1. Selection of candidate genes Hypothesis and objective
POLYMORPHISMS OF SELECTED CHEMOKINE AND CYTOKINE GENES AND RISK FOR FAILURE IN TOTAL HIP ARTHROPLASTY Z. Navratilova1, J. Gallo2, F. Mrazek1, R. Fillerova1, M. Petrek1 1 Laboratory of Immunogenomics and Proteomics, Dept. of Immunology 2 Dept. of Orthopaedics Palacky University and University Hospital Olomouc, Czech Republic
Background
Methods
Subjects
205 unrelated Czech patients with cementless type THA - stratified according to:
1) THA failure (reoperation) and 2) severity of OL. Table 1.
Genotyping
Genotyping technique:
Polymerase Chain Reaction with Sequence Specific Primers (PCR-SSP). Table 2.
3. Statistics
Conformity of the distribution of genotypes to the Hardy-Weinberg equilibrium: χ2 goodness-of-fit test
Differences between allelic, genotype and phenotype („carriage rate“) frequencies: χ2 test.
Periprosthetic osteolysis
Periprosthetic osteolysis (OL) is major complication of the total hip athroplasty (THA) which can result in aseptic loosening and revision surgery.
OL is considered as complex inflammatory response to wear particles liberated from the prosthetic surfaces.
Recent findings support concept of genetic component of OL and aseptic loosening.
Selection of candidate genes
Cytokines and chemokines are though to be plausible candidates for implication in the pathogenesis of OL and aseptic loosening.
Here we selected genes encoding six molecules involved in two (cytokine and chemokine) signalling pathways:
1) IL-17A, IL-17F and IL-23R are important regulators of immune response and may be associated with bone turnover
2) CXCL1, CXCL5 and their receptor CXCR2 promote accumulation of immune cells (namely neutrophils) in site of inflammation
Tab 1. Characteristics of the patients with THA stratified according to the need for reoperation and OL severity
Severe and mild OL according to Saleh et al. classification (J Bone Joint Surg Am, 83: 1040, 2001).
Revised THA
Functional primary THA
Mild OL (Types I, II)
Severe OL (Types III-IV)
Patients, N
157 48 89
116
Gender (men/women)
49/108
19/29
35/54
33/83
Age at index surgery
46 (24-68)
48 (32-58)
48 (27-58)
45 (24-68)
Primary diagnosis
Osteoarthritis 22 26 35 13
Dysplastic hip 76 9 23 62
Other diagnosis 59 31 41
Tab 2. Investigated SNPs and their alleles
Chemokines
Cytokines
Gene
Rs numbers
Genetic variants
CXCL1
Rs4074
G/A
IL-17A Rs
CXCL5
Rs425535
IL-17F
Rs763780
T/C
CXCR2 Rs
C/T
IL-23R Rs
T/G
Hypothesis and objective
Results
Genotypes of all six investigated SNPs were distributed in compliance with the Hardy-Weinberg equilibrium. The distribution of alleles among the patients with THA corresponded to the frequencies observed in Czech healthy control population and other Caucasians (Figure 1).
Out of investigated variants, CXCL1 rs4074 AA genotype was more frequent in the patients with functional primary prosthesis compared to those with revised THA (p = 0.02, Figure 2). The frequency of AA genotype in whole group of the patients with THA was same as that in Czech population (0.12). No further difference in the distribution of tested SNPs was observed between revised and unrevised THA patients (p > 0.05, Figure 3).
None of the explored cytokine / chemokine SNPs was associated with the severity of OL (p > 0.05).
Periprosthetic Osteolysis
Wear Particles
Inflammation
Bone Turnover
Premature THA Failure
Genetic Factors
Fig 1. The frequency of less common alleles for six investigated SNPs in the patients with THA compared to control Czech population.
the patients with THA versus control Czech population p > 0.05 (for all SNPs)
Fig 2. Proportion of CXCL1 rs4074 AA genotype in the patients with total hip athroplasty (THA) failure compared to those in the patients with functional primary THA
THA failure versus functional primary THA p = 0.02
The aim of the present study was to investigate possible association of single nucleotide polymorphisms (SNPs) within the genes encoding for CXCL1, CXCL5, CXCR2, IL-17A, IL-17F and
IL-23R with severity of OL and THA failure (revision).
Conclusions
Fig 3. The frequencies of less common alleles for six investigated SNPs in the patients with revised THA compared to those with functional primary THA.
revised THA versus functional primary THA: p > 0.05
In this pilot study, less common AA genotype of CXCL1 rs4074 SNP appeared as a marker associated with the protection from total hip arthroplasty failure (revision).
Our preliminary findings should be replicated in larger THA cohorts, optimally including more detailed and functional analysis of the CXCL1 gene variability. Studies of CXCL1 role in OL and aseptic loosening of THA are desirable as well.
Conclusions
Grant support: GACR 310/09/P377, IGA NS and MSM