Stable Stem Research Articles

A new human mast cell line expressing a functional IgE receptor converts to tumorigenic growth by KIT D816V transfection

AbstractIn systemic mastocytosis (SM), clinical problems arise from factor-independent proliferation of mast cells (MCs) and the increased release of mediators by MCs, but no human cell line model for studying MC activation in the context of SM is available. We have created a stable stem cell factor (SCF) –dependent human MC line, ROSAKIT WT, expressing a fully functional immunoglobulin E (IgE) receptor. Transfection with KIT D816V converted ROSAKIT WT cells into an SCF-independent clone, ROSAKIT D816V, which produced a mastocytosis-like disease in NSG mice. Although several signaling pathways were activated, ROSAKIT D816V did not exhibit an increased, but did exhibit a decreased responsiveness to IgE-dependent stimuli. Moreover, NSG mice bearing ROSAKIT D816V-derived tumors did not show mediator-related symptoms, and KIT D816V-positive MCs obtained from patients with SM did not show increased IgE-dependent histamine release or CD63 upregulation. Our data show that KIT D816V is a disease-propagating oncoprotein, but it does not activate MCs to release proinflammatory mediators, which may explain why mediator-related symptoms in SM occur preferentially in the context of a coexisting allergy. ROSAKIT D816V may provide a valuable tool for studying the pathogenesis of mastocytosis and should facilitate the development of novel drugs for treating SM patients.

Breaking down pluripotency in the porcine embryo reveals both a premature and reticent stem cell state in the inner cell mass and unique expression profiles of the naive and primed stem cell states.

To date, it has been difficult to establish bona fide porcine embryonic stem cells (pESC) and stable induced pluripotent stem cells. Reasons for this remain unclear, but they may depend on inappropriate culture conditions. This study reports the most insights to date on genes expressed in the pluripotent cells of the porcine embryo, namely the inner cell mass (ICM), the trophectoderm-covered epiblast (EPI), and the embryonic disc epiblast (ED). Specifically, we reveal that the early porcine ICM represents a premature state of pluripotency due to lack of translation of key pluripotent proteins, and the late ICM enters a transient, reticent pluripotent state which lacks expression of most genes associated with pluripotency. We describe a unique expression profile of the porcine EPI, reflecting the naive stem cell state, including expression of OCT4, NANOG, CRIPTO, and SSEA-1; weak expression of NrOB1 and REX1; but very limited expression of genes in classical pathways involved in regulating pluripotency. The porcine ED, reflecting the primed stem cell state, can be characterized by the expression of OCT4, NANOG, SOX2, KLF4, cMYC, REX1, CRIPTO, and KLF2. Further cell culture experiments using inhibitors against FGF, JAK/STAT, BMP, WNT, and NODAL pathways on cell cultures derived from day 5 and 10 embryos reveal the importance of FGF, JAK/STAT, and BMP signaling in maintaining cell proliferation of pESCs in vitro. Together, this article provides new insights into the regulation of pluripotency, revealing unique stem cell states in the different porcine stem cell populations derived from the early developing embryo.

Intron retention in the 5'UTR of the novel ZIF2 transporter enhances translation to promote zinc tolerance in arabidopsis.

Root vacuolar sequestration is one of the best-conserved plant strategies to cope with heavy metal toxicity. Here we report that zinc (Zn) tolerance in Arabidopsis requires the action of a novel Major Facilitator Superfamily (MFS) transporter. We show that ZIF2 (Zinc-Induced Facilitator 2) localises primarily at the tonoplast of root cortical cells and is a functional transporter able to mediate Zn efflux when heterologously expressed in yeast. By affecting plant tissue partitioning of the metal ion, loss of ZIF2 function exacerbates plant sensitivity to excess Zn, while its overexpression enhances Zn tolerance. The ZIF2 gene is Zn-induced and an intron retention event in its 5′UTR generates two splice variants (ZIF2.1 and ZIF2.2) encoding the same protein. Importantly, high Zn favours production of the longer ZIF2.2 transcript, which compared to ZIF2.1 confers greater Zn tolerance to transgenic plants by promoting higher root Zn immobilization. We show that the retained intron in the ZIF2 5′UTR enhances translation in a Zn-responsive manner, markedly promoting ZIF2 protein expression under excess Zn. Moreover, Zn regulation of translation driven by the ZIF2.2 5′UTR depends largely on a predicted stable stem loop immediately upstream of the start codon that is lost in the ZIF2.1 5′UTR. Collectively, our findings indicate that alternative splicing controls the levels of a Zn-responsive mRNA variant of the ZIF2 transporter to enhance plant tolerance to the metal ion.

Creating stable stem regions for loop elongation in Fcabs — Insights from combining yeast surface display, in silico loop reconstruction and molecular dynamics simulations

Fcabs (Fc antigen binding) are crystallizable fragments of IgG where the C-terminal structural loops of the CH3 domain are engineered for antigen binding. For the design of libraries it is beneficial to know positions that will permit loop elongation to increase the potential interaction surface with antigen. However, the insertion of additional loop residues might impair the immunoglobulin fold. In the present work we have probed whether stabilizing mutations flanking the randomized and elongated loop region improve the quality of Fcab libraries. In detail, 13 libraries were constructed having the C-terminal part of the EF loop randomized and carrying additional residues (1, 2, 3, 5 or 10, respectively) in the absence and presence of two flanking mutations. The latter have been demonstrated to increase the thermal stability of the CH3 domain of the respective solubly expressed proteins. Assessment of the stability of the libraries expressed on the surface of yeast cells by flow cytometry demonstrated that loop elongation was considerably better tolerated in the stabilized libraries. By using in silico loop reconstruction and mimicking randomization together with MD simulations the underlying molecular dynamics were investigated. In the presence of stabilizing stem residues the backbone flexibility of the engineered EF loop as well as the fluctuation between its accessible conformations were decreased. In addition the CD loop (but not the AB loop) and most of the framework regions were rigidified. The obtained data are discussed with respect to the design of Fcabs and available data on the relation between flexibility and affinity of CDR loops in Ig-like molecules.

Refrigerated Platelets for the Treatment of Acute Bleeding

This review is a synopsis of the decisions that shaped global policy on platelet (PLT) storage temperature and a focused appraisal of the literature on which those discussions were based. We hypothesize that choices were centered on optimization of preventive PLT transfusion strategies, possibly to the detriment of the therapeutic needs of acutely bleeding patients. Refrigerated PLTs are a better hemostatic product, and they are safer in that they are less prone to bacterial contamination. They were abandoned during the 1970s because of the belief that clinically effective PLTs should both be hemostatically functional and survive in circulation for several days as indicated for prophylactic transfusion; however, clinical practice may be changing. Data from two randomized controlled trials bring into question the concept that stable autologous stem cell transplant patients with hypoproliferative thrombocytopenia should continue to receive prophylactic transfusions. At the same time, new findings regarding the efficacy of cold PLTs and their potential role in treating acute bleeding have revived the debate regarding optimal PLT storage temperature. In summary, a "one-size-fits-all" strategy for PLT storage may not be adequate, and a reexamination of whether cold-stored PLTs should be offered as a widely available therapeutic product may be indicated.

Non-nearest-neighbor dependence of stability for group III RNA single nucleotide bulge loops.

Thirty-five RNA duplexes containing single nucleotide bulge loops were optically melted and the thermodynamic parameters for each duplex determined. The bulge loops were of the group III variety, where the bulged nucleotide is either a AG/U or CU/G, leading to ambiguity to the exact position and identity of the bulge. All possible group III bulge loops with Watson-Crick nearest-neighbors were examined. The data were used to develop a model to predict the free energy of an RNA duplex containing a group III single nucleotide bulge loop. The destabilization of the duplex by the group III bulge could be modeled so that the bulge nucleotide leads to the formation of the Watson-Crick base pair rather than the wobble base pair. The destabilization of an RNA duplex caused by the insertion of a group III bulge is primarily dependent upon non-nearest-neighbor interactions and was shown to be dependent upon the stability of second least stable stem of the duplex. In-line structure probing of group III bulge loops embedded in a hairpin indicated that the bulged nucleotide is the one positioned further from the hairpin loop irrespective of whether the resulting stem formed a Watson-Crick or wobble base pair. Fourteen RNA hairpins containing group III bulge loops, either 3' or 5' of the hairpin loop, were optically melted and the thermodynamic parameters determined. The model developed to predict the influence of group III bulge loops on the stability of duplex formation was extended to predict the influence of bulge loops on hairpin stability.

Mutant BMPR2 expression in cardiomyocytes results in an altered hypertrophic response (1090.2)

Background: End‐stage pulmonary arterial hypertension (PAH) is characterized by right ventricular (RV) dysfunction, failure and death. We have shown BMPR2 mutation is associated with impaired RV hypertrophy and cardiomyocyte lipid deposition in both heritable PAH patients and a murine model of mutant BMPR2 expression.Hypothesis: BMPR2 mutation alters hypertrophic response and fatty acid transport in RV cardiomyocytes.Methods: Stable mouse embryonic stem cell lines (ESC) were engineered to express BMPR2 mutation using pCI‐Neo‐BMPR2 plasmids with mutation in either cytoplasmic (CD) or kinase domain (KD) or a linearized pCI‐Neo vector (Control) and gene expression confirmed by RT‐PCR. Directed differentiation of the ESC to cardiac myocytes (ESC CM) performed using noggin. ESC CM treated with phenylephrine for 72 hours to induce hypertrophy. Western analysis performed for proteins: CD36 (a fatty acid transporter molecule), brain natriuretic peptide (BNP) and corin (a serine peptidase which cleaves pro‐BNP). Oil‐red‐O stain performed for intracellular lipid deposition in ESC‐CM.Results: All ESC‐CM expressed α‐SMA and demonstrated characteristic contraction in vitro. In response to hypertrophy, control ESC CM increased expression of BNP and corin, which remained unchanged in CD and KD BMPR2 mutant cells.At baseline expression of CD36 protein was higher in CD BMPR2 mutant containing ESC CM and Oil‐red‐O staining suggested increased intracellular lipid accumulation in mutant ESC CM relative to control cells. Hypertrophic stimulus reduced the expression of CD36 in CD and KD BMPR2 ESC CM compared to control cells.Conclusions: Altered BMPR2 signaling due to CD or KD mutations in ESC CM were associated with an impaired hypertrophic response. This impaired response was associated with decreased expression of BNP, corin and CD36. This may explain reduced ability of RV to adapt to increased RV afterload in PAH. Further characterization of the mechanism of impaired hypertrophy is planned.Grant Funding Source: P01HL108800

P53: The barrier to cancer stem cell formation

The role of p53 as the "guardian of the genome" in differentiated somatic cells, triggering various biological processes, is well established. Recent studies in the stem cell field have highlighted a profound role of p53 in stem cell biology as well. These studies, combined with basic data obtained 20 years ago, provide insight into how p53 governs the quantity and quality of various stem cells, ensuring a sufficient repertoire of normal stem cells to enable proper development, tissue regeneration and a cancer free life. In this review we address the role of p53 in genomically stable embryonic stem cells, a unique predisposed cancer stem cell model and adult stem cells, its role in the generation of induced pluripotent stem cells, as well as its role as the barrier to cancer stem cell formation.

TLR3 regulates mycobacterial RNA-induced IL-10 production through the PI3K/AKT signaling pathway

Cytokine induction in response to Mycobacterium tuberculosis (Mtb) infection is critical for pathogen control, by (i) mediating innate immune effector functions and (ii) instructing specific adaptive immunity. IL-10 is an important anti-inflammatory cytokine involved in pathogenesis of tuberculosis (TB). Here, we show that TLR3, a sensor of extracellular viral or host RNA with stable stem structures derived from infected or damaged cells, is essential for Mtb-induced IL-10 production. Upon Mycobacterium bovis Bacillus Calmette–Guérin (BCG) infection, TLR3−/− macrophages expressed lower IL-10 but higher IL-12p40 production, accompanied by reduced phosphorylation of AKT at Ser473. BCG-infected TLR3−/− mice exhibited reduced IL-10 but elevated IL-12 expression compared to controls. Moreover, higher numbers of splenic Th1 cells and reduced pulmonary bacterial burden and tissue damage were observed in BCG-infected TLR3−/− mice. Finally, BCG RNA induced IL-10 in macrophages via TLR3-mediated activation of PI3K/AKT. Our findings demonstrate a critical role of TLR3-mediated regulation in the pathogenesis of mycobacterial infection involving mycobacterial RNA, which induces IL-10 through the PI3K/AKT signaling pathway.

Deciphering Ribosomal Frameshifting Dynamics

Ribosomes programmed by specific messenger RNA (mRNA) sequence elements can switch translation reading frames and synthesize different polypeptides from a single template. The Escherichia coli dnaX mRNA encodes two DNA polymerase III subunits, τ and γ, synthesized from 0-frame and probabilistic −1-slip across the slippery sequence: AAAAAAG. When further enhanced by structural barriers situated around the slippery sequence-an internal Shine-Dalgarno sequence and a stable hairpin stem loop, an 80% (= γ/(γ+τ)) frameshift efficiency is attained. Here, we attempt to determine the frameshift timing within one translation cycle by following a single ribosome translating a frameshift-promoting mRNA held on optical tweezers. In parallel, by mass spectrometry (MS), we survey the synthesized polypeptides to resolve where on the mRNA the ribosome has slipped.From the mass spectra of polypeptides terminated at the −1-frame stop codon, we learned that the ribosome −1-slips from more than one codon position around the slippery sequence. Some −1-frameshifted polypeptides were found to bear an extra amino acid, or to lack one, indicating that slipping sizes of −4 and +2-nt also occurred. Similarly, distinctive large-scale fluctuating translocation dynamics were seen in our real-time single-ribosome translation trajectories. This reveals that a translocating ribosome can explore a broad range of frameshift pathways. Frequently adopted frameshift pathways, i.e. the more abundant frameshifted species resolved by MS, exhibit a preference for minimizing codon:anticodon base-pair mismatches on the ribosome after a slip. Mismatch-containing ribosomes can be prematurely terminated by release factors, resulting in release of incomplete peptides. Indeed, we observed higher yields of incomplete peptides that are terminated at frameshift sites where significant mismatches were encountered. These species coincide with the prematurely stalled ribosomes recorded in the translation trajectories. Collectively what emerges from our results is a versatile ribosomal frameshifting scheme during mRNA translocation, facilitating branching of frameshift pathways.

UPF1 RNA Immunoprecipitation from Mini-μ Construct–expressing Cells

UPF1, an RNA helicase and a core factor of nonsense-mediated mRNA decay (NMD), interacts with RNA independently of the sequence context. To investigate the influence of translation on the association of UPF1 with specific reporter transcripts, UPF1 RNA immunoprecipitations (RIPs) are performed from Hela cells that either express a normally translated immunoglobulin-µ (Ig-µ) reporter (mini µ) or a version with a stable stem loop in the 5' UTR (SL mini µ) that efficiently inhibit translation initiation (Zund et al., 2013). Both the cloning of the SL mini µ reporter construct and the UPF1 RIP experiment are described in detail.

Two-Dimensional Electrophoresis-Based Selection of Aptamers Against an Unidentified Protein in a Tissue Sample

A fully automated two-dimensional electrophoresis (2DE) system was employed for DNA aptamer selection against an unidentified protein in a mouse liver tissue extract as a model target. A 2DE-based systematic evolution of ligands by exponential enrichment (2DE-SELEX) was demonstrated for aptamer selection against a single protein spot that was separated on a nitrocellulose membrane. After four iterative 2DE-SELEX cycles, the oligonucleotide pool was sequenced and aptamer sequences were identified. A blotting assay showed that an identified aptamer with a stable stem–loop structure had specific binding activity against the target protein. The 2DE-SELEX was shown to be promising for the development of aptamers against unidentified proteins in complex samples for proteomic analysis and biomarker discovery. Supplemental materials are available for this article. Go to the publisher's online edition of Analytical Letters to view the supplemental file.

Significantly Reduced Leg Length Discrepancy and Increased Femoral Offset by Application of a Head–Neck Adapter in Revision Total Hip Arthroplasty

Head–neck adapters in total hip arthroplasty (THA) promise the reconstruction of optimal femoral offset and leg length in revision THA while retaining stable implants. Radiological parameters after adapter implantation in THA revision were determined in 37 cases. Significant reduction of leg length discrepancy and improvement of femoral offset (P<0.001) were found. Clinical endpoints were determined in 20 cases (mean follow-up 4.0years). Clinical scores were rather poor (median Harris hip score 54, WOMAC score 41) due to age and comorbidities, postoperative dislocation occurred in 3 cases. Only one stable femoral stem had to be revised due to recurrent postoperative dislocation. In conclusion, a head–neck adapter can be a valuable tool in certain cases of revision THA with acceptable dislocation rates while allowing the retention of stable implants.

Dedifferentiation of committed epithelial cells into stem cells in vivo

SummaryCellular plasticity contributes to the regenerative capacity of plants, invertebrates, teleost fishes, and amphibians. In vertebrates, differentiated cells are known to revert into replicating progenitors, but these cells do not persist as stable stem cells. We now present evidence that differentiated airway epithelial cells can revert into stable and functional stem cells in vivo. Following the ablation of airway stem cells, we observed a surprising increase in the proliferation of committed secretory cells. Subsequent lineage tracing demonstrated that the luminal secretory cells had dedifferentiated into basal stem cells. Dedifferentiated cells were morphologically indistinguishable from stem cells and they functioned as well as their endogenous counterparts to repair epithelial injury. Indeed, single secretory cells clonally dedifferentiated into multipotent stem cells when they were cultured ex vivo without basal stem cells. In contrast, direct contact with a single basal stem cell was sufficient to prevent secretory cell dedifferentiation. In analogy to classical descriptions of amphibian nuclear reprogramming, the propensity of committed cells to dedifferentiate was inversely correlated to their state of maturity. This capacity of committed cells to dedifferentiate into stem cells may play a more general role in the regeneration of many tissues and in multiple disease states, notably cancer.

The Cementless Spotorno stem in THA: 10 year results

The clinical results of total hip arthroplasty (THA) with a cementless prosthesis have been constantly improving due to progress in the area of stem design and surface finish. Cementless Spotorno stem (CLS stem; Zimmer, Warsaw, USA) is a double-tapered rectangular straight stem. The purpose of this study is to investigate the mean 10 year results of CLS stem and to evaluate the press-fit stability of CLS stem. One hundred and eighty-six consecutive patients (194 hips) were evaluated at more than five years after THA using CLS stems. The mean follow-up period was 111 months. The radiographic stability of the femoral stem was determined by Engh's criteria. The ascertained period of spot welds was noted by Gruen zones on the femoral side. The presence of stress shielding, and subsidence was also evaluated. A stable stem with bony on growth was identified in all cases. The mean period of expression of spot welds was 10.8 months in zone 2, 9.9 months in zone 3, 8.5 months in zone 5, and 8.8 months in zone 6. Stress shielding of more than grade 2 was observed in only three hips, which was non-progressive at one year after surgery. Subsidence of more than 2 mm was not observed in any of the hips. Excellent stability of CLS stem has been maintained without abnormal bone reaction at the proximal femur. CLS stem is considered to achieve not only press-fit stability at trochanteric and subtrochanteric level, but bony fixation by osseointegration within one year after THA.

Hybrid Fixation Utilizing a Custom Stem Extension for the Treatment of Periprosthetic Femoral Nonunions Around Well-Fixed Cylindrical Femoral Stems

Periprosthetic femoral nonunion associated with total hip arthroplasty is an infrequent complication1. However, the increasing worldwide incidence of periprosthetic fractures2 is expected to result in a higher number of complications, including fracture nonunion. A periprosthetic fracture around a well-fixed stem (e.g., Vancouver type B1)3 is a difficult complication to manage4, and it often requires both an arthroplasty and the skills of a trauma surgeon5. Nonunited fractures are even more challenging; they have a high rate of complications and relatively poor functional outcomes1. We present two cases of periprosthetic femoral nonunion around a stable cylindrical stem. The first nonunion occurred following an intraoperative periprosthetic fracture, and the second nonunion occurred following a postoperative fracture, after which a custom stem extension had been added to the conventional fixation method. After this combination of intramedullary and extramedullary or hybrid fixation, stability was achieved at the nonunion site, and healing was obtained in both patients. To our knowledge, the use of this type of custom-made porous-coated prosthesis has not been previously reported. The patients were informed that data concerning their cases would be submitted for publication, and they provided consent. Case 1. A sixty-six-year-old woman with a history of polymyalgia rheumatica (treated with corticosteroid therapy) and left hip osteoarthritis underwent simultaneous removal of previous fixation hardware and a cementless left total hip arthroplasty. The components included a Duraloc cup and a cylindrical-type Prodigy stem (DePuy Synthes, Warsaw, Indiana). During the procedure, the patient sustained a long spiral femoral fracture extending around and distal to the stem. Because the stem was stable, the fracture was reduced and fixed with a Dall-Miles cable and plate system and multiple lag screws. Six months postoperatively, radiographs showed a well-ingrown femoral stem; however, the fracture had failed to …

Abstract 010: A Separable Upstream Promoter of the Slc8a1 (NCX1) Gene Efficiently Marks Cardiac Cell Populations Derived from Human Pluripotent Stem Cells

The sarcolemmal Na+/Ca2+ exchanger SLC8A1(NCX) regulates intracellular Ca+ in cardiomyocytes from early developmental stages. The upstream-most SLC8A1(NCX1) promoter is well conserved amongst the homoeothermic animals and contains putative binding sites for transcription factors of the NKX, GATA, STAT and CDX families. We hypothesized that functional cardiac cells with mature cardiac structural markers will express the sarcolemmal Na+/Ca2+ calcium antiporting channel, important for proper functional contractivity of in vitro differentiated human pluripotent stem cells. Pseudotyped lentiviral particles delivering NCX1cp-EGFP reporter cassette were used to confirm the efficiency and specificity of the reporter in rodent foetal cardiac cell isolates, and to establish stable human pluripotent stem cell lines. Cells were differentiated using a 2D induction protocol, and gene expression analysis and protein quantification carried at day 16. Initial NCX1cp-EGFP expression was observed from day 10-11 of cardiac differentiation. Beating foci were visualized 1-2 day after initial NCXCP-EGFP expression, reporter expression was confined to the grouped and individual beating cells, and highly correlated with the efficiency of spontaneously contractile cell production. At later stages, NCX1cp-EGFP expression correlated with clusters of formed spontaneously contractile units harbouring essentially all cardiomyocytes present in cultures, as evidenced by colocalization of high levels of cardiac troponin T (cTnT) and α-actinin proteins. The EGFP+ sorted fraction of differentiated cultures was found to be highly enriched in both early (ISL1, TBX5) and late (cTnT, MYH6) cardiomyocyte markers when compared to the EGFP- fraction. We conclude that a ~3 kb genomic fragment of the distal cardiac-specific promoter of the SLC8A1(NCX1) containing the upstream-most exon of the gene is sufficient to drive the expression of a lentiviral reporter in both rodent heart-derived primary and human (embryonic and induced) pluripotent stem cell-derived cardiac cells. Isolation of a homogenous and functional cardiomyogenic population represents one of the key objectives for cardiac tissue engineering, and in particular in vitro drug screening applications.

Stable human hematopoietic stem cell engraftment supports continuous de novo generation of mature human blood cells in mice

Stable human hematopoietic stem cell engraftment supports continuous de novo generation of mature human blood cells in mice

5′-UTR mediated translational control of splicing assembly factor RNP-4F expression during development of the Drosophila central nervous system

Drosophila RNP-4F is a highly conserved protein from yeast to human and functions as a spliceosome assembly factor during pre-mRNA splicing. Two major developmentally regulated rnp-4f mRNA isoforms have been described during fly development, designated “long” and “short,” differing by a 177-nt tract in the 5′-UTR. This region potentially folds into a single long stable stem–loop by pairing of intron 0 and part of exon 2. Since the coding potential for the two isoforms is identical, the interesting question arises as to the functional significance of this evolutionarily-conserved 5′-UTR feature. Here we describe the effects of wild-type and mutated stem–loop on modulation of rnp-4f gene expression in embryos using a GFP reporter assay. In this work, a new GFP expression vector designated pUAS-Neostinger was constructed. The UAS-GAL4 system was utilized to trigger GFP expression using tissue-specific promoter driver fly lines. Fluorescence microscopy visualization, Western blotting and real-time qRT-PÇR were used to study and quantify GFP reporter protein and mRNA levels. A significant increase in GFP reporter protein expression due to presence of the wild-type stem–loop sequence/structure was unexpectedly observed with no concomitant increase in GFP reporter mRNA levels, showing that the 177-nt region enhancement acts posttranscriptionally. The effects of potential cis-acting elements within the stem–loop were evaluated using the reporter assay in two mutant constructs. Results of GFP reporter over-expression show that RNP-4F translational regulation is highly sensitive in the developing fly central nervous system. The potential molecular mechanism behind the observed translational enhancement is discussed.

Superior outcome of strut allograft-augmented plate fixation for the treatment of periprosthetic fractures around a stable femoral stem

PurposeThis study was designed to compare the outcome of two surgical approaches for treating femoral periprosthetic fractures around a stable femoral stem. The hypothesis was that plate fixation alone might be associated with a higher complication rate due to insufficient mechanical stability. We also considered that the addition of a strut allograft would contribute to fracture healing by means of osteoconduction. MethodsWe retrospectively assessed the outcome of 21 patients who sustained periprosthetic fractures around a total hip replacement system (Vancouver type B1 and type C fractures) and who were treated in our department (January 2006 and August 2011) either by plate fixation alone or by plate fixation and a strut allograft. The mean postoperative follow-up was 23 months (range 9–69 months). Eleven patients were treated by plate fixation alone (Plate Group), and 10 patients were treated by plate fixation and a deep frozen cortical strut allograft (AG Group). Functional outcome was rated by the Harris Hip scoring system. Postoperative radiographs were assessed for evidence of fracture union. Surgical failure was defined as any complication requiring surgical revision. ResultsThe 21 patients included 17 females and 4 males. The average age was 79 years (range, 73–88) for the Plate Group and 82 years (range, 53–94) for the AG Group, and the average time to fracture union was 12 weeks (range, 2.5–6 months) and 12.95 weeks (range, 1.5–3) respectively. The overall failure rate was significantly higher in the Plate Group: 5 of them required revision surgery compared to none in the AG Group (p=0.014). ConclusionThe results of this analysis indicate that a strut allograft augmentation approach to Vancouver type B1 and type C periprosthetic fractures results in a better outcome than plate fixation alone by apparently adding mechanical stability and enhancing the biological healing process.