In vitro-generated human muscle reserve cells are heterogeneous for Pax7 with distinct molecular states and metabolic profiles.

BACKGROUND: The capacity of skeletal muscles to regenerate relies on Pax7+ muscle stem cells (MuSC). While in vitro-amplified MuSC are activated and lose part of their regenerative capacity, in vitro-generated human muscle reserve cells (MuRC) are very similar to quiescent MuSC with properties required for their use in cell-based therapies. METHODS: In the present study, we investigated the heterogeneity of human MuRC and characterized their molecular signature and metabolic profile. RESULTS: We observed that Notch signaling is active and essential for the generation of quiescent human Pax7+ MuRC in vitro. We also revealed, by immunofluorescence and flow cytometry, two distinct subpopulations of MuRC distinguished by their relative Pax7 expression. After 48 h in differentiation medium (DM), the Pax7High subpopulation represented 35% of the total MuRC pool and this percentage increased to 61% after 96 h in DM. Transcriptomic analysis revealed that Pax7High MuRC were less primed for myogenic differentiation as compared to Pax7Low MuRC and displayed a metabolic shift from glycolysis toward fatty acid oxidation. The bioenergetic profile of human MuRC displayed a 1.5-fold decrease in glycolysis, basal respiration and ATP-linked respiration as compared to myoblasts. We also observed that AMPKα1 expression was significantly upregulated in human MuRC that correlated with an increased phosphorylation of acetyl-CoA carboxylase (ACC). Finally, we showed that fatty acid uptake was increased in MuRC as compared to myoblasts, whereas no changes were observed for glucose uptake. CONCLUSIONS: Overall, these data reveal that the quiescent MuRC pool is heterogeneous for Pax7 with a Pax7High subpopulation being in a deeper quiescent state, less committed to differentiation and displaying a reduced metabolic activity. Altogether, our data suggest that human Pax7High MuRC may constitute an appropriate stem cell source for potential therapeutic applications in skeletal muscle diseases.

Primary Pyomyositis Caused by Kingella kingae in a 21-Month-old Infant: A Case Report.

The authors report a rare case of an unusual primary pyomyositis of the biceps cruralis assigned to Kingella kingae in a 21-month-old girl. The reported case demonstrated that primary pyomyositis may be encountered during invasive infection due to K. kingae even if this manifestation remains rare. This bacterial etiology must, therefore, be evoked when a primary pyomyositis is observed, and this is in particular in children under 4 years of age.

A single dose of tranexamic acid reduces blood loss after reverse and anatomic shoulder arthroplasty: a randomized controlled trial.

BACKGROUND: Hematoma formation and the need for blood transfusions are commonly reported complications after shoulder arthroplasty. Tranexamic acid (TXA) has been widely used in hip and knee arthroplasty to decrease perioperative blood loss. The role of TXA is still being established in shoulder arthroplasty. MATERIALS AND METHODS: We conducted a double-blind randomized controlled trial comparing intravenous TXA vs. placebo in 60 patients undergoing primary anatomic or reverse shoulder arthroplasty. Of these patients, 29 received a placebo whereas 31 received a single dose of 2 g of intravenous TXA. Patient demographic characteristics, as well as drain tube output, blood loss, hematoma formation, transfusion requirement, length of hospital stay, and pain score, were recorded. Patients were followed up for 12 weeks to assess for complications. RESULTS: Patients who received TXA had a lower drain tube output at all time points: 41 mL vs. 133 mL at 6 hours, 75 mL vs. 179 mL at 12 hours, and 94 mL vs. 226 mL at 24 hours (P < .001 for all). They also had a higher postoperative hemoglobin (Hb) level (12.3 g/dL vs. 11.4 g/dL, P = .009), lower change in Hb level (1.7 g/dL vs. 2.3 g/dL, P = .011), lower total Hb loss (0.078 g vs. 0.103 g, P = .042), lower blood volume loss (0.55 L vs. 0.74 L, P = .021), higher postoperative hematocrit level (36.7% vs. 34.6%, P = .020), and lower hematocrit change (5.4% vs. 7.6%, P = .022). There was no significant difference in pain score or length of hospital stay, and no patients required a transfusion. CONCLUSION: A single dose of 2 g of intravenous TXA decreases blood loss and drain tube output in primary anatomic and reverse arthroplasty of the shoulder. No differences were detected in the occurrence of complications, need for transfusion, pain score, or length of hospital stay. With the mounting evidence now available, patients undergoing elective primary shoulder arthroplasty should be given intravenous TXA to decrease perioperative blood loss.

Kingella kingae Osteoarticular Infections Approached through the Prism of the Pediatric Orthopedist.

Nowadays, Kingella kingae (K. kingae) is considered as the main bacterial cause of osteoarticular infections (OAI) in children aged less than 48 months. Next to classical acute hematogenous osteomyelitis and septic arthritis, invasive K. kingae infections can also give rise to atypical osteoarticular infections, such as cellulitis, pyomyositis, bursitis, or tendon sheath infections. Clinically, K. kingae OAI are usually characterized by a mild clinical presentation and by a modest biologic inflammatory response to infection. Most of the time, children with skeletal system infections due to K. kingae would not require invasive surgical procedures, except maybe for excluding pyogenic germs' implication. In addition, K. kingae's OAI respond well even to short antibiotics treatments, and, therefore, the management of these infections requires only short hospitalization, and most of the patients can then be treated safely as outpatients.

[Therapeutic approaches for proximal humerus fractures]. / Approches thérapeutiques des fractures de l'humérus proximal.

Proximal humerus fracture (PHF) is the 3rd most common fracture over age 65, and its incidence increases with age. The combination of an aging population and a high incidence in geriatric patients constitute a serious potential public health concern. The treatment of PHF is debated. Recent publications report similar results of conservative versus surgical treatment in several types of fractures. Therapeutic decision based on a multiparametric analysis is recommended, there is yet no consensus on the parameters to be analyzed. A recent study suggests taking into consideration individual parameters in deciding the therapeutic strategy and provides a pragmatic treatment algorithm. We propose here a simplified version of this algorithm, guiding therapeutic decision between conservative treatment, osteosynthesis and arthroplasty.

La fracture de l'humérus proximal (FHP) est la troisième fracture la plus fréquente au-delà de 65 ans, et son incidence augmente avec l'âge. Avec le vieillissement de la population, l'incidence des FHP devrait augmenter ces prochaines années, en en faisant un véritable problème de santé publique. Leur traitement est un débat d'actualité. Des publications récentes rapportent des résultats similaires entre traitement conservateur et traitement chirurgical dans plusieurs types de FHP. Concernant le choix de traitement, une décision basée sur une analyse multiparamétrique est recommandée mais les paramètres à considérer ne font actuellement pas l'objet d'un consensus. Nous proposons ici un algorithme basé sur celui d'une étude récente, permettant de guider la décision thérapeutique entre traitement conservateur, ostéosynthèse et arthroplastie.