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PubMed1997

Transforming growth factor-beta receptor and fibronectin expressions in aortic smooth muscle cells in diabetic rats.

Smooth muscle cells in arteries of diabetic rats and rabbits have unique properties including the overexpression of platelet-derived growth factor (PDGF) beta-receptor compared with controls. Fibronectin, one of the increased components of extra-cellular matrices in diabetic arteries, plays an important role in the phenotypic change of smooth muscle cells from the contractile to the synthetic type with the expression of the PDGF beta-receptor. Moreover, fibronectin synthesis is regulated by transforming growth factor-beta (TGF-beta). In this study, we report on the expression of TGF-beta receptors in diabetic smooth muscle cells, by immunohistochemistry, cross-linking of 125I-TGF-beta 1 to cells and quantitative reverse transcription-polymerase chain reaction. We also report on the effects of TGF-beta 1 on fibronectin synthesis of diabetic smooth muscle cells by use of ELISA and immunoprecipitation, in order to clarify the role of TGF-beta-fibronectin pathway in forming characteristic changes of diabetic smooth muscle cells. Cultured aortic smooth muscle cells of diabetic rats expressed TGF-beta type II receptor about 8.7 times that of controls at the protein level and 5.7 times at the mRNA level, whereas the expression of the type I receptor did not differ between the two types of smooth muscle cells. These changes were accompanied by increased fibronectin synthesis in diabetic smooth muscle cells in response to TGF-beta 1. Furthermore, protein expression of fibronectin, and mRNA and protein of TGF-beta type II receptor were increased in the diabetic aorta compared with the control aorta in vivo, implying the importance of the TGF-beta-fibronectin pathway for the unique biology of smooth muscle cells in the diabetic artery.

Analysis of Variance↗
PubMed1961

The photoactivated relaxation of smooth muscle of rabbit aorta.

Smooth muscle of strips of rabbit aorta, placed in a state of active tonic contraction by addition of a stimulating drug, relaxes during exposure to light. The relaxation is reversible. The extent of relaxation produced by a standard exposure depends on the preexposure level of active contraction but not on the nature of the stimulating drug used to produce contraction. With strips brought to an intermediate level of contraction, the degree of relaxation (steady state levels) is a rectangular hyperbolic function of radiation intensity. The kinetics of the relaxation process during irradiation and the recovery process following irradiation are consistent with the hypothesis that the primary photoactivated material initiates a reaction or reactions leading to a product which inhibits some process involved in the production of active contraction. The photorelaxation does not require the presence of oxygen. It is potentiated by reducing the temperature of the aortic strip. The action spectrum of the photorelaxation shows relatively low effectiveness at wavelengths above 450 mmicro. The effectiveness increases markedly and progressively as the wavelength is lowered below 450 mmicro, reaching a peak at 310 mmicro. A deep trough occurs at 280 mmicro. However, both peak and trough probably result from internal filtering due to absorption by proteins in the aortic strip. It is surmised that if a correction could be made for this internal filtering, the action spectrum would rise continuously down to wavelengths at least as low as 250 mmicro.

Animals↗
PubMed2002

Endothelin receptors in cultured and native human radial artery smooth muscle.

In human vascular smooth muscle cells endothelin-1, acting at both endothelin A and endothelin B receptors, has been demonstrated to be both a potent vasoconstrictor and mitogen. Our aim was to study the functional expression of endothelin receptors in human radial artery smooth muscle using both native tissue and cultured cells (RASMCs). Radial artery smooth muscle cells were cultured from arterial explants and loaded with the calcium fluorescent dye fura-2. Cells responded to endothelin-1 and a variety of other vasoconstrictors with rises in cytoplasmic calcium ([Ca2+]c). Arterial rings responded to endothelin-1 with an increase in tension. The response of both cells and arterial rings to endothelin-1 was characterized using the selective endothelin A receptor antagonist BQ123 and the endothelin B receptor antagonist BQ788. The RASMCs were found to express [Ca2+]c responses consistent with the expression of only the endothelin A receptor. Endothelin-1-mediated vasoconstriction in radial artery rings was unaffected by BQ788 but was completely blocked by BQ123. Using the selective radioligands [125I]-PD151242 and [125I]-BQ3020 and a combination of in vitro receptor autoradiography and isolated cell preparations, endothelin A receptors were confirmed to be present on RASMCs and on arterial sections, whereas endothelin B binding was barely detectable on native smooth muscle and on RASMCs.

Autoradiography↗
PubMed1994

Calcium and smooth muscle contraction.

The fact that smooth muscle exists in almost every hollow organ and is involved in a large number of disease states has led to a vast increase in smooth muscle research, covering areas from testing response to antagonists and agonists to measuring the molecular force generated by a single actin filament. Yet, the exact mechanisms regulating contractile response of smooth muscle remain unsolved. Calcium has been a central player in mediating smooth muscle contraction through binding with calmodulin, although there is evidence showing that under special circumstances smooth muscle can contract without change in intracellular Ca2+. In addition to the major regulatory pathway of Ca(2+)-calmodulin-myosin light chain kinase, there are other thin filament linked regulatory mechanisms in which Ca(2+)-calmodulin dependent phosphorylation of calponin and caldesmon may be involved. Ca2+ sensitivity of smooth muscle contraction may vary under different situations and this has recently been recognized as an important regulatory mechanism. Examples are protein kinase C (PKC) dependent phosphorylation of myosin light chain kinase which results in partial inhibition of contraction, and activation of myosin light chain phosphatase. There is new evidence showing that not only does Ca2+ regulate contraction by regulating the interaction of contractile proteins in smooth muscle, but also that shortening of smooth muscle itself reduces intracellular Ca2+ concentration, via a negative feedback.

Actins↗
PubMed1993

Relation between alpha 1-adrenoceptor subtypes and noradrenaline-induced contraction in rat portal vein smooth muscle.

1. In vascular smooth muscle, alpha 1-adrenoceptors have been classified recently into two or three subtypes. We examined which alpha 1-adrenoceptor subtypes are involved in the noradrenaline-induced contraction of rat portal vein smooth muscle. 2. Binding studies with [3H]-prazosin in membranes from equine portal vein smooth muscle revealed the presence of two distinct affinity binding sites. The high-affinity site for [3H]-prazosin was also identified in intact strips of rat portal vein. Prazosin, HV723 (alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)ethyl)-amin o)- propyl) benzene-acetonitrile fumarate), WB4101 (2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane), 5-methylurapidil, phentolamine and yohimbine antagonized [3H]-prazosin binding at both types of sites. Pretreatment with 50 microM chloroethylclonidine (CEC) eliminated the high-affinity sites for prazosin but had no effect on the low-affinity sites. 3. Noradrenaline produced a concentration-dependent contraction in the rat portal vein. Pretreatment with 50 microM CEC induced a slight rightward displacement of the concentration-response curve but the maximal contraction was not significantly affected suggesting that the CEC-sensitive alpha 1-adrenoceptors played a minor role in the noradrenaline-induced contraction. Prazosin, WB4101 and HV723 produced a concentration-dependent inhibition of noradrenaline-induced contractions. The inhibition curves were little affected by CEC-pretreatment and yielded a relative order of potency of WB4101 > prazosin > HV723. 4. In the presence of 0.1 microM isradipine to block voltage-dependent Ca2+ channels, the noradrenaline-induced contraction is due to release of Ca2+ ions from agonist-sensitive intracellular Ca2+ stores. Under these conditions, the noradrenaline-induced contraction was not significantly affected by pretreatment with 50 microM CEC but was inhibited by the antagonists mentioned above with affinities different from those in the absence of isradipine. The rank order of potency became HV723 > WB4101 > prazosin.5. The present results indicate the existence of two distinct o1-adrenoceptor subtypes in rat portal vein smooth muscle, which show high- and low-affinities respectively for each of prazosin, WB4101 andHV723 and correspond to alphalH- and alphalL-adrenoceptor subtypes. According to recent alpha1-adrenoceptor subclassifications, the alpha l H-adrenoceptor subtype which is sensitive to inactivation by CEC may correspond to the alpha1B-adrenoceptor subtype. The contraction induced by noradrenaline seems to be predominantly mediated through the alphalL-adrenoceptor subtypes which may include the alpha1N-adrenoceptor subtype, as recently proposed.

Acetonitriles↗
PubMed1999

A mechanosensitive calcium channel in human intestinal smooth muscle cells.

BACKGROUND & AIMS: Gastrointestinal smooth muscle strips devoid of enteric nerve cells can contract in response to stretch, suggesting that mechanosensitivity and mechanotransduction can occur at the level of the smooth muscle cell. The aim of this study was to determine whether stretch-activated calcium channels are present in gastrointestinal smooth muscle cells. METHODS: Whole-cell and single-channel calcium currents were measured from human jejunal circular smooth muscle cells in response to increased intracellular pressure, bath perfusion, and membrane stretch. RESULTS: At 10 mm Hg positive pressure, peak calcium current increased from -36 +/- 10 pA to -53 +/- 13 pA. Bath perfusion at 10 mL/min increased calcium current from -97.7 +/- 14 pA to -122 +/- 16 pA. Single-channel open probability increased in response to negative pipette pressure. All increases were blocked by nifedipine. CONCLUSIONS: A stretch-activated, nifedipine-sensitive calcium channel is present in human jejunal circular smooth muscle cells. The channel is activated by both an increase in intracellular pressure and by external shear forces. The presence of a stretch-activated calcium channel in gastrointestinal smooth muscle cells may allow the smooth muscle cells to act directly as mechanotransducers and to participate in the regulation of smooth muscle tone and intestinal motility.

Calcium Channels↗
PubMed1990

Endothelial heparan sulfate proteoglycan. I. Inhibitory effects on smooth muscle cell proliferation.

Proliferation of smooth muscle cells is an important component of pulmonary arterial morphogenesis, both during normal development and pathologic remodeling. However, little is known of the factors that regulate smooth muscle proliferation in these vessels. To investigate the hypothesis that factors produced by endothelial cells may regulate smooth muscle cell growth, we studied the effects of culture medium conditioned by fetal bovine pulmonary arterial endothelium on proliferation of smooth muscle cells in culture. This conditioned medium contains an inhibitor of smooth muscle proliferation that is degraded by nitrous acid, heparinase, and heparitinase, but resists degradation by protease, boiling, and chondroitin ABC lyase, indicating that the inhibitor is structurally similar to heparin. Inhibitor release occurs in both growing and confluent endothelial cell cultures and in the presence and absence of serum. A growth-inhibiting proteoglycan purified to homogeneity from endothelial cell-conditioned medium has physicochemical characteristics similar to those of the prototypic basement membrane heparan sulfate proteoglycan of the Englebreth-Holm-Swarm tumor: an overall size of approximately 10(6) D, heparan sulfate chains of 60,000 D, and a buoyant density of 1.33 g/ml. Antibody raised against the tumor basement proteoglycan recognizes this endothelial heparan sulfate proteoglycan, and Western blotting after SDS-PAGE demonstrates that the core proteins of both proteoglycans migrate as a doublet at apparent molecular weights of 450,000 and 360,000 D. Heparan sulfate glycosaminoglycan prepared from purified medium proteoglycan is a potent inhibitor of smooth muscle cell growth, exhibiting activity approximately 1,000 times greater than that of heparin. These results indicate that endothelial cells cultured from fetal bovine pulmonary arteries produce a basement membrane heparan sulfate proteoglycan that is a potent inhibitor of smooth muscle proliferation. This proteoglycan may mediate endothelial regulation of smooth muscle growth during development or pathologic pulmonary arterial remodeling.

Animals↗
PubMed2005

Diagnosing erectile dysfunction: instruments for the study of smooth muscle relaxation.

Complete cavernosal smooth muscle relaxation is the pre-requisite for the reliability of every evaluation of the integrity of the corporal veno-occlusive system. Such evaluation is needed whenever reaching a diagnostic conclusion on the haemodynamic status of a given patient is clinically relevant. Clinical challenges that a laboratory evaluation of veno-occlusive integrity face comprise both the induction of complete smooth muscle relaxation, and the possibility to monitor it. This article will review the relevant aspects of normal range values of veno-occlusive function, existing strategies aimed to promote complete smooth muscle relaxation, and available techniques to monitor the cavernosal smooth muscle status.

Erectile Dysfunction↗
PubMed1996

Differentiated properties and proliferation of arterial smooth muscle cells in culture.

The smooth muscle cell is the sole cell type normally found in the media of mammalian arteries. In the adult, it is a terminally differentiated cell that expresses cytoskeletal marker proteins like smooth muscle alpha-actin and smooth muscle myosin heavy chains, and contracts in response to chemical and mechanical stimuli. However, it is able to revert to a proliferative and secretory active state equivalent to that seen during vasculogenesis in the fetus, and this is a prerequisite for the involvement of the smooth muscle cell in the formation of atherosclerotic and restenotic lesions. A similar transition from a contractile to a synthetic phenotype occurs when smooth muscle cells are established in culture. Accordingly, an in vitro system has been used extensively to study the regulation of differentiated properties and proliferation of these cells. During the first few days after seeding, the cells are reorganized structurally with a loss of myofilaments and formation of a widespread endoplasmic reticulum and a prominent Golgi complex. In parallel, they lose their contractility and instead become competent to divide in response to a large variety of mitogens, including platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). After entering the cell cycle, they start to produce these and other mitogens on their own, and continue to replicate in the absence of exogenous stimuli for a restricted number of generations. Furthermore, they start to secrete extracellular matrix components such as collagen, elastin, and proteoglycans. The mechanisms that control this change in morphology and function of the smooth muscle cells are still poorly understood. Adhesive proteins such as fibronectin and laminin apparently have an important role in determining the basic phenotypic state of the cells and exert their effects via integrin receptors. The proliferative and secretory activities of the cells are influenced by a multitude of growth factors, cytokines, and other molecules. Although much work remains before an integrated view of this regulatory machinery can be achieved, there is no doubt that the cell culture technique has contributed substantially to our knowledge of smooth muscle differentiation and growth. At the same time, it has been crucial in exploring the role of these cells in vascular disease and developing new therapeutic strategies to cope with major causes of human death and disability.

Animals↗
PubMed2004

Isolation of muscle derived stem cells from rat and its smooth muscle differentiation [corrected].

We investigated whether stem cells (MDSC) from primary cultures of rat skeletal muscle can differentiate into the smooth muscle lineage in response to vascular endothelial growth factor (VEGF) and coculture with bladder smooth muscle cells. The MDSC were isolated from gastrocnemius muscle biopsies of normal 3-6 week-old Sprague-Dawley rats and purified by the preplate technique. Cells that took approximately 6 days to adhere to the collagen-coated flasks were termed late preplate (LP) cells, and were used in all the experiments. The early plate (EP) cells (pp1-pp4) contained some myogenic cells but were mostly fibroblasts (< 15% desmin+ cells) whereas the LP cells (pp5-pp6) were highly purified muscle-derived cells (pp6) (> 90% desmin+ cells). The muscle-derived stem cells (LP cells) were CD34+ or Sca-1+, CD45- and desmin+ by immunohistochemical staining. After two days of co-culture with bladder smooth muscle cells, about 25% of the muscle-derived stem cells were positive for alpha-smooth muscle actin (alpha-SMA)+. RT-PCR for alpha-SMA was positive in the VEGF stimulated MDSC, but negative in the absence of VEGF. In conclusion, rat muscle-derived stem cells exhibited stem cell properties (CD34+ or Sca-1+), and were not of hematogeous (CD45-) but of myogenic origin (desmin+). RT-PCR of alpha-SMA was positive in the VEGF stimulated muscle-derived stem cells.

Actins↗
PubMed2000

Fas/FADD-mediated activation of a specific program of inflammatory gene expression in vascular smooth muscle cells.

Apoptosis of smooth muscle cells is a common feature of vascular lesions but its pathophysiological significance is not known. We demonstrate that signals initiated by regulated Fas-associated death domain protein overexpression in rat vascular smooth muscle cells in the carotid artery induce expression of monocyte-chemoattractant protein-1 and interleukin-8, and cause massive immigration of macrophages in vivo. These chemokines, and a specific set of other pro-inflammatory genes, are also upregulated in human vascular smooth muscle cells during Fas-induced apoptosis, in part through a process that requires interleukin-1alpha activation. Induction of a pro-inflammatory program by apoptotic vascular smooth muscle cells may thus contribute to the pathogenesis of vascular disease.

Adaptor Proteins, Signal Transducing↗
PubMed1989

The use of 31P-NMR to study smooth muscle.

The use of 31P NMR to study smooth muscle is hindered by low metabolite concentrations and low tissue mass. These disadvantages can be overcome due to low rates of energy utilization and the temporal stability of smooth muscle. Smooth muscle free Mg++, ADP, and the creatine analogue beta-guanidinopropionate can be studied in ways distinctive from 31P NMR of striated muscle. The pharmacological effects of naturally occurring agents such as insulin, glucose, or norepinephrine, and of NMR markers such as phenylphosphonate or 3-(trimethylsilyl)-1-propane-sulfonate on both vascular smooth muscle and perfused smooth muscles can be measured. Given sufficient collection time, 31P NMR is as useful in assessing the behavior of smooth muscle as it is of other muscle types.

Adenosine Triphosphate↗
PubMed2000

Calcium homeostasis and nerve growth factor secretion from vascular and bladder smooth muscle cells.

Bladder and vascular smooth muscle cells cultured from four rat strains (WKY, SHR, WKHA, WKHT) differing in rates of nerve growth factor (NGF) production were used to determine whether a relationship exists between intracellular calcium and NGF secretion. Basal cytosolic calcium was related to basal NGF secretion rates in bladder and vascular smooth muscle cells from all four strains with the exception of WKHT bladder muscle cells. Thrombin is a calcium-mobilizing agent and increases NGF production from vascular but not bladder smooth muscle cells. Strain differences were found in the magnitude of the calcium peak induced by thrombin in vascular smooth muscle cells, but these differences did not correlate with NGF secretion. Thrombin caused a calcium response in bladder smooth muscle cells without influencing NGF production. Quenching the calcium transient with a calcium chelator had no effect on thrombin-inducted NGF secretion rates in vascular smooth muscle cells. Thus, basal intracellular calcium may establish a set point for NGF secretion from smooth muscle. In addition, transient elevations in cytosolic calcium were unrelated to the induction of NGF output.

Animals↗
PubMed1998

Long-term effects of intracellular calcium and growth factors on excitation and contraction in smooth muscle.

Modulation of vascular smooth muscle cells from a contractile to a synthetic phenotype is thought to be important in the development of the atherosclerotic lesion. Such modulation depends on growth factors and is influenced by cell-cell and cell-matrix interactions. Whereas smooth muscle cells in the vessel wall are contractile, dispersed cells in culture rapidly modulate to synthetic phenotype, which complicates long-term in vitro studies. In contrast, vascular segments or smooth muscle strips in organ culture can maintain contractility for at least a week, sufficient for studies involving altered metabolism or protein expression. Examples are effects of endogenous polyamines on membrane ion channels and excitation-contraction coupling. While smooth muscle tissue is well preserved in serum-free culture, growth stimulation with fetal calf serum (FCS) causes multiple effects, including decreased contractility, ultrastructural changes, decreased expression of L-type Ca2+ channels, and increased SR release of Ca2+ via ryanodine receptors. These are all consequences of increased basal [Ca2+]i caused by FCS, as they are reversed by culture with verapamil in a concentration (1 microM) that does not inhibit stimulation of DNA and protein synthesis by FCS. The effects of FCS on contractility and Ca2+ channel expression are mimicked in serum-free culture with increased [Ca2+]i. Contractile protein patterns, including myosin isoform composition, are unaffected by FCS, suggesting that reversal to synthetic phenotype is limited and not the immediate cause of decreased contractility.

Animals↗
PubMed2000

[Non-selective cationic current--the basis of depolarization in smooth muscle].

The activation of smooth muscle muscarinic receptors leads to its contraction. Electrophysiological and biochemical methods have gradually, over the time span of roughly 30-40 past years, helped to reveal this phenomenon's underlying processes. One element of this cascade of processes is the influx of cations into the smooth muscle cell--non-selective cationic current--causing depolarisation of the cell membrane and subsequent opening of voltage-operated calcium channels. This mini-review provides the reader with up-to-date knowledge on non-selective cationic current, supplemented with information on muscarinic receptors of smooth muscle, their coupling with effectors via G proteins, as well as on muscarinic modulation of calcium and potassium channels of smooth muscle. The conclusion is dedicated to pointing out the future trends of research in this area. (Tab. 2, Fig. 2, Ref. 82.)

Animals↗
PubMed1998

Basic fibroblast growth factor decreases type V/XI collagen expression in cultured bovine aortic smooth muscle cells.

Vascular smooth muscle cells (SMCs), the major cellular constituent of an artery, synthesize the bulk of fibrillar collagens, including type V/XI, which regulates heterotypic collagen fibril assembly. Basic fibroblast growth factor (bFGF) is a heparin-binding polypeptide growth factor that has been implicated in important events during the development of atherosclerosis, such as early intimal SMC proliferation. Here we have investigated the effects of bFGF on aortic SMC expression of type V/XI collagen. Treatment of exponentially growing or serum-deprived subconfluent cultures of bovine aortic SMCs with bFGF decreased the steady-state levels of the mRNAs for collagen type V/XI, including alpha 1(V), alpha 2(V), and alpha 1(XI). The effect of bFGF was time dependent with a two- and a fourfold decrease in alpha 2(V) mRNA observed after treatment for 24 and 48 h, respectively. This decrease resulted from a drop in the rate of alpha 2(V) gene transcription; no change was observed in the stability of the alpha 2(V) mRNA. Furthermore, accumulation of collagen protein decreased upon bFGF treatment. As expected, treatment with bFGF increased the rate of proliferation of serum-deprived SMCs, as judged by DNA content in the cultures, thymidine incorporation, and steady-state mRNA levels of the S-phase-expressed histone H3.2. These results suggest that bFGF plays an important role in the regulation of collagen fibril structure, with potential implications for the development and organization of an atherosclerotic lesion.

Animals↗
PubMed1997

Heparin suppresses sgk, an early response gene in proliferating vascular smooth muscle cells.

Vascular smooth muscle cell (VSMC) hyperplasia plays a central role in chronic and acute vascular pathology including arteriosclerosis and restenosis following vascular surgery. The glycosaminoglycans of the heparan sulfate class, including heparin, inhibit VSMC proliferation in animals and in culture. Heparin binds to high affinity sites on the cell surface, selectively modulates mitogenic signal transduction pathway(s), and rapidly alters transcription of several genes. To further explore the molecular mechanisms responsible for this growth inhibition, we have employed the differential display technique to identify heparin-regulated genes. Here we demonstrate that heparin inhibits the expression of the early response gene sgk (serum and glucocorticoid-regulated kinase). The expression of sgk is not inhibited by chondroitin sulfate, a nonantiproliferative glycosaminoglycan, suggesting that sgk suppression may play a functional role in the antiproliferative effect of heparin. This idea is strengthened by the finding that heparin does not inhibit sgk expression in VSMCs resistant to the antiproliferative effect of heparin or in vascular endothelial cells which are unresponsive to heparin. Expression of sgk mRNA diminishes with increasing concentrations of heparin. Finally, sgk expression is not suppressed by other growth inhibitors such as transforming growth factor-beta 1 (TGF-beta 1) and interferon-beta (IFN-beta), suggesting separate and distinct effects of these growth inhibitors on the mitogenic pathway.

Animals↗
PubMed2000

Type V collagen regulates the assembly of collagen fibrils in cultures of bovine vascular smooth muscle cells.

Vascular smooth muscle cells (SMCs), the major cellular constituent of the medial layer of an artery, synthesize the majority of connective tissue proteins, including fibrillar collagen types I, III, and V/XI. Proper collagen synthesis and deposition, which are important for the integrity of the arterial wall, require the antioxidant vitamin C. Vitamin C serves as cofactor for the enzymes prolyl and lysyl hydroxylase, which are responsible for the proper hydroxylation of collagen. Here, the role of type V collagen in the assembly of collagen fibrils in the extracellular matrix (ECM) of cultured vascular SMCs was investigated. Treatment of SMCs with vitamin C resulted in a dramatic induction in the levels of the cell-layer associated pepsin-resistant type V collagen, whereas only a minor induction in the levels of types I and III collagen was detected. Of note, the deposition of type V collagen was accompanied by the formation of striated collagen fibrils in the ECM. Immunohistochemistry demonstrated that type V collagen, but not type I collagen, became masked as collagen fibrils matured. Furthermore, the relative ratio of type V to type I collagen decreased as the ECM matured as a function of days in culture, and this decrease was accompanied by an increase in the diameter of collagen fibrils. Together these results suggest that the masking of type V collagen is caused by its internalization on continuous deposition of type I collagen on the exterior of the fibril. Furthermore, they suggest that type V collagen acts as framework for the initial assembly of collagen molecules into heterotypic fibrils, regulating the diameter and architecture of these fibrils.

Animals↗