The Subscapularis-Sparing "Flipped Latarjet" Procedure.

The Latarjet procedure is a proven and effective operation to treat anterior shoulder instability. Especially in cases with anterior glenoid bone loss, the Latarjet operation is the most popular procedure to restore glenoid anatomy and avoid further dislocations. Next to the re-creation of the missing glenoid bone, the sling effect of the conjoint tendon transferred between a split in the subscapularis muscle is an important "soft tissue stabilizer" of the humeral head. However, it has been shown that the inferior part of the subscapularis muscle tends to degenerate, leading to fatty infiltration of the muscle itself. Also, exposure through the subscapularis split is technically demanding, and there is a risk of nerve damage due to the pulling forces of the retractors during open surgery. When performing the procedure arthroscopically, extremely low and medial portals are necessary to find a correct angle for the glenoid drilling when approaching from anterior. Neurovascular structures may be at risk during these surgical steps. The aim of the flipped Latarjet procedure is to facilitate a safe and reliable arthroscopic operation to anteriorly stabilize the shoulder by transferring the coracoid to the deficient glenoid without splitting the subscapularis muscle while keeping the benefits of a sling effect of the conjoined tendon.

Multiplanar analysis of proximal humerus anatomy of patients with rotator cuff arthropathy and relevance to reverse shoulder press-fit stems.

Background: Short stems have become increasingly popular in reverse shoulder arthroplasty (RSA) due to their ability to preserve bone stock for revision surgery. However, short stems may be more at risk for malalignment or loosening, and commercially available stems have varied designs. The purpose of this study was to perform a multiplanar analysis of proximal humerus anatomy in patients with rotator cuff arthropathy to better define canal geometry and identify differences based on sex. Methods: A retrospective review was performed of a consecutive series of patients undergoing RSA for rotator cuff arthropathy. A total of 117 patients were identified with preoperative computed tomography scans. Measurements were undertaken following multiplanar reconstruction of the computed tomography scans. Measured parameters included the following: transition point (TP), anteroposterior (AP) and mediolateral (ML) distances, intramedullary (IM) and bone diameter, and cortical thickness. The TP was defined as the distance from the periosteal border of the greater tuberosity to the level of the IM canal where the endosteal borders became parallel. Measurements started at the metaphysis, and then proceeded 25 and 50 mm distal to the metaphysis followed by 10 mm increments thereafter. Each level was compared to the level above with t tests in the overall cohort and separately by sex. Height was correlated to ML-AP difference and IM diameter with Pearson correlation coefficient. Potential stem sizes that extended 50, 60, 70, and 80 mm from the metaphysis were analyzed to record the percentage of patients in whom the stem would reach past the TP. Results: The mean TP for all patients was 55.6 ± 7.4 mm (37.5-78.4) from the greater tuberosity, 53.3 ± 6.6 mm (37.5-67.0) in females and 58.1 ± 7.5 mm (41.9-78.4) in males. ML and AP distances and IM diameter became consistent at level 3 (mean, 83 mm distal to the greater tuberosity) in the overall cohort and in both sexes. Height positively correlated with IM diameter. Males had significantly larger IM diameters compared to females at all levels. Cortical thickness remained relatively consistent throughout the proximal humerus. A stem length of 70 mm would extend past the TP in 98% of patients. Conclusion: Humeral implants in RSA with a stem of at least 70 mm in length would extend distally past the TP in the majority of cases regardless of sex. At this point, the canal's area remains consistent which would facilitate diaphyseal fixation if required.

[Revision surgery in reverse shoulder arthroplasty : Management of the most common complications]. / Revision der inversen Schulterprothese : Management der häufigsten Komplikationen.

BACKGROUND: In recent years, the number of reverse shoulder arthroplasty implantations has increased continuously and a higher number of revision surgeries due to complications can be expected in the future. Current data show a mean complication rate for RSA of around 4%. The most common complications are instability, infection, component loosening, and periprosthetic fracture. TREATMENT OPTIONS: Revision surgery for RSA is challenging, and an individual treatment plan is necessary. For prosthetic instability, different operative or non-operative treatment options are available. Revision surgery for periprosthetic infection with replacement of the prosthesis is usually necessary for infection management. The treatment of periprosthetic fractures is based on techniques of general fracture treatment and depends on the fracture type. Knowledge of complications and risk factors may decrease complication rates in primary reverse shoulder arthroplasty in the future.

Validation of the distal filling ratio in uncemented convertible short-stem shoulder arthroplasty.

INTRODUCTION: Radiographic stress shielding is a common finding in uncemented convertible short-stem shoulder arthroplasty (UCSSSA). The distal filling ratio (DFR) has been described as a predictor for the occurrence of stress shielding. A DFR > 70% was mentioned as a risk factor for the occurrence of stress shielding for some UCSSSA. However, measurements were only performed on conventional radiographs and no validation exists for 3D automated planning tools. METHODS: DFR was manually measured on postoperative true ap radiographs of 76 shoulder arthroplasties using a standardized protocol and were compared to preoperative CT scans with an automated calculation of the DFR after virtual implantation of the stem. RESULTS: The mean DFR measured on X-rays was 75.9% (SD = 8.7; 95% CI = 74-78) vs. 78.9% (SD = 9.1; 95% CI = 76.8-83) automatically measured on CT scans. This difference was significant (p < 0.001). In 7 out of 76 cases (9%) the difference between manual measurement on radiographs and computerized measurement on CT scans was > 10%. CONCLUSION: Manual measurement of the DFR is underestimated on conventional radiographs compared to automated calculation on CT scans be a mean of 3%. Therefore, automated measurement of the DFR on CT scans seems to be beneficial, especially in cases with osteopenic cortices. Manual measurement of the DFR on conventional ap radiographs in cases without CT scans, however, is still a viable alternative. LEVEL OF EVIDENCE: Level IV, retrospective study.

Stem size prediction in shoulder arthroplasty with preoperative 3D planning.

INTRODUCTION: Three-dimensional surgical planning software provides virtual reconstructions of the shoulder with automated joint indices for a preoperative case assessment. The aim of this single center study was to evaluate the concordance between the preoperatively selected humeral components and the final implants used in shoulder arthroplasty. METHODS: 129 cases who had undergone anatomic (n = 16) or reverse shoulder arthroplasty (n = 117) using the same type of uncemented short stem implant and were included for review in this study. The type of arthroplasty, stem size, stem inclination, tray-offset and liner-thickness were noted preoperatively and compared to the final implant specifications used in surgery. RESULTS: The type of arthroplasty matched the surgical plan in 99.2% of cases, as one case was converted from RSA to TSA. The concordance of planned to implanted stem size was 44.2% and the planned size was in range of one adjacent size in 87.6% of cases. Stem inclination in TSA matched the surgical plan in 50% of cases. Tray offset in RSA was predicted correctly in 65% and liner-thickness matched the surgical plan in 98.3% of cases. CONCLUSION: Despite a low degree of concordance of planned to implanted stem sizes of 44.2%, the choice of stem size was found to be in range of one adjacent size in 87.6% of cases. Further investigations of other contributing factors are necessary to increase the accuracy of the preoperative selection of humeral implants. LEVEL OF EVIDENCE: level IV, retrospective case study.

Short stem humeral components in reverse shoulder arthroplasty: stem alignment influences the neck-shaft angle.

INTRODUCTION: Shorter humeral reverse total shoulder arthroplasty (RTSA) stems may reduce stress shielding, however, potentially carry the risk of varus/valgus malalignment. This radiographic study's purpose was to measure the incidence of stem malalignment and thus the realized neck-shaft angle (NSA). The hypothesis was that malalignment of the stem is a frequent postoperative radiographic finding. METHODS: Radiographs of an uncemented curved short stem RTSA with a 145° NSA were reviewed. The study group included 124 cases at a mean age of 74 (range 48-91) years. The humeral stem axis was measured and defined as neutral if the value fell within ± 5° of the longitudinal humeral axis. Angular values > 5° were defined as malaligned in valgus or varus. The filling ratio of the implant within the humeral shaft was measured at the level of the metaphysis (FRmet) and diaphysis (FRdia). RESULTS: The average humeral stem axis angle was 4 ± 3° valgus, corresponding to a true mean NSA of 149 ± 3°. Stem axis was neutral in 73% (n = 90) of implants. Of the 34 malaligned implants, 82% (n = 28) were in valgus (NSA = 153 ± 2°) and 18% (n = 6) in varus (NSA = 139 ± 1°). The average FRmet and FRdia were 0.68 ± 0.11 and 0.72 ± 0.11, respectively. A low positive association was found between stem diameter and filling ratios (r = 0.39; p < 0.001); indicating smaller stem sizes were more likely to be misaligned. CONCLUSION: Uncemented short stem implants may decrease stress shielding; however, approximately one quarter were implanted > 5° malaligned. The majority of malaligned components (86%) were implanted in valgus, corresponding to an NSA of > 150°. As such, surgeons must be aware that shorter and smaller stems may lead to axial malalignment influencing the true SA. LEVEL OF EVIDENCE: Level IV, retrospective study.

Subsidence of Uncemented Short Stems in Reverse Shoulder Arthroplasty-A Multicenter Study.

BACKGROUND: The radiological phenomenon of subsidence following the implantation of uncemented short-stem reverse prostheses (USSP) has not yet been described. The purpose of this study was to describe the rate and potential risk factors for subsidence. We hypothesized that subsidence may be a frequent finding and that a subsidence of >5 mm (mm) is associated with an inferior clinical outcome. METHODS: A total of 139 patients with an average age of 73 ± 9 years were included. The clinical and radiological outcome was evaluated at a minimum follow-up (FU) of 12 months. RESULTS: No humeral component loosening was present at a mean FU of 18 (range, 12-51) months. Mean Constant Score (CS) and Subjective Shoulder Value (SSV) improved significantly from 34.3 ± 18.0 points and 37.0 ± 19.5% preoperatively to 72.2 ± 13.4 points and 80.3 ± 16.5% at final FU (p < 0.001). The average subsidence of the USSP was 1.4 ± 3.7 mm. Subsidence of >5 mm was present in 15 patients (11%). No association between a subsidence >5 mm and CS or SSV was found (p = 0.456, p = 0.527). However, a subsidence of >5 mm resulted in lower strength at final FU (p = 0.022). Complications occurred in six cases (4.2%), and the revision rate was 3.5% (five cases). CONCLUSIONS: Although subsidence of USSP is a frequent radiographic finding it is not associated with loosening of the component or a decrease in the clinical outcome at short term FU. LEVEL OF EVIDENCE: Level 4, retrospective study.

Is preoperative planning effective for intraoperative glenoid implant size and type selection during anatomic and reverse shoulder arthroplasty?

INTRODUCTION: Preoperative 3D planning programs for anatomic (TSA) and reverse total shoulder arthroplasty (RSA) allow the analysis of glenohumeral joint pathoanatomy and templating for implant size selection and placement. The aim of this multicenter study was to compare the preoperative glenoid implant type and size planned to the final glenoid implant type and size used intraoperatively. METHODS: Two hundred patients (100 TSA and 100 RSA) with a mean age of 72 years who had undergone preoperative planning and subsequent shoulder arthroplasty (100 TSA and 100 RSA) were included. All preoperative plans were saved and were analyzed for arthroplasty type (TSA vs. RSA), implant type (augment vs. nonaugment), and size (ie, polyethylene size, polyethylene radius of curvature, glenoid baseplate diameter, baseplate post length, and baseplate lateralization). The preoperative plan was available during surgery and was compared to the final implants inserted by the surgeon. RESULTS: There were no intraoperative conversions of TSA to RSA or vice versa. In patients planned for a TSA, complete concordance between the preoperative plan and final implant selection was 85%. A complete mismatch for TSA glenoid size, backside radius of curvature, and augmentation occurred in 2%. For RSA, complete concordance was found in 90% of cases. A complete mismatch for implant type, size, post length, and glenosphere size occurred in 3%. CONCLUSION: A high concordance was found between preoperative 3D planning implant selection and the glenoid component inserted at surgery for TSA and RSA. This high concordance may assist with surgical preparedness, implant stocks, and possibly future implant production.

Postoperative radiographic findings of an uncemented convertible short stem for anatomic and reverse shoulder arthroplasty.

BACKGROUND: Several short-stemmed press-fit humeral components have been developed in recent years for anatomic total shoulder arthroplasty (TSA) as well as reverse shoulder arthroplasty (RSA). Varying radiographic outcomes have been reported, with some studies reporting concerning rates of aseptic loosening. This study analyzed the radiographic findings of a press-fit convertible short-stemmed humeral component in both TSA and RSA. METHODS: There were 150 anatomic TSAs (group 1) and 77 RSAs (group 2) analyzed radiographically at a minimum follow-up of 2 years postoperatively. Plain radiographs were reviewed for stem loosening, alignment, signs of stress shielding, and the filling ratio. RESULTS: At final follow-up, 49% of group 1 and 65% of group 2 had no evidence for radiographic changes. In those with radiographic changes, low bone adaptions were found in 83% and high adaptions in 17% in both groups. Larger stem sizes with higher filling ratios were associated with high radiographic adaptions in both groups (P = .02). The overall filling ratios were higher in group 2 (P = .002). Cortical contact of the stem led to higher bone adaptions (P = .014). CONCLUSIONS: The short humeral component analyzed in this study showed encouraging survival rates without aseptic loosening. Radiographic changes are associated with a higher filling ratio and cortical contact of the stem. Surgeons should aim to achieve fixation with the minimal required canal filling to minimize radiographic changes with the uncemented humeral component used in this study.

Short-term results of a second generation anatomic short-stem shoulder prosthesis in primary osteoarthritis.

INTRODUCTION: The aim of the study was to evaluate the short-term clinical results of anatomic total shoulder arthroplasty with a short-stem prosthesis in primary osteoarthritis. MATERIALS AND METHODS: 65 shoulders with a mean age of 70 years (range 47-85 years) were available for minimum follow-up of 24 months. Clinical outcome was determined by range of motion, Constant score (CS) age and sex-adjusted Constant score (CS%), and subjective shoulder value (SSV). The influence of six different factors (high bone adaptations, age > 65 years, female gender, dominant side, atrophy of the supraspinatus tendon ≥ grade 2, glenoid type B2/B3) on the clinical outcome was assessed. RESULTS: At mean follow-up of 37 months (range 24-58 months), the CS improved from 36 ± 8 to 75 ± 12 (p < 0.001). The shoulder flexion (100° ± 21° to 159° ± 19°) as well as the external rotation (3° ± 11° to 43° ± 18°) improved significantly (p < 0.001). Three complications were noted (transient neuropraxia of the radial nerve, subjective instability, hematoma with superficial wound infection) leading to one revision surgery (wound debridement). No stem loosening was observed. High bone adaptation was present in 19 out of 65 shoulders (29%). The clinical outcome was not influenced by high bone adaptations (p ≥ 0.095). Age > 65 years (n = 44) and female gender (n = 38) were associated with worse clinical outcome (p ≤ 0.043). CONCLUSIONS: In the short term, the clinical results of this anatomical short-stem shoulder prosthesis are encouraging. A low prevalence of high bone adaptations was found without any influence on the clinical outcome and stem loosening was not observed.

Exploring Local Disorder within CAU-1 Frameworks Using Hyperpolarized 129Xe NMR Spectroscopy.

The sorption properties of metal-organic frameworks (MOFs) can be influenced by introducing covalently attached functional side chains, which make this subclass of porous materials promising for applications as diverse as gas storage and separation, catalysis, and drug delivery. The incorporation of side groups usually comes along with disorder, as the synthesis procedures rarely allow for one specific position among a larger group of equivalent sites to be selected. For a series of isoreticular CAU-1 frameworks, chosen as model compounds, one out of four positions at every linker is modified with equal probability. Here, we investigate the influence of this disorder on Ar sorption and 129Xe nuclear magnetic resonance spectroscopy using hyperpolarized 129Xe gas. Models used for predicting the pore dimensions as well as their distributions were derived from the unfunctionalized framework by replacing one proton at every linker with either an amino, an acetamide, or a methyl urea functionality. The resulting structures were optimized using density functional theory (DFT) calculations. Results from void analyses and Monte Carlo force field simulations suggest that for available Ar nonlocal DFT (NLDFT) kernels, neither the pore dimensions nor the distributions induced by the side-chain disorder are well-reproduced. By contrast, we found the 129Xe chemical shift analysis for the shift observed at high temperature to be well-suited to develop a detailed fingerprint of the porosity and side-chain disorder within the isoreticular CAU-1 series. After calibrating the 129Xe limiting shift of the amino-functionalized framework with DFT calculations, the downfield shifts for the other two derivatives are an excellent measure for the reduction of the accessible pore space and reveal a strong preference for the side chains toward the octahedral voids for both cases. We expect that the strategy presented here can be commonly applied to disorder phenomena within MOFs in the future.

ABCA3 missense mutations causing surfactant dysfunction disorders have distinct cellular phenotypes.

Mutations in the ATP-binding cassette subfamily A member 3 (ABCA3) gene are the most common monogenetic cause of surfactant dysfunction disorders in newborns and interstitial lung diseases in children and young adults. Although the effect of mutations resulting in truncated or incomplete proteins can be predicted, the consequences of missense variants cannot be as easily. Our aim was to investigate the intracellular handling and disturbance of the cellular surfactant system in a stable cell model with several different clinically relevant ABCA3 missense mutations. We found that the investigated missense mutations within the ABCA3 gene affect surfactant homeostasis in different ways: first by disrupting intracellular ABCA3 protein localization (c.643C > A, p.Q215K; c.2279T > G, p.M760R), second by impairing the lipid transport of ABCA3 protein (c.875A > T, p.E292V; c.4164G > C, p.K1388N), and third by yet undetermined mechanisms predisposing for the development of interstitial lung diseases despite correct localization and normal lipid transport of the variant ABCA3 protein (c.622C > T, p.R208W; c.863G > A, p.R288K; c.2891G > A, p.G964D). In conclusion, we classified cellular consequences of missense ABCA3 sequence variations leading to pulmonary disease of variable severity. The corresponding molecular pathomechanisms of such ABCA3 variants may specifically be addressed by targeted treatments.

Probing Interactions of N-Donor Molecules with Open Metal Sites within Paramagnetic Cr-MIL-101: A Solid-State NMR Spectroscopic and Density Functional Theory Study.

Understanding host-guest interactions is one of the key requirements for adjusting properties in metal-organic frameworks (MOFs). In particular, systems with coordinatively unsaturated Lewis acidic metal sites feature highly selective adsorption processes. This is attributed to strong interactions with Lewis basic guest molecules. Here we show that a combination of 13C MAS NMR spectroscopy with state-of-the-art density functional theory (DFT) calculations allows one to unravel the interactions of water, 2-aminopyridine, 3-aminopyridine, and diethylamine with the open metal sites in Cr-MIL-101. The 13C MAS NMR spectra, obtained with ultrafast magic-angle spinning, are well resolved, with resonances distributed over 1000 ppm. They present a clear signature for each guest at the open metal sites. Based on competition experiments this leads to the following binding preference: water < diethylamine ≈ 2-aminopyridine < 3-aminopyridine. Assignments were done by exploiting distance sum relations derived from spin-lattice relaxation data and 13C{1H} REDOR spectral editing. The experimental data were used to validate NMR shifts computed for the Cr-MIL-101 derivatives, which contain Cr3O clusters with magnetically coupled metal centers. While both approaches provide an unequivocal assignment and the arrangement of the guests at the open metal sites, the NMR data offer additional information about the guest and framework dynamics. We expect that our strategy has the potential for probing the binding situation of adsorbate mixtures at the open metal sites of MOFs in general and thus accesses the microscopic interaction mechanisms for this important material class, which is essential for deriving structure-property relationships.

Functional rescue of misfolding ABCA3 mutations by small molecular correctors.

Adenosine triphosphate (ATP)-binding cassette subfamily A member 3 (ABCA3), a phospholipid transporter in lung lamellar bodies (LBs), is essential for the assembly of pulmonary surfactant and LB biogenesis. Mutations in the ABCA3 gene are an important genetic cause for respiratory distress syndrome in neonates and interstitial lung disease in children and adults, for which there is currently no cure. The aim of this study was to prove that disease causing misfolding ABCA3 mutations can be corrected in vitro and to investigate available options for correction. We stably expressed hemagglutinin (HA)-tagged wild-type ABCA3 or variants p.Q215K, p.M760R, p.A1046E, p.K1388N or p.G1421R in A549 cells and assessed correction by quantitation of ABCA3 processing products, their intracellular localization, resembling LB morphological integrity and analysis of functional transport activity. We showed that all mutant proteins except for M760R ABCA3 were rescued by the bithiazole correctors C13 and C17. These variants were also corrected by the chemical chaperone trimethylamine N-oxide and by low temperature. The identification of lead molecules C13 and C17 is an important step toward pharmacotherapy of ABCA3 misfolding-induced lung disease.

Short-term radiographic results of a cemented polyethylene keeled glenoid component with varying backside radiuses of curvature.

BACKGROUND: This study analyzed the radiographic results of a cemented all-polyethylene keeled glenoid component available in different sizes and multiple backside radiuses of curvature. METHODS: The study group consisted of 118 cases (114 patients). There were 63 women and 51 men. Mean age at the time of arthroplasty was 68 years (range, 51-85 years). True anterior-posterior radiographs obtained postoperatively and at the final follow-up were analyzed for implant seating and the occurrence of radiolucent lines. Glenoid morphology and fatty infiltration of the rotator cuff muscles were examined using computed tomography scans. Mean follow-up was 38 months (range, 24-70 months). RESULTS: The mean radiolucent line score after surgery was 0.54 points (range, 0-3 points), and 90% had no or only 1 radiolucent line. At the final follow-up, the mean score was 1.06 points (range, 0-3 points), and 74% had no or only 1 radiolucent line. The score increased significantly over time (P < .001). No component was at risk for loosening. No correlation was found between patient age, sex, hand dominance, glenoid morphology, or fatty infiltration of the rotator cuff muscles and the occurrence of radiolucent lines. CONCLUSION: In the short-term, the glenoid component analyzed in this study showed promising radiographic results, with a low number of radiolucent lines without failure. However, the mean radiolucent line score increased significantly over time, and long-term observations are necessary to confirm a possible advantage compared with older component designs.

Quantification of volume and lipid filling of intracellular vesicles carrying the ABCA3 transporter.

The ABCA3 lipid transporter is located in the limiting membrane of lamellar bodies (LBs) in type-II-pneumocytes. Mutations within the ABCA3 gene may functionally impair the transporter, causing lung diseases in newborns, children and adults. Assays to quantify volume and lipid filling of the LBs on the level of the vesicular structures and thereby assess the function of ABCA3 are still lacking. In the present study human influenza haemagglutinin- (HA-) tagged wild type and mutant ABCA3 proteins were stably expressed in lung A549 cells. Fluorescently-labelled TopFluor phosphatidylcholine (TopF-PC) incorporated in surfactant-like liposomes was delivered to the cells and visualized by confocal microscopy. Subsequently, a comprehensive image analysis method was applied to quantify volume and fluorescence intensity of TopF-PC in ABCA3-HA-positive vesicles. TopF-PC accumulated within the vesicles in a time and concentration-dependent manner, whereas the volume remained unchanged, suggesting active transport into preformed ABCA3 containing vesicles. Furthermore, this finding was supported by a decrease of the fluorescence intensity within the vesicles when either the ATPase of the transporter was inhibited by vanadate, or when a disease-causing mutation (K1388N) close to the ABCA3-nucleotide binding domain 2 was introduced. Conversely, a mutation (E292V) located in the first cytoplasmic loop of ABCA3 did not significantly affect lipid transport, but rather resulted in smaller vesicles. In addition to these findings, the assay used in this work for analysing the PC-lipid transport into ABCA3 positive vesicles will be useful to screen for compounds susceptible to restore function in mutated ABCA3 protein.

Lung disease caused by ABCA3 mutations.

BACKGROUND: Knowledge about the clinical spectrum of lung disease caused by variations in the ATP binding cassette subfamily A member 3 (ABCA3) gene is limited. Here we describe genotype-phenotype correlations in a European cohort. METHODS: We retrospectively analysed baseline and outcome characteristics of 40 patients with two disease-causing ABCA3 mutations collected between 2001 and 2015. RESULTS: Of 22 homozygous (15 male) and 18 compound heterozygous patients (3 male), 37 presented with neonatal respiratory distress syndrome as term babies. At follow-up, two major phenotypes are documented: patients with (1) early lethal mutations subdivided into (1a) dying within the first 6 months or (1b) before the age of 5 years, and (2) patients with prolonged survival into childhood, adolescence or adulthood. Patients with null/null mutations predicting complete ABCA3 deficiency died within the 1st weeks to months of life, while those with null/other or other/other mutations had a more variable presentation and outcome. Treatment with exogenous surfactant, systemic steroids, hydroxychloroquine and whole lung lavages had apparent but many times transient effects in individual subjects. CONCLUSIONS: Overall long-term (>5 years) survival of subjects with two disease-causing ABCA3 mutations was <20%. Response to therapies needs to be ascertained in randomised controlled trials.

Matricellular protein SPARCL1 regulates tumor microenvironment-dependent endothelial cell heterogeneity in colorectal carcinoma.

Different tumor microenvironments (TMEs) induce stromal cell plasticity that affects tumorigenesis. The impact of TME-dependent heterogeneity of tumor endothelial cells (TECs) on tumorigenesis is unclear. Here, we isolated pure TECs from human colorectal carcinomas (CRCs) that exhibited TMEs with either improved (Th1-TME CRCs) or worse clinical prognosis (control-TME CRCs). Transcriptome analyses identified markedly different gene clusters that reflected the tumorigenic and angiogenic activities of the respective TMEs. The gene encoding the matricellular protein SPARCL1 was most strongly upregulated in Th1-TME TECs. It was also highly expressed in ECs in healthy colon tissues and Th1-TME CRCs but low in control-TME CRCs. In vitro, SPARCL1 expression was induced in confluent, quiescent ECs and functionally contributed to EC quiescence by inhibiting proliferation, migration, and sprouting, whereas siRNA-mediated knockdown increased sprouting. In human CRC tissues and mouse models, vessels with SPARCL1 expression were larger and more densely covered by mural cells. SPARCL1 secretion from quiescent ECs inhibited mural cell migration, which likely led to stabilized mural cell coverage of mature vessels. Together, these findings demonstrate TME-dependent intertumoral TEC heterogeneity in CRC. They further indicate that TEC heterogeneity is regulated by SPARCL1, which promotes the cell quiescence and vessel homeostasis contributing to the favorable prognoses associated with Th1-TME CRCs.

Homooligomerization of ABCA3 and its functional significance.

ABCA3 is a surfactant lipid transporter in the limiting membrane of lamellar bodies in alveolar type II cells. Mutations in the ATP-binding cassette, sub-family A (ABC1), member 3 (ABCA3) gene cause respiratory distress syndrome in newborns, and chronic interstitial lung disease in children and adults. ABCA3 belongs to the class of full ABC transporters, which are supposed to be functional in their monomeric forms. Although other family members e.g., ABCA1 and ABCC7 have been shown to function as oligomers, the oligomerization state of ABCA3 is unknown. In the present study, the oligomerization of ABCA3 was investigated in cell lysates and crude membrane preparations from transiently and stably transfected 293 cells using blue native PAGE (BN-PAGE), gel filtration and co-immunoprecipitation. Additionally, homooligomerization was examined in vivo in cells using bioluminescence resonance energy transfer (BRET). Using BN-PAGE and gel filtration, we demonstrate that non-denatured ABCA3 exists in different oligomeric forms, with monomers (45%) and tetramers (30%) being the most abundant forms. Furthermore, we also show the existence of 20% dimers and 5% trimers. BRET analyses verified intermolecular interactions in vivo. Our results also demonstrated that the arrest of ABCA3 in the endoplasmic reticulum (ER), either through drug treatment or induced by mutations in ABCA3, inhibited the propensity of the protein to form dimers. Based on our results, we suggest that transporter oligomerization is crucial for ABCA3 function and that a disruption of oligomerization due to mutations represents a novel pathomechanism in ABCA3-associated lung disease.

Tools to explore ABCA3 mutations causing interstitial lung disease.

BACKGROUND: Interstitial lung diseases (ILD) comprise disorders of mostly unknown cause. Among the few molecularly defined entities, mutations in the gene encoding the ATP-binding cassette (ABC), subfamily A, member 3 (ABCA3) lipid transporter represent the main cause of inherited surfactant dysfunction disorders, a subgroup of ILD. Whereas many cases are reported, specific methods to functionally define such mutations are rarely presented. MATERIALS AND METHODS: In this study, we exemplarily utilized a set of molecular tools to characterize the mutation K1388N, which had been identified in a patient suffering from ILD with lethal outcome. We also aimed to correlate in vitro and ex vivo findings. RESULTS: We found that presence of the K1388N mutation did not affect protein expression, but resulted in an altered protein processing and a functional impairment of ABCA3. This was demonstrated by decreased dipalmitoyl-phosphatidylcholine (PC 32:0) content and malformed lamellar bodies in cells transfected with the K1388N variant as compared to controls. CONCLUSIONS: Here we present a set of tools useful for categorizing different ABCA3 mutations according to their impact upon ABCA3 activity. Knowledge of the molecular defects and close correlation of in vitro and ex vivo data will allow us to define groups of mutations that can be targeted by small molecule correctors for restoring impaired ABCA3 transporter in the future. Pediatr Pulmonol. 2016;51:1284-1294. © 2016 Wiley Periodicals, Inc.