Heterotopic ossification, osteolysis and implant failure following cervical total disc replacement with the M6-C™ artificial disc.

INTRODUCTION: A recent study reported a 34% mid-term revision rate after M6-C™ cervical total disc replacement (CTDR) for wear-related osteolysis. Here, we aim to investigate the prevalence, risk factors, and radiographic characteristics of periprosthetic bony changes and implant failure of the M6-C™ artificial disc. METHODS: We retrospectively analysed radiographic (conventional X-ray, CT scan) and clinical outcomes (EQ-5D-5L, Neck Disability Index (NDI), and Visual Analog Scale (VAS) for neck and arm pain) data collected during routine follow-up of patients who underwent CTDR with the M6-C™ between 2011 and 2015. RESULTS: In total, 85 patients underwent CTDR with the M6-C™. Follow-up data were available for 43 patients (54% female, mean age 44 years) with 50 implants and a mean follow-up of 8.1 years (6.5-11 years). Implant failure with the presence of severe osteolysis was identified in 5 (12%) patients who were all male (p = 0.016) and implanted at the C5/6 level (p = 0.11). All failed implants required revision surgery. The overall prevalence of osteolysis was 44% (22/50 implants) and 34% (17/50 implants) for significant heterotopic ossification. Patients with high-grade osteolysis showed higher VAS arm pain (p = 0.05) and lower EQ-5D-VAS health VAS (p = 0.03). CONCLUSION: We report a lower reoperation rate for failed M6-C™ implants than previously published, but confirmed that osteolysis and heterotopic ossification are common following CTDR with the M6-C™ and may be asymptomatic. Therefore, we strongly recommend ongoing clinical and radiographic monitoring after CTDR with the M6-C™, particularly for male patients implanted at the C5/6 level.

Expression in skin biopsies supports genetic evidence linking CAMKK2, P2X7R and P2X4R with HIV-associated sensory neuropathy.

HIV-associated sensory neuropathy (HIV-SN) affects 14-38% of HIV+ individuals stable on therapy with no neurotoxic drugs. Polymorphisms in CAMKK2, P2X7R and P2X4R associated with altered risk of HIV-SN in Indonesian and South African patients. The role of CaMKK2 in neuronal repair makes this an attractive candidate, but a direct role for any protein is predicated on expression in affected tissues. Here, we describe expression of CaMKK2, P2X7R and P2X4R proteins in skin biopsies from the lower legs of HIV+ Indonesians with and without HIV-SN, and healthy controls (HC). HIV-SN was diagnosed using the Brief Peripheral Neuropathy Screen. Biopsies were stained to detect protein gene product 9.5 on nerve fibres and CaMKK2, P2X7R or P2X4R, and were examined using 3-colour sequential scanning confocal microscopy. Intraepidermal nerve fibre densities (IENFD) were lower in HIV+ donors than HC and correlated directly with nadir CD4 T-cell counts (r = 0.69, p = 0.004). However, IENFD counts were similar in HIV-SN+ and HIV-SN- donors (p = 0.19) and so did not define neuropathy. CaMKK2+ cells were located close to dermal and epidermal nerve fibres and were rare in HC and HIV-SN- donors, consistent with a role for the protein in nerve damage and/or repair. P2X7R was expressed by cells in blood vessels of HIV-SN- donors, but rarely in HC or HIV-SN+ donors. P2X4R expression by cells in the epidermal basal layer appeared greatest in HIV-SN+ donors. Overall, the differential expression of CaMKK2, P2X7R and P2X4R supports the genetic evidence of a role for these proteins in HIV-SN.

TNF-Block Genotypes Influence Susceptibility to HIV-Associated Sensory Neuropathy in Indonesians and South Africans.

HIV-associated sensory neuropathy (HIV-SN) is a disabling complication of HIV disease and antiretroviral therapies (ART). Since stavudine was removed from recommended treatment schedules, the prevalence of HIV-SN has declined and associated risk factors have changed. With stavudine, rs1799964*C (TNF-1031) associated with HIV-SN in Caucasians and Indonesians but not in South Africans. Here, we investigate associations between HIV-SN and rs1799964*C and 12 other polymorphisms spanning TNF and seven neighboring genes (the TNF-block) in Indonesians (n = 202; 34/168 cases) and South Africans (n = 75; 29/75 cases) treated without stavudine. Haplotypes were derived using fastPHASE and haplotype networks built with PopART. There were no associations with rs1799964*C in either population. However, rs9281523*C in intron 10 of BAT1 (alternatively DDX39B) independently associated with HIV-SN in Indonesians after correcting for lower CD4 T-cell counts and >500 copies of HIV RNA/mL (model p = 0.0011, Pseudo R2 = 0.09). rs4947324*T (between NFKBIL1 and LTA) independently associated with reduced risk of HIV-SN and African haplotype 1 (containing no minor alleles) associated with increased risk of HIV-SN after correcting for greater body weight, a history of tuberculosis and nadir CD4 T-cell counts (model: p = 0.0003, Pseudo R2 = 0.23). These results confirm TNF-block genotypes influence susceptibility of HIV-SN. However, critical genotypes differ between ethnicities and with stavudine use.

Polymorphisms in P2X4R and CAMKK2 may affect TNFα production: Implications for a role in HIV-associated sensory neuropathy.

Polymorphisms in P2X4R and CAMKK2 associate with susceptibility to HIV-associated sensory neuropathy (HIV-SN) - a condition likely mediated by TNFα. As single nucleotide polymorphisms (SNPs) and haplotypes of CAMKK2, and a neighbouring gene P2X4R, mark susceptibility to HIV-SN in South Africans living with HIV, we examined the relationship between P2X4R and CAMKK2 genotypes and TNFα production. Peripheral blood mononuclear cells from 129 healthy donors were stimulated with killed Escherichia coli, and concentrations of soluble TNFα were assessed. Their DNA was genotyped for 22 SNPs in P2X4R and CAMKK2. Three SNPs within P2X4R and two SNPs within CAMKK2 influenced concentrations of TNFα, but these SNP did not associate with risk for HIV-SN. This incongruence may reflect differences in P2X4R haplotypes present in Africans and Europeans. However some CAMKK2 haplotypes were found in both populations, so CAMKK2 polymorphisms may impact upon HIV-SN via effects of the protein on pathways other than TNFα.

Ex-vivo expression of chemokine receptors on cells surrounding cutaneous nerves in patients with HIV-associated sensory neuropathy.

OBJECTIVE: HIV-associated sensory neuropathy (HIV-SN) remains common in HIV+ individuals receiving antiretroviral therapy (ART), even though neurotoxic antiretroviral drugs (e.g. stavudine) have been phased out of use. Accumulating evidence indicates that the neuropathy is immune-mediated. We hypothesize that chemokines produced locally in the skin promote migration of macrophages and T cells into the tissue, damaging cutaneous nerves causing HIV-SN. DESIGN: We assessed chemokine receptor expression on infiltrating CD14 and CD3 cells around cutaneous nerves in standardized skin biopsies from HIV-SN+ patients (n = 5), HIV-SN- patients (n = 9) and healthy controls (n = 4). METHODS: The AIDS Clinical Trials Group Brief Peripheral Neuropathy Screen was used to assess Indonesian HIV+ patients receiving ART without stavudine (case definition: bilateral presence of at least one symptom and at least one sign of neuropathy). Distal leg skin biopsies were stained to visualize chemokine receptors (CCR2, CCR5, CXCR3, CXCR4, CX3CR1), infiltrating CD3 and CD14 cells, and protein-gene-product 9.5 on nerves, using immunohistochemistry and 4-colour confocal microscopy. RESULTS: Intraepidermal nerve fibre density was variable in patients without HIV-SN and generally lower in those with HIV-SN. CX3CR1 was more evident on CD14 cells whereas CCR2, CCR5, CXCR3 and CXCR4 were more common on CD3 cells. Expression of CX3CR1, CCR2 and CCR5 was more common in HIV-SN+ patients than those without HIV-SN. CXCR3 and CXCR4 were upregulated in all HIV+ patients, compared with healthy controls. CONCLUSION: Inflammatory macrophages expressing CX3CR1 and T cells expressing CCR2 and CCR5 may participate in peripheral nerve damage leading to HIV-SN in HIV+ patients treated without stavudine. Further characterization of these cells is warranted.

Polymorphisms in IL10 may alter CD4 T-cell counts in Indonesian HIV patients beginning antiretroviral therapy.

Interleukin 10 (IL-10) is a potent anti-inflammatory cytokine influenced by single nucleotide polymorphisms (SNP) located in upstream regulatory regions. Here we address the effects of five SNP (rs1518111, rs3021094, rs3024491, rs1800872 and rs1800871) on CD4 T-cell counts in Indonesian HIV patients assessed before ART and over 12months on treatment. Heterozygosity at rs1518111 or rs1800872 associated with low CD4 T-cell counts at all time points. Both alleles were carried in two haplotypes. Haplotype 21122 (present in 30% of participants) associated with low CD4 T-cell counts, whereas 21222 (in 6% of participants) did not. Hence untyped SNP(s) tagged by 21122 may depress CD4 T-cell counts. The association with heterozygosity suggests synergy with an allele from a haplotype lacking rs1518111 and/or rs1800872.