optimization-flow-cytometric-sorting-parameters-for-high-throughput

Optimization of Flow Cytometric Sorting Parameters for High-Throughput Isolation and Purification of Small Extracellular Vesicles

Small extracellular vesicles (sEV) can be released from all cell types and carry protein, DNA, and RNA. Signaling molecules serve as indicators of the ...

Zhejiang University School of Medicine

Natural products have always been a major source of therapeutic agents; however, the development of traditional herbal products has been currently hampered by the lack of analytic methods suitable for both high-throughput screening and evaluating the mechanism of action. Cellular processes such as proliferation, apoptosis, and toxicity are well-orchestrated in real time. Monitoring these events and their perturbation by natural products can provide high-rich information about cell physiological relevancies being involved. Here, we report a novel cell-based phenotypic profiling strategy that uses electronic impedance readouts for real-time monitoring of cellular responses to traditional Chinese medicines (TCMs). The utility of this approach was used to screen natural herbs that have been historically documented to cure human diseases and that have been classified into seven clusters based on their mechanisms of action. The results suggest that herbal medicines with similar cellular mechanisms produce similar time/dose-dependent cell response profiles (TCRPs). By comparing the TCRPs produced by the Chinese medicinal Cordyceps sinensis with similar TCRPs of chemical compounds, we explored the potential use of herbal TCRPs for predicting cellular mechanisms of action, herbal authentications, and bioactive identification. Additionally, we further compared this novel TCRP technology with high-performance liquid chromatography (HPLC)-based methods for herbal origin-tracing authentication and identification of bioactive ingredients. Together, our findings suggest that using TCRP as an alternative to existing spectroscopic techniques can allow us to analyze natural products in a more convenient and physiologically relevant manner.

Kinetic cellular phenotypic profiling: prediction, identification, and analysis of bioactive natural products.

Type II alveolar epithelial (AT-II) cells produce pulmonary surfactant proteins that are essential for alveolar function. AT-II is a major target in lung injury, and ineffective repair of damaged alveolar epithelia has been postulated to cause pulmonary fibrosis. Previous studies have shown that tyrosine phosphatase Shp2 is expressed highly in the embryonic lung epithelial buds, and Shp2 activity is required for FGF-induced lung branching morphogenesis. To investigate in vivo function of pulmonary Shp2, we generated alveoli epithelia-specific Shp2-knockout (Shp2(Δ/Δ)) mice. Shp2(Δ/Δ) mice exhibit marked reduction in surfactant proteins, disorganized lamellar bodies, increased alveolar epithelial apoptosis, and interstitial pulmonary fibrosis without preceding inflammation. Mechanistically, Shp2 acts to mediate expression of thyroid transcription factor 1 (TTF1) and ATP-binding cassette subfamily A member 3 (ABCA3). Shp2 also plays a central role in mediating FGF/GAB/ERK activity, required for epithelial repair program. Together, our results identify a novel role of tyrosine phosphatase Shp2 in surfactant homeostasis, and deregulation of Shp2 triggers spontaneous pulmonary fibrosis with minimal inflammation.

Loss of Shp2 in alveoli epithelia induces deregulated surfactant homeostasis, resulting in spontaneous pulmonary fibrosis.

In this work we describe the establishment of mesenchymal stem cells (MSCs) derived from embryonic stem cells (ESCs) and the role of bFGF in adipocyte differentiation. The totipotency of ESCs and MSCs was assessed by immunofluorescence staining and RT-PCR of totipotency factors. MSCs were successfully used to induce osteoblasts, chondrocytes and adipocytes. MSCs that differentiated into adipocytes were stimulated with and without bFGF. The OD/DNA (optical density/content of total DNA) and expression levels of the specific adipocyte genes PPARγ2 (peroxisome proliferator activated receptor γ2) and C/EBPs were higher in bFGF cells. Embryonic bodies had a higher adipocyte level compared with cells cultured in plates. These findings indicate that bFGF promotes adipocyte differentiation. MSCs may be useful cells for seeding in tissue engineering and have enormous therapeutic potential for adipose tissue engineering.

bFGF promotes adipocyte differentiation in human mesenchymal stem cells derived from embryonic stem cells.

To investigate the differentiation potential of purified CD90 cells sorted from adipose-derived stem cells (ADSCs), CD90 cells were sorted from rabbit ADSCs using flow cytometry. Then, cell expansion of CD90 cells and unsorted ADSCs was observed using an inverted microscope. Furthermore, cell surface markers including CD40, CD105, and CD90 on CD90 cells and unsorted ADSCs were quantified using flow cytometry. Additionally, multi-lineage differentiation ability between CD90 cells and unsorted ADSCs was compared, and expression of adipocyte-related genes PPAR-r and CEBPA as well as stem cell-related gene SOX2 in CD90 cells and unsorted ADSCs was determined using real-time quantitative PCR. We found that CD90 cells had a stronger cell proliferation ability than unsorted ADSCs. CD90 cells showed a stronger ability of osteoblast and chondrocyte differentiation than unsorted ADSCs and CD90 cells, whereas the adipose differentiation ability of CD90 cells was similar to that of ADSCs and CD90 cells. CD14, CD105, and CD90 on CD90 cells were expressed more highly than those on ADSCs. Additionally, the mRNA expression level of SOX2 in CD90 cells was significantly higher than that in ADSCs, whereas the expression of PPAR-r and CEBPA was markedly lower than that in ADSCs. These results suggested that the purified CD90 cells sorted from ADSCs exhibit a stronger differentiation potential than the unsorted ADSCs.

Differentiation potential of rabbit CD90-positive cells sorted from adipose-derived stem cells in vitro.

Identification of effective culture conditions to maintain and possibly expand human HSPCs in vitro is an important goal. Recent advances highlight the efficacy of chemicals in maintaining and converting cell fates. We screened 186 chemicals and found that a combination of CHIR-99021, Forskolin and OAC1 (CFO) maintained human CD34-positive cells in vitro. Efficiency of the culture system was characterized using flow cytometry for CD34-positive cells, a colony-forming assay and xeno-transplants. We found that human CD34-positive cells treated with this combination had enhanced expression of human HSPC markers and increased haematopoietic re-populating ability in immune-deficient mice. Single-cell RNA-seq analyses showed that the in vitro cultured human CD34-positive cells were heterogeneous. We found that CFO supports maintenance of human CD34-positive cells by activating ,  and AKT-cAMP signaling pathway. These data have implications in therapies requiring maintenance and/or expansion of human HSPCs.

Maintenance of human haematopoietic stem and progenitor cells in vitro using a chemical cocktail.

Flow cytometric sorting is a vital tool in biological research and clinical diagnostics. Theoretically, a high-speed jet-in-air sorter is a fluorescent-activated cell sorting sorter that ideally processes cells with high purity, yield, and viability. However, high-speed jet-in-air sorting is a complex process due to its inherent requirements for high fluidic stability and electronic and timing precision. Here, we report that an additional manual correction of drop delay leads to improved cell yield. Adding 2% FBS to the loading buffer had no significant effect on the fate of sorted cells in 4 h. However, the addition of a suitable concentration of FBS/BSA in the collecting buffer resulted in a notable increase in cell count and proliferation and a significant decrease in cell apoptosis for cell lines and primary cells. Moreover, the level of gene expression remained steady in the 5% FBS collecting buffer. In summary, here we demonstrate techniques that can be easily followed to refine sorted yields of healthy cells.

Improved strategy for jet-in-air cell sorting with high purity, yield, viability, and genome stability.

Adipose tissue-derived stromal cells are promising candidates investigating the stem cell-related treatment. However, their proportion and utility in the human body decline with time, rendering stem cells incompetent to complete repair processes . The involvement of circRNAs in the aging process is poorly understood. Rat subcutaneous adipose tissue from 10-week-old and 27-month-old rats were used for hematoxylin and eosin (H and E) staining, TUNEL staining, and circRNA sequencing. Rat adipose tissue-derived stromal cells were cultured and overexpressed with circ-ATXN2. Proliferation was examined using xCELLigence real-time cell analysis, EdU staining, and cell cycle assay. Apoptosis was induced by CoCl2 and examined using flow cytometry. RT-PCR assay and Oil Red O staining were used to measure adipogenesis at 48 h and 14 days, respectively. H and E staining showed that the diameter of adipocytes increased; however, the number of cells decreased in old rats. TUNEL staining showed that the proportion of apoptotic cells was increased in old rats. A total of 4,860 and 4,952 circRNAs was detected in young and old rats, respectively. Among them, 67 circRNAs exhibited divergent expression between the two groups (fold change ≥2,  ≤ 0.05), of which 33 were upregulated (49.3%) and 34 were downregulated (50.7%). The proliferation of circ-ATXN2-overexpressing cells decreased significantly , which was further validated by xCELLigence real-time cell analysis, EdU staining, and cell cycle assay. Overexpression of circ-ATXN2 significantly increased the total apoptotic rate from 5.78 ± 0.46% to 11.97 ± 1.61%, early apoptotic rate from 1.76 ± 0.22% to 5.50 ± 0.66%, and late apoptosis rate from 4.02 ± 0.25% to 6.47 ± 1.06% in adipose tissue-derived stromal cells. Furthermore, in circ-ATXN2-overexpressing cells, RT-PCR assay revealed that the expression levels of adipose differentiation-related genes  and  were increased and the Oil Red O staining assay showed more lipid droplets. Our study revealed the expression profile of circRNAs in the adipose tissue of old rats. We found a novel age-related circular RNA-circ-ATXN2-that inhibits proliferation and promotes cell death and adipogenesis in rat adipose tissue-derived stromal cells.

A Novel Age-Related Circular RNA Circ-ATXN2 Inhibits Proliferation, Promotes Cell Death and Adipogenesis in Rat Adipose Tissue-Derived Stromal Cells.

Although widely applied in treating hematopoietic malignancies, transplantation of hematopoietic stem/progenitor cells (HSPCs) is impeded by HSPC shortage. Whether circulating HSPCs (cHSPCs) in steady-state blood could be used as an alternative source remains largely elusive. Here we develop a three-dimensional culture system (3DCS) including arginine, glycine, aspartate, and a series of factors. Fourteen-day culture of peripheral blood mononuclear cells (PBMNCs) in 3DCS led to 125- and 70-fold increase of the frequency and number of CD34 cells. Further, 3DCS-expanded cHSPCs exhibited the similar reconstitution rate compared to CD34 HSPCs in bone marrow. Mechanistically, 3DCS fabricated an immunomodulatory niche, secreting cytokines as TNF to support cHSPC survival and proliferation. Finally, 3DCS could also promote the expansion of cHSPCs in patients who failed in HSPC mobilization. Our 3DCS successfully expands rare cHSPCs, providing an alternative source for the HSPC therapy, particularly for the patients/donors who have failed in HSPC mobilization.

Efficient expansion of rare human circulating hematopoietic stem/progenitor cells in steady-state blood using a polypeptide-forming 3D culture.

Spinal cord injury (SCI) can change the intestinal microbiota pattern and corresponding metabolites, which in turn affect the prognosis of SCI. Among many metabolites, short-chain fatty acids (SCFAs) are critical for neurological recovery after SCI. Recent research has shown that resveratrol exerts anti-inflammatory properties. But it is unknown if the anti-inflammatory properties of resveratrol are associated with intestinal microbiota and metabolites. We thus investigate the alteration in gut microbiota and the consequent change of SCFAs following resveratrol treatment. The SCI mouse models with retention of gut microbiota (donor) and depletion of gut microbiota (recipient) were established. Fecal microbiota transplantation from donors to recipients was performed with intragastrical administration. Spinal cord tissues of mice were examined by H&E, Nissl, and immunofluorescence stainings. The expressions of the inflammatory profile were examined by qPCR and cytometric bead array. Fecal samples of mice were collected and analyzed with 16S rRNA sequencing. The results showed that resveratrol inhibited the microglial activation and promoted the functional recovery of SCI. The analysis of intestinal microbiota and metabolites indicated that SCI caused dysbiosis and the decrease in butyrate, while resveratrol restored microbiota pattern, reversed intestinal dysbiosis, and increased the concentration of butyrate. Both fecal supernatants from resveratrol-treated donors and butyrate suppressed the expression of pro-inflammatory genes in BV2 microglia. Our result demonstrated that fecal microbiota transplantation from resveratrol-treated donors had beneficial effects on the functional recovery of SCI. One mechanism of resveratrol effects was to restore the disrupted gut microbiota and butyrate.

Yanwei Li

Core Facilities

Zhejiang University School of Medicine

Optimization of Flow Cytometric Sorting Parameters for High-Throughput Isolation and Purification of Small Extracellular Vesicles