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

An in vitro comparison of human corneal epithelial cell activity and inflammatory response on differently designed ocular amniotic membranes and a clinical case study

Amniotic membrane (AM) is a naturally derived biomaterial with biological and mechanical properties important to Ophthalmology. The epithelial side of the AM promotes epithelialization, while the stromal side regulates inflammation. However, not all AMs are equal. AMs undergo different processing with resultant changes in cellular content and structure. This study evaluates the effects of sidedness and processing on human corneal epithelial cell (HCEC) activity, the effect of processing on HCEC inflammatory response, and then a case study is presented. Three differently processed, commercially available ocular AMs were selected: (1) Biovance®3L Ocular, a decellularized, dehydrated human AM (DDHAM), (2) AMBIO2®, a dehydrated human AM (DHAM), and (3) AmnioGraft®, a cryopreserved human AM (CHAM). HCECs were seeded onto the AMs and incubated for 1, 4 and 7 days. Cell adhesion and viability were evaluated using alamarBlue assay. HCEC migration was evaluated using a scratch wound assay. An inflammatory response was induced by TNF-α treatment. The effect of AM on the expression of pro-inflammatory genes in HCECs was compared using quantitative polymerase chain reaction (qPCR). Staining confirmed complete decellularization and the absence of nuclei in DDHAM. HCEC activity was best supported on the stromal side of DDHAM. Under inflammatory stimulation, DDHAM promoted a higher initial inflammatory response with a declining trend across time. Clinically, DDHAM was used to successfully treat anterior basement membrane dystrophy. Compared with DHAM and CHAM, DDHAM had significant positive effects on the cellular activities of HCECs in vitro, which may suggest greater ocular cell compatibility in vivo.

Double covering with amniotic membrane in restrictive strabismus

A case of severe restrictive strabismus after a consecutive exotropia surgery is presented. We describe the exitous managment through a technique consist of wrapping with amniotic membrane (AM) the affected muscle where we add a second AM graft in the reconstruction of the ocular Surface.

Histologic and Immunohistochemical Evaluation of Radiosurgery in Strabismus Surgery in a Rabbit Model

PURPOSE

The aim of this study was to evaluate the use of monopolar radiosurgery (MRS) assisted strabismus surgery and to compare its histologic and immunohistochemical wound healing outcomes with conventional surgery.

MATERIALS AND METHODS

Superior rectus muscle resection was performed on 30 white rabbits with three different surgical muscle cutting techniques: monopolar radiosurgery (MRS group), conventional scissors preceded by bipolar electrocautery (BEC group), and conventional scissors with no cauterization (control group). Degree of tissue injury, bleeding, inflammation, and fibrosis, as well as wound healing rate (CD68+ cell number), were evaluated.

RESULTS

In CS group, hemorrhage scores were significantly higher than those in the other groups (MRS group: Z = 5.182; p < 0.001 and BEC group: Z = 4.463; p < 0.001) and MRS group had lower scores than BEC group; however, the difference was not significant (Z = 1.423; p = 0.211). The tissue injury score in BEC group was higher when compared with MRS, and the difference was statistically significant (p = 0.028). Median inflammation scores at days 1 and 21 were lowest in MRS group, but the difference was not statistically significant among groups (day 1; p = 0.115, day 21; p = 0.095). The median fibrosis score was higher in the control group, when compared with MRS, and the difference was statistically significant (muscle-sclera; p = 0.011 and muscle-conjunctiva: p = 0.003). The macrophage score (number of CD68+ cells) was lowest in CS group; however, the difference was not significant (p = 0.657).

CONCLUSIONS

Monopolar radiosurgery is a novel method for strabismus surgery and provides equivalent hemostasis effects and wound healing properties, compared with conventional methods, and enhances surgeon comfort, as muscle incisions are made in one step with clean surgical area.

The effect of platelet-rich fibrin on wound healing following strabismus surgery

PURPOSE

To investigate the effect of platelet-rich fibrin (PRF) on post-operative wound healing following strabismus surgery in a rabbit model.

METHODS

Nine New Zealand white rabbits were involved in the study. One of these nine rabbits was kept in control without having any operation. Both eyes of eight rabbits underwent superior rectus muscle (SRM) resection. After resection of SRM, PRF was applied to SRM of the right eyes. In the left eye, SRM was not wrapped with PRF and served as a control. The rabbits were sacrificed and enucleated 6 weeks after the surgery. Inflammation and vascular proliferation were assessed by staining with haematoxylin-eosin. Scar and fibrosis were examined by the Masson trichrome staining. Immunohistochemical staining was performed for a vascular endothelial growth factor (VEGF) and alpha-smooth muscle actin (α-SMA).

RESULTS

There was no significant difference in terms of inflammation (p = 0.535), vascularization (p = 0.602), and fibrosis (p = 0.745) between the eyes. Immunohistochemical staining for VEGF demonstrated no significant difference (p = 0.745). However, significant staining for α-SMA was detected in PRF-treated eyes compared with control eyes (p = 0.037).

CONCLUSION

Consistent with the hypothesis that PRF facilitates wound healing as a biocatalyst, there was only a significant difference for α-SMA related to myofibroblast activity which is important for wound remodelling. Future comprehensive studies are needed to extend these results.

Histopathological changes in extraocular muscles of rabbits following injection of Bupivacaine 5mg/ml versus 7.5mg/ml

PURPOSE

To compare the histopathological effects of injecting 2 concentrations of Bupivacaine (5mg/ml and 7.5mg/ml) in the superior rectus muscle of rabbits, and to compare these to conventional extraocular muscle surgery in previous studies.

METHODS

Eighteen albino rabbits' eyes were used. The superior rectus muscles were injected with Bupivacaine 5mg/ml (Group B5, 10 eyes) or 7.5mg/ml (Group B7, 8 eyes). The rabbits were sacrificed and eyes enucleated 6 weeks later for histopathological evaluation. Results were compared to the average of those obtained, by 3 previous studies, after conventional superior rectus resection in rabbits.

RESULTS

Foreign body reaction was absent in all specimens. Conjunctival and scleral inflammation, perimuscular adhesions, intramuscular fibrosis, conjunctival and scleral oedema and muscle atrophy were higher in group B7, while conjunctival hyperaemia and muscle hypertrophy were higher in group B5 (p > .05). On comparison to conventional surgery, conjunctival inflammation and hyperaemia, foreign body reaction, and adhesions were less after bupivacaine injection (p >.05 for all except for intensity of conjunctival inflammation in B5 versus conventional surgery). Scleral inflammation was more frequent after bupivacaine injection (p <.05). Muscle fibrosis was more frequent in group B7 and conventional surgery than in group B5 (p >.05).

CONCLUSIONS

Both Bupivacaine concentrations effectively produced the desired muscle hypertrophy and fibrosis, so the lower concentration may be used for muscle strengthening to correct strabismus. Bupivacaine injection, although produced no foreign body reaction, did not significantly lower the development of undesired postoperative adhesions and caused more scleral inflammation.

Treatment and prevention of ocular motility restrictions with amniotic membrane transplantation

We intend to investigate the indications, complications, and final results of amniotic membrane (AM) transplantation in ocular motility restrictions. Surgeons have tried to prevent restrictive adhesions between the extraocular muscles and surrounding tissues because they cause unpredictable results. AM transplantation wrapping extraocular musculature has been proposed as a technique with good results for this purpose. A search was carried out in Medline, Embase, Cochrane Library and Clinicaltrial, Lilac and Ibecs databases, using the indexed terms" amnion", "strabismus," "strabismus-subheading-surgery" and "ocular motility disorders." The only exclusion criteria were studies conducted in non-humans or studies with insufficient data on eye motility. No study was discarded for analysis because of language, age or methodology. This review includes 165 patients (223 eyes), with a mean follow-up of 11.49 months. The mean age was 21 years old, 47% were males and 57% were children. 14 studies conducted in humans were eligible: 4 single case, 8 case series, 1 cohort study and 1 randomized clinical trial. In the vast majority of these papers, use of AM transplantation to treat (12 out of 14 papers) or either to prevent (2 out of 14 papers) motility restrictions or restrictive strabismus secondary to muscular adhesions. All the studies except one presents very favorable results improving postsurgical eye motility. The cryopreservation method was more widely used, presenting a good safety profile with few adverse effects in the short and medium term. Significant improvement was reported in most patients after the use of amniotic membrane transplantation to treat or prevent ocular motility limitations. Very few complications or adverse effects were documented.

Palmitoylethanolamide (PEA) reduces postoperative adhesions after experimental strabismus surgery in rabbits by suppressing canonical and non-canonical TGFβ signaling through PPARα

Postoperative adhesions and scarring are the particular complication after strabismus surgery, for which there is currently no comprehensive treatment available. Preventing inflammation and fibrosis in the extraocular muscle are crucial for treatment of postoperative adhesions. In the present study, we found that administration of palmitoylethanolamide (PEA) attenuated postoperative inflammation and fibroproliferation through activating peroxisome proliferator-activated receptor α (PPARα), thus prevented scar formation. Inhibition of PEA degradation by N-Acylethanolamine acid amidase (NAAA) inhibitor F96 led to the same pharmacological results. PPARα activation suppressed both canonical and non-canonical TGFβ signaling. Mechanistically, we found that PPARα directly bound to TGFβ-activated kinase 1 (TAK1), thus preventing its hyperphosphorylation and the activation of downstream p38 and JNK1/2 signaling. Taken together, current study suggested that PEA could be a novel therapeutic approach for postoperative adhesions after strabismus surgery.

Surgical and Immunohistochemical Outcomes of Scleral Reconstruction with Autogenic, Allogenic and Xenogenic Grafts: An Experimental Rabbit Model

Purpose: Choukroun's platelet-rich fibrin (PRF), a second-generation platelet concentrate, has unique morphological and chemical features and may be considered as a scaffold for scleral reinforcement and regeneration. The purpose of this study was to compare the use of xenogenic human-derived amniotic membrane (HAM), allogenic sclera, and autogenic PRF in rabbit lamellar scleral defect model with respect to both anatomical and immunohistochemical improvement. Methods: A total of 45 adult New Zealand rabbits were randomized into five groups: normal control; without surgical procedure, negative control; scleral defect model (SDM), xenogenic HAM; SDM+HAM graft, allogenic sclera; SDM+allogenic sclera graft, autogenic PRF; SDM+autogenic PRF graft. Clinical findings, Hematoxylin&Eozin (HE), Masson Trichrome, Verhoeff Acid Fuchsin, Transforming Growth Factor β Receptor 1, Fibroblast Growth Factor, Bone Morphogenetic Protein 2, collagen type 1, aggrecan, and Matrix Metalloproteinase 2 were evaluated. Results: Ocular surface inflammation was significantly lower in normal control and autogenic PRF groups (p < .001). Graft was avascular and not integrated to scleral wound area in 25% rabbits of allogenic sclera group (p = .02), was out of the scleral wound in 33.3% rabbits of xenogenic HAM group (p > .05), all the grafts were at the normal location and viable in autogenic PRF group. The inflammation and vascularization in autogenic PRF group was significantly lower than negative control and xenogenic HAM groups in HE (p < .001). The collagen score of negative control and xenogenic HAM groups were significantly lower than normal control (p < .001) and autogenic PRF (p < .001) groups. There were insignificant differences between allogenic sclera and autogenic PRF groups (p > .05). For immunohistochemistry, the closest values to normal control group were detected in autogenic PRF group for all immunomarkers. Conclusion: Autogenic PRF showed superior features via its excellent anatomical and chemical composition for scleral regeneration when compared to single-layered xenogenic HAM and allogenic sclera grafts.

Efficacy of collagen matrix implant on adhesions in restrictive strabismus: An experimental study in a rabbit model

PURPOSE

To determine the efficacy of a biodegradable collagen matrix implant (Ologen, Aeon Astron Europe BV, Leiden, the Netherlands) in reducing adhesions in a rabbit model of restrictive strabismus.

METHODS

A prospective, masked-observer, controlled experimental study was performed. Sixty superior rectus muscles of 30 rabbits were resected and Marlex mesh was fixed beneath the resected muscle using nonabsorbable suture. Forty eyes underwent one of two different procedures; the resected muscle was wrapped with preserved human amniotic membrane (AM group) or Ologen (Ologen group). Randomly selected 20 eyes served as controls. Eyes were enucleated at 4 weeks after surgery to measure the severity of adhesion using a push pull gauge. Histopathological examination was performed.

RESULTS

At postoperative week four, the average tensile strength of the myoscleral adhesion was significantly lower in the Ologen group (151.8 ± 42.7 gram force) compared to controls (347.9 ± 68.6 gram force) and AM group (193.0 ± 44.3 gram force) (p < 0.001 and p = 0.045, respectively). Ologen group showed significantly lower degree of acute inflammation, chronic inflammation and rectus muscle fibrosis compared with controls (all p < 0.01). The degree of chronic inflammation was significantly lower in the Ologen group compared with AM group (p = 0.012).

CONCLUSION

Compared to amniotic membrane, Ologen is more effective in reducing mesh-related extraocular muscle adhesions in a rabbit model of restrictive strabismus.

Amniotic Membrane Transplantation in Strabismus Surgery

PURPOSE

Adhesions between the extraocular muscles and surrounding tissues pose a main cause of failure of strabismus reoperations. Amniotic membrane (AM) transplantation during extraocular muscle surgery, to prevent the formation of adhesions, has been a subject of research during the past decade. This review aims to determine the value, indications, and tips on usage of AM transplantation during strabismus surgery.

MATERIALS AND METHODS

All references cited in PubMed in English were searched using the key words: amniotic membrane strabismus or amniotic membrane extraocular muscles, and a brief summary of these was described. In addition, certain articles were chosen to provide introductory information on wound healing and fibrosis, AM properties and how it works after transplantation, and AM processing and preservation.

RESULTS

AM used for transplantation during extraocular muscle surgery may be cryopreserved, dried, or fresh. It may be oriented with its stroma or epithelium towards the muscle. It may or may not be fixed with sutures. What were the best choices? Various studies attempted to answer these questions. Many of the studies reviewed, however, were inconclusive or contradictory. Fresh AM seemed effective, but carried a risk of transmission of communicable diseases. Dried membrane was not of value in preventing adhesions. Histopathologically, cryopreserved membrane prevented the development of adhesions in the region of its presence, regardless of its orientation, and without the need for suture fixation. To accentuate this histopathological effect during clinical practice, it was recommended to utilize the largest segment possible of cryopreserved membrane and limit its usage to cases where adhesions are expected to be the main cause of failure of strabismus surgery.

CONCLUSION

Cryopreserved AM transplantation was safe and histopathologically effective in preventing adhesions. This effect was, however, less pronounced clinically. Its use during strabismus reoperations is merited if previous recommendations and precautions are considered.

Long-term follow-up of cryopreserved amniotic membrane transplant during strabismus reoperations: Up 85 months' follow-up

PURPOSE

To evaluate the long-term effect of cryopreserved human amniotic membrane transplant during strabismus reoperations.

METHODS

A total of 15 patients with persistent strabismus were included in a prospective study to evaluate the effect of wrapping the extra-ocular muscles with cryopreserved amniotic membrane during strabismus reoperations. The study end-point was the last follow-up visit. A successful outcome was defined as 0-10∆ of horizontal tropia and 0-4∆ of vertical tropia, with no limitation of ductions exceeding -1. A cosmetically acceptable outcome was defined as a tropia of 0-15∆.

RESULTS

Maximum follow-up was 85 months (mean: 25.4 ± 25.5 months). At the last follow-up visit, a successful outcome was achieved in 46.7%, a cosmetically acceptable outcome was achieved in 66.7%, and the mean ocular deviation angles improved from 38.60 ± 14.63∆, preoperatively, to 10.6 ± 11.08∆. Motility limitation on the final follow-up visit exceeded -1 in only 4/180 muscles (2.2%).

CONCLUSION

The effect of cryopreserved amniotic membrane transplantation on the success of strabismus reoperations was moderate in terms of ocular alignment. Its effect was more pronounced in terms of ocular motility. The latter better reflects the level of adhesions. No long-term complications were documented, denoting safety of cryopreserved amniotic membrane usage during strabismus reoperations.

Ulinastatin Supplementation During Human Amniotic Membrane Preservation to Improve its Viability

PURPOSE

The amniotic membrane (AM) is the transparent innermost layer of the placenta and it facilitates rapid wound healing in a diversity of ocular surface disorders. However, extended periods of cryopreservation before use induce significant impairment of cell viability due to oxidative stresses and inflammatory responses. We investigated the effect of supplementing ulinastatin (ULI), a known serine protease inhibitor, and relevant mechanisms of action in AM preservation solution through the hypothermic continuum on inflammatory and apoptotic signals and viability of AM tissue.

MATERIALS AND METHODS

The expression of inflammatory signal factors, including high mobility group box 1 (HMGB1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and anti-TNF-inducible gene 6 (TSG-6) which is a TNF-α-inducible anti-inflammatory protein, and the expression of apoptotic signal factors, including caspase (Cas)-9 and Cas-8, the initiators, and Cas-3, the executioner caspase and Bax were analyzed with or without ULI during hypothermic preservation of human AM. Subsequently, the actual viability of human AM tissue was verified with or without ULI supplementation throughout hypothermic continuum (both hypothermic- and cryopreservation).

RESULTS

Hypothermic AM preservation with ULI for 48 h resulted in downregulated expression of cold-inducible inflammatory factors, including HMGB1 and NF-κB, as well as RIPK3. In addition, ULI suppressed apoptotic signals related with Cas-9, Cas-8, and Cas-3 under hypothermic conditions. Furthermore, ULI supplementation during hypothermic- and cryopreservation of AM significantly enhanced viability of AM tissue and amniotic epithelial cells.

CONCLUSIONS

Supplementation of ULI during human AM preservation through the hypothermic continuum may be a feasible dual anti-inflammatory and anti-apoptotic strategy that enhances the viability of AM tissue.

A comparative study of different amniotic membrane orientations during extraocular muscle surgery in rabbits

PURPOSE

To histopathologically compare the effect of different orientations of cryopreserved human amniotic membrane (AM) transplant during extraocular muscle surgery in rabbits.

METHODS

Fifty-two albino rabbit eyes underwent 4-mm resection of the superior rectus. Eyes were randomly divided into four groups. In Group C (Control group, 16 eyes) the muscle was not wrapped with amniotic membrane. In the three AM groups, cryopreserved AM was wrapped around the muscle, oriented with either its stroma (Group S, 15 eyes) or epithelium (Group E, nine eyes) towards the muscle, or folded on itself with the epithelium externally (Group F, 12 eyes). The rabbits were sacrificed and the eyes were enucleated 6 weeks after surgery. Histopathological examination was conducted for periamniotic, foreign body, scleral, and conjunctival inflammation, conjunctival vascularity, adhesions and muscle fibrosis.

RESULTS

In all AM eyes, the AM was surrounded by periamniotic inflammation, with no adhesions detected between the muscle and surrounding tissues in the segment where the AM was present, but detected elsewhere. Adhesions were detected in all group C eyes. Foreign body inflammation was significantly less in Group C than in each of the AM groups (p < .05), but was insignificantly different among the three AM groups (p > .05). Scleral inflammation was absent in all specimens. No significant differences were noted among all groups in terms of conjunctival vascularity, conjunctival inflammation, or muscle fibrosis (p > .05).

CONCLUSIONS

All AM orientations were equally effective in preventing the development of postoperative adhesions between the extraocular muscle and surrounding tissues.

Cryopreserved rabbit amniotic membrane alleviated inflammatory response and fibrosis following experimental strabismus surgery in rabbits

We evaluate the ability of cryopreserved rabbit amniotic membrane (AM) transplantation to reduce postoperative inflammation and the extent of fibrosis following experimental strabismus surgery. Ten white rabbits underwent bilateral superior rectus (SR) muscle resection. In the left eye, the resected SR muscle was wrapped with cryopreserved rabbit AM. The right eye underwent SR resection only and served as a control. The eyes were enucleated 4 weeks after strabismus surgery. The degree of postoperative inflammatory infiltration, the extent of fibrosis, and profile of the relative expression of inflammatory mediators in the SR muscle were evaluated and compared between the two groups by histological analysis and real-time polymerase chain reaction (PCR). There were statistically meaningful differences in the degree of postoperative inflammatory infiltration and extent of fibrosis between the eyes treated with cryopreserved rabbit AM after SR resection and those underwent SR resection only. A significant decrease in the expression of inflammatory cytokines [interleukin (IL)-12a, IL-12b, IL-17f, and tumor necrosis factor- alpha (TNF-α)], and a markedly increased expression of anti-inflammatory cytokines (transforming growth factor-beta-1(TGFβ-1) and IL-10) were observed in the eyes treated with cryopreserved rabbit AM. In this study, we demonstrate that cryopreserved rabbit AM is effective in reducing postoperative inflammation and extent of fibrosis in a rabbit model of strabismus surgery. Our results imply that cryopreserved AM allograft has anti-inflammatory and anti-scarring properties that can prevent postoperative adhesions following strabismus surgery.

Placental Membranes for Management of Refractory Cutaneous Sinus Tracts of Surgical Origin: A Pilot Study

Despite advances in surgical technique, postoperative complications may lead to refractory cutaneous sinus tracts or tunnels. Negative pressure wound therapy is difficult to apply in longer tracts with a narrow diameter opening and conservative treatment failures ultimately necessitate surgical revisions. The aim of this pilot study was a clinical utility assessment of two different commercial placental membrane products for refractory cutaneous sinus tracts of surgical origin. Patients were treated with viable cryopreserved placental membrane (vCPM, n = 6) or devitalized dehydrated amnion/chorion membrane (dHACM, n = 6). The primary outcome measurement was the proportion of complete sinus tract depth resolution without exudate. Secondary endpoints included 4-week percent reduction in sinus tract probing depth and peri-tract wound surface area, days and number of grafts to resolution, number of wound-related infections, and 1-year recurrence rate for closed sinus tracts. All vCPM patients demonstrated complete sinus tract resolution compared to zero closures in the dHACM group (p = 0.00216). The vCPM group achieved greater percent reduction in probing depth (73.3 ± 21.9 versus −4.4 ± 91.3) and surrounding wound surface area (34.8 ± 86.8 versus −279.3 ± 454.9) at 4 weeks than dHACM. The use of viable intact cryopreserved placental membrane has demonstrated positive clinical outcomes for the treatment for refractory exudative sinus tracts and may be an alternative to repeat surgical intervention.

A controlled study of the role of cryopreserved amniotic membrane transplant during strabismus reoperations

PURPOSE

To evaluate the effects of using cryopreserved human amniotic membrane (AM) transplant during strabismus reoperations.

METHODS

A total of 30 patients with persistent strabismus were included in this prospective study. Patients were divided into two groups of 15 patients each. The AM group underwent strabismus reoperation with wrapping of the muscles with cryopreserved amniotic membrane. Controls underwent strabismus reoperation without an AM wrap. Final follow-up visit was scheduled between 3 and 12 months postoperatively. Surgical success was defined as 0^Δ-10^Δ of horizontal tropia and 0^Δ-4^Δ of vertical tropia, with no limitation of ductions exceeding -1. A cosmetically acceptable outcome was defined as a tropia of 0^Δ-15^Δ.

RESULTS

Three patients were excluded in the AM group due to incomplete follow-up. A successful outcome was achieved in 7 patients in each group (58% and 47% in groups AM and C, resp.; P = 0.63). A cosmetically acceptable outcome was achieved in 10 patients in the AM group (83.3%) and 12 (80%) in the control group (P = 0.48). The mean ocular deviation angles improved to 8.7^Δ ± 12^Δ in the AM group and 12.3^Δ ± 17.4^Δ in the control group (P = 0.63). Ductions improved in 66.7% and 36.4% of the muscles with limited motility in groups AM and C, respectively (P = 0.019).

CONCLUSIONS

Wrapping the extraocular muscles with cryopreserved AM during strabismus reoperations was of limited clinical benefit. We attributed this to the small segment of AM used and to the presence of other causes of failure rather than adhesions.

Antifibrotic Effects of Human Amniotic Membrane Transplantation in Established Biliary Fibrosis Induced in Rats

Liver fibrosis is characterized by excessive accumulation of extracellular matrix components in the liver parenchyma that distorts the normal architecture and hepatic function. Progressive fibrosis could end in the advanced stage known as cirrhosis, resulting in the need to resort to liver transplantation. Amniotic membrane (AM) has emerged as an innovative therapeutic approach for chronic liver diseases due to its anti-inflammatory, antiscarring, and wound-healing effects. We have recently shown that AM can be used as a patch on the liver surface at the same time of fibrosis induction, resulting in significantly reduced progression and severity of biliary fibrosis. Here we investigated the effects of human AM on the established rat model of liver fibrosis, induced by the bile duct ligation (BDL). We also explored the effect of AM on the expression of transforming growth factor-1 (TGF-1), the main profibrogenic factor in hepatic fibrosis, and the proinflammatory cytokines, tumor necrosis factor- (TNF-), interleukin-6 (IL-6), and anti-inflammatory cytokine IL-10. Two weeks after BDL, the liver was covered with a fragment of AM or left untreated. Six weeks later, the fibrosis was first assessed by the semiquantitative Knodell and the METAVIR scoring systems and, thereafter, by CellProfiler digital image analysis to quantify the area occupied by collagen deposition, ductular reactions (DRs), activated myofibroblasts, and TGF-1. The hepatic cytokines were determined by ELISA. AM-treated rats showed a significantly lower score compared to the control BDL rats (2.50.9 vs. 3.50.3, respectively; p0.05). The collagen deposition, DRs, number of activated myofibroblasts, and TGF-1 were all reduced to about 50% of levels observed in untreated BDL rats. These findings suggest that AM, when applied as a patch onto the liver surface, is useful for treating well-established cholestatic fibrosis, and the mechanism was partly by means of downregulating the profibrotic factor TGF-1 and IL-6.

Restrictive problems related to strabismus surgery

Strabismus surgery may be responsible for some restrictions in ocular motility that may cause new problems after surgery. Most of the time these restrictions present as a complex motility problem after surgery that requires further treatment. There may be various reasons that cause motility restriction following strabismus surgery. Those are excessive shortening or inadvertent capture of extraocular muscles, transposition procedures and, the most challenging problem, postoperative scar tissue-adhesion formation. In this review the potential reasons for postoperative restrictive problems, preventive measures and finally the treatment options for such problems are overviewed.

Reduction in Rectus Muscle Recession Depending on the Distance Between Rectus Muscle Suture Placement and Scleral Insertion in Rabbit Eyes

PURPOSE

To quantitatively determine how a large tendon remnant reduces the effect of the rectus muscle recession procedure with respect to the distance between the placement of the muscle suture and the scleral insertion.

METHODS

Thirty-six eyes from 18 rabbits were randomly divided into four groups according to the distance between the superior rectus muscle suture placement and the scleral insertion (1, 2, 3, and 4 mm). The superior rectus muscle was sutured at the previously listed distances from the insertion. Each superior rectus muscle was reattached using a scleral pass at a site 4 mm posterior to its original insertion. The amount of recession was measured as the distance between the most anterior aspect of the reattached muscle and the original insertion site.

RESULTS

The mean amount of recession was 4.07 ± 0.25 mm in the 1-mm group and 2.76 ± 0.55 mm in the 4-mm group at postoperative week 4. There were significant differences in the amount of recession between the four groups. Linear regression analyses revealed a significant relationship between the distance of the muscle suture placement from the scleral insertion and the amount of recession (r(2) = 0.521). The superior rectus muscle was estimated to be reattached 0.437 mm anterior to the desired location for every 1 mm that the muscle suture was placed posterior to the scleral insertion.

CONCLUSIONS

The potential error that depends on the distance between the muscle suture placement and the scleral insertion should be considered to reduce undercorrection and ensure a good surgical outcome.

Long-term efficacy of glycerine-processed amniotic membrane transplantation in patients with corneal ulcer

PURPOSE

The aim of this study was to determine the long-term treatment efficacy of glycerine-preserved human amniotic membrane transplantation in patients suffering from corneal ulcers.

METHODS

This was a retrospective, non-controlled, monocentric analysis. Included were patients with corneal ulcers that were non-responsive to ointment or contact lenses and had been treated by amniotic membrane transplantation with either the overlay or sandwich procedure. Analysis parameters were visual acuity before and following treatment, recurrence rate and subjective comfort at the last follow-up.

RESULTS

Of the 371 amniotic membrane transplantations that were conducted, 135 surgical treatments in 108 patients (51.9% male, 48.1% female; mean age 63.7 years) met the inclusion criteria. In total, 99 overlay and 36 multilayer amniotic membrane transplantations were performed. The follow-up period was 47.5 ± 66.7 weeks (mean ± SD). The recurrence rate at the last follow-up was 47.8% with overlay membranes and 51.8% with the sandwich technique. There was no significant change in best-corrected visual acuity following treatment with overlays (p = 0.219) or sandwich procedure (p = 0.703). At the last follow-up, 72.1% (overlay) and 78.3% (sandwich) of the patients reported either no pain or increased comfort.

CONCLUSION

The recurrence rates and changes in visual acuity following overlay or sandwich amniotic membrane transplantation in patients suffering from corneal ulcer were lower than reported elsewhere in the literature. More than half of the patients profited from each of the amniotic membrane transplantation techniques with respect to recurrence and postoperative comfort.

Amniotic membrane for reducing the formation of adhesions in strabismus surgery: experimental study in rabbits

PURPOSE

To evaluate the effect of amniotic membrane in reducing inflammation, fibrosis, adhesion formation, and ocular motility restrictions following strabismus surgery.

METHODS

In the first stage of this prospective, randomized study, 17 rabbits underwent superior rectus muscle recession in both eyes. Surgery was performed in the same manner, but human amniotic membrane was placed over the muscle without sutures in the right eye after recession. After 15 days, the rabbits were killed and their orbits were exenterated and evaluated histopathologically to quantify tissue inflammation and fibrosis. In the second stage, 5 rabbits underwent the same procedure but were killed after 30 days. A dynamometer was used to measure the force required to displace all eyes.

RESULTS

At 15 days postoperatively, eyes with amniotic membrane exhibited an increased inflammatory response and less fibrosis than eyes without amniotic membrane. At 30 days postoperatively, eyes with amniotic membrane continued to exhibit increased inflammation and less fibrosis than eyes without amniotic membrane. In the dynamometer test, more force was needed to displace eyes without amniotic membrane after 15 days, but there was no significant difference between the forces required at 30 days.

CONCLUSIONS

Human amniotic membrane in rabbits led to an increase in the inflammatory process and a decrease in fibrosis formation following strabismus surgery.

Tissue response to implanted Ahmed glaucoma valve with adjunctive amniotic membrane in rabbit eyes

AIMS

To investigate the histopathology of the fibrous capsule around Ahmed glaucoma valves (AGVs) implanted with adjunctive amniotic membranes in rabbits.

METHODS

AGV implantation with or without adjunctive amniotic membrane was performed in a single eye of 20 albino rabbits. The upper surface of the AGV body was covered with amniotic membrane in the study group. After 2 months, histology was used to compare the thickness and characteristics of the fibrous capsule, transdifferentiation of myofibroblasts, and density of blood vessels and leukocytes between the study and control groups.

RESULTS

The fibrous capsule along the roof of the bleb was composed of compact collagen fibers with minimal vascularization in the control group. In contrast, in the study group, the fibrous capsule was looser and had a more disorganized collagen architecture. The thickness of the fibrous capsule and the myofibroblast layer was significantly thinner in the study group than in the control group (p < 0.001). The number of CD31-positive blood vessels did not differ between the two groups (p = 0.235). CD45-positive inflammatory cells were more frequently observed in the study group than the control group (p = 0.001). The groups did not differ in the thickness of the fibrous capsule or myofibroblast layer, or the density of blood vessels and leukocytes along the floor of the bleb.

CONCLUSIONS

Adjunctive amniotic membranes could reduce the risk of encapsulation and aqueous outflow resistance by altering the tissue response to implanted AGVs and subsequent formation of a loose thin capsule.