A Novel 3D Culture Model of Human ASCs Reduces Cell Death in Spheroid Cores and Maintains Inner Cell Proliferation Compared With a Nonadherent 3D Culture

3D cell culture technologies have recently shown very valuable promise for applications in regenerative medicine, but the most common 3D culture methods for mesenchymal stem cells still have limitations for clinical application, mainly due to the slowdown of inner cell proliferation and increase in cell death rate. We previously developed a new 3D culture of adipose-derived mesenchymal stem cells (ASCs) based on its self-feeder layer, which solves the two issues of ASC 3D cell culture on ultra-low attachment (ULA) surface. In this study, we compared the 3D spheroids formed on the self-feeder layer (SLF-3D ASCs) with the spheroids formed by using ULA plates (ULA-3D ASCs). We discovered that the cells of SLF-3D spheroids still have a greater proliferation ability than ULA-3D ASCs, and the volume of these spheroids increases rather than shrinks, with more viable cells in 3D spheroids compared with the ULA-3D ASCs. Furthermore, it was discovered that the SLF-3D ASCs are likely to exhibit the abovementioned unique properties due to change in the expression level of ECM-related genes, like COL3A1, MMP3, HAS1, and FN1. These results indicate that the SLF-3D spheroid is a promising way forward for clinical application.

Promising Preliminary Activity of Optimized Affinity, CD38 CAR NK Cells Generated Using a Non-Viral Engineering Approach in Gene Edited Cord Blood Derived NK Cells for the Treatment of Multiple Myeloma

CD38 is a multifunctional cell surface protein that is frequently overexpressed on malignant plasma cells as well as on immune suppressive cells within the tumor microenvironment and constitutes a validated immunotherapeutic target in the treatment of multiple myeloma (MM). At ONK Therapeutics we are developing a gene edited, cord blood-derived NK (CBNK) cell product targeting CD38 for treatment of patients with relapsed and/or refractory MM. The product will be generated using a workflow shown in Figure 1A. This involves starting with cord blood that is processed for NK expansion using a clinically validated, Epstein Barr Virus-transformed lymphoblastoid cell line (EBV-LCL) feeder layer. The NK cells would undergo genetic engineering that involves gene editing followed by a non-viral chimeric antigen receptor (CAR) introduction process mediated by the TcBuster (TcB) DNA transposon system (Biotechne). This is followed by a second round of expansion on the EBV-LCL feeder layer resulting in a characterized NK cell product that can then be cryopreserved. In order to develop protocols for optimizing the best transfection efficiencies using the Maxcyte ATx instrument, GFP mRNA (TriLink) was used for transfecting CBNK cells using different electroporation programs. High transfection efficiency was obtained using all programs (Figure 1B.), with the best from program NK4. Since the product employs an optimized affinity second generation anti CD38 CAR (Stikvoort et al., Hemasphere 2021) which could also target CD38 expressed on neighbouring activated NK cells, it is imperative to knock out (KO) the cell surface expression of CD38 on the CAR-NK cells. To achieve this we carried out CRISPR Cas9 based KO studies of CD38 (Figure 1C. left top), using guide RNAs targeting CD38 (Synthego) in the form of a ribonucleoprotein (RNP) complex with Cas9. CBNK cells were transfected using the Maxcyte ATx instrument and CD38 cell surface expression monitored. As shown in Figure 1C. (left top), complete CD38 KO was achieved 11 days post transfection. ONK Therapeutics is actively involved in targeting and downregulating the negative regulator of cytokine signalling, cytokine inducible SH2-containing protein (CIS), which is encoded by the CISH gene, as part of their CBNK products. It has been demonstrated that in addition to facilitating greater cytokine signalling, CISH KO also confers greater metabolic capacity to NK cells resulting in their increased persistence (Daher et al., Blood 2021). Therefore, ONK Therapeutics have evaluated CISH KO in CBNK cells (Figure 1C, top right) using the same scheme that was used for the CD38 KO. Guide RNAs in the form of a RNP complex with Cas9 (Synthego) were transfected into CBNK cells and intracellular CIS protein levels monitored over time. Almost complete KO was attained by 9 days post transfection. In order to dial in CISH KO as part of the product, we further carried out a simultaneous KO of CD38 and CISH, in addition to individual KO of CD38 or CISH (Fig 1C, bottom). Simultaneous multiplexing of the CD38 and CISH KOs resulted in efficient double KO (DKO) . The extent of knock down leading to KO in the DKO setting was very similar to that of individual gene KOs. We then introduced the anti CD38 CAR as part of a transposon that could be transposed by TcB transposase in CBNK cells. After DKO of CD38 and CISH in CBNK cells, the transposon DNA and mRNA for transposase were electroporated. CAR expression was detected 4-5 days post transposition (Figure 1D) with more than 50% of cells expressing the anti CD38 CAR. These CAR expressing CBNK cells were then tested for functionality in a co-culture kill assay against the CD38 positive MM cell line, RPMI8226, which was engineered to express firefly luciferase. In a 4 hour killing assay, robust killing of the RPMI8226 cells was achieved by the CAR-CBNK cells with an EC 50 ten times lower (more potent) than that of mock electroporation control CBNK cells. To our knowledge this is the first successful expression of an anti CD38 CAR in cord-derived NK cells, and with a double CD38/CISH KO, using non-viral CAR insertion approaches. Current work is focusing on designing and developing a manufacturing-ready workflow for this potential product and further examining the effects of CAR NK cell activity in a DKO setting where both KOs contribute to improved metabolism and potentially NK cell persistence, as well as exploring the added benefit of a DR5 TRAIL variant to enhance cytotoxicity. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

The role of quercetin in primary culture of ovine spermatogonial stem cells

The aim of the present study was to examine the effect of quercetin on the survival and primary culture of ovine spermatogonial stem cells (SSCs). The two-time enzymatic digestion process was employed to obtain SSCs from lamb testes. In the next step, the use of filtration and differential plating methods caused an increase in the number of SSCs in the cell suspension resulting from enzymatic and mechanical digestions. Mitomycin-C-treated Sertoli cells were used to prepare the feeder layer. The stem cells were then cultured on the Sertoli cell feeder layer. The identification of the colonies was done through alkaline phosphatase staining methods and specific gene expression of ram’s SSCs (nanog and Plzf). The results of methylthiazolyldiphenyl-tetrazolium bromide assay on SSCs 72 h after culture with different treatments of quercetin demonstrated that the highest percentage of survival was for 5 μM and 10 μM concentrations, respectively; however, compared to the control, no significant difference was observed. In comparison with the control, the concentration equal to and greater than 20 μM quercetin caused a significant decrease in the survival of SSCs (P < 0.05). Seven days after culture, 40 μM quercetin caused a substantial reduction in the mean number of colonies, compared to the control (P < 0.05). The results demonstrated that compared to the control, 5 μM to 40 μM of quercetin significantly reduced Plzf gene expression. Furthermore, the concentration equal to and higher than 10 μM quercetin significantly decreased bcl-2 gene expression in the cells under study (P < 0.05). Based on the findings of the present study, the use of quercetin for the primary culture of ovine SSCs is not recommended. It is suggested that the function of this antioxidant should be investigated on the differentiation of SSCs.

Extracellular cues accelerate neurogenesis of induced pluripotent stem cell derived neurons

Neurogenesis is a complex process encompassing neuronal progenitor cell expansion/proliferation and differentiation, followed by neuron maturation. In vivo models are most commonly used to study neurogenesis; however, human induced pluripotent stem cell-derived (iPSC) neurons are increasingly used to establish cellular models of human neurological processes. Unfortunately, the differentiation and maturation of iPSC-derived neurons varies in methodology, is asynchronous, and has restricted experimental utility because of extended differentiation/maturation times. To accelerate and standardize iPS neuronal maturation, we differentiated and matured feeder layer-free iPSC-derived neuronal cultures under physiological oxygen levels (5%), and modified the underlying extracellular matrix and medium composition. Our results demonstrate that calretinin gene expression occurred earlier under our optimized iPS conditions and the corresponding neurogenesis burst associated with proliferative expansion occurred more synchronously, reliably emerging two and three weeks after differentiation. As expected, the expression of mature neuronal markers (i.e., NeuN+/Calbindin+) started at 4-weeks post-differentiation. qPCR microarray, western blot and single cell analyses using high content imaging indicated that 4-week iPS neuronal cultures were non-cycling with decreased expression of cyclin D1 and Ki67. Our data demonstrate that extracellular cues influence the kinetics of neurogenesis models and that feeder layer-free iPSC-derived neurogenesis can be reproducibly miniaturized.

Oxidation and RGD Modification Affect the Early Neural Differentiation of Murine Embryonic Stem Cells Cultured in Core-Shell Alginate Hydrogel Microcapsules

Directed neural differentiation of embryonic stem cells (ESCs) has been studied extensively to improve the treatment of neurodegenerative disorders. This can be done through stromal-cell derived inducing activity (SDIA), by culturing ESCs directly on top of a layer of feeder stromal cells. However, the stem cells usually become mixed with the feeder cells during the differentiation process, making it difficult to obtain a pure population of the differentiated cells for further use. To address this issue, a non-planar microfluidic device is used here to encapsulate murine ESCs (mESCs) in the 3D liquid core of microcapsules with an alginate hydrogel shell of different sizes for early neural differentiation through SDIA, by culturing mESC-laden microcapsules over a feeder layer of PA6 cells. Furthermore, the alginate hydrogel shell of the microcapsules is modified via oxidation or RGD peptide conjugation to examine the mechanical and chemical effects on neural differentiation of the encapsulated mESC aggregates. A higher expression of Nestin is observed in the aggregates encapsulated in small (∼300 μm) microcapsules and cultured over the PA6 cell feeder layer. Furthermore, the modification of the alginate with RGD facilitates early neurite extension within the microcapsules. This study demonstrates that the presence of the RGD peptide, the SDIA effect of the PA6 cells, and the absence of leukemia inhibition factor from the medium can lead to the early differentiation of mESCs with extensive neurites within the 3D microenvironment of the small microcapsules. This is the first study to investigate the effects of cell adhesion and degradation of the encapsulation materials for directed neural differentiation of mESCs. The simple modifications (i.e., oxidation and RGD incorporation) of the miniaturized 3D environment for improved early neural differentiation of mESCs may potentially enhance further downstream differentiation of the mESCs into more specialized neurons for therapeutic use and drug screening.

Measurement of the Bio-Mechanical Properties of Two Different Feeder Layer Cells

Introduction: We here present our findings on 2 types of feeder layers, one composed of mouse embryonic fibroblasts (MEF) and the second one of mouse skeletal myoblasts (C2Cl2) feeder cells. Methods: The 2 feeder layers present a dramatic variance of intrinsic stiffness (142.68 ± 17.21 KPa and 45.78 ± 9.81 KPa, respectively). Results and Conclusion: This information could be used for a better understanding of cells and cell microenvironment mechano-physical characteristics that are influencing stem cell commitment, in order to develop a suitable engineered tissue for cardiac and skeletal muscle repair and a bio-actuator.

In Vitro Culture of Chicken Circulating and Gonadal Primordial Germ Cells on a Somatic Feeder Layer of Avian Origin

The present study had two aims: (1) To develop a culture system that imitates a normal physiological environment of primordial germ cells (PGCs). There are two types of PGCs in chicken: Circulating blood (cPGCs) and gonadal (gPGCs). The culture condition must support the proliferation of both cPGCs and gPGCs, without affecting their migratory properties and must be deprived of xenobiotic factors, and (2) to propose an easy-to-train, nonlabeling optical technique for the routine identification of live PGCs. To address the first aim, early chicken embryo’s feeder cells were examined instead of using feeder cells from mammalian species. The KAv-1 medium at pH 8.0 with the addition of bFGF (basic fibroblast growth factor) was used instead of a conventional culture medium (pH approximately 7.2). Both cPGCs and gPGCs proliferated in vitro and retained their migratory ability after 2 weeks of culture. The cultivated cPGCs and gPGCs colonized the right and/or left gonads of the recipient male and female embryos. To address the second aim, we demonstrated a simple and rapid method to identify live PGCs as bright cells under darkfield illumination. The PGCs rich in lipid droplets in their cytoplasm highly contrasted with the co-cultured feeder layer and other cell populations in the culture.

231 Novel protocol for the invitro maintenance and expansion of adult epidermal LGR5+ stem cells

Currently, the standard for treatment of full-thickness skin wounds is skin grafts or bioengineered skin substitutes; however, this method is limited by the amount of intact donor skin and lack of follicles and architecture. Thus, a protocol is needed for the expansion and differentiation of adult epidermal and hair follicle stem cells for use in scaffold mediated tissue engineering. Recently, we developed a transgenic porcine model in which H2B-GFP is under the control of the LGR5 promoter. LGR5 is an established marker of stem cells, meaning this model can be used to track the development and behaviour of these cells. The focus of this project was to create a novel culture method for the maintenance and expansion of LGR5+ epidermal adult stem cells utilising the green fluorescent protein (GFP) tag. Single cell epidermal stem cells were isolated from porcine skin using dispase II (10mgmL−1; Sigma) and trypsin (0.05%; Corning). Porcine fetal fibroblasts (PFF) or mouse embryonic fibroblasts (MEF) were grown to 95% confluence in a 6-well plate. Feeder layer cells were mitotically inactivated by incubation with mitomycin C (Sigma Aldrich, 10μgmL−1). Three different media were tested: basal medium [Dulbecco's modified Eagle's medium (DMEM), penicillin/streptomycin, Corning; Ham's F12, ThermoFisher; fetal bovine serum, Gemini Bio-Products], basal media + 5-azacytidine (Sigma Aldrich) and CHIR99021 (Tocris), or basal media + keratinocyte growth supplements (transferrin, hydrocortisone, T3, adenine, insulin, cholera toxin; Sigma Aldrich, epidermal growth factor; R&D Systems). Epidermal cells were plated in each medium for both PFF and MEF feeder layers. Experiments were performed in technical duplicates and replicated 3 times. On Day 9, total numbers of colonies in each well were counted and number of GFP-positive cells were quantified using ImageJ (National Institutes of Health). Results in Table 1 show that overall, the MEF feeder layer was able to support a higher rate of growth (P<0.05) and maintain the LGR5+ lineage at a higher proportion under all of the experimental conditions (P<0.05). In the growth-supplemented media, MEFs had fewer colonies than PFFs, but MEF colonies were, on average, 2.5 times larger (P<0.05). Conditions containing 5-aza and CHIR were the only conditions to maintain the LGR5+ lineage on the feeder layer. Statistically significant differences (P<0.05) were determined using two-way ANOVA, followed by Tukey's HSD test. Next, LGR5+ cells will be plated in media containing additional growth factors to stimulate expansion, while using CHIR and 5-aza to maintain the LGR5+ lineage. This protocol could be used in scaffolds to create three-dimensional growth of skin invitro and lead to better grafts for burn victims. Table 1.Growth of LGR5+ cells in different media including 5-azacytidine (5-aza), CHIR 99021 (CHIR), and keratinocyte growth supplements Group1 Basal medium (BM) BM + 5-aza+ CHIR BM + growth supplements No. of colonies/well MEF 127.7±40.8AB 189.3±16.9A 87.3±14.6B PFF 65.0±14.1A 83.3±17.0AB 148±33.7B Average no. of GFP+ cells per frame MEF 0.5±0.8B 65.7±18.4A 1.8±1.7B PFF 0.9±1.0B 22.6±4.5A 0.3±0.6B A,BValues within rows with different superscripts differ (P ≤ 0.05). 1MEF=mouse embryonic fibroblasts; PFF=porcine fetal fibroblasts.