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PubMed1989

Rat mesangial cell-matrix interactions in culture.

The glomerular mesangium contains fibronectin (FN), laminin, and collagen IV, but it remains unclear whether these matrix proteins affect mesangial cellular functions. The present experiments were designed to test whether cell-matrix interactions could affect some functions of mesangial cells. Cultured rat mesangial cells synthesized a cellular form of FN that was both secreted and incorporated into an extensive, fibrillar pericellular matrix. This FN matrix was increased in high-density cultures and was more developed in human mesangial cells. Rat mesangial cells in vitro displayed a marked capacity to incorporate exogenous FN into a pericellular matrix, demonstrating that accumulations of FN in the mesangial matrix could result from endogenous and/or exogenous sources. Rat mesangial cells also expressed RGD-sensitive integrin receptors for FN, laminin, and collagens I and IV that promoted cell adhesion and that directed differential changes in morphology. Indirect evidence suggested the existence of other mesangial binding sites for extracellular matrix proteins. FN and collagen IV also stimulated modest increases in [3H]thymidine uptake and cell number by quiescent cells. Taken together, these results suggest that cultured mesangial cells present a model system for studying the regulation of cell-matrix interactions in the mesangium.

Animals↗
PubMed1992

The effect of in vitro heat exposure on the recovery of nuclear matrix-bound DNA polymerase alpha activity during the different phases of the cell cycle in synchronized HeLa S3 cells.

HeLa S3 cells were synchronized by a double thymidine block or aphidicolin treatment and the levels of nuclear matrix-bound DNA polymerase alpha activity were then measured using activated calf thymus DNA as template. The nuclear matrix was obtained by 2 M NaCl extraction and DNase I digestion of isolated nuclei incubated at 37 degrees C for 45 min prior to subfractionation. In all phases of the cell cycle 25-30% of nuclear DNA polymerase alpha activity remained matrix-bound, even when cells were in the G1 phase. No dynamic association of DNA polymerase alpha activity with the matrix was seen, at variance with previous results obtained in regenerating rat liver. The variations measured in matrix-bound activity closely followed those detected in isolated nuclei throughout the cell cycle. If nuclei were not heat-stabilized very low levels of DNA polymerase alpha activity were measured in the matrix (1-2% of total nuclear activity). Heat incubation of nuclei failed to produce any enrichment in matrix-associated newly replicated DNA, whereas the sulfhydryl cross-linking chemical sodium tetrathionate did. Therefore the results obtained after the heat stabilization procedure do not completely fit with the model that envisions the nuclear matrix as the active site where eucaryotic DNA replication takes place.

Aphidicolin↗
PubMed1992

Matrix vesicles contain metalloproteinases that degrade proteoglycans.

This study explored whether extracellular matrix processing enzymes are present in matrix vesicles produced by rat costochondral resting zone and growth zone chondrocytes in culture. It was found that there was a differential distribution of enzyme activities related to the cartilage zone from which the cells were isolated. There was a 3-fold enrichment of total and active acid metalloproteinase in growth zone chondrocyte (GC) matrix vesicles whereas no enrichment in enzyme activity was observed in resting zone chondrocyte (RC) matrix vesicles. Total and active neutral metalloproteinase were similarly enriched 2-fold in GC matrix vesicles. TIMP, plasminogen activator and beta-glucuronidase activities were highest in the plasma membranes of both cell types. No collagenase, lysozyme, or hyaluronidase activity was found. The data indicate that matrix vesicles are selectively enriched in enzymes that degrade proteoglycans. The highest concentrations of these enzymes are found in matrix vesicles produced by growth zone chondrocytes, suggesting that this may be a mechanism by which the more differentiated cell modulates the matrix for calcification.

Animals↗
PubMed1990

Defective generalized extracellular matrix in the neoplasm bearing host: decreased inflammation, immunity and resistance.

Neoplasms have extensive qualitative and quantitative changes in their extracellular matrix. Lytic factors from neoplasms breakdown extracellular matrix of the areas adjacent to the neoplasms and fibroblasts in these areas produce increased extracellular matrix. Some of the extracellular matrix fractions are normally present in serum. Multiple fractions derived from extracellular matrix are present in the serum of tumor patients. Tumor patients often have decreased early cellular inflammation and immunity. These reactions depend on a normal extracellular matrix. A number of known facts about the tumor bearing host can be explained by the concept that the host's generalized extracellular matrix is altered by circulating fractions of extracellular matrix. These could be qualitative or quantitative defects as well as an abundance of depolymerized fractions. The beneficial effects of cytokines, streptococcal infections and pyridoxine deficiency on tumors can be explained by this concept.

Animals↗
PubMed2006

Integrin-linked kinase is involved in matrix-induced hepatocyte differentiation.

Hepatocytes have restricted proliferative capacity in culture and when cultured without matrix, lose the hepatocyte-specific gene expression and characteristic cellular micro-architecture. Overlay of matrix-preparations on de-differentiated hepatocytes restores differentiation. Integrin-linked kinase (ILK) is a cell-matrix-adhesion protein crucial in fundamental processes such as differentiation and survival. In this study, we investigated the role of ILK, and its binding partners PINCH, alpha-parvin, and Mig-2 in matrix-induced hepatocyte differentiation. We report here that ILK is present in the liver and localizes at cell-matrix adhesions of cultured hepatocytes. We also show that ILK, PINCH, alpha-parvin, and Mig-2 expression level is dramatically reduced in the re-differentiated hepatocytes. Interestingly, hepatocytes lacking ILK undergo matrix-induced differentiation but their differentiation is incomplete, as judged by monitoring cell morphology and production of albumin. Our results show that ILK and cell-matrix adhesion proteins play an important role in the process of matrix-induced hepatocyte differentiation.

Animals↗
PubMed2005

Mollusk shell formation: mapping the distribution of organic matrix components underlying a single aragonitic tablet in nacre.

Control over mineral formation in mollusk shells is exerted by the macromolecules of the organic matrix. Using histochemical methods, we mapped the carboxylates and sulfates of proteins and polysaccharides on the surfaces of decalcified interlamellar matrices from the nacreous shell layer of the cephalopod Nautilus pompilius, expanding upon an earlier study by Crenshaw and Ristedt [Crenshaw, M.A., Ristedt, H., 1976. The histochemical localization of reactive groups in septal nacre from Nautilus pompilius. In: Watabe, N., Wilbur, K.M. (Ed.), The Mechanisms of Mineralization in the Invertebrates and Plants. University of South Carolina Press, Colombia, pp. 355-367]. We observed four different zones underlying a single crystal: (1) a central spot rich in carboxylates; (2) a central ring-shaped area rich in sulfates; (3) an area between the central nucleation region and the imprint periphery containing carboxylates, and (4) the intertabular matrix, rich in carboxylates and sulfates. We also mapped matrix functional groups on the nacreous matrix surfaces of the bivalve Atrina rigida, but did not identify well-defined zones. Immuno-mapping of the constituents of the aragonite-nucleating protein fraction from Atrina nacre showed that these macromolecules are located both in the intertabular matrix and in the center of the crystal imprints for both Atrina and Nautilus matrix surfaces. Their presence at the latter location is consistent with their purported role in aragonite nucleation. The observed differentiation in the distribution of matrix components and their functional groups shows that the different stages of single crystal growth are highly controlled by the matrix.

Animals↗
PubMed2004

Normal matrix mineralization induced by strontium ranelate in MC3T3-E1 osteogenic cells.

There is growing evidence that strontium ranelate (SR; S12911-2, PROTELOS; Institut de Recherches Internationales Servier, Courbevoie, France), a compound containing 2 atoms of stable strontium (Sr), influences bone cells and bone metabolism in vitro and in vivo. We previously reported that SR increases bone mass in rats and mice by stimulating bone formation and inhibiting bone resorption. We also showed that short-term treatment with SR enhances osteoblastic cell recruitment and function in short-term rat calvaria cultures. Because Sr incorporates into the bone matrix, it was of interest to determine whether SR may affect matrix mineralization in long-term culture. To this goal, osteogenic mouse calvaria-derived MC3T3-E1 osteoblastic cells were cultured for up to 14 days in the presence of ascorbic acid and phosphate to induce matrix formation and mineralization. Matrix formation was determined by incorporation of tritiated proline during collagen synthesis. Matrix mineralization was quantified by measuring the number and surface of mineralized nodules using a digital image analyzer. In this model, 1,25(OH)2 vitamin D (1 nmol/L) used as internal control, increased alkaline phosphatase (ALP) activity, an early osteoblast marker, on days 4, 10, and 14 of culture. Treatment with SR (1 mmol/L Sr(2+)) increased ALP activity at days 4 and 14 of culture. SR also increased collagen synthesis at days 4 and 10 of culture. In contrast, 1,25(OH)2 vitamin D (1 nmol/L) inhibited collagen synthesis at 4 to 14 days of culture. Long-term treatment with SR (0.1 to 1 mmol/L Sr(2+)) dose dependently increased Sr concentration into the calcified nodules, but did not alter matrix mineralization in long-term culture, as shown by the ratio of the surface of mineralized nodules to the number of mineralized nodules on day 14 of culture. These results show that long-term treatment with SR increases collagenous matrix formation by MC3T3-E1 osteoblasts without inducing deleterious effect on matrix mineralization.

Alkaline Phosphatase↗
PubMed2004

Bisphosphonate treatment affects trabecular bone apparent modulus through micro-architecture rather than matrix properties.

Bisphosphonates are emerging as an important treatment for osteoporosis. But whether the reduced fracture risk associated with bisphosphonate treatment is due to increased bone mass, improved trabecular architecture and/or increased secondary mineralization of the calcified matrix remains unclear. We examined the effects of bisphosphonates on both the trabecular architecture and matrix properties of canine trabecular bone. Thirty-six beagles were divided into a control group and two treatment groups, one receiving risedronate and the other alendronate at 5-6 times the clinical dose for osteoporosis treatment. After one year, the dogs were killed, and samples from the first lumbar vertebrae were examined using a combination of micro-computed tomography, finite element modeling, and mechanical testing. By combining these methods, we examined the treatment effects on the calcified matrix and trabecular architecture independently. Conventional histomorphometry and microdamage data were obtained from the second and third lumbar vertebrae of the same dogs [Bone 28 (2001) 524]. Bisphosphonate treatment resulted in an increased apparent Young's modulus, decreased bone turnover, increased calcified matrix density, and increased microdamage. We could not detect any change in the effective Young's modulus of the calcified matrix in the bisphosphonate treated groups. The observed increase in apparent Young's modulus was due to increased bone mass and altered trabecular architecture rather than changes in the calcified matrix modulus. We hypothesize that the expected increase in the Young's modulus of the calcified matrix due to the increased calcified matrix density was counteracted by the accumulation of microdamage.

Alendronate↗
PubMed1996

Increased matrix metalloproteinase activity and reduced tissue inhibitor of metalloproteinases-1 levels in amniotic fluids from pregnancies complicated by premature rupture of membranes.

OBJECTIVES: It has been suggested that increased matrix metalloproteinases activity promotes the weakening of the amniochorion during normal and premature rupture of membranes. This study was designed to determine whether levels of matrix metalloproteinases and the tissue inhibitor of metalloproteinases-1 in amniotic fluid change in a pattern consistent with this hypothesis. STUDY DESIGN: Gelatinolytic activity, measured by a soluble substrate assay and zymography, and the concentrations of tissue inhibitor of metalloproteinases-1 were estimated in amniotic fluid obtained from (1) normal early gestations, (2) normal term pregnancies with labor, (3) normal term pregnancies without labor, and (4) pregnancies complicated by premature rupture of membranes. The 92 kd type IV collagenase (matrix metalloproteinase-9) was also detected in amniotic fluid by Western blotting. RESULTS: Matrix metalloproteinase activities were higher in amniotic fluid from normal term pregnancies with labor and pregnancies complicated by premature rupture of membranes than from early pregnancies and term gestations without labor. The amniotic fluid from term pregnancies with labor or pregnancies with premature rupture of membranes contained several gelatinases, as revealed by zymography. The major amniotic fluid gelatinolytic activity in premature rupture of membranes and term pregnancies with labor corresponded to matrix metalloproteinase-9. Tissue inhibitor of metalloproteinases-1 concentrations were highest in early-pregnancy amniotic fluid, followed by term gestation with labor, term gestation without labor, and premature rupture of membranes. CONCLUSIONS: Normal labor and premature rupture of membranes are associated with increased levels of matrix metalloproteinases, particularly matrix metalloproteinase-9 in amniotic fluid. Premature rupture of membranes is associated with reduced levels of tissue inhibitor of metalloproteinases-1. The imbalance between matrix metalloproteinases and tissue inhibitor of metalloproteinases-1 in amniotic fluid may reflect a disorder that promotes premature rupture of membranes.

Amniotic Fluid↗
PubMed1997

Expression of interstitial collagenase (matrix metalloproteinase-1) is related to the activity of human endometriotic lesions.

OBJECTIVE: To determine whether interstitial collagenase (matrix metalloproteinase-1), known to play a pivotal role in the initiation of menstruation, contributes to the pathogenesis of endometriosis. DESIGN: Serial sections of peritoneal red and black endometriotic lesions, ovarian endometriotic cysts, and rectovaginal adenomyotic nodules were analyzed by in situ hybridization for the expression of matrix metalloproteinase-1 by silver staining for the integrity of the fibrillar extracellular matrix and by immunolabeling for the abundance of sex steroid receptors. SETTING: Academic hospital and research laboratory. PATIENT(S): Premenopausal women undergoing laparoscopy for endometriosis. INTERVENTION(S): Biopsy of endometriotic lesions, combined with endometrium whenever possible. MAIN OUTCOME MEASURE(S): Expression of matrix metalloproteinase-1 messenger RNA (mRNA). RESULT(S): Matrix metalloproteinase-1 mRNA was expressed focally in red peritoneal and ovarian endometriosis irrespective of the phase of the menstrual cycle but was not detectable in black peritoneal and rectovaginal lesions. Foci of matrix metalloproteinase-1 expression closely correlated with matrix breakdown and with the absence of P receptors in adjacent epithelial cells. CONCLUSION(S): Correlation of matrix metalloproteinase-1 expression with activity of endometriotic tissue suggests its involvement in tissue remodeling and bleeding, and possibly in the secondary shedding and reimplantation of endometriotic lesions.

Adult↗
PubMed1999

Amniotic fluid matrix metalloproteinase-9 levels in women with preterm labor and suspected intra-amniotic infection.

OBJECTIVE: To determine the accuracy of amniotic fluid (AF) matrix metalloproteinase-9 measurements for diagnosing intra-amniotic infection in women with preterm labor. METHODS: We performed amniocenteses in 44 women between 22 and 35 weeks' gestation who presented to our center with preterm labor and clinical suspicion of intra-amniotic infection. Each sample was analyzed by glucose measurement, Gram stain, and culture for aerobes, anaerobes, and mycoplasmas. We tested the AF for matrix metalloproteinase-9 using gelatin zymography and a commercial enzyme-linked immunosorbent assay (ELISA) system. We calculated accuracy and confidence intervals (CIs) for AF matrix metalloproteinase-9, glucose, and Gram stain for diagnosing intra-amniotic infection, using culture as the criterion standard. RESULTS: All patients who had matrix metalloproteinase-9 detectable by ELISA also demonstrated matrix metalloproteinase-9 by zymography. Six cases of intra-amniotic infection were confirmed by culture (prevalence 14%). The performance statistics of AF matrix metalloproteinase-9 for diagnosing intra-amniotic infection were: sensitivity 83% (95% CI 53, 99), specificity 95% (95% CI 88, 99), positive predictive value 71% (95% CI 37, 99), and negative predictive value 97% (95% CI 92, 99). Two women had false-positive results; one had gram-negative rods on the AF Gram stain and developed clinical signs and symptoms of chorioamnionitis several hours after amniocentesis and the other had a purulent vaginal discharge and an AF glucose level less than 15 mg/dL. Both delivered within 24 hours of amniocentesis. CONCLUSION: Measuring matrix metalloproteinase-9 in the AF appeared to be reliable for diagnosing intra-amniotic infection. An elevated matrix metalloproteinase-9 concentration in the AF at a preterm gestational age may portend imminent delivery regardless of microbiologic confirmation of intra-amniotic infection.

Adult↗
PubMed1995

The nuclear matrix: a structural milieu for genomic function.

While significant progress has been made in elucidating molecular properties of specific genes and their regulation, our understanding of how the whole genome is coordinated has lagged behind. To understand how the genome functions as a coordinated whole, we must understand how the nucleus is put together and functions as a whole. An important step in that direction occurred with the isolation and characterization of the nuclear matrix. Aside from the plethora of functional properties associated with these isolated nuclear structures, they have enabled the first direct examination and molecular cloning of specific nuclear matrix proteins. The isolated nuclear matrix can be used for providing an in vitro model for understanding nuclear matrix organization in whole cells. Recent development of high-resolution and three-dimensional approaches for visualizing domains of genomic organization and function in situ has provided corroborative evidence for the nuclear matrix as the site of organization for replication, transcription, and post-transcriptional processing. As more is learned about these in situ functional sites, appropriate experiments could be designed to test molecular mechanisms with the in vitro nuclear matrix systems. This is illustrated in this chapter by the studies of nuclear matrix-associated DNA replication which have evolved from biochemical studies of in vitro nuclear matrix systems toward three-dimensional computer image analysis of replication sites for individual genes.

Animals↗
PubMed1999

Modification of surfaces with cell adhesion peptides alters extracellular matrix deposition.

The goal of the current study was to evaluate matrix protein synthesis by cells cultured on materials that had been modified with cell adhesion ligands. We examined the effects of surface peptide density and of peptides with different affinities on the extracellular matrix production of smooth muscle cells, endothelial cells and fibroblasts. While initial adhesion was greatest on the higher density peptide surfaces, all cell types exhibited decreased matrix production on the more highly adhesive surfaces. Similarly, when different peptides were evaluated, matrix production was the lowest on the most adhesive surface and highest on the least adhesive surface. These results suggest that extracellular matrix synthesis may be regulated, to some extent, by signal transduction initiated by adhesion events. This may pose limitations for use of bioactive materials as tissue engineering scaffolds, as matrix production is an important aspect of tissue formation. However, it may be possible to increase matrix production on highly adhesive surfaces using exogenous factors. TGF-beta was shown to increase matrix production by both smooth muscle cells and endothelial cells.

Animals↗
PubMed1998

Dedifferentiation of human hepatocytes by extracellular matrix proteins in vitro: quantitative and qualitative investigation of cytokeratin 7, 8, 18, 19 and vimentin filaments.

BACKGROUND/AIMS: Liver cirrhosis and carcinogenesis are accompanied by an alteration in extracellular matrix material. Histological studies reveal upregulation of the intermediate filaments cytokeratins 8 and 18 and de novo synthesis of vimentin, and cytokeratin 7 or 19 in hepatocytes. The aim of this study was to investigate how these two processes are linked. METHODS: Human hepatocytes were seeded: (i) on the matrix components collagen I, IV, laminin, or fibronectin; (ii) on stoichiometrically different complete matrices, derived from human placenta (matrix I) or the Englebreth-Holm-Swarm tumor (matrix II), and (iii) inside a three-dimensional collagen I sandwich. Filament expression and assembly were measured by cytofluor analysis or confocal laserscan microscopy. RESULTS: The matrix components or complete matrices triggered enhancement of cytokeratins 8 and 18 and de novo synthesis of cytokeratins 7, 19 and vimentin in a characteristic way. Confocal images demonstrated a dense and uniform network of cytokeratin 18 in freshly isolated cells, which was "replaced" by a few, thick protein bundles within 20 days. Interestingly, newly synthesized cytokeratin 19 structurally resembled the cytokeratin 19 organization in biliary epithelial cells. Marked cytokeratin alterations could be partially prevented when hepatocytes were grown in a three-dimensional collagen sandwich. CONCLUSIONS: Pathological alterations to the chemical composition, molecular structure, or spatial arrangement of the liver matrix lead to specific changes in the intermediate filament pattern in human hepatocytes. We assume that degradation of the matrix results in pathological alterations to the hepatocyte-receptor matrix-ligand ratio, followed by a switch from physiological to pathological cell-activation.

Cell Count↗
PubMed2004

Microdeposition device interfacing capillary electrochromatography and microcolumn liquid chromatography with matrix-assisted laser desorption/ionization mass spectrometry.

A sample deposition device has been constructed and optimized for interfacing CEC and capillary LC columns to MALDI mass spectrometry. For CEC analysis, the device is composed of an inlet buffer reservoir and an outlet buffer reservoir connected to a matrix reservoir through a connection sleeve. The matrix reservoir is connected to a deposition capillary via another connection sleeve. CEC eluent is transported to the matrix reservoir via a capillary that is connected to the deposition capillary by the connection sleeve inside the matrix reservoir. This connection sleeve also acts as a mixing chamber, allowing the CEC eluent to be mixed with matrix prior to deposition. Complex glycan mixtures can be separated by CEC using hydrophilic-phase monolithic columns, with capillary eluent being deposited on a standard MALDI plate along with a suitable matrix solution. Thousands of discrete, highly homogeneous dots can be generated for a subsequent mass spectrometric analysis. With minor modifications, this device is also applicable to capillary LC of peptides using gradient elution. In this configuration, the outlet of the LC column is connected to a deposition capillary inside a matrix reservoir through a connection sleeve that allows mixing of the LC effluent with an appropriate matrix. The device has been evaluated with the tryptic digests of proteins.

Chromatography, Liquid↗
PubMed1993

Specificity in the interactions of extracellular matrix proteins with subpopulations of the glycosaminoglycan heparin.

Many extracellular matrix glycoproteins--including laminin, fibronectin, thrombospondin, type I collagen, and other collagens--bind the glycosaminoglycan heparin, yet little is known about the functional significance of these interactions. It is also not known if heparin-binding extracellular matrix proteins recognize distinct structural elements in heparin, nor whether all extracellular matrix proteins recognize the same or different aspects of heparin structure. If extracellular matrix proteins each recognize distinct features of heparin, such specificity could be of importance in vivo, where structurally distinct heparan sulfate species occur. To investigate specificity in the binding between extracellular matrix proteins and heparin, the method of affinity coelectrophoresis (ACE) was used [Lee, M. K., & Lander, A. D. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 2768-2772]. Low M(r) (approximately 6 kDa) 125I-heparin was fractionated by electrophoresis through agarose gel lanes containing extracellular matrix proteins at various concentrations; from heparin migration patterns, binding affinities were calculated. The results indicate that fibronectin, type I collagen, and laminin--but not thrombospondin--each fractionate heparin into subpopulations that differ substantially in binding affinity. From ACE gels containing either fibronectin, type I collagen, or laminin, fractions of heparin were isolated that represent the 25% of molecules most strongly bound and the 25% least strongly bound by each of these proteins. Subsequent ACE analysis of these six fractions showed that (1) for each of fibronectin, type I collagen, and laminin, strongly- and weakly-binding heparin subfractions differ approximately 5-30-fold in Kd; (2) heparin that binds strongly to any one of fibronectin, type I collagen, or laminin also binds strongly to the other two; (3) heparin that binds weakly to any one of fibronectin, type I collagen, or laminin, also binds weakly to the other two; (4) heparin subfractions that differ greatly in affinity for fibronectin, type I collagen, and laminin show little difference in Kd for thrombospondin or for the heparin-binding growth factor basic fibroblast growth factor (bFGF); (5) neither heterogeneity in molecular charge [as measured by diethylaminoethyl (DEAE) chromatography] nor size nor the presence or absence of antithrombin III recognition sequences can account for the selective binding of heparin subpopulations to fibronectin, type I collagen, and laminin. These results suggest that structural elements within heparin can confer preferential binding to extracellular matrix proteins. Sensitivity of some, but not all, extracellular matrix proteins to these structural features suggests that similar features, if present in heparan sulfates or other glycosaminoglycans, may be physiologically relevant in vivo.

Antithrombin III↗
PubMed2006

Recombinant protein-co-PEG networks as cell-adhesive and proteolytically degradable hydrogel matrixes. Part II: biofunctional characteristics.

We present here the biological performance in supporting tissue regeneration of hybrid hydrogels consisting of genetically engineered protein polymers that carry specific features of the natural extracellular matrix, cross-linked with reactive poly(ethylene glycol) (PEG). Specifically, the protein polymers contain the cell adhesion motif RGD, which mediates integrin receptor binding, and degradation sites for plasmin and matrix-metalloproteinases, both being proteases implicated in natural matrix remodeling. Biochemical assays as well as in vitro cell culture experiments confirmed the ability of these protein-PEG hydrogels to promote specific cellular adhesion and to exhibit degradability by the target enzymes. Cell culture experiments demonstrated that proteolytic sensitivity and suitable mechanical properties were critical for three-dimensional cell migration inside these synthetic matrixes. In vivo, protein-PEG matrixes were tested as a carrier of bone morphogenetic protein (rhBMP-2) to heal critical-sized defects in a rat calvarial defect model. The results underscore the importance of fine-tuning material properties of provisional therapeutic matrixes to induce cellular responses conducive to tissue repair. In particular, a lack of rhBMP or insufficient degradability of the protein-PEG matrix prevented healing of bone defects or remodeling and replacement of the artificial matrix. This work confirms the feasibility of attaining desired biological responses in vivo by engineering material properties through the design of single components at the molecular level. The combination of polymer science and recombinant DNA technology emerges as a powerful tool for the development of novel biomaterials.

Amino Acid Sequence↗
PubMed2002

Collagen type 1 retards tube formation by human microvascular endothelial cells in a fibrin matrix.

Angiogenesis, or the formation of new microvessels, is often encountered in pathological situations. A fibrinous exudate can often act as a temporary matrix for the ingrowth of these new microvessels. This matrix consists mainly of fibrin, but is mingled with other plasma components and interstitial collagen fibres. In vitro, capillary-like tube formation can be mimicked by exposing human microvascular endothelial cells (hMVECs), seeded on top of a three-dimensional fibrin matrix, to an angiogenic growth factor (e.g. fibroblast growth factor (FGF)-2) and the cytokine tumour necrosis factor (TNF)-alpha. Plasmin activity is required in this process. We investigated whether the angiogenic potential of hMVECs was altered by the presence of collagen. The addition of type I collagen to fibrin matrices dose-dependently inhibited tube-formation. Tube-formation in these fibrin/collagen matrices by hMVECs required matrix metalloprotease (MMP) activity, as well as plasmin activity. On a pure collagen type I matrix, hMVECs were not able to form tube-like structures in the matrix but formed sprouts. This sprouting required MMP activity and was, in contrast to the tube-like structures in a fibrin matrix, not influenced by hypoxia. These data indicate that the interaction between endothelial cells and different matrix components is of importance for the angiogenic potential of these cells.

Cell Culture Techniques↗