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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

The nucleus is the target for radiation-induced chromosomal instability

We have previously described chromosomal instability in cells of a human-hamster hybrid cell line after exposure to X rays. Chromosomal instability in these cells is characterized by the appearance of novel chromosomal rearrangements multiple generations after exposure to ionizing radiation. To identify the cellular target(s) for radiation-induced chromosomal instability, cells were treated with 125I-labeled compounds and frozen. Radioactive decays from 125I cause damage to the cell primarily at the site of their decay, and freezing the cells allows damage to accumulate in the absence of other cellular processes. We found that the decay of 125I-iododeoxyuridine, which is incorporated into the DNA, caused chromosomal instability. While cell killing and first-division chromosomal rearrangements increased with increasing numbers of 125I decays, the frequency of chromosomal instability was independent of dose. Chromosomal instability could also be induced from incorporation of 125I-iododeoxyuridine without freezing the cells for accumulation of decays. This indicates that DNA double-strand breaks in frozen cells resulting from 125I decays failed to lead to instability. Incorporation of an 125I-labeled protein (125I-succinyl-concanavalin A), which was internalized into the cell and/or bound to the plasma membrane, neither caused chromosomal instability nor potentiated chromosomal instability induced by 125I-iododeoxyuridine. These results show that the target for radiation-induced chromosomal instability in these cells is the nucleus.

Non-NASA Center↗
NASA NTRS1989

Gravity and animal embryos

Out of more than 4,500 rat hours in space there was only one experimental attempt (Cosmos 1129) at mating with an apparent absence of fertilization, implantation and subsequent development to term and partuition. Portions of this process were successfully flown, however, including the major portion of organogenesis in the rat (Cosmos 1524). These observations show that the cellular and molecular events underlying morphogenesis and differentiation in a small mammal can proceed normally in-utero under microgravity and other conditions encountered during short-duration flight. However, it is not known whether this situation will hold for larger mammals over several generations during extended missions that venture outside of near Earth. Furthermore, it is not understood why the previous attempt at obtaining copulation, fertilization and implantation in orbit failed but may be related to limitations of the rat habitat for meeting the preconditions for reproductive behavior. With respect to mammalian development it is important to appreciate that fertilization and development occur internally within the female and take a long time to complete and their success will, therefore, be contingent upon the maternal response to the space environment. One process central to development (the establishment of cell lines) is initiated prior to implantation by environmental asymmetries preceived by progenitor cells. These asymmetries appear to result from the formation of asymmetric cell-cell contacts and the concommitant development of an electrical axis across the progenitor cells. Other asymmetries were also documented. It is not known whether any of the known asymmetries perceived by progenitor cells are influenced by gravity vectors and/or by the maternal response to microgravity and other conditions encountered in space.

Wiley, Lynn M.↗
NASA NTRS2007

Chromosome Aberrations in Normal and Ataxia-Telangiectasia Cells Exposed to Heavy Ions

Although cells derived from Ataxia Telangiectasia (AT) patients are known to exhibit abnormal responses to ionizing radiations, its underlying mechanism still remains unclear. Previously, the authors reported that at the same gamma-irradiation dose AT cells show higher frequencies of misrepair and deletions compared to normal human fibroblast cells. In this study, we investigated the effects of heavy ions beams on chromosomal aberrations in normal and AT cells. Normal and AT fibroblast cells arrested at G0/G1 phase were irradiated with 2 Gy of X-rays, 490 MeV/u Silicon (LET 55 keV/m), 500 MeV/u Iron (LET 185 keV/m) and 200 MeV/u Iron (LET 440 keV/m) particles, and then cells were allowed to repair for 24 hours at 37 degrees before subculture. Calyculin-A induced PCC method was employed to collect G2/M chromosomes and whole DNA probes 1 and 3 were used to analyze chromosomal aberrations such as color-junctions, deletions, simple exchanges (incomplete and reciprocal exanges) and complex-type exchanges. The percentages of aberrant cells were higher when normal and AT cells were exposed to heavy ions compared to X-rays, and had a tendency to increase with increasing LET up to 185 keV/m and then decreased at 440 keV/m. When the frequency of color-junctions per cell was compared after X-ray exposure, AT cells had around three times higher frequency of color-junctions (mis-rejoining) than normal cells. However, at 185 keV/m there was no difference in the frequency of color-junctions between two cell lines. It was also found that the frequency of simple exchanges per cell was almost constant in AT cells regardless LET levels, but it was LET dependent for normal cells. Interestingly, the frequency of simple exchanges was higher for AT cells when it was compared at 185 keV/m but AT cells had more complex-type exchanges at the same LET levels. Heavy ions are more efficient in inducing chromosome aberrations in normal and AT cells compared to X-rays, and the aberration types between normal and AT fibroblast appeared different probably due to difference in the ATM gene function.

Kawata, T.↗
NASA NTRS2011

The Distribution of Chromosomal Aberrations in Human Cells Predicted by a Generalized Time-Dependent Model of Radiation-Induced Formation of Aberrations

New experimental data show how chromosomal aberrations for low- and high-LET radiation are dependent on DSB repair deficiencies in wild-type, AT and NBS cells. We simulated the development of chromosomal aberrations in these cells lines in a stochastic track-structure-dependent model, in which different cells have different kinetics of DSB repair. We updated a previously formulated model of chromosomal aberrations, which was based on a stochastic Monte Carlo approach, to consider the time-dependence of DSB rejoining. The previous version of the model had an assumption that all DSBs would rejoin, and therefore we called it a time-independent model. The chromosomal-aberrations model takes into account the DNA and track structure for low- and high-LET radiations, and provides an explanation and prediction of the statistics of rare and more complex aberrations. We compared the program-simulated kinetics of DSB rejoining to the experimentally-derived bimodal exponential curves of the DSB kinetics. We scored the formation of translocations, dicentrics, acentric and centric rings, deletions, and inversions. The fraction of DSBs participating in aberrations was studied in relation to the rejoining time. Comparisons of simulated dose dependence for simple aberrations to the experimental dose-dependence for HF19, AT and NBS cells will be made.

Ponomarev, Artem L.↗
NASA NTRS1993

Measuring the metastatic potential of cancer cells

Cancer cells must secrete proteolytic enzymes to invade adjacent tissues and migrate to a new metastatic site. Urokinase (uPA) is a key enzyme related to metastasis in cancers of the lung, colon, gastric, uterine, breast, brain, and malignant melanoma. A NASA technology utilization project has combined fluorescence microscopy, image analysis, and flow cytometry, using fluorescent dyes, and urokinase-specific antibodies to measure uPA and abnormal DNA levels (related to cancer cell proliferation) inside the cancer cells. The project is focused on developing quantitative measurements to determine if a patient's tumor cells are actively metastasizing. If a significant number of tumor cells contain large amounts of uPA (esp. membrane-bound) then the post-surgical chemotherapy or radiotherapy can be targeted for metastatic cells that have already left the primary tumor. These analytical methods have been applied to a retrospective study of biopsy tissues from 150 node negative, stage 1 breast cancer patients. Cytopathology and image analysis has shown that uPA is present in high levels in many breast cancer cells, but not found in normal breast. Significant amounts of uPA also have been measured in glioma cell lines cultured from brain tumors. Commercial applications include new diagnostic tests for metastatic cells, in different cancers, which are being developed with a company that provides a medical testing service using flow cytometry for DNA analysis and hormone receptors on tumor cells from patient biopsies. This research also may provide the basis for developing a new 'magic bullet' treatment against metastasis using chemotherapeutic drugs or radioisotopes attached to urokinase-specific monoclonal antibodies that will only bind to metastatic cells.

Morrison, Dennis R.↗
NASA NTRS2000

Enhanced expression of extracellular calcium sensing receptor in monocyte-differentiated versus undifferentiated HL-60 cells: potential role in regulation of a nonselective cation channel

Human promyelocytic leukemia cells (HL-60) have been used widely as a model for studying the differentiation of hematopoietic progenitor cells in vitro. After treatment with phorbol-12-myristate-13-acetate (PMA) or 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], HL-60 cells differentiate into cells with the phenotype of monocytes/macrophages. We previously showed that peripheral blood monocytes and the murine J774 monocytic cell line express the CaR, and myeloid progenitors in the bone marrow and myeloid cells in peripheral blood other than monocytes express lower levels of the CaR. Therefore, we investigated whether undifferentiated HL-60 cells express a functional G protein-coupled, extracellular calcium (Ca(2+)(o))-sensing receptor (CaR) and if the expression of the CaR increases as these cells differentiate along the monocytic lineage. The use of reverse transcription-polymerase chain reaction (RT-PCR) with CaR-specific primers, followed by sequencing of the amplified products, identified an authentic CaR transcript in undifferentiated HL-60 cells. Both immunocytochemistry and Western blot analysis using a CaR-specific antiserum detected low levels of CaR protein expression in undifferentiated HL-60 cells. The levels of CaR protein increased considerably following treatment of the cells with PMA (50 nM) or 1,25(OH)(2)D(3) (100 nM) for 5 days. Northern analysis using a CaR-specific riboprobe identified CaR transcripts in undifferentiated HL-60 cells, but CaR mRNA levels did not change appreciably after treatment with either agent, suggesting that upregulation of CaR protein occurs at a translational level. PMA-treated HL-60 cells expressed a nonselective cation channel (NCC), and the calcimimetic CaR activator, NPS R-467, but not its less active stereoisomer, NPS S-467, as well as the polycationic CaR agonist, neomycin, activated this NCC, demonstrating that the CaR expressed in these cells is functionally active. Therefore, HL-60 cells exhibit an increase in CaR protein expression, occurring at a translational level during their differentiation into cells with a monocyte/macrophage phenotype in response to treatment with PMA or 1, 25(OH)(2)D(3), which is functionally linked to activation of a nonselective cation channel.

NASA Discipline Musculoskeletal↗
NASA NTRS1997

Endothelial Cell Morphology and Migration are Altered by Changes in Gravitational Fields

Endothelial cell migration is important to vascular wall regeneration following injury or stress. However, the mechanism(s) governing this response is not well understood. The microgravity environment of space may complicate the response of these cells to injury. To date, there are no reports in this area. We examined how bovine aortic (BAEC) and pulmonary (BPEC) endothelial cells respond to denudation injury under hypergravity (HGrav) and simulated microgravity (MGrav), using image analysis. In 10% FBS, the migration of confluent BAEC and BPEC into the denuded area was not affected by HGrav or MGrav. However, in low FBS (0.5%), signficantly retarded migration under MGrav, and increased migration under HGrav was found. MGrav also decreased the migration of postconfluent BPEC while HGrav showed no difference. Both MGrav and HGrav strongly decreased the migration of postconfluent BAEC. Also, both cell lines showed significant morphological changes by scanning electron microscopy. These studies indicate that endothelial cell function is affected by changes in gravity.

Melhado, Caroline↗
NASA NTRS1991

Effects of murine leukemia virus env gene proteins on macrophage-mediated cytotoxicity in vitro

F5b Tumor cells were incubated with concentrated culture supernatants taken from cells resistant (F5m) or sensitive (F5b) to contact-dependent macrophage cytotoxicity. Macrophage cell line B6MP102 and murine peritoneal macrophages killed targets incubated with supernatants taken from sensitive cells but poorly killed cells incubated in supernatants isolated from resistant cells. Membranes from cells resistant to macrophage killing, F5m, were fused into F5b cells. The fused F5b cells were killed significantly less than F5b cells fused with F5b cell membranes or untreated F5b cells. The decreased killing of F5b cells corresponded to increased concentrations of gp70(a) molecules on F5b cells. Affinity purified gp70(a) was added to cytotoxicity assays but failed to inhibit macrophage cytotoxicity. P15E molecules were detectable on both F5b and F5m cells. In addition, a synthetic peptide found to exhibit the inhibitory properties of p15E was added to cytotoxicity assays. P15E synthetic peptide also did not inhibit macrophage cytotoxicity. Therefore, env gene proteins of murine leukemia virus do not appear responsible for inducing tumor cell resistance to activated macrophage contact-dependent cytotoxicity.

NASA Program NSCORT↗
NASA NTRS2009

Analysis of Chromosomal Aberrations after Low and High Dose Rate Gamma Irradiation in ATM or NBS Suppressed Human Fibroblast Cells

A detailed understanding of the biological effects of heavy nuclei is needed for space radiation protection and for cancer therapy. High-LET radiation produces more complex DNA lesions that may be non-repairable or that may require additional processing steps compared to endogenous DSBs, increasing the possibility of misrepair. Interplay between radiation sensitivity, dose, and radiation quality has not been studied extensively. Previously we studied chromosome aberrations induced by low- and high- LET radiation in several cell lines deficient in ATM (ataxia telangactasia mutated; product of the gene that is mutated in ataxia telangiectasia patients) or NBS (nibrin; product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase (DNA-PK) activity. We found that the yields of both simple and complex chromosomal aberrations were significantly increased in the DSB repair defective cells compared to normal cells. The increased aberrations observed for the ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex aberrations, while the linear dose-response term was significantly higher in NBS cells only for simple exchanges. These results point to the importance of the functions of ATM and NBS in chromatin modifications that function to facilitate correct DSB repair and minimize aberration formation. To further understand the sensitivity differences that were observed in ATM and NBS deficient cells, in this study, chromosomal aberration analysis was performed in normal lung fibroblast cells treated with KU-55933, a specific ATM kinase inhibitor, or Mirin, an MRN complex inhibitor involved in activation of ATM. We are also testing siRNA knockdown of these proteins. Normal and ATM or NBS suppressed cells were irradiated with gamma-rays and chromosomes were collected with a premature chromosome condensation (PCC) technique at the first mitosis post-irradiation. Chromosomes were analyzed using a multicolor fluorescence in-situ hybridization (mFISH) chromosome painting method. Preliminary analysis showed that chromosomal exchanges were increased in the cells treated with the specific ATM inhibitor. Possible cytogenetic signatures of acute and low dose-rate gamma irradiation in ATM or Nibrin deficient and suppressed cells will be discussed.

Hada, M.↗
NASA NTRS1997

Csa-19, a radiation-responsive human gene, identified by an unbiased two-gel cDNA library screening method in human cancer cells

A novel polymerase chain reaction (PCR)-based method was used to identify candidate genes whose expression is altered in cancer cells by ionizing radiation. Transcriptional induction of randomly selected genes in control versus irradiated human HL60 cells was compared. Among several complementary DNA (cDNA) clones recovered by this approach, one cDNA clone (CL68-5) was downregulated in X-irradiated HL60 cells but unaffected by 12-O-tetradecanoyl phorbol-13-acetate, forskolin, or cyclosporin-A. DNA sequencing of the CL68-5 cDNA revealed 100% nucleotide sequence homology to the reported human Csa-19 gene. Northern blot analysis of RNA from control and irradiated cells revealed the expression of a single 0.7-kilobase (kb) messenger RNA (mRNA) transcript. This 0.7-kb Csa-19 mRNA transcript was also expressed in a variety of human adult and corresponding fetal normal tissues. Moreover, when the effect of X- or fission neutron-irradiation on Csa-19 mRNA was compared in cultured human cells differing in p53 gene status (p53-/- versus p53+/+), downregulation of Csa-19 by X-rays or fission neutrons was similar in p53-wild type and p53-null cell lines. Our results provide the first known example of a radiation-responsive gene in human cancer cells whose expression is not associated with p53, adenylate cyclase or protein kinase C.

NASA Discipline Radiation Health↗
NASA NTRS2016

Translational Cellular Research on the International Space Station

The emerging field of Translational Research aims to coalesce interdisciplinary findings from basic science for biomedical applications. To complement spaceflight research using human subjects, translational studies can be designed to address aspects of space-related human health risks and help develop countermeasures to prevent or mitigate them, with therapeutical benefits for analogous conditions experienced on Earth. Translational research with cells and model organisms is being conducted onboard the International Space Station (ISS) in connection with various human systems impacted by spaceflight, such as the cardiovascular, musculoskeletal, and immune systems. Examples of recent cell-based translational investigations on the ISS include the following. The JAXA investigation Cell Mechanosensing seeks to identify gravity sensors in skeletal muscle cells to develop muscle atrophy countermeasures by analyzing tension fluctuations in the plasma membrane, which changes the expression of key proteins and genes. Earth applications of this study include therapeutic approaches for some forms of muscular dystrophy, which appear to parallel aspects of muscle wasting in space. Spheroids is an ESA investigation examining the system of endothelial cells lining the inner surface of all blood vessels in terms of vessel formation, cellular proliferation, and programmed cell death, because injury to the endothelium has been implicated as underpinning various cardiovascular and musculoskeletal problems arising during spaceflight. Since endothelial cells are involved in the functional integrity of the vascular wall, this research has applications to Earth diseases such as atherosclerosis, diabetes, and hypertension. The goal of the T-Cell Activation in Aging NASA investigation is to understand human immune system depression in microgravity by identifying gene expression patterns of candidate molecular regulators, which will provide further insight into factors that may play a critical role in immune function loss during aging. In addition, Omics investigations with cells have synergistic applications ranging from the evaluation of pharmacological countermeasures to drug discovery. Thus, cell-based translational research onboard the ISS is bidirectionally bridging cutting-edge cellular and molecular approaches with space bioastronautics and human health methodologies on Earth.

Love, John↗
NASA NTRS2003

Are chromosomal instabilities induced by exposure of cultured normal human cells to low- or high-LET radiation?

Radiation-induced genomic instability has been proposed as a very early, if not an initiating, step in radiation carcinogenesis. Numerous studies have established the occurrence of radiation-induced chromosomal instability in various cells of both human and rodent origin. In many of these studies, however, the cells were not "normal" initially, and in many cases they involved tumor-derived cell lines. The phenomenon clearly would be of even greater interest if it were shown to occur generally in cells that are normal at the outset, rather than cells that may have been "selected" because of a pre-existing susceptibility to induced instability. As a test of the generality of the phenomenon, we studied low-passage normal diploid human fibroblasts (AG1521A) to determine whether they are susceptible to the induction of chromosomal instability in the progeny of surviving cells after exposure in G(0) to low- and high-LET radiation. Cytogenetic assays for instability were performed on both mixed populations of cells and clones of cells surviving exposure. We found no evidence for the induction of such instability as a result of radiation exposure, though we observed a senescence-related chromosomal instability in the progeny of both irradiated and unirradiated cell populations. Copyright 2003 by Radiation Research Society.

Non-NASA Center↗
NASA NTRS2003

Three-Dimensional Engineered High Fidelity Normal Human Lung Tissue-Like Assemblies (TLA) as Targets for Human Respiratory Virus Infections

Unlike traditional two-dimensional (2D) cell cultures, three-dimensional (3D) tissue-like assemblies (TLA) (Goodwin et aI, 1992, 1993, 2000 and Nickerson et aI. , 2001,2002) offer high organ fidelity with the potential to emulate the infective dynamics of viruses and bacteria in vivo. Thus, utilizing NASA micro gravity Rotating Wall Vessel (RWV) technology, in vitro human broncho-epithelial (HBE) TLAs were engineered to mimic in vivo tissue for study of human respiratory viruses. These 3D HBE TLAs were propagated from a human broncho-tracheal cell line with a mesenchymal component (HBTC) as the foundation matrix and either an adult human broncho-epithelial cell (BEAS-2B) or human neonatal epithelial cell (16HBE140-) as the overlying element. Resulting TLAs share several characteristic features with in vivo human respiratory epithelium including tight junctions, desmosomes and cilia (SEM, TEM). The presence of epithelium and specific lung epithelium markers furthers the contention that these HBE cells differentiate into TLAs paralleling in vivo tissues. A time course of infection of these 3D HBE TLAs with human respiratory syncytial virus (hRSV) wild type A2 strain, indicates that virus replication and virus budding are supported and manifested by increasing virus titer and detection of membrane-bound F and G glycoproteins. Infected 3D HBE TLAs remain intact for up to 12 days compared to infected 2D cultures that are destroyed in 2-3 days. Infected cells show an increased vacuolation and cellular destruction (by transmission electron microscopy) by day 9; whereas, uninfected cells remain robust and morphologically intact. Therefore, the 3D HBE TLAs mimic aspects of human respiratory epithelium providing a unique opportunity to analyze, for the first time, simulated in vivo viral infection independent of host immune response.

Goodwin, T. J.↗
NASA NTRS1992

Chromosomal changes in cultured human epithelial cells transformed by low- and high-LET radiation

For a better assessment of radiation risk in space, an understanding of the responses of human cells, especially the epithelial cells, to low- and high-LET radiation is essential. In our laboratory, we have successfully developed techniques to study the neoplastic transformation of two human epithelial cell systems by ionizing radiation. These cell systems are human mammary epithelial cells (H184B5) and human epidermal keratinocytes (HEK). Both cell lines are immortal, anchorage dependent for growth, and nontumorigenic in athymic nude mice. Neoplastic transformation was achieved by irradiating cells successively. Our results showed that radiogenic cell transformation is a multistep process and that a single exposure of ionizing radiation can cause only one step of transformation. It requires, therefore, multihits to make human epithelial cells fully tumorigenic. Using a simple karyotyping method, we did chromosome analysis with cells cloned at various stages of transformation. We found no consistent large terminal deletion of chromosomes in radiation-induced transformants. Some changes of total number of chromosomes, however, were observed in the transformed cells. These transformants provide an unique opportunity for further genetic studies at a molecular level.

NASA Discipline Number 04-10↗
NASA NTRS1999

Migration of lymphocytes on fibronectin-coated surfaces: temporal evolution of migratory parameters

Lymphocytes typically interact with implanted biomaterials through adsorbed exogenous proteins. To provide a more complete characterization of these interactions, analysis of lymphocyte migration on adsorbed extracellular matrix proteins must accompany the commonly performed adhesion studies. We report here a comparison of the migratory and adhesion behavior of Jurkat cells (a T lymphoblastoid cell line) on tissue culture treated and untreated polystyrene surfaces coated with various concentrations of fibronectin. The average speed of cell locomotion showed a biphasic response to substrate adhesiveness for cells migrating on untreated polystyrene and a monotonic decrease for cells migrating on tissue culture-treated polystyrene. A modified approach to the persistent random walk model was implemented to determine the time dependence of cell migration parameters. The random motility coefficient showed significant increases with time when cells migrated on tissue culture-treated polystyrene surfaces, while it remained relatively constant for experiments with untreated polystyrene plates. Finally, a cell migration computer model was developed to verify our modified persistent random walk analysis. Simulation results suggest that our experimental data were consistent with temporally increasing random motility coefficients.

NASA Program Fundamental Space Biology↗
NASA NTRS1989

Presentation of antigen to T lymphocytes by non-immune B-cell hybridoma clones: evidence for specific and non-specific presentation

Non-immune SJL (H-2s) spleen cells were fused with non-secreting, non-antigen presenting (H-2d) Balb/c 653-myeloma cells and the hybridomas were cloned by two limiting dilutions. The resulting hybrid B-cell clones were tested for their antigen presentation capability to SJL T-cell lines that were specific for either lysozyme or myoglobin. In proliferative assays, 53% of the antigen presenting B-cell clones presented both myoglobin and lysozyme (general presenters) while the other 47% presented specifically either myoglobin or lysozyme (specific presenters). The ability to selectively present either myoglobin or lysozyme indicates that antigen presentation at the clonal level can be specific or non-specific depending on the particular B-cell clone.

B-Lymphocytes/immunology↗
NASA NTRS1988

Presentation of antigen to T lymphocytes by non-immune B-cell hybridoma clones: evidence for specific and non-specific presentation

Non-immune SJL (H-2s) spleen cells were fused with (H-2d) Balb/c 653-myeloma cells and the hybridomas were cloned by two limiting dilutions. The resulting hybrid B- cell clones were tested for their antigen presentation capability to SJL T-cell lines that were specific for either lysozyme or myoglobin. In proliferative assays, 53% of the antigen presenting B-cell clones were able to present both myoglobin and lysozyme (general presenters) while the other 47% presented specifically either myoglobin or lysozyme (specific presenters). The ability to selectively present either myoglobin or lysozyme indicates that antigen presentation at the clonal level can be specific or non-specific depending on the particular B-cell clone.

T-Lymphocytes/immunology↗
NASA NTRS2005

Tissue Engineering Using Transfected Growth-Factor Genes

A method of growing bioengineered tissues includes, as a major component, the use of mammalian cells that have been transfected with genes for secretion of regulator and growth-factor substances. In a typical application, one either seeds the cells onto an artificial matrix made of a synthetic or natural biocompatible material, or else one cultures the cells until they secrete a desired amount of an extracellular matrix. If such a bioengineered tissue construct is to be used for surgical replacement of injured tissue, then the cells should preferably be the patient s own cells or, if not, at least cells matched to the patient s cells according to a human-leucocyteantigen (HLA) test. The bioengineered tissue construct is typically implanted in the patient's injured natural tissue, wherein the growth-factor genes enhance metabolic functions that promote the in vitro development of functional tissue constructs and their integration with native tissues. If the matrix is biodegradable, then one of the results of metabolism could be absorption of the matrix and replacement of the matrix with tissue formed at least partly by the transfected cells. The method was developed for articular chondrocytes but can (at least in principle) be extended to a variety of cell types and biocompatible matrix materials, including ones that have been exploited in prior tissue-engineering methods. Examples of cell types include chondrocytes, hepatocytes, islet cells, nerve cells, muscle cells, other organ cells, bone- and cartilage-forming cells, epithelial and endothelial cells, connective- tissue stem cells, mesodermal stem cells, and cells of the liver and the pancreas. Cells can be obtained from cell-line cultures, biopsies, and tissue banks. Genes, molecules, or nucleic acids that secrete factors that influence the growth of cells, the production of extracellular matrix material, and other cell functions can be inserted in cells by any of a variety of standard transfection techniques.

Madry, Henning↗