The P522R protective variant of PLCG2 promotes the expression of antigen presentation genes by human microglia in an Alzheimer's disease mouse model

The P522R variant of PLCG2, expressed by microglia, is associated with reduced risk of Alzheimer's disease (AD). Yet, the impact of this protective mutation on microglial responses to AD pathology remains unknown. Chimeric AD and wild-type mice were generated by transplanting PLCG2-P522R or isogenic wild-type human induced pluripotent stem cell microglia. At 7 months of age, single-cell and bulk RNA sequencing, and histological analyses were performed. The PLCG2-P522R variant induced a significant increase in microglial human leukocyte antigen (HLA) expression and the induction of antigen presentation, chemokine signaling, and T cell proliferation pathways. Examination of immune-intact AD mice further demonstrated that the PLCG2-P522R variant promotes the recruitment of CD8+ T cells to the brain. These data provide the first evidence that the PLCG2-P522R variant increases the capacity of microglia to recruit T cells and present antigens, promoting a microglial transcriptional state that has recently been shown to be reduced in AD patient brains.

Plaque-associated human microglia accumulate lipid droplets in a chimeric model of Alzheimer's disease

BACKGROUND

Disease-associated microglia (DAMs), that surround beta-amyloid plaques, represent a transcriptionally-distinct microglial profile in Alzheimer's disease (AD). Activation of DAMs is dependent on triggering receptor expressed on myeloid cells 2 (TREM2) in mouse models and the AD TREM2-R47H risk variant reduces microglial activation and plaque association in human carriers. Interestingly, TREM2 has also been identified as a microglial lipid-sensor, and recent data indicates lipid droplet accumulation in aged microglia, that is in turn associated with a dysfunctional proinflammatory phenotype. However, whether lipid droplets (LDs) are present in human microglia in AD and how the R47H mutation affects this remains unknown.

METHODS

To determine the impact of the TREM2 R47H mutation on human microglial function in vivo, we transplanted wild-type and isogenic TREM2-R47H iPSC-derived microglial progenitors into our recently developed chimeric Alzheimer mouse model. At 7 months of age scRNA-seq and histological analyses were performed.

RESULTS

Here we report that the transcriptome of human wild-type TREM2 and isogenic TREM2-R47H DAM xenografted microglia (xMGs), isolated from chimeric AD mice, closely resembles that of human atherosclerotic foam cells. In addition, much like foam cells, plaque-bound xMGs are highly enriched in lipid droplets. Somewhat surprisingly and in contrast to a recent in vitro study, TREM2-R47H mutant xMGs exhibit an overall reduction in the accumulation of lipid droplets in vivo. Notably, TREM2-R47H xMGs also show overall reduced reactivity to plaques, including diminished plaque-proximity, reduced CD9 expression, and lower secretion of plaque-associated APOE.

CONCLUSIONS

Altogether, these results indicate lipid droplet accumulation occurs in human DAM xMGs in AD, but is reduced in TREM2-R47H DAM xMGs, as it occurs secondary to TREM2-mediated changes in plaque proximity and reactivity.

Fast Adipogenesis Tracking System (FATS)-a robust, high-throughput, automation-ready adipogenesis quantification technique

Adipogenesis is essential in in vitro experimentation to assess differentiation capability of stem cells, and therefore, its accurate measurement is important. Quantitative analysis of adipogenic levels, however, is challenging and often susceptible to errors due to non-specific reading or manual estimation by observers. To this end, we developed a novel adipocyte quantification algorithm, named Fast Adipogenesis Tracking System (FATS), based on computer vision libraries. The FATS algorithm is versatile and capable of accurately detecting and quantifying percentage of cells undergoing adipogenic and browning differentiation even under difficult conditions such as the presence of large cell clumps or high cell densities. The algorithm was tested on various cell lines including 3T3-L1 cells, adipose-derived mesenchymal stem cells (ASCs), and induced pluripotent stem cell (iPSC)-derived cells. The FATS algorithm is particularly useful for adipogenic measurement of embryoid bodies derived from pluripotent stem cells and was capable of accurately distinguishing adipogenic cells from false-positive stains. We then demonstrate the effectiveness of the FATS algorithm for screening of nuclear receptor ligands that affect adipogenesis in the high-throughput manner. Together, the FATS offer a universal and automated image-based method to quantify adipocyte differentiation of different cell lines in both standard and high-throughput workflows.

[Conceptual model for assessment and management of human risk from transport pollution]

The existing methodology for human health risk assessment allows one to appreciably study cause-and-effect relationships between environmental factors and human health. Risk management is a logic continuation of the assessment of human health risk and it is aimed at substantiating the choice of decisions that are best in a specific situation to eliminate or minimize it, to make follow-up monitoring of exposures and a risk, to evaluate the efficiency of health-improving measures and to correct the latter. Risk management involves technical, technological, organizational, social, legal, economic, normative, political, and other decisions made on the conclusions and estimates obtained when characterizing the risk.

A new bioabsorbable interference screw: preliminary results of a prospective, multicenter, randomized clinical trial

SUMMARY

A randomized clinical trial was conducted to compare a bioabsorbable polyglyconate screw (Endo-Fix; Smith & Nephew, Andover, MA) to a metal screw in anterior cruciate ligament reconstruction. A total of 124 patients were operated on and 113 assessed up to 1 year postoperatively. Assessments included a history and physical examination, the IKDC evaluation, and knee arthrometry measurements. No significant differences were found between the groups with respect to any of the IKDC problem areas at 1 year. The IKDC final evaluation was normal or nearly normal in 92% of polyglyconate patients and 90% of controls. The incidence of postoperative complications was similar in the 2 groups. One polyglyconate patient developed a subcutaneous cyst that may have been related to breakdown of the screw. This resolved without treatment and the patient had an excellent clinical outcome. This study shows that the polyglyconate screw is an effective alternative to metal in endoscopic reconstruction of the ACL.

[Multi-directional instability of the shoulder; e new form of chronic shoulder instability]

This article describes multidirectional shoulder instability. This lesion is not rare and is easily overlooked. MDI is often caused by repeated minor injuries in athletic patients. The basic lesion in MDI is an enlarged joint volume. The diagnosis is based on the clinical picture. The sulcus sign is pathognomonic. Conservative treatment is the treatment of first choice. If complaints persist after one year of conservative treatment, a capsular shift as described by Neer is recommended.

Neer arthroplasty for humeral fracture

The Neer arthroplasty was performed in 10 patients with four-part proximal humeral fractures. The average follow-up was 2.5 years. No serious complications occurred. All but one became pain-free, but only four were classified as excellent or satisfactory. Videofluoroscopy revealed only minimal gleno-humeral movement in most cases.

The results of treatment of comminuted fractures and fracture dislocations of the proximal humerus

Out of 31 patients with a comminuted fracture or fracture dislocation of the proximal humerus, 21 were followed up. Twelve patients were treated operatively by internal fixation or endoprosthesis and nine were treated conservatively. The best results were achieved after internal fixation, especially in the younger patients. In the older patients, implantation of a prosthesis gave a satisfactory result.