SummaryCell therapies treating pathological muscle atrophy or damage requires an adequate quantity of muscle progenitor cells (MPCs) not currently attainable from adult donors. Here, we generate cultures of approximately 90% skeletal myogenic cells by treating human embryonic stem cells (ESCs) with the GSK3 inhibitor CHIR99021 followed by FGF2 and N2 supplements. Gene expression analysis identified progressive expression of mesoderm, somite, dermomyotome, and myotome markers, following patterns of embryonic myogenesis. CHIR99021 enhanced transcript levels of the pan-mesoderm gene T and paraxial-mesoderm genes MSGN1 and TBX6; immunofluorescence confirmed that 91% ± 6% of cells expressed T immediately following treatment. By 7 weeks, 47% ± 3% of cells were MYH+ve myocytes/myotubes surrounded by a 43% ± 4% population of PAX7+ve MPCs, indicating 90% of cells had achieved myogenic identity without any cell sorting. Treatment of mouse ESCs with these factors resulted in similar enhancements of myogenesis. These studies establish a foundation for serum-free and chemically defined monolayer skeletal myogenesis of ESCs.

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Rhomboids comprise a broad family of intramembrane serine proteases that are found in a wide range of organisms and participate in a diverse array of biological processes. Highresolution structures of the catalytic transmembrane domain of the Escherichia coli GlpG rhomboid have provided numerous insights that help explain how hydrolytic cleavage can be achieved below the membrane surface. Key to this are observations that GlpG hydrophobic domain dimensions may not be sufficient to completely span the native lipid bilayer. This formed the basis for a model where hydrophobic mismatch Induces thinning of the local membrane environment to promote access to transmembrane substrates. However, hydrophobic mismatch also has the potential to alter the functional properties of the rhomboid, a possibility we explore in the current work. For this purpose, we purified the catalytic transmembrane domain of GlpG into phosphocholine or maltoside detergent micelles of varying alkyl chain lengths, and assessed proteolytic function with a model water-soluble substrate. Catalytic turnover numbers were found to depend on detergent alkyl chain length, with saturated chains containing 10-12 carbon atoms supporting maximal activity. Similar results were obtained in phospholipid bicelles, with no proteolytic activity being detected in longer-chain lipids. Although differences in thermal stability and GlpG oligomerization could not explain these activity differences, circular dichroism spectra suggest that mismatch gives rise to a small change in structure. Overall, these results demonstrate that hydrophobic mismatch can exert an inhibitory effect on rhomboid activity, with the potential for changes in local membrane environment to regulate activity in vivo.

Operative classification of ventral abdominal hernias: new and practical classification. Yasser Selim. From the Ministry of Health.Background: Ventral hernias of the abdomen are defined as a noninguinal, nonhiatal defect in the fascia of the abdominal wall. Unfortunately, there is not currently a universal classification system for ventral hernias. One of the more accepted classification systems is that of the European Hernia Society (EHS). Its limitation is that it does not include individual patient risk factors and wound classification. The aim of this work was to find out the basic principles of hernia etiology and pathogenesis, clarify the factors that are important in treatment of ventral hernias, and categorize hernia patients according to those factors. Methods: This retrospective study included 238 patients who presented to our surgery department between 2010 and 2020. A full description of ventral hernias was made, including their type according to the EHS. In addition, abdominal wall components were assessed, including strength of rectus muscles, lateral abdominal muscles, and abdominal fascia, namely the linea alba. Patients with spontaneous hernias were grouped according to the size of the defect and the condition of the rectus abdominis muscles, the fascia and other abdominal muscles. Results: Patients were put into 6 clinical categories: type 1A, type 1B, type 2, type 3, type 4, and type 5. The grouping of patients was done according to the factors we believed affect the choice of surgical procedure and the prognosis of repair. Patients with types 1 and 2 have normal abdominal muscles, whereas those with types 3 and 4 have weak muscles and weak stretched fascia (linea alba). Type 5 includes incisional hernias. Conclusion: The primary purpose of any classification should be to improve the possibility of comparing different studies and their results. By describing hernias in a standardized way, different patient populations can be compared. Numerous classifications for groin and ventral hernias have been proposed over the past 5-6 decades. For primary abdominal wall hernias, there was agreement with EHS classification on the use of localization and size as classification variables.