Collagen Fibril Density Research Articles

Matrix mechanical properties of transversalis fascia in inguinal herniation as a model for tissue expansion

Inguinal herniation represents a common condition requiring surgical intervention. Despite being regarded as a connective tissue disorder of uncertain cause, research has focused predominantly on biochemical changes in the key tissue layer, the transversalis fascia (TF) with little direct analysis of functional tissue mechanics. Connective tissue tensile properties are dominated by collagen fibril density and architecture. This study has correlated mechanical properties of herniated TF (HTF) and non-herniated TF (NHTF) with fibrillar properties at the ultrastructural level by quasi-static tensile mechanical analysis and image analysis of collagen electron micrographs. No significant difference was found between any of the key mechanical properties (break stress, strain or modulus) for HTF and NHTF. In addition, no significant differences were found in average collagen fibril diameter, density or fibre bundle spacing. However, both groups displayed anisotropy with greater break stress ( p=0.001) on average in the transverse anatomical plane compared to the longitudinal plane in a mean ratio of 2:1 (anisotropy ratio), though there was no evidence of a difference in this ratio for HTF and NHTF for both break stress and modulus. It was noted that this anisotropy ratio corresponds closely with the expected force distribution on a model cylindrical structure loaded axially. The absence of other functional differences does not support the idea of a failing (injured) tissue but is consistent with it being a tissue undergoing chronic growth/expansion under multi-vectored mechanical loading. These findings provide new clues to collagen tissue herniation for mathematical modelling and model tissue engineering.

Variation of diameter distribution, number density, and area fraction of fibrils within five areas of the rabbit patellar tendon

The purpose of this investigation is to show microstructural information at various regions within the rabbit patellar tendon. The properties of the rabbit patellar tendon are well documented mechanically, but detailed information at the microscopic level is not available. Increasing attention has been directed to soft tissue microscopy as the demand for development of biologically inspired materials increases. Microstructural examination of the tendon fibrils is performed to provide further insight into understanding of the structure to function relations within the rabbit patellar tendon. Limited studies on rabbit patellar tendon collagen fibrils at the microscopic level have been computed. Furthermore, evaluation of structure-function relations in multiple regions of any given specimen of a particular tissue type has not been conducted. In this study the number density, area fraction, and diameter distribution of collagen fibrils have been determined. Overall, this examination showed considerable variation within each section of the tendon. Correlating these structural results with mechanical tests of the tendon portions in the various regions could provide additional information on the mechanics of the rabbit tendon as well as insight into development of artificial tissue constructs.

Endogenous overexpression of hyaluronan synthases within dynamically cultured collagen gels: Implications for vascular and valvular disease

Hyaluronan is a ubiquitous component of the extracellular matrix with important roles in cell and tissue functions. Hyaluronan content is often elevated in cardiovascular diseases, such as mitral valve disease and atherosclerosis. The objective of this study was to determine the impact of endogenously produced hyaluronan dynamically cultured three-dimensional model of collagenous tissues. Collagen gels containing excess HA and hyaluronan synthase ( has) overexpressing cells were grown in a cyclic strain environment to simulate cell-mediated matrix organization. Cyclic strain caused a significant elevation in the collagen fibril density, cell number, and hyaluronan content of the resulting collagen gels compared to those grown under a static strain regimen. The material behavior of collagen gels containing has overexpressing cells was also notably weakened compared to controls. Transmission electron microscopy and immunohistochemistry showed that proteoglycan distribution was influenced by both strain and has overexpression. The results were also dependent on the specific has isozyme overexpressed. This investigation helps to identify the mechanism by which hyaluronan acts in vivo to alter tissue material behavior in cardiovascular diseases such as myxomatous mitral valve disease and atherosclerosis.

Influence of cyclic strain and decorin deficiency on 3D cellularized collagen matrices

Cyclic strain evokes the expression of the small leucine-rich proteoglycans decorin and biglycan in 2D cultures and native tissues. However, strain-dependent expression of these proteoglycans has not been demonstrated in engineered tissues. We hypothesized that the absence of decorin may compromise the effect of cyclic strain on the development of engineered tissues. Thus, we investigated the contribution of decorin to tissue organization in cyclically strained collagen gels relative to statically cultured controls. Decorin null ( Dcn −/−) and wild-type murine embryonic fibroblasts were seeded within collagen gels and mechanically conditioned using a Flexcell ® Tissue Train ® culture system. After 8 days, the cyclically strained samples demonstrated greater collagen fibril density, proteoglycan content, and material strength for both cell types. On the other hand, increases in cell density, collagen fibril diameter, and biglycan expression were observed only in the cyclically strained gels seeded with Dcn −/− cells. Although cyclic strain caused an elevation in proteoglycan expression regardless of cell type, the type of proteoglycan differed between groups: the Dcn −/− cell-seeded gels produced an excess of biglycan not found in the wild-type controls. These results suggest that decorin-mediated tissue organization is strongly dependent upon tissue type and mechanical environment.

Response of Knee Ligaments to Prolotherapy in a Rat Injury Model

Background Prolotherapy is an alternative therapy for chronic musculoskeletal injury including joint laxity. The commonly used injectant, D-glucose (dextrose), is hypothesized to improve ligament mechanics and decrease pain through an inflammatory mechanism. No study has investigated the mechanical effects of prolotherapy on stretch-injured ligaments. Hypotheses Dextrose injections will enlarge cross-sectional area, decrease laxity, strengthen, and stiffen stretch-injured medial collateral ligaments (MCLs) compared with controls. Dextrose prolotherapy will increase collagen fibril diameter and density of stretch-injured MCLs. Study Design Controlled laboratory study. Methods Twenty-four rats were bilaterally MCL stretch-injured, and the induced laxity was measured. After 2 weeks, 32 MCLs Were injected twice, 1 week apart, with either dextrose or saline control; 16 MCLs received no injection. Seven uninjured rats (14 MCLs) were additional controls. Two weeks after the second injection, ligament laxity, mechanical properties (n = 8), and collagen fibril diameter and density (n = 3) were assessed. Results The injury model created consistent ligament laxity (P < .05) that was not altered by dextrose injections. Cross-sectional area of dextrose-injected MCLs was increased 30% and 90% compared with saline and uninjured controls, respectively (P < .05). Collagen fibril diameter and density were decreased in injured ligaments compared with uninjured controls (P < .05), but collagen fibril characteristics were not different between injured groups. Conclusion Dextrose injections increased the cross-sectional area of MCLs compared with saline-injected and uninjured controls. Dextrose injections did not alter other measured properties in this model. Clinical Relevance Our results suggest that clinical improvement from prolotherapy may not result from direct effects on ligament biomechanics.

Morphometric analysis of collagen fibrils in skin of patients with spontaneous cervical artery dissection

Background and aim: The aetiopathogenesis of spontaneous cervical artery dissection (sCAD) is largely unknown. Electron microscopic (EM) examination of skin biopsies of patients with sCAD revealed very subtle pathological changes...

Peritumoral TNFα administration influences tumour stroma structure and physiology independently of growth in DMBA‐induced mammary tumours

Background. Systemic treatment of malignancies with high doses of tumour necrosis factor‐α (TNFα) has an anticancer effect, but also serious side effects. The aim of the present study was to elucidate the effects of local TNFα administration alone or in combination with chemotherapy on tumour stroma structure and physiology in di‐methyl‐benz‐anthracene (DMBA)‐induced mammary carcinomas in rats. Methods. TNFα (500 ng/mL in a volume of 5 µL) was given s.c. around the carcinoma and 5‐fluorouracil (5‐FU) (1.5 mg/kg, volume of 0.2 mL) was given i.p on days 1, 4, 7 and 10. Results. Treatment with TNFα resulted in a significant reduction of tumour interstitial fluid pressure (TIFP: 75–87 %, p<0.02–0.001), as well as in the number of tumour‐infiltrating macrophages, extracellular volume (ECV) and collagen fibril density in carcinoma. In addition, pH was lowered in tumours treated with TNFα, suggesting decreased aerobic metabolism. Treatment with TNFα, however, had no effect on tumour growth, arterial blood pressure, tumour vessel density, plasma volume or body weight. Concentrations of locally produced VEGF and IL‐1β in carcinoma interstitial fluid or in serum were not affected by TNFα. The study demonstrated that these cytokines are produced locally in the tumour. Furthermore, TNFα had no effect on efficacy of treatment with 5‐FU. Conclusions: Locally administered TNFα did not affect DMBA‐induced mammary tumour growth or vasculature, but reduced inflammation and ECM structure, suggesting the latter to be of importance in the observed reduction in TIFP.

Regulation of Corneal Fibroblast Morphology and Collagen Reorganization by Extracellular Matrix Mechanical Properties

To investigate how extracellular matrix mechanical properties influence cell and matrix patterning in three-dimensional culture. Human corneal fibroblasts were seeded within 30 x 10 mm collagen matrices that were unconstrained (UN), fully constrained (CO) along the long axis by attaching the construct to two immobilized plastic bars, or partially constrained (PC) by allowing linear elastic displacement of one bar. After 24 hours, constructs were labeled with phalloidin and were imaged using fluorescent and reflected light (for collagen) confocal microscopy. Cell morphology and local collagen fibril density and alignment were measured using digital image processing. Corneal fibroblasts in UN matrices were less elongated (UN < PC < CO; P < 0.05) than those in constrained matrices. Cells were aligned parallel to the long axis in the anisotropic region of constrained matrices but were randomly aligned in unconstrained (isotropic) matrices (UN < PC = CO; P < 0.05). Both the local collagen density and the degree of cell/collagen coalignment were higher in constrained matrices (UN < PC < CO; P < 0.05). In regions of higher cell density, additional bands of aligned collagen were often observed between individual cells. These data suggest that cell spreading, alignment, and contractile force generation are directly influenced by the mechanical properties of the surrounding extracellular matrix (ECM). Corneal fibroblasts generally align and compact collagen parallel to the axis of greatest ECM stiffness. Mechanical cross-talk between adjacent cells leads to enhancement of matrix reorganization, and results in additional, more complex matrix patterning.

Collagen Organization in Canine Myxomatous Mitral Valve Disease: An X-Ray Diffraction Study

Collagen fibrils, a major component of mitral valve leaflets, play an important role in defining shape and providing mechanical strength and flexibility. Histopathological studies show that collagen fibrils undergo dramatic changes in the course of myxomatous mitral valve disease in both dogs and humans. However, little is known about the detailed organization of collagen in this disease. This study was designed to analyze and compare collagen fibril organization in healthy and lesional areas of myxomatous mitral valves of dogs, using synchrotron small-angle x-ray diffraction. The orientation, density, and alignment of collagen fibrils were mapped across six different valves. The findings reveal a preferred collagen alignment in the main body of the leaflets between two commissures. Qualitative and quantitative analysis of the data showed significant differences between affected and lesion-free areas in terms of collagen content, fibril alignment, and total tissue volume. Regression analysis of the amount of collagen compared to the total tissue content at each point revealed a significant relationship between these two parameters in lesion-free but not in affected areas. This is the first time this technique has been used to map collagen fibrils in cardiac tissue; the findings have important applications to human cardiology.

Quantitative Histology and Ultrastructure Fail to Explain Weakness of Immobilized Rabbit Achilles’ Tendons

Zhou J, Koike Y, Uhthoff HK, Trudell G. Quantitative histology and ultrastructure fail to explain weakness of immobilized rabbit Achilles’ tendons. Objective To test the hypothesis that mechanical weakness caused by immobilization is the result of characteristic histologic and ultrastructural changes in rabbit Achilles’ tendons. Design Single-blind, randomized controlled trial. Setting University animal care facility. Animals Twenty-three New Zealand rabbits. Intervention Twenty weight-matched rabbits underwent unilateral hind leg immobilization. The Achilles’ tendons of immobilized and contralateral legs were harvested after 4 or 8 weeks. For ultrastructural outcomes, 6 normal Achilles’ tendons of 3 rabbits served as controls. Main Outcome Measures Light microscopic assessments were made on the tendons for cross-sectional area of the tendon, number of tenocytes, adipocytes and blood vessels, roundness of nuclei, area of intense metachromasia, and area of spatially aligned collagen fibers. Transmission electron microscopy (TEM) measured mean collagen fibril diameter and density. Results Light microscopic assessment failed to reveal a statistical difference in any of the outcome measures between immobilized and contralateral tendons. TEM did not show a statistical difference in mean fibril diameter between the immobilized groups (4wk, 113.8±1.6nm; 8wk, 113.5±1.4nm) compared with their respective contralateral tendons (4wk, 111.4±1.4nm; 8wk, 116.2±1.8nm) and normal controls (111.8±2.0nm). Eight-week contralateral fibrils were statistically larger than 4-week contralateral fibrils, which was attributed to a training effect of the leg opposite of the casted leg. Conclusions Our results add to the recent literature about the absence of characteristic histologic or collagen fibril size markers that could explain the mechanical weakness of immobilized tendons. Further research using biochemical, gene expression, and functional imaging markers of tendon is needed to pinpoint the alterations responsible for the mechanical weakness. Such markers would be crucial for the rehabilitation and secondary prevention of tendon injuries.

A Missense Mutation in the M1S1 Gene Found in a Turkish Patient With Gelatinous Droplike Corneal Dystrophy

To report a missense mutation in the M1S1 gene found in a Turkish patient with gelatinous droplike corneal dystrophy (GDLD). A Turkish patient with GDLD was examined. Keratoplasty was performed and a diagnosis of GDLD was made by histopathologic and electron microscopic studies. Genomic DNA was extracted from peripheral blood and the paraffin-embedded tissue of the corneal button. A 248-bp DNA fragment of the M1S1 gene was amplified, and sequencing reactions were analyzed. The results were compared with those of 30 healthy, nonrelated individuals. On light microscopic examination, sheets of amorphous amyloid deposits were observed in subepithelial regions and in the anterior and midcorneal stroma. Electron microscopy revealed dense collagen fibrils and entrapped filamentous amyloid fibrils in the corneal stroma. A substitution of T-->C at nucleotide 557 was found in the peripheral blood DNA sequence analysis, which resulted in an amino acid substitution of L-->P (L186P). Results were confirmed by direct DNA sequencing analysis of the paraffin-embedded corneal button. The patient with GDLD was homozygous for the mutation, resulting in amino acid substitution L186P. This is the first report, to our knowledge, of a homozygous mutation (L186P) in the M1S1 gene found in a Turkish patient. The clinical examination may be insufficient in sporadic cases, and histopathologic examination and molecular genetic analysis can accelerate and improve the accuracy of diagnosis in patients with GDLD.

Morphologic and Histologic Comparison Between the Patella and Hamstring Tendons Grafts: A Descriptive and Anatomic Study

Morphologic and histologic comparison of patella and hamstring tendon grafts. Hamstring tendons (semitendinosus and gracilis) and patellar tendons were taken from 20 cadaveric knees and were investigated by using light and electron microscopy, immunohistochemistry, and morphometry. The thickness of collagen fibrils, fibril/interstitum ratio, density of blood vessels, density of fibroblasts, and distribution of the collagen fibrils were analyzed. The semitendinosus and gracilis tendons provide 20% and 30% more fibril/interstitum ratio compared with the patella tendon (P = .0056 and .0028). Also, the density of fibroblasts was 50% and 35% more (P = .0061 and .0050). No differences regarding the thickness of the collagen fibrils, density of blood vessels, and distribution of the fibrils were found. Both semitendinous and gracilis tendons provide significantly more density of collagen fibrils as well as density of fibroblasts in comparison with patellar tendons. These findings provide a potential advantage of the hamstrings group on better remodelling and regeneration of the tissue. These grafts have been used as autografts for anterior cruciate ligament reconstruction. Despite the interest on these tendons, their microscopic structure has not been sufficiently investigated yet.

Rho plays a central role in regulating local cell‐matrix mechanical interactions in 3D culture

The purpose of this study was to assess quantitatively the role of the small GTPase Rho on cell morphology, f-actin organization, and cell-induced matrix remodeling in 3D culture. Human corneal fibroblasts (HTK) were infected with adenoviruses that express green fluorescent protein (GFP) or GFP-N19Rho (dominant negative Rho). One day later cells were plated inside collagen matrices and allowed to spread for 24 h. Cells were fixed and stained for f-actin. Fluorescent (for f-actin) and reflected light (for collagen fibrils) images were acquired using confocal microscopy. Fourier transform analysis was used to assess local collagen fibril alignment, and changes in cell morphology and collagen density were measured using MetaMorph. The decrease in matrix height was used as an indicator of global matrix contraction. HTK and HTK-GFP cells induced significant global matrix contraction; this was inhibited by N19Rho. HTK and HTK-GFP fibroblasts generally had a bipolar morphology and occasional intracellular stress fibers. Collagen fibrils were compacted and aligned parallel to stress fibers and pseudopodia. In contrast, HTK-GFPN19 cells were elongated, and had a more cortical f-actin distribution. Numerous small extensions were also observed along the cell body. In addition, both local collagen fibril density and alignment were significantly reduced. Rho plays a key role in regulating both the morphology and mechanical behavior of corneal fibroblasts in 3D culture. Overall, the data suggest that Rho-kinase dependent cell contractility contributes to global and local matrix remodeling, whereas Rho dependent activation of mDia and/or other downstream effectors regulates the structure and number of cell processes.

The effect of surface chemistry on the formation of thin films of native fibrillar collagen

In this study, we used well-defined, homogeneous, gradient and patterned substrates to explore the effects of surface chemistry on the supramolecular structure of adsorbed type I collagen. Type I collagen (320 μg/mL) was allowed to adsorb onto self-assembled CH 3-, COOH-, NH 2- and OH-terminated alkylthiolate monolayers at 37 °C. Atomic force microscopy, ellipsometry and phase microscopy indicated that large supramolecular collagen fibril structures (approximately 200 nm in diameter, several microns long) assembled only at the hydrophobic CH 3-terminated surfaces. By varying the surface energy using a mixture of OH- and CH 3-terminated thiols during monolayer formation, we found that large fibril assembly occurred at surfaces with a water contact angle above 83°, but not on surfaces with a water contact angle below 63°. Examining a surface with a linear hydrophobicity gradient revealed that the assembly of large collagen fibrils requires a hydrophobic surface with a water contact angle of at least 78°. Collagen fibril density increased over a narrow range of surface energy and reached near-maximum density on surfaces with a water contact angle of 87°. These studies confirm that the supramolecular structure of adsorbed collagen is highly dependent on the underlying substrate surface chemistry. We can take advantage of this dependency to pattern areas of fibrillar and non-fibrillar collagen on a single surface. Morphology studies with vascular smooth muscle cells indicated that only collagen films formed on hydrophobic substrates mimicked the biological properties of fibrillar collagen gels.

Quantitative assessment of local collagen matrix remodeling in 3-D Culture: The role of Rho kinase

The purpose of this study was to quantitatively assess the role of Rho kinase in modulating the pattern and amount of local cell-induced collagen matrix remodeling. Human corneal fibroblasts were plated inside 100-μm thick fibrillar collagen matrices and cultured for 24 h in media with or without the Rho kinase inhibitor Y-27632. Cells were then fixed and stained with phalloidin. Fluorescent (for f-actin) and reflected light (for collagen fibrils) 3-D optical section images were acquired using laser confocal microscopy. Fourier transform analysis was used to assess collagen fibril alignment, and 3-D cell morphology and local collagen density were measured using MetaMorph. Culture in serum-containing media induced significant global matrix contraction, which was inhibited by blocking Rho kinase ( p < 0.001). Fibroblasts generally had a bipolar morphology and intracellular stress fibers. Collagen fibrils were compacted and aligned parallel to stress fibers and pseudopodia. When Rho kinase was inhibited, cells had a more cortical f-actin distribution and dendritic morphology. Both local collagen fibril density and alignment were significantly reduced ( p < 0.01). Overall, the data suggests that Rho kinase-dependent contractile force generation leads to co-alignment of cells and collagen fibrils along the plane of greatest resistance, and that this process contributes to global matrix contraction.

MORPHOLOGICAL CHANGES OF COLLAGEN FIBRILS IN THE SUBSYNOVIAL CONNECTIVE TISSUE IN CARPAL TUNNEL SYNDROME

Background: Pathologic changes occur commonly in the subsynovial connective tissue in patients with carpal tunnel syndrome. The purposes of this study were to investigate the ultrastructural changes of the subsynovial connective tissue in these patients and compare them with the findings in cadaver controls. Methods: The diameter and density of collagen fibrils were measured by transmission electron microscopy in specimens of subsynovial connective tissue from ten patients with idiopathic carpal tunnel syndrome and from ten fresh-frozen cadavers of individuals without known symptoms of carpal tunnel syndrome. Results: We noted deformed collagen fibrils with a spiraled appearance in the specimens from the patients. We also observed phagocytosis of elastin fibrils in all of those specimens. These changes were noted only rarely in the cadaver controls. The mean diameter (and standard deviation) of the collagen fibrils was 45.5 ± 8.0 nm in the control group and 54.8 ± 15.2 nm in the patient group (p < 0.05). The mean number of collagen fibrils per 0.04 μm2 (density) was 201.38 ± 48.88 in the control group and 157.08 ± 54.38 in the patient group (p < 0.05). Conclusions: These ultrastructural findings suggest that subsynovial collagen in patients with carpal tunnel syndrome is structurally different from that in individuals without carpal tunnel syndrome, but the processes resulting in that abnormal morphology remain to be elucidated. Level of Evidence: Prognostic Level III. See Instructions to Authors for a complete description of levels of evidence.

Morphological Changes of Collagen Fibrils in the Subsynovial Connective Tissue in Carpal Tunnel Syndrome

Pathologic changes occur commonly in the subsynovial connective tissue in patients with carpal tunnel syndrome. The purposes of this study were to investigate the ultrastructural changes of the subsynovial connective tissue in these patients and compare them with the findings in cadaver controls. The diameter and density of collagen fibrils were measured by transmission electron microscopy in specimens of subsynovial connective tissue from ten patients with idiopathic carpal tunnel syndrome and from ten fresh-frozen cadavers of individuals without known symptoms of carpal tunnel syndrome. We noted deformed collagen fibrils with a spiraled appearance in the specimens from the patients. We also observed phagocytosis of elastin fibrils in all of those specimens. These changes were noted only rarely in the cadaver controls. The mean diameter (and standard deviation) of the collagen fibrils was 45.5 +/- 8.0 nm in the control group and 54.8 +/- 15.2 nm in the patient group (p < 0.05). The mean number of collagen fibrils per 0.04 microm2 (density) was 201.38 +/- 48.88 in the control group and 157.08 +/- 54.38 in the patient group (p < 0.05). These ultrastructural findings suggest that subsynovial collagen in patients with carpal tunnel syndrome is structurally different from that in individuals without carpal tunnel syndrome, but the processes resulting in that abnormal morphology remain to be elucidated.

Effects of Ingestion of Collagen Peptide on Collagen Fibrils and Glycosaminoglycans in the Dermis

In order to investigate the effects of collagen peptide ingestion on fibroblasts and the extracellular matrix in the dermis, collagen peptide was administered orally to pigs at 0.2 g/kg body weight/d for 62 d, and its effects were compared with those of lactalbumin and water controls. Fibroblast density, and diameter and density of collagen fibrils were significantly larger in the collagen peptide group than in the lactalbumin and water control groups. The two major components of dermal glycosaminoglycans, hyaluronic acid and dermatan sulfate, which are present in the inter-fibrillar space, did not differ significantly among the three groups. However, the ratio of dermatan sulfate, which is derived from fibril-bound decorin, was largest in the collagen peptide group. These results suggest that ingestion of collagen peptide induces increased fibroblast density and enhances formation of collagen fibrils in the dermis in a protein-specific manner.

Current concepts in soft connective tissue wound healing.

The strength and integrity of intact soft connective tissues are related to the forces which exist between collagen fibrils and these in turn appear to depend on collagen fibril size, density and architecture en masse. The genetic type of collagen, enzymic modifications to the collagen monomer and the proteoglycan environment all affect fibril size. Current evidence suggests that the restoration of tissue continuity and the early redevelopment of tissue strength following wounding are initially achieved by the formation of a myofibroblast-reticulin network which eventually disappears as the healing wound ages. The extent of this network defines the area in which repair tissue will be laid down and the network is equipped with the sensory apparatus to monitor the physical and chemical environment where healing is taking place and thus to direct the various facets of connective tissue synthesis outlined above. The maturation of the scar connective tissue matrix and the development of attachment between new and original connective tissues are simultaneous, related but independent processes. It takes some time before the weld is achieved by the same forces that hold connective tissue fibres together in intact tissues and the myofibroblast-reticulin network is replaced.

Influence of the aggregation state in solution on the supramolecular organization of adsorbed type I collagen layers

In the last years, adsorbed collagen was shown to form layers with a supramolecular organization depending on the substrate surface properties and on the preparation procedure. If the concentration of collagen and the duration of adsorption are sufficient, fibrillar collagen structures are formed, corresponding to assemblies of a few molecules. This occurs more readily on hydrophobic compared to hydrophilic surfaces. This study aims at understanding the origin of such fibrillar structures and in particular at determining whether they result from the deposition of fibrils formed in solution or from the building of assemblies at the interface. Therefore, type I collagen solutions with an increasing degree of aggregation were prepared, using the “neutral-start” approach, by ageing pH 5.8 solutions at 37 °C for 15 min, 2 or 7 days. The obtained solutions were used to investigate the influence of collagen aggregation in solution on the supramolecular organization of adsorbed collagen layers, which was characterized by X-ray photoelectron spectroscopy and atomic force microscopy. Polystyrene and plasma-oxidized polystyrene were chosen as substrates for the adsorption. The size and the density of collagen fibrils at the interface decreased upon increasing the degree of aggregation of collagen in solution. This is explained by a competitive adsorption process between monomers and aggregates of the solution, turning at the advantage of the monomers. More aggregated solutions, which are thus depleted in free monomers, behave like less concentrated solutions, i.e. lead to a lower adsorbed amount and less fibril formation at the interface. This study shows that the supramolecular fibrils observed in adsorbed collagen layers, especially on hydrophobic substrates, are not formed in the solution, prior to adsorption, but are built at the interface, through the assembly of free segments of adsorbed molecules.