A switch in the mode of Wnt signaling orchestrates the formation of germline stem cell differentiation niche in Drosophila.

Germline stem cell (GSC) self-renewal and differentiation into gametes is regulated by both intrinsic factors in the germ line as well as extrinsic factors from the surrounding somatic niche. dWnt4, in the escort cells of the adult somatic niche promotes GSC differentiation using the canonical ß-catenin-dependent transcriptional pathway to regulate escort cell survival, adhesion to the germ line and downregulation of self-renewal signaling. Here, we show that in addition to the ß-catenin-dependent canonical pathway, dWnt4 also uses downstream components of the Wnt non-canonical pathway to promote escort cell function earlier in development. We find that the downstream non-canonical components, RhoA, Rac1 and cdc42, are expressed at high levels and are active in escort cell precursors of the female larval gonad compared to the adult somatic niche. Consistent with this expression pattern, we find that the non-canonical pathway components function in the larval stages but not in adults to regulate GSC differentiation. In the larval gonad, dWnt4, RhoA, Rac1 and cdc42 are required to promote intermingling of escort cell precursors, a function that then promotes proper escort cell function in the adults. We find that dWnt4 acts by modulating the activity of RhoA, Rac1 and cdc42, but not their protein levels. Together, our results indicate that at different points of development, dWnt4 switches from using the non-canonical pathway components to using a ß-catenin-dependent canonical pathway in the escort cells to facilitate the proper differentiation of GSCs.

Techniques to Address Humeral Bone Insufficiency During Total Shoulder Arthroplasty With a Nonspherical Humeral Head and Inlay Glenoid.

Total shoulder arthroplasty with a humeral head resurfacing (HHR) component and an inlay glenoid (OVOMotion; Arthrosurface) is a successful treatment option for patients with advanced glenohumeral arthritis, an intact rotator cuff, and adequate proximal humeral bone stock. In patients with poor proximal humeral bone, historically stemmed humeral components have been used instead of HHR. However, strategies can be used to successfully optimize HHR implant fixation in suboptimal bone without converting to stemmed implants or in surgical centers where stemmed prostheses are not available. This Technical Note describes 3 techniques-upsizing the humeral taper post, using humeral autograft, and cementation-to improve humeral implant fixation in patients with suboptimal bone stock when using the Arthrosurface OVOMotion implant.

Anatomic total shoulder arthroplasty with a nonspherical humeral head and inlay glenoid: 90-day complication profile in the inpatient versus outpatient setting.

BACKGROUND: Total shoulder arthroplasty (TSA) with a nonspherical humeral head component and inlay glenoid is a successful bone-preserving treatment for glenohumeral arthritis. This study aimed to describe the 90-day complication profile of TSA with this prosthesis and compare major and minor complication and readmission rates between inpatient- and outpatient-procedure patients. METHODS: A retrospective review was performed of a consecutive cohort of patients undergoing TSA with a nonspherical humeral head and inlay glenoid in the inpatient and outpatient settings by a single surgeon between 2017 and 2022. Age, sex, body mass index, American Society of Anesthesiologists (ASA) score, Charlson Comorbidity Index (CCI), and 90-day complication and readmission rates were compared between inpatient and outpatient groups. RESULTS: One hundred eighteen TSAs in 111 patients were identified. Mean age was 64.9 years (range, 39-90) and 65% of patients were male. Ninety-four (80%) and 24 (20%) patients underwent outpatient and inpatient procedures, respectively. Four complications (3.4%) were recorded: axillary nerve stretch injury, isolated ipsilateral arm deep venous thrombosis (DVT), ipsilateral arm DVT with pulmonary embolism requiring readmission, and gastrointestinal bleed requiring readmission. There were no reoperations or other complications. Outpatients were younger with lower ASA and CCI scores than inpatients; however, there was no difference in complications (1/24 vs. 3/94, P=1.00) or readmissions (1/24 vs. 1/94, P=0.37) between these two groups. CONCLUSIONS: TSA with a nonspherical humeral head and inlay glenoid can be performed safely in both inpatient and outpatient settings. Rates of early complications and readmissions were low with no difference according to surgical setting. Level of evidence: IV.