Cryopreserved human amniotic membrane for ocular surface reconstruction

Proteomic analysis of equine amniotic membrane: characterization of proteins

INTRODUCTION

Human amniotic membrane (AM) has been used as a biomaterial for surgical wound skin and ocular surface reconstruction for several years. Currently, equine AM has been used for corneal reconstruction in several animal species, and appears to have the same properties as human AM. Despite the observed positive healing abilities of this tissue in horses with ulcerative keratitis the proteins of equine AM have not been described.

OBJECTIVE

To identify proteins known to be associated with corneal healing from frozen equine AM.

PROCEDURES

Placentas were acquired from healthy live foal births from a local Thoroughbred breeding farm. The amnion was removed from the chorion by blunt dissection, washed with phosphate-buffered saline (PBS), and treated with 0.05% trypsin and 0.02% ethylene diaminetetraacetic acid in PBS. Amnion was attached to nitrocellulose paper (epithelial side up), and cut into 4 × 4 cm pieces. The sheets were frozen at -80 °C. The protein samples were solubilized, and analyzed by 2D gel electrophoresis and shotgun proteomics.

RESULTS

A reference identification map of the equine AM proteins was produced and 149 different proteins were identified. From gel-based proteomics, 49 spots were excised and 43 proteins identified by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Shotgun proteomics identified 116 proteins with an overlap of 10 proteins in both analyses.

CONCLUSIONS

We have described a reference map for equine AM proteins that may provide a background to explain the positive results found in horses with ulcerative keratopathies using this biomaterial.

Human amniotic membrane transplantation: Different modalities of its use in ophthalmology

The amniotic membrane (AM) is the inner layer of the fetal membranes and consist of 3 different layers: the epithelium, basement membrane and stroma which further consists of three contiguous but distinct layers: the inner compact layer, middle fibroblast layer and the outermost spongy layer. The AM has been shown to have anti-inflammatory, anti-fibrotic, anti-angiogenic as well as anti-microbial properties. Also because of its transparent structure, lack of immunogenicity and the ability to provide an excellent substrate for growth, migration and adhesion of epithelial corneal and conjunctival cells, it is being used increasingly for ocular surface reconstruction in a variety of ocular pathologies including corneal disorders associated with limbal stem cell deficiency, surgeries for conjunctival reconstruction, as a carrier for ex vivo expansion of limbal epithelial cells, glaucoma surgeries and sceral melts and perforations. However indiscriminate use of human AM needs to be discouraged as complications though infrequent can occur. These include risk of transmission of bacterial, viral or fungal infections to the recipient if the donors are not adequately screened for communicable diseases, if the membrane is not processed under sterile conditions or if storage is improper. Optimal outcomes can be achieved only with meticulous case selection. This review explores the ever expanding ophthalmological indications for the use of human AM.

Storage and qualification of viable intact human amniotic graft and technology transfer to a tissue bank

Human amniotic membrane (hAM) is known to have good potential to help the regeneration of tissue. It has been used for over 100 years in many medical disciplines because of its properties, namely a scaffold containing stem cells and growth factors, with low immunogenicity and anti-microbial, anti-inflammatory, anti-fibrotic and analgesic properties. In order to use this "boosted membrane" as an advanced therapeutic medicinal product for bone repair, we aimed to observe the influence of tissue culture and/or cryopreservation on cell viability and tissue structure, and secondly, to adapt to a tissue bank, identify easy processes to store hAM containing viable cells and to verify the quality of the graft before its release for use. To this end, we tested different published culture or cryopreservation storage conditions and cell viability assays. Tissue structure was evaluated by Giemsa staining and was compared to histological analysis. Preliminary results show no dramatic decrease in cell viability in cultured hAM as compared to cryopreserved hAM, but tissue structure alterations were observed with both storage conditions. Histological and immunohistochemical data highlight that tissue damage was associated with significantly modified protein expression, which could lead to a possible loss of differentiation potential. Finally, we report that trypan blue and Giemsa staining could constitute controls that are "materially and easily transferable" to a tissue bank.

Preparation, indications and results of human amniotic membrane transplantation for ocular surface disorders

In comparison with other biologic tissues used as reconstructive grafts, the amniotic membrane has the advantage that it is thinner and better tolerated by the patient. Amniotic membrane, when appropriately preserved, can be used as a substrate replacement, such that host cells can migrate into the membrane to form new and healthy tissue. The amniotic membrane is the deeper layer of the fetal membrane; it is avascular, multilayered tissue with antiangiogenic, antiscarring and anti-inflammatory properties. Since it does not express antigens of histocompatibility, the membrane is never rejected by the receiving tissues. In addition, the beneficial effects of reducing inflammation and neovascularization persist for a long time, if properly cryopreserved.

Amniotic membrane properties and current practice of amniotic membrane use in ophthalmology in Slovenia

Amniotic membrane (AM) is the innermost, multilayered part of the placenta. When harvested, processed and stored properly, its properties, stemming from AM biological composition, make it a useful tissue for ophthalmic surgery. AM was shown to have several beneficial effects: it promotes epithelization, has antimicrobial effects, decreases inflammation, fibrosis and neovascularization. Many case reports and case series as well as practical experience (e.g. reconstruction of conjunctival and corneal defects, treatment of corneal ulcers) demonstrated the beneficial effect of AM for different ophthalmological indications. The combination of the above mentioned beneficial effects and reasonable mechanical properties are also the reason why AM is used as a substrate for ex vivo expansion of epithelial progenitor cells. Recently, amnion-derived cells, which also have stem cell characteristics, have been proposed as potential contributors to cell-based treatment of ocular surface disease. However, the use of AM remains one of the least standardized methods in ophthalmic surgery. In this review, the various properties of AM and its current clinical use in ophthalmology in Slovenia are discussed.

A simple alkaline method for decellularizing human amniotic membrane for cell culture

Human amniotic membrane is a standard substratum used to culture limbal epithelial stem cells for transplantation to patients with limbal stem cell deficiency. Various methods were developed to decellularize amniotic membrane, because denuded membrane is poorly immunogenic and better supports repopulation by dissociated limbal epithelial cells. Amniotic membrane denuding usually involves treatment with EDTA and/or proteolytic enzymes; in many cases additional mechanical scraping is required. Although ensuring limbal cell proliferation, these methods are not standardized, require relatively long treatment times and can result in membrane damage. We propose to use 0.5 M NaOH to reliably remove amniotic cells from the membrane. This method was used before to lyse cells for DNA isolation and radioactivity counting. Gently rubbing a cotton swab soaked in NaOH over the epithelial side of amniotic membrane leads to nearly complete and easy removal of adherent cells in less than a minute. The denuded membrane is subsequently washed in a neutral buffer. Cell removal was more thorough and uniform than with EDTA, or EDTA plus mechanical scraping with an electric toothbrush, or n-heptanol plus EDTA treatment. NaOH-denuded amniotic membrane did not show any perforations compared with mechanical or thermolysin denuding, and showed excellent preservation of immunoreactivity for major basement membrane components including laminin α2, γ1-γ3 chains, α1/α2 and α6 type IV collagen chains, fibronectin, nidogen-2, and perlecan. Sodium hydroxide treatment was efficient with fresh or cryopreserved (10% dimethyl sulfoxide or 50% glycerol) amniotic membrane. The latter method is a common way of membrane storage for subsequent grafting in the European Union. NaOH-denuded amniotic membrane supported growth of human limbal epithelial cells, immortalized corneal epithelial cells, and induced pluripotent stem cells. This simple, fast and reliable method can be used to standardize decellularized amniotic membrane preparations for expansion of limbal stem cells in vitro before transplantation to patients.

Amniotic membrane scaffolds enable the development of tissue-engineered urothelium with molecular and ultrastructural properties comparable to that of native urothelium

The amniotic membrane (AM) is a naturally derived biomaterial that possesses biological and mechanical properties of great importance for tissue engineering. The aim of our study was to determine whether the AM enables the formation of a normal urinary bladder epithelium-urothelium--and to reveal any differences in the urothelial cell (UC) growth and differentiation when using different AM scaffolds. Cryopreserved human AM was used as a scaffold in three different ways. Normal porcine UCs were seeded on the AM epithelium (eAM), denuded AM (dAM), and stromal AM (sAM) and were cultured for 3 weeks. UC growth on AM scaffolds was monitored daily. By using electron microscopy, histochemical and immunofluorescence techniques, we here provide evidence that all three AM scaffolds enable the development of the urothelium. The fastest growth and the highest differentiation of UCs were demonstrated on the sAM scaffold, which enables the development of tissue-engineered urothelium with molecular and ultrastructural properties comparable to that of the native urothelium. Most importantly, the highly differentiated urothelia on the sAM scaffolds provide important experimental models for future drug delivery studies and developing tissue engineering strategies considering that subtle differences are identified before translation to the clinical settings.

Effect of cryopreserved amniotic membrane on the development of adhesions and fibrosis after extraocular muscle surgery in rabbits

PURPOSE

To histopathologically evaluate the effect of cryopreserved human amniotic membrane (AM) transplant on preventing the development of postoperative adhesions after extraocular muscle surgery.

METHODS

Ten albino rabbits were used. The superior rectus muscles were bilaterally resected. In right eyes, the muscle was wrapped with cryopreserved human AM (group AM). In left eyes, the muscle was not wrapped with AM and served as a control group (group C). The rabbits were killed, and the eyes were enucleated 6 weeks after surgery to perform histopathological examination.

RESULTS

On histopathological examination, the AM was present in eight eyes, surrounded by periamniotic inflammation, with no adhesions detected between rectus muscle and sclera, conjunctiva and Tenon's capsule in the segment where the AM was present, but detected elsewhere. Adhesions were detected in the other two eyes of group AM, in which the AM was absent, and in all group C eyes. When comparing eye pairs of each rabbit, AM eyes showed significantly less adhesions between the muscle and sclera (p = 0.009) and between the muscle and Tenon's capsule and conjunctiva (p = 0.008), in the region of AM application, and significantly more foreign body inflammation (p = 0.031), than C eyes. The differences between AM and C eye pairs, in terms of conjunctival inflammation and vascularity and muscle fibrosis, were insignificant (p > 0.05).

CONCLUSIONS

Cryopreserved AM is effective in reducing postoperative extraocular muscle adhesions. Its application is, therefore, recommended during strabismus reoperations.

Current concepts of ocular adnexal surgery

Ophthalmic Plastic and Reconstructive Surgery is a specialized area of ophthalmology that deals with the management of deformities and abnormalities of the eyelids, lacrimal system and the orbit. An ophthalmoplastic surgeon is able to identify and correct abnormalities of the ocular adnexae such as ectropion, lid retraction, conjunctival scarring with severe entropion, that can cause secondary ocular surface disorders; manage patients with watering eye, and when needed intervene with a dacryocystorhinostomy by external or endonasal approach and moreover minimize disfigurement following enucleation or evisceration and prevent further corneal damage, alleviate complains of tearing and grittiness, but also cosmetic complaints in patients with Graves' orbitopathy. Aim of this manuscript was to review current established and recently evolving surgical procedures.

In vitro characterization and ex vivo surgical evaluation of human hair keratin films in ocular surface reconstruction after sterilization processing

The disadvantages of human amniotic membrane (hAM), used for ocular surface reconstruction, necessitate the development of standardized alternatives. Keratin-derived-films (KF) have been indicated as transferable substrate for cell cultivation and tissue engineering. The impact of different sterilization procedures on KF and surgical feasibility were investigated. Human hair KF were prepared and sterilized; optical, biomechanical properties, in vitro cell seeding efficiency and proliferation of human corneal epithelial cells were studied and compared with hAM. Surgical feasibility was tested on enucleated porcine eye. Sterilized KF showed higher light transmission and significantly higher E-modulus than hAM; cell-seeding-efficiency and proliferation rate were not affected. Although KF could be surgically handled, suture placement was more difficult compared to hAM. Plasma treatment seems the best sterilization method for KF; it does not affect cell biology or optical and biomechanical properties. However material modifications are requested before KF may represent a feasible alternative for ocular surface reconstruction.

Amniotic membrane in oral and maxillofacial surgery

PURPOSE

Following its renaissance in ophthalmology during the 1990s, preserved human amniotic membrane (HAM) has become an attractive biomaterial for all surgical disciplines. This article reviews the current and potential use of HAM in oral and maxillofacial surgery, its postulated properties and common preservation techniques.

METHODS

Literature was identified by an electronic search of PubMed in July 2012; this was supplemented from the reference lists of the consulted papers.

RESULTS

HAM has been used in the field of oral and maxillofacial surgery from 1969 onwards because of its immunological preference and its pain-reducing, antimicrobial, mechanical and side-dependent adhesive or anti-adhesive properties. The effects of HAM on dermal and mucosal re-epithelialisation have been highlighted. Typically, HAM is applied after being banked in a glycerol-preserved, DMSO-preserved or freeze-dried and irradiated state. Whereas the use of HAM in flap surgery and in intra-oral and extra-oral lining is reported frequently, novel HAM applications in post-traumatic orbital surgery and temporomandibular joint surgery have been added since 2010. Tissue engineering with HAM is a fast-expanding field with a high variety of future options.

CONCLUSIONS

Preserved HAM is considered to be a safe and sufficient biomaterial in all fields of oral and maxillofacial wound healing. Recently published novel indications for HAM application lack a high level of evidence and need to be studied further.

Amniotic membrane in the management of strabismus reoperations

PURPOSE

To reduce postoperative scar formation and to improve duction using amniotic membrane (AM) in strabismus reoperations.

METHODS

A prospective study of interventional case series comprised of 14 patients with restrictive strabismus. Objective clinical findings (visual acuity, angle of deviations and degree of duction deficits) were recorded in both the pre- and post-operative periods. Strabismus surgery included the excision of adhesions and scar tissue, repositioning of extraocular muscles (according to the degree of deviations) and placement of two sheets, one between muscle and tenon and the other between muscle and sclera. Conjunctival recession with covering of the bare sclera using AM was also performed.

RESULTS

The mean preoperative deviation of the patients was 34.3 prism diopters (PD) and mean post-operative deviation was 4.6 PD. The mean pre-operative duction deficit of the patients was 1.7; mean post-operative duction deficit was 0.2. Postoperatively all patients improved in relation to deviation and duction. Less than 8 PD deviations with no duction deficits were achieved in 12 (86 %) of the patients.

CONCLUSIONS

Amniotic membrane placement around the extraocular muscle improves the duction and decreases the residual angle of deviations by inhibiting postoperative scar formation.

Anti-fibrotic effects of fresh and cryopreserved human amniotic membrane in a rat liver fibrosis model

The human amniotic membrane (hAM), thanks to its favorable properties, including anti-inflammatory, anti-fibrotic and pro-regenerative effects, is a well-known surgical material for many clinical applications, when used both freshly after isolation and after preservation. We have shown previously that hAM patching is a potential approach to counteract liver fibrosis. Indeed, when fresh hAM was used to cover the liver surface of rats with liver fibrosis induced by the bile duct ligation (BDL) procedure, the progression and severity of fibrosis were significantly reduced. Since cryopreservation enables safety and long-term storage of hAM but may influence its functional properties, here we compared the anti-fibrotic effects of fresh and cryopreserved hAM in rats with BDL-induced liver fibrosis. After BDL, the rat liver was covered with a piece of fresh or cryopreserved hAM, or left untreated. Six weeks later, the degree of liver fibrosis was assessed histologically using the Knodell and the METAVIR scoring systems. Digital image analysis was used to quantify the percentage of the areas of each liver section displaying ductular reaction, extracellular matrix (ECM) deposition, activated myofibroblasts and hepatic stellate cells (HSCs). Liver collagen content was also determined by spectrophotometric technique. The degree of liver fibrosis, ductular reaction, ECM deposition, and the number of activated myofibroblasts and HSCs were all significantly reduced in hAM-treated rats compared to control animals. Fresh and cryopreserved hAM produced the same anti-fibrotic effects. These findings indicate that cryopreservation maintains the anti-fibrotic properties of hAM when used as a patch to reduce the severity of liver fibrosis.

In vitro reconstruction and characterization of tissue-engineered human corneal epithelium with seeder cells from an untransfected human corneal epithelial cell line

AIM

To demonstrate the morphology and structure of in vitro reconstructed tissue-engineered human corneal epithelium (TE-HCEP) with seeder cells from an untransfected HCEP cell line.

METHODS

The TE-HCEPs were reconstructed in vitro with seeder cells from an untransfected HCEP cell line, and scaffold carriers of denuded amniotic membrane (dAM) in air-liquid interface culture for 3, 5, 7 and 9 days, respectively. The specimens were examined with hematoxylin-eosin (HE) staining of paraffin-section, immunocytochemical staining, scanning and transmission electron microscopy.

RESULTS

During in vitro reconstruction of TE-HCEP, HCEP cells formed a 3-4, 6-7 and 8-10 layers of an HCEP-like structure on dAMs in air-liquid interface culture for 3, 5 and 7 days, respectively. But the cells deceased to 5-6 layers and the structure of straified epithelium became loose at day 9. And the cells maintained positive expression of marker proteins (keratin 3 and keratin 12), cell-junction proteins (zonula occludens-1, E-cadherin, connexin 43 and integrin β1) and membrane transport protein of Na(+)-K(+) ATPase. The HCEP cells in TE-HCEP were rich in microvilli on apical surface and established numerous cell-cell and cell-dAM junctions at day 5.

CONCLUSION

The morphology and structure of the reconstructed TE-HCEP were similar to those of HCEP in vivo. The HCEP cells in the reconstructed TE-HCEP maintained the properties of HCEP cells, including abilities of forming intercellular and cell-extracellular matrix junctions and abilities of performing membrane transportation. The untransfected HCEP cells and dAMs could promisingly be used in reconstruction HCEP equivalent for clinical corneal epithelium transplantation.

Both freshly prepared and frozen-stored amniotic membrane cells express the complement inhibitor CD59

Amniotic membrane proved to be very effective tool in the treatment of a number of ocular surface diseases. The amniotic membrane, however, has to be stored before its transplantation onto the ocular surface followed by mandatory serologic control in order to exclude the transmission of certain viruses. Therefore it is most important to study if cryopreservation of the membrane affects cell surface expression of the molecules. We measured cell surface expression of CD59, a membrane-bound complement inhibitor on the cells of freshly prepared and cryopreserved amniotic membrane. Cells of amniotic membrane were separated mechanically. Epithelial and mesenchymal cells were identified by the intracellular expression of nanog and the cell surface ICAM1 positivity, respectively. Multicolor flow cytometric immunophenotyping was used for determination of the CD59 expression. CellQuest-Pro software program (Becton Dickinson) was used both for measurements and analysis. CD59-positive cells could be detected in all investigated samples and in all investigated cell types, although the expression level of CD59 differed. CD59 was expressed both on freshly prepared and frozen-stored samples. Higher level of CD59 was detected on ICAM1+ mesenchymal cells than on nanog+ epithelial cells. Our findings indicate that amniotic membranes maintain their complement inhibiting capacity after cryopreservation.

Effect of lyophilized amniotic membrane on the development of adhesions and fibrosis after extraocular muscle surgery in rabbits

PURPOSE

To histopathologically evaluate the influence of lyophilized human amniotic membrane transplant on the development of postoperative adhesions and fibrosis after extraocular muscle surgery.

METHODS

Ten albino rabbits were used. The superior rectus muscle was resected 4 mm in both eyes. In right eyes, the superior rectus muscle was wrapped with lyophilized (air-dried, freeze-dried) human amniotic membrane (group AM). In left eyes, the superior rectus muscle was not wrapped with amniotic membrane, and served as a control group (group C). The rabbits were sacrificed and the eyes were enucleated 6 weeks after surgery to perform histopathological examination.

RESULTS

Two rabbits died 1 week after surgery and were excluded. Histopathological evaluation of both eyes of the remaining 8 rabbits was done. The amniotic membrane was not seen in all eyes. On comparing eye pairs of each rabbit, right eyes showed significantly less conjunctival inflammation (p = 0.034), but insignificantly less foreign body inflammation (p = 0.625), adhesions between sclera and muscle (p = 0.206), muscle fibrosis (p = 1.000), and conjunctival hyperemia (p = 0.059) as compared to left eyes.

CONCLUSIONS

Lyophilized amniotic membrane insignificantly reduces postoperative adhesions and fibrosis, when used to wrap the operated upon extraocular muscles, limiting the benefit of this membrane in strabismus surgery.

The effects of preservation procedures on amniotic membrane's ability to serve as a substrate for cultivation of endothelial cells

Amniotic membrane (AM) has been used as a scaffold for the ex vivo expansion of different types of cells and a cell delivery matrix in regenerative medicine. Since the preservation procedures can influence the AM properties for experimental and clinical purposes, this study was established to investigate the feasibility of using the AM after different preservation methods to serve as substrates for endothelial cell expansion ex vivo. The effects of cryopreservation and lyophilization were evaluated on mechanical and histological characteristics of the AM, and the results were compared with the fresh AM. The ECM components of the basement membrane were well conserved in all groups. Although lyophilization resulted in more histological changes and lower level of physical variables including thickness, F(max), elongation at break and suture retention than the fresh and cryopreserved AM, endothelial cells grown on the lyophilized AM were better attached to the basement membrane. Cytotoxicity assay by MTT showed that the lyophilized AM is a compatible substrate for endothelial cells cultivation. The findings of this study suggest that the lyophilized AM is a suitable matrix for cultivation of endothelial cells due to this fact that lyophilization led to exposure of basement membrane of the AM.

Amniotic membrane as a scaffold for melanocyte transplantation in patients with stable vitiligo

Vitiligo is an acquired skin disease that significantly impacts the quality of life of patients. Medical treatment of vitiligo includes the use of melanocyte transplant, but the results are variable. We have treated 4 patients with either focal or generalized stable vitiligo using a graft of autologous melanocytes' culture on a denuded amniotic membrane (AM). A culture biopsy was obtained in every patient and grown in melanocytes' media for 10-14 days after which cells were transferred to a denuded AM and transplanted into the achromic lesions. Patients were followed for up to 6 months using clinical assessment of achromic lesions. Treated areas ranged between 4 cm(2) and 210.6 cm(2). Response to treatment was excellent in all patients with 90-95% repigmentation success rate. Our results demonstrate that transplantation of autologous melanocytes cultured on AM is a new, simple, and effective treatment for stable vitiligo.

Simultaneous amniotic membrane patch in high-risk keratoplasty

PURPOSE

To analyze the short- and intermediate-term results of simultaneous transplantation of amniotic membrane with high-risk keratoplasty.

METHODS

Between January 2002 and February 2004, a simultaneous amniotic membrane patch was transplanted with penetrating keratoplasty in 16 eyes of 16 patients. In 13 eyes, a soft contact lens was applied afterward. Corneal perforation was present in 10 of 14 eyes with emergency keratoplasty. Five patients received systemic immunosuppressive medication for 4-6 months after penetrating keratoplasty.

RESULTS

The amniotic membrane patch fell off after 8 ± 3 (range: 4-14) days without residual tissue except in 1 case. In 15 of 16 eyes, the epithelium was completely closed after 10 ± 8 (range: 4-30) days. In 3 eyes, recurrence of the epithelial defect occurred after 3-6 months. During a follow-up period of 18 ± 6 months, 13 of 16 corneal grafts were clear.

CONCLUSIONS

Simultaneous amniotic membrane transplantation and penetrating keratoplasty may improve the prognosis of corneal graft in eyes with risk of epithelial healing problems.

Inhibition of angiogenesis by HC·HA, a complex of hyaluronan and the heavy chain of inter-α-inhibitor, purified from human amniotic membrane

PURPOSE

To determine whether antiangiogenic action of the amniotic membrane (AM) can be mediated by HC·HA, a covalent complex of hyaluronan (HA) and the heavy chain (HC) of inter-α-inhibitor, purified from AM soluble extract.

METHODS

HC·HA action on viability, proliferation, attachment, death, migration, and differentiation of human umbilical vein endothelial cells (HUVECs) and neovascularization in chicken chorioallantoic membrane (CAM) was examined by MTT assay, BrdU labeling, cell proliferation assay, cell death detection ELISA, transwell assay, tube formation assay, and CAM assay.

RESULTS

HC·HA suppressed HUVEC viability more significantly than HA and AM stromal extract, and such suppression was not mediated by CD44. HC·HA also caused HUVECs to become small and rounded, with a decrease in spreading and filamentous actin. Without promoting cell detachment or death, HC·HA dose dependently inhibited proliferation (IC(50), 2.3 μg/mL) and was 100-fold more potent than HA. Migration triggered by VEGF and tube formation was also significantly inhibited by HC·HA. Purified HC·HA did not contain PEDF and TSP-1 but did contain IGFBP-1 and platelet factor 4 while significantly suppressing neovascularization in CAM.

CONCLUSIONS

The antiangiogenic activity of HC·HA might explain why AM is developmentally avascular and how AM might exert an antiangiogenic action when transplanted to the ocular surface, and it might indicate a potential therapeutic effect of HC·HA in diseases manifesting pathogenic angiogenesis. Roles of IGFBP-1 and platelet factor 4 in HC·HA antiangiogenic action warrant further investigation.

Isolation and properties of an in vitro human outer blood-retinal barrier model

The outer blood-retinal barrier is composed of a monolayer of retinal pigment epithelium (RPE), Bruch's membrane, and the choriocapillaris, which is fenestrated. An in vitro model that includes all these layers within a 3-D architecture confers a clear advantage over traditional monolayer cultures. Cells here, whether endothelial or epithelial, reside in conditions resembling that in vivo and can participate in cell-cell and cell-matrix cross talk. This chapter describes how a human trilayer culture model was generated with RPE (ARPE-19) cells cultured on the epithelial surface of amniotic membrane and with human umbilical vein derived endothelial cells (HUVEC) on the interstitial surface. This model resembles the outer retinal barrier both in restricting transport of small molecules (<4 kDa), possession of occludin-rich tight junctions in the RPE and fenestrated endothelial cells. Techniques used to test the generated trilayer properties are also described and these include imaging of structure and molecular occupancy of tight and adherens junctions, estimation of the barrier efficiency of trilayer by measurement of fluorescein and fluorescein-conjugated tracers under flow, measurement of secreted vascular endothelial growth factor-A and ultrastructural studies, which allow analyses of the fine structure of the tight junctions in the RPE, and the endothelial fenestra.

Differentiation status of limbal epithelial cells cultured on intact and denuded amniotic membrane before and after air-lifting

We have investigated differences in bovine limbal epithelial cell differentiation when expanded upon intact (amniotic epithelial cells and basement membrane remaining) and denuded human amniotic membrane (AM), a commonly used substrate in ophthalmic surgery for corneal stem cell transplantation. Ex vivo expansion of the epithelial cells, in supplemented media, continued for 2 weeks followed by 1 week under air-lifting conditions. Before and after air-lifting the differentiated (K3/K12 positive) and undifferentiated (K14 positive) cells were quantified by immunohistochemistry, Western blotting, and quantitative polymerase chain reaction. Limbal epithelial cells expanded upon AM formed 4-6 stratified layers, both on intact AM (iAM) and denuded AM (dAM). On dAM the proportion of differentiated cells remained unaltered after air-lifting. Within cells grown on iAM, however, the number of differentiated cells increased significantly after air-lifting. These results have important implications for both basic and clinical research. First, they show that bovine limbal epithelia can be used as an alternative source of cells for basic research investigating ex vivo limbal stem cells expansion. Second, these findings serve as a warning to clinicians that the effect of AM on transplantable cells is not fully understood; the use of iAM or dAM can produce different results in terms of the amount of differentiation, once cells are exposed to the air.

Donor age and gestational age influence on growth factor levels in human amniotic membrane

PURPOSE

Amniotic membrane (AM) is used as a biomaterial for reconstruction in ocular surface surgery. This study investigated the influence of interdonor variations and processing and preservation procedures applied to the AM on growth factors and protein levels.

METHODS

 Samples of human AM from thirteen donors were analysed. Collected donor data were age, parity and gestational age. Total protein amount was measured in extracts of intact AM nonpreserved, lyophilized and cryopreserved, at -80°C and in liquid nitrogen. An enzyme-linked immunosorbent assay (ELISA) was used to assay growth factors protein levels for epidermal growth factor, basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), keratinocyte growth factor (KGF), transforming growth factor beta1 (TFG-β(1) ) and nerve growth factor (NGF). Univariate and multivariate statistical analyses were used to study the influence of the preservation method applied and interdonor variations on growth factors levels.

RESULTS

We detected important variations in growth factors and protein concentrations between samples from different donors. Total protein amount, bFGF, HGF, KGF and TGF-β(1) showed lower levels in samples from donors with higher gestational ages and donor ages, for all groups.

CONCLUSION

The variability in the biochemical composition of AM from different donors is considerable, and it is related with donor factors as donor age and gestational age. As AM biochemical composition has a role in its therapeutic effects, these variations could affect the clinical results of amniotic membrane transplantation and must be taken into account in donor selection processes.

Comparison of cryopreserved and air-dried human amniotic membrane for ophthalmologic applications

BACKGROUND

Cryopreserved amniotic membrane (Cryo-AM) is widely used in ocular surface surgery because of its positive effect on wound healing and its anti-inflammatory properties. A new peracetic acid/ethanol sterilized air-dried amniotic membrane (AD-AM) recently became available which might be an alternative to Cryo-AM. Our aim was to compare AM preserved with both methods with regard to the release of wound-healing modulating proteins, the preservation of basement membrane components, and the ability to serve as a substrate for the cultivation of human limbal epithelial cells (HLECs).

METHODS

Pieces of Cryo-AM and AD-AM from three different donors were incubated in DMEM for five days. The culture supernatant was collected after an incubation period of 0.1, 24, 48, 72 and 120 h; in the case of AD-AM, this period was extended up to 14 days. TIMP-1, IL-1ra, CTGF and TGF-beta1 were detected in the culture supernatant using Western blotting. Twenty human limbal epithelial cultures were initiated on both AD- and Cryo-AM. The cultures were analyzed morphologically, and the outgrowth area was measured in 3-day intervals. Cryosections of Cryo- and AD-AM from three different donors were analyzed histochemically to detect the basement membrane components collagen IV, collagen VII, laminin, laminin 5 and fibronectin.

RESULTS

The release of TIMP-1, IL-1ra and TGF-beta1 from Cryo-AM was constant for the studied period. CTGF showed a stronger signal after 120 h. None of the analyzed proteins, except for a small amount of IL-1ra, could be detected in the supernatant of AD-AM. An outgrowth of HLEC was observed in all cultures on Cryo-AM, but in only 30% of cultures on AD-AM. The outgrowth area on Cryo-AM was at all time points significantly higher than on AD-AM (p < 0.0001). Collagen IV, -VII, laminins and fibronectin were detectable in the basement membrane of Cryo-AM, but only collagen IV and fibronectin in AD-AM.

CONCLUSIONS

Cryo-AM is a more suitable substrate for the cultivation of HLECs than AD-AM. The higher outgrowth rate of cultured limbal epithelium, release of intact soluble wound-healing modulating factors and a better preservation of basement membrane components suggest the superiority of Cryo-AM for use in ophthalmology in comparison to AD-AM.

Culture conditions for primary human limbal epithelial cells

The cornea at the front of the eye is covered by an epithelium. This epithelium is maintained by stem cells located at the periphery of the cornea, in a region known as the limbus. Because this region harbors the stem cells for the corneal epithelium, the so-called limbal stem cells, its culture provides considerable interest. Limbal epithelial culture is used for two main reasons. The first is to further our understanding of limbal stem-cell biology. The second is for the culture expansion of limbal stem cells for transplantation purposes in patients with limbal stem-cell deficiency. However, considerable variations in the culture methods for limbal epithelium exist. These include culture media, sera used in the culture, use of 3T3 fibroblasts or amniotic membrane or both, the culture of whole pieces of limbal tissue or enzymatically digested tissue, and the use of airlifting.

Adnexal Surgery for Severe Ocular Surface Disease

Secondary causes of ocular surface disease are-to a large extent-due to disorders of the ocular adnexae. The main pathomechanisms involved include exposure, abrasion and malnutrition, resulting from a multitude of disorders such as ec- or entropion (e.g. in cicatrizing conjunctivitis), lid retraction and severe aqueous deficiency. In the presence of these problems, surgical attempts of ocular surface reconstruction frequently fail. Here we review established and evolving new techniques in the field of adnexal surgery to specifically address these problems.

Decellularization of bovine corneas for tissue engineering applications

Scaffolds derived from processed tissues offer viable alternatives to synthetic polymers as biological scaffolds for regenerative medicine. Tissue-derived scaffolds provide an extracellular matrix (ECM) as the starting material for wound healing and the functional reconstruction of tissues, offering a potentially valuable approach for the replacement of damaged or missing tissues. Additionally, acellular tissue may provide a natural microenvironment for host-cell migration and the induction of stem cell differentiation to contribute to tissue regeneration. There are a number of processing methods that aim to stabilize and provide an immunologically inert tissue scaffold. Furthermore, these tissue-processing methods can often be applied to xenogenic transplants because the essential components of the ECM are often maintained between species. In this study, we applied several tissue-processing protocols to the cornea in order to obtain a decellularized cornea matrix that maintained the clarity and mechanical properties of the native tissue. Histology, mechanical testing and electron microscopy techniques were used to assess the cell extraction process and the organization of the remaining ECM. In vitro cell seeding experiments confirmed the processed corneas' biocompatibility.

Effects of lyophilization on human amniotic membrane

PURPOSE

This study aimed to evaluate the effects of lyophilization and cryopreservation on human amniotic membrane (HAM) in terms of histological characteristics and growth factor levels.

METHODS

Non-preserved, lyophilized and cryopreserved HAM samples from 13 placentas were investigated. The morphological characteristics of HAM were evaluated using light and electron microscopy. Immunohistochemical methods were also applied to assess the distribution of collagen IV in the basement membrane. Total protein amounts were measured in extracts of intact amniotic membrane from non-preserved, lyophilized and cryopreserved samples. An enzyme-linked immunosorbent assay (ELISA) was used to assay growth factor protein levels for epidermal growth factor, fibroblast growth factor basic, hepatocyte growth factor, keratinocyte growth factor, transforming growth factor-beta1 and nerve growth factor.

RESULTS

Histological examination of lyophilized and cryopreserved human amniotic membrane showed similar results. Immunohistochemistry showed presence of collagen IV throughout the basement membrane, both in cryopreserved and lyophilized samples. Total protein amount was higher in cryopreserved samples, without statistical significance. Growth factors ELISA did not show statistically significant differences except for fibroblast growth factor basic, with higher levels in cryopreserved amniotic membrane.

CONCLUSIONS

Lyophilization maintains the histological structure of HAM, but seems to cause greater reductions in total protein amount and growth factor concentration than cryopreservation.

Amniotic membrane and amniotic fluid-derived cells: potential tools for regenerative medicine?

Human amniotic membranes and amniotic fluid have attracted increasing attention in recent years as a possible reserve of stem cells that may be useful for clinical application in regenerative medicine. Many studies have been conducted to date in terms of the differentiation potential of these cells, with several reports demonstrating that cells from both the amniotic fluid and membrane display high plasticity. In addition, cells from the amniotic membrane have also been shown to display immunomodulatory characteristics both in vivo and in vitro, which could make them useful in an allotransplantation setting. Here, we provide an overview comparing the latest findings regarding the stem characteristics of cells from both the amniotic membrane and amniotic fluid, as well as on the potential utility of these cells for future clinical application in regenerative medicine.

The influence of various storage conditions on cell viability in amniotic membrane

Up to now freeze-dried, gamma-sterilised or glycerol-preserved amniotic membranes (AMs) have widely been used in the field of ophthalmology and wound care (e.g. leg ulcers, burns). After some preservation processes in use, like freeze-drying or glycerol-preserving, the cells in the AM are no longer viable. Within this study we evaluated the influence of different short-term and long-term storage conditions on cell viability in AM. Therefore AMs from cesarean section placentae were washed and biopsied to evaluate the microbiological status and to determine the viability of the tissue. Additionally, viability under various storage conditions was examined by assessment of mitochondrial activity. Preservation included temperatures above and below 0 degrees C as well as various media compositions. As expected, cell viability in amnion decreases during storage, in fact the effect was more pronounced when stored frozen, but the higher viability of amnion obtained by storage above 0 degrees C with medium is associated with the limitation to a short period of storage of about 28 days. The evaluated preservation methods are the basis for future non-clinical in-vivo studies in which the possible benefit of amnion as a viable biomaterial in wound healing will be investigated.

The effect of amniotic membrane preparation method on its ability to serve as a substrate for the ex-vivo expansion of limbal epithelial cells

Human amniotic membrane (HAM) is employed as a substrate for the ex-vivo expansion of limbal epithelial cells (LECs) used to treat corneal epithelial stem cell deficiency in humans. The optimal method of HAM preparation for this purpose is unknown. This study evaluated the ability of different preparations of stored HAM to serve as substrates for LEC expansion ex-vivo. The effect of removing the amniotic epithelial cells (decellularisation) from HAM prior to seeding of LECs, the effect of glycerol cryopreservation and the effect of peracetic acid (PAA) sterilization and antibiotic disinfection were evaluated using different HAM test groups. Human LECs were cultured on each preparation and the following outcomes were assessed: confluence of growth, cell density, cell morphology and expression of the putative LESC markers deltaN-p63alpha and ABCG2. Removing amniotic epithelial cells prior to seeding of LECs resulted in a higher percentage of confluence but a lower cell density than intact HAM suggesting that decellularisation does not increase proliferation, but rather that it facilitates migration of LECs resulting in larger cells. Decellularisation did not affect the percentage of cells expressing the putative LESC markers deltaN-p63alpha (< or =4% in both intact and acellular groups) and ABCG2 (< or =3% in both intact and acellular groups). Glycerol cryopreservation of HAM resulted in poor morphology and a low proportion of cells expressing deltaN-p63alpha (< or =6%) and ABCG2 (< or =8%). HAM frozen at -80 degrees C in Hank's Balanced Salt Solution (HBSS) was superior, demonstrating excellent morphology of cultured LECs and high levels of deltaN-p63alpha (< or =68%) and ABCG2 (< or =62%) expression (p<0.001). The use of PAA or antibiotics to decontaminate HAM does not appear to affect this function. The variables affecting the ability of HAM to serve as a substrate for LEC expansion ex-vivo are poorly understood. The use of glycerol as a cryoprotectant impairs this ability whereas simple frozen HAM appears to work extremely well for this purpose.

Cryopreserved human amniotic membrane for soft tissue repair in rats

Fresh amniotic membrane has been used in medicine since 1910. The reconstruction of immunologic privileged ocular surfaces with cryopreserved amniotic membrane was introduced in the 1990s. The aim of this study was to analyze the use of cryopreserved human amniotic membrane (HAM) as a surgical patch in immunologic unprivileged anatomic sites. In part I of the investigation, the abdominal wall muscle of 36 rats was covered with mono- and multilayered HAM. After 3, 14, and 28 days, respectively, these grafts were evaluated macro- and microscopically. Multilayer samples displayed slower degradation and less inflammation compared with monolayer coverage. In part II of the study, abdominal wall closure with multilayer HAM and with polypropylene mesh was conducted in 20 rats. All rats showed sufficient closure after 21 days, but significantly lower intraabdominal adhesion formation was observed in the HAM rats. The results of this study might pave the way for the use of cryopreserved HAM as graft material in reconstructive surgery.

Sterilization and preservation influence the biophysical properties of human amnion grafts

The introduction of amniotic membrane (AM) transplantation in ophthalmic surgery holds great promise and in many clinical situations it offers an alternative to existing management options. The purpose of this study was to examine the influence of established sterilization and preservation procedures on biophysical and histological properties of AM grafts. Amnion was sterilized by peracetic acid/ethanol sterilization [PES] and preserved by air-drying (sterile laminar flow) [AD] or in glycerol [GLYC]. Unsterilized AM were preserved at -80 degrees C [-80 degrees C] and served as an experimental control. Amnion allografts were characterized by the determination of their thickness, moisture vapour permeability (MVP), oxygen permeability (OPERM), tensile strength and sulphur content. Immunostaining for tissue-specific and basement membrane-related proteins was performed. Differences in biophysical parameters were found between the unsterilized allografts and the sterilized, air-dried or glycerol-preserved allografts. [PES/AD] showed the highest MVP and OPERM, the highest tensile strength and the lowest sulphur content and thickness. [PES/GLYC] exhibited the lowest OPERM and the highest thickness compared to [-80 degrees C] and [PES/AD]. Collagen types V and VII were preserved the best in the control group. Sterilization and preservation affect biophysical properties important for the use of AM as allogenic grafts. It has to be determined if any change, as noted, has a clinical impact.

Hypopyon iritis after primary fresh amniotic membrane transplantation

PURPOSE

To report the occurrence of hypopyon iritis after primary, fresh amniotic membrane transplant (AMT).

METHODS

A case report of a 65-year-old man who underwent AMT along with placement of hydrophilic contact lens for symptomatic relief of pseudophakic bullous keratopathy for the first time. The amniotic membrane (AM) transplanted was obtained freshly after an elective cesarean section.

RESULTS

The patient developed hypopyon on the second postoperative day. Culture of remnants of AM and contact lens were negative. Hypopyon did not respond to periocular antibiotics but disappeared with periocular steroids. Hypopyon was noticed again at 1-week follow-up because of poor compliance of the patient. It again responded to periocular steroids. At 1-year follow-up, the patient is asymptomatic with 20/600 vision.

CONCLUSIONS

Sterile hypopyon iritis appeared after primary AMT with fresh AM, and it disappeared with periocular steroids.

[Amniotic membrane transplantation. An indispensable therapy option for persistent corneal epithelial defects]

Nowadays, cryopreserved amniotic membrane transplantation (AMT) is omnipresent in the therapy of persistent corneal epithelial defects. With persistent corneal ulcers AMT should be considered early, to avoid keratoplasty à chaud or even a conjunctival flap. A differentiated microsurgical technique results in different integration patterns of AM into the human cornea. The sandwich technique seems to have advantages in contrast to the solitary graft or patch techniques with respect to primary success and recurrence rate. Corneal infections are extremely rare after AMT, but may happen. Postoperatively, phosphate-containing eye drops should not be used to avoid corneal calcification. AMT appears to have a great variety of merits before, instead of, during, or even after keratoplasty. The consequent systemic therapy of underlying diseases is absolutely indispensable for durable success of AMT.

Transplante de membrana amniótica canina criopreservada para cicatrização de córnea com deficiência de células límbicas em coelhos

Avaliaram-se as alterações relacionadas à deficiência das células límbicas precursoras do epitélio corneano de coelhos e o efeito da membrana amniótica sobre sua cicatrização. A lesão, induzida com n-heptanol associado à peritomia conjuntival em 360°, foi recoberta com membrana amniótica canina, suturada à episclera perilímbica, criopreservada em meio para congelação de embrião ou em meio próprio, ambos com glicerol a 50% e mantida a -80°C. O grupo-controle não foi tratado com a membrana. As avaliações histológicas foram realizadas ao sétimo, 15º e 30º dias. Todos desenvolveram deficiência de células germinativas do limbo, denominada conjuntivalização, com presença de neovascularização, inflamação e defeitos epiteliais recorrentes, caracterizada na histopatologia pela presença de neovasos, edema, leucócitos e células caliciformes. O transplante de membrana amniótica não foi eficiente para o tratamento desta deficiência, entretanto auxiliou o processo de cicatrização da córnea.

How does amniotic membrane work?

Transplantation of amniotic membrane as a temporary or permanent graft promotes epithelial wound healing and exerts potent anti-inflammatory and anti-scarring effects on the ocular surface. These actions depend on the killing of allogeneic amniotic cells and preservation of the cytokine-containing matrix during the preparation of the amniotic membrane. This review describes how these actions inherently operate in utero and how amniotic membrane transplantation aims to recreate such a fetal environment to exert these actions by insulating the surgical site from the host environment. These actions also render the amniotic membrane a unique niche capable of expanding both epithelial and mesenchymal progenitor cells ex vivo, while maintaining their normal cell phenotypes. As a result, the amniotic membrane becomes an ideal substrate for engineering different types of ocular surface tissues for transplantation. Further studies investigating the exact molecular mechanism by which the amniotic membrane works will undoubtedly unravel additional applications in reconstruction and engineering of both ocular and nonocular tissues in the burgeoning field of regenerative medicine.

Use of Autologous Platelet-Rich Plasma in the Treatment of Dormant Corneal Ulcers

PURPOSE

To investigate the potential role of autologous platelet-rich plasma in promoting healing in dormant corneal ulcers.

DESIGN

Prospective, consecutive, interventional, noncomparative, nonrandomized, observational study.

PARTICIPANTS

Forty eyes of 38 patients with dormant corneal ulcers.

METHODS

Autologous platelet-rich plasma was used in a total of 40 eyes with dormant corneal ulcers divided into 2 groups: group I, 26 eyes treated with topical eyedrops of autologous platelet-rich plasma (12 neurotrophic, 9 herpetic, and 5 immunological ulcers), and group II, 14 eyes treated surgically with a solid clot of autologous platelet-rich plasma combined with amniotic membrane transplantation in perforated corneas or with impending perforation. The treatment was used in patients with chronic nonhealing ulcers (mean, 2 years of evolution) that had been unresponsive to conventional topical therapy. Autologous blood from each patient was obtained by venipuncture, and platelet-rich plasma was prepared from each blood sample without additives.

MAIN OUTCOME MEASURES

Ulcer size, inflammation, healing, visual acuity, and patient's subjective symptoms.

RESULTS

Autologous platelet-rich plasma promoted healing of ulcers. In group I, 13 eyes healed, 11 eyes improved significantly, and 2 eyes showed no change. In group II, 10 eyes healed and 4 eyes improved significantly. Inflammation and subjective symptoms, particularly pain, improved in all patients. Vision remained stable or improved in all cases.

CONCLUSION

Autologous platelet-rich plasma promoted healing of dormant corneal ulcers even in eyes threatened by corneal perforation and was accompanied by a reduction in pain and inflammation.