Interference screw versus suture button fixation for tibialis anterior tendon transfer: a biomechanical analysis

Tibialis anterior tendon (TAT) transfer to the lateral cuneiform is commonly utilized to treat dynamic supination for relapsed clubfoot deformity. Traditional suture button fixation (SBF) may lead to skin necrosis at the button/skin interface. While interference screw fixation (ISF) would mitigate this concern, this fixation method has not been investigated in clubfoot patients. This study aims to investigate the performance of ISF versus SBF for TAT transfer in a cadaveric model. Ten matched pairs of cadaveric feet were obtained. One of each matched specimen underwent TAT transfer to the lateral cuneiform using ISF and the other underwent TAT transfer using SBF. For each ISF specimen, the tension of the transferred TAT required to bring the ankle to neutral was measured. This tension was then applied to both matched specimens using an MTS machine. Tension dissipation was measured after a 20-minute interval. In specimens with SBF, a load cell was positioned between the plantar skin and suture button to determine plantar skin pressure at the time of initial tension application. Average tension necessary to achieve neutral dorsiflexion was 49.4 N. Average tension dissipation after 20 min was significantly less in the IFS group (20 N versus 23.6 N, P = 0.02). No fixation failures occurred in either group. Average plantar foot skin pressure was 196.5 mmHg at initial tension application, exceeding thresholds for tissue ischemia. ISF allows for tendon tensioning at forces beyond those expected to result in skin necrosis with SBF with less dissipation of tension over time.

Comparison of waterproof versus cotton cast liners on cast index in pediatric forearm fractures

Achieving an adequate cast mold is critical for successful nonoperative management of pediatric forearm fractures. A high cast index (>0.8) is as- sociated with an increased risk of loss of reduction and failure of conservative management. Waterproof cast liners offer improved patient satisfaction compared to conventional cotton liners, however they may carry different mechanical properties compared to traditional cotton liners. The purpose of this study was to determine whether the cast index differs between waterproof and traditional cotton cast liners when used to stabilize pediatric forearm fractures. We retrospectively reviewed all forearm fractures casted in a pediatric orthopedic surgeon's clinic between December 2009 and January 2017. Either a waterproof or cotton cast liner was utilized according to parent and patient preferences. The cast index was determined on follow-up radiographs and compared between groups. Overall, 127 fractures met the criteria for this study. Twenty-five fractures had waterproof liners and 102 fractures had cotton liners placed. Waterproof liner casts showed a significantly higher cast index (0.832 vs 0.777; p=0.001), with a significantly higher proportion of casts with index greater than 0.8 (64.0% vs 35.3%; p=0.009). The use of waterproof cast liners is associated with a higher cast index compared to traditional cotton cast liners. Although waterproof liners may be associated with higher patient satisfaction scores, providers should be aware of this difference in mechanical properties and may consider altering their casting technique accordingly.

Total Ankle Arthroplasty Is Safer than Total Hip and Knee Arthroplasty

Category:

Ankle Arthritis

Introduction/Purpose:

Total hip and knee arthroplasty (THA and TKA) are performed far more commonly than total ankle arthroplasty (TAA), so patients and the orthopaedic community have a better understanding of the complication profile for THA and TKA than for TAA. The present study compares adverse event rates, the rate of blood transfusion, operative times, length of stay, and the rate of hospital readmission between TAA, THA, and TKA procedures.

Methods:

Patients were identified who underwent TAA, THA, or TKA during 2006-2016 as part of the American College of Surgeons National Surgical Quality Improvement Program (NSQIP). Multivariate regression was used to compare TAA to THA and TKA in terms of adverse event rates, the rate of blood transfusion, operative times, length of stay, and the rate of hospital readmission. All analyses were fully adjusted for differences in baseline demographic, comorbidity, and procedural characteristics, including type of anesthesia. The level of significance was set at p<0.05.

Results:

A total of 138,325 patients were identified as having undergone THA, 223,587 TKA, and 839 TAA. The total complication rate was lower for TAA (2.98%) compared to THA (4.92%, p=0.011) and TKA (4.56%, p=0.049; Table 1). Similarly, the rate of blood transfusion was lower for TAA (0.48%) compared to THA (9.66%, p<0.001) and TKA (6.44%, p<0.001). Interestingly, operative time was approximately an hour longer for TAA (157.7 minutes) compared to THA (93.6 minutes, p<0.001) and TKA (93.7 minutes, p<0.001). Length of stay was approximately one day shorter for TAA (1.9 days) compared to THA (2.9 days, p<0.001) and TKA (3.0 days, p<0.001). Finally, the rate of readmission was lower for TAA (1.5%) compared to THA (3.7%, p=0.002) and TKA (3.4%, p=0.005).

Conclusion:

TAA is a relatively rare procedure to which patients may not have had much exposure. Patients considering TAA are more likely to have had exposure to more common procedures such as THA and TKA (through family, friends, their own procedures, etc.). Patients can be counseled that relative to THA and TKA, TAA is a safer procedure in the perioperative time frame, with significantly lower rates of adverse events, blood transfusion, additional surgery, and hospital readmission. Their procedures can be expected to take longer, but their hospital stays can be expected to be shorter.

Quality of Modern Total Ankle Arthroplasty Research

Category:

Ankle Arthritis

Introduction/Purpose:

Total ankle arthroplasty (TAA) is gaining popularity as an alternative to ankle arthrodesis in the setting of end-stage ankle arthritis. However, compared to hip and knee arthroplasty, there is a relative dearth of evidence to support its use. This study assesses the quality of literature surrounding modern TAA designs.

Methods:

A search of all peer-reviewed, English-language journals was conducted to identify publications involving TAA. The initial search identified 444 articles published during 2006-2016. Of these, 182 were excluded because they were not clinical outcomes studies, 46 because the TAA implant was no longer available, and 15 because the primary outcome of the study was not related to TAA, leaving 201 articles for analysis.

Results:

No Level I studies were identified. Seventeen (8%) studies were Level II, 48 (24%) Level III, 128 (64%) Level IV, and 8 (4%) Level V. One hundred forty-three studies (71%) were retrospective in nature. Stratification by study design revealed 128 (64%) case series, 33 (16%) experimental cohort studies, 19 (10%) case-control studies, 13 (6%) observational cohort studies, and 8 (4%) case reports. The number of studies published each year steadily increased from 2006 to 2016. A total of 51% of TAA research was published in only two journals: Foot and Ankle International and the Journal of Bone and Joint Surgery. Publications from the United States accounted for 36% of total publications. The most published implant was the Scandinavian Total Ankle Replacement (Figure 1).

Conclusion:

While the number of TAA studies published each year has steadily increased since 2006, the quality of this research as measured by level of evidence remains suboptimal. This analysis highlights the need for continued improvement in methodology and development of robust prospective registries to advance our knowledge of TAA as a treatment for end-stage ankle arthritis.

Timing of Adverse Events Following Open Reduction and Internal Fixation of the Ankle

Category:

Ankle

Introduction/Purpose:

There is increasing interest in the early identification and treatment of adverse medical events following orthopaedic procedures. The purpose of this study is to characterize the timing of adverse events following open reduction and internal fixation of closed fractures of the ankle.

Methods:

A retrospective cohort study was conducted using the American College of Surgeons National Surgical Quality Improvement Program. A total of 17,318 patients undergoing open reduction and internal fixation of closed ankle fractures were identified. For each of eight different adverse events, the median postoperative day of diagnosis, interquartile range for day of diagnosis, and middle 80% for day of diagnosis were determined. Timing was compared between uni-malleolar and bi-/tri-malleolar fractures.

Results:

The median day of diagnosis (and interquartile range; middle 80%) for myocardial infarction was 2 (1-5; 0-17), pneumonia 3 (2-7; 1-19), acute kidney injury 6.5 (2-18; 2-20), urinary tract infection 7 (2-14; 0-24), pulmonary embolism 10 (3-21; 0-27), sepsis 15 (4-22; 1-28), deep vein thrombosis 17 (10-22; 3-27), and surgical site infection 19 (14-25; 8-28; Figure 1). Myocardial infarction occured earlier in patients with bi-/tri-malleolar fractures than in patients with uni-malleolar fractures (median postoperative day 2 versus 10, p=0.041). Similarly, sepsis occured earlier in patients with bi-/tri-malleolar fractures than in patients with uni-malleolar fractures (median day 10 versus 20.5, p=0.022). For the other 6 adverse events, there was no difference in timing between patients with uni-malleolar and patients with bi-/tri-malleolar fractures (p>0.05 for each).

Conclusion:

These precisely described time periods for occurrence of specific adverse events enable heightened awareness amongst orthopaedic surgeons during the first month following open reduction and internal fixation of the ankle. Orthopaedic surgeons should have the lowest threshold for testing for each adverse event during the time period of greatest risk.

Sensitivity of the Saline Load Test for Traumatic Arthrotomy of the Ankle

Category:

Ankle

Introduction/Purpose:

The saline load test is routinely used to evaluate for traumatic arthrotomy in orthopaedics. The purpose of this study was to determine the volume of saline required to detect traumatic arthrotomy of the ankle.

Methods:

42 patients undergoing elective ankle arthroscopy were prospectively enrolled. For each patient, a standard 4 mm anteromedial portal was established. Next, an 18-guage needle was inserted at the site of the anterolateral portal. Sterile saline was slowly injected through the needle until saline extravasated from the anteromedial portal. Saline volumes at the time of extravasation were recorded and analyzed.

Results:

The saline volume required to achieve extravasation ranged from 0.2mL-60.0 mL (Figure 1A). The median saline volume required to achieve extravasation (and interquartile range) was 9.7 mL (3.8-29.6 mL); however, five of 42 patients required volumes between 50.0 mL and 60.0 mL. A total of 50.0 mL was required to achieve 90% sensitivity, 55.0 mL to achieve 95% sensitivity, and 60.0 mL to achieve 99% sensitivity (Figure 1B).

Conclusion:

The previously recommended 30 mL of saline required to reliably detect traumatic arthrotomy of the ankle may be too small a volume. The present study suggests that clinicians should attempt to inject 60 mL in order to effectively rule out a traumatic arthrotomy injury.

Authorship and Citations in Foot and Ankle International from 1980-2017

Category:

Other

Introduction/Purpose:

Orthopaedic foot and ankle surgery is a young and rapidly evolving orthopaedic subspecialty. Little is known regarding the authors contributing to the field. The purpose of this study is to characterize the demographics of the authors publishing foot and ankle research since the inception of the research journal of the American Orthopaedic Foot and Ankle Society.

Methods:

All publications in the journal Foot and Ankle International between 1980 and 2017 were reviewed. Papers were characterized in terms of number of authors, number of institutions, and number of references. The first and corresponding authors were also characterized in terms of country of origin, gender, and degree qualification. Each of these characteristics was tested for trends over time.

Results:

In total, 5,323 publications were reviewed, including 4,297 research articles, 367 case reports, 262 editorials, 159 letters, and 121 technique tips. The mean number of authors per paper increased from 2.3 during the 1980s to 4.3 during the 2010s (p<0.001). The percent of publications with female first authors increased from 4.9% during the 1980s to 13.2% during the 2010s (p<0.001). The country of origin shifted markedly away from the United States during the 1980s towards Europe and other countries during the 2010s (Figure 1). Podiatrists consisted of 1.3% of first authors and 1.4% of corresponding authors—these proportions did not meaningfully change over time (p>0.05). The mean number of references to other work increased from 13.8 during the 1980s to 24.4 during the 2010s (p<0.001).

Conclusion:

The authors of the foot and ankle literature have changed markedly over the past 4 decades. Most notably, there have been shifts towards female and international authorship. The number of authors per paper has also nearly doubled over time. Such trends are likely to continue as the field of foot and ankle grows.

Validated Risk Stratification System for Prediction of Adverse Events Following Open Reduction and Internal Fixation of the Ankle

Category:

Ankle

Introduction/Purpose:

As orthopaedic surgery moves towards bundled payments, there is growing interest in identifying patients at high risk for postoperative adverse events. The purpose of this study is to develop and validate a risk stratification system for the occurrence of adverse events following open reduction and internal fixation (ORIF) of the ankle.

Methods:

Patients undergoing ORIF of closed ankle fractures as part of the National Surgical Quality Improvement Program (NSQIP) were identified. For patients undergoing surgery during 2006-2014, multivariate Cox proportional hazards modeling was used to identify factors that were independently associated with the occurrence of adverse events (including events such as surgical site infection, myocardial infarction, and pulmonary embolism). Based on these results, a nomogram was used to generate a point-scoring system for risk stratification. To evaluate the validity of the point-scoring system, the system was applied to patients undergoing ankle ORIF during 2015-2016.

Results:

Of the 6,140 patients undergoing surgery during 2006-2014, 5.8% developed an adverse event. Based on the Cox proportional hazards regression, patients were assigned points for each of the following statistically significant risk factors: anemia (+2 points), insulin-dependent diabetes (+2 points), age=65 (+1 point), dependent functional status (+1 point), chronic obstructive pulmonary disease (COPD; +1 point), and hypertension (+1 point; Figure 1A). 4,702 patients were identified in the 2015-2016 validation cohort. Among these patients, the risk-stratification system was found to strongly predict the risk for adverse events (p<0.001, Figure 1B).

Conclusion:

The occurrence of adverse events following ankle ORIF is associated with anemia, insulin-dependent diabetes, age=65, dependent functional status, COPD, and hypertension. We present and validate a simple point-scoring risk stratification system to predict the risk of adverse events. Future systems of bundled payments for ankle ORIF should exclude high-risk patients from the bundling systems, or make appropriate adjustments in reimbursement based on risk.

Patient Knowledge Regarding Radiation Exposure from Orthopaedic Foot and Ankle Imaging

Category:

Other

Introduction/Purpose:

Foot and ankle surgeons routinely prescribe diagnostic imaging that exposes patients to potentially harmful ionizing radiation. The purpose of this study is to characterize patients’ knowledge regarding radiation exposure associated with common forms of foot and ankle imaging.

Methods:

A survey was administered to all new patients prior to their first foot and ankle clinic appointments. Patients were asked to compare the amount of harmful radiation associated with chest x-rays to that associated with various types of foot and ankle imaging. Results were tabulated and compared to actual values of radiation exposure from the published literature.

Results:

A total of 890 patients were invited to participate, of whom 791 (88.9%) completed the survey. The majority of patients believed that a foot x-ray, an ankle x-ray, a “low dose” CT scan of the foot and ankle (alluding to cone-beam CT), and a traditional CT scan of the foot and ankle all contain similar amounts of harmful ionizing radiation to a chest x-ray (Table 1). This is in contrast to the published literature, which suggests that foot x-rays, ankle x-rays, cone beam CT scans of the foot and ankle, and traditional CT scans of the foot and ankle expose patients to 0.006, 0.006, 0.127, and 0.833 chest x-rays worth of radiation.

Conclusion:

The results of the present study suggest that patients greatly over-estimate the amount of harmful ionizing radiation associated with plain film and cone-beam CT scans of the foot and ankle. Interestingly, their estimates of radiation associated with traditional CT scans of the foot and ankle were relatively accurate. Results suggest that patients may benefit from increased counseling by surgeons regarding the relatively low risk of radiation exposure associated with plain film and cone-beam CT imaging of the foot and ankle.

Transverse versus longitudinal incision for minimally invasive Achilles tendon repair

Category:

Sports

Introduction/Purpose:

The rate of wound complications following traditional open Achilles tendon repair is reported at 7-8%. In an effort to reduce the rate of wound complications, orthopaedic surgeons have adopted novel minimally invasive techniques. The purpose of this study is to characterize the rate of wound and other early complications following a minimally invasive Achilles tendon repair, to identify any factors associated with increased risk.

Methods:

The postoperative courses of 55 patients who underwent minimally invasive Achilles tendon repair by two surgeons at separate academic medical centers were retrospectively reviewed. Repair technique was similar in all cases, making use of the same commercially available suture-guidance jig, silicone-impregnated deep suture material, and locking stitch technique. However, 31 procedures used a longitudinal incision and a tourniquet (one surgeon’s preference), while 24 procedures used a transverse incision and no tourniquet (the second surgeon’s preference). Of the 24 procedures using transverse incisions, 2 had to be converted to L-shaped incisions to achieve better access to the tendon. The rates of early complications within 3 months after surgery were characterized and compared between patients with differing procedural characteristics.

Results:

Of the 55 patients included in the study, 2 (3.6%) developed wound complications. Both wound complications appeared to be reactions to the deep suture material (see Table 1 for details). There was no statistical difference in the rate of wound complications between patients in the longitudinal incision/tourniquet group and patients in the transverse incision/no tourniquet group (6.5% versus 0.0%; p=0.499). Three patients (5.5%) developed sural neuropraxia, which manifested as mild-to-moderate subjective numbness with sensation remaining intact to light touch. There were no cases of re-rupture. At 3-month follow-up, all 55 patients had intact Thompson tests and well-healed wounds.

Conclusion:

The rate of wound complications following minimally invasive Achilles repair is low at 3.6%. The present study could not demonstrate a difference in risk for wound complications between patients treated with a longitudinal incision and tourniquet and patients treated with a transverse incision and no tourniquet. The wound complications we observed were primarily attributable to inflammatory reactions to the silicone-impregnated deep suture material. Patients should be counseled that although risk for wound complications may be lower with minimally invasive techniques, such techniques do risk sural neuropraxia and deep suture reaction. Further prospective analysis is warranted.

Astrocytic protection of spinal motor neurons but not cortical neurons against loss of Als2/alsin function

Three neurodegenerative diseases affecting upper and/or lower motor neurons have been associated with loss of ALS2/Alsin function: juvenile amyotrophic lateral sclerosis, primary lateral sclerosis and infantile-onset ascending hereditary spastic paralysis. The distinct neuronal vulnerability and the role of glia in these diseases remains, however, unclear. We here demonstrate that alsin-depleted spinal motor neurons can be rescued from defective survival and axon growth by co-cultured astrocytes. The astrocytic rescue is mediated by a soluble protective factor rather than by cellular contact. Cortical neurons are intrinsically as vulnerable to alsin depletion as spinal motor neurons but cannot be rescued by co-cultured astrocytes. To our knowledge, these data provide the first example of non-cell-autonomous glial effects in a recessive form of motor neuron disease and a potential rationale for the higher vulnerability of upper versus lower motor neurons in ALS2/Alsin-linked disorders.

AmineDB: Large scale docking of amines with CYP2D6 and scoring for druglike properties—towards defining the scope of the chemical defense against foreign amines in humans

Organic amines are prevalent in nature and in drugs, especially the psychotherapeutic agents, and a major defense against potentially toxic amines is metabolism by CYP2D6. In order to understand better the constraints on the broad specificity of CYP2D6, 4207 amines were docked into the binding site of this enzyme. Docking poses were found predominantly with the positively charged amino groups closest to Asp301, with aromatic rings close to Phe120 and sometimes extending as far as Phe483. Organic amines that bind best to CYP2D6 tend to have larger molecular weights and logP values. Organic amines that score highly as being druglike, based on a Bayesian model constructed using a 5223-drug training set, are least likely to bind to CYP2D6. This correlation suggests that the set of known drugs, which have been largely designed or selected to avoid high affinity CYP binding, partially encodes the binding site preferences (or rather anti-preferences) of CYP2D6. Finally, in order to benchmark our docking and druglike scoring procedures, an analysis of psychotherapeutic agents is presented. All of these data, including the 4207 AM1-optimized ligand structures in proper ionization states, docking poses and scores, Druglike Scores and Lipinski properties, can be viewed from an online database, the AmineDB.

betaMinor-globin messenger RNA accumulation in reticulocytes governs improved erythropoiesis in beta thalassemic mice after erythropoietin complementary DNA electrotransfer in muscles

Mechanisms governing the induction of effective erythropoiesis in response to erythropoietin (Epo) oversecretion have been investigated in beta thalassemic C57Bl/6(Hbbth) mice. Naked DNA encoding an expression vector for mouse Epo was introduced into skeletal muscles by electrotransfer. A transient increase of serum Epo concentrations with a proportional augmentation of hematocrit values was observed. Various parameters relevant to beta thalassemia were surveyed in blood samples taken before treatment, at the peak of Epo secretion, and when the phenotype reverted to anemia. We measured globin messenger RNA (mRNA) levels in reticulocytes by real-time quantitative polymerase chain reaction, globin chain synthesis levels, and several indicators of erythrocyte membrane quality, including bound alpha chains, bound immunoglobulins, main protein components, and iron compartmentalization. Data indicated that high serum Epo levels primarily affect betaminor-globin mRNA accumulation in reticulocytes. Other changes subsequent to intense Epo stimulation, like increased betaminor/alpha-globin chain synthesis ratio, reduced levels of alpha chains and immunoglobulins bound to membranes, improved spectrin/band 3 ratio, increased red blood cell survival, and improved erythropoiesis appeared as consequences of increased betaminor-globin mRNA levels. This conclusion is consistent with models postulating that intense Epo stimulation induces the expansion and differentiation of erythroid progenitors committed to fetal erythropoiesis. Although phenotypic correction was partial in mice, and comparable achievements will probably be more difficult to obtain in humans, naked DNA electrotransfer may provide a safe and low-cost method for reassessing the potentials of Epo as an inducer of fetal erythropoiesis reactivation in patients with beta thalassemia.

Delivering erythropoietin through genetically engineered cells

Erythropoietin (Epo) is a glycoprotein hormone produced by genetic engineering. Many pathologic conditions could benefit from its administration, such as chronic renal failure or hemoglobinopathies. Epo secretion from genetically modified tissued could be proposed to patients only if the protocol is low cost and low risk. For that purpose, retroviral vectors and adeno-associated vectors expressing the Epo cDNA were developed. Gene transfer was performed into skeletal muscles. To avoid polycythemia, a tetracycline-regulated system was used to control the levels of protein secretion in vivo. beta-thalassemias are among diseases that could benefit from an Epo gene transfer. beta-thalassemias are attributable to deficient synthesis of beta-globin and accumulation of unpaired alpha-chains. Stimulation of fetal globin synthesis is one strategy to correct the globin chain imbalance. There is evidence that Epo could play this role. In a mouse model of beta-thalassemia, an adeno-associated vector expressing the Epo cDNA was injected intramuscularly. Epo was secreted continuously during at least 1 yr. Erythropoiesis was improved in those mice by increasing the synthesis of fetal hemoglobin.

Improvement of erythropoiesis in beta-thalassemic mice by continuous erythropoietin delivery from muscle

beta-Thalassemias are highly prevalent genetic disorders that can cause severe hemolytic anemia. The main pathophysiologic feature of beta-thalassemia is the accumulation of unpaired alpha-globin chains in erythrocyte precursors and red blood cells (RBCs). This accumulation alters cell membrane function and results in early cell destruction and ineffective erythropoiesis. Correction of globin chain imbalance through the induction of fetal hemoglobin (HbF) synthesis is a tentative therapeutic approach for this class of diseases. In short-term in vitro or in vivo assays, recombinant human erythropoietin increases the frequency of erythroid precursors programmed to HbF in humans and to beta-minor globin in mice. In contrast, long-term treatment of beta-thalassemic patients did not induce HbF significantly. We took advantage of highly efficient adeno-associated virus-mediated (AAV-mediated) gene transfer into mouse muscle to induce a robust and sustained secretion of mouse erythropoietin in beta-thalassemic mice, which represent a suitable model for human beta-thalassemia intermedia. A 1-year follow-up of 12 treated animals showed a stable correction of anemia associated with improved RBC morphology, increased beta-minor globin synthesis, and decreased amounts of alpha-globin chains bound to erythrocyte membranes. More effective erythropoiesis probably accounted for a reduction of erythroid cell proliferation, as shown by decreased proportions of circulating reticulocytes and by reduced iron 59 ((59)Fe) incorporation into erythroid tissues. This study indicates that the continuous delivery of high amounts of autologous erythropoietin induced a sustained stimulation of beta-minor globin synthesis and a stable improvement of erythropoiesis in the beta-thalassemic mouse model. (Blood. 2000;95:2793-2798)

Structure of adeno-associated virus vector DNA following transduction of the skeletal muscle

The skeletal muscle provides a very permissive physiological environment for adeno-associated virus (AAV) type 2-mediated gene transfer. We have studied the early steps leading to the establishment of permanent transgene expression, after injection of recombinant AAV (rAAV) particles in the quadriceps muscle of mice. The animals received an rAAV encoding a secreted protein, murine erythropoietin (mEpo), under the control of the human cytomegalovirus major immediate-early promoter and were sacrificed between 1 and 60 days after injection. The measurement of plasma Epo levels and of hematocrits indicated a progressive increase of transgene expression over the first 2 weeks, followed by a stabilization at maximal plateau values. The rAAV sequences were analyzed by Southern blotting following neutral or alkaline gel electrophoresis of total DNA from injected muscles. While a high number of rAAV sequences were detected during the first 5 days following the injection, only a few percent of these sequences was retained in the animals analyzed after 2 weeks, in which transgene expression was maximal. Double-stranded DNA molecules resulting from de novo second-strand synthesis were detected as early as day 1, indicating that this crucial step of AAV-mediated gene transfer is readily accomplished in the muscle. The templates driving stable gene expression at later time points are low in copy number and structured as high-molecular-weight concatemers or interlocked circles. The presence of the circular form of the rAAV genomes at early time points suggests that the molecular transformations involved in the formation of stable concatemers may involve a rolling-circle type of DNA replication.

Control of erythropoietin secretion by doxycycline or mifepristone in mice bearing polymer-encapsulated engineered cells

Cell encapsulation offers a safe and manufacturable method for the systemic delivery of therapeutic proteins from genetically engineered cells. However, control of dose delivery remains a major issue with regard to clinical application. We generated populations of immortalized murine NIH 3T3 fibroblasts that secrete mouse erythropoietin (Epo) in response to stimulation by doxycycline or mifepristone. Engineered cells were introduced into AN69 hollow fibers, which were implanted in the peritoneal cavity or recipient mice. Animals receiving doxycycline or mifepristone showed stable polyhemia and increased serum Epo concentrations over a 6-month observation period, whereas animals not receiving the inducer drug had normal hematocrits. Epo secretion could be switched on and off, depending on the presence of doxycycline in the drinking water. In contrast, polyhemia was hardly reversible after subcutaneous injections of mifepristone. These data show that a permanent and regulated systemic delivery of a therapeutic protein can be obtained by the in vivo implantation of engineered allogeneic cells immunoprotected in membrane polymers.

Selective uptake and sustained expression of AAV vectors following subcutaneous delivery

BACKGROUND

Recombinant adeno-associated viral (rAAV) vectors are capable of long-term expression of secreted and intracellular proteins following delivery to muscle, liver, and the central nervous system. In this study, we have evaluated subcutaneous injection of rAAV encoding a variety of transgenes as an alternative route of administration for the systemic delivery of therapeutic proteins.

METHODS

rAAV vectors encoding the human factor IX, human interferon-alpha 2a, murine erythropoietin (epo), and Escherichia coli lacZ genes were used for subcutaneous delivery into mature immunocompetent mice. Expression of factor IX and interferon in mouse serum was measured by ELISA. Expression of Epo was monitored by an increase in hemotocrit and by RIA. The tissue tropism of AAV transduction was determined by histochemistry following administration of the lacZ vector.

RESULTS

Long-term protein expression (at least one year) is demonstrated in the serum of immunocompetent mice following subcutaneous delivery of AAV vectors encoding the human factor IX and interferon genes. The murine epo gene delivered via this route resulted in levels of Epo that correlate with increased hematocrits of up to 90% for a duration of nine months. rAAV encoding the lacZ gene revealed that the panniculus carnosus, a skeletal muscle layer of the skin, was transduced upon subcutaneous administration.

CONCLUSIONS

This study shows that long-term expression of secreted proteins can be achieved using rAAV vectors injected subcutaneously as a single administration. The observation that the panniculus carnosus is the primary tissue transduced by rAAV illustrates the high tropism of rAAV for skeletal muscle.

Control of erythropoietin delivery by doxycycline in mice after intramuscular injection of adeno-associated vector

We reported previously that controlled expression of a foreign gene in response to tetracycline derivative can be accomplished in mice by the autologous transplantation of retrovirus-modified muscle cells. Although regulated systemic delivery of therapeutic proteins from engineered tissues has potential clinical application, the transplantation of muscle cells is not currently feasible in humans. Several studies have shown that a single injection of adeno-associated virus (AAV) vectors into mouse muscle results in long-term expression of reporter genes as well as sustained delivery of proteins into the serum. Because this method is potentially applicable clinically, we constructed an AAV vector in which the expression of the mouse erythropoietin (Epo) cDNA is modulated in response to doxycycline. The vector was injected intramuscularly in normal mice. We observed that hematocrit and serum Epo concentrations could be modulated over a 29-week period in response to the presence or absence of doxycycline in the drinking water of these animals. Thus, a regulated gene expression cassette can be incorporated into a single AAV vector, such that intramuscular injection of the vector allows sustained and regulated expression of a desired gene.

Regulation of gene expression in vivo following transduction by two separate rAAV vectors

Control of gene expression is important to gene therapy for purposes of both dosing and safety. In vivo regulation of gene expression was demonstrated following co-injection of two separate recombinant adeno-associated virus vectors, one encoding an inducible murine erythropoietin transgene and the other a transcriptional activator, directly into the skeletal muscle of adult immunocompetent mice. Transcription was controlled by systemic administration or withdrawal of tetracycline over an 18 week period, demonstrating that the two vectors were capable of transducing the same cell. Cellular or humoral immune responses against the transactivator protein were not detected.

Transcriptional modulation of foreign gene expression in engineered somatic tissues

Many diseases that are candidates for gene therapy require that the therapeutic gene expression level be controlled to ensure biological efficacy and to prevent toxic effects. Various systems have been described that allow transcriptional regulation by artificial chimeric transactivators in mammalian cells. This paper describes these various systems and discusses their interests for gene therapy.

Efficient and stable adeno-associated virus-mediated transduction in the skeletal muscle of adult immunocompetent mice

Recombinant adeno-associated virus (rAAV) vectors were evaluated for gene transfer into the skeletal muscle of adult immunocompetent mice. A study using a vector encoding nuclear localized beta-galactosidase (rAAV-nls-lacZ) examined: (i) the efficiency and duration of transgene expression; (ii) the status of the AAV genome in the transduced fibers; and (iii) the possibility of improving gene transfer by inducing muscle regeneration. In the absence of regeneration, the injection of 1.7 x 10(7) particles in the quadriceps resulted in gene transfer to 10-70% of myofibers. Histological analysis indicated that the vector was able to reach myofiber nuclei distant from the injection point. Cellular infiltrates were absent at early time points but became conspicuous in the vicinity of some positive fibers at 4-8 weeks and subsided by 26 weeks. Southern analysis indicated that one to three copies of the vector genome were present per cell genome equivalent. They were associated with high-molecular-weight DNA in the form of tandem oligomers or interlocked circles. Gene transfer was not facilitated in the regenerating muscle. Rather, an early inflammatory response resulted in the elimination of most positive fibers after 8 weeks. The presence of regenerated fibers with beta-galactosidase-positive nuclei suggested that myoblasts had been transduced and were able to fuse to form new fibers. Gene transfer in the absence of immune reactions against the transgene product was studied by injecting mice with a rAAV carrying the murine erythropoietin (mEpo) cDNA. Dose-dependent elevation in the hematocrit was measured for over 200 days and corresponded to 5- to 20-fold increases in plasma Epo levels. We conclude that AAV vectors efficiently and stably transduce post-mitotic muscle fibers and myoblasts in vivo.

Transcription of the HS2 enhancer toward a cis-linked gene is independent of the orientation, position, and distance of the enhancer relative to the gene

The locus control region (LCR) regulates transcription of the downstream beta-like globin genes 10 to 50 kb away. Among hypersensitive sites HS4, -3, -2, and -1, which define the LCR in erythroid cells, HS2 possesses prominent enhancer function. The mechanism by which the HS2 enhancer and other functional components of the LCR act over the distance is not clear. We have used reverse transcription-PCR and RNase protection assays to analyze the transcriptional statuses of both the endogenous and the transfected HS2 enhancer in erythroid K562 cells. A novel pattern of HS2 enhancer transcription was observed. The endogenous HS2 enhancer was transcribed predominantly in the direction toward the downstream globin genes. The HS2 enhancer in transfected recombinant chloramphenicol acetyltransferase (CAT) plasmids was also transcribed predominantly toward the CAT gene, regardless of whether the enhancer was placed (i) in the genomic or reverse genomic orientation, (ii) in a position 5' or 3' to the gene, or (iii) at various distances up to 6 kb from the gene. The orientation, position, and distance independence in gene-tropic transcription of the HS2 enhancer correlates with the observed orientation, position, and distance independence of HS2 enhancer function and suggests that enhancer transcription may play a role in enhancer function.

Long-term control of erythropoietin secretion by doxycycline in mice transplanted with engineered primary myoblasts

We investigated tetracycline regulation of gene expression in an experimental model relevant to gene therapy. Mouse primary myogenic cells were engineered for doxycycline-inducible and skeletal muscle-specific expression of the mouse erythropoietin (Epo) cDNA by using two retrovirus vectors. Gene expression increased 200 fold in response to both myogenic cell differentiation and doxycycline stimulation. After transplantation of transduced cells into mouse skeletal muscles, Epo secretion could be iteratively switched on and off over a five-month period, depending on the presence or the absence of doxycycline in the drinking water. We conclude that tetracycline regulation provides a suitable control system for adjusting the delivery of therapeutic proteins from engineered tissues over long periods of time.

Modulation of erythropoietin delivery from engineered muscles in mice

In most relevant diseases, the permanent systemic delivery of a therapeutic protein from engineered cells might be proposed only if secretion levels can be regulated. The tetracycline resistance operon of Escherichia coli provides a transcriptional regulatory system effective in mammalian cells, which could be used for that purpose. A chimeric transactivator (tTA) consisting of the tetracycline repressor fused to the transactivation domain of the herpes simplex virus VP16 protein stimulates transcription by binding a minimal cytomegalovirus (CMV) promoter containing repeats of the tetracycline operator (tetO-CMV). Binding is abolished by tetracycline, thus impairing promoter activation. We have transduced C2.7 myoblasts with two U3-deleted retroviral vectors containing these regulatory elements. The tetP-Epo vector expressed the murine erythropoietin (Epo) cDNA under the control of the tetO-CMV promoter. The D-De-tTA vector expressed tTA under the control of the muscle-specific human desmin enhancer-promoter. Northern blot analysis showed background Epo mRNA expression in myoblasts. Myotubes differentiation induced tTA expression, leading to a 28-fold increase of Epo mRNAs, which was suppressed by tetracycline. Basal Epo secretion in myoblasts increased 23- to 41-fold during the formation of multinucleated myotubes, and turned back close to myoblast level when tetracycline was added. Myoblasts transduced with both vectors and treated with mitomycin with the aim to prevent tumor formation were engrafted in skeletal muscles of syngeneic C3H mice. Hematocrit levels were significantly higher in animals bearing cells transduced with both vectors than in control animals grafted with cells transduced with the Epo vector only. This difference was abolished when tetracycline was given to mice. These data indicate that the tetracycline regulatory elements can modulate transcription in the context of retroviral vector genomes, and that this system can be used to control the in vivo delivery of a therapeutic protein from genetically modified muscles.

Continuous secretion of human soluble CD4 in mice transplanted with genetically modified cells

Somatic transgenesis can be used to confer endogenous production of proteins with therapeutic properties. One such product, recombinant soluble human CD4 (sCD4), has been shown to be an efficient inhibitor of human immunodeficiency virus 1 (HIV-1) in vitro, but its too short half-life in vivo has impaired long-term clinical trials in AIDS patients. Using a retroviral vector, we introduced the cDNA of sCD4 into primary mouse fibroblasts. The cells were enclosed in a lattice of collagen and synthetic fibers coated with basic fibroblast growth factor, and implanted in the peritoneal cavity of syngeneic mice. Implantation of such sCD4-secreting organoids into cyclosporin A-treated C3H mice elicited a strong antibody response against sCD4. Implantation of sCD4-secreting organoids into immunotolerant mice (transgenic for transmembrane human CD4) resulted in continuous sCD4 production, detected during 60 days in animal sera. The serum levels obtained were significant, but too limited as yet for anti-HIV purposes. Nevertheless, this model may be of interest in various fields, as it provides the first demonstration that one potentially therapeutic protein, despite its half-life of a few hours, could remain present in vivo 2 months after a single somatic transgenesis.

Long-term delivery of a lysosomal enzyme by genetically modified fibroblasts in dogs

We have evaluated the feasibility and efficacy of intraperitoneal implants (neo-organs) for protein delivery in large animals. Skin biopsies were taken from four healthy dogs. Primary fibroblast cultures were transduced with a retroviral vector coding for the human beta-glucuronidase. One to six lattices each containing 10(9) skin fibroblasts were implanted into the omentum of the donor animal. Laparotomies performed at regular intervals showed vascularized neo-organs without local inflammation. Human beta-glucuronidase levels equivalent to 0.8 to 3.1% of the endogenous canine activity were detected for up to 340 days on liver biopsy samples. These results indicate that neo-organs can be considered for the long-term delivery of therapeutic proteins or enzymes in humans.

Correction of lysosomal storage in the liver and spleen of MPS VII mice by implantation of genetically modified skin fibroblasts

Genetic defects of lysosomal hydrolases result in severe storage diseases and treatments based on enzyme replacement have been proposed. In mice lacking beta-glucuronidase, which develop a disease homologous to human mucopolysaccharidosis type VII (Sly syndrome), we have used autologous implants of genetically-modified skin fibroblasts for the continuous in vivo production of the enzyme. The human beta-glucuronidase cDNA was introduced with a retroviral vector into mutant mice skin fibroblasts grown in primary culture. Fourteen mutant mice were implanted intraperitoneally with these modified cells embedded into collagen lattices. All animals expressed beta-glucuronidase from the vascularized neo-organs that developed after implantation and accumulated the enzyme in their tissues. A complete disappearance of the lysosomal storage lesions was observed in their liver and spleen.

A clinical trial comparing a new NSAID (droxicam) and piroxicam in spinal osteoarthritis

This double-blind, parallel, controlled and randomized trial compares the clinical efficacy and tolerance of a new NSAID (pro-drug of piroxicam), droxicam, at the dose of 20 mg/day against that of piroxicam at the same dose. The comparison is drawn after the administration to 30 patients with spinal osteoarthritis during 8 weeks after a single-blind placebo-period run-in of 7 days. Results show that both drugs improve, with statistical significance, all parameters evaluated (pain intensity, morning stiffness, nocturnal pain, pain after getting up and after 30 min standing, difficulty in daily living, frequency of pain exacerbations and the ability to do several daily activities). No statistically significant differences were found between groups. Only one case in the droxicam group and two in the piroxicam group reported subjective complaints of mild intensity that did not require additional treatment or interruption of the study.

[MR tomography in intracranial meningiomas]

The typical findings of intracranial meningiomas seen in 24 patients are described. The signal intensities at different acquisition parameters are analysed and optimal pulse sequences derived from these data. In 90% of the patients MR-tissue parameters were measured and correlated with the histological findings. Marked prolongation of T2-times was found in tumours showing regressive changes.

De novo membrano-proliferative glomerulonephritis in a renal allograft

De novo glomerulonephritis (GN) in the graft is an uncommon complication of renal transplantation. We report a case of de novo membrano-proliferative GN which occurred in a second cadaver allograft in a 42-year-old woman, who developed severe hypertension, nephrotic syndrome, and progressive renal failure. Our material and a review of the literature suggest an incidence of de novo GN of about 0.5-2%. In contrast to most of the cases described by other authors, the membrano-proliferative type of de novo GN in renal allografts seems to be very rare.