Different Combinations Of Growth Factors Research Articles

The Sequential and Systemic Administration of BMP-2 and SDF-1α Nanocapsules for Promoting Osteoporotic Fracture Healing.

The objective of this study was to investigate the use of the nanocapsule sequential delivery of BMP-2 and SDF-1α through the peripheral circulatory system to promote the healing of osteoporotic fractures. Based on increased vascular permeability in the early hematoma environment around the fracture and the presence of a large number of matrix metalloproteinase MMPs in the inflammatory environment, we designed MMP-sensitive nanocapsules which were formed viain situ free-radical polymerization on the surface of grow factors with 2-(methacryloyloxy) ethyl phosphorylcholine (MPC) and the bisacryloylated VPLGVRTK peptide. The antiphagic effect and biological activity of the growth factors for the nanomicrocapsule delivery system were tested by cell experiments. The 36 SD rats with an osteoporotic fracture model were randomly divided into six groups (A, B, C, D, E, and F). In this paper, the nanocapsules loaded with BMP-2 and SDF-1 are represented as n (BMP-2) and n (SDF-1α). In the six groups, the following different combinations of growth factors were injected into the bone defect site on days 1 and 3 after bone defect surgery: in group A, n (SDF-1α) combined with n (SDF-1α); in group B, n (BMP-2) combined with n (BMP-2); in group C, n (SDF-1α) + n (BMP-2) combined with n (SDF-1α) + n (BMP-2); in group D, n (SDF-1α) combined with n (BMP-2); in group E, n (BMP-2) combined with n (SDF-1α); in group F, nanocapsules without growth factor were used as the control group. Micro-CT was used to observe the effect of n(BMP-2) and n(SDF-1α) sequential delivery inearly healing in osteoporotic fractures. Finally, in this study, we evaluated the safety of the nanocapsules delivery system by detecting ectopic osteogenesis and inflammatory responses in animals. Nanocapsules have low toxicity and protect the integrity and biological activity of growth factors. The results confirmed that nanocapsules could still be effectively targeted to the fracture site on days 1, 3, and 7 after intravenous administration. Growth factors encapsulated in nanocapsules have better bone repair results than natural growth factors. In particular, groups C and D had the best bone repair results than other groups.In vivo experiments confirmed that nanocapsules did not cause significant ectopic osteogenesis and inflammation. The results confirmed that the special vascular permeability and inflammatory factor microenvironment of the fracture site could be used to deliver two growth factors with a synergistic effect through venous circulation, which could better promote the healing process of osteoporotic fracture.

Improvement of in vitro proliferation of cockerel spermatogonial stem cells using different combinations of growth factors

ABSTRACT 1. This study examined whether in vitro proliferation and maintenance of cockerel spermatogonial stem cells (SSCs) could be improved by adding different combinations of growth factors (GFs), including glial cell line-derived neurotrophic factor (GDNF), basic fibroblast growth factor (bFGF) or leukaemia inhibitory factor (LIF) into the culture medium. 2. The SSCs were isolated from the testes of immature cockerels. For short-term cultures, a medium supplemented with different combinations of GFs for 7 d in 5 replicates was used. The groups were classified as follows: without GF (control group); with GDNF (G group); with GDNF and bFGF (GF group); and with GDNF, bFGF and LIF (GFL group). The number of colonies and cells per colony, as well as the transcript abundance of STRA8 and OCT4 genes, was determined 7 d after the initial culturing. Immunofluorescence staining of SSEA-1, SSEA-3 and VASA protein markers, besides periodic acid-Schiff (PAS) staining, was carried out. 3. The number of colonies and cells per colony increased in the G, GF and GFL groups, compared to the control group (P < 0.01); however, the highest proliferation and colony formation were observed in the GFL group. The positive immunofluorescence staining of SSEA-1, SSEA-3 and VASA protein markers, as well as PAS staining, confirmed the self-renewal and colonisation of cockerel SSCs. The proliferation results were supported by the increased STRA8 and OCT4 transcript abundance in the treated groups (G, GF and GLF), compared to the control group. The SSC proliferation was associated with the higher transcript abundance of STAR8 and OCT4 genes in the GFL group, compared to the G and GF groups (P < 0.01). 4. The results showed that proliferation and colony-forming capacity of cockerel SSCs were positively improved by GDNF, bFGF and LIF. However, the most significant effect was observed when the medium was supplemented with LIF in combination with GDNF and bFGF.

An optimized protocol for generating labeled and transplantable photoreceptor precursors from human embryonic stem cells

Cell replacement therapy is a promising approach for treatment of retinal degenerative diseases. Several protocols for the generation of photoreceptor precursors (PRP) from human embryonic stem cells (hESC) have been reported with variable efficiency. Herein, we show the advantages of use of size-controlled embryoid bodies in the ESC differentiation process using two differentiation protocols. We further explored cell-labeling methods for following the survival of PRP transplanted subretinally in rat eyes. Size-controlled embryoid bodies (EBs) generated using microwell dishes and non-size-controlled EBs generated using V-shaped 96-well plates were differentiated into PRP using two differentiation protocols. The differentiation protocols utilized two different combinations of growth factors. The first, Dkk1, Noggin, and IGF1, and the second protocol used IWR1e, SAG, and CHIR99021. Differentiation efficiency to PRP was analyzed by qPCR, immunocytochemistry, and fluorescence-assisted cell sorting (FACS). Size-controlled IWR1e yielded a significantly higher percent (86.4%) of PRP cells expressing CRX, compared with non-size-controlled IWR1e (51.4%, P = 0.026) or the size-controlled DKK1 protocol (70.5%, p = 0.007). In addition, the IWR1e differentiated cells exhibited a significantly higher fluorescence intensity of CRX immunostaining, compared with the DKK1 protocol, consistent with higher protein expression levels. The IWR1e cells exhibited higher maturation levels, as manifested by lower early neuronal marker PAX6 and pluripotency marker OCT4 levels compared with the DKK1 protocol. The expression of other late photoreceptor markers (NRL, recoverin) were similar among the differentiation groups.PRP cells were labeled by using hESC constitutively expressing EGFP or by AAV-GFP transduction. Finally, we transplanted the cells in the subretinal space of wild-type rats and monitored their survival over several weeks. The AAV2 serotype efficiently transduced the PRP cells, whereas other serotypes yielded low or no transduction. Following subretinal transplantation of GFP-labeled PRP, 63% of the cells were detected at 4 weeks post-transplantation. In conclusion, we show here that the IWR1e protocol using size-controlled EBs efficiently generated of PRP that could be labeled and followed in-vivo for weeks. The data from this study is an advance toward the goal of PRP transplantation therapy for retinal degenerative diseases.

Different combinations of growth factors for the tenogenic differentiation of bone marrow mesenchymal stem cells in monolayer culture and in fibrin-based three-dimensional constructs

Tendon injuries are severe burdens in clinics. The poor tendon healing is related to an ineffective response of resident cells and inadequate vascularization. Thanks to the high proliferation and multi-lineage differentiation capability, bone marrow-derived mesenchymal stem cells (BMSCs) are a promising cell source to support the tendon repair. To date, the association of various growth factors to induce the in vitro tenogenic differentiation of multipotent progenitor cells is poorly investigated. This study aimed to investigate the tenogenic differentiation of rabbit BMSCs by testing the combination of bone morphogenetic proteins (BMP-12 and 14) with transforming growth factor beta (TGF-β) and vascular endothelial growth factor (VEGF) both in 2D and 3D cultures within fibrin-based constructs. After 7 and 14 days, the tenogenic differentiation was assessed by analyzing cell metabolism and collagen content, the gene expression of tenogenic markers and the histological cell distribution and collagen deposition within 3D constructs.Our results demonstrated that the association of BMP-14 with TGF-β3 and VEGF enhanced the BMSC tenogenic differentiation both in 2D and 3D cultures. This study supports the use of fibrin as hydrogel-based matrix to generate spheroids loaded with tenogenic differentiated BMSCs that could be used to treat tendon lesions in the future.

Dissociation of Survival, Proliferation, and State Control in Human Hematopoietic Stem Cells.

SummaryThe role of growth factors (GFs) in controlling the biology of human hematopoietic stem cells (HSCs) remains limited by a lack of information concerning the individual and combined effects of GFs directly on the survival, Mitogenesis, and regenerative activity of highly purified human HSCs. We show that the initial input HSC activity of such a purified starting population of human cord blood cells can be fully maintained over a 21-day period in serum-free medium containing five GFs alone. HSC survival was partially supported by any one of these GFs, but none were essential, and different combinations of GFs variably stimulated HSC proliferation. However, serial transplantability was not detectably compromised by many conditions that reduced human HSC proliferation and/or survival. These results demonstrate the dissociated control of these three human HSC bio-responses, and set the stage for future improvements in strategies to modify and expand human HSCs ex vivo.

Development of a two-step protocol for culture expansion of human annulus fibrosus cells with TGF-β1 and FGF-2.

BackgroundDifferent biologic approaches to treat disc regeneration, including growth factors (GFs) application, are currently under investigation. Human annulus fibrosus (hAF) repair or regeneration is one of the key elements for maintenance and restoration of nucleus pulposus function. However, so far there is no effective treatment for this purpose. The aim of the present study was to investigate the response of hAF cells to different combinations of GFs, and develop a protocol for efficient culture expansion.MethodshAF cells were harvested from degenerated disc tissues during surgical intervertebral disc removal, and hAF cells were expanded in a monolayer. The experiments were categorized based on different protocols with transforming growth factor (TGF-β1) and fibroblast growth factor (FGF-2) culture for 14 days: group 1 had no GFs (control group); group 2 received TGF-β1; group 3 received FGF-2; group 4 received both GFs; and group 5 (two-step) received both GFs for the first 10 days and TGF-β1 only for the next 4 days. Cell proliferation, collagen, and noncollagen extracellular matrix (ECM) production and genes expression were compared among these groups.ResultsAt days 3, 7 and 10 of cultivation, groups 4 and 5 had significantly more cell numbers and faster cell proliferation rates than groups 1, 2, and 3. At 14 days of cultivation, significantly more cell numbers were observed in groups 3 and 4 than in group 5. The group 4 had the most cell numbers and the fastest proliferation rate at 14 days of cultivation. After normalization for cell numbers, group 5 (two-step) produced the most collagen and noncollagen ECM at 10 and 14 days of cultivation among the five groups. In group 5, ECM gene expression was significantly upregulated. High expression of matrix metalloproteinase-1 was upregulated with FGF-2 on the different days as compared to the other groups. Annulus fibrosus cell phenotypes were only marginally retained under the different protocols based on quantitative polymerase chain reaction results.ConclusionTaken together, the two-step protocol was the most efficient among these different protocols with the most abundant ECM production after normalization for cell numbers for culture expansion of hAF cells. The protocol may be useful in further cell therapy and tissue engineering approaches for disc regeneration.

Modified protocol for improvement of differentiation potential of menstrual blood-derived stem cells into adipogenic lineage.

To characterize potency of menstrual blood-derived stem cells (MenSCs) for future cell therapies, we examined differentiation potential of MenSCs into adipocytes. Differentiation potential of MenSCs in comparison to bone marrow stem cells (BMSCs) was assessed in conventional culture medium. Differentiation potential of MenSCs into adipocytes was improved using different combinations of growth factors and hormones. First, we demonstrated that MenSCs preserve their appearance and karyotypic stability during passages. Although these cells express mesenchymal stem cells markers, they cannot simply be classified as mesenchymal stem cells due to expression of embryonic stem cells marker, OCT-4. Oil red O staining showed that differentiated MenSCs in conventional medium with/without retinoic acid (protocols 1 and 2) did not attain adipocyte characteristics, whereas differentiated BMSCs in conventional medium accumulated oil vacuoles typically. Nevertheless, real-time RT-PCR results showed that LPL gene expression was up-regulated in both protocols 1 and 2, whereas LEPR was up-regulated only in protocol 2 (fortified with retinoic acid). Surprisingly, protocol 3 (including rosiglitazone) had odd influence on mRNA expression of all genes (LEPR, LPL and PPAR-γ). Oil red O staining confirmed fat-producing ability of MenSCs under protocol 3. Presented data suggest an efficient differentiation protocol for in vitro production of MenSC-derived adipocytes. These cells are suggested to be an apt alternative to BMSCs for future stem cell therapy of soft tissue injuries.

IGF-1 enhances cell proliferation and survival during early differentiation of mesenchymal stem cells to neural progenitor-like cells.

BackgroundThere has been increasing interest recently in the plasticity of mesenchymal stem cells (MSCs) and their potential to differentiate into neural lineages. To unravel the roles and effects of different growth factors in the differentiation of MSCs into neural lineages, we have differentiated MSCs into neural lineages using different combinations of growth factors. Based on previous studies of the roles of insulin-like growth factor 1 (IGF-1) in neural stem cell isolation in the laboratory, we hypothesized that IGF-1 can enhance proliferation and reduce apoptosis in neural progenitor-like cells (NPCs) during differentiation of MSCs into NCPs.We induced MSCs differentiation under four different combinations of growth factors: (A) EGF + bFGF, (B) EGF + bFGF + IGF-1, (C) EGF + bFGF + LIF, (D) EGF + bFGF + BDNF, and (E) without growth factors, as a negative control. The neurospheres formed were characterized by immunofluorescence staining against nestin, and the expression was measured by flow cytometry. Cell proliferation and apoptosis were also studied by MTS and Annexin V assay, respectively, at three different time intervals (24 hr, 3 days, and 5 days). The neurospheres formed in the four groups were then terminally differentiated into neuron and glial cells.ResultsThe four derived NPCs showed a significantly higher expression of nestin than was shown by the negative control. Among the groups treated with growth factors, NPCs treated with IGF-1 showed the highest expression of nestin. Furthermore, NPCs derived using IGF-1 exhibited the highest cell proliferation and cell survival among the treated groups. The NPCs derived from IGF-1 treatment also resulted in a better yield after the terminal differentiation into neurons and glial cells than that of the other treated groups.ConclusionsOur results suggested that IGF-1 has a crucial role in the differentiation of MSCs into neuronal lineage by enhancing the proliferation and reducing the apoptosis in the NPCs. This information will be beneficial in the long run for improving both cell-based and cell-free therapy for neurodegenerative diseases.

Mobilization of bone marrow mesenchymal stem cells in vivo augments bone healing in a mouse model of segmental bone defect

Although the number of mesenchymal stem cells (MSC) in the bone marrow is sufficient to maintain skeletal homeostasis, in osteopenic pathology, aggravated osteoclast activity or insufficient osteoblast numbers ensue, affecting normal bone remodeling. Most of the currently available therapies are anti-resorptive with limited osteogenic potential. Since mobilization of stem/progenitors from the BM is a prerequisite for their participation in tissue repair, amplification of endogenous stem cells may provide an alternative approach in these conditions. The present study determined the potential of MSC mobilization in vivo, using combinations of different growth factors with the CXCR4 antagonist, AMD3100, in a mouse model of segmental bone defect. Results indicated that among several factors tested IGF1 had maximum proliferative ability of MSC in vitro. Results of the in vivo studies indicated that the combination of IGF1 and AMD3100 provided significant augmentation of bone growth as determined by DXA, micro-CT and histomorphometry in mice bearing segmental fractures. Further, characterization of MSC isolated from mice treated with IGF1 and AMD3100 indicated Akt/PI3K, MEK1/2-Erk1/2 and smad2/3 as key signaling pathways mediating this effect. These data indicate the potential of in vivo stem cell mobilization as a novel alternative for bone healing.

Synergistic effects of growth factors and mesenchymal stromal cells for expansion of hematopoietic stem and progenitor cells

The number of hematopoietic stem and progenitor cells (HPCs) per cord blood unit is limited, and this can result in delayed engraftment or graft failure. In vitro expansion of HPCs provides a perspective to overcome these limitations. Cytokines as well as mesenchymal stromal cells (MSCs) have been shown to support HPCs ex vivo expansion, but a systematic analysis of their interplay remains elusive. Twenty different combinations of growth factors (stem cell factor [SCF], thrombopoietin [TPO], fibroblast growth factor-1 [FGF-1], angiopoietin-like 5, and insulin-like growth factor-binding protein 2), either with or without MSC coculture were systematically compared for their ability to support HPC expansion. CD34(+) cells were stained with carboxyfluorescein diacetate N-succinimidyl ester to monitor cell division history in conjunction with immunophenotype. Colony-forming unit frequencies and hematopoietic reconstitution of nonobese diabetic severe combined immunodeficient mice were also assessed. Proliferation of HPCs was stimulated by coculture with MSCs. This was further enhanced in combination with SCF, TPO, and FGF-1. Moreover, these conditions maintained expression of primitive surface markers for more than four cell divisions. Colony-forming unit-initiating cells were not expanded without stromal support, whereas an eightfold increase was reached by simultaneous cytokine-treatment and MSC coculture. Importantly, in comparison to expansion without stromal support, coculture with MSCs significantly enhanced hematopoietic chimerism in a murine transplantation model. The supportive effect of MSCs on hematopoiesis can be significantly increased by addition of specific recombinant growth factors; especially in combination with SCF, TPO, and FGF-1.

Mechanism of action of somatic stem cell treatments: towards the concept of therapeutic plasticity

The initial perception that transplantation of stem cells could serve only to replace damaged cells has continued to be modifi ed as evidence for a protective multifaceted function of transplanted cells has emerged. Neural stem/precursor cells (NPC) were the fi rst to be shown to use this strategy to protect the central nervous system (CNS) from infl ammatory insults (1 – 5). Subsequently similar functions by other types of somatic stem cells (e.g. mesenchymal stromal cells; MSC) have been described (6). Currently the ability of transplanted stem cells to protect tissues from diverse injury using multifaceted ‘ bystander strategies ’ has been substantiated in several experiments. Somatic stem cells promote CNS repair following intralesional as well as systemic injection by producing in situ a milieu of protective molecules whose release is regulated, both temporally and spatially, by environmental demands. The milieu contains immunomodulatory substances, trophic growth factors, stem cell regulators, angiogenic factors, scavengers, etc.: all molecules constitutively expressed by somatic stem cells for maintaining tissue homeostasis during development and in adult life. The concept of ‘ therapeutic platicity ’ that is now emerging (7) also reconciles data showing that stem cells other than NPC, although endowed with negligible transdifferentiation capability, may have a benefi cial role in CNS repair. In four articles of this issue of Cytotherapy the concept of therapeutic plasticity of somatic stem cells is presented further. Although these reports do not completely clarify the mechanisms underlying this therapeutic plasticity, they demonstrate that transplantation of various somatic stem cells via different routes ameliorates diverse neurologic diseases without an overt terminal differentiation and functional integration of the transplanted cells. Alexanian et al. (8) observe that delayed intralesional transplantation of human glial-restricted NPC in rats affected by thoracic spinal cord injury ameliorates sensorimotor defi cits. He et al. (9) report that bone marrow (BM)-derived MSC and endothelial progenitor cells transplanted intravenously (i.v.) protect rats from focal ischemia via the secretion of different combinations of growth factors. Interestingly, an additive benefi cial effect was observed when the two different cell sources were co-transplanted. Li et al. (10) focus on a mouse model of muscular dystrophy where mean survival as well as loss of dystrophin and utrophin expression is delayed by i.v. transplantation of rat-derived MSC. Attar et al. (11) describe preliminary results of intralesional transplantation of BM-derived hematopoietic stem cells along with BM-derived mononuclear cells in four patients with spinal cord injury. Although the possibility of using bystander strategies as protection from tissue injury appears to be a very promising therapeutic use of somatic stem cells, we still need to resolve unsolved key questions before clinical translation. One crucial question is whether to transplant the cells heterotopically or homotopically. Transplantation is not without risks: co-transplantation of NPC and pancreatic islet cells under the kidney capsule of diabetic mice induced the generation, at the site of cell transplantation, of insulin-induced neuroblastoma-like neoplasms (12). Intracardiac transplantation of stem cell factor-overexpressing MSC into mice with myocardial infarction promoted the formation of a chest wall-invading soft tissue sarcoma (13). The unregulated transplantation Cytotherapy, 2011; 13: 6–7

Directed Differentiation of Human Embryonic Stem Cells as Spin Embryoid Bodies and a Description of the Hematopoietic Blast Colony Forming Assay

This unit describes a protocol for the differentiation of human embryonic stem cells (hESCs). To generate spin embryoid bodies (EBs), known numbers of hESCs are deposited into low-attachment, round-bottomed 96-well plates in a serum-free medium supplemented with growth factors. The cells are then aggregated by centrifugation, initiating formation of EBs of uniform size. The spin EBs generated using this technique differentiate efficiently and synchronously along the lineages preferentially induced by the combinations of growth factors to which the cells are exposed. The 96-well format permits an assessment of the effects of different combinations of growth factors in the same experiment, facilitating the optimization of differentiation conditions for any given cell type. Up to 40 plates can be set up within a couple of hours by one experimenter, and aliquots of the differentiating EBs can be harvested at intervals and subjected to analyses using a variety of techniques.

Improving In Vitro Generated Cartilage-Carrier-Constructs by Optimizing Growth Factor Combination

The presented study is focused on the generation of osteochondral implants for cartilage repair, which consist of bone substitutes covered with in vitro engineered cartilage. Re-differentiation of expanded porcine cells was performed in alginate gel followed by cartilage formation in high-density cell cultures. In this work, different combinations of growth factors for the stimulation of re-differentiation and cartilage formation have been tested to improve the quality of osteochondral implants. It has been demonstrated that supplementation of the medium with growth factors has significant effects on the properties of the matrix. The addition of the growth factors IGF-I (100 ng/mL) and TGF-β1 (10 ng/mL) during the alginate culture and the absence of any growth factors during the high-density cell culture led to significantly higher GAG to DNA ratios and Young’s Moduli of the constructs compared to other combinations. The histological sections showed homogenous tissue and intensive staining for collagen type II.

Mobilised Peripheral Blood Could Be a Suitable Source of Mesenchymal Stem Cells?.

Mesenchymal stem cells (MSC) are multipotent cells that are considered one of the most promising product for cellular therapy in regenerative medicine. MSC have been obtained and expanded from bone marrow and umbilical cord blood in adequate amounts for clinical applications. Under the right conditions, MSC could migrate from bone marrow into the peripheral circulation; however MSC have not been routinely isolated from peripheral blood, and studies are rare and not conclusive. The aim of the present study was to evaluate mobilised peripheral blood (MPB), obtained from patients undergoing apheresis collection of circulating hematopoietic progenitor cells, as a potential source of MSC for clinical applications. MPB samples (500–900 × 106 cells, N = 17) were separated by negative lineage-depletion immunoselection (RosetteSep). Selected cells were seeded in multi-well plates at low density in MesenCult Basal Medium without and with different combinations of growth factors (EGF, PDGF-BB, b-FGF). On reaching confluence, adherent cells were detached by 0.25% trypsin-EDTA treatment and replated for at least two passages. At each passage, surface antigen expression was analyzed by flowcytometry (CD45, CD34, CD105, CD44, CD73, CD166, CD31, HLA-DR and VE-caderine). Following immunoselection 9.5–17.1 × 106 cells were recovered from MPB samples. Cultured cells reached confluency in 3–4 weeks on first passage and in two weeks thereafter. Immunophenotyping showed negativity for CD45 antigen. The absence of growth factors in culture medium conditioned MSC growth capability, while the addition of PDGF-BB+EGF or b-FGF was able to boost the number of CD45−/CD73+/CD90+ cells in culture (see figure). However expansion remains still sub-optimal, having been reached in 8/17 samples. In conclusion, we demonstrate that MSC can be obtained from MPB, but expansion requires longer time period and appears more difficult compared to bone marrow. Therefore, further studies need to be conducted to find better culture conditions and optimal growth factor combinations to support MPB-derived MSC expansion. [Display omitted]

Advances in the management of leg ulcers--the potential role of growth factors.

Venous ulcers are a major health problem because of the increased costs of the treatment and the refractory nature of the ulcers. The treatment cost is estimated to be around 1 billion dollars per year in the United States (US), and the average cost for one patient over a lifetime exceeds dollars 400,000. There has been an increasing trend in the use of growth factors in their management. Genetic engineering has revolutionised the research of wound healing, as the majority of recombinant growth factors are now available for in vitro and in vivo studies. Online searches of Medline, Pub Medical and Embase were carried out using the terms venous ulcers, leg ulcers, growth factors and growth hormone. The literature regarding the potential role of growth factors in the management of leg ulcers is reviewed. The important clinical studies are critically analysed with a view to appreciate the emerging therapies and the further research possibilities in the management of venous leg ulcers. Clinical results with the use of growth factors in non-healing wounds are encouraging. However, small sample sizes and inconsistent end points in different clinical studies have been the main hurdle in reaching a definite conclusion. Further research is needed to provide the definite evidence. Future developments may include different delivery methods for the growth factors, use of different combinations of growth factors administered simultaneously or, sequentially, bioengineered skin grafts and chemical induction of angiogenesis with the use of gene transfer techniques.

IN VITRO PROLIFERATION OF SWINE HEPATOCYTES WITHOUT EXOGENOUS MATRICES EFFECTS OF THE COMPOSWON OF THE CULTURE MEDIUM

Hepatocyte transplantation requires a population of mature and proliferating cells for long time. The aim of this work was to study the proliferative capacity of hepatocytes that were grown in vitro with different media, without exogenous matrices. Methods: E Williams was used as basal medium. It was supplemented with ECF, hydrocortisone, transferrin, BPE, insulin, and 1% FBS: complete medium. The following conditions were compared: 1) complete medium without only one factor from those mentioned above, and 2) basal medium plus only one factor. Proliferation was determined by [3H]-tymidine incorporation activity at days 2, 4, 6, 10, 15, 20, and 30. Results: Cells grown in complete media showed two peaks of thymidine incorporation: the first one (higher) at day 2, and the second one (lower) at day 10. The absence of insulin, transferrin, or ECF, produced a lower incorporation than basal medium, from day 6, but it was higher in the absence of hydrocortisone. Basal media plus ECF and complete medium gave a comparable proliferative response. However, most of the cells were lost after 15 days of culture Conclusion: In the absence of exogenous matrices, swine hepatocytes cultured in vitro are able to proliferate for at least 15 days. Furthermore, this capacity cm be modulated using different combinations of growth factors, being this a new point of view in tissue engineering.

Adult neural stem cells: plasticity and developmental potential

Stem cells play an essential role during the processes of embryonic tissue formation and development and in the maintenance of tissue integrity and renewal throughout adulthood. The differentiation potential of stem cells in adult tissues has been thought to be limited to cell lineages present in the organ from which they derive, but there is evidence that somatic stem cells may display a broader differentiation repertoire. This has been documented for bone marrow stem cells (which can give rise to muscle, hepatic and brain cells) and for muscle precursors, which can turn into blood cells. The adult central nervous system (CNS) has long been considered incapable of cell renewal and structural remodeling. Recent findings indicate that, even in postnatal and adult mammals, neurogenesis does occur in different brain regions and that these regions actually contain adult stem cells. These cells can be expanded both in vivo and ex vivo by exposure to different combinations of growth factors and subsequently give rise to a differentiated progeny comprising the major cell types of the CNS. Almost paradoxically, adult neural stem cells display a multipotency much broader than expected, since they can differentiate into non-CNS mesodermal-derivatives, such as blood cells and skeletal muscle cells. We review the recent findings documenting this unforeseen plasticity and unexpected developmental potential of somatic stem cells in general and of neural stem cells in particular. To better introduce these concepts, some basic notions on the functional properties of adult neural stem cells will also be discussed, particularly focusing on the emerging role of the microenvironment in determining and maintaining their peculiar characteristics.

Hämatopoetische Wachstumsfaktoren in der Prophylaxe und Therapie infektiöser Komplikationen bei Kindern mit Neutropenie

Hematopoietic colony-stimulating factors have been introduced into clinical practice as additional supportive measures to reduce infectious complications associated with congenital or acquired neutropenia. Over the past decade, we have begun to appreciate the subtler aspects of the proper use of G-CSF and GM-CSF, identifying appropriate indications and contraindications. In the course of evaluating the corpus of studies, a set of formal recommendations have been propagated for the judicious use of these expensive growth factors. To prevent serious infection, the use of G-CSF or GM-CSF is recommended in a subset of pediatric cancer patients shortly after having received chemotherapy or a form of a marrow transplant. Children with highly intensive chemotherapy (e.g., children with high risk ALL or NHL) seem to benefit from hematopoietic growth factors whereas this is still unclear for children undergoing therapy for solid tumors. An exciting development is the use of G-CSF and GM-CSF to mobilize peripheral-blood progenitor cells for autologous or allogeneic transplantation. In pediatric patients with hematological diseases, there are only few data on the use of hematopoietic growth factors in children with myelodysplastic syndrome. Experts recommend the early administration of G-CSF in children with very severe aplastic anemia. The use of G-CSF is also recommended in children with severe chronic neutropenia, but these patients have to be monitored regularly for cytogenetic abnormalities. No larger study has shown a clinical benefit of hematopoietic growth factor in preterm or term infants. Future studies in pediatric patients are clearly warranted to address several issues. Prospective clinical trials are still needed to define specific treatment groups who can benefit from growth factor support. In this regard, efforts must be directed at better defining the endpoints and in particular assigning value to reduction in treatment of possible infectious complications, such as days in hospital, antibiotic usage and costs. In addition, randomized studies are required to evaluate the proper dosage and duration of therapy, which most likely will vary between groups of patients. In addition, combinations of different growth factors have to be tested, particularly if ex vivo expansion and the storage of hematopoietic stem cells are to be utilized in a wider spectrum of patients.

Animal Serum-Free Culture of Purified Human CD34+ Cells: Amplification of Progenitors from G-CSF and GM-CSF-Mobilized Peripheral Blood

The isolation and culture of human CD34+ cells could have broad clinical application for hematologic support following high-dose chemotherapy or bone marrow transplantation. The need for reproducible, animal product-free conditions for the culture of progenitors is crucial to the widespread clinical implementation of ex vivo cell therapies. In these studies, we explored the use of animal serum-free (ASF) medium for the culture of isolated human bone marrow and peripheral blood CD34+ cells. In this ASF system, isolated CD34+ cells were cultured using a variety of different growth factor combinations. Such ASF culture conditions yielded equivalent to superior cell and progenitor growth when directly compared with culture containing 10% fetal calf serum (FCS). In cultures containing IL-1, IL-3, and stem cell factor, total cell numbers increased, on average, 33-fold over the first 2 weeks. On phenotypic analysis, the ASF cultures demonstrated sustained proliferation of CD33+ myeloid cells throughout the culture period. CD34+ cell numbers increased during the first 7-10 days of culture, with a mean 3.4-fold expansion. Concomitant with the CD34+ cell expansion was an average 8.2-fold expansion of colony-forming unit-granulocyte-macrophage (CFU-GM) and a 102.0-fold increase in burst-forming units-erythrocytes (BFU-E). Likewise, a mean 4929-fold expansion of CD41a+ megakaryocyte progenitors was observed in these CD34+ cultures. Different combinations of growth factors affected the fold increase in cell and progenitor number. When CD34+ cell cultures from normal healthy volunteers mobilized with either G-CSF or GM-CSF were compared, similar expansions of total cell and progenitor cells resulted. However, CD41+ cells expansions were greater in those samples from G-CSF-mobilized volunteers in every case tested. These studies established the feasibility of this ASF CD34+ cell culture system to generate a population of maturing progenitors for potential use in transfusion support during cytopenic periods following high-dose chemotherapy or bone marrow transplantation.

Mutual Inhibition of Murine Erythropoiesis and Granulopoiesis During Combined Erythropoietin, Granulocyte Colony-Stimulating Factor, and Stem Cell Factor Administration: In Vivo Interactions and Dose-Response Surfaces

We investigated the in vivo effects of erythropoietin (EPO) on granulopoiesis and, conversely, the effect of granulocyte colony-stimulating factor (G-CSF) treatment on erythropoiesis. Recombinant human EPO at four different doses in combination with recombinant human G-CSF also at four different doses was simultaneously administered for 7 days to splenectomized mice. In total, 16 different combinations of growth factors were thus tested. G-CSF administration increased granulocyte production as expected, whereas immature colony-forming unit granulocyte-macrophage numbers were decreased. EPO analogously increased late erythroid cell numbers. Both EPO and G-CSF dose-dependently inhibited late cell stages of the opposite lineage, with EPO abrogating G-CSF-stimulated granulopoiesis and, conversely, G-CSF inhibiting EPO-stimulated erythropoiesis. In a subsequent experiment, we tested whether these lineage-competitive effects could be prevented by coadministering stem cell factor (SCF). In these three factor-treated mice, all granuloid and erythroid cell stages increased, thereby reducing the effect of the mutual inhibition. We conclude that EPO-stimulated erythropoiesis and G-CSF-stimulated granulopoiesis inhibited each other at a late level. Simultaneous SCF administration increased the input into both the erythroid and granuloid compartment and thereby compensated the mutual inhibition. This study shows that intricate dose-response relationships exist between various growth factors that should be carefully analyzed before combinations of these factors are used in humans.