Presence Of Appropriate Growth Factors Research Articles

3D Printing & Pharmaceutical Manufacturing: Opportunities and Challenges

Many researchers have attempted to use computer-aided design (C.A.D) and computer-aided manufacturing (CAM) to realize a scaffold that provides a three-dimensional (3D) environment for regeneration of tissues and organs. As a result, several 3D printing technologies, including stereolithography, deposition modeling, inkjet-based printing and selective laser sintering have been developed. Because these 3D printing technologies use computers for design and fabrication, and they can fabricate 3D scaffolds as designed; as a consequence, they can be standardized. Growth of target tissues and organs requires the presence of appropriate growth factors, so fabrication of 3Dscaffold systems that release these biomolecules has been explored. A drug delivery system (D.D.S) that administrates a pharmaceutical compound to achieve a therapeutic effect in cells, animals and humans is a key technology that delivers biomolecules without side effects caused by excessive doses. 3D printing technologies and D. D. Ss have been assembled successfully, so new possibilities for improved tissue regeneration have been suggested. If the interaction between cells and scaffold system with biomolecules can be understood and controlled, and if an optimal 3D tissue regenerating environment is realized, 3D printing technologies will become an important aspect of tissue engineering research in the near future. 3D Printing promises to produce complex biomedical devices according to computer design using patient-specific anatomical data. Since its initial use as pre-surgical visualization models and tooling molds, 3D Printing has slowly evolved to create one-of-a-kind devices, implants, scaffolds for tissue engineering, diagnostic platforms, and drug delivery systems. Fuelled by the recent explosion in public interest and access to affordable printers, there is renewed interest to combine stem cells with custom 3D scaffolds for personalized regenerative medicine. Before 3D Printing can be used routinely for the regeneration of complex tissues (e.g. bone, cartilage, muscles, vessels, nerves in the craniomaxillofacial complex), and complex organs with intricate 3D microarchitecture (e.g. liver, lymphoid organs), several technological limitations must be addressed. Until recently, tablet designs had been restricted to the relatively small number of shapes that are easily achievable using traditional manufacturing methods. As 3D printing capabilities develop further, safety and regulatory concerns are addressed and the cost of the technology falls, contract manufacturers and pharmaceutical companies that experiment with these 3D printing innovations are likely to gain a competitive edge. This review compose the basics, types & techniques used, advantages and disadvantages of 3D printing

3D Printing technology over a drug delivery for tissue engineering.

Many researchers have attempted to use computer-aided design (CAD) and computer-aided manufacturing (CAM) to realize a scaffold that provides a three-dimensional (3D) environment for regeneration of tissues and organs. As a result, several 3D printing technologies, including stereolithography, deposition modeling, inkjet-based printing and selective laser sintering have been developed. Because these 3D printing technologies use computers for design and fabrication, and they can fabricate 3D scaffolds as designed; as a consequence, they can be standardized. Growth of target tissues and organs requires the presence of appropriate growth factors, so fabrication of 3Dscaffold systems that release these biomolecules has been explored. A drug delivery system (DDS) that administrates a pharmaceutical compound to achieve a therapeutic effect in cells, animals and humans is a key technology that delivers biomolecules without side effects caused by excessive doses. 3D printing technologies and DDSs have been assembled successfully, so new possibilities for improved tissue regeneration have been suggested. If the interaction between cells and scaffold system with biomolecules can be understood and controlled, and if an optimal 3D tissue regenerating environment is realized, 3D printing technologies will become an important aspect of tissue engineering research in the near future.

Novel cell lines isolated from mouse embryonic stem cells exhibiting de novo methylation of the E-cadherin promoter.

Mouse embryonic stem cells (mESCs) and epiblast stem cells represent the naïve and primed pluripotent states, respectively. These cells self-renew via distinct signaling pathways and can transition between the two states in the presence of appropriate growth factors. Manipulation of signaling pathways has therefore allowed the isolation of novel pluripotent cell types such as Fibroblast growth factor, Activin and BIO-derived stem cells and IESCs. However, the effect of cell seeding density on pluripotency remains unexplored. In this study, we have examined whether mESCs can epigenetically regulate E-cadherin to enter a primed-like state in response to low cell seeding density. We show that low density seeding in the absence of leukaemia inhibitory factor (LIF) induces decreased apoptosis and maintenance of pluripotency via Activin/Nodal, concomitant with loss of E-cadherin, Signal transducer and activator of transcription phosphorylation, and chimera-forming ability. These cells, E-cadherin negative proliferating stem cells (ENPSCs) can be reverted to a naïve phenotype by addition of LIF or forced E-cadherin expression. However, prolonged culture of ENPSCs without LIF leads to methylation of the E-cadherin promoter (ENPSC(M)), which cannot be reversed by LIF supplementation, and increased histone H3K27 and decreased H3K4 trimethylation. Transcript analysis of ENPSC(M) revealed a primed-like phenotype and their differentiation leads to enrichment of neuroectoderm cells. The generation of ENPSCs is similar to tumorigenesis as ENPSCs exhibit transcript alterations associated with neoplasia, hyperplasia, carcinoma, and metastasis. We therefore describe a novel cell model to elucidate the role of E-cadherin in pluripotency and to investigate epigenetic regulation of this gene during mESC differentiation and tumor metastasis.

Derivation of Hematopoietic Progenitor Cells From Vector-Free Human Induced Pluripotent Stem Cells

Abstract 4746Induced pluripotent stem cells (iPSCs), due to their self-renewal and differentiation capability, have tremendous potential in regenerative medicine. Differentiation of IPSCs in vitro to obtain sufficient number of hematopoietic stem cells (HSCs) and their progenitors (HPCs) from iPSCs for therapeutic purposes is a holy grail of cellular therapy. To this end, we are comparing different in vitro differentiation approaches for generation of HSCs/HPCs from IPSCs.We have generated iPSCs from human adult dermal fibroblasts using two different reprogramming methods: 1) Transduction with retroviral vectors encoding human Klf4, Oct3/4, Sox2 and cMyc or 2) Electroporation with Epstein–Barr virus (EBV) based episomal plasmid vectors encoding Klf4, Oct3/4, Sox2, L-Myc and p53 targeting shRNA. The transduced/electroporated cells were reprogrammed on SNL5 mouse feeder cells. Putative iPSC-like colonies were cloned and adapted to grow under feeder-free conditions on Matrigel (BD) in mTeSR1 (Stem Cell Technologies) medium. From over 30 individual clones isolated, six were further characterized for: 1) expression of pluripotency markers (Tra-1–60, SSEA-3, SSEA-4, Nanog and Oct3/4) by immunofluorescence; 2) endogenous and total mRNA expression by quantitative real-time reverse-transcriptase PCR (RT-qPCR) for Klf4, Oct3/4, Sox2 and cMyc to distinguish between cellular and vector derived expression of reprogramming factors; 3) RT-qPCR to determine expression of other markers of pluripotency such as Nanog and DNA methyl transferease; 4) karyotype analysis to determine chromosomal anomalies. The vector-free IPSC clones were also tested for residual integrated EBV plasmid DNA by qPCR. Trilineage differentiation ability of the clones was determined through embryoid body formation in suspension cultures, and subsequent staining of resulting embryoid bodies after adherence to gelatin coated dishes for makers of ectoderm, mesoderm and endoderm.HSCs/HPCs were obtained from IPSCs by 1) coculture with OP9 stromal cells, or 2) step-wise differentiation in feeder-free conditions on Matrigel under defined conditions in the presence of appropriate growth factors [Niwa A et al. PLoS One. (2011); 6(7):e22261.]. The resultant HSCs/HPCs were subjected to colony forming assays in semi-solid medium containing hematopoietic cytokines. Both erythroid and myelomonocytic colonies could be readily identified. The influence of ambient oxygen concentration on the HSC/HPC derivation procedure is being investigated. The results of these studies will be presented. Disclosures:No relevant conflicts of interest to declare.

Megakaryocyte Production From Feeder Cell-Free Cultures of Human Embryonic Stem Cells (hESC).

Abstract 2528Poster Board II-505 Introduction:As the understanding of hESC biology and technology improves, one long-term goal is to utilize expanded numbers of undifferentiated hESC to produce clinically relevant numbers of blood cells in vitro to reduce the need for donors for red blood cell and platelet transfusions. At one end of the production system is the need to create systems for efficient culture of very large numbers of hESC. Methods have been developed using various cytokine combinations to expand end-stage hematopoietic cells from CD34+ cells from bone marrow, peripheral blood, or umbilical cord blood, although little work has been done on megakaryocytopoiesis. Previous systems for bridging the differentiation gap from undifferentiated hESC to mesoderm to hematopoietic progenitor cells have required xenogeneic or in some cases allogeneic supportive cells ± serum at various stages of culture. We have developed a culture system that utilizes feeder cell-free matrix for undifferentiated hESC growth, followed by embryoid body formation, with subsequent shedding of individual hematopoietic progenitor cells that expand and mature to platelet-shedding megakaryocytes. Methods:After extensive evaluations of culture conditions, we arrived at the following optimized conditions. Culture dishes coated with extracellular matrix residual of chemically-digested human foreskin fibroblasts (HFF1 cells from ATCC) support expansion of undifferentiated hESC for more than 30 passages in the presence of DMEM/F12 medium with serum replacement and basic fibroblast growth factor (bFGF). Clusters of cells (∼2 × 105 cells per 2 ml in 6 well plates) from these hESC cultures were transferred to ultra-low attachment culture dishes to form embryoid bodies (EB) in Stemline II medium with (1) basic fibroblast growth factor (bFGF) + vascular endothelial growth factor (VEGF) + bone morphogenic protein (BMP)4 for 2 days; (2) then Stemline II medium with VEGF + BMP4 + thrombopoietin (TPO) + stem cell factor (SCF) + flt3 ligand (FL) for 2 days; (3) then a defined medium with VEGF + BMP4 + TPO + SCF + FL + interleukin (IL)3 + IL6 + IL11 + granulocyte-macrophage colony-stimulating factor (GM-CSF) for 10 days; (4) then cells were transferred to single cell suspension in defined medium with GM-CSF + SCF + FL + TPO + IL6 + Heparin for up to 3 additional weeks. Markers of all stages of differentiation from hESC through megakaryocytes were analyzed by immunofluorescence throughout the course of the cultures. Results:Expression of hESC markers Oct4 and Sox2 was decreased by EB day 7 and was undetectable by EB day 10, although SSEA4 expression persisted until EB day 14. The early mesoderm markers brachyury and Mixl1 were barely detectable until EB day 14. Somewhat surprisingly, hemangioblast/hematopoietic progenitor markers, CD34, GATA1, and CD31, were readily detectable in nearly 100% of cells several days earlier than brachyury and Mixl1, by EB day 7. By EB day 14, there was approximately a 10-fold expansion of cell numbers from the beginning of the EB cultures, with large numbers of single almost exclusively mononuclear cells routinely being found in suspension outside of the EBs. Virtually 100% of these cells were strongly CD34+/GATA1+, a majority were brachyury+ and Mixl1+, and the majority of free floating cells, but not cells within the day 14 EBs were mildly positive for the megakaryocytic lineage markers CD41, CD42a, and CD42b, with 5–10% of these cells outside of the EBs being very strongly positive for these megakaryocytic lineage markers. Differentiation toward megakaryocytes progressed from 7 to 14 days after the EB day 14 suspension cells were transferred to new feeder-free, non-adherent culture dishes. Nearly 100% of cells still were CD34+/GATA1+ (decreased intensity compared to EB Day 14), and >80% of cells became CD41+/CD42a+/CD42b+/CD61+/vWF+/PF4+, and many were shedding platelet-like particles by 14 days after transfer from EB cultures. Conclusions:We have developed a multi-stage culture system that, in the presence of appropriate growth factors, supports specific differentiation from hESC to EB to mature megakaryocytes, avoiding any need for xenogeneic or allogeneic feeder cells or serum. Disclosures:No relevant conflicts of interest to declare.

Lentiviral transduction of Tar Decoy and CCR5 ribozyme into CD34+ progenitor cells and derivation of HIV-1 resistant T cells and macrophages

BackgroundRNA based antiviral approaches against HIV-1 are among the most promising for long-term gene therapy. These include ribozymes, aptamers (decoys), and small interfering RNAs (siRNAs). Lentiviral vectors are ideal for transduction of such inhibitory RNAs into hematopoietic stem cells due to their ability to transduce non-dividing cells and their relative refractiveness to gene silencing. The objective of this study is to introduce an HIV-1 Tar aptamer either alone or in combination with an anti-CCR5 ribozyme into CD34+ hematopoietic progenitor cells via an HIV-based lentiviral vector to derive viral resistant progeny T cells and macrophages.ResultsHigh efficiency and sustained gene transfer into CD34+ cells were achieved with lentiviral vector constructs harboring either Tar decoy or Tar decoy in combination with CCR5 ribozyme. Cells transduced with these constructs differentiated normally into T-lymphocytes in vivo in thy/liv grafts of SCID-hu mice, and into macrophages in vitro in the presence of appropriate growth factors. When challenged in vitro, the differentiated T lymphocytes and macrophages showed marked resistance against HIV-1 infection.ConclusionsViral resistant transgenic T cells and macrophages that express HIV-1 Tar aptamer either alone or in combination with an anti-CCR5 ribozyme could be obtained by lentiviral gene transduction of CD34+ progenitor cells. These results showed for the first time that expression of these anti-HIV-1 transgenes in combination do not interfere with normal thymopoiesis and thus have set the stage for their application in stem cell based gene therapy for HIV/AIDS.

Genetic modification of stem cells to enhance bone repair.

Orthopaedic surgeons are often faced with difficult bone loss problems. Conventional bone grafting is usually accomplished with autogenous iliac crest bone graft that provides osteogenic cells, osteoinductive growth factors, and an osteoconductive matrix. Cadaveric bone allograft and bone graft substitutes are inferior to autogenous bone graft because they fail to supply osteogenic cells or a significant amount of osteoinductive growth factors. Recombinant growth factors such as bone morphogenetic protein-2 and osteogenic protein-1 are currently in clinical use but these proteins require supraphysiologic dosing and considerable expense while failing to provide a sustained osteoinductive signal at the implantation site. Mesenchymal stem cells capable of differentiating into mesodermal tissues have been isolated and expanded in culture from several different sources including bone marrow, adipose tissue, and muscle. In the presence of appropriate growth factors these cells can differentiate into osteoblast lineage cells that will form bone in vitro and in vivo. Recent attention has focused on genetic modification of mesenchymal stem cells to both produce and respond to osteogenic growth factors with the goal of developing a tissue engineering strategy for bone repair. This review examines the current potential and limitations of these cellular systems for bone repair.

Inhibition of myeloid cell differentiation in cancer: the role of reactive oxygen species.

It is well established that tumor growth is associated with accumulation of immature myeloid cells (ImC). They play an important role in tumor-associated immune suppression. ImC accumulate not only in tumor-bearing hosts but also in immunized, tumor-free hosts or hosts infected with bacterial pathogens. The kinetics of ImC in these mice is different. If in tumor-bearing mice, the number of ImC continues to increase with tumor progression in tumor-free mice after an initial spike, it decreases to the control level. Here, we have investigated the mechanisms of ImC accumulation in tumor-bearing hosts by comparing differentiation of ImC obtained from tumor-free and tumor-bearing mice. In the presence of appropriate growth factors, ImC isolated from tumor-free mice quickly differentiated in vitro into mature dendritic cells (DC), macrophages, and granulocytes. In contrast, differentiation of ImC from tumor-bearing mice was significantly delayed. Similar results were obtained in vivo after adoptive transfer of ImC into naïve, congeneic mice. ImC transferred into tumor-bearing recipients failed to differentiate into DC or macrophages. ImC from tumor-bearing mice had significantly higher levels of reactive oxygen species (ROS) than ImC obtained from tumor-free mice. Hydrogen peroxide (H(2)O(2)) but not superoxide radical anions was found to be the major part of this increased ROS production. In vitro experiments demonstrated that scavenging of H(2)O(2) with catalase induced differentiation of ImC from tumor-bearing mice into macrophages. Thus, this is a first demonstration that tumors may prevent differentiation of antigen-presenting cells by increasing the level of endogenous H(2)O(2) in immature myeloid cells.

O6-Benzylguanine potentiates BCNU but not busulfan toxicity in hematopoietic stem cells.

Busulfan (BU) is often used in conditioning regimens prior to bone marrow transplantation, but its mechanism of action remains to be resolved. We have examined the possibility that BU may exert part of its toxic effects via DNA alkylation at the O6 position of guanine as this might provide an approach to improving the conditioning regimen. Survival of LAMA-84 and RJKO cells was assessed by colony-forming assay and cell counting, respectively. O6-alkylguanine-DNA alkyltransferase (ATase) activity was assayed by transfer of radioactivity from [3H]-methylated DNA. Colony-forming potential of normal human bone marrow cells (BMC) was measured in the presence of appropriate growth factors as the formation of both granulocyte-macrophage colony-forming units (CFU-GM) or burst-forming unit erythroids (BFU-E) within the same assay. Murine hematopoietic precursors were grown under a bone marrow stromal cell line to allow measurement of the frequency of cobblestone area-forming cells (CAFC) that correspond to CFU-GM, spleen colony-forming units (CFU-S), and the primitive stem cells with long-term repopulating ability. Inactivation of ATase by O6-benzylguanine (O6-BeG) sensitized a human erythromegakaryocytic cell line (LAMA-84) and normal human bone marrow progenitors to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) but not to BU toxicity. BCNU, but not BU, inactivated ATase in LAMA-84 cells. Overexpression of human ATase in cDNA transfected Chinese hamster cells attenuated the toxicity of BCNU but not BU. Finally, the in vivo treatment of mice showed that the depletion of primitive stem cells by BU as measured in the CAFC assay was not affected by addition of O6-BeG. O6-BeG did, however, dramatically potentiate BCNU toxicity in all CAFC subsets, leading to depletion of more than 99% stem cells. These data suggest that BU does not elicit toxicity via alkylation at the O6 position of guanine in DNA in a way that can be influenced by ATase modulation.

Cortical lesions induce an increase in cell number and PSA-NCAM expression in the subventricular zone of adult rats.

The subventricular zone (SVZ) bordering the lateral ventricle is one of the few regions of adult brain that contains dividing cells. These cells can differentiate into neurons in vivo after migration into the olfactory bulb and in vitro in the presence of appropriate growth factors. Little is known, however, about the fate of these cells in vivo after brain injury in adults. We examined cell number and expression of differentiation markers in the SVZ of adult rats after cortical lesions. Aspiration lesions of the sensorimotor cortex in adult rats induced a transient doubling of the number of cells in the SVZ at the level of the striatum without consistent increases in bromodeoxyuridine-labeled cells. Immunoreactivity to the polysialylated neural cell adhesion molecule, expressed by the majority of cells of the SVZ during development, increased dramatically after lesion. In contrast, immunolabeling for molecules found in mature neurons and glia did not increase in the SVZ after lesion, and immunoreactivity for growth factors that induce differentiation of SVZ cells in vitro decreased or remained undetectable, suggesting that lack of appropriate growth factor expression may contribute to the lack of differentiation of the newly accumulated cells in vivo. The data reveal that cells of the SVZ are capable of plasticity in the adult rat after brain injury in vivo and that the newly accumulated cells retain characteristics seen during development.

Human cerebral cortical cell lines from patients with unilateral megalencephaly and Rasmussen's encephalitis

Continuous cerebral cortical cell lines have been developed from two patients, an 11-month-old with unilateral megalencephaly and a seven-year-old with Rasmussen's encephalitis, designated HCN-1 and HCN-2, respectively. The two cell lines stain for neuronal markers such as neurofilament and neuron-specific enolase but not for non-neuronal markers such as glial fibrillary acidic protein and S-100 protein. In the presence of appropriate growth factors, the cells extend long, branched processes resembling neurons. Differentiation of HCN-1 cells can be induced with nerve growth factor, dibutyryl cyclic AMP and isobutylmethylxanthine, while for HCN-2 cells nerve growth factor, isobutylmethylxanthine and the phorbol ester12- O-tetradecaoylphorbol-13-acetate are most effective. Immunohistochemical staining of both differentiated cell lines reveals intense staining for GABA, glutamate, somatostatin, cholecystokinin-8 and methionine enkephalin. Two human cortical neuronal cell lines have been developed which represent neuronal precursors. These cell lines propagate in culture and are capable of differentiating upon the addition of a variety of growth factors and chemical agents. These cell lines should prove to be useful models for the study of in vitro neuronal processes.

T cell differentiation in the thymus

T lymphocytes arise in the thymus and seed to peripheral lymphoid organs as fully functional cells at the time of exit. In humans, the thymus begins to function very early in ontogeny and releases large numbers of T cells before the time of birth. However, the vast majority of developing thymocytes (>95%) die within the thymus as a result of stringent selection processes. Positive selection imposes self-MHC-restriction on thymocytes and dictates the MHC-restricted repertoire of post-thymic T cells. Negative selection results in deletion of autoreactive cells. Both types of selection depend on cell to cell contracts and on the presence of appropriate growth factors which are still largely undetermined. Cell to cell contacts occur between developing thymocytes and cells of the thymic microenvironment (accessory cells), and are mediated by several receptor/ligand interactions which subserve the function of establishing and stabilizing these contacts. Besides MHC-TCR interactions, adhesion molecules are important for thymocyte maturation, selection and activation, and for the export and peripheral homing of mature T cells produced in the thymus. Here we describe a novel integrin involved in thymocyte-thymic epithelial cell interactions.

Isolation of ts mutant cells which arrest in G1/G0 phase at the non-permissive temperature in the presence of appropriate growth factors from a Fischer rat cell line, 3Y1

Two types of cell-cycle- ts mutants were isolated from Fischer rat cell line, 3Y1, and characterized. Clones in one complementation group, tsJT51 and tsJT341, grew at 34 °C in the presence of 10% fetal bovine serum (FBS). When the cells growing at 34 °C were transferred to 39.5 °C, they were arrested alive in G1/G0 phase in the presence of both FBS and epidermal growth factor (EGF), but died in the presence of one of these growth factors. The cells in the other complementation group, tsJT59, tsJT308, tsJT314 and tsJT439, grew at 34 °C in the presence of 10% FBS. When the cells growing at 34 °C were transferred to 39.5 °C, they were arrested alive in G1/G0 phase in the simultaneous presence of FBS, EGF and insulin, but died quickly if one of these growth factors was lacking. Growth-arrested cells at 39.5 °C were viable at least one or two weeks and had a potency to resume growth following the shift-down of temperature. Those are assumed to be ts mutant cells which enter and stay in G1/G0 phase from the cell cycle at the non-permissive temperature only in the presence of appropriate growth factors.