Transthyretin synthesis in rabbit ciliary pigment epithelium

Ocular findings in patients with acquired ATTRv amyloidosis following domino liver transplantation

PURPOSE

To investigate the presence of amyloidosis-related ocular findings in patients who received domino liver transplantation from ATTRv amyloidosis donors.

METHODS

We reviewed the ocular findings in patients who had previously undergone domino liver transplantation and received ophthalmologic examinations between January 2009 and March 2023. The presence of amyloidosis-related ocular findings was retrospectively assessed by two ophthalmologists.

RESULTS

During the study period, a total of 7 patients with 14 eyes were examined. All patients were considered as acquired ATTRv amyloidosis. The mean age at the final visit was 64.6±8.4 years (52-75 years), and the mean time since domino liver transplantation was 167.6±76.2 months (69-257 months). The two evaluators' assessments for amyloidosis-related ocular findings were completely identical. No amyloid fibril deposition was observed in the pupil, lens, or vitreous. Five patients (10 eyes) had a Schirmer test result of 5mm or less than 5 mm, and four patients with a total of 8 eyes underwent fluorescein angiography and indocyanine green angiography, and no evidence of retinal amyloid angiopathy was found on fluorescein angiography. However, three patients with 6 eyes showed choroidal amyloid angiopathy on indocyanine green angiography.

CONCLUSION

While cases of choroidal amyloid angiopathy were observed, serious amyloidosis-related ocular complications such as vitreous opacity or secondary glaucoma did not occur even in the long term after domino liver transplantation.

Long-term surgical results of trabeculectomy for secondary glaucoma in Val30Met hereditary transthyretin amyloidosis

This study reports the long-term results of trabeculectomy (LEC) for secondary glaucoma in hereditary transthyretin (ATTRv) amyloidosis patients and its correlation with prior vitrectomy. A retrospective case series was conducted involving 31 consecutive eyes of 20 ATTRv amyloidosis patients who underwent LEC between 2007 and 2020. The mean follow-up period was 73.2 ± 37.0 months (range: 20-181 months). Postoperative intraocular pressures (IOPs) were evaluated based on the following criteria: (a) IOP between 6 and 21 mmHg without additional glaucoma surgeries, except for laser suture lysis, (b) IOP between 6 and 15 mmHg without additional glaucoma surgeries, except for laser suture lysis, and (c) IOP between 6 and 21 mmHg without additional glaucoma surgeries, except for needling and laser suture lysis. Kaplan-Meier analysis revealed survival rates after LEC of 0.52 at 36 months, 0.42 at 60 months, and 0.25 at 84 months under criterion (a); 0.49 at 36 months, 0.27 at 60 months, and 0.11 at 84 months under criterion (b); and 0.76 at 36 months, 0.71 at 60 months, and 0.65 at 84 months under criterion (c). Eyes with a history of small gauge transconjunctival vitrectomy (SGTV) exhibited a tendency towards lower survival rates, although no statistically significant difference was observed (log-rank test; p = 0.193 under criterion (a) and p = 0.0553 under criterion (b)). Our findings suggest that LEC and additional needling procedures can provide some control over IOP; however, the overall postoperative outcomes of LEC for ATTRv amyloidosis remain unsatisfactory, even in the era of SGTV with reduced conjunctival scarring.

Modified Technique of Ex-PRESS® Filtration Device Combined with a Scleral Pocket for Hereditary Transthyretin Amyloidosis (hATTR) Secondary Open-Angle Glaucoma

Purpose

To evaluate the effectiveness and safety of a modified approach using the Ex-PRESS^® implant combined with a scleral pocket in the management of secondary open-angle glaucoma in hereditary transthyretin amyloidosis (hATTR) at our department.

Methods

This was a retrospective analysis. The primary endpoints included Intraocular pressure (IOP) evaluation (baseline, 1st day, 1st week, 1, 3, 6, 12 months and at last follow-up) and number of hypotensive drugs (baseline, 6th, 12th months and at last follow-up). As secondary endpoints surgical complications, the need for additional glaucoma surgery and LogMAR BCVA were evaluated. Qualified and complete success were defined as ≥ 30% IOP decrease from baseline, with or without additional medications, respectively. The minimum follow-up was 12 months.

Results

A total of 32 eyes were included with a mean follow-up of 2.4±2.9 years. IOP decreased significantly from baseline (27.4±4.4 mmHg) to 1st day (5.00±2.9 mmHg), 1st week (6.9±4.1 mmHg), 1st month (11.7±7.8 mmHg), 3rd month (11.6±6.1 mmHg), 6th month (13.1±6.8 mmHg), 12th month (12.0±3.5 mmHg) and last visit (11.8±2.4 mmHg), p<0.001. There was also a significant reduction in the number of antiglaucoma medications from baseline (3.8±0.6) and last follow-up (0.4±0.8), p<0.001. LogMAR BCVA remained stable (0.25±0.26 at baseline and 0.25±0.24 at last follow-up), p=0.767. Transient hypotony occurred in 17 eyes (53.1%), but only 11 (34.4%) exhibited anterior chamber shallowing and needed additional care, namely cycloplegic drops and viscoelastic injection. Complete surgical success was achieved in 22 eyes (68.8%) and qualified success in 6 eyes (18.8%). Four eyes (12.5%) needed additional glaucoma surgery.

Conclusion

The modified ExPRESS^® technique appears to be effective, especially when low levels of IOP are required. Additionally, fewer anti-glaucoma drugs were necessary. In the other hand, hypotony was a common side effect with this procedure, although all patients were properly handled, preserving the surgical outcomes.

Does Patisiran Reduce Ocular Transthyretin Synthesis? A Pilot Study of Two Cases

BACKGROUND

Variant transthyretin-mediated amyloidosis (ATTR-v) is a well-characterized disease affecting the neurologic and cardiovascular systems. Patisiran has been approved for neurologic involvement as it reduces hepatic synthesis of transthyretin (TTR). Eye involvement is a lateonset feature increasing the risk of glaucoma and cataracts in patients.

AIMS

The aim of this case series was to assess whether patisiran can effectively reduce TTR synthesis in such a barrier-protected organ as the eye.

METHODS

Two patisiran-treated ATTR-v patients underwent serum and aqueous humor sampling to measure TTR levels detected by SDS-PAGE and immunoblotting. Serum samples were compared to healthy control (HC), whereas aqueous humor samples were compared to non-amyloidotic subjects affected by cataracts and glaucoma.

RESULTS

Serum TTR levels representative of hepatic synthesis were sharply lower in treated patients if compared to the HC (-87.5% and -93.75%, respectively). Aqueous humor TTR levels showed mild-tono reduction in treated patients compared to non-amyloidotic subjects with cataracts (-34.9% and +8.1%, respectively) and glaucoma (-41.1% and -2.1%).

CONCLUSION

Patisiran does not seem to be as effective in inhibiting ocular TTR synthesis as it is in inhibiting hepatic synthesis. Re-engineering the envelope could allow the drug to target RPE cells thus avoiding any ocular involvement.

Microhook ab interno trabeculotomy for secondary glaucoma in patients with hereditary transthyretin amyloidosis

PURPOSE

To report surgical outcomes of a Microhook ab interno trabeculotomy (µLOT) procedure for glaucoma secondary to hereditary transthyretin amyloidosis (ATTRv).

STUDY DESIGN

Retrospective case series.

METHODS

Medical records of patients with glaucoma secondary to ATTRv with transthyretin Val30Met variant, who underwent µLOT, were retrospectively reviewed. Surgical success was categorized according to the postoperative intraocular pressures (IOPs, mmHg) as follows: (a) 6 ≤ IOP ≤ 21; (b) 6 ≤ IOP ≤ 18; and (c) 6 ≤ IOP ≤ 15, without light perception loss or additional glaucoma surgery. Secondary outcomes were glaucoma medication scores and postoperative complications.

RESULTS

This study included 18 eyes (13 patients, 6 men). The mean follow-up period was 25.2±9.8 months (7-38 months). Kaplan-Meier analysis indicated success rates of (a) 1.00 at 6, 1.00 at 12, and 0.43 at 24 months; (b), 1.00 at 6, 0.93 at 12, and 0.43 at 24 months; (c) 0.94 at 6, 0.75 at 12, and 0.27 at 24 months after operation. Postoperative IOPs were significantly reduced from the baseline of 25.2±5.8 mmHg to 11.5±2.7 at 3, 12.3±4.1 at 6, and 13.8±3.9 at 12 months (Dunnett's test). Medication scores were also improved at 3 and 6 months but without a significant reduction at 12 months. There were no severe complications requiring surgical intervention except for additional glaucoma surgery.

CONCLUSION

µLOT for secondary glaucoma in ATTRv is safe and effective 1 year after surgery, but the effects diminish after 2 years.

Suture trabeculotomy ab interno for secondary glaucoma in Japanese patients with Val30Met hereditary transthyretin amyloidosis

We retrospectively evaluated surgical outcomes of suture trabeculotomy (SLOT) ab interno for secondary glaucoma in 18 eyes of 12 patients with hereditary transthyretin (ATTRv) amyloidosis with Val30Met mutation. SLOT ab interno was performed between May 2015 and January 2020. All the participants were followed up for at least 12 months. The primary outcome measure was Kaplan-Meier survival. Failure of this treatment was defined as an intraocular pressure (IOP) of ≥ 22 mmHg and a < 20% IOP reduction with or without medication or as additional operations needed to reduce IOP. The mean postoperative follow-up period was 3.5 years (1.2-6.1 years). The SLOT ab interno procedure alone was performed in 17 eyes (94%). Fifteen eyes (83%) had a 360° incision made in Schlemm's canal and 3 eyes (17%) had a 180° incision performed. Cumulative survival values were 0.83, 0.63, and 0.22 at 1, 2, and 3 years, respectively. Ten eyes (56%) needed additional surgery, such as repeated SLOT ab interno, Ahmed glaucoma valve implantation, or MicroPulse transscleral cyclophotocoagulation. Our results here, as well as our previous results with trabeculectomy, suggest that SLOT ab interno may not have a sufficiently long-term effect on secondary glaucoma because of ATTRv amyloidosis.

Application of optical coherence tomography angiography to assess systemic severity in patients with hereditary transthyretin amyloidosis

Hereditary transthyretin amyloidosis is an autosomal dominant form of amyloidosis caused by an abnormality in transthyretin, with various ocular manifestations. Among these, ocular amyloid angiopathy has attracted attention because of its direct link to visual impairment and its correlation with systemic severity. We hypothesized that optical coherence tomography angiographic parameters would be useful biomarkers of amyloidosis systemic severity and investigated their correlation with the systemic severity score. The primary outcome was the correlation between the systemic severity score and choriocapillaris flow deficit percentage. Secondary outcomes were the correlations between the systemic severity score and retinal optical coherence tomography angiographic parameters, including foveal avascular zone size and circularity and superficial/deep/total retinal perfusion and vessel densities. The choroidal and retinal vasculature was quantified in 36 eyes from 36 patients (age, 51.8±12.1 years; disease duration, 13.4±6.2 years). Ten eyes had a history of vitrectomy for vitreous opacity. Choriocapillaris flow deficit percentage was not significantly correlated with the systemic severity score (Spearman’s rank correlation: r = 2.96×10⁻², p = 0.863). Similarly, foveal avascular zone size and circularity, and superficial/deep/total retinal perfusion and vessel densities were not significantly correlated with the systemic severity score. These results may indicate that optical coherence tomography angiographic parameters are not sufficient to predict amyloidosis severity.

Transthyretin: Its function and amyloid formation

Transthyretin (TTR), which is one of the major amyloidogenic proteins in systemic amyloidosis, forms extracellular amyloid deposits in the systemic organs such as nerves, ligaments, heart, and arterioles, and causes two kinds of systemic amyloidosis, hereditary ATTR (ATTRv) amyloidosis induced by variant TTR and aging-related wild-type ATTR (ATTRwt) amyloidosis. More than 150 different mutations, most of which are amyloidogenic, have been reported in the TTR gene. Since most disease-associated mutations affect TTR tetramer dissociation rates, destabilization of TTR tetramers is widely believed to be a critical step in TTR amyloid formation. Recently, effective disease-modifying therapies such as TTR tetramer stabilizers and TTR gene silencing therapies have been developed for ATTR amyloidosis. This study reviews the clinical phenotypes of ATTR amyloidosis, TTR features, and recent progress in promising therapies for ATTR amyloidosis.

Ahmed valve for secondary glaucoma in patients with hereditary transthyretin amyloidosis

OBJECTIVE

To evaluate the surgical outcomes of patients with hereditary transthyretin amyloidosis (TTR-FAP) who underwent Ahmed glaucoma valve (AGV) implantation.

METHODS

A retrospective cohort study was performed on patients with a diagnosis of TTR-FAP secondary glaucoma, who underwent AGV implantation in our department, between November 2010 and July 2019. The cumulative probability of treatment success was measured with Kaplan-Meier survival analysis. The primary outcome was success, defined as intraocular pressure (IOP) ≥ 6 mmHg and ≤21 mmHg with or without medication, with no need for further glaucoma surgery and without loss of light perception at last follow-up. Secondary outcomes were postoperative IOP, number of IOP-lowering medications, and rates of complications.

RESULTS

The study included 114 eyes of 87 patients. The mean follow-up duration was 3.81 ± 2.11 years (y) [range, 1.00-8.28 y]. Compared to the preoperative values, the mean IOP was reduced from 28.20 ± 7.01 to 12.87 ± 3.76 mmHg at the final visit (p < 0.001), with a reduction in the number of medications from 3.89 ± 0.66 to 1.86 ± 1.43 (p < 0.001). Early and late postoperative complications occurred in 20 (17.09%) and 9 (7.89%) eyes, respectively. Kaplan-Meier analysis indicated probabilities of success of 0.98 at 1 y, 0.97 at 2 y, 0.95 at 3 y, 0.89 at 4 y, 0.77 at 5 y and 0.72 at 6 y. The linear correlation analysis showed a correlation between some characteristics of the natural history of TTR-FAP patients and AGV implantation success.

CONCLUSION

Although glaucoma in TTR-FAP patients is very difficult to manage, AGV implantation is an effective and relatively safe procedure.

The role of transthyretin in cell biology: impact on human pathophysiology

Transthyretin (TTR) is an extracellular protein mainly produced in the liver and choroid plexus, with a well-stablished role in the transport of thyroxin and retinol throughout the body and brain. TTR is prone to aggregation, as both wild-type and mutated forms of the protein can lead to the accumulation of amyloid deposits, resulting in a disease called TTR amyloidosis. Recently, novel activities for TTR in cell biology have emerged, ranging from neuronal health preservation in both central and peripheral nervous systems, to cellular fate determination, regulation of proliferation and metabolism. Here, we review the novel literature regarding TTR new cellular effects. We pinpoint TTR as major player on brain health and nerve biology, activities that might impact on nervous systems pathologies, and assign a new link between TTR and angiogenesis and cancer. We also explore the molecular mechanisms underlying TTR activities at the cellular level, and suggest that these might go beyond its most acknowledged carrier functions and include interaction with receptors and activation of intracellular signaling pathways.

ASSOCIATION BETWEEN CHOROIDAL CHARACTERISTICS AND SYSTEMIC SEVERITY IN AMYLOIDOSIS

PURPOSE

This study aimed to describe the choroidal features of ocular amyloidosis using multimodal imaging, to correlate these findings with systemic involvement, and to propose a choroidal grading system.

METHODS

Eleven patients with systemic amyloidosis were reviewed retrospectively. Each case was assigned a grade according to the severity of choroidal findings as determined by both enhanced depth imaging optical coherence tomography and indocyanine green angiography. The severity of systemic amyloidosis was then correlated with the choroidal involvement.

RESULTS

On indocyanine green angiography, all patients exhibited hyperfluorescent spots in the late stage and were classified according to preexisting criteria. On enhanced depth imaging optical coherence tomography, hyperreflective foci were seen in the choriocapillaris and Sattler's layer in Grade 1, partial loss of Sattler's layer was additionally seen in Grade 2, and a dense hyperreflective Haller's layer was seen in Grade 3. Choroidal grading scores were significantly correlated with the systemic severity score (P = 0.0014, Pearson's correlation coefficient; ρ = 0.83).

CONCLUSION

With ocular amyloidosis, evaluation of choroidal characteristics using multimodal imaging may serve as a biomarker for systemic involvement.

Transscleral Cyclophotocoagulation in Familial Amyloidotic Polyneuropathy Secondary Glaucoma after Ahmed Valve Implantation: A Case Series Study

Purpose

To investigate the outcomes of transscleral cyclophotocoagulation (TSCPC) after Ahmed glaucoma valve (AGV) implantation failure in patients with familial amyloidotic polyneuropathy (FAP) secondary glaucoma.

Materials and methods

In this retrospective study, all patients with secondary FAP glaucoma who underwent AGV implantation between 2010 and 2019 in our tertiary center were assessed. Among all, those patients who needed TSCPC to control intraocular pressure (IOP) after AGV were selected. Demographic data, value of IOP, best-corrected visual acuity (BCVA), number of antiglaucomatous medications, surgical complications, and need for retreatment were collected.

Results

From a total of 124 eyes submitted to AGV implantation, 13 eyes (10.48%) needed TSCPC to control IOP. The median age at TSCPC was 49.50 years (43; 55.75), and the median period between AGV implantation and TSCPC was 1.63 years (1.00; 3.65). There was a significant decrease of IOP after the procedure, from 24.33 ± 4.76 to 11.33 ± 2.90 mm Hg at last visit (p < 0.001). A reduction in the number of antiglaucomatous medications was also noticed, from 3.92 ± 0.29 to 1.25 ± 1.42 (p < 0.001). There was no difference in BCVA (p = 0.502). After the procedure, there was an exuberant anterior chamber (AC) reaction in two eyes (16.7%), and one case developed a neurotrophic ulcer (8.3%). There was no need for re-treatment.

Conclusion

Ahmed glaucoma valve implantation is a promising surgical procedure to treat patients with PAF secondary glaucoma, showing good results. For refractory cases, TSCPC seems to be effective and safe to control IOP.

Clinical significance

There are only a few studies in current literature that address amyloid secondary glaucoma, maybe because it is a rare pathology worldwide. However, it has a high incidence in certain regions, including the north of Portugal. For the record, this is the first study describing the tool of cycloablative procedures in this type of glaucoma.

How to cite this article

Vieira R, Marta A, Figueiredo A, et al. Transscleral Cyclophotocoagulation in Familial Amyloidotic Polyneuropathy Secondary Glaucoma after Ahmed Valve Implantation: A Case Series Study. J Curr Glaucoma Pract 2021;15(1):32–35.

Review of proteomics approach to eye diseases affecting the anterior segment

Visual impairment and blindness is a major health burden worldwide, and major ocular diseases causing visual impairment pertain to the anterior segment of the eye. Anterior segment ocular diseases are common, yet complex entities. Although many treatment options and surgical techniques are available for these ailments, the underlying cause and pathogenesis is still unclear. Finding ways to fundamentally treat these patients and rectify the underlying dysregulations leading to the disease may help cure patients completely without major complications. Proteomics approaches are a novel way to distinguish dysregulated proteins in a variety of biological tissues in a hypothesis-free manner, thus helping to find the responsible pathways leading to a certain disease. The aim of the current study is to review the available knowledge in scientific literature regarding the proteomics studies done on anterior segment eye diseases and suggest potential clinical implications to exploit the results of these studies. SIGNIFICANCE: Anterior segment ocular diseases are responsible for a major proportion of visual impairment and blindness worldwide. Although ophthalmologists have several treatment options that can alleviate or control the progression of these diseases, no definite cure is available for most of them. Moreover, because these diseases are progressive, prompt diagnosis is of utmost important. Proteomics studies enable us to identify and quantify the dysregulated proteins in a biological specimen in a hypothesis-free manner. Understanding the dysregulated protein pathways shines a light on the pathogenesis of the disease. Moreover, these dysregulated proteins may act as biomarkers to help in diagnosis and treatment follow-up. Hence, in this article we sought out to review the available scientific literature regarding the proteomics studies of anterior segment ocular diseases and to identify potential applications of proteomic studies in clinic.

Small gauge vitrectomy for vitreous amyloidosis and subsequent management of secondary glaucoma in patients with hereditary transthyretin amyloidosis

We conducted a retrospective observational study including 31 eyes of 20 patients in order to investigate the efficacy of 25-gauge vitrectomy for vitreous opacity with minimal conjunctival invasion and subsequent management of intraocular pressure (IOP) secondary to hereditary transthyretin amyloidosis. We followed up these patients for an average of 44.7 ± 32.6 months. The primary outcome was best corrected visual acuity (BCVA) at 1 month after surgery and at the final follow-up visit, with management of subsequent IOP elevation. Secondary outcomes included the post-vitrectomy IOP survival rate, to determine the frequency of IOP elevation requiring glaucoma surgery. Mean age at vitrectomy was 55.4 ± 9.1 years. Logarithm of the Minimum Angle of Resolution (LogMAR) BCVA showed immediate improvement from 0.73 ± 0.62 to 0.00 ± 0.22 at 1 month (p = 4.1 × 10⁻⁷), an improvement that was maintained up to the final follow-up visit, when IOP was maintained at 13.1 ± 5.2 mmHg. The survival rate of post-vitrectomy IOP control was 0.51, 0.38, and 0.23 at 12, 24, and 60 months, respectively. A poor post-vitrectomy IOP survival rate suggests that removing vitreous amyloid via 25-gauge vitrectomy is not sufficient to guarantee good visual function; subsequent careful follow-up and proper glaucoma management is also required in order to achieve this goal.

Conjunctival lymphangiectasia as a biomarker of severe systemic disease in Ser77Tyr hereditary transthyretin amyloidosis

AIMS

To investigate the relationship between the ophthalmic and systemic phenotypes in patients with hereditary transthyretin amyloidosis with the S77Y mutation (ATTRS77Y).

METHODS

In this cross-sectional study, patients with genetically confirmed ATTRS77Y amyloidosis were enrolled. All patients underwent complete neurological examination, including staging with the Neuropathy Impairment Score (NIS), Polyneuropathy Disability (PND) score; complete cardiological evaluation, including echocardiography, cardiac MRI and/or cardiac scintigraphy and complete ophthalmic evaluation, including slit lamp examination and fundus examination. Ocular ancillary tests (fluorescein and indocyanine green angiography, and anterior segment optical coherence tomography) were performed in cases with abnormal findings. The Kruskal-Wallis test was used for quantitative outcomes and Fisher's exact test for qualitative outcomes. Statistical significance was indicated by p<0.05 (two tailed).

RESULTS

The study sample was composed of 24 ATTRS77Y patients. The mean patient age was 58.4±12.4 years. None of the patients presented with amyloid deposits in the anterior chamber, secondary glaucoma or vitreous amyloidosis. Retinal angiopathy was observed in four patients, complicated with retinal ischaemia in one patient. Conjunctival lymphangiectasia (CL) was detected in 13 patients (54%), associated with perilymphatic amyloid deposits. The presence of CL was statistically associated with more severe neurological disease (NIS=43.3±31.9 vs 18.9±20.4; PND=2.6±1.0 vs 1.4±0.7 in patients with and without CL, respectively; both p<0.05) and amyloid cardiomyopathy (p=0.002).

CONCLUSION

In ATTRS77Y patients, CL is common and could serve as a potential biomarker for severe systemic disease. There were neither anterior chamber deposits, secondary glaucoma nor vitreous deposits in ATTRS77Y patients.

Multimodal retinal imaging of familial amyloid polyneuropathy

Background: Retinal amyloid angiopathy is a sight-threatening complication of familial amyloid polyneuropathy (FAP) caused by pathological deposition of transthyretin. The purpose of this report is to present ocular findings in patients with FAP using a combination of novel non-invasive retinal imaging techniques, including first time published images of optical coherence tomography angiography (OCT-A) in FAP.Materials and methods: Observational cross-sectional study of retinal images in patients with FAP using: fundus ultra wide-field photography (UWF); autofluorescence (AF); optical coherence tomography (OCT); and, OCT-A. Fifteen eyes of eight patients with FAP from a tertiary center were included. A descriptive analysis of obtained images and clinical data was performed.Results: Amyloid vitreous and retinal deposits were easily identified using OCT scans, AF, and UWF images, especially in the red-free modality. OCT-A allowed quality reconstruction of posterior pole vasculature, foveal avascular zone, and areas of ischemia.Conclusions: Different modalities of currently available non-invasive retinal imaging techniques, including OCT-A scans described for the first time in FAP, are safe and useful in detecting and analyzing retinal amyloidosis. Retinopathy in FAP in the studied group was more frequent than previously reported.

RE-INTERVENTION IN DE NOVO VITREOUS OPACITIES AFTER PARS PLANA VITRECTOMY IN FAMILIAL AMYLOIDOTIC POLYNEUROPATHY TTR VAL30METPORTUGUESE PATIENTS

PURPOSE

To report management of de novo vitreous amyloid opacities after previous pars plana vitrectomy in familial amyloidotic polyneuropathy transthyretin Val30Met.

METHODS

This work is a retrospective observational consecutive case series of five eyes of four patients. Demographic data, transthyretin mutation involved, age at the beginning of disease, duration of disease, treatment (liver transplant or tafamidis), time between vitrectomy and re-intervention, and ophthalmologic changes were evaluated. Surgical re-intervention included phacoemulsification with intraocular lens implantation in phakic eyes, re-vitrectomy as complete as possible with posterior capsulectomy, and internal limiting membrane peeling if wrinkling of internal retinal surface was present.

RESULTS

All patients had transthyretin Val30Met mutation, and three were women. Mean age of onset of the disease was 52 ± 11.0 years, and average evolution time of the disease was 8 years. Three patients had been submitted to liver transplant 4, 9, and 15 years before. Time between first vitrectomy and surgical re-intervention was longer than 2 years in all cases. Two eyes had amyloid deposits on anterior lens surface and pupillary border with scalloped pupil. Two eyes were phakic. Glaucoma was present in two eyes; one of them had previous trabeculectomy. All cases had vitreous opacities behind posterior lens capsule and at vitreous base area. After re-intervention, no further recurrence was observed (average follow-up of 10 months).

CONCLUSION

De novo vitreous amyloid opacities may occur several years after pars plana vitrectomy. Amyloid deposition in vitreous cavity was observed only in strong vitreous adherence locations (behind posterior lens capsule and at vitreous base area). The authors expect that this procedure, an extensive re-vitrectomy associated with posterior capsulectomy, will prevent de novo vitreous amyloid opacities.

Transthyretin deposition in the eye in the era of effective therapy for hereditary ATTRV30M amyloidosis

BACKGROUND

Ocular abnormalities have been known to occur in hereditary amyloidotic polyneuropathy since the 1950s. While vitreous opacities and scalloped pupils were described early it has become evident that every component of the eye from the conjunctiva to the retinal vasculature can be involved. Reports from the major centres in Japan, Portugal and Sweden, which primarily treat patients with ATTRV30M, have indicated that with the increased longevity seen in patients treated with liver transplantation the frequency of the more severe eye findings, notably vitreous opacities and subsequent glaucoma, are being detected more frequently.

METHODS

In an attempt to confirm that the experience was similar in a broader range of locales we performed a survey of ten treatment centres in eight countries to determine the frequency of severe ocular abnormalities (vitreous opacities and glaucoma) in 804 patients with V30M disease and whether there was any relationship to treatment with liver transplantation or the transthyretin stabilizer tafamidis.

RESULTS

The data indicate that the frequency of these abnormalities increases with increasing duration of disease. In patients broadly matched for duration of disease the frequency was higher in subjects who had undergone liver transplantation than in those who were untreated.

CONCLUSIONS

Retrospective surveys are subject to a number of potential biases. In this case, the major potential confounders were defining the time of disease onset and physician bias in choice of therapy, particularly regarding the choice of patients and the time in their course when they should undergo liver transplantation, and when and whether they should receive tafamidis. Nonetheless it appears that the incidence of severe ocular abnormalities in V30M subjects from centres around the world is similar to those found in centres in the areas endemic for this variant protein. The incidence increased with duration of disease regardless of therapy with the highest frequencies seen in patients more than ten years after diagnosis who had undergone liver transplantation.

The Extracellular Protein, Transthyretin Is an Oxidative Stress Biomarker

The extracellular protein, transthyretin is responsible for the transport of thyroxin and retinol binding protein complex to the various parts of the body. In addition to this transport function, transthyretin has also been involved in cardiovascular malfunctions, polyneuropathy, psychological disorders, obesity and diabetes, etc. Recent developments have evidenced that transthyretin has been associated with many other biological functions that are directly or indirectly associated with the oxidative stress, the common hallmark for many human diseases. In this review, we have attempted to address that transthyretin is associated with oxidative stress and could be an important biomarker. Potential future perspectives have also been discussed.

Delivery of an anti-transthyretin Nanobody to the brain through intranasal administration reveals transthyretin expression and secretion by motor neurons

Transthyretin (TTR) is a transport protein of retinol and thyroxine in serum and CSF, which is mainly secreted by liver and choroid plexus, and in smaller amounts in other cells throughout the body. The exact role of TTR and its specific expression in Central Nervous System (CNS) remains understudied. We investigated TTR expression and metabolism in CNS, through the intranasal and intracerebroventricular delivery of a specific anti-TTR Nanobody to the brain, unveiling Nanobody pharmacokinetics to the CNS. In TTR deficient mice, we observed that anti-TTR Nanobody was successfully distributed throughout all brain areas, and also reaching the spinal cord. In wild-type mice, a similar distribution pattern was observed. However, in areas known to be rich in TTR, reduced levels of Nanobody were found, suggesting potential target-mediated effects. Indeed, in wild-type mice, the anti-TTR Nanobody was specifically internalized in a receptor-mediated process, by neuronal-like cells, which were identified as motor neurons. Whereas in KO TTR mice Nanobody was internalized by all cells, for late lysosomal degradation. Moreover, we demonstrate that in vivo motor neurons also actively synthesize TTR. Finally, in vitro cultured primary motor neurons were also found to synthesize and secrete TTR into culture media. Thus, through a novel intranasal CNS distribution study with an anti-TTR Nanobody, we disclose a new cell type capable of synthesizing TTR, which might be important for the understanding of the physiological role of TTR, as well as in pathological conditions where TTR levels are altered in CSF, such as amyotrophic lateral sclerosis.

Evolution of thyroid hormone distributor proteins

Thyroid hormones (THs) are evolutionarily old hormones, having effects on metabolism in bacteria, invertebrates and vertebrates. THs bind specific distributor proteins (THDPs) to ensure their efficient distribution through the blood and cerebrospinal fluid in vertebrates. Albumin is a THDP in the blood of all studied species of vertebrates, so may be the original vertebrate THDP. However, albumin has weak affinity for THs. Transthyretin (TTR) has been identified in the blood across different lineages in adults vs juveniles. TTR has intermediate affinity for THs. Thyroxine-binding globulin has only been identified in mammals and has high affinity for THs. Of these THDPs, TTR is the only one known to be synthesised in the brain and is involved in moving THs from the blood into the cerebrospinal fluid. We analysed the rates of evolution of these three THDPs: TTR has been most highly conserved and albumin has had the highest rate of divergence.

De novo intraocular amyloid deposition after hepatic transplantation in familial amyloidotic polyneuropathy

The familiar amyloid polyneuropathy (FAP) is a rare autosomal-dominant systemic amyloidosis. Amyloid deposition occurs more frequently and extensively in the vitq. The increase in intraocular pressure (IOP) is a result of deposition of transthyretin (TTR) in trabecular meshwork. Rarely, the amyloid deposition in anterior segment can be more exuberant than in posterior segment. A 42 years old man, with FAP (Val30Met mutation), liver transplantation in 1997. He was asymptomatic, without any significant ocular abnormality until 2011. In 2011 he had an episode of pain in right eye (RE). Scalloped pupils, pupillary amyloid deposits and subtle vitreous opacities were detected. The IOP was 40 mmHg in RE and 28 mmHg in left eye (LE) with open angle. Optical coherence tomography detected a temporal superior retinal nerve fiber layer defect in LE and perimetry was normal. Topical timolol was initiated, and brimonidine was subsequently added to improve IOP control, which was achieved with topical medication until last evaluation. No progression occurred since 2011. Actually, with longer life expectancies, there is an increased risk of ocular involvement in FAP, even after liver transplantation. Although rare, a more exuberant amyloid deposition in anterior segment vs posterior segment can occur, and supports an important role of amyloid production in ciliary pigment epithelium in these patients. Medical control of IOP and a stable course are unusual in this secondary glaucoma. Ophthalmologists have an important task in the follow-up of patients and early diagnosis of risk factors for secondary glaucoma, such as scalloped pupils with amyloid deposits.

Transthyretin amyloidosis: an under-recognized neuropathy and cardiomyopathy

Transthyretin (TTR) amyloidosis (ATTR amyloidosis) is an underdiagnosed and important type of cardiomyopathy and/or polyneuropathy that requires increased awareness within the medical community. Raising awareness among clinicians about this type of neuropathy and lethal form of heart disease is critical for improving earlier diagnosis and the identification of patients for treatment. The following review summarizes current criteria used to diagnose both hereditary and wild-type ATTR (ATTRwt) amyloidosis, tools available to clinicians to improve diagnostic accuracy, available and newly developing therapeutics, as well as a brief biochemical and biophysical background of TTR amyloidogenesis.

Marked biochemical difference in amyloid proportion between intra- and extraocular tissues in a liver-transplanted patient with hereditary ATTR amyloidosis

In order to elucidate the pathomechanism of ocular amyloid formation in a liver-transplanted patient with hereditary ATTR amyloidosis, we investigated detailed biochemical features of ocular amyloid. The patient was a 49-year-old woman with V30M transthyretin (TTR) variant (p.TTRV50M), who underwent ophthalmectomy due to corneal rupture 10 years after liver transplantation (LT). The amyloid was selectively isolated from several portions in intra- and extraocular tissues using a laser microdissection (LMD) system and analyzed by liquid chromatography-tandem mass spectrometry to determine the composition percentage of wild-type and variant TTR in the isolated amyloid. Biochemical analysis revealed that the amyloid consisted mainly of variant TTR in intraocular tissues with a percentage > 80%. On the contrary in the extraocular muscles, wild-type TTR was the main component of the amyloid with a percentage of ∼70%. Our data indicate that intraocular amyloid formation strongly depends on locally synthesized variant TTR and the contribution of wild-type TTR to amyloid formation is quite limited.

Involvement of Macrophages in the Pathogenesis of Familial Amyloid Polyneuropathy and Efficacy of Human iPS Cell-Derived Macrophages in Its Treatment

We hypothesized that tissue-resident macrophages in familial amyloid polyneuropathy (FAP) patients will exhibit qualitative or quantitative abnormalities, that may accelerate transthyretin (TTR)-derived amyloid deposition. To evaluate this, we examined the number and subset of tissue-resident macrophages in heart tissue from amyloid-deposited FAP and control patients. In both FAP and control patients, tissue-resident macrophages in heart tissue were all Iba⁺/CD163⁺/CD206⁺ macrophages. However, the number of macrophages was significantly decreased in FAP patients compared with control patients. Furthermore, the proportion of intracellular TTR in CD14⁺ monocytes was reduced in peripheral blood compared with healthy donors. Based on these results, we next examined degradation and endocytosis of TTR in human induced pluripotent stem (iPS) cell-derived myeloid lineage cells (MLs), which function like macrophages. iPS-MLs express CD163 and CD206, and belong to the inhibitory macrophage category. In addition, iPS-MLs degrade both native and aggregated TTR in a cell-dependent manner in vitro. Further, iPS-MLs endocytose aggregated, and especially polymerized, TTR. These results suggest that decreased tissue-localized macrophages disrupt clearance of TTR-derived amyloid deposits, leading to progression of a pathological condition in FAP patients. To improve this situation, clinical application of pluripotent stem cell-derived MLs may be useful as an approach for FAP therapy.

Nonpenetrating deep sclerectomy as an effective treatment of glaucoma related to familial amyloid polyneuropathy

PURPOSE

To present the clinical course and treatment by nonpenetrating deep sclerectomy (NPDS) of open-angle glaucoma secondary to familial amyloid polyneuropathy (FAP).

PATIENTS AND METHODS

In a series of 10 patients with FAP in a tertiary ophthalmology center, 4 eyes of 3 patients required glaucoma filtration surgery and NPDS with implant, and local intraoperative mitomycin C application was performed. Intraocular pressure and anatomic bleb functionality were measured. We performed a retrospective review of data from medical charts of the 10 FAP patients, which included demographics, incidence and treatment of glaucoma, and previous vitrectomy.

RESULTS

NPDS resulted in normalization of intraocular pressure in all 4 eyes. Ten eyes (6 patients) of the studied group underwent vitrectomy because of amyloid opacities, 7 eyes (4 patients) had glaucoma, 6 of the eyes with glaucoma were previously vitrectomized, and 4 of them subsequently required glaucoma surgery.

CONCLUSIONS

NPDS is an effective treatment of FAP glaucoma. Previously vitrectomized eyes have a more severe course of glaucoma and more frequently require filtration surgery.

Impact of liver transplantation on the natural history of oculopathy in Portuguese patients with transthyretin (V30M) amyloidosis

PURPOSE

Evaluation of the impact of liver transplantation in the natural history of ocular disorders in familial amyloidotic polyneuropathy (FAP) amyloidosis TTR V30M related (ATTR V30M) patients.

DESIGN

A clinical, retrospective and cross-sectional study of 64 Portuguese FAP ATTR V30M patients was carried out between January 2005 and December 2011.

METHODS

Thirty-two liver transplanted patients (both eyes) aged 39.6-53.8 years old, 32/32 male/female, were paired with an equal number of non-transplanted patients, matching for age, gender, age at onset, disease duration and gender of transmitting parent. Intervention or observation procedure: Routine ophthalmological observation.

MAIN OUTCOME MEASURES

Slit-lamp observation for abnormal conjunctival vessels (ACV), tears break-up time, iris, lens; fundus observation for vitreous, retina and optic disc; Schirmer test.

RESULTS

Liver transplantation had no influence on tears break-up time, deposition of amyloid on the iris and retinal amyloid angiopathy. Slight, non-statistically significant protective effects of liver transplantation were noted in the first years for some ocular manifestations (ACV and scalloped iris), except for the abnormal Schirmer test, which was significantly more prevalent in non-transplanted patients' eyes (81% versus 56%, p = 0.002). On the other hand, deposition of amyloid on the lens, vitreous amyloidosis and glaucoma were apparently more common in transplanted patients. Those differences tended to disappear with time.

CONCLUSIONS

Ocular manifestations of FAP were not influenced by liver transplantation in a meaningful way. Both transplanted and non-transplanted FAP patients need similar regular follow-up due to long-term risk of serious ocular disease.

Ophthalmological manifestations in hereditary transthyretin (ATTR V30M) carriers: a review of 513 cases

PURPOSE

Assessment of ocular involvement in transthyretin-related familial amyloidosis with polyneuropathy (FAP) in a large cohort of Portuguese patients.

METHODS

We reviewed the medical records of 513 Portuguese FAP mutation carriers, at the Ophthalmology Service, Centro Hospitalar do Porto, between 1 January 2008 and 31 January 2013. Abnormal conjunctiva vessels (ACV), Schirmer test, tear break-up time (TBUT), amyloid deposition on the iris (DAI), scalloped iris, amyloid deposition on the anterior capsule of the lens (DAL), vitreous amyloidosis, retinal amyloid angiopathy and glaucoma were evaluated and registered.

RESULTS

Of the 513 carriers, 477 (93%) had clinical systemic disease with a median duration of 9.3 (5.1-13.7) years and 247 were men. Of these, 343 (72%) had been liver transplanted, on median of 6.6 (3.3-10.8) years before inclusion in this study. No ocular abnormalities were identified in the asymptomatic carriers (7%). The abnormalities observed with decreasing frequency were abnormal TBUT (379 patients, 79.5%, 751 eyes), abnormal Schirmer test (320 patients, 67%, 635 eyes), DAI (183 patients, 38.4%, 350 eyes), DAL (157 patients, 32.9%, 308 eyes), scalloped iris (133 patients, 27.9%, 238 eyes), glaucoma (97 patients, 20%, 165 eyes), vitreous amyloidosis (83 patients, 17.4%, 139 eyes), ACV (68 patients, 14%, 136 eyes) and amyloidotic retinal angiopathy (21 patients, 4%, 32 eyes). Patients with abnormal Schirmer test (p < 0.001), scalloped iris (p = 0.006) and vitreous amyloidosis (p = 0.007) were significantly older than the others. According to their age of onset of systemic disease, the patients have been split into early-onset (<40 years old), intermediate-onset (40-50 years old), late onset (>50 years old) and asymptomatic carriers. We observed a statistically significant difference in the prevalence of ACV (p = 0.045) and of an abnormal Schirmer test (p = 0.004) between groups. Transplanted patients have a significantly higher prevalence of DAI (p = 0.001), DAL (p = 0.009) and vitreous amyloidosis (p = 0.025) than non-transplanted patients. Of the 165 eyes with glaucoma, 92.1% had scalloped iris (p < 0.001) and of 32 eyes with retinal amyloidotic angiopathy, 68.8% had vitreous amyloidosis (p < 0.001). All prevalences increased with time of disease. The earliest ocular manifestations were abnormal Schirmer test and abnormal TBUT (12% and 17% at 5 years of clinical disease) and the least prevalent was retinal amyloid angiopathy (8% at 15 years of clinical disease).

CONCLUSION

Ocular disorders in FAP patients are common, and their prevalence increases with disease duration. Prevalence is influenced by several factors, such as the age at onset of FAP and liver transplantation.

Long-term outcomes and complications of trabeculectomy for secondary glaucoma in patients with familial amyloidotic polyneuropathy

Objective

Secondary glaucoma is a serious complication in patients with transthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP). We assessed the long-term outcomes and complications of trabeculectomy with mitomycin C (MMC) for secondary glaucoma associated with FAP.

Methods

Medical case records of Kumamoto University Hospital were retrospectively reviewed. Twenty-one eyes of 13 patients (10 with FAP ATTR Val30Met; 3 with FAP ATTR Tyr114Cys) underwent trabeculectomy with MMC and follow-up of at least 2 years. The primary outcome measure was Kaplan-Meier survival, with failure of this treatment being defined as an intraocular pressure (IOP) of ≤5 mm Hg or ≥22 mm Hg on two consecutive visits or as additional operations needed to reduce IOP. Secondary outcome measures included complications, bleb characteristics, and additional postoperative interventions required.

Results

The mean postoperative follow-up period was 5.7 years (range, 2.2–12.7 years). Kaplan-Meier analysis indicated probabilities of success of 0.76, 0.67, and 0.53 at 1, 2, and 3 years after operation, respectively. Significant complications included ocular decompression retinopathy in 7 eyes (33%) and bleb encapsulation in 10 eyes (48%). Twelve eyes (57%) needed additional surgery, such as bleb revision or trabeculectomy with MMC, to reduce IOP.

Conclusions

Trabeculectomy with MMC may not be optimal for patients with FAP-related glaucoma and may have several significant complications.

Vitreous Amyloidosis as the Presenting Symptom of Familial Amyloid Polyneuropathy TTR Val30Met in a Portuguese Patient

Familial amyloid polyneuropathy (FAP) is a group of disorders characterized by the extracellular deposition of amyloid substance in various tissues. The peripheral nervous system and the heart are the main target organs, but the eye may also be involved. We report a case of vitreous amyloidosis as the first manifestation of FAP in a 66-year-old Portuguese man without a family history.

Biomarkers in primary open angle glaucoma

Glaucoma, a leading cause of blindness worldwide, is currently defined as a disturbance of the structural or functional integrity of the optic nerve that causes characteristic atrophic changes in the optic nerve, which may lead to specific visual field defects over time. This disturbance usually can be arrested or diminished by adequate lowering of intraocular pressure (IOP). Glaucoma can be divided roughly into two main categories, ‘ open angle ’ and ‘ closed angle ’ glaucoma.Open angle, chronic glaucoma tends to progress at a slower rate and patients may not notice loss of vision until the disease has progressed significantly. Primary open angle glaucoma(POAG) is described distinctly as a multifactorial optic neuropathy that is chronic and progressive with a characteristic acquired loss of optic nerve fibers. Such loss develops in the presence of open anterior chamber angles, characteristic visual field abnormalities, and IOP that is too high for the healthy eye. It manifests by cupping and atrophy of the optic disc, in the absence of other known causes of glaucomatous disease. Several biological markers have been implicated with the disease. The purpose of this study was to summarize the current knowledge regarding the non-genetic molecular markers which have been predicted to have an association with POAG but have not yet been validated.

Novel function of transthyretin in pancreatic alpha cells

Although transthyretin (TTR) is expressed in pancreatic alpha (glucagon) cells in the islets of Langerhans, the function of TTR in pancreatic alpha cells remains unknown. In this study, by using TTR knockout (TTR KO) mice, we determined the novel role of TTR in glucose homeostasis. We demonstrated that TTR KO mice evidenced impaired recovery of blood glucose and glucagon levels. Lack of TTR induced significantly lower levels of glucagon in the islets of Langerhans. These results suggest that TTR expressed in pancreatic alpha cells may play important roles in glucose homeostasis via regulating the expression of glucagon.

Vitreous surgery impact in glaucoma development in liver transplanted familial amyloidosis ATTR V30M Portuguese patients

PURPOSE

Familial amyloidosis with polyneuropathy (FAP) sometimes courses with vitreous amyloid. The aim of this study was to evaluate the incidence of glaucoma after vitrectomy in FAP patients.

METHODS

A total of 79 eyes of 42 liver transplanted FAP patients and 16 eyes of 16 non-FAP patients with rhegmatogenous retina detachment were collected. The patients were divided in to three groups: Group I - FAP patients with vitreous opacities submitted to vitrectomy, Group II - FAP patients without vitreous opacities and not submitted to vitrectomy and, Group III - non-FAP patients with rhegmatogenous retinal detachment submitted to vitrectomy. The Group I was subdivided into: Ia - "complete" vitrectomy; Ib - "incomplete" vitrectomy. The onset of glaucoma was considered when the intraocular pressure level was higher than 21 mmHg, with concomitant visual field abnormalities and optic nerve cupping.

RESULTS

Post vitrectomy glaucoma was more frequent in Group I (56.1%) than in Group III (12.5%) and in Group II (10.5%). We observed a higher incidence of glaucoma in the Ia than in the Ib subgroup (86.4 vs. 21.1%) and earlier appearance in subgroup Ia (7.9 ± 3.6 vs. 39.5 ± 6.6 months).

CONCLUSION

Vitrectomy induced the development of glaucoma in FAP patients.

Recurrence of vitreous amyloidosis and need of surgical reintervention in Portuguese patients with familial amyloidosis ATTR V30M

PURPOSE

Vitreous amyloid deposits are one of the most common ocular manifestations of familial amyloidosis ATTR V30M (FAP-I), which can be the only manifestation of the disease and can appear even after liver transplantation. Removal by vitrectomy is usually performed, but vitreous amyloid recurrence has been frequently reported. This study was undertaken to evaluate the recurrence of vitreous amyloidosis and its relationship with the degree of previous vitreous removal.

METHODS

Fifty-four vitrectomized eyes from 32 patients with FAP-I were evaluated in the course of a follow-up period of 30.7 ± 17.2 months (range, 8-78; median = 30 months). An extensive, as possible, vitrectomy with indentation was performed in 41 eyes (complete), and in the others 13 eyes only a vitrectomy without indentation (incomplete) was performed. The parameters evaluated were the incidence of amyloid deposits and visual outcomes.

RESULTS

A noteworthy visual acuity gain was observed, although a few patients had a subsequent decrease of visual acuity related to new vitreous amyloid deposition in the visual axis. These new amyloid deposits did not occur in eyes that had undergone extensive vitreous removal, but only in nonextensive vitrectomized eyes (P < 0.001).

CONCLUSION

Recurrence of amyloid deposition only occurred in nonextensive vitrectomized eyes and represents a false recurrence associated with incomplete vitrectomy.

Anticipation of presbyopia in Portuguese familial amyloidosis ATTR V30M

The aim of this study was to evaluate if Portuguese patients with familial amyloidosis, liver transplanted and not, have an earlier development of presbyopia compared with a normal population and its relation with the presence or the absence of anterior capsule opacification of the lens. This study was performed to evaluate if Portuguese patients with familial amyloidosis and in a blood donors population (control group). Three hundred and fifty-six subjects, 144 amyloidotic patients and 212 healthy individuals, were evaluated for the need of plus lenses for normal near reading (Jaeger chart 1 at 33 cm). In familial amyloidosis patients, the value of the add-power was related to age, liver transplantation status, and presence of visible anterior capsule opacification of the lens. In both groups, the value of add-power was positively correlated with age (r=0.91; P<0.005). Familial amyloidosis patients require more add-power than control individuals of similar age, and need to use reading glasses at earlier ages. The age of onset of presbyopia in familial amyloidosis patients was significantly lower than in control individuals (32 years vs. 42 years). Adjusting for age, no significant difference was observed in add-power values between liver transplanted and not transplanted amyloidotic patients, suggesting that liver transplantation has no influence on presbyopia evolution in these patients. Familial amyloidosis patients had an earlier onset of presbyopia, probably related to amyloid deposition on the anterior capsule of the lens, which is not halted by liver transplantation.

Evolutionary changes to transthyretin: evolution of transthyretin biosynthesis

Thyroid hormones are involved in growth and development, particularly of the brain. Thus, it is imperative that these hormones get from their site of synthesis to their sites of action throughout the body and the brain. This role is fulfilled by thyroid hormone distributor proteins. Of particular interest is transthyretin, which in mammals is synthesized in the liver, choroid plexus, meninges, retinal and ciliary pigment epithelia, visceral yolk sac, placenta, pancreas and intestines, whereas the other thyroid hormone distributor proteins are synthesized only in the liver. Transthyretin is synthesized by all classes of vertebrates; however, the tissue specificity of transthyretin gene expression varies widely between classes. This review summarizes what is currently known about the evolution of transthyretin synthesis in vertebrates and presents hypotheses regarding tissue-specific synthesis of transthyretin in each vertebrate class.

Transthyretin is not expressed by dorsal root ganglia cells

Several mutations in transthyretin (TTR) are related to familial amyloidotic polyneuropathy (FAP), a neurodegenerative disorder caused by extracellular deposition of TTR fibrils, particularly in the peripheral nervous system (PNS). TTR is mainly synthesized by the liver and choroid plexus of the brain that contribute to the plasma and cerebrospinal fluid (CSF) pools of the protein, respectively. It has recently been reported that TTR is additionally expressed in the PNS, namely by peripheral glial cells of dorsal root ganglia (DRG). This lead to the hypothesis that TTR synthesis in the DRG might contribute to the PNS involvement in FAP. In this report we clarify this issue by showing that TTR synthesis is absent in both human and mouse DRG. Moreover, by using TTR KO mouse DRG as controls, we demonstrate that TTR-like immunoreactivity in the perineurium is an artifact. As such, and similarly to what has been previously shown in the central nervous system (CNS), TTR amplification by RT-PCR in the DRG most probably results from contamination by the meninges. In conclusion, TTR deposited in the PNS of FAP patients should still be regarded as having blood and/or CSF origin.