The liver-resident immune cell repertoire - A boon or a bane during machine perfusion?

The liver has been proposed as an important “immune organ” of the body, as it is critically involved in a variety of specific and unique immune tasks. It contains a huge resident immune cell repertoire, which determines the balance between tolerance and inflammation in the hepatic microenvironment. Liver-resident immune cells, populating the sinusoids and the space of Disse, include professional antigen-presenting cells, myeloid cells, as well as innate and adaptive lymphoid cell populations. Machine perfusion (MP) has emerged as an innovative technology to preserve organs ex vivo while testing for organ quality and function prior to transplantation. As for the liver, hypothermic and normothermic MP techniques have successfully been implemented in clinically routine, especially for the use of marginal donor livers. Although there is evidence that ischemia reperfusion injury-associated inflammation is reduced in machine-perfused livers, little is known whether MP impacts the quantity, activation state and function of the hepatic immune-cell repertoire, and how this affects the inflammatory milieu during MP. At this point, it remains even speculative if liver-resident immune cells primarily exert a pro-inflammatory and hence destructive effect on machine-perfused organs, or in part may be essential to induce liver regeneration and counteract liver damage. This review discusses the role of hepatic immune cell subtypes during inflammatory conditions and ischemia reperfusion injury in the context of liver transplantation. We further highlight the possible impact of MP on the modification of the immune cell repertoire and its potential for future applications and immune modulation of the liver.

The natural alpha angle of the femoral head-neck junction

Aims

Asphericity of the femoral head-neck junction is common in cam-type femoroacetabular impingement (FAI) and usually quantified using the alpha angle on radiographs or MRI. The aim of this study was to determine the natural alpha angle in a large cohort of patients by continuous circumferential analysis with CT.

Methods

CT scans of 1312 femurs of 656 patients were analyzed in this cross-sectional study. There were 362 men and 294 women. Their mean age was 61.2 years (18 to 93). All scans had been performed for reasons other than hip disease. Digital circumferential analysis allowed continuous determination of the alpha angle around the entire head-neck junction. All statistical tests were conducted two-sided; a p-value < 0.05 was considered statistically significant.

Results

The mean maximum alpha angle for the cohort was 59.0° (sd 9.4). The maximum was located anterosuperiorly at 01:36 on the clock face, with two additional maxima of asphericity at the posterior and inferior head-neck junction. The mean alpha angle was significantly larger in men (59.4°, sd 8.0) compared with women (53.5°, sd 7.4°; p = 0.0005), and in Caucasians (60.7°, sd 9.0°) compared with Africans (56.3°, sd 8.0; p = 0.007) and Asians (50.8°, sd 7.2; p = 0.0005). The alpha angle showed a weak positive correlation with age (p < 0.05). If measured at commonly used planes of the radially reconstructed CT or MRI, the alpha angle was largely underestimated; measurement at the 01:30 and 02:00 positions showed a mean underestimation of 4° and 6°, respectively.

Conclusion

This study provides important data on the normal alpha angle dependent on age, gender, and ethnic origin. The normal alpha angle in men is > 55°, and this should be borne in mind when making a diagnosis of cam-type morphology. Cite this article: Bone Joint J 2018;100-B:570–8.

Intraoperative, fluoroscopy-based planning for complex osteotomies of the proximal femur

Intertrochanteric osteotomy of the proximal femur is a surgical technique that aims at changing the orientation of the proximal part of the femur in the hip joint by removing a bone wedge between the trochanters. Due to its six degrees of freedom, it presents a complex planning problem for the surgeon. In this paper, we propose an intraoperative planning system for proximal femur osteotomies. Based on two fluoroscopic images taken during the procedure, a primitive femur model is reconstructed, which then allows the user to interactively determine the osteotomy parameters and perform the intervention with the help of a navigation system. Besides the fluoroscopic images, no other imaging is needed. Compared to the traditional approach, this system allows the intervention to be performed with higher precision and less radiation exposure for both patient and surgeon, requiring only little time overhead. An in vitro study has demonstrated the high accuracy and ease of use of this system.

Fluoroskopiebasierte 3D-Navigation komplexer Korrekturosteotomien des proximalen Femurs

BACKGROUND

Despite great advances in hip alloarthroplasty there are still numerous indications for joint-saving procedures such as correction osteotomies. Often these procedures include complex 3D rearrangements of the proximal femur, which are for the surgeon technically very demanding. The project aim was to develop a precise intraoperative virtual 3D planning tool including a detailed biomechanical analysis and enable the surgeon to realize exactly this plan by using computer-assisted techniques.

METHODS

Using only two different angled fluoro frames a simplified femoral model was inversely constructed. For navigation a passive optical system was used with a C-arm calibration kit and PC-based software. For in vitro evaluation complex osteotomies were performed on ten femora under simulated OR conditions.

RESULTS

The mean difference between the planning and real surgical outcome for the wedge size was less then 2 degrees and for the femur head center position less then 4 mm. No implant penetrated the femur neck isthmus.

CONCLUSION

Without changing the standard operative procedure the method can be of high clinical importance to improve planning accuracy and consecutive operative realization for precise fragment positioning and plate location without penetrating the isthmus of the femoral neck. And -- besides precision -- it can potentially help to reduce intraoperative complications such as implant penetration and minimize X-ray use.

Changes in the serine-specific transfer ribonucleic acid pattern of guinea pig epidermis after corticosteroid treatment

The pattern of serine-specific tRNAs from guinea pig epidermis was determined and compared to that from liver by employing reversed phase chromatography on total tRNA preparations aminoacylated with 3H- or 14C-serine. Five tRNAserS (I-V) were found, two of which, tRNAserI and tRNAserV, appear to be "typical" for epidermis and in so far probably reflect in some way metabolic peculiarities of epidermal cell differentiation. This hypothesis was further corroborated by showing that the locally applied corticosteroid triamcinolon selectively increases tRNAserI and tRNAserV 2-3-fold. The implications of these findings were discussed in detail.

Comparative characterization of four purified lysine-specific transfer ribonucleic acids from chicken embryos

Four purified tRNALys species from 13-day-old chick embryo muscle have been characterized with respect to the following properties: qualitative oligoribonucleotide composition (polyacrylamide gel electrophoresis after RNase T1 digestion), anticodon response towards AAG and AAA (equilibrium dialysis and polylysine synthesis), strength of the aminoacyl bond (de-esterification kinetics), sedimentation coefficient, and temperature-dependent double helix-to-coil transition. The results confirm the existence of four molecularly independent lysine-specific tRNA's in this eukaryotic system.