Background
Idiopathic osteonecrosis of the femoral head (ONFH) frequently occurs after liver transplantation (LT) because of lifelong administration of corticosteroids or immunosuppressants and often requires total hip arthroplasty (THA). This study examines patient characteristics and short-term outcomes of THA after LT.
Methods
We observed 9 hips in 7 patients who underwent THA from August 2015 to December 2017 for ONFH after LT (group L). Cementless implants were inserted in all hips. Medical records were retrospectively reviewed to reveal reasons for LT, type of donor, and period from LT to THA. Preoperative laboratory data, operative time, intraoperative blood loss, complication rates, and Harris Hip Score were compared with a control group of 27 cementless THAs in 27 patients with ONFH.
Results
Causative diseases were liver cirrhosis (n = 4), type B fulminant hepatitis (n = 1), congenital biliary atresia (n = 1), and iatrogenic biliary tract injury (n = 1). Four livers were from living donors and 3 from cadavers. Mean time from LT to THA was 10.4 (1-20) years. Preoperative blood test showed a significant decrease in platelet count (178 vs 268 [∗10
3
/μl]) and rise in total bilirubin (1.1 vs 0.7 [mg/dL]) in group L. There was no significant difference in operative time (86 vs 100 [minutes]), but intraoperative blood loss (303 vs 163 [mL]) increased significantly in group L. There were no significant differences in complication incidence or Harris Hip Score between the 2 groups.
Conclusion
THA after LT requires caution because risks for bleeding increase. However, short-term outcomes appear to be equivalent to normal THA.
Osteoclasts and foreign body giant cells (FBGCs) are derived from common progenitors and share properties such as multi-nucleation capacity induced by cell-cell fusion; however, mechanisms underlying lineage determination between these cells remain unclear. Here we show that, under inflammatory conditions, osteoclasts are stimulated in a manner similar to M1 macrophages, while formation of FBGCs, which exhibit M2-like phenotypes, is inhibited in a manner similar to that seen in M1/M2 macrophage polarization. FBGC/osteoclast polarization was inhibited by conditional knockout of tumor necrosis factor receptor associated factor 6 (Traf6) in adults in vivo and in vitro. Traf6-null mice were previously reported to die soon after birth, but we found that Traf6 deletion in adults did not cause lethality but rather inhibited osteoclast activation and prevented FBGC inhibition under inflammatory conditions. Accordingly, basal osteoclastogenesis was significantly inhibited by Traf6 deletion in vivo and in vitro and accompanied by increased bone mass. Lipopolysaccharide-induced osteoclast formation and osteolysis were significantly inhibited in Traf6 conditional knockout mice. Our results suggest that Traf6 plays a crucial role in regulating M1 osteoclast and M2 FBGC polarization and is a potential therapeutic target in blocking FBGC inhibition, antagonizing osteolysis in inflammatory conditions, and increasing bone mass without adverse effects in adults.
Vitamin D deficiency is a recognized risk factor for sarcopenia development, but mechanisms underlying this outcome are unclear. Here, we show that low vitamin D status worsens immobilization-induced muscle atrophy in mice. Mice globally lacking vitamin D receptor (VDR) exhibited more severe muscle atrophy following limb immobilization than controls. Moreover, immobilization-induced muscle atrophy was worse in neural crest-specific than in skeletal muscle-specific VDR-deficient mice.
Tnfα
expression was significantly higher in immobilized muscle of VDR-deficient relative to control mice, and was significantly elevated in neural crest-specific but not muscle-specific VDR-deficient mice. Furthermore, muscle atrophy induced by limb immobilization in low vitamin D mice was significantly inhibited in Tnfα-deficient mice. We conclude that vitamin D antagonizes immobilization-induced muscle atrophy via VDR expressed in neural crest-derived cells.
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