Ung Hyun Ko

Islet-like organoids derived from human pluripotent stem cells efficiently function in the glucose responsiveness in vitro and in vivo.

Insulin secretion is elaborately modulated in pancreatic ß cells within islets of three-dimensional (3D) structures. Using human pluripotent stem cells (hPSCs) to develop islet-like structures with insulin-producing ß cells for the treatment of diabetes is challenging. Here, we report that pancreatic islet-like clusters derived from hESCs are functionally capable of glucose-responsive insulin secretion as well as therapeutic effects. Pancreatic hormone-expressing endocrine cells (ECs) were differentiated from hESCs using a step-wise protocol. The hESC-derived ECs expressed pancreatic endocrine hormones, such as insulin, somatostatin, and pancreatic polypeptide. Notably, dissociated ECs autonomously aggregated to form islet-like, 3D structures of consistent sizes (100–150 μm in diameter). These EC clusters (ECCs) enhanced insulin secretion in response to glucose stimulus and potassium channel inhibition in vitro. Furthermore, ß cell-deficient mice transplanted with ECCs survived for more than 40 d while retaining a normal blood glucose level to some extent. The expression of pancreatic endocrine hormones was observed in tissues transplanted with ECCs. In addition, ECCs could be generated from human induced pluripotent stem cells. These results suggest that hPSC-derived, islet-like clusters may be alternative therapeutic cell sources for treating diabetes.

The nesprin-cytoskeleton interface probed directly on single nuclei is a mechanically rich system

ABSTRACT The cytoskeleton provides structure and plays an important role in cellular function such as migration, resisting compression forces, and transport. The cytoskeleton also reacts to physical cues such as fluid shear stress or extracellular matrix remodeling by reorganizing filament associations, most commonly focal adhesions and cell-cell cadherin junctions. These mechanical stimuli can result in genome-level changes, and the physical connection of the cytoskeleton to the nucleus provides an optimal conduit for signal transduction by interfacing with nuclear envelope proteins, called nesprins, within the LINC (linker of the nucleus to the cytoskeleton) complex. Using single-molecule on single nuclei assays, we report that the interactions between the nucleus and the cytoskeleton, thought to be nesprin-cytoskeleton interactions, are highly sensitive to force magnitude and direction depending on whether cells are historically interfaced with the matrix or with cell aggregates. Application of ∼10–30 pN forces to these nesprin linkages yielded structural transitions, with a base transition size of 5–6 nm, which are speculated to be associated with partial unfoldings of the spectrin domains of the nesprins and/or structural changes of histones within the nucleus.

Aging Donor-Derived Human Mesenchymal Stem Cells Exhibit Reduced Reactive Oxygen Species Loads and Increased Differentiation Potential Following Serial Expansion on a PEG-PCL Copolymer Substrate

Human mesenchymal stem cells (hMSCs) have been widely studied for therapeutic development in tissue engineering and regenerative medicine. They can be harvested from human donors via tissue biopsies, such as bone marrow aspiration, and cultured to reach clinically relevant cell numbers. However, an unmet issue lies in the fact that the hMSC donors for regenerative therapies are more likely to be of advanced age. Their stem cells are not as potent compared to those of young donors, and continue to lose healthy, stemness-related activities when the hMSCs are serially passaged in tissue culture plates. Here, we have developed a cheap, scalable, and effective copolymer film to culture hMSCs obtained from aged human donors over several passages without loss of reactive oxygen species (ROS) handling or differentiation capacity. Assays of cell morphology, reactive oxygen species load, and differentiation potential demonstrate the effectiveness of copolymer culture on reduction in senescence-related activities of aging donor-derived hMSCs that could hinder the therapeutic potential of autologous stem cell therapies.

Combinatorial Physical Stimulation and Synergistically-Enhanced Fibroblast Differentiation for Skin Regeneration

For proper wound healing, dermal contraction and remodeling are critical; during the natural healing process, differentiated fibroblasts called “myofibroblasts” typically undertake these functions. For severe wounds, however, a critical mass of dermal matrix and fibroblasts are lost, making self-regeneration impossible. To overcome this impairment, synthetic wound patches with embedded functional cells can be used to promote healing. In this study, we developed a polydioxanone (PDO)-based cell-embedded sheet on which dermal fibroblasts were cultured and induced for differentiation into myofibroblasts, whereby the following combinatorial physicochemical stimuli were also applied: aligned topology, electric field (EF), and growth factor. The results show that both the aligned topology and EF synergistically enhanced the expression of alpha smoothmuscle actin (α-SMA), a key myofibroblast marker. Our proof-of-concept (POC) experiments demonstrated the potential applicability of a myofibroblast-embedded PDO sheet as a wound patch.