Ascorbic acid deficiency in cultured human fibroblasts

Mesoscopic structural analysis via deep learning processing, with a special reference to in vitro alteration in collagen fibre induced by a gap junction inhibitor

Dense connective tissue, including the ligament, tendon, fascia and cornea, is formed by regularly arranged collagen fibres synthesized by fibroblasts (Fbs). The mechanism by which fibre orientation is determined remains unclear. Periodontal ligament Fbs consistently communicate with their surroundings via gap junctions (GJs), leading to the formation of a wide cellular network. A method to culture Fb-synthesized collagen fibres was previously reported by Schafer et al. ('Ascorbic acid deficiency in cultured human fibroblasts'. J. Cell Biol. 34: 83-95, 1967). This method has been applied to investigate the ability and activity of Fb collagen synthesis/phagocytosis using conventional electron microscopy (EM). However, the three-dimensional mesoscopic architecture of collagen fibres and the influence of GJ inhibitors on collagen fibre formation in vitro are poorly understood. In this study, three-dimensional mesoscopic analysis was used to elucidate the mechanism of directional fibre formation. We investigated the influence of GJ inhibitors on collagen formation driven by periodontal ligament Fbs in vitro, histomorphometrically, and the structural properties of in vitro collagen fibre on a mesoscale quantitatively, using correlative light and EM optimized for picrosirius red staining and focused ion beam-scanning EM tomography. Our results indicate that under culture conditions, in the presence of a GJ inhibitor, the orientation of collagen fibres becomes more disordered than that in the control group. This suggests that the GJ might be involved in determining fibre orientation during collagen fibre formation. Elucidation of this mechanism may help develop novel treatment strategies for connective tissue orientation disorders. Graphical Abstract.

Ascorbic Acid Enhances the Metabolic Activity, Growth and Collagen Production of Human Dermal Fibroblasts Growing in Three-dimensional (3D) Culture

Tissue engineering (TE) enables developing functional synthetic substitutes to be replaced with damaged tissues and organs instead of the use of auto or allografts. A wide range of biomaterials is currently in use as TE scaffolds. Among these materials, naturally-sourced ones are favourable due to being highly biocompatible and supporting cell growth and function whereas synthetic ones are advantageous because of the high tunability on mechanical and physical properties as well as being easy to process. Alongside the advantages of synthetic polymers, they mostly show hydrophobic behaviour that limits biomaterial-cell interaction and consequently the functioning of the developed TE constructs. In this study, we assessed the impact of L-Ascorbic acid 2-phosphate (AA2P) on improving the culture of human dermal fibroblasts (HDFs) growing on a three-dimensional (3D) scaffold made of polycaprolactone by emulsion templating technique. Our results demonstrated that AA2P enhances the metabolic activity, growth, and collagen production of HDFs when supplemented to their growth medium at 50 µg/mL concentration. It showed a great potential to be used as a growth medium supplement to circumvent the disadvantages of culturing human cells on a synthetic biomaterial that is not favoured in default. AA2P's potential to improve cell growth and collagen deposition may prove an effective way to culture human cells on 3D PCL PolyHIPE scaffolds for various TE applications.

The Development of Tissue Engineering Scaffolds Using Matrix from iPS-Reprogrammed Fibroblasts

Tissue engineering solutions have been widely explored for enhanced healing of skin wounds. Diabetic foot ulcers (DFU) are particularly challenging wounds to heal for a variety of reasons, including aberrant ECM, dysregulation of vascularization, and persistent inflammation. Tissue engineering approaches, such as porous collagen-based scaffolds, have shown promise in replacing the current treatments of surgical debridement and topical treatments. Collagen-glycosaminoglycan scaffolds, which are FDA approved for diabetic foot ulcers, can benefit from further functionalization by incorporation of additional signaling factors or extracellular matrix molecules. One option for this is to incorporate matrix from a rejuvenated cell source, as wounds in younger patients heal more quickly. Induced pluripotent stem cells (iPS) are generated from somatic cells and share many functional similarities with embryonic stem cells (ES), while avoiding the ethical concerns. Fibroblasts differentiated from iPS cells have been shown to enrich their ECM with glycosaminoglycan (GAGs), collagen Type III and fibronectin, to have an increased ECM production, and to be pro-angiogenic. Here we describe a technique to grow matrix from post-iPS fibroblasts, and to develop a scaffold from this matrix, in combination with collagen, with the goal of enhancing wound healing. By activating scaffolds with extracellular matrix (ECM) from fibroblasts derived from an iPS source (post-iPSF), the scaffolds are enriched with beneficial elements like GAGs, collagen type III, fibronectin, and VEGF. We believe these scaffolds can enhance skin regeneration and that the techniques can be modified for other tissue engineering applications.

Scaffolds Functionalized with Matrix from Induced Pluripotent Stem Cell Fibroblasts for Diabetic Wound Healing

Diabetic foot ulcers (DFUs) are chronic wounds, with 20% of cases resulting in amputation, despite intervention. A recently approved tissue engineering product-a cell-free collagen-glycosaminoglycan (GAG) scaffold-demonstrates 50% success, motivating its functionalization with extracellular matrix (ECM). Induced pluripotent stem cell (iPSC) technology reprograms somatic cells into an embryonic-like state. Recent findings describe how iPSCs-derived fibroblasts ("post-iPSF") are proangiogenic, produce more ECM than their somatic precursors ("pre-iPSF"), and their ECM has characteristics of foetal ECM (a wound regeneration advantage, as fetuses heal scar-free). ECM production is 45% higher from post-iPSF and has favorable components (e.g., Collagen I and III, and fibronectin). Herein, a freeze-dried scaffold using ECM grown by post-iPSF cells (Post-iPSF Coll) is developed and tested vs precursors ECM-activated scaffolds (Pre-iPSF Coll). When seeded with healthy or DFU fibroblasts, both ECM-derived scaffolds have more diverse ECM and more robust immune responses to cues. Post-iPSF-Coll had higher GAG, higher cell content, higher Vascular Endothelial Growth Factor (VEGF) in DFUs, and higher Interleukin-1-receptor antagonist (IL-1ra) vs. pre-iPSF Coll. This work constitutes the first step in exploiting ECM from iPSF for tissue engineering scaffolds.

The effect of continuous enteral tube feeding on various nutritional parameters in patients with disseminated malignant melanoma during intensive chemotherapy

In a prospective study the effect of continuous enteral tube feeding was evaluated on various nutritional parameters in patients with disseminated malignant melanoma during 13 chemotherapy courses employing bleomycin, DTIC, vindesine and actinomycin D. The patients received a quantity of calories according to their pretreatment intake, but complete metabolic equilibrium could not be obtained during chemotherapy. Although the weight/height index remained unchanged, a decrease of serum albumin and prealbumin level occurred during all 13 treatment courses. Transferrin level decreased during 11 of these courses and cholinesterase level during 12. Triceps skinfold thickness and arm muscle circumference diminished equally. Serum prealbumin was the first nutritional parameter to fall during chemotherapy and seems to be a very sensitive indicator of the occurrence of nutritional imbalance. The plasma vitamin C level was low before treatment while during treatment both vitamin C and vitamin A level fell quickly even though the nutritional intake of these vitamins was adequate. We conclude that continuous enteral tube feeding, which is a feasible method of feeding, can to some extent fulfill the nutritional needs of patients treated with intensive chemotherapy.

Testing of nine different xeno-free culture media for human embryonic stem cell cultures

BACKGROUND

Human embryonic stem cells (hESC) are excellent candidates for cell replacement therapies. However, currently used culture conditions contain animal-derived components that bear a risk of transmitting animal pathogens and incorporation of non-human immunogenic molecules to hESC.

METHODS

Nine xeno-free culture media were compared with the conventional serum replacement (ko-SR) containing media in the culture of hESC on human feeder cells. Cultured hESC were characterized immunocytochemically and by fluorescence-activated cell sorter analysis. The differentiation potential of hESC cultured with xeno-free media was determined with the RT-PCR analysis.

RESULTS

The hESC cultured in xeno-free media differentiated or the proliferation decreased substantially. Under some test conditions, the morphology of the feeder cells was altered considerably. The hESC cultured with human serum underwent excessive differentiation in the beginning of culture, but a fraction of hESC was able to adapt to culture conditions containing 20% of human serum.

CONCLUSIONS

None of the studied xeno-free media was able to maintain the undifferentiated growth of hESC. The medium containing 20% human serum was found to sustain undifferentiated hESC proliferation to some extent, yet was inferior to the conventional ko-SR-containing medium.

Heterogeneous distribution of the precursor of type I and type III collagen and fibronectin in the rough endoplasmic reticulum of palatal mesenchymal cells of the mouse embryo cultured in ascorbate-depleted medium

In order to examine the intracellular distribution of precursors of type I and type III collagen and fibronectin in the palatal mesenchymal (MEPM) cells of the mouse embryo cultured under ascorbate-deficient conditions, immuno-electron-microscopic studies were carried out by use of affinity purified antibodies for these proteins. MEPM cells were obtained from the palatal shelves of 14-day-old mouse fetuses and cultured for 3-7 days in medium, either with or without 50 ng/dish/day ascorbic acid. Results obtained were as follows: (1) Although the rough endoplasmic reticulum (rER) of MEPM cells cultured for 5 days in ascorbate-supplemented medium was flattened, that in cells cultured in ascorbate-deficient medium had a distended or vesicular appearance. (2) Vesicular or distended rER showed heterogeneous staining for both type I and type III collagen, namely, some parts of rER showed positive staining for both types of collagen, while others showed negative staining. (3) Both type I and type III collagen showed codistribution in the same vesicular rER. (4) Vesicular rER showed negative or very faint labelling for fibronectin. These results may suggest regional differences in the function of rER.

The interaction of human papillary and reticular fibroblasts and human keratinocytes in the contraction of three-dimensional floating collagen lattices

Fibroblasts derived from the papillary and reticular dermis of human skin and human keratinocytes show differences in their abilities to contract floating three-dimensional gels constructed from type I collagen. Reticular fibroblasts produce greater gel contraction than papillary fibroblasts. When equal numbers of papillary and reticular fibroblasts are mixed in the gels, papillary fibroblasts consistently inhibit gel contraction by reticular fibroblasts indicating interaction between these cell types in the contraction process. Surprisingly, keratinocytes alone produce greater gel contraction than that produced by either fibroblast type. Cooperativity in the gel contraction process is observed when fibroblasts are incorporated into the collagen matrix and keratinocytes are seeded onto the gel surface. Keratinocytes and dermal fibroblasts adhere to the collagen fibril to induce gel contraction by different mechanisms. Fibroblast contraction of collagen gels does not require fibronectin but is a serum-dependent reaction. In contrast, keratinocyte contraction of collagen gels occurs in a serum-free environment. Polyclonal, affinity-purified antibodies to human plasma fibronectin at high concentrations do not inhibit gel contraction by keratinocytes, making unlikely the possibility that fibronectin synthesized by the keratinocyte is a significant factor in the gel contraction process. We are currently examining the possibilities either that keratinocytes are synthesizing other adhesion proteins or that receptors on the cell surface can interact directly with the collagen fiber.

Changes in plasma and buffy layer vitamin C following surgery

Postoperative changes in plasma and buffy layer (BL) vitamin C were studied in 107 patients receiving either 0 (37 patients), 100 mg (33 patients) or 500 mg (37 patients) vitamin C supplements daily. In patients receiving no supplement plasma vitamin C concentrations had fallen (mean 33 per cent) by the first postoperative day and thereafter changed little. The falls occurred irrespective of initial plasma concentration, were greater the higher the initial concentration, but tended to be proportional to the length of operation. In patients given supplements this loss of vitamin C was evident but modified, and from the second postoperative day the response to the supplements was as would have been expected in non-operated subjects. The most probable explanation for the loss of vitamin C from plasma was an increased urinary excretion during operation. Changes in BL vitamin C concentrations were studied in relation to changes in leucocyte and platelet counts. The previously reported postoperative falls in BL vitamin C were found to be the result of a major artefact in the methods routinely used for BL vitamin C estimation, caused by changes in the leucocyte and platelet populations, most importantly the platelet to leucocyte ratio. No true demand for vitamin C, as measured from the buffy layer cells, was evident.

Comparative observation of fibroblasts derived from the papillary and reticular dermis of infants and adults: growth kinetics, packing density at confluence and surface morphology

We have confirmed the reports of Harper and Grove (Science, 204 (1979) 526-527), and Azzarone and Macierira-Coehlo (J. Cell Sci., 57 (1982) 177-187) that fibroblasts derived from the papillary dermis have greater in vitro growth potential and longer replicative lifespans than genomically identical fibroblasts derived from the reticular dermis. In addition we demonstrate that the kinetics of cell replication differ for papillary and reticular fibroblasts derived from infant and adult donors. Infant papillary fibroblasts replicate at faster rates than reticular fibroblasts throughout the growth cycle. Adult papillary and reticular fibroblasts replicate at similar rates at low cell densities, but exponential growth of reticular fibroblasts slows at lower cell densities than papillary fibroblasts suggesting that they are more sensitive to density-dependent inhibition of replication. The surface morphologies of reticular fibroblasts and papillary fibroblasts at confluence correlate with their growth kinetics. The decreased cell yields of reticular fibroblasts appears related to the spreading behaviors of individual cells which stretch and occupy more area of the growth surface than do papillary fibroblasts. These data and the reports cited clearly show that one must account for the presence of at least two distinct populations of dermal fibroblasts when examining their biological properties in vitro.

Morphological alterations in epithelial cells of the mouse gallbladder 30 hours after treatment with lithogenic diet

Mice were fed a gallstone inducing diet. Thirty hours after treatment, distinct morphological alterations in the gallbladder epithelium occurred. The most striking effect was the short-term appearance of large cisternae, which emerge as a result of coalescence of dilated cavities of the rough endoplasmic reticulum. At the same time, an increased storage of small granular material was observed. These alterations did not appear after treatment lasting for less or more than thirty hours. The development started with an enlargement of the endoplasmic cavities, whereas the Golgi apparatus did not seem to undergo transformations; therefore, a transport stop of the secretory products of the epithelial cells must be located at the connection between both organelles. The formation of the endoplasmic cisternae seemed to be caused by a reversible block of the intracellular transport pathway of the secretion products.

Immunocytochemical localization of procollagen and fibronectin in human fibroblasts: effects of the monovalent ionophore, monensin

The monovalent ionophore monensin inhibits the secretion of both procollagen and fibronectin from human fibroblasts in culture. The distribution of these proteins in control and inhibited (5 x 10(-7) M monensin) cells has been studied by immunofluorescence microscopy. In control cells, both antigens are present throughout the cytoplasm and in specific deposits in a region adjacent to the nucleus, which we identify as a Golgi zone by electron microscopy. Treatment of cells with monensin causes intracellular accumulation of procollagen and fibronectin, initially in the juxta-nuclear region and also subsequently in peripheral regions. Electron microscope studies reveal that in such cells the juxta-nuclear Golgi zone becomes filled with a new population of smooth-membraned vacuoles and that normal Golgi complexes are not found. Immunocytochemically detected procollagen and fibronectin are localized in the region of these vacuoles, whereas more peripheral deposits correspond to the dilated cisternae of rough endoplasmic reticulum, which are also caused by monensin. Procollagen and fibronectin are often codistributed in these peripheral deposits. Accumulation of exportable proteins in Golgi-related vacuoles is consistent with previous analyses of the monensin effect. The subsequent development of dilated rough endoplasmic reticulum also containing accumulated proteins may indicate that there is an additional blockade at the exit from the endoplasmic reticulum, or that the synthesized proteins exceed the capacity of the Golgi compartment and that their accumulation extends into the endoplasmic reticulum.

Biosynthesis and release of glycoproteins by human skin fibroblasts in culture

1. Confluent human skin fibroblasts maintained in a chemically defined medium incorporate l-[1-(3)H]fucose in a linear manner with time into non-diffusible macromolecules for up to 48h. Chromatographic analysis demonstrated that virtually all the macromolecule-associated (3)H was present as [(3)H]fucose. 2. Equilibrium CsCl-density-gradient centrifugation established that [(3)H]fucose-labelled macromolecules released into the medium were predominantly glycoproteins. Confirmation of this finding was provided by molecular-size analyses of the [(3)H]fucose-labelled material before and after trypsin digestion. 3. The [(3)H]fucose-labelled glycoproteins released into fibroblast culture medium were analysed by gel-filtration chromatography and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. These techniques demonstrated that the major fucosylated glycoprotein had an apparent mol.wt. of 230000-250000; several minor labelled species were also detected. 4. Dual-labelling experiments with [(3)H]fucose and (14)C-labelled amino acids indicated that the major fucosylated glycoprotein was synthesized de novo by cultured fibroblasts. The non-collagenous nature of this glycoprotein was established by three independent methods. 5. Gel-filtration analysis before and after reduction with dithiothreitol showed that the major glycoprotein occurs as a disulphide-bonded dimer when analysed under denaturing conditions. Further experiments demonstrated that this glycoprotein was the predominant labelled species released into the medium when fibroblasts were incubated with [(35)S]cysteine. 6. The relationship between the major fucosylated glycoprotein and a glycoprotein, or group of glycoproteins, variously known as fibronectin, LETS protein, cell-surface protein etc., is discussed.

Determination of L-ascorbic acid levels in culture medium: concentrations in commercial media and maintenance of levels under conditions of organ culture

The method of Deutsch and Weeks was modified to provide a reliable and reasonably quick method for assaying the L-ascorbic acid content of culture medium. The modified method was used to determine the decay of L-ascorbic acid under various conditions of culture and the concentration of the vitamin in commercially prepared media. The half-life of L-ascorbic acid in a modified New circulator gassed with 95% O2 + 5% CO2 was 1.5 hr.; and when gassed with 20% O2 + 5% CO2 + 75% N2, about 2 hr. In Petri dishes gassed with 20% O2 + 5% CO2 + 75% N2, the half-life of L-ascorbic acid was 0.9 hr. About 4% of the L-ascorbic acid was lost per day when medium was stored at 0 degrees C and about 9% per day when stored at 5 degrees C. When medium with an initial content of 300 microng per ml was stored at room temperature, the half-life was found to be 15.5 hr. The L-ascorbic acid in five commercially available media, which contain the vitamin in their formulations, was assayed immediately after their delivery to the laboratory. The values of L-ascorbic acid measured in these media were in all cases far lower than prescribed. A continuous-flow organ culture system has been designed which allows the provision of a relatively constant level of L-ascorbic acid to explant by taking advantage of the slow oxidation of L-ascorbic acid at 0 degrees C.

Fine structure of rabbit articular chondrocytes in tissue culture during logarithmic and confluent stages of growth

Ultrastructural changes in cultured articular cartilage chondrocytes from rabbit, during two growth phases were examined by transmission and scanning electron microscopy. Cells in logarithmic growth are characterized by an abundance of intracellular lipoid bodies, little development of rough endoplasmic reticulum (RER), and few cytoplasmic microfilaments. As the cells reach confluency there is a concomitant development of RER, organization and abundance of microfilaments, loss of lipoid bodies, and increase in the number of mitochondria. The fine structure of cultured chondrocytes is very similar to that of rabbit cartilage cells in situ, in that numerous lipoid bodies and microfilaments are prominent features in both cases.

Induction of fibrogenesis by lung antibody-treated macrophages

Using a modification of an in vitro model of fibrogenesis, lung connective tissue antibodies have been shown to stimulate macrophages to release a collagen stimulating factor acting on fibroblast target cells. This stimulation was measured by increased hydroxyproline production from fibroblasts that had reached stationary growth phase. In subcytotoxic amounts, this antibody had no such effect directly on fibroblasts. These findings further illustrate the value of studying fibrogenesis by the in vitro method.

Effect of ascorbic acid on arylsulfatase A and B activities in human chondrocyte cultures

Cultured normal human articular cartilage chondrocytes exhibited decreasing levels of arylsulfatase A and B activities when grown in the presence of increasing levels of ascorbic acid (0 to 90 mug/ml) in the media. That this was not a general effect on all lysosomal enzymes was supported by the increase in acid phosphatase activity and no change in beta-glucuronidase activity observed with increasing levels of vitamin C under identical culture conditions. No decrease in either arylsulfatase activity was observed when ascorbic acid was replaced by ascorbate-2-sulfate. Ascorbic acid did not inhibit either arylsulfatase activity when added directly to the assay mixture. These data, combined with results of mixing experiments, suggest that the effect of vitamin C is mediated through cellular factors produced in response to its inclusion in the growth media.

Insect cell culture: improved media and methods for initiating attached cell lines from the Lepidoptera

Several cell lines from the pupae of the noctuid moth species Spodoptera frugiperda, Heliothis zea, and Trichoplusia ni were isolated on a synthetic medium containing insect hemolymph and turkey serum. These lines were progressively adapted to improved media free of insect hemolymph but containing one or more of the following sera: turkey, chicken, and fetal calf. Primary culture tissue disruption was improved by substituting collagenase for trypsin. Primary culture survival was improved by controlling the total tissue volume per unit medium volum, and by the addition of glutathione to prevent melanization and to improve cell adherence to the substrate. Culture servival was also improved by heat treatment of sera, control of medium osmolality, and changes in the basal medium and serum supplementation. Some of these changes also resulted in improved growth giving higher maximal cell counts. Comparative cell growth on the various media was graphed and generation times given.

Importance of homocysteine-induced abnormalities of proteoglycan structure in arteriosclerosis

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The effect of scurvy on hexosamine-containing substances in healing wounds in guinea pigs

1. Granulation tissue from healing tendonectomy wounds in guinea pigs was analysed and the effects of inanition and ascorbic acid deficiency on this tissue were investigated. 2. Inanition produced no significant effect on either the glucosamine or the galactosamine content of the tissue. Ascorbic acid deficiency decreased the galactosamine content without affecting the glucosamine content. 3. Fractionation of papain-digested granulation tissue gave three major fractions, which behaved respectively as glycopeptide, hyaluronic acid and a sulphated glycosaminoglycan mixture. At least half of the sulphated glycosaminoglycan mixture behaved as dermatan sulphate. 4. Inanition produced no consistent effect on the fractions examined. In ascorbic acid deficiency, a decrease in the sulphated glycosaminoglycan fraction was observed, which accounted for the decreased galactosamine content of the tissue. This was accompanied by a decrease in hyaluronic acid and a slight increase in the glycopeptide fraction.

Study of the Hurler syndrome using cell culture: definition of the biochemical phenotype and the effects of ascorbic acid on the mutant cell

Fibroblasts from patients with Hurler syndrome retain a distinctive biochemical phenotype when grown in culture which is characterized by increased synthesis of both nonsulfated and sulfated glycosaminoglycans. Ascorbic acid reinforces the phenotypic expression of the biochemical abnormality, producing not only increased synthesis of sulfated glycosaminoglycans, but selective retention of sulfated glycosaminoglycans within the cell. Although the synthesis of nonsulfated glycosaminoglycans is also increased, these compounds, particularly hyaluronic acid are not retained by the cell but are secreted into the medium. Analyses of urine from patients with Hurler syndrome show increased absolute concentrations of nonsulfated glycosaminoglycans in addition to the expected increase in sulfated glycosaminoglycans. This indicates that the biochemical phenotype as defined in cell culture is not an artifact of the experimental model but reflects the biochemical defect in the patient. Redefinition of the biochemical defect to include nonsulfated as well as sulfated glycosaminoglycans contradicts explanations of this disease which are based on a single structural gene mutation.