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Summary: Stem cell therapies for degenerative cartilage disease are limited by an incomplete understanding of hyaline cartilage formation and maintenance. Human bone marrow stromal cells/skeletal stem cells (hBMSCs/SSCs) produce stable hyaline cartilage when attached to hyaluronic acid-coated fibrin microbeads (HyA-FMBs), yet the mechanism remains unclear. In vitro, hBMSC/SSC/HyA-FMB organoids exhibited reduced BMP signaling early in chondrogenic differentiation, followed by restoration of BMP signaling in chondrogenic IGFBP5+/MGP+ cells. Subsequently, human-induced pluripotent stem cell (hiPSC)-derived sclerotome cells were established (BMP inhibition) and then treated with transforming growth factor β (TGF-β) −/+ BMP2 and growth differentiation factor 5 (GDF5) (BMP signaling activation). TGF-β alone elicited a weak chondrogenic response, but TGF-β/BMP2/GDF5 led to delamination of SOX9+ aggregates (chondrospheroids) with high expression of COL2A1, ACAN, and PRG4 and minimal expression of COL10A1 and ALP in vitro. While transplanted hBMSCs/SSCs/HyA-FMBs did not heal articular cartilage defects in immunocompromised rodents, chondrospheroid-derived cells/HyA-FMBs formed non-hypertrophic cartilage that persisted until at least 5 months in vivo.

Cut-and-paste |$K$| -theory has recently emerged as an important variant of higher algebraic |$K$| -theory. However, many of the powerful tools used to study classical higher algebraic |$K$| -theory do not yet have analogues in the cut-and-paste setting. In particular, there does not yet exist a sensible notion of the Dennis trace for cut-and-paste |$K$| -theory. In this paper we address the particular case of the |$K$| -theory of polyhedra, also called scissors congruence |$K$| -theory. We introduce an explicit, computable trace map from the higher scissors congruence groups to group homology, and use this trace to prove the existence of some nonzero classes in the higher scissors congruence groups. We also show that the |$K$| -theory of polyhedra is a homotopy orbit spectrum. This fits into Thomason's general framework of |$K$| -theory commuting with homotopy colimits, but we give a self-contained proof. We then use this result to re-interpret the trace map as a partial inverse to the map that commutes homotopy orbits with algebraic |$K$| -theory. [ABSTRACT FROM AUTHOR]

The climate crisis prompted the International Monetary Fund (IMF), an international lender of last resort, to implement wholesale reforms to incorporate climate policy into its operations. At the IMF, selected countries from the Global North—historically the largest emitters of greenhouse gases—dominate decision‐making. This raises several questions. Can the Fund implement an ambitious and effective climate policy? How are climate‐vulnerable developing countries and their interests represented in everyday decision‐making at the institution? Drawing on scholarship on the political economy and legitimacy of international organizations, we focus on the formal distribution of decision‐making power within the IMF to evaluate the IMF's shift toward climate change. Our empirical analysis of the representation of 57 self‐identifying climate‐vulnerable developing countries (the V20) at the IMF and within its Executive Board shows that these countries, speaking for almost a third of the Fund's membership, command a vote share of merely 5.6%. Our assessment of the Climate Strategy adopted by the IMF amplifies equity concerns over its climate policies and further attests to the disregard of requests by developing countries. Barring meaningful governance reform to increase the voice and representation of climate‐vulnerable developing countries, the IMF's approach to addressing climate change is unlikely to translate into legitimate and effective climate policy. [ABSTRACT FROM AUTHOR]

We prove that the group of strict contactomorphisms of the standard tight contact structure on the three-sphere deformation retracts to its unitary subgroup U (2). [ABSTRACT FROM AUTHOR]