Drosophila melanogaster: a new model to study cisplatin-induced neurotoxicity.

Platinum-based compounds are widely used and effective chemotherapeutic agents; however, sensory peripheral neuropathy is a dose-limiting and long term side effect for 20-30% of patients. A critical question is whether the mechanisms of cell death underlying clinical efficacy can be separated from the effects on neurons in order to develop strategies that prevent platinum-induced neuropathy. In rodent dorsal root ganglion neurons (DRG), cisplatin has been shown to bind and damage neuronal DNA, inducing apoptosis; however genetic manipulation in order to study mechanisms of this phenomenon in the rodent model system is costly and time-consuming. Drosophila melanogaster are commonly used to study neurological disorders, have DNA damage-apoptosis mechanisms homologous to mammalian systems, and have readily-available, inexpensive tools for rapid genetic manipulation. We therefore sought to develop adult Drosophila as a new model to study cisplatin-induced neurotoxicity. Adult Drosophila were exposed to 10, 25, 50, 100, 200 and 400 µg/ml cisplatin for 3 days and observed for fly survival and geotactic climbing behavior, cisplatin-DNA binding and cellular apoptosis. On day 3, 50 µg/ml cisplatin reduced the number of flies able to climb above 2 cm to 43% while fly survival was maintained at 92%. 100% lethality was observed at 400 µg/ml cisplatin. Whole fly platinum-genomic DNA adducts were measured and found to be comparable to adduct levels previously measured in rat DRG neurons. Brain, ovaries, kidney and heart harvested from cisplatin treated flies were stained for active caspase 3. Apoptosis was found in ovaries and brain but not in heart and kidney. Brain apoptosis was confirmed by transmission electron microscopy. Expression of the anti-apoptotic baculoviral protein, p35, in neurons using the GAL4-UAS system prevented cisplatin-induced apoptosis in the brain and restored climbing behavior. In conclusion, cisplatin-induced behavioral and apoptotic changes in Drosophila resemble those seen in mammals. Furthermore, the use of lethality and climbing assays combined with powerful gene manipulation, make Drosophila a suitable model to study mechanisms of cisplatin neurotoxicity.

Abnormal loading of the hip and knee joints in unilateral hip osteoarthritis persists two years after total hip replacement.

A total hip replacement (THR) is a common and routine procedure to reduce pain and restore normal activity. Gait analysis can provide insights into functional characteristics and dynamic joint loading situation not identifiable by clinical examination or static radiographic measures. The present prospective longitudinal study tested whether 2 years after surgery a THR would restore dynamic loading of the knee and hip joints in the frontal plane to normal. Instrumented gait analysis was performed shortly before surgery and approximately 2 years after THR on 15 unilateral hip osteoarthritis (OA) patients. 15 asymptomatic matched individuals were recruited as healthy controls. Results showed that abnormal joint loading persisted 2 years after THR. The 2nd external knee adduction moment in terminal stance in the affected (-34%, p = 0.002, d = 1.22) and non-affected limb (-25%, p = 0.035, d = 0.81) was lower compared to controls and thus indicated a shift in the knee joint load distribution from medial to lateral. A correlation analysis revealed that a smaller hip range of motion explained 46% of 2nd knee adduction moment alterations. In contrast, the 2nd external hip adduction moment in terminal stance was postoperatively higher in the affected (+22%, p = 0.007, d = 1.04) and non-affected limb (+22%, p = 0.005, d = 1.05). Here, 51% of 2nd hip adduction moment alterations can be explained with a greater hip adduction angle. Patients with a THR may therefore be at higher risk for abnormal joint loading and thus for the development of OA in other joints of the lower extremities. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Unilateral hip osteoarthritis: The effect of compensation strategies and anatomic measurements on frontal plane joint loading.

In order to reduce pain caused by the affected hip joint, unilateral hip osteoarthritis patients (HOAP) adopt characteristic gait patterns. However, it is unknown if the knee and hip joint loading in the non-affected (limbnon-affected ) and the affected (limbaffected ) limb differ from healthy controls (HC) and which gait parameters correlate with potential abnormal joint loading. Instrumented 3D-gait analysis was performed on 18 HOAP and 18 sex, age, and height matched HC. The limbnon-affected showed greater first and second peak external hip adduction moments (first HAM: +15%, p = 0.014; second HAM: +15%, p = 0.021, respectively), than seen in HC. In contrast, the second peak external knee adduction moment (KAM) in the limbaffected is reduced by about 23% and 30% compared to the limbnon-affected and HC, respectively. Furthermore, our patients showed characteristic gait compensation strategies including reduced peak vertical forces (pvF), a greater foot progression angle (FPA), and reduced knee range of motion (ROM) in the limbaffected . The limbaffected was 5.6 ± 3.8 mm shorter than the limbnon-affected . Results of stepwise regression analyses showed that increased first pvF explain 16% of first HAM alterations, whereas knee ROM and FPA explain 39% of second KAM alterations. We therefore expect an increased rate of progression of OA in the hip joint of the limbnon-affected and suggest that the shift in the medial-to-lateral knee joint load distribution may impact the rate of progression of OA in the limbaffected . The level of evidence is III. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1764-1773, 2017.

Unilateral hip osteoarthritis: Its effects on preoperative lower limb muscle activation and intramuscular coordination patterns.

The objective of this study was to test if patients with unilateral hip osteoarthritis (OA) show greater muscle activity asymmetry between their affected and non-affected limbs than healthy controls between their left and right limbs. Seventeen patients with unilateral hip OA (7 females, 10 males) and 17 age-matched healthy controls (7 females, 10 males) participated in this study. Both groups performed instrumented gait analysis at comparable speeds. Muscle activity was recorded simultaneously for the tibialis anterior (TA), gastrocnemius medialis (GM), vastus lateralis (VL), semitendinosus (ST), tensor fasciae latae (TFL), and gluteus medius (GLM) muscles. In hip OA patients, EMG data showed greater activity of the TA muscle in the non-affected limb, and greater TFL muscle activity in the affected limb. Compared to healthy controls, greater asymmetries between paired limbs were observed for the TA and GM muscles. Finally, the TFL muscle of the affected limb contributed more to the total limb muscle activity than did the non-affected limb. The observed alterations in TA and GM muscle activity in hip OA patients may be due to the greater peak braking and peak vertical forces measured in the non-affected limb. Contrary to this, greater TLF muscle activity of the affected limb indicates the demands put on stabilizing the hip during stance phase. Further studies are necessary to test whether leg length discrepancy affects muscle activation alterations between the affected and non-affected limb in unilateral hip OA patients.

Effects of electrical stimulation on rat limb regeneration, a new look at an old model.

Limb loss is a devastating disability and while current treatments provide aesthetic and functional restoration, they are associated with complications and risks. The optimal solution would be to harness the body's regenerative capabilities to regrow new limbs. Several methods have been tried to regrow limbs in mammals, but none have succeeded. One such attempt, in the early 1970s, used electrical stimulation and demonstrated partial limb regeneration. Several researchers reproduced these findings, applying low voltage DC electrical stimulation to the stumps of amputated rat forelimbs reporting "blastema, and new bone, bone marrow, cartilage, nerve, skin, muscle and epiphyseal plate formation". In spite of these encouraging results this research was discontinued. Recently there has been renewed interest in studying electrical stimulation, primarily at a cellular and subcellular level, and studies have demonstrated changes in stem cell behavior with increased proliferation, differentiation, matrix formation and migration, all important in tissue regeneration. We applied electrical stimulation, in vivo, to the stumps of amputated rat limbs and observed significant new bone, cartilage and vessel formation and prevention of neuroma formation. These findings demonstrate that electricity stimulates tissue regeneration and form the basis for further research leading to possible new treatments for regenerating limbs.

ADAM17 controls endochondral ossification by regulating terminal differentiation of chondrocytes.

Endochondral ossification is a highly regulated process that relies on properly orchestrated cell-cell interactions in the developing growth plate. This study is focused on understanding the role of a crucial regulator of cell-cell interactions, the membrane-anchored metalloproteinase ADAM17, in endochondral ossification. ADAM17 releases growth factors, cytokines, and other membrane proteins from cells and is essential for epidermal growth factor receptor (EGFR) signaling and for processing tumor necrosis factor alpha. Here, we report that mice lacking ADAM17 in chondrocytes (A17ΔCh) have a significantly expanded zone of hypertrophic chondrocytes in the growth plate and retarded growth of long bones. This abnormality is caused by an accumulation of the most terminally differentiated type of chondrocytes that produces a calcified matrix. Inactivation of ADAM17 in osteoclasts or endothelial cells does not affect the zone of hypertrophic chondrocytes, suggesting that the main role of ADAM17 in the growth plate is in chondrocytes. This notion is further supported by in vitro experiments showing enhanced hypertrophic differentiation of primary chondrocytes lacking Adam17. The enlarged zone of hypertrophic chondrocytes in A17ΔCh mice resembles that described in mice with mutant EGFR signaling or lack of its ligand transforming growth factor α (TGFα), suggesting that ADAM17 regulates terminal differentiation of chondrocytes during endochondral ossification by activating the TGFα/EGFR signaling axis.