Breaking limitations of complex culture media: functional non-viral miRNA delivery into pharmaceutical production cell lines

Stable overexpression of native and artificial miRNAs for the production of differentially fucosylated antibodies in CHO cells

Cell engineering strategies typically rely on energy-consuming overexpression of genes or radical gene-knock out. Both strategies are not particularly convenient for the generation of slightly modulated phenotypes, as needed in biosimilar development of for example differentially fucosylated monoclonal antibodies (mAbs). Recently, transiently transfected small noncoding microRNAs (miRNAs), known to be regulators of entire gene networks, have emerged as potent fucosylation modulators in Chinese hamster ovary (CHO) production cells. Here, we demonstrate the applicability of stable miRNA overexpression in CHO production cells to adjust the fucosylation pattern of mAbs as a model phenotype. For this purpose, we applied a miRNA chaining strategy to achieve adjustability of fucosylation in stable cell pools. In addition, we were able to implement recently developed artificial miRNAs (amiRNAs) based on native miRNA sequences into a stable CHO expression system to even further fine-tune fucosylation regulation. Our results demonstrate the potential of miRNAs as a versatile tool to control mAb fucosylation in CHO production cells without adverse side effects on important process parameters.

miR-210 promotes immune- and suppresses oocyte meiosis-related genes in the zebrafish ovarian cells

microRNA-210 (miRNA), a well-documented miRNA, has been implicated in a myriad of biological processes, including responses to hypoxia, angiogenesis, cell proliferation, and male infertility in humans. However, a comprehensive understanding of its functions in fish requires further investigation. This study pursued to elucidate the downstream effect of dre-miR-210-5p on primary ovarian cell culture in zebrafish (Danio rerio), an animal model. A protocol was settled down by incubations with either an miR-210 mimic or a scrambled miRNA in the isolated ovaries. RNA-sequencing analysis identified ∼6000 differentially expressed target genes revealing that downregulated genes were associated with reproduction-related pathways while immune-related pathways displayed an upregulated pattern. To identify molecular markers, predicted target genes were classified into reproduction and immune cell types. These findings underscore the existence of a profound interplay between the reproductive and immune systems, with miR-210 emerging as a pivotal player in orchestrating transcriptomic alterations within fish ovaries.

RNAi-Mediated Silencing in the Insect Cell-Baculovirus Expression System

RNA interference (RNAi) serves as an indispensable tool for gene function studies and has been substantiated through extensive research for its practical applications in the baculovirus expression vector system (BEVS). This chapter expands the RNAi toolkit in insect cell culture by including small interfering RNA (siRNA) in the protocol, in addition to the conventional use of double-stranded RNA (dsRNA). This chapter also brings attention to key design and reporting considerations, based on Minimum Information About an RNAi Experiment (MIARE) guidelines. Recommendations regarding online tools for dsRNA and siRNA design are provided, along with guidance on choosing suitable methods for measuring silencing outcomes.

Comparison of different types of liposomal nano structures for microRNA transfection to human mesenchymal stem cell line S1939

Background: Liposomes are utilized as a drug delivery carrier in various fields of biomedicine. They are synthesized in the nanometer-size range and are becoming a viable drug delivery carrier for the treatment of different diseases. MicroRNAs as regulatory elements could be transferred to cells for changing their morphology or physiology. The study's major aim is to find the optimized formula of liposomes for transfection of microRNA to human mesenchymal stem cell line S1939 (HMSCs). Materials and Methods: Various ratios of soybean phosphatidylcholine (SPC), cholesterol, 1, 2 dioleoyloxy-3- (trimethylammonium) propane (DOTAP), and polyethylene glycol (PEG) were combined. The mean diameter of all formulations and their surface properties were determined by a zeta sizer device and scanning electron microscope, respectively. The cytotoxicity of formulations was assessed using MTT (3,4,5-dimethyl thiazol-2-yl) (2,5-diphenyltetrazolium bromide) assay. The transfection effectiveness of liposomal miRNA vs empty liposomes was determined using agarose gel electrophoresis. Results: The optimized liposome vesicles were prepared using 45:30:27.5:5 molar ratios of SPC:DOTAP:cholesterol: DSPE-PEG. The liposome formulations F10 and F18 were the best in terms of biocompatibility because of the higher viabilities of treated cells. The best formulation (F18, containing 0.7 µg of miRNA and 10 µg of liposome) was nearly 100% efficient in sequestering and fixing miRNA. Phase-contrast and fluorescent microscopic examinations showed intra-nuclear as well as intracytoplasmic localization of the particles. Conclusion: Some easily prepared liposomal formulation vehicles are quite efficient in the transfection of miRNA into the HMSCs and could be used for in vitro applications in regenerative medicine.

Loss of a Newly Discovered microRNA in Chinese Hamster Ovary Cells Leads to Upregulation of NGNA Sialylation on Monoclonal Antibodies

Chinese hamster ovary (CHO) cells are known not to express appreciable levels of the sialic acid residue N‐glycolylneuraminic acid (NGNA) on monoclonal antibodies. However, we actually have identified a recombinant CHO cell line expressing an IgG with unusually high levels of NGNA sialylation (>30%). Comprehensive multi‐OMICs based experimental analyses unraveled the root cause of this atypical sialylation: (1) expression of the cytidine monophosphate‐N‐acetylneuraminic acid hydroxylase (CMAH) gene was spontaneously switched on, (2) CMAH mRNA showed an anti‐correlated expression to the newly discovered Cricetulus griseus (cgr) specific microRNA cgr‐miR‐111 and exhibits two putative miR‐111 binding sites, (3) miR‐111 expression depends on the transcription of its host gene SDK1, and (4) a single point mutation within the promoter region of the sidekick cell adhesion molecule 1 (SDK1) gene generated a binding site for the transcriptional repressor histone H4 transcription factor HINF‐P. The resulting transcriptional repression of SDK1 led to a downregulation of its co‐expressed miR‐111 and hence to a spontaneous upregulation of CMAH expression finally increasing NGNA protein sialylation.

A blueprint from nature: miRNome comparison of plasma cells and CHO cells to optimize therapeutic antibody production

Chinese Hamster Ovary (CHO) cells are the most frequently used biopharmaceutical production hosts, although industry is presently suffering from their variable recombinant product quality, insufficient long-term stability and low productivity. Here, we present an effort to address overall cell line engineering by a novel bottom-up microRNA (miRNA) screening approach. miRNAs are small non-coding RNAs known to regulate global gene expression at the post-transcriptional level and have proved to serve as promising tools for cell line engineering for over a decade. Here the miRNome of plasma cells (PCs) has been analyzed as the natural blueprint for optimized production and secretion of antibodies. Performing comparative miRNome cross-species expression analysis of four murine/human PC-derived (PCD) and two CHO cell lines showed 147 conserved miRNAs to be differentially expressed between PCDs and CHOs. Conducting a targeted miRNA screen of this PC-specific miRNA subset revealed 14 miRNAs to improve bioprocess relevant parameters in CHO cells, among them the PC-characteristic miR-183 cluster. Finally, miRNA target prediction tools and transcriptome analysis were combined to elucidate differentially regulated lysine degradation and fatty acid metabolism pathways in monoclonal antibody (mAb) expressing CHO-DG44 and CHO-K1 cells, respectively. Thus, substantial new insights into molecular and cellular mechanisms of biopharmaceutical production cell lines can be gained by targeted bottom-up miRNA screenings.

Transferability of miRNA-technology to bioprocessing: Influence of cultivation mode and media

The biopharmaceutical industry strives for improvement of their production processes. In recent years, miRNAs have been shown to positively impact the production capacity of recombinant CHO cells, especially with regard to difficult to express proteins. Effective and reliable gene regulation of process relevant target genes by miRNAs is a prerequisite for integrating them into the toolbox of industrial cell engineering strategies. However, most studies rely on transient transfection of miRNA mimics; there is low standardization in evaluation of miRNA function and little knowledge on transferability of effects found during transient expression to stable expression during industry relevant fed‐batch cultivation. In order to provide more insight into this topic, we used the pcDNA6.2 vector for stable miRNA overexpression during batch and fed‐batch cultivation in CHO DG44 cells, optimized the vector, and compared the miRNA levels and effects with those achieved by transfection of miRNA mimics. We found that miR‐1 downregulated TWF1 mRNA in different recombinant CHO DG44 clones in a dose‐dependent manner during transient batch cultivation. Cells stably overexpressing miR‐1 also showed a TWF1 mRNA downregulation when cultivated in batch mode using in‐house medium 1. However, when the cells stably overexpressing miR‐1 were cultivated in fed‐batch mode using in‐house medium 2. Consequently, a change of cultivation mode and medium seems to have an impact on target gene regulation by miRNA. Taken together, our findings highlight the importance to standardize miRNA evaluations and test miRNAs in the final application environment.

Transient manipulation of the expression level of selected growth rate correlating microRNAs does not increase growth rate in CHO-K1 cells

Engineering of Chinese Hamster Ovary cells by manipulating microRNA (miRNA) expression levels has been shown to induce advantageous, desired phenotypes. Most of these studies so far were concerned with increasing productivity or reducing growth rate (with the implied intention of thus freeing cellular resources to also increase productivity). Here we evaluated the ability of growth correlating miRNAs to increase the growth rate of CHO-K1 cells by transient overexpression or knock down, respectively. Candidates were selected based on the correlation between growth rate and miRNA expression levels as observed in previous studies. These candidates were then up- or downregulated initially by transfection of mimics or inhibitors and subsequently by transfection of plasmids bearing the corresponding miRNAs or sponges. None of the 40 selected candidates was able to induce a better growth phenotype under these conditions. Overlap between miRNAs identified to correlate to growth in published miRNA expression studies and those identified to actively increase growth rate in a functional screen is minimal, indicating that the here selected approach of traditional overexpression/knock down engineering of miRNAs may not be a suitable strategy for the purpose of increasing growth rate.

Induction of apoptosis in ovarian cancer cells by miR-493-3p directly targeting AKT2, STK38L, HMGA2, ETS1 and E2F5

Apoptosis is a form of directed programmed cell death with a tightly regulated signalling cascade for the destruction of single cells. MicroRNAs (miRNAs) play an important role as fine tuners in the regulation of apoptotic processes. MiR-493-3p mimic transfection leads to the induction of apoptosis causing the breakdown of mitochondrial membrane potential and the activation of Caspases resulting in the fragmentation of DNA in several ovarian carcinoma cell lines. Ovarian cancer shows with its pronounced heterogeneity a very high death-to-incidence ratio. A target gene analysis for miR-493-3p was performed for the investigation of underlying molecular mechanisms involved in apoptosis signalling pathways. Elevated miR-493-3p levels downregulated the mRNA and protein expression levels of Serine/Threonine Kinase 38 Like (STK38L), High Mobility Group AT-Hook 2 (HMGA2) and AKT Serine/Threonine Kinase 2 (AKT2) by direct binding as demonstrated by luciferase reporter assays. Notably, the protein expression of RAF1 Proto-Oncogene, Serine/Threonine Kinase (RAF1) was almost completely downregulated by miR-493-3p. This interaction, however, was indirect and regulated by STK38L phosphorylation. In addition, RAF1 transcription was diminished as a result of reduced transcription of ETS proto-oncogene 1 (ETS1), another direct target of miR-493-3p. Taken together, our observations have uncovered the apoptosis inducing potential of miR-493-3p through its regulation of multiple target genes participating in the extrinsic and intrinsic apoptosis pathway.

MiR-744-5p inducing cell death by directly targeting HNRNPC and NFIX in ovarian cancer cells

MicroRNAs (miRNAs) play an important role in the regulation of gene expression. The binding to target messenger RNAs (mRNAs) results in mRNA cleavage or inhibition of the translational machinery leading to decreased protein levels. Various signalling pathways, including apoptosis are modulated by miRNAs. Here, we investigated the role of miR-744-5p in apoptosis signalling in ovarian cancer cell lines. MiR-744-5p expression was reduced in the cancer cell lines independent of the host gene MAP2K4. Overexpression of miR-744-5p activated the intrinsic apoptotic pathway in SKOV3, OVCAR3 and Cisplatin resistant (A2780-cis) and non-resistant A2780 cells leading to cell death. Notably, miR-744-5p overexpression together with Carboplatin treatment led to at least additive pro-apoptotic effects. Investigation of the apoptotic signalling pathways mediated by miR-744-5p revealed that its elevated expression directly downregulated mRNA and protein expression of nuclear factor I X (NFIX) and heterogeneous nuclear ribonucleoprotein C (HNRNPC). HNRNPC caused diminished miR-21 expression and AKT phosphorylation, while NFIX decreased Bcl2 levels, leading to the detected pro-apoptotic effects. Finally, Kaplan-Meier-Plots showed a prolonged median disease-free survival in ovarian serous cystadenocarcinoma patients with high miR-744 expression.

Stable miRNA overexpression in human CAP cells: Engineering alternative production systems for advanced manufacturing of biologics using miR-136 and miR-3074

Chinese hamster ovary (CHO) cells still represent the major production host for therapeutic proteins. However, multiple limitations have been acknowledged leading to the search for alternative expression systems. CEVEC's amniocyte production (CAP) cells are human production cells demonstrated to enable efficient overexpression of recombinant proteins with human glycosylation pattern. However, CAP cells have not yet undergone any engineering approaches to optimize process parameters for a cheaper and more sustainable production of biopharmaceuticals. Thus, we assessed the possibility to enhance CAP cell production capacity via cell engineering using miRNA technology. Based on a previous high-content miRNA screen in CHO-SEAP cells, selected pro-productive miRNAs including, miR-99b-3p, 30a-5p, 329-3p, 483-3p, 370-3p, 219-1-3p, 3074-5p, 136-3p, 30e-5p, 1a-3p, and 484-5p, were shown to act pro-productive and product independent upon transient transfection in CAP and CHO antibody expressing cell lines. Stable expression of miRNAs established seven CAP cell pools with an overexpression of the pro-productive miRNA strand. Subsequent small-scale screening as well as upscaling batch experiments identified miR-136 and miR-3074 to significantly increase final mAb concentration in CAP-mAb cells. Transcriptomic changes analyzed by microarrays identified several lncRNAs as well as growth and apoptosis-related miRNAs to be differentially regulated in CAP-mAb-miR-136 and -miR-3074. This study presents the first engineering approach to optimize the alternative human expression system of CAP-cells.

Analysis of Gene Regulatory Networks of Maize in Response to Nitrogen

Nitrogen (N) fertilizer has a major influence on the yield and quality. Understanding and optimising the response of crop plants to nitrogen fertilizer usage is of central importance in enhancing food security and agricultural sustainability. In this study, the analysis of gene regulatory networks reveals multiple genes and biological processes in response to N. Two microarray studies have been used to infer components of the nitrogen-response network. Since they used different array technologies, a map linking the two probe sets to the maize B73 reference genome has been generated to allow comparison. Putative Arabidopsis homologues of maize genes were used to query the Biological General Repository for Interaction Datasets (BioGRID) network, which yielded the potential involvement of three transcription factors (TFs) (GLK5, MADS64 and bZIP108) and a Calcium-dependent protein kinase. An Artificial Neural Network was used to identify influential genes and retrieved bZIP108 and WRKY36 as significant TFs in both microarray studies, along with genes for Asparagine Synthetase, a dual-specific protein kinase and a protein phosphatase. The output from one study also suggested roles for microRNA (miRNA) 399b and Nin-like Protein 15 (NLP15). Co-expression-network analysis of TFs with closely related profiles to known Nitrate-responsive genes identified GLK5, GLK8 and NLP15 as candidate regulators of genes repressed under low Nitrogen conditions, while bZIP108 might play a role in gene activation.

Investigation on tissue specific effects of pro-apoptotic micro RNAs revealed miR-147b as a potential biomarker in ovarian cancer prognosis

The development and progression of cancer can be ascribed to imbalances in gene regulation leading to aberrant cellular behavior. The loss of micro RNAs (miRNAs) exhibiting tumor-suppressive function has been demonstrated to be often causative for uncontrolled cell proliferation, migration or tissue infiltration. The installation of de novo tumor suppressive function by using pro-apoptotic miRNAs might be a promising therapeutic approach. In addition, there is a great demand for novel biomarkers for the prognosis of cancer, which prompted us to transfer a high content miRNA screening initially performed to identify bioprocess relevant miRNAs in Chinese hamster ovary (CHO) cells to human cancer cell lines . Analysis of screened miRNAs exhibiting strongest pro-apoptotic effects discovered globally and cross-species active candidates. The recovery rate of apoptosis inducing miRNAs was highest in the human ovarian carcinoma cell line SKOV3. Focusing on ovarian cell lines miR-1912, miR-147b and miR-3073a showed significant apoptosis induction in cell lines with different genetic background (SKOV3^p53null, OVCAR3^p53R248Q, TOV21G, TOV112D^p53R175H, A2780, A2780-cis^p53K351N) alone and additive effects in combination with carboplatin. While expression analysis revealed a low endogenous expression of miR-1912 and miR-147b in SKOV3, miRNA expression was highly upregulated upon apoptosis induction using chemotherapeutics. Ectopic introduction of these miRNAs lead to enhanced activation of caspase-dependent death signaling and an induction of the pro-apoptotic proteins Bak1 and Bax and a reduced expression of Bcl2 and Bcl-xL. Finally, analysis of The Cancer Genome Atlas data revealed the expression of hsa-miR-147b-5p to show a positive influence on the median survival of ovarian cancer patients.

miRNA engineering of CHO cells facilitates production of difficult-to-express proteins and increases success in cell line development

In recent years, coherent with growing biologics portfolios also the number of complex and thus difficult-to-express (DTE) therapeutic proteins has increased considerably. DTE proteins challenge bioprocess development and can include various therapeutic protein formats such as monoclonal antibodies (mAbs), multi-specific affinity scaffolds (e.g., bispecific antibodies), cytokines, or fusion proteins. Hence, the availability of robust and versatile Chinese hamster ovary (CHO) host cell factories is fundamental for high-yielding bioprocesses. MicroRNAs (miRNAs) have emerged as potent cell engineering tools to improve process performance of CHO manufacturing cell lines. However, there has not been any report demonstrating the impact of beneficial miRNAs on industrial cell line development (CLD) yet. To address this question, we established novel CHO host cells constitutively expressing a pro-productive miRNA: miR-557. Novel host cells were tested in two independent CLD campaigns using two different mAb candidates including a normal as well as a DTE antibody. Presence of miR-557 significantly enhanced each process step during CLD in a product independent manner. Stable expression of miR-557 increased the probability to identify high-producing cell clones. Furthermore, production cell lines derived from miR-557 expressing host cells exhibited significantly increased final product yields in fed-batch cultivation processes without compromising product quality. Strikingly, cells co-expressing miR-557 and a DTE antibody achieved a twofold increase in product titer compared to clones co-expressing a negative control miRNA. Thus, host cell engineering using miRNAs represents a promising tool to overcome limitations in industrial CLD especially with regard to DTE proteins. Biotechnol. Bioeng. 2017;114: 1495-1510. © 2017 Wiley Periodicals, Inc.

Delivering Nucleic-Acid Based Nanomedicines on Biomaterial Scaffolds for Orthopedic Tissue Repair: Challenges, Progress and Future Perspectives

As well as acting to fill defects and allow for cell infiltration and proliferation in regenerative medicine, biomaterial scaffolds can also act as carriers for therapeutics, further enhancing their efficacy. Drug and protein delivery on scaffolds have shown potential, however, supraphysiological quantities of therapeutic are often released at the defect site, causing off-target side effects and cytotoxicity. Gene therapy involves the introduction of foreign genes into a cell in order to exert an effect; either replacing a missing gene or modulating expression of a protein. State of the art gene therapy also encompasses manipulation of the transcriptome by harnessing RNA interference (RNAi) therapy. The delivery of nucleic acid nanomedicines on biomaterial scaffolds - gene-activated scaffolds -has shown potential for use in a variety of tissue engineering applications, but as of yet, have not reached clinical use. The current state of the art in terms of biomaterial scaffolds and delivery vector materials for gene therapy is reviewed, and the limitations of current procedures discussed. Future directions in the clinical translation of gene-activated scaffolds are also considered, with a particular focus on bone and cartilage tissue regeneration.

miRNA profiling of high, low and non-producing CHO cells during biphasic fed-batch cultivation reveals process relevant targets for host cell engineering

Fed-batch cultivation of recombinant Chinese hamster ovary (CHO) cell lines is one of the most widely used production modes for commercial manufacturing of recombinant protein therapeutics. Furthermore, fed-batch cultivations are often conducted as biphasic processes where the culture temperature is decreased to maximize volumetric product yields. However, it remains to be elucidated which intracellular regulatory elements actually control the observed pro-productive phenotypes. Recently, several studies have revealed microRNAs (miRNAs) to be important molecular switches of cell phenotypes. In this study, we analyzed miRNA profiles of two different recombinant CHO cell lines (high and low producer), and compared them to a non-producing CHO DG44 host cell line during fed-batch cultivation at 37°C versus a temperature shift to 30°C. Taking advantage of next-generation sequencing combined with cluster, correlation and differential expression analyses, we could identify 89 different miRNAs, which were differentially expressed in the different cell lines and cultivation phases. Functional validation experiments using 19 validated target miRNAs confirmed that these miRNAs indeed induced changes in process relevant phenotypes. Furthermore, computational miRNA target prediction combined with functional clustering identified putative target genes and cellular pathways, which might be regulated by these miRNAs. This study systematically identified novel target miRNAs during different phases and conditions of a biphasic fed-batch production process and functionally evaluated their potential for host cell engineering.

A signature of 12 microRNAs is robustly associated with growth rate in a variety of CHO cell lines

As Chinese Hamster Ovary (CHO) cells are the cell line of choice for the production of human-like recombinant proteins, there is interest in genetic optimization of host cell lines to overcome certain limitations in their growth rate and protein secretion. At the same time, a detailed understanding of these processes could be used to advantage by identification of marker transcripts that characterize states of performance. In this context, microRNAs (miRNAs) that exhibit a robust correlation to the growth rate of CHO cells were determined by analyzing miRNA expression profiles in a comprehensive collection of 46 samples including CHO-K1, CHO-S and CHO-DUKXB11, which were adapted to various culture conditions, and analyzed in different growth stages using microarrays. By applying Spearman or Pearson correlation coefficient criteria of>|0.6|, miRNAs with high correlation to the overall growth, or growth rates observed in exponential, serum-free, and serum-free exponential phase were identified. An overlap of twelve miRNAs common for all sample sets was revealed, with nine positively and three negatively correlating miRNAs. The here identified panel of miRNAs can help to understand growth regulation in CHO cells and contains putative engineering targets as well as biomarkers for cell lines with advantageous growth characteristics.

Unveiling the principle of microRNA-mediated redundancy in cellular pathway regulation

Understanding the multifaceted nature of microRNA (miRNA) function in mammalian cells is still a challenge. Commonly accepted principles of cooperativity and multiplicity of miRNA function imply that individual mRNAs can be targeted by several miRNAs whereas a single miRNA may concomitantly regulate a subset of different genes. However, there is a paucity of information whether multiple miRNAs regulate critical cellular events and thereby acting redundantly. To gain insight into this notion, we conducted an unbiased high-content miRNA screen by individually introducing 1139 miRNA mimics into Chinese hamster ovary (CHO) cells. We discovered that 66% of all miRNAs significantly impacted on proliferation, protein expression, apoptosis and necrosis. In summary, we provide evidence for a substantial degree of redundancy among miRNAs to maintain cellular homeostasis.

Enhanced protein production by microRNA-30 family in CHO cells is mediated by the modulation of the ubiquitin pathway

Functional genomics represent a valuable approach to improve culture performance of Chinese hamster ovary (CHO) cell lines for biopharmaceutical manufacturing. Recent advances in applied microRNA (miRNAs) research suggest that these small non-coding RNAs are critical for the regulation of cell phenotypes in CHO cells. However, the notion that individual miRNAs usually control the expression of hundreds of different genes makes miRNA target identification highly complex. We have recently reported that the entire miR-30 family enhances recombinant protein production in CHO cells. To better understand the pro-productive effects of this miRNA family, we set out to identify their downstream target genes in CHO cells. Computational target prediction combined with a comprehensive functional validation enabled the discovery of a set of twenty putative target genes for all productivity enhancing miR-30 family members. We demonstrate that all miR-30 isoforms contribute to the regulation of the ubiquitin pathway in CHO cells by directly targeting the ubiquitin E3 ligase S-phase kinase-associated protein 2 (Skp2). Finally, we provide several lines of evidence that miR-30-mediated modulation of the ubiquitin pathway may enhance recombinant protein expression in CHO cells. In summary, this study supports the importance of non-coding RNAs, especially of miRNAs, in the context of cell line engineering.

Engineering the supply chain for protein production/secretion in yeasts and mammalian cells

Metabolic bottlenecks play an increasing role in yeasts and mammalian cells applied for high-performance production of proteins, particularly of pharmaceutical ones that require complex posttranslational modifications. We review the present status and developments focusing on the rational metabolic engineering of such cells to optimize the supply chain for building blocks and energy. Methods comprise selection of beneficial genetic modifications, rational design of media and feeding strategies. Design of better producer cells based on whole genome-wide metabolic network analysis becomes increasingly possible. High-resolution methods of metabolic flux analysis for the complex networks in these compartmented cells are increasingly available. We discuss phenomena that are common to both types of organisms but also those that are different with respect to the supply chain for the production and secretion of pharmaceutical proteins.

A novel collagen-nanohydroxyapatite microRNA-activated scaffold for tissue engineering applications capable of efficient delivery of both miR-mimics and antagomiRs to human mesenchymal stem cells

Manipulation of gene expression through the use of microRNAs (miRNAs) offers tremendous potential for the field of tissue engineering. However, the lack of sufficient site-specific and bioactive delivery systems has severely hampered the clinical translation of miRNA-based therapies. In this study, we developed a novel non-viral bioactive delivery platform for miRNA mimics and antagomiRs to allow for a vast range of therapeutic applications. By combining nanohydroxyapatite (nHA) particles with reporter miRNAs (nanomiRs) and collagen-nanohydroxyapatite scaffolds, this work introduces the first non-viral, non-lipid platform to date, capable of efficient delivery of mature miRNA molecules to human mesenchymal stem cells (hMSCs), a particularly difficult cell type to transfect effectively, with minimal treatment-associated cytotoxicity. Firstly, miRNAs were successfully delivered to hMSCs in monolayer, with internalisation efficiencies of 17.4 and 39.6% for nanomiR-mimics and nanoantagomiRs respectively, and both nanomiR-mimics and nanoantagomiRs yielded sustained interfering activity of greater than 90% in monolayer over 7 days. When applied to 3D scaffolds, significant RNA interference of 20% for nanomiR-mimics and 88.4% for nanoantagomiRs was achieved with no cytotoxicity issues over a 7 day period. In summary, in-house synthesised non-viral nHA particles efficiently delivered reporter miRNAs both in monolayer and on scaffolds demonstrating the immense potential of this innovative miRNA-activated scaffold system for tissue engineering applications.

Cholesterol-conjugated let-7a mimics: antitumor efficacy on hepatocellular carcinoma in vitro and in a preclinical orthotopic xenograft model of systemic therapy

Background

A major challenge to the clinical utility of let-7 for hepatocellular carcinoma (HCC) therapy is the lack of an effective carrier to target tumours. We confirmed the high transfection efficiency of cholesterol-conjugated let-7a miRNA mimics (Chol-let-7a) in human HCC cells, as well as their high affinity for liver tissue in nude mice. However, their antitumor efficacy via systemic delivery remains unknown.

Methods

We explored the effects of Chol-let-7a on HCC in vitro and in vivo. Cell viability and mobility, let-7a abundance and the target ras genes was measured. Live-cell image and cell ultrastructure was observed. Antitumor efficacy in vivo was analyzed by ultrasonography, hispatholgogy and transmission electronic microscopy in a preclinical model of HCC orthotopic xenografts with systemic therapy.

Results

Chol-let-7a inhibited the viability and mobility of HCC cells. Chol-let-7a was primarily observed in the cytoplasm and induced organelle changes, including autophagy. Mild changes were observed in the cells treated with negative control miRNA. Chol-let-7a reached HCC orthotopic tumours, significantly inhibited tumour growth, and prevented local invasion and metastasis. Compared to control tumours, Chol-let-7a-treated tumours showed more necrosis. Tumour cells showed no significant atypia, and mitoses were very rare after systemic Chol-let-7a therapy. Furthermore, let-7a abundance in orthotopic xenografts was coincident with a reduction in the expression of 3 human ras mRNAs and RAS proteins.

Conclusions

Chol-let-7a exerted significant antitumor effects by down-regulating all human ras genes at the transcriptional and translational levels. Chol-let-7a inhibited cell proliferation, growth, and metastasis, and mainly functioned in the cytoplasm. Chol-let-7a represents a potential useful modified molecule for systemic HCC therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-889) contains supplementary material, which is available to authorized users.

A functional high-content miRNA screen identifies miR-30 family to boost recombinant protein production in CHO cells

The steady improvement of mammalian cell factories for the production of biopharmaceuticals is a key challenge for the biotechnology community. Recently, small regulatory microRNAs (miRNAs) were identified as novel targets for optimizing Chinese hamster ovary (CHO) production cells as they do not add any translational burden to the cell while being capable of regulating entire physiological pathways. The aim of the present study was to elucidate miRNA function in a recombinant CHO-SEAP cell line by means of a genome-wide high-content miRNA screen. This screen revealed that out of the 1, 139 miRNAs examined, 21% of the miRNAs enhanced cell-specific SEAP productivity mainly resulting in elevated volumetric yields, while cell proliferation was accelerated by 5% of the miRNAs. Conversely, cell death was diminished by 13% (apoptosis) or 4% (necrosis) of all transfected miRNAs. Besides these large number of identified target miRNAs, the outcome of our studies suggest that the entire miR-30 family substantially improves bioprocess performance of CHO cells. Stable miR-30 over expressing cells outperformed parental cells by increasing SEAP productivity or maximum cell density of approximately twofold. Our results highlight the application of miRNAs as powerful tools for CHO cell engineering, identified the miR-30 family as a critical component of cell proliferation, and support the notion that miRNAs are powerful determinants of cell viability.

Establishment of lipofection for studying miRNA function in human adipocytes

miRNA dysregulation has recently been linked to human obesity and its related complications such as type 2 diabetes. In order to study miRNA function in human adipocytes, we aimed for the modulation of mature miRNA concentration in these cells. Adipocytes, however, tend to be resistant to transfection and there is often a need to resort to viral transduction or electroporation. Our objective therefore was to identify an efficient, non-viral transfection reagent capable of delivering small RNAs into these cells. To achieve this, we compared the efficiencies of three transfection agents, Lipofectamine 2000, ScreenFect A and BPEI 1.2 k in delivering fluorescent-labelled siRNA into human Simpson-Golabi-Behmel syndrome (SGBS) preadipocytes and adipocytes. Downregulation of a specific target gene in response to miRNA mimic overexpression was assayed in SGBS cells and also in ex vivo differentiated primary human adipocytes. Our results demonstrated that while all three transfection agents were able to internalize the oligos, only lipofection resulted in the efficient downregulation of a specific target gene both in SGBS cells and in primary human adipocytes. Lipofectamine 2000 outperformed ScreenFect A in preadipocytes, but in adipocytes the two reagents gave comparable results making ScreenFect A a notable new alternative for the gold standard Lipofectamine 2000.

Analysis of microRNA transcription and post-transcriptional processing by Dicer in the context of CHO cell proliferation

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The expression of Dicer is correlated to growth rate in different CHO cell lines.

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Global perturbation of microRNA levels via DICER knockdown or overexpression directly influences CHO growth behavior.

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This provides strong evidence that microRNAs are key growth regulators in CHO cell lines.

CHO cells are the mammalian cell line of choice for recombinant production of therapeutic proteins. However, their low rate of proliferation limits obtainable space-time yields due to inefficient biomass accumulation. We set out to correlate microRNA transcription to cell-specific growth-rate by microarray analysis of 5 CHO suspension cell lines with low to high specific growth rates. Global microRNA expression analysis and Pearson correlation studies showed that mature microRNA transcript levels are predominately up-regulated in a state of fast proliferation (46 positively correlated, 17 negatively correlated). To further validate this observation, the expression of three genes that are central to microRNA biogenesis (Dicer, Drosha and Dgcr8) was analyzed. The expression of Dicer, which mediates the final step in microRNA maturation, was found to be strongly correlated to growth rate. Accordingly, knockdown of Dicer impaired cell growth by reducing growth-correlating microRNA transcripts. Moderate ectopic overexpression of Dicer positively affected cell growth, while strong overexpression impaired growth, presumably due to the concomitant increase of microRNAs that inhibit cell growth. Our data therefore suggest that Dicer dependent microRNAs regulate CHO cell proliferation and that Dicer could serve as a potential surrogate marker for cellular proliferation.