, T. W. Rudy, and S. L-Y. Woo. J. Ortho. Sci. 5:567-571, 2000; Ma, C. B., C. D. Papageogiou, R. E. Debski, and S. L. Woo. Acta Orthop. Scand. 71:387-393, 2000; Sakane, M., G. A. Livesay, R. J. Fox, T. W. Rudy, T. J. Runco, and S. L-Y. Woo. Knee Surg. Sports Traumatol. Arthrosc. 7:93-97, 1999). When one structure is deficient, the force in the other increases significantly to compensate. The injured ACL does not heal and requires surgical replacement by tissue grafts. On the other hand, after an isolated MCL tear or in a combined MCL and ACL injury, the MCL can heal spontaneously without surgical intervention and can function well in most cases. Nevertheless, the biomechanical and biochemical properties as well as the histomorphological appearance of the healing MCL are substantially different to those of normal tissue (Bray, R. C., D. J. Butterwick, M. R. Daschak, and J. V. Tyberg. J. Orthop. Res. 14:618-625, 1996; Loitz-Ramage, B. J., C. B. Frank, and N. G. Shrive. Clin. Orthop.:272-280, 1997; Weiss, J. A., S. L-Y. Woo, K. J. Ohland, S. Horibe, and P. O. Newton. J. Orthop. Res. 9:516-528, 1991). In an effort to improve the outcome of injuries to these and other ligaments, therapeutic strategies associated with improving biomechanical, biochemical, and histomorphological properties of ligaments have been investigated in recent years. These therapeutic strategies include growth factor stimulation (Conti, N. A., and L. E. Dahners. Presented at Orthopaedic Research Society, San Francisco, CA; Deie, M., T. Marui, C. R. Allen, K. A. Hildebrand, H. I. Georgescu, et al. Mech. Ageing Dev. 97:121-130, 1997), cell therapy (Menetrey, J., C. Kasemkijwattana, C. S. Day, P. Bosch, F. H. Fu, et al. Tissue Eng. 5:435-442, 1999; Watanabe, N., S. L-Y. Woo, C. Papageorgiou, C. Celechovsky, and S. Takai. Microsc. Res. Tech. 58:39-44, 2002), as well as gene stherapy (Nakamura N., D. A. Hart, R. S. Boorman, Y. Kaneda, N. G. Shrive, et al. J. Orthop. Res. 18:517-523, 2000; Shimomura, T., F. Jia, C. Niyibizi, and S. L-Y. Woo. Connect. Tissue Res.:2003). The knowledge gained by studying these therapeutic strategies could potentially be applied to other ligaments and tendons. In this article, antisense gene therapy to alter gene expression by using antisense oligonucleotides will be examined as a possible solution.

Matrix metalloproteinase-13 expression in rabbit knee joint connective tissues: influence of maturation and response to injury

The hypothesis of the present work was that expression of matrix metalloproteinase-13 (MMP-13, collagenase-3) would be induced during conditions involving important matrix remodeling such as ligament maturation, scar healing and joint instability. Therefore, MMP-13 expression in the medial collateral ligament (MCL) during the variable situations of tissue maturation and healing was assessed. MMP-13 expression in three intra-articular connective tissues of the knee (i.e. articular cartilage, menisci and synovium) following the transection of the anterior cruciate ligament of the knee was evaluated at 3 and 8 weeks post-injury. MMP-13 mRNA (semi-quantitative RT-PCR) and protein (immunohistochemistry and Western blotting) were detected in all of the tissues studied. Significantly higher MCL mRNA levels for MMP-13 were detected during the early phases of tissue maturation (i.e. 29 days in utero and 2-month-old rabbits) compared to later phases (5- and 12-month-old rabbits). This pattern of expression was recapitulated following MCL injury, with very high levels of expression in scar tissue at 3 weeks post-injury and then a decline to levels not significantly different from control values by 14 weeks. Elevated mRNA levels correlated with increased protein levels for MMP-13 in both menisci and synovium following the transection of the anterior cruciate ligament and during medial collateral ligament healing. These results indicate that MMP-13 expression is regulated by a number of variables and that high levels of expression occur in situations when connective tissue remodeling is very active.

[Virally mediated gene transfer in the patellar tendon. An experimental study in rabbits]

Growth factors have the potential to enhance native repair responses in ligamentous and meniscal lesions. However, methods for applying these cytokines to sites of injury for extended periods are lacking. We suggest that local transfer of genes that encode the relevant healing factors merits investigation as a potential solution to this problem. In the present study, different viral vectors and liposomes are evaluated for their ability to deliver genes to cells of ligamentous and meniscal origin. The ACL, PCL, MCL, semitendinosus tendon, patellar tendon, and menisci were harvested from New Zealand white rabbits. Cells grown from these tissues were then investigated for their susceptibility to genetic alteration by these vectors. Based upon the ability of these vectors to convert cells in culture to a lacZ(+) phenotype, adenovirus was the most effective vector in short-term experiments. However, expression was transient. Although retrovirus gave lower initial transduction efficiencies, the percentage of transduced cells could be increased by the use of the selectable marker gene neo(r). Cells infected with adeno-associated virus containing the neor-gene could also be selected in this way. Liposomes showed low efficiency of gene transfer and expression. In an in vivo marker study, we injected adenovirus into the rabbit patellar tendon. Transduced cells could be observed preferentially in the subsynovial layer at a declining frequency over a 6-week period. The allogeneous transplantation of retrovirally transduced fibroblasts into the patellar tendon resulted in a greater number of transduced cells. Although the number of lacZ(+) cells declined with time, positive cells were still present 6 weeks after transplantation. Furthermore, the transplanted cells, unlike cells transduced in situ with adenovirus, migrated from the injection site and integrated into the crimp of the tendon.

Surgery in acute patellar dislocation--evaluation of the effect of injury mechanism and family occurrence on the outcome of treatment

A retrospective study was made of 270 patients and 284 knees with acute patellar dislocation treated operatively. The mean follow up time was 4.1 years. Medical history revealed 21.1% of cases with previous dislocations and 15.6% of cases with family occurrence of patellar dislocation. The dislocation resulted from an athletic performance in 41.5% of cases. The sport events most often associated with patellar dislocation were soccer, gymnastics, and ice hockey. All cases were treated with reefing of medial capsule. Release of lateral patellar retinacula was performed in 243 cases. Two cases were treated primarily with the Elmslie-Roux-Trillat procedure. The subjective result of operative treatment was better and the redislocation rate was lower if the injury mechanism was traumatic rather than non-traumatic and if there was no history for family occurrence of patellar dislocation.