Micro- and nano-CT for the study of bone ultrastructure

Micro-computed tomography (micro-CT)-a version of X-ray CT operating at high spatial resolution-has had a considerable success for the investigation of trabecular bone micro-architecture. Currently, there is a lot of interest in exploiting CT techniques at even higher spatial resolutions to assess bone tissue at the cellular scale. After recalling the basic principles of micro-CT, we review the different existing system, based on either standard X-ray tubes or synchrotron sources. Then, we present recent applications of micro- and nano-CT for the analysis of osteocyte lacunae and the lacunar-canalicular network. We also address the question of the quantification of bone ultrastructure to go beyond the sole visualization.

A novel poly(amido amine)-dendrimer-based hydrogel as a mimic for the extracellular matrix

The extracellular matrix is mimicked by a novel dendrimer-based hydrogel, which exhibits a highly interconnected porous network, enhanced mechanical stiffness, and a low swelling ratio. The hydrogel system supports the proliferation and differentiation of mesenchymal stem cells without any cytotoxic effects. This dendrimer-based hydrogel may serve as a model for developing new advanced materials with applications in tissue engineering.

Mammographic density: intersection of science, the law, and clinical practice

High mammographic density is associated with a two- to sixfold increased risk of breast cancer. Mammographic density can be altered by endogenous and exogenous hormonal factors and generally declines with age. Mammographic density is affected by confounding factors such as age, parity, menopausal status, and body mass index (BMI), thus making interpretation of mammographic density challenging. None of the established means of measuring mammographic density are entirely satisfactory because they are time consuming and/or subjective. Although mammographic density has been shown to predict breast cancer risk, the role of mammographic density in precisely assessing a woman's breast cancer risk over her lifetime and evaluating response to risk-reduction strategies cannot be fully realized until we have a better understanding of the biology that links mammographic density to breast cancer risk.

Ultrasonic assessment of extracellular matrix content in healing Achilles tendon

Although several imaging modalities have been utilized to observe tendons, assessing injured tendons by tracking the healing response over time with ultrasound is a desirable method which is yet to be realized. This study examines the use of ultrasound for non-invasive monitoring of the healing process of Achilles tendons after surgical transection. The overall extracellular matrix content of the transection site is monitored and quantified as a function of time. B-mode images (built from successive A-scan signatures) of the injury site were obtained and compared to biomechanical properties. A quantitative measure of tendon healing using the extracellular matrix (ECM) content of the injury site was analyzed using linear regression with all biomechanical measures. Contralateral tendons were used as controls. The trend in the degree of ECM regrowth in the 4 weeks following complete transection of excised tendons was found to be most closely paralleled with that of linear stiffness (R(2) = 0.987, p < .05) obtained with post-ultrasound biomechanical tests. Results suggest that ultrasound can be an effective imaging technique in assessing the degree of tendon healing, and can be used to correlate structural properties of Achilles tendons.

Biomimetic approach to perforation repair using dental pulp stem cells and dentin matrix protein 1

INTRODUCTION

Dentin regeneration could be an ideal treatment option to restore tissue function. This study was conducted to evaluate the ability of dental pulp stem cells (DPSCs) and dentin matrix protein 1 (DMP1) impregnated within a collagen scaffold to regenerate dentin.

METHODS

Simulated perforations were created in 18 dentin wafers made from freshly extracted human molars. Six groups were established. They were (1) empty wafers, (2) mineral trioxide aggregate, (3) collagen scaffold, (4) scaffold with DMP1, (5) scaffold with DPSCs, and (6) scaffold with DPSCs and DMP1. One sample was placed subcutaneously in each mouse with three mice in each group. After 12 weeks, the samples were subjected to radiographic, histological, and immunohistochemical evaluations.

RESULTS

DPSCs impregnated within a collagen scaffold differentiated into odontoblast-like cells forming a highly cellular, vascular, and mineralized matrix in the presence of DMP1.

CONCLUSIONS

A triad consisting of DPSCs, DMP1, and a collagen scaffold promotes dentin regeneration in a simulated perforation repair model.

Ultrasound anatomy of normal nails unit with 18 mhz linear transducer

Interest is growing in non-invasive diagnostic methods for nails in dermatological pathology. Currently, nail disease diagnosis is based mostly on clinical evaluation; instrumental examination, traditionally, has been performed by magnetic resonance. Ultrasound (US) can be proposed as an easier and more available method for the study of the nail apparatus. In this study, the nail unit normal ultrasound anatomy was investigated to obtain data on adult normal parameters. On 35 healthy volunteers (20 women and 15 men--average age of 27 years) we performed an ultrasonographic study on the nail plate (dorsal and ventral), nail matrix and nail bed of all fingers of the hands using a 18 MHz linear transducer with Esaote Mylab 50. A thick gel layer allowed for appropriate transmission of ultrasound without any additional device. Macroscopic nail features were studied by clinical examination and photographic analysis. The following ultrasound parameters were investigated: nail thickness; nail bed thickness; matrix lenght; matrix-bone distance. Blood flow was studied with the use of colour and power colour Doppler. The nail apparatus echographic anatomy consists in: (a) nail plate, represented by two hyperechoic bands (dorsal and ventral) with an hypoechoic or anechoic space between them; (b) nail bed, represented by an area of dys-homogeneous hypo-echogeneity; (c) nail matrix, represented by a markedly hypoechoic area corresponding to the region under the nail sulcus; (d) ligaments, sometimes well detectable and formed by a specialized connective tissue; and (e) vessels, well evaluable through doppler examination.

Quantifying the 3D macrostructure of tissue scaffolds

The need to shift from tissue replacement to tissue regeneration has led to the development of tissue engineering and in situ tissue regeneration. Both of these strategies often employ the use of scaffolds--templates that allow cells to attach and then guide the new tissue growth. There are many design criteria for an ideal scaffold. These criteria vary depending on the tissue type and location in the body. In any application of a scaffold it is vital to be able to characterise the scaffold before it goes into in vitro testing. In vitro testing allows the cell response to be investigated before its in vivo performance is assessed. A full characterisation of events in vitro and in vivo, in three dimensions (3D), is necessary if a scaffold's performance and effectiveness is to be fully quantified. This paper focuses on porous scaffolds for bone regeneration, suggests appropriate design criteria for a bone regenerating scaffold and then reviews techniques for obtaining the vitally important quantification of its pore structure. The techniques discussed will include newly developed methods of quantifying X-ray microtomography (microCT) images in 3D and for predicting the scaffolds mechanical properties and the likely paths of fluid flow (and hence potential cell migration). The complications in investigating scaffold performance in vitro are then discussed. Finally, the use of microCT for imaging scaffolds for in vivo tests is reviewed.

[Chondromas (enchondroma, periosteal chondroma, enchondromatosis)]

Chondromas combine a group of benign cartilaginous tissue tumors with common histological manifestations. The tumors (enchondroma, periosteal chondroma, and enchondromatosis) differ in sites and clinical manifestations. Chondromas are generally hypocellular, avascular tumors with an abundance of hyaline cartilage matrix and chondrocytes located diffusely, in clones or lobules. Small bone chondromas, Ollier's disease, and Mafucci's syndrome are characterized by the tumor tissue containing a large number of cells and by greater cytological atypia. Enchondroma is successfully treated by surgical methods.

Intermittent applications of continuous ultrasound on the viability, proliferation, morphology, and matrix production of chondrocytes in 3D matrices

Chondrocytes, the cellular component of the articular cartilage, have long been recognized as strain-sensitive cells, and have the ability to sense mechanical stimulation through surface receptors and intracellular signaling pathways. This strain-induced biological response of chondrocytes has been exploited to facilitate chondrocyte culture in in vitro systems; examples include the application of hydrostatic pressure, dynamic compression, hydrodynamic shear (i.e., rotating bioreactors), and low-intensity pulsed ultrasound (US). While the ability of US to influence chondrogenesis has been documented, the precise mechanisms of US-induced stimulation continue to be investigated. There remains a critical need to evaluate the impact of US on chondrocytes in 3D culture, which is a necessary microenvironment for maintaining the chondrocyte phenotype. In this study, a continuous US wave for predetermined time intervals was employed, as opposed to pulsed US used in previous studies, to stimulate chondrocytes seeded in 3D scaffolds. The chondrocytes (n = 6) were subjected to US stimulation as follows: 1.5 MHz for 161 seconds, 5.0 MHz for 51 seconds, and 8.5 MHz for 24 seconds, and the US signal was applied twice in a 24-hour period. Scaffolds that are not stimulated by US served as the control. Both the control and the US-stimulated groups were maintained in culture for 10 days, and at the conclusion of the culture period, chondrocytes were assayed for total DNA content, morphology, and cartilage-specific gene expression by reverse transcriptase polymerase chain reaction. Our results show that chondrocytes when stimulated with continuous US for predetermined time intervals possessed higher cellular viability (1.2 to 1.4 times) and higher levels of type II collagen and aggrecan mRNA expression when compared to controls.

Molecular-functional imaging of cancer: to image and imagine

The integration of advances in molecular biology, synthetic chemistry and visualization techniques has catapulted imaging into a molecular-functional realm, so that imaging is finding basic-research, preclinical and translational applications in cancer. Currently, molecular-imaging capabilities include the ability to image gene expression, receptors, signaling pathways, apoptosis, multidrug resistance and the extracellular matrix (ECM). Functional-imaging capabilities include the ability to assess angiogenesis, hypoxia and metabolism. Traditionally, imaging has played an important role in cancer diagnosing and determining response to treatment. However, it is the realization of the goal of noninvasively visualizing molecules and molecular pathways and relating these to function that makes multi-modality imaging such an exciting and powerful means for studying a multifaceted disease such as cancer.

Quantitative monitoring of extracellular matrix production in bone implants by 13C and 31P solid-state nuclear magnetic resonance spectroscopy

We used (31)P and (13)C solid-state nuclear magnetic resonance (NMR) spectroscopy to detect and analyze the major organic and inorganic components (collagen type I and bioapatite) in natural rabbit bone and beta-tricalcium phosphate implants loaded with osteogenically differentiated mesenchymal stem cells. High-resolution solid-state NMR spectra were obtained using the magic-angle spinning (MAS) technique. The (31)P NMR spectra of bone specimens showed a single line characteristic of bone calcium phosphate. (13)C cross-polarization (CP) MAS NMR spectra of bone exhibited the characteristic signatures of collagen type I with good resolution for all major amino acids in collagen. Quantitative measurements of (13)C-(1)H dipolar couplings indicated that the collagen segments are very rigid, undergoing only small amplitude fluctuations with correlation times in the nanosecond range. In contrast, directly polarized (13)C MAS NMR spectra of rabbit bone were dominated by signals of highly mobile triglycerides. These quantitative investigations of natural bone may provide the basis for a quality control of various osteoinductive bone substitutes. We studied the formation of extracellular bone matrix in artificial mesenchymal stem cell-loaded beta-tricalcium phosphate matrices that were implanted into the femoral condyle of rabbits. The NMR spectra of these bone grafts were acquired 3 months after implantation. In the (31)P NMR spectra, beta-tricalcium phosphate and bone calcium phosphate could be distinguished quantitatively, allowing recording of the formation of the natural bone matrix. Further, (13)C CPMAS allowed detection of collagen type I that had been produced in the implants. Comparison with the spectroscopic data from natural bone allowed assessment of the quality of the bone substitute material.

Maturation-dependent change and regional variations in acoustic stiffness of rabbit articular cartilage: an examination of the superficial collagen-rich zone of cartilage

OBJECTIVE

The purpose of the study was to investigate maturation-dependent changes of acoustic (ultrasound) stiffness and other ultrasound features of articular cartilage in healthy rabbit knees.

METHODS

Five groups of rabbits of various ages (3 weeks, 8 weeks, 6 months, 1 year, 2.5 years) consisting of five rabbits per group were examined. Signal intensity (index of stiffness), signal duration (index of surface irregularity) and interval between signals (index of thickness) of the ultrasound reflection from articular cartilage were examined at four sites: posterior lateral femoral condyle, posterior medial femoral condyle, lateral tibial plateau, and medial tibial plateau. The sites were observed macroscopically and microscopically with a light microscope and a polarized light microscope.

RESULTS

At the lateral and medial condyles and the lateral tibial plateau, signal intensity was least in 3-week-old specimens. The intensity increased until 6 months or 1 year of age. At these sites, the signal durations and intervals between signals were least at the ages of 6 months or 1 year. At the medial tibial plateau, the intensity was the least at 2.5 years of age and the interval between signals was least at 3 weeks of age; there was no effect of age on signal duration. Cartilage surfaces of all specimens were smooth and no degenerative changes were macroscopically or microscopically evident. The surface brightness of cartilage under the polarized light microscope was consistent with signal intensity values.

CONCLUSIONS

The response of articular cartilage to ultrasound was maturation-dependent. Acoustic properties differed from mechanical stiffness properties, which were determined using indentation. Ultrasound may detect properties of the surface collagen of the articular cartilage.

Affine versus non-affine fibril kinematics in collagen networks: theoretical studies of network behavior

The microstructure of tissues and tissue equivalents (TEs) plays a critical role in determining the mechanical properties thereof. One of the key challenges in constitutive modeling of TEs is incorporating the kinematics at both the macroscopic and the microscopic scale. Models of fibrous microstructure commonly assume fibrils to move homogeneously, that is affine with the macroscopic deformation. While intuitive for situations of fibril-matrix load transfer, the relevance of the affine assumption is less clear when primary load transfer is from fibril to fibril. The microstructure of TEs is a hydrated network of collagen fibrils, making its microstructural kinematics an open question. Numerical simulation of uniaxial extensile behavior in planar TE networks was performed with fibril kinematics dictated by the network model and by the affine model. The average fibril orientation evolved similarly with strain for both models. The individual fibril kinematics, however, were markedly different. There was no correlation between fibril strain and orientation in the network model, and fibril strains were contained by extensive reorientation. As a result, the macroscopic stress given by the network model was roughly threefold lower than the affine model. Also, the network model showed a toe region, where fibril reorientation precluded the development of significant fibril strain. We conclude that network fibril kinematics are not governed by affine principles, an important consideration in the understanding of tissue and TE mechanics, especially when load bearing is primarily by an interconnected fibril network.

[Alterations in the structure of the epiretinal membranes in PVR -- assumptions and reality]

BACKGROUND

Proliferative vitreoretinopathy (PVR) is known to be the main cause of failure for routine retinal detachment surgery. Our aim was to document the ultrastructural changes in the epiretinal membranes in cases of PVR.

MATERIAL AND METHODS

Epiretinal membranes were taken during vitrectomy of 64 patients with different stages of PVR and further analysed using transmission and scanning electron microscopy.

RESULTS

In the early stages of the disease mainly retinal pigment epithelial (RPE) cells, fibroblasts and occasional glial cells were found. Moreover, some of the RPE cells showed altered characteristics. In contrast, epiretinal membranes from the developed stages of PVR were comprised mostly of fibroblasts and a considerably diminished number of RPE cells. Cells with marks of degeneration were generally found.

CONCLUSIONS

Our results point out that epiretinal membranes in PVR are dynamic structures, constantly changing their cell and matrix composition with the progression of the disease. The morphological changes together with the clinical data are important points to consider when discussing the most appropriate therapeutic approach for each case.

Radiographic correlation in orthopedic pathology

Radiographic correlation is an essential adjunct for the accurate diagnosis of orthopedic lesions, yet it is a skill neglected by pathologists. The purpose of this review is to demonstrate why performing this correlation is an essential part of the diagnostic process and not merely an interesting adjunct to the surgical pathology of orthopedic lesions. The relationships between x-rays and tissues are explored with an emphasis on bone and soft tissue composition and structure. In addition, the rudiments of complementary imaging studies and how to incorporate their data into diagnoses are examined.

Maturation and Integration of Tissue-Engineered Cartilages within anin VitroDefect Repair Model

This study compared the behavior of four different engineered cartilages in a hybrid culture system. First, the growth and maturation of tissue-engineered cartilages in isolation were compared to those grown in an in vitro articular cartilage defect repair model. Tissue-engineered cartilages using fibrin, agarose, or poly(glycolic acid) scaffolds were implanted into annular explants of articular cartilage and cultured for 20 or 40 days. Native tissue had a substantial influence on the DNA, sulfated glycosaminoglycan, and hydroxyproline content of the engineered tissues, suggesting that the presence of living tissue in the culture significantly altered cell proliferation and matrix accumulation. Second, the adhesion strength of various engineered cartilages to native tissue was measured and compared with the biochemical content of the engineered tissues. All scaffold treatments adhered to the native cartilage, but there were statistically significant differences in adhesive strength between the different scaffolds. The adhesive strength of all engineered scaffolds was significantly lower than that of native tissue to itself. In the engineered tissues, neither failure stress nor energy to failure correlated with gross biochemical content, suggesting that adhesion between native and engineered tissues is not purely a function of gross matrix synthesis.

Targeting Metastatic Prostate Cancer With Radiolabeled Monoclonal Antibody J591 to the Extracellular Domain of Prostate Specific Membrane Antigen

PURPOSE

We performed an interim analysis of imaging data collected in 2 phase I radioimmunotherapy trials to determine the ability of monoclonal antibody (mAb) J591 directed to the extracellular domain of prostate specific membrane antigen (PSMA) to target sites of known metastatic prostate cancer accurately.

MATERIALS AND METHODS

Patients with progressing hormone independent prostate cancer were entered in 2 phase I dose finding trials with radiolabeled mAb J591. J591 is the first mAb targeting the extracellular domain of PSMA as well as the first de-immunized (humanized) mAb to PSMA to be tested in humans. These trials were primarily designed to assess dose limiting toxicity, maximum tolerated dose, pharmacokinetics and organ dosimetry. Planar gamma camera imaging studies obtained on the first 53 patients were reviewed and compared to sites of metastatic prostate cancer visualized on conventional imaging studies including bone scan, computerized tomography and/or magnetic resonance imaging. In 1 trial 29 patients received 111indium-J591 for imaging followed by 90yttrium-J591 for therapy. In the parallel trial 24 patients were treated with 177lutetium-J591, an isotope that can be imaged directly.

RESULTS

Of 53 patients reviewed 46 (87%) had evidence of metastatic disease on conventional scans. Overall, of the 43 evaluable patients J591 accurately targeted bone and/or soft tissue lesions in 42 (98%). J591 accurately targeted bone lesions in 32 of 34 (94%) and soft tissue lesions in 13 of 18 (72%) evaluable patients.

CONCLUSIONS

Radiolabeled J591 accurately targets bone and soft tissue metastatic prostate cancer sites, and may be useful for targeting therapeutic and/or diagnostic imaging agents.

The extracellular matrix is an important source of ultrasound backscatter from myocardium

Ultrasound tissue characterization with measurement of backscatter has been employed in numerous experimental and clinical studies of cardiac pathology, yet the cellular components responsible for scattering from cardiac tissues have not been unequivocally identified. This laboratory has proposed a mathematical model for myocardial backscatter that postulates the fibrous extracellular matrix (ECM) as a significant determinant of backscatter. To demonstrate the importance of ECM, this group sought to determine whether measurements of backscatter from the isolated ECM could reproduce the known directional dependence, or anisotropy of backscatter, from intact cardiac tissues in vitro. Segments of left ventricular free wall from ten formalin fixed porcine hearts were insonified at 50 MHz, traversing the heart wall from endo- to epicardium to measure the anisotropy of myocardial backscatter, defined as the difference between peak (perpendicular to fibers) and trough (parallel to fibers) backscatter amplitude. The tissue segments were then treated with 10% NaOH to dissolve all of the cellular components, leaving only the intact ECM. Scanning electron micrographs (SEM) were obtained of tissue sections to reveal complete digestion of the cellular elements. The dimensions of the residual voids resulting from cell digestion were approximately the diameter of the intact myocytes (10-30 microm). These samples were reinsonified after seven days of treatment to compare the anisotropy of integrated backscatter. The magnitude of anisotropy of backscatter changed from 15.4 +/- 0.8 to 12.6 +/- 1.1dB for intact as compared with digested specimens. Because digestion of the myocardium leaves only extracellular sources of ultrasonic scattering, and because the isolated ECM exhibits similar ultrasonic anisotropy as does the intact myocardium, it is concluded that there is a direct association between the ECM and the anisotropy of backscatter within intact tissue. Thus, it is suggested that ultrasonic tissue characterization represents a potentially clinically applicable method for delineating the structure and function of the ECM.

Morphological classification of nuchal skin in human fetuses with trisomy 21, 18, and 13 at 12-18 weeks and in a trisomy 16 mouse

An increase in the nuchal translucency that can be detected at 10-14 weeks of gestation by ultrasound forms the basis for a screening test for chromosomal abnormality. Several mechanisms leading to this increase in skin thickness have been proposed, including changes of the extracellular matrix, cardiac defects and abnormalities of the large vessels. This study examines the composition of the extracellular matrix of the skin in gestational age-matched fetuses with trisomy 21, 18 and 13 from 12-18 weeks. Immunohistochemistry was applied with monoclonal and polyclonal antibodies against collagen type I, III, IV, V and VI and against laminin and fibronectin. Collagen type VI gene expression was further studied by in situ hybridization to detect differences in expression patterns of COL6A1, COL6A3 and COL1A1 between normal fetuses and those with trisomy 21. The ultrastructure of tissue samples was studied by transmission electron microscopy (TEM) and additionally by immunogold TEM. Further, we examined the morphology of the skin in an animal model for Down's syndrome, the murine trisomy 16, by light and TEM. The dermis of trisomy 21 fetuses was richer in collagen type VI than that of normal fetuses and other trisomies, and COL6A1, located on chromosome 21, was expressed in a wider area than COL6A3, which is located on chromosome 2. Collagen type I was less abundant in the skin of trisomy 18 fetuses, while the skin of all three trisomies contained a dense network of collagen type III and V in comparison with normal fetuses. Collagen type IV, of which two genes are located on chromosome 13, was expressed in the basement membranes of the skin in all fetuses and additionally in the dermal fibroblasts only of trisomy 13 fetuses. Likewise, laminin was present in all basement membranes of normal and trisomic fetuses as well as in dermal fibroblasts of fetuses with trisomy 18. LAMA1 and LAMA3 genes are located on chromosome 18. Dermal cysts were found in the skin of trisomy 18 and 13, but not in trisomy 21 and normal fetuses. Ultrastructural findings showed that an extracellular precipitate containing glycosaminoglycans was regularly present in the skin of trisomy 21 fetuses and murine trisomy 16 embryos. In conclusion, this study suggests that the skin edema in fetal trisomies is characterized by specific alterations of the extracellular matrix that may be attributed to gene dosage effects as a result of a genetic imbalance due to the condition of fetal trisomy.

Effect of bovine bone constituents on broadband ultrasound attenuation measurements

Broadband ultrasound attenuation (BUA) has been found to correlate positively with bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. However, because there is a significant amount of unexplained variation in this correlation, it has been suggested that BUA might also provide information about bone structure. The purpose of this study was to determine the contribution of bone mineral and organic matrix to BUA and BMD measurements. The influence of sample length on both BUA and BMD was also investigated by normalizing these measurements to length. BUA (Walker Souix, 575+) and BMD (Lunar DPX) values were obtained on bicortical cores removed from 12 bovine femoral necks. BMD and BUA measurements were repeated on the samples after: (1) mechanical removal of the cortices; (2) defatting using a 2:1 chloroform:methanol solution; and (3) decalcifying using formic acid. The data demonstrate that the cortical component of the bone contributes significantly to BMD. We found that 41.7% of the normalized BMD reflect cortical bone. Defatting the samples did not affect BUA. Decalcifying the trabecular bone while maintaining an intact collagenous structure significantly reduces BUA by 89% and BMD by 96% compared to the whole core samples. Normalizing BMD and BUA to sample length, in cases where large variation is present, does influence the correlation between the variables. We conclude that BUA is influenced mainly by the presence of bone mineral, whereas the presence of the organic matrix contributes very little to BUA.

Deposition of extracellular matrix on silicone intraocular lens implants in rabbits

PURPOSE

To examine the deposition of extracellular matrix on silicone intraocular lenses (IOLs) implanted experimentally into rabbit eyes by electron microscopy and to determine the immunolocalization of extracellular matrix components, including collagen types and cellular fibronectin, on these IOLs.

METHODS

We performed phacoemulsification and aspiration of the crystalline lens and implanted a foldable silicone IOL in the capsular bag of one eye of each of 26 adult albino rabbits under general anesthesia. After 8 weeks the animals were killed and the eyes were enucleated. The silicone IOLs were processed for electron microscopy and for immunohistochemical detection of collagen types I, III, and IV and cellular fibronectin.

RESULTS

Electron microscopy revealed deposition of a presumed cell matrix complex on the optic portion of all silicone IOLs, as well as the adhesion of presumed macrophages and foreign-body giant cells. Cellular deposits showed immunoreactivity for cellular fibronectin. Fibrous or membranous deposits exhibited immunoreactivity for cellular fibronectin and collagen types I and III. A few type IV collagen-immunoreactive deposits were also seen.

CONCLUSION

Deposits of extracellular matrix components were observed on silicone IOLs. These deposits may form the scaffolding for the adhesion and proliferation of cells. These matrix components appeared to be the products of cells adhering to the surfaces of IOLs, including lens epithelial cells, macrophages and foreign-body giant cells, indicating that the process of granulation was incomplete.