Intravital multiphoton microscopic imaging platform for ocular surface imaging

High-Resolution Imaging of the Ocular Vasculature of Conjunctivitis in Mice Using Highly Bright Polymer Dots

Ocular diseases are mainly caused by vascular aberrations in the eye, and accurate imaging and analysis of the ocular vascular structure is crucial. In this study, poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT) polymer dots (Pdots), with the advantages of easy synthesis, high brightness, and low toxicity, are used as nanoprobes to perform high-resolution imaging of the vasculature of the eyeball and optic nerve. Moreover, rapid imaging of the choroidal microvessels is carried out by stereoscopic fluorescence microscopy with a resolution of up to 1.6 µm. The comprehensive 3D vascular information of retinal aorta and optic nerve microvessels is obtained by combining tissue clearing and multiphoton microscopy. In addition, the vascular density of Schlemm's canal and iris blood vessels is compared between the conjunctivitis mice and the normal mice. These results suggest that PFBT Pdots have great application potential in the fast and accurate imaging of ocular diseases.

Enhanced angiogenic potential of adipose-derived stem cell sheets by integration with cell spheroids of the same source

Background

Adipose-derived stem cell (ASC) has been considered as a desirable source for cell therapy. In contrast to combining scaffold materials with cells, ASCs can be fabricated into scaffold-free three-dimensional (3D) constructs to promote regeneration at tissue level. However, previous reports have found decreased expression of vascular endothelial growth factor (VEGF) in ASC sheets. In this study, we aimed to integrate ASC spheroids into ASC sheets to enhance the angiogenic capability of cell sheets.

Methods

ASCs were seeded in agarose microwells to generate uniform cell spheroids with adjustable size, while extracellular matrix deposition could be stimulated by ascorbic acid 2-phosphate to form ASC sheets. RNA sequencing was performed to identify the transcriptomic profiles of ASC spheroids and sheets relative to monolayer ASCs. By transferring ASC spheroids onto ASC sheets, the spheroid sheet composites could be successfully fabricated after a short-term co-culture, and their angiogenic potential was evaluated in vitro and in ovo.

Results

RNA sequencing analysis revealed that upregulation of angiogenesis-related genes was found only in ASC spheroids. The stimulating effect of spheroid formation on ASCs toward endothelial lineage was demonstrated by enhanced CD31 expression, which maintained after ASC spheroids were seeded on cell sheets. Relative to ASC sheets, enhanced expression of VEGF and hepatocyte growth factor was also noted in ASC spheroid sheets, and conditioned medium of ASC spheroid sheets significantly enhanced tube formation of endothelial cells in vitro. Moreover, chick embryo chorioallantoic membrane assay showed a significantly higher capillary density with more branch points after applying ASC spheroid sheets, and immunohistochemistry also revealed a significantly higher ratio of CD31-positive area.

Conclusion

In the spheroid sheet construct, ASC spheroids can augment the pro-angiogenesis capability of ASC sheets without the use of exogenous biomaterial or genetic manipulation. The strategy of this composite system holds promise as an advance in 3D culture technique of ASCs for future application in angiogenesis and regeneration therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02948-3.

Endoplasmic reticulum protein TXNDC5 promotes renal fibrosis by enforcing TGF-β signaling in kidney fibroblasts

Renal fibrosis, a common pathological manifestation of virtually all types of chronic kidney disease (CKD), often results in diffuse kidney scarring and predisposes to end-stage renal disease. Currently, there is no effective therapy against renal fibrosis. Recently, our laboratory identified an ER-resident protein, thioredoxin domain containing 5 (TXNDC5), as a critical mediator of cardiac fibrosis. Transcriptome analyses of renal biopsy specimens from patients with CKD revealed marked TXNDC5 upregulation in fibrotic kidneys, suggesting a potential role of TXNDC5 in renal fibrosis. Employing multiple fluorescence reporter mouse lines, we showed that TXNDC5 was specifically upregulated in collagen-secreting fibroblasts in fibrotic mouse kidneys. In addition, we showed that TXNDC5 was required for TGF-β1-induced fibrogenic responses in human kidney fibroblasts (HKFs), whereas TXNDC5 overexpression was sufficient to promote HKF activation, proliferation, and collagen production. Mechanistically, we showed that TXNDC5, transcriptionally controlled by the ATF6-dependent ER stress pathway, mediated its profibrogenic effects by enforcing TGF-β signaling activity through posttranslational stabilization and upregulation of type I TGF-β receptor in kidney fibroblasts. Using a tamoxifen-inducible, fibroblast-specific Txndc5 knockout mouse line, we demonstrated that deletion of Txndc5 in kidney fibroblasts mitigated the progression of established kidney fibrosis, suggesting the therapeutic potential of TXNDC5 targeting for renal fibrosis and CKD.

Influence of Human Platelet Lysate on Extracellular Matrix Deposition and Cellular Characteristics in Adipose-Derived Stem Cell Sheets

Adipose-derived stem cell (ASC) is a valuable source of cell therapy. By stimulating extracellular matrix (ECM) secretion, ASC sheets can be fabricated with enhanced regenerative capabilities. In recent years, human platelet lysate (HPL) provides an attractive alternative to fetal bovine serum (FBS) for the ex vivo expansion of ASCs for clinical use. However, the effect of HPL on ASC sheet formation has not been previously determined. In this study, we compared ECM composition and cellular characteristics of ASC sheets cultured in growth medium supplemented with either FBS or HPL. HPL supplement significantly enhanced ASC proliferation without obvious change in the expression pattern of cell surface markers. We found that culturing ASCs with HPL rendered thicker cell sheets with significantly more ECM deposition, including collagen and fibronectin. Proteomic analysis of the FBS or HPL-cultured cell sheets showed diversity in ECM composition. HPL-cultured ASC sheets exhibited up-regulation of interleukin-6 and an anti-inflammatory cytokine, C1q/tumor necrosis factor-related protein-3. Conditioned medium of HPL-cultured ASC sheets significantly enhanced fibroblast migration and tube formation of endothelial cells in vitro, while it inhibited the migration of macrophages toward stimulated macrophages in vitro. TGF-β1-stimulated fibroblasts cultured in ASC sheet-conditioned medium showed down-regulation of α-SMA and TGF-β1. By adding an anti-hepatocyte growth factor (HGF) neutralizing antibody in conditioned medium, we indicated that an anti-fibrosis effect of HPL-cultured ASC sheets is partially mediated through the increased secretion of HGF. Moreover, chick embryo chorioallantoic membrane (CAM) assay showed comparable capillary density after applying either FBS or HPL-cultured ASC sheets, both of which were significantly higher than the control. In conclusion, robust ECM formation with altered ECM composition was noted in ASC sheets cultured in HPL-supplemented medium. Their immunomodulatory and pro-angiogenesis capabilities were largely maintained. Our findings paved the way to elucidate the potential of HPL-cultured ASC sheets for clinical application in tissue regeneration.

Fibroblast-enriched endoplasmic reticulum protein TXNDC5 promotes pulmonary fibrosis by augmenting TGFβ signaling through TGFBR1 stabilization

Pulmonary fibrosis (PF) is a major public health problem with limited therapeutic options. There is a clear need to identify novel mediators of PF to develop effective therapeutics. Here we show that an ER protein disulfide isomerase, thioredoxin domain containing 5 (TXNDC5), is highly upregulated in the lung tissues from both patients with idiopathic pulmonary fibrosis and a mouse model of bleomycin (BLM)-induced PF. Global deletion of Txndc5 markedly reduces the extent of PF and preserves lung function in mice following BLM treatment. Mechanistic investigations demonstrate that TXNDC5 promotes fibrogenesis by enhancing TGFβ1 signaling through direct binding with and stabilization of TGFBR1 in lung fibroblasts. Moreover, TGFβ1 stimulation is shown to upregulate TXNDC5 via ER stress/ATF6-dependent transcriptional control in lung fibroblasts. Inducing fibroblast-specific deletion of Txndc5 mitigates the progression of BLM-induced PF and lung function deterioration. Targeting TXNDC5, therefore, could be a novel therapeutic approach against PF.

Pulmonary fibrosis is a major public health problem with unclear mechanism and limited therapeutic options. Here the authors show that a fibroblast-enriched endoplasmic reticulum protein, TXNDC5, promotes pulmonary fibrosis by stabilizing TGFBR1 and show the potential of TXNDC5 as a therapeutic target against pulmonary fibrosis.

Transgenic models for investigating the nervous system: Currently available neurofluorescent reporters and potential neuronal markers

Recombinant DNA technologies have enabled the development of transgenic animal models for use in studying a myriad of diseases and biological states. By placing fluorescent reporters under the direct regulation of the promoter region of specific marker proteins, these models can localize and characterize very specific cell types. One important application of transgenic species is the study of the cytoarchitecture of the nervous system. Neurofluorescent reporters can be used to study the structural patterns of nerves in the central or peripheral nervous system in vivo, as well as phenomena involving embryologic or adult neurogenesis, injury, degeneration, and recovery. Furthermore, crucial molecular factors can also be screened via the transgenic approach, which may eventually play a major role in the development of therapeutic strategies against diseases like Alzheimer's or Parkinson's. This review describes currently available reporters and their uses in the literature as well as potential neural markers that can be leveraged to create additional, robust transgenic models for future studies.

Long-Term Intravital Imaging of the Cornea, Skin, and Hair Follicle by Multiphoton Microscope

Multiphoton microscopy allows long-term direct visualization of cells in live animals due to its low photodamage. When coupled with fluorescence protein targeting and second harmonic generation signals from natural collagen as contrast, multiphoton microscopy enables intravital tracing of cells while providing structural information from the extracellular matrix. Compared with conventional histological analysis, it can bring new insight into the cell dynamics in stem cell research. Here, we demonstrate cell imaging and tracing at a single cell resolution in the cornea, skin, and hair follicles using multiphoton microscopy in transgenic mice of which specific cell populations are tagged with fluorescent proteins.