Role of ascorbic acid in procollagen expression and secretion by human intestinal smooth muscle cells

Discriminant Principal Component Analysis of ToF-SIMS Spectra for Deciphering Compositional Differences of MSC-Secreted Extracellular Matrices

Identifying characteristic extracellular matrix (ECM) variants is a key challenge in mechanistic biology, bioengineering, and medical diagnostics. The reported study demonstrates the potential of time-of-flight secondary ion mass spectrometry (ToF-SIMS) to detect subtle differences between human mesenchymal stromal cell (MSC)-secreted ECM types as induced by exogenous stimulation or emerging pathology. ToF-SIMS spectra of decellularized ECM samples are evaluated by discriminant principal component analysis (DPCA), an advanced multivariate analysis technique, to decipher characteristic compositional features. To establish the approach, signatures of major ECM proteins are determined from samples of pre-defined mixtures. Based on that, sets of ECM variants produced by MSCs in vitro are analyzed. Differences in the content of collagen, fibronectin, and laminin in the ECM resulting from the combined supplementation of MSC cultures with polymers that induce macromolecular crowding and with ascorbic acid are detected from the DPCA of ToF-SIMS spectra. The results are verified by immunostaining. Finally, the comparative ToF-SIMS analysis of ECM produced by MSCs of healthy donors and patients suffering from myelodysplastic syndrome display the potential of the novel methodology to reveal disease-associated alterations of the ECM composition.

Valve interstitial cell culture: Production of mature type I collagen and precise detection

Collagen often acts as an extracellular and intracellular marker for in vitro experiments, and its quality defines tissue constructs. To validate collagen detection techniques, cardiac valve interstitial cells were isolated from pigs and cultured under two different conditions; with and without ascorbic acid. The culture with ascorbic acid reached higher cell growth and collagen deposition, although the expression levels of collagen gene stayed similar to the culture without ascorbic acid. The fluorescent microscopy was positive for collagen fibers in both the cultures. Visualization of only extracellular collagen returned a higher correlation coefficient when comparing the immunolabeling and second harmonic generation microscopy images in the culture with ascorbic acid. Lastly, it was proved that the hydroxyproline strongly contributes to the second-order susceptibility tensor of collagen molecules, and therefore the second harmonic generation signal is impaired in the culture without ascorbic acid.

The effect of growth factors on both collagen synthesis and tensile strength of engineered human ligaments

Growth factors play a central role in the development and remodelling of musculoskeletal tissues. To determine which growth factors optimized in vitro ligament formation and mechanics, a Box-Behnken designed array of varying concentrations of growth factors and ascorbic acid were applied to engineered ligaments and the collagen content and mechanics of the grafts were determined. Increasing the amount of transforming growth factor (TGF) β1 and insulin-like growth factor (IGF)-1 led to an additive effect on ligament collagen and maximal tensile load (MTL). In contrast, epidermal growth factor (EGF) had a negative effect on both collagen content and MTL. The predicted optimal growth media (50 μg/ml TGFβ, IGF-1, and GDF-7 and 200 μM ascorbic acid) was then validated in two separate trials: showing a 5.7-fold greater MTL and 5.2-fold more collagen than a minimal media. Notably, the effect of the maximized growth media was scalable such that larger constructs developed the same material properties, but larger MTL. These results show that optimizing the interactions between growth factors and engineered ligament volume results in an engineered ligament of clinically relevant function.

Bone regeneration and neovascularization processes in a pellet culture system for periosteal cells

Reliable bone regeneration can be achieved with a pellet culture system using bovine periosteal cells. However, bone regeneration and neovascularization processes in this system have remained unclear. The present study aimed to clarify the extracellular environment and neovascularization process. To detect components of the extracellular matrix secreted by cells and to identify the conditions necessary for bone regeneration in the body, Western blotting and in vivo tests in nude mice were performed. Cells were cultured with or without ascorbic acid and culture supernatant was precipitated. Western blotting showed that culture supernatant contained collagen type I, procollagen type I, and procollagen type I C-terminus when cells were cultured with ascorbic acid. Cells cultured with ascorbic acid formed partial bony tissues at 2 weeks after grafting to nude mice, while bone formation was missing without ascorbic acid. Immunostaining was performed using species-specific vascular endothelial cell markers to ascertain whether vascular endothelial cells were bovine or murine (nude mouse). Immunohistological methods showed vascular endothelial cells in osseous tissue formed in the subcutaneous tissue of nude mice were murine. Extracellular matrix synthesis in vitro and host blood flow in vivo are essential for bone regeneration.

Oxidative stress, tissue remodeling and regression during amphibian metamorphosis

Anuran metamorphosis is characterized by rapid and drastic changes in the body form and function under the influence of thyroid hormones. We evaluated the involvement of reactive oxygen species and antioxidant defenses during intestinal remodeling and tail regression of tadpoles of Xenopus laevis. Oxidative stress resulting from depletion in catalase and reduced glutathione, and simultaneous increase in lipid peroxidation during intestinal remodeling as well as tail regression are probably responsible for cell death and differentiation in these organs. Gene expression data for superoxide dismutase and catalase supports this contention. A dramatic increase in another antioxidant, ascorbic acid content of both these organs during metamorphic climax indicates its multifactor role such as collagen synthesis in intestine and controlled tail regression. These findings suggest that the cellular environment in the intestine and tail becomes progressively more oxidizing during its remodeling and regression respectively.

Quantitative analysis of the synthesis and secretion of type VII collagen in cultured human dermal fibroblasts with a sensitive sandwich enzyme-linked immunoassay

Type VII collagen is the major component of anchoring fibrils in the epidermal basement membrane. Its expression has been analyzed by immunostaining or Northern blotting, but rarely at the protein level. In this study, we have quantitatively examined the effects of ascorbic acid and various cytokines/growth factors on the protein synthesis and secretion of type VII collagen by human dermal fibroblasts in culture, using a developed, highly sensitive sandwich enzyme-linked immunoassay with two kinds of specific monoclonal antibodies against the non-collagenous domain-1. Ascorbic acid and its derivative induced a twofold increase in type VII collagen synthesis, and markedly increased the secretion of type VII collagen into the medium when compared with the control culture. This effect was not influenced by the presence of transforming growth factor-beta1 (TGF-beta1). The synthesis of type VII collagen was elevated by TGF-beta1, platelet-derived growth factor, tumor necrosis factor-alpha, and interleukin-1beta, but not by TGF-alpha. Thus, our data indicate that the synthesis and secretion of type VII collagen in human dermal fibroblasts are regulated by ascorbate and the enhancement of type VII collagen gene expression by cytokines/growth factors is accompanied with elevated production of type VII collagen at the protein level.

Serum-dependent effects on adult and fetal tendon fibroblast migration and collagen expression

Cell migration and extracellular matrix synthesis play an important role in the wound-healing response to injury. Several studies have described differences in migratory behavior and collagen biosynthetic activity in adult vs. fetal skin fibroblasts. The objective of this study was to examine the serum- and age-dependent effects on cell migration and collagen expression in tendon fibroblasts. Medial tendon fibroblasts were isolated from pregnant ewes and their fetuses, and cultured with and without serum for up to 7 days. Cell migration was determined by quantitative image analysis, and collagen expression was assessed by reverse transcription-polymerase chain reaction and immunohistochemical staining. In serum-containing medium, tendon fibroblasts migrated significantly faster than cells in serum-free medium. Additionally, fetal tendon fibroblasts migrated significantly faster than adult tendon fibroblasts under both culture conditions. The expression of types I and III collagen mRNA was significantly up-regulated in tendon cell populations in serum-free medium compared with those in serum-containing medium. Quantitative assessment of collagen staining indicated that fetal tenocytes produced more type I collagen than adult tenocytes under both culture conditions. These findings suggest that there is an inherent difference between adult and fetal tendon fibroblasts, which may have implications in the wound-healing response in tendons.

Assembly of bone marrow stromal cell sheets with knitted poly (L-lactide) scaffold for engineering ligament analogs

The current cell seeding technique has several disadvantages, such as low efficiency of cell attachment to scaffolds and the limited strength of cell-gel composite adhesion to scaffold. These problems warrant further study to improve the assembly of cell to scaffold. Therefore this study aims to fabricate a bone marrow stromal cells (bMSCs) sheet and assemble it on a knitted poly (L-lactide) (PLLA) scaffold for engineering ligament analogs. bMSCs were cultured to form a cell sheet in the presence of ascorbic acid. Once a sheet of bMSCs was obtained, it was assembled onto the knitted scaffold by a wrapping technique. Then the assembled structure was held in place in a spinner flask for 4 weeks. The macromorphology, histology, and biomechanics of the grafts were evaluated. The composite of cell sheet/PLLA scaffold constructs had transformed into tissuelike ligament analogs. Immunohistochemical analysis showed that the components of the analogs were similar to that of ligament tissues, consisting primarily of collagen type I and small amount of collagen type III and tenascin. The failure force of the cell/scaffold assembly under tension (46.68+/-2.29 N) was higher than that of the scaffold group (43.58+/-2.41 N; p<0.05), but tensile stiffness of the cell/scaffold group (20.6+/-1.417 N/mm) was significantly lower than that of the scaffold group (27.6+/-1.449 N/mm; p<0.05). These data showed that the incorporation of bMSCs sheet onto the PLLA scaffold could make the analog stronger and more stretchable. Therefore the approach of assembling bMSCs sheet onto knitted PLLA scaffold is promising for producing tissuelike and functional ligament analogs under dynamic fluid situation for the purpose of anterior cruciate ligament (ACL) reconstruction.

Evaluation of the effect of ascorbic acid treatment on wound healing in mice exposed to different doses of fractionated gamma radiation

Alteration of the radiation-induced changes in wound contraction, collagen synthesis and wound histology by ascorbic acid was studied in mice exposed to 10, 16 and 20 Gy of fractionated (2 Gy/fraction) gamma radiation. The animals were given double-distilled water or ascorbic acid daily before exposure to 2 Gy/day of fractionated irradiation. A full-thickness skin wound was created on the dorsum of the irradiated mice, and the progression of wound contraction and collagen synthesis were examined and histological evaluations were carried out at various times after wounding. Irradiation caused a dose-dependent delay in wound contraction, and pretreatment with ascorbic acid resulted in a significant increase in wound contraction. The greatest increase in wound contraction was observed 6 and 9 days after wounding in both groups. Pretreatment with ascorbic acid augmented the synthesis of collagen significantly as revealed by an increase in hydroxyproline content. The collagen deposition and fibroblast and vasculature densities declined in a dose-dependent manner in groups receiving radiation alone as indicated by histological evaluation. Pretreatment with ascorbic acid ameliorated the observed effect significantly. These studies demonstrate that pretreatment with ascorbic acid resulted in a significant reduction of radiation-induced delay in wound healing as shown by earlier wound closure and increased collagen content and fibroblast and vascular densities.

Acylated ascorbate stimulates collagen synthesis in cultured human foreskin fibroblasts at lower doses than does ascorbic acid

Acylated derivatives of ascorbic acid were found to be active in a number of biochemical and physiological processes. In the present study we investigated the effects of 6-O-palmitoyl ascorbate on collagen synthesis by cultured foreskin human fibroblasts. Our observations indicate a marked stimulatory effect on collagen synthesis by 6-O-palmitoyl ascorbate in the concentration range of 5-20 microM, while the synthesis stimulated by ascorbic acid was maximal at concentrations of 20-100 microM. Cells treated with 10 microM palmitoyl ascorbate for 36 h exhibited a production of collagen threefold greater than those in the presence of 10 microM ascorbic acid, and it was about the same as in cells treated with 100 microM ascorbic acid. By 48 h differences were not significant. Acylated ascorbate impaired vitality of the treated fibroblasts at concentrations exceeding 20 microM in media supplemented with 0.5% FCS. However, most of the cytotoxic effect was neutralized by FCS at a concentration of 10%. The resistance of acylated ascorbate against oxidative degradation as well as the role of free radicals in the modulation of collagen synthesis by ascorbic acid and by its derivatives is discussed.

Ascorbate and glutathione homeostasis in vascular smooth muscle cells: cooperation with endothelial cells

Human umbilical vein smooth muscle cells (HUVSMCs) utilize extracellular cystine, glutathione (GSH), and N-acetylcysteine (NAC) to synthesize cellular GSH. Extracellular cystine was effective from 5 microM, whereas GSH and NAC were required at 100 microM for comparable effects. The efficacy of extracellular GSH was dependent on de novo GSH synthesis, indicating a dependence on cellular gamma-glutamyltransferase (glutamyl transpeptidase). Coculture of syngenetic HUVSMCs and corresponding human umbilical vein endothelial cells (HUVECs) on porous supports restricted cystine- or GSH-stimulated synthesis of HUVSMC GSH when supplied on the "luminal" endothelial side. Thus HUVSMC GSH rapidly attained a steady-state level below that achieved in the absence of interposed HUVECs. HUVSMCs also readily utilize both reduced ascorbate (AA) and oxidized dehydroascorbate (DHAA) over the range 50-500 microM. Phloretin effectively blocked both AA- and DHAA-stimulated assimilation of intracellular AA, indicating a role for a glucose transporter in their transport. Uptake of extracellular AA was also sensitive to extracellular, but not intracellular, thiol depletion. When AA was applied to the endothelial side of the coculture model, assimilation of intracellular AA in HUVSMCs was restricted to a steady-state level below that achieved by free access.

Development of pseudointima and stenosis after transjugular intrahepatic portasystemic shunts: characterization of cell phenotype and function

The clinical utility of transjugular intrahepatic portasystemic shunts (TIPS) is frequently complicated by the ingrowth of tissue into the stent lumen, causing stent stenosis. These studies were undertaken to define the cellular and matrix components of the pseudointima, define the phenotype and function of the mesenchymal cells in the pseudointima and maintain them in culture, and to study the differences between stenotic and nonstenosed stents. A total of 35 stents were evaluated. TIPS pseudointima were examined histologically, by immunohistochemistry and in situ hybridization to determine the cellular and connective tissue constituents. Mesenchymal cells were grown from tissue within the TIPS and around it, and their phenotype was studied and compared with control smooth muscle cells and fibroblasts. Masson's trichrome staining of histological sections demonstrated that TIPS tissue was composed of collagen and palisades of mesenchymal cells and was lined by an endothelium. Immunostaining demonstrated strong and uniform alpha-smooth muscle staining in TIPS mesenchymal cells and peri-TIPS cells. Type I procollagen mRNA expression was demonstrated in mesenchymal cells in and around the stent by in situ hybridization. TIPS mesenchymal cells secreted less radiolabeled fibronectin, and far more type III, relative to type I, collagen compared with peri-TIPS cells. TIPS cells also expressed high levels of type III procollagen mRNA compared with peri-TIPS cells. There was no difference between stenotic stents and nonstenosed stents with respect to clinical features, time from stenting, gross morphology, histology, presence of bile fistulae, and cell phenotype. However, smooth muscle cells (SMC) from stenotic stents demonstrated both greater cell proliferation and collagen I and III secretion compared with those from nonstenosed stents. These data demonstrate that TIPS stenosis results from an accumulation of collagen and proliferation of SMC within the stent lumen.

Effects of ascorbic acid on levels of fibronectin, laminin and collagen type 1 in bovine trabecular meshwork in organ culture

PURPOSE

Fibronectin, laminin and collagen type I are important extracellular matrix products of trabecular meshwork cells. This study was performed to examine the effects of ascorbic acid, a significant component in the aqueous humor, on the levels of these proteins in trabecular meshwork cells maintained in organ culture.

METHODS

The anterior segment of freshly enucleated bovine eyes was perfused in a modified organ culture system. Three cultures were set up simultaneously. One received serum-free medium containing 100 micrograms/ml of ascorbic acid, one received 250 micrograms/ml of ascorbic acid and one served as a control. After 72 h, the tissues were processed for paraffin sections and immunostaining was conducted using an avidin-biotin-peroxidase complex method. Western blot and dot blot assays were performed on tissue extracts.

RESULTS

Compared with the controls, the staining for fibronectin and laminin was markedly enhanced in trabecular meshwork tissues treated with both concentrations of ascorbic acid. Increased collagen type I production by trabecular meshwork cells was also demonstrated in the presence of ascorbic acid. Western blot and dot blot results confirmed the immunostaining findings.

CONCLUSIONS

Ascorbic acid promotes production of fibronectin, laminin and collagen type I by trabecular meshwork cells. The organ culture results are consistent with those obtained previously from tissue culture studies.

Healing in the gastrointestinal tract

Healing in the GI tract is rapid when free of complications: Unlike cutaneous healing, in which progress can be observed on a daily basis and intervention instituted early if necessary, healing of the intestinal anastomosis is anatomically obscured from inspection, allowing the surgeon only the patient's parameters of general well-being to judge the success of the operation. For the same reason, complications usually require re-operation, with the associated morbidity of a laparotomy and additional general anesthetic. This places a great responsibility on the surgeon to be cognizant of all the preoperative, intraoperative, and postoperative factors relating to anastomotic healing that might compromise the healing process. Bearing these in mind, along with attention to technical detail, should limit complications to an acceptable level. Patients most at risk are (1) those who perioperatively develop physiologic problems that lead to shock, hypoxia, and resultant anastomotic ischemia, (2) those with radiation-induced tissue injury, (3) those with sepsis, and (4) those with preoperative bowel obstruction. Malnourishment, malignancy, diabetes, steroids, and age also influence outcome to varying degrees. Future advancement in the field of GI healing lies in our ability to manipulate the early struggle between collagen synthesis and collagen breakdown. A profound understanding of the molecular and biochemical pathways and the factors that control them will bring us closer to this goal. Clinically, this may be accomplished by the introduction of wound healing enhancers into the anastomotic site, possibly by incorporating them into suture materials, biofragmentable anastomotic rings, or staple materials. Already much is known about the influence of different cytokines and growth factors on collagen regulation, knowledge that will help resolve many of the long-standing problems associated with GI surgery.

Cleavage of type I procollagen by human mast cell chymase initiates collagen fibril formation and generates a unique carboxyl-terminal propeptide

The ability of human mast cell chymase and tryptase to process procollagen was examined. Purified human intestinal smooth muscle cell procollagen was incubated with human mast cell tryptase or human mast cell chymase. Purified chymase, but not tryptase, exhibited procollagen proteinase activity in the presence of EDTA. Addition of purified porcine heparin over a range of 0.1-100 microg/ml did not affect either the rate or the products of procollagen chymase cleavage. The cleavage site of chymase on the pro-alpha1(I) collagen carboxyl terminus was found to be in the propeptide region at Leu-1248-Ser-1249. Cleavage at this site suggested that the collagen products would form fibrils and confirmed the production of a unique carboxyl-terminal propeptide. Turbidometric fibril formation assay demonstrated de novo formation of chymase-generated collagen fibrils with characteristic lag, growth, and plateau phases. When observed by dark field microscopy, these fibrils were similar to fibrils formed by the action of procollagen proteinases. Thus, mast cell chymase, but not tryptase, exhibits procollagen peptidase-like activity as evidenced by its ability to process procollagen to fibril-forming collagen with concurrent formation of a unique carboxyl-terminal propeptide. These data demonstrate that mast cell chymase has a potential role in the regulation of collagen biosynthesis and in the pathogenesis of fibrosis.

Corticosteroids increase procollagen gene expression, synthesis, and secretion by human intestinal smooth muscle cells

BACKGROUND & AIMS

Collagen synthesis by smooth muscle cells plays an important role in intestinal fibrosis. Corticosteroids inhibit collagen synthesis in fibroblasts. The aim of this study was to examine the effect of corticosteroids on the expression of collagen by human intestinal smooth muscle (HISM) cells in vitro.

METHODS

Collagen synthesis was determined by the sensitivity of radiolabeled protein to collagenase. Secretion was determined by polyacrylamide gel electrophoresis of radiolabeled procollagen in the medium. Procollagen messenger RNA was determined by Northern blot analysis.

RESULTS

Collagen synthesis by confluent HISM cells was not affected by corticosteroids at 10(-10) to 10(-5) mol/L but, in subconfluent cultures, was nonspecifically increased 50% at 10(-5) mol/L. Procollagen secretion was nonspecifically increased 60% at 10(-6) mol/L dexamethasone without any effect on the type III/I ratio. Procollagen I and III messenger RNA levels responded in a biphasic manner: a 45%-65% increase at 10(-10) mol/L and a 15% and 30% decrease at 10(-8) and 10(-6) mol/L. In fibroblasts, collagen synthesis was inhibited 85% by dexamethasone, procollagen secretion was decreased 70%, the type III/I ratio decreased from 70:1 to 18:1, and procollagen messenger RNA was inhibited 25% and 60% (types I and III).

CONCLUSIONS

Collagen expression by HISM cells is refractory to corticosteroids and, at certain concentrations, is augmented.