Collagen Pattern Research Articles

Small-angle x-ray scattering studies of human breast tissue samples

Small-angle x-ray scattering (SAXS) patterns are recorded from thin breast tissue samples containing healthy and cancerous regions. The SAXS patterns are compared with histo-pathological observations. The information available from SAXS is reviewed, and a model for scattering from collagen is presented. Scattering patterns of collagen at regions far from the tumours are essentially different from those at tumours. The axial period of collagen fibrils is 65.0 ± 0.1 nm in healthy regions, and 0.3 nm larger in cancer-invaded regions. The average intensity of scattering from cancerous regions is an order of magnitude higher than the intensity from healthy regions. This is interpreted to arise from an increase of the specific surface area of the scatterers, which is due to a disruption of the molecular and supra-molecular structures in cancerous regions and invasion of new types of cells. The differences of the SAXS patterns are large and distinctive enough to suggest that these phenomena may be utilized in mammography.

Temporal expression patterns of BMP receptors and collagen II (B) during periosteal chondrogenesis

Articular cartilage has a limited ability to repair itself. Periosteal grafts have chondrogenic potential and are used clinically to repair defects in articular cartilage. An organ culture model system for in vitro rabbit periosteal chondrogenesis has been established to study the molecular events of periosteal chondrogenesis in vitro. In this model, bone morphogenetic protein-2 (BMP2) mRNA expression was found to be upregulated in the first 12 h. BMPs usually transduce their signals through a receptor complex that includes type II and either type IA or type IB BMP receptors. Receptors IA and IB play distinct roles during limb development. We have examined the temporal expression patterns for the mRNAs of these receptors using our experimental model. The mRNA expression patterns of these three BMP receptors differed from one another in periosteal explants during chondrogenesis. When these explants were cultured under chondrogenic conditions (agarose suspension with TGF-β1 added to the media for the first 2 days), the expression of BMPRII mRNA and that of BMPRIA mRNA varied only slightly and persisted over a long time. In contrast, the expression of BMPRIB mRNAwas upregulated within 12 h, peaked at day 5, and fell to a level that was barely detected beyond day 21. Moreover, the expression of BMPRIB mRNA preceded that of collagen type IIB mRNAs, a marker for matrix-depositing chondrocytes. These data support a role for coordinate expression of BMP2 and its receptors early during periosteal chondrogenesis.

The ultrastructure of anorganic bovine bone and selected synthetic hyroxyapatites used as bone graft substitute materials

The objective of this study was to investigate the morphology and organization of apatite crystallites in mature mammalian bone. Anorganic bovine bone was studied in this investigation to allow for the examination of the mineral crystallites after removal of the organic phase. Field-emission low-voltage scanning electron microscopy (FE-LVSEM) was employed to obtain images at nanometer resolution without the application of a conductive coating. Transmission electron microscopy (TEM) of the samples was also performed to confirm the identification of features observed in the SEM and to allow for comparison with earlier studies of bone mineral architecture. For comparison, in order to demonstrate how the interaction of collagen and apatite results in the architecture and crystal structure of bone mineral, two synthetic hydroxyapatite materials were also analyzed: OsteoGen and OsteoGraf/LD300. FE-LVSEM revealed distinctive features of bone mineral: a fibrillar organization of crystallites, a periodic spacing of crystallites along the fibrils consistent with the banding pattern of collagen, inter-fibrillar bridging crystallites, and a plate-like habit of the crystallites. These findings supported the hypothesis, derived from the earlier TEM data of others, that the mineralization of collagen comprising osteoid proceeds by the formation of apatite crystallites within the fibers at selected periodic sites along their length. Moreover, the very presence in this anorganic material of distinct fibers comprised of the crystallites is demonstration of inter-crystallite bonding. The crystallites of the synthetic hydroxyapatite materials did not display any of these ultrastructural features.

The localized expression of extracellular matrix components in healing tendon insertion sites: an in situ hybridization study

The localized expression of a number of extracellular matrix genes was evaluated over time in a novel rat rotator cuff injury model. The supraspinatus tendons of rats were severed at the bony insertion and repaired surgically. The healing response was evaluated at 1, 2, 4, and 8 weeks post-injury using histologic and in situ hybridization techniques. Expression patterns of collagens (I, II, III, IX, X, XII), proteoglycans (decorin, aggrecan, versican, biglycan, fibromodulin), and other extracellular matrix proteins (elastin, osteocalcin, alkaline phosphatase) were evaluated at the healing tendon to bone insertion site. Histologic results indicate a poor healing response to the injury, with only partial recreation of the insertion site by 8 weeks. In situ hybridization results indicate a specific pattern of genes expressed in each zone of the insertion site (i.e., tendon, fibrocartilage, mineralized cartilage, bone). Overall, expression of collagen types I and XII, aggrecan, and biglycan was increased, while expression of collagen type X and decorin was decreased. Expression of collagen type I, collagen type XII, and biglycan decreased over time, but remained above normal at 8 weeks. Results indicate that the rat supraspinatus tendon is ineffective in recreating the original insertion site, even at 8 weeks post-injury, in the absence of biological or biomechanical enhancements.

Contacts with fibrils containing collagen I, but not collagens II, IX, and XI, can destabilize the cartilage phenotype of chondrocytes

Objective Cell-matrix interactions are important regulators of cellular functions, including matrix synthesis, proliferation and differentiation. This is well exemplified by the characteristically labile phenotype of chondrocytes that is lost in monolayer culture but is stabilized in suspension under appropriate conditions. We were interested in the role of collagen suprastructures in maintaining or destabilizing the cartilage phenotype of chondrocytes. Design Primary sternal chondrocytes from 17-day-old chick embryos were cultured in gels of fibrils reconstituted from soluble collagen I from various sources. The culture media either contained or lacked FBS. Cells were cultured for up to 28 days and the evolution of the phenotype of the cells was assessed by their collagen expression (collagens II and X for differentiated chondrocytes and hypertrophic chodrocytes, repectively; collagen I for phenotypically modulated cells), or by their secretion of alkaline phosphatase (hypertrophic cartilage phenotype). Results The cells often retained their differentiated phenotype only if cultured with serum. Under serum-free conditions, cartilage characteristics were lost. The cells acquired a fibroblast-like shape and, later, synthesized collagen I instead of cartilage collagens. Shape changes were influenced by β1-integrin-activity, whereas other matrix receptors were important for alterations of collagen patterns. Heterotypic fibrils reconstituted from collagens II, IX, and XI did not provoke this phenotypic instability. Conclusions Chondrocytes sensitively recognize the suprastructures of collagen fibrils in their environment. Cellular interactions with fibrils with appropriate molecular organizations, such as that in cartilage fibrils, result in the maintenance of the differentiated cartilage phenotype. However, other suprastructures, e.g. in reconstituted fibrils mainly containing collagen I, lead to cell-matrix interactions incompatible with the cartilage phenotype. The maintenance of the differentiated traits of chondrocytes is pivotal for the normal function of, e.g., articular cartilage. If pathologically altered matrix suprastructures lead to a dysregulation of collagen production also in vivo compromised cartilage functions inevitably will be propagated further.

Modulable Nanometer-Scale Surface Architecture Using Spin-Coating on an Adsorbed Collagen Layer

A strategy was developed to create a modulable polymer surface architecture (topography, chemical composition) at the nanometer scale. Therefore, collagen was first adsorbed on a poly(methyl methacrylate) (PMMA) substrate and dried at high or low rate to produce continuous or discontinuous layers, respectively. Solutions of PMMA in chlorobenzene were then spin-coated on top of these collagen layers. The obtained surfaces were investigated using atomic force microscopy and X-ray photoelectron spectroscopy. Spin-coating with pure chlorobenzene on the continuous collagen layer produced pits in the PMMA substrate through the collagen layer; spin-coating with PMMA solutions of increasing concentrations progressively led to the formation of a surface covered by particles made of PMMA and collagen, resulting from a combination of dissolution of PMMA from the substrate and deposition of PMMA from the solution. Spin-coating with pure chlorobenzene on the discontinuous collagen layer led to dissolution of PMMA and to its redeposition on the collagen pattern, which served as a template. This provided a surface entirely composed of PMMA, with cavities in the range of 0.1-1 mum diameter and 50-250 nm depth. In this case, the surface relief was independent of the PMMA concentration of the spin-coated solution, the substrate PMMA dissolution and redeposition being the dominant processes.

Myofibroblastoma and solitary fibrous tumour of the breast: histopathologic and immunohistochemical studies

Thirteen mesenchymal tumours of the breast were reviewed histologically and immunohistochemically. Nine tumours (male:female ratio 5:4, average age 64 years) were classified as myofibroblastomas and presented as a single nodule (four) or a multilobular mass (five). They were composed of elongated cells with vesicular nuclei showing grooves, intranuclear inclusion, and small but conspicuous nucleoli resembling myofibroblasts seen in scar tissue. In six tumours, hypercellular zones alternated with paucicellular, hyalinized areas. The collagen pattern was dense, diffuse, and brightly eosinophilic in all neoplasms. The tumour cells were positive for desmin, actin, and vimentin in all nine lesions, and in six tumours a focal CD 34 positivity was also demonstrated. Four tumours (four female patients, average age 75 years) were classified as solitary fibrous tumours and consisted of well-circumscribed nodules. They were characterized by a monomorphic population of thin, spindled to ovoid cells with finely dispersed chromatin and inconspicuous nucleoli. The pattern of the collagen in these tumours was one of thick, brightly eosinophilic bands. These four tumours were negative for all markers tested except vimentin and CD 34. Although myofibroblastomas and solitary fibrous tumours of the breast share many morphologic features, there are enough differences in their cytologic composition and, most importantly, in their immunohistochemical profile to consider them as distinct entities.

Age- and gender-related collagen distribution in human vocal folds.

The composition of the lamina propria in human vocal folds has been shown to affect vocal performance. Collagen plays a significant role in the biomechanical effects of the lamina propria. Specifically, it lends tensile strength to the rapidly oscillating fold. We obtained from a state medical examiner 38 larynges from men and women in infant, adult, and geriatric age groups. We stained the vocal folds for collagen using a picric acid stain and studied them using an image analysis system. Distributions of collagen were measured from the superficial to deep layers (from epithelium to vocalis muscle) within the lamina propria. The data showed an increase in collagen content from infant to adult stages. Infant folds had about 51% of the collagen found in all adults and in geriatric patients (p < .001). There was no significant difference between adult and geriatric folds (p < .16). There was, however, a gender difference in the amount of collagen in both adult and geriatric specimens. Female adult and geriatric folds had about 59% of the collagen found in male adult and geriatric folds (p < .001). The distribution pattern of collagen showed that most of the collagen was present in the deep layer. From these data we conclude that there are age-related and gender-related differences between male and female infant, adult, and geriatric vocal folds. Stress-strain performance studies need to be correlated with histologic findings to better study the phonetic implications of these findings.

Collagen as a model system to investigate the use of aspirin as an inhibitor of protein glycation and crosslinking

Aspirin has been shown to be a powerful inhibitor of post-Amadori Maillard reactions, although the exact mechanism of this action remains unclear. We have used corneal and scleral collagen as a model system: (i) to assess how aspirin, either alone or in combination with sugars, affects the surface charge distribution along the collagen fibrils; (ii) to see how sugars and/or aspirin affect the swelling properties of the cornea; and (iii) to see if sugars and/or aspirin change the distribution of water within the corneal stroma as the tissue swells. Charge changes were detected by examining changes in the uptake of phosphotungstate ions as seen in the electron microscope. Swelling was measured by monitoring the uptake of water as a function of swelling time, and water distribution was determined by using synchrotron X-ray diffraction to follow changes in the interfibrillar Bragg spacing as the cornea swells. Aspirin has a marked effect on the positive staining pattern of scleral collagen. This is different to the changes in stain uptake produced by glycation. Incubation with both sugars and aspirin showed that the sugar binding takes precedence over the effects of aspirin which, in turn, suggests that protein acetylation by aspirin is unlikely under these circumstances. However, aspirin completely suppresses corneal swelling. Even when the aspirin is removed, swelling in distilled water is reduced, and this is accompanied by changes in the water distribution. The results suggest that water is more evenly distributed in aspirin-treated corneas that are subsequently swollen than in swollen glycated corneas. Fructation, glucation and ribation on their own have little effect on the uptake of water as the cornea swells. This suggests that any sugar-derived crosslinks formed at this stage do not limit swelling.

Fetal wound repair results in scar formation in interleukin-10–deficient mice in a syngeneic murine model of scarless fetal wound repair

Background: Fetal dermal wound healing is characterized by minimal inflammation, restoration of normal dermal architecture, and scarless repair. The authors have shown that proinflammatory cytokines interleukin-6 (IL-6) and interleukin-8 (IL-8) are diminished during fetal wound repair. Interleukin-10 (IL-10) is an antiinflammatory cytokine that decreases production of IL-6 and IL-8. The authors hypothesized that diminished IL-6 and IL-8 and minimal inflammation may be caused by IL-10. Methods: To test this hypothesis, the authors developed a new syngeneic murine model of fetal wound repair in which 15-day-gestation skin from either normal C57BL/6 or transgenic C57BL/6 IL-10 knockout mice was grafted to the back of the same strain adult mice. The grafts were incisionally wounded after 5 days, harvested at 1 week, and analyzed for inflammatory response and scar formation. Results: Wounds in normal fetal skin grafts showed minimal inflammation and normal dermal reticular collagen pattern at the site of the wound, consistent with scarless repair. In contrast, wounds in IL-10 knockout fetal skin grafts showed significant inflammation and scar formation. Conclusions: Fetal skin grafts on adult syngeneic mice heal without inflammation or scar formation. The absence of IL-10 in fetal skin results in scar formation. Intrinsic lack of IL-10 may result in continued amplification of the inflammatory cytokine cascade, continued stimulation of fibroblasts, and abnormal collagen deposition. IL-10 is necessary for scarless wound repair to occur. J Pediatr Surg 35:866-873. Copyright © 2000 by W.B. Saunders Company.

Cytotoxicity testing through cell adhesion to a pattern of collagen matrix

A pattern of fluorescein isothiocyanate-labeled collagen (FITC-collagen) can be fabricated on a substrate; it is clearly observable by fluorescence microscopy. Human venous endothelial cells separately adhere only to the collagen islands. The stained cells and the collagen islands can be discriminately viewed by fluorescence microscopy with two filter sets. Zinc sulfate in the cell medium produces effects on the cell adhesion; it decreases the number of the cells anchored to the collagen islands, suggesting a new methodology of testing chemical cytotoxicity. The method could also be useful to understand cells’ growth, morphogenesis, differentiation, and death.

Laminin and collagen IV in pleomorphic adenoma and carcinoma ex-pleomorphic adenoma: An immunohistochemical study

Laminin and collagen have been studied in several tumor types and their immunomorphological expression correlated with tumor morphogenesis, local invasiveness, and metastatic behavior. In a series of 53 cases of pleomorphic adenomas (PA) and 16 cases of carcinomas ex-pleomorphic adenoma (Ca ex-PA), we investigated by immunohistochemistry the distribution pattern of laminin (lam) and collagen IV (col IV) at the basement membrane (BM) and the interstitial compartments, and their potential relationship with the metastatic behavior of Ca ex-PA. At the BM compartment, lam and col IV were expressed in 37 and 41 of all cases, respectively. In PA, there were lam and col IV around cell aggregates in 47.2% and 56.6% of the cases, respectively, and around isolated cells in 30.2% and 26.4%, respectively. In Ca ex-PA cases, both antigens were expressed in 56.3% and in 18.8% of the cases around cell aggregates and isolated cells, respectively. At the interstitial compartment, the fibro-hyaline matrix contained few lam in PA (19.2%) in contrast to Ca ex-PA (75%), including the benign areas of the neoplasms (90%), being the difference statistically significant ( P < .001). In the Ca ex-PA group, a statistically significant difference was found on col IV deposits around tumor cell aggregates between metastasizing and nonmetastasizing neoplasms ( P < .001). These findings support that laminin and collagen IV are involved in the process of malignant transformation of pleomorphic adenomas and their biological progression.

Spherulosis of the Breast

Abstract Objective.—Collagenous spherulosis of the breast is an uncommon localized pattern of basement membrane material deposition that may be mistaken for atypical proliferations or carcinoma. This report describes 9 cases in which the predominant or exclusive appearance of the spherules was basophilic instead of eosinophilic. Design.—The files of all cases of collagenous spherulosis diagnosed at the Armed Forces Institute of Pathology were reviewed to ascertain the frequency of diagnosis. Results.—Spherulosis with a predominantly basophilic pattern had a histochemical and immunohistochemical profile similar to collagenous spherulosis and was associated with more collagenous-appearing forms in 7 of 9 cases. Review of 81 cases showed that collagenous spherulosis was correctly diagnosed in 15% of referrals and was mistaken for intraductal or invasive carcinoma in 11% of cases. Conclusions.—Mucinous and collagenous patterns appear to be related forms of spherulosis. They are underrecognized by pathologists...

Spherulosis of the breast. A spectrum of municous and collagenous lesions.

Collagenous spherulosis of the breast is an uncommon localized pattern of basement membrane material deposition that may be mistaken for atypical proliferations or carcinoma. This report describes 9 cases in which the predominant or exclusive appearance of the spherules was basophilic instead of eosinophilic. The files of all cases of collagenous spherulosis diagnosed at the Armed Forces Institute of Pathology were reviewed to ascertain the frequency of diagnosis. Spherulosis with a predominantly basophilic pattern had a histochemical and immunohistochemical profile similar to collagenous spherulosis and was associated with more collagenous-appearing forms in 7 of 9 cases. Review of 81 cases showed that collagenous spherulosis was correctly diagnosed in 15% of referrals and was mistaken for intraductal or invasive carcinoma in 11% of cases. Mucinous and collagenous patterns appear to be related forms of spherulosis. They are underrecognized by pathologists and maybe mistaken for atypia or malignancy.

Spherulosis of the Breast

Abstract Objective.—Collagenous spherulosis of the breast is an uncommon localized pattern of basement membrane material deposition that may be mistaken for atypical proliferations or carcinoma. This report describes 9 cases in which the predominant or exclusive appearance of the spherules was basophilic instead of eosinophilic. Design.—The files of all cases of collagenous spherulosis diagnosed at the Armed Forces Institute of Pathology were reviewed to ascertain the frequency of diagnosis. Results.—Spherulosis with a predominantly basophilic pattern had a histochemical and immunohistochemical profile similar to collagenous spherulosis and was associated with more collagenous-appearing forms in 7 of 9 cases. Review of 81 cases showed that collagenous spherulosis was correctly diagnosed in 15% of referrals and was mistaken for intraductal or invasive carcinoma in 11% of cases. Conclusions.—Mucinous and collagenous patterns appear to be related forms of spherulosis. They are underrecognized by pathologists and maybe mistaken for atypia or malignancy.

Alterations of the extracellular matrix of venous walls in varicous veins.

Investigation of changes in normal veins which result in the formation of varicosis led to examination of the histological organisation of the vessel wall and to histomorphological alterations in the region of the extracellular matrix. The expression pattern of the matrix proteins collagen IV, fibronectin, laminin, tenascin, and undulin as well as the structure and orientation of elastic fibres were determined by means of immunohistochemical staining. All varices exhibited an increased expression pattern in comparison to healthy veins. The venous vessel wall was often non-homogeneously enlarged. The intima was always more involved than the media and showed enhanced accumulation, whereas, the adventitia was not influenced by the pathological process. Collagen IV exhibited an early accumulation, especially in the subendothelial region. The other matrix proteins demonstrated an increase in fibre propagation parallel to the enlargement of the vessel wall. Essentially, an augmented de novo synthesis of fibres with an irregular arrangement and the formation of local plaques was found. Elastic fibres were enhanced by slight involvement of the vessel wall and were reduced and fragmented during increased involvement of the venous wall which explained the rigidity of varices in contrast to normal veins.

A correlation between epithelial proliferation rates, basement membrane component localization patterns, and morphogenetic potential in the embryonic mouse lung.

Lung epithelial branching morphogenesis results from a repetitive series of cleft and bud formation, a process dependent upon a complex interaction with the surrounding mesenchyme. The present study describes these cleft- and bud-forming regions as autonomous morphogenetic compartments within the embryonic day 11.5 (E11.5) mouse lung and directly correlates their identity with differences in epithelial proliferation rates and the localization pattern of specific basement membrane components. Lung buds were cultured in vitro, in two-dimensional planes, and labeled with a series of 5-bromo-2'-deoxyuridine (BrdU) pulses. Collectively, epithelial cells within actively budding regions of the bronchiolar tree demonstrated an at least 2.5-fold greater proliferation rate than those situated in the adjacent cleft-forming regions. Epithelial proliferation rates showed an inverse relationship with the degree of immunoreactivity of nidogen, laminin-1, fibronectin, and collagen IV within the underlying basement membrane. Epithelial cells dissected free from mesenchyme demonstrated cell-cell contact-dependent proliferation, thus revealing a hierarchy between mesenchymal signaling and direct epithelial cell-cell communication during branch formation. Dissection of the E11.5 bronchiolar tree into specific distalbud and interbud regions and their in vitro culture demonstrated differences in their autonomous morphogenetic potential. Tissue dissected from the distal tips of the lung continued to branch, whereas tissue dissected from immediately adjacent cleft regions seldom branched. Isolated distalbud tissue also continued to correlate regional differences in epithelial proliferation rates and immunolocalization patterns of nidogen, laminin-1, fibronectin, and collagen IV with branch formation. These results support the basement membrane remodeling hypothesis, thus connecting nidogen, collagen type IV, fibronectin, and laminin-1 localization with the molecular processes directing epithelial proliferation and supporting bud outgrowth and cleft formation/stabilization during lung morphogenesis.

Structure of chordae tendineae in the left ventricle of the human heart.

The bicuspid (mitral) valve complex of the human heart consists of functional units which include the valve leaflets, chordae tendineae and the papillary muscles. The mechanical properties of these functional units depend to a large extent on the link between the muscle and the valve. This link is usually arranged in a branching network of avascular tendinous chordae composed of collagen and elastic fibres, which transmit contractions of the papillary muscle to the valve leaflets. In order to perform their function efficiently, the chordae have to possess a high degree of elasticity, as well as considerable strength and endurance. Human chordae tendineae originating from the left ventricles were obtained from 7 embalmed cadavers and 6 postmortem subjects of various ages. Samples washed in saline were fixed or postfixed in 9 % formol saline. Observations were made by illuminating the chordae along their axes. The reflected images originating from the superficial collagenous layers of the relaxed chordae showed a striped pattern 11 microm in width. Scanning electron and light microscopy of the chordae confirmed an undulating pattern of collagen fibrils arranged in bundles of planar waves in register and around the entire circumference of the chorda. The dimensions of the waves correlated with those of the striped reflected pattern. The observed undulating arrangement of the collagen fibrils appears to produce an inherent built-in elasticity which is likely to be of considerable advantage for a tissue which is under continuous repetitive stress. The chordae were covered by endocardium composed of a superficial layer of smooth squamous endothelial cells and an underlying dense layer of elastic fibres. It is suggested that the relaxed striped chordae, consisting of undulating collagen fibrils, straighten when the chordae become stretched by papillary muscle contraction, thereby mitigating the peak stress developed during muscle contraction. On relaxation the elastic tissue tends to return the collagen to its wavy configuration. It is also suggested that the regular wavy pattern of collagen seen in young individuals gradually changes with age by elongation of the wave pattern which eventually becomes randomised. In addition, with increasing age, substantial cushions of connective tissue appear below endocardium while the dense collagenous core has a reduced cross-sectional area which may lead to stretching and eventual rupture of the chordae.

Inhibition of Chondrogenesis by Integrin Antibodyin Vitro

Integrins mediate cell attachment to a variety of extracellular matrix proteins. These interactions play an important role in morphogenesis and differentiation. The mediating functions of integrins during chondrogenesisin vitrowere investigated by using mesenchymal cells from limb buds of day 12 mouse embryos. The cells were treated with anti-β1, -α1, and -α5 integrin antibodies (a) from day 1 to day 3 and (b) from day 3 to day 7 of cultivation. The total culture period was 7 days. The presence of exogenous anti-β1, but not -α1 and -α5 integrin antibodies, from day 1 to 3 completely inhibited the differentiation of blastemal cells to chondroblasts and the formation of cartilage matrix. On the other hand, the presence of exogenous anti-β1, -α1, and -α5 integrin antibodies from day 3 of cultivation onwards had no effect. Immunoblotting and immunomorphological findings in the cultures treated with anti-β1 antibody from day 1 to day 3 revealed a pattern of integrins and collagen composed of β1, α1, α5β1 integrins and collagen type I. The cartilage-specific chondroitin sulfate proteoglycan (CSPG) could not be demonstrated in these cultures. The cultures treated later (day 3 to day 7) showed a pattern of β1, α3, α5β1, and αvβ3 integrins, collagen types I and II, and CSPG identical to that of the untreated controls. These findings indicate that β1-integrins play a crucial role in early cartilage differentiation and point to a possible important cell–matrix interaction in the induction of chondrogenesis.

Localization patterns of collagens during growth of human scalp hair

Localization patterns of collagens during growth of human scalp hair