Synthetic probes for in vitro purification and in vivo tracking of hepatocytes derived from human pluripotent stem cells

A general fluorescence off/on strategy for fluorogenic probes: Steric repulsion-induced twisted intramolecular charge transfer (sr-TICT)

Various control strategies are available for building fluorogenic probes to visualize biological events in terms of a fluorescence change. Here, we performed the time-dependent density functional theory (TD-DFT) computational analysis of the twisted intramolecular charge transfer (TICT) process in rhodamine dyes. On the basis of the results, we designed and synthesized a series of rhodamine dyes and established a fluorescence quenching strategy that we call steric repulsion-induced TICT (sr-TICT), in which the fluorescence quenching process is greatly accelerated by simple intramolecular twisting. As proof of concept of this design strategy, we used it to develop a fluorogenic probe, 2-Me PeER (pentyloxyethylrhodamine), for the N-dealkylation activity of CYP3A4. We applied 2-Me PeER for CYP3A4 activity-based fluorescence-activated cell sorting (FACS), providing access to homogeneous, highly functional human-induced pluripotent stem cell (hiPSC)-derived hepatocytes and intestinal epithelial cells. Our results suggest that sr-TICT represents a general fluorescence control method for fluorogenic probes.

Progress of near-infrared-II fluorescence in precision diagnosis and treatment of colorectal cancer

Colorectal cancer is a malignant tumour with high incidence and mortality worldwide; therefore, improving the early diagnosis of colorectal cancer and implementing a targeted "individualized treatment" strategy is of great concern. NIR-II fluorescence imaging is a large-depth, high-resolution optical bioimaging tool. Around the NIR-II window, researchers have developed a variety of luminescent probes, imaging systems, and treatment methods with colorectal cancer targeting capabilities, which can be visualized and image-guided in clinical surgery. This article aims to overcome the difficulties in diagnosing and treating colorectal cancer. The present review summarizes the latest results on using NIR-II fluorescence for targeted colorectal cancer imaging, expounds on the application prospects of NIR-II optical imaging for colorectal cancer, and discusses the imaging-guided multifunctional diagnosis and treatment platforms.

Pluripotent stem cells: Basic biology or else differentiations aimed at translational research and the role of flow cytometry

Pluripotent stem cell research has revolutionized the modern era for the past 14 years with the advent of induced pluripotent stem cells. Before this time, scientists had access to human and mouse embryonic stem cells primarily for basic research and an attempt towards lineage-specific differentiations for cell therapy applications. Regarding pluripotent stem cells, expression of bonafide marker proteins such as Oct4, Nanog, Sox2, Klf4, c-Myc, and Lin28 have been considered giving a perfect readout for pluripotent stem cells and assessed using an analytical flow cytometer. In addition to the intracellular markers, surface markers such as stage-specific embryonic antigen-1 for mouse cells and SSEA-4 for human cells are needed to sort pure populations of stem cells for further downstream applications for cell therapy. The surface marker SSEA-4 is the most appropriate for obtaining pure populations of human pluripotent stem cells. When differentiated in a controlled manner using growth factors or small molecules, it is mandatory to assess the downregulation of pluripotency markers (Oct4, Nanog, Sox2, and Klf4) with subsequent up-regulation of stage-specific differentiation markers. Such assessments are done using flow cytometry. Pluripotent stem cells have a high teratoma-forming potential in vivo. Small amounts of undifferentiated PSCs might lead to dangerous teratomas upon transplantation if leftover in the pool of differentiated cells. Hence, flow cytometry is essential for sorting out PSC populations with teratoma-forming potential. The pure populations of differentiated progenitors need to be flow-sorted before differentiating them further for cell therapy applications. For example, Glycoprotein 2 is a specific cell-surface marker for pancreatic progenitors that enables one to sort the pancreatic progenitors differentiated from human PSCs. Taken together, analytical flow cytometry, and cell sorting provide indispensable tools in PSC research and cell therapy.

Mn2+ /Fe3+ /Co2+ and Tetrasulfide Bond Co-Incorporated Dendritic Mesoporous Organosilica as Multifunctional Nanocarriers: One-Step Synthesis and Applications for Cancer Therapy

Enriching the application of multifunctional dendritic mesoporous organosilica (DMOS) is still challenging in anti-cancer research. Herein, manganese ions, iron ions, or cobalt ions and tetrasulfide bonds are co-incorporated into the framework of DMOS to yield multifunctional nanoparticles denoted as Mn-DMOS, Fe-DMOS, or Co-DMOS by directly doping metal ions during the synthetic process. Due to co-incorporation of metal ions and tetrasulfide bonds, these designed nanocarriers have more functions rather than only for cargo delivery. As proof of concept, the nanocomposite is established based on Mn-DMOS as an efficient nanocarrier for indocyanine green (ICG) delivery and modification with polyethylene glycol. In the tumor microenvironment, the generated hydrogen sulfide (H₂ S) arising from the reaction between tetrasulfide bond and over-expressed glutathione (GSH) causes mitochondrial injury to reduce cellular respiration. The released Mn²⁺ from the rapidly decomposed nanocomposite catalyzes the endogenous hydrogen peroxide to produce oxygen (O₂ ). The photothermal effect from the released ICG initiated by the near-infrared light induces cancer cells apoptosis and simultaneously enhances the content of blood O₂ at tumor sites. Therefore, due to the GSH depletion and trimodal O₂ compensation, the photodynamic therapy efficiency of ICG has significantly improved. In brief, these designed nanocarriers will play advanced roles in cancer therapy.

Precise Diagnosis and Therapy of Bone Cancer Using Near-Infrared Lights

Bone is a preferred site for both primary and metastasis tumors. Current diagnosis of osteopathia typically relies on noninvasive skeleton radiography technology. However, due to the limited resolution of ionizing radiation, accurate diagnosis and effective identification impairment areas are still lacking. Near-infrared (NIR) bioimaging, especially in the NIR-II (1000-1700 nm) regions, can provide high sensitivity and spatiotemporal resolution bioimaging compared to the conventional radiography. Thus, NIR bioimaging affords intraoperative visualization and imaging-guided surgery, aiming to overcome challenges associated with theranostics of osteopathia and bone tumors. The present review aimed to summarize the latest evidence on the use of NIR probes for the targeting bone imaging. We further highlight the recent advances in bone photoX (X presents thermal, dynamic, and immuno) therapy through NIR probes, in particular combination with other customized therapeutic agents could provide high-efficiency treatment for bone tumors.

Laminin-511 and recombinant vitronectin supplementation enables human pluripotent stem cell culture and differentiation on conventional tissue culture polystyrene surfaces in xeno-free conditions

Human pluripotent stem cells (hPSCs) are typically cultivated on extracellular matrix (ECM) protein-coated dishes in xeno-free culture conditions. We supplemented mixed ECM proteins (laminin-511 and recombinant vitronectin, rVT) in culture medium for hPSC culture on conventional polystyrene dishes. Three hPSC cell lines were successfully cultivated on uncoated polystyrene dishes in medium supplemented with optimal conditions of laminin-511 and rVT. Excellent colony shape and colony size as well as high expansion fold of hPSCs were found under these conditions, whereas the colony size was small and poor expansion fold was found solely on L-511-coated dishes. A small portion of L-511 in the culture medium supported hPSC adhesion and prevented the adhesion from being too strong on the uncoated dishes, and rVT in the culture medium further supported adhesion of hPSCs on the dishes by maintaining their pluripotency. Having the optimal composition of L-511 and rVT in the culture medium was important for generating good hPSC colony shapes and sizes as well as a high expansion fold. After long-term culture of hPSCs on uncoated dishes supplemented with the mixed proteins, the hPSCs successfully showed pluripotent markers and could differentiate into a specific lineage of cells, cardiomyocytes, with high efficiency.

Downstream bioprocessing of human pluripotent stem cell‐derived therapeutics

With the advancement in lineage‐specific differentiation from human pluripotent stem cells (hPSCs), downstream cell separation has now become a critical step to produce hPSC‐derived products. Since differentiation procedures usually result in a heterogeneous cell population, cell separation needs to be performed either to enrich the desired cell population or remove the undesired cell population. This article summarizes recent advances in separation processes for hPSC‐derived cells, including the standard separation technologies, such as magnetic‐activated cell sorting, as well as the novel separation strategies, such as those based on adhesion strength and metabolic flux. Specifically, the downstream bioprocessing flow and the identification of surface markers for various cell lineages are discussed. While challenges remain for large‐scale downstream bioprocessing of hPSC‐derived cells, the rational quality‐by‐design approach should be implemented to enhance the understanding of the relationship between process and the product and to ensure the safety of the produced cells.

In Vivo Subretinal ARPE-19 Cell Tracking Using Indocyanine Green Contrast-Enhanced Multimodality Photoacoustic Microscopy, Optical Coherence Tomography, and Fluorescence Imaging for Regenerative Medicine

Purpose

Cell-based regenerative therapies are being investigated as a novel treatment method to treat currently incurable eye diseases, such as geographic atrophy in macular degeneration. Photoacoustic imaging is a promising technology which can visualize transplanted stem cells in vivo longitudinally over time in the retina. In this study, a US Food and Drug Administration (FDA)-approved indocyanine green (ICG) contrast agent is used for labeling and tracking cell distribution and viability using multimodal photoacoustic microscopy (PAM), optical coherence tomography (OCT), and fluorescence imaging.

Methods

Twelve rabbits (2.4–3.4 kg weight, 2–4 months old) were used in the study. Human retinal pigment epithelial cells (ARPE-19) were labeled with ICG dye and transplanted in the subretinal space in the rabbits. Longitudinal PAM, OCT, and fluorescence imaging was performed for up to 28 days following subretinal administration of ARPE-19 cells.

Results

Cell migration location, viability, and cell layer thickness were clearly recognized and determined from the fluorescence, OCT, and PAM signal. The in vivo results demonstrated that fluorescence signal increased 37-fold and PAM signal enhanced 20-fold post transplantation.

Conclusions

This study demonstrates that ICG-assisted PAM, OCT, and fluorescence imaging can provide a unique platform for tracking ARPE-19 cells longitudinally with high resolution and high image contrast.

Translational Relevance

Multimodal PAM, OCT, and fluorescence in vivo imaging with ICG can improve our understanding of the fate, distribution, and function of regenerative cell therapies over time nondestructively.

Enrichment of cancer-initiating cells from colon cancer cells through porous polymeric membranes by a membrane filtration method

Cancer-initiating cells (CICs) or cancer stem cells (CSCs) are primarily responsible for tumor initiation, growth, and metastasis and represent a few percent of the total tumor cell population. We designed a membrane filtration protocol to enrich CICs (CSCs) from the LoVo colon cancer cell line via nylon mesh filter membranes with 11 and 20 μm pore sizes and poly(lactide-co-glycolic acid)/silk screen (PLGA/silk screen) porous membranes (pore sizes of 20-30 μm). The colon cancer cell solution was filtered through the membranes to obtain a permeate solution. Subsequently, the cell culture medium was filtered through the membranes to collect the recovery solution where the cells attached to the membranes were rinsed off into the recovery solution. Then, the membranes were cultivated in the cultivation medium to collect the migrated cells from the membranes. The cells migrated from any membrane had higher expression of the CSC surface markers CD44 and CD133, had higher colony formation levels, and produced more carcinoembryonic antigen (CEA) than the colon cancer cells cultivated on conventional tissue culture plates (control). We established a method to enrich the CICs (CSCs) of colon cancer cells from migrated cells through porous polymeric membranes by the membrane filtration protocol developed in this study.

Generation of uniform liver spheroids from human pluripotent stem cells for imaging-based drug toxicity analysis

Recent advances in pluripotent stem cell technology provide an alternative source of human hepatocytes to overcome the limitations of current toxicity tests. However, this approach requires optimization and standardization before it can be used as a fast and reliable toxicity screening system. Here, we designed and tested microwell culture platforms with various diameters. We found that large quantities of uniformly-sized hepatocyte-like cell (HLC) spheroids (3D-uniHLC-Ss) could be efficiently and reproducibly generated in a short period time from a small number of differentiating human pluripotent stem cells (hPSCs). The hPSC-3D-uniHLC-Ss that were produced in 500-μm diameter microwells consistently exhibited high expressions of hepatic marker genes and had no significant signs of cell death. Importantly, a hepatic master gene hepatocyte nuclear factor 4α (HNF4α) was maintained at high levels, and the epithelial-mesenchymal transition was significantly attenuated in hPSC-3D-uniHLC-Ss. Additionally, when compared with 3D-HLC-Ss that were produced in other 3D platforms, hPSC-3D-uniHLC-Ss showed significantly higher hepatic gene expressions and drug-metabolizing activity of the enzyme, CYP3A4. Imaging-based drug toxicity studies demonstrated that hPSC-3D-uniHLC-Ss exhibited enhanced sensitivity to various hepatotoxicants, compared to HLCs, which were differentiated under 2D conditions. Precise prediction of drug-induced hepatotoxicity is a crucial step in the early phases of drug discovery. Thus, the hPSC-3D-uniHLC-Ss produced using our microwell platform could be used as an imaging-based toxicity screening system to predict drug hepatotoxicity.

Thermoresponsive surfaces designed for the proliferation and differentiation of human pluripotent stem cells

Thermoresponsive surfaces enable the detachment of cells or cell sheets by decreasing the temperature of the surface when harvesting the cells. However, human pluripotent stem cells (hPSCs), such as embryonic stem cells and induced pluripotent stem cells, cannot be directly cultured on a thermoresponsive surface; hPSCs need a specific extracellular matrix to bind to the integrin receptors on their surfaces. We prepared a thermoresponsive surface by using poly(N-isopropylacrylamide-co-butylacrylate) and recombinant vitronectin to provide an optimal coating concentration for the hPSC culture. hPSCs can be cultured on the same thermoresponsive surface for 5 passages by partial detachment of the cells from the surface by decreasing the temperature for 30 min; then, the remaining hPSCs were subsequently cultured on the same dishes following the addition of new cultivation media. The detached cells, even after continual culture for five passages, showed high pluripotency, the ability to differentiate into cells derived from the 3 germ layers and the ability to undergo cardiac differentiation.

A photo-triggered hydrogel for bidirectional regulation with imaging visualization

The bidirectional intelligent regulation of hydrogels is a critical challenge in on-demand functional hydrogels. In this paper, a photo-triggered hydrogel for bidirectional regulation based on IR820-α-cyclodextrin/polyethylene glycol methyl acrylate was developed. This thermosensitive hydrogel can soften from gel to sol under near-infrared irradiation based on the photothermal effect of IR820, while the hydrogel can stiffen based on the photo-crosslinking of polyethylene glycol methyl acrylate under UV laser irradiation. After implanting in vivo, the softness and stiffness of the hydrogel can be regulated in a bidirectional manner by the switching of the irradiation wavelength. Moreover, the location and status of the hydrogel was tracked in vivo by fluorescence imaging due to the fluorescence labeling of IR820. The controlled and visible hydrogel could be potentially applied to different biomedical fields for precise treatment.

Culture and differentiation of purified human adipose-derived stem cells by membrane filtration via nylon mesh filters

Human adipose derived stem cells purified by the membrane migration method through filter membranes coated with vitronectin showed high osteogenic differentiation.