Glutamate regulates the expression of apoptosis-related genes and triggers the apoptosis of fibroblasts in rotator cuff tendons. Subacromial bursitis is always accompanied by symptomatic rotator cuff tear (RCT). However, no study has been reported on the presence of glutamate in subacromial bursa and on its involvement of shoulder pain in patients who had RCT. The purposes of this study were to determine whether the glutamate expression in subacromial bursa is associated with the presence of RCT and with the severity of shoulder pain accompanying RCT.

Subacromial bursal tissues were harvested from patients who underwent arthroscopic rotator cuff tendon repair or glenoid labral repair with intact rotator cuff tendon. Glutamate tissue concentrations were measured, using a glutamate assay kit. Expressions of glutamate and its receptors in subacromial bursae were histologically determined. The sizes of RCT were determined by arthroscopic findings, using the DeOrio and Cofield classification. The severity of shoulder pain was determined, using visual analog scale (VAS). Any associations between glutamate concentrations and the size of RCT were evaluated, using logistic regression analysis. The correlation between glutamate concentrations and the severity of pain was determined, using the Pearson correlation coefficient. Differences with a probability <0.05 were considered statistically significant.

Glutamate concentrations showed significant differences between the torn tendon group and the intact tendon group (P = 0.009). Concentrations of glutamate significantly increased according to increases in tear size (P < 0.001). In histological studies, the expressions of glutamate and of its ionotropic and metabotropic receptors have been confirmed in subacromial bursa. Glutamate concentrations were significantly correlated with pain on VAS (Rho=0.56 and P =0.01).

The expression of glutamate in subacromial bursa is significantly associated with the presence of RCT and significantly correlated with its accompanying shoulder pain.

Acknowledgements: This research was supported by the Basic Science Research Program, through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2015R1D1A3A01018955 and 2017R1D1A1B03035232).

The use of mesenchymal stem cell (MSCs) for intervertebral disc (IVD) regeneration has been extensively explored in the last two decades. MSCs are potent cell types that can be easily and safely harvested due to their abundancy and availability. Moreover, they are characterized by the capacity to differentiate towards IVD cells as well as release growth factors to support resident cell metabolism and recruit local progenitor cells to induce endogenous repair of degenerated IVDs. This talk will outline the characteristics of the main MSC sources and their effect towards IVD regeneration based on available preclinical and clinical evidence. In addition, innovative aspects of MSC-derived cell-free therapies will also be discussed.

The biological understanding for the disease progression osteoarthritis (OA) has uncovered specific biomarkers from either synovial fluid, articular chondrocytes or synoviocytes that can be used to diagnose the disease. Examples of these biomarkers include interleukin-1β (IL-1β) or collagen II fragments (1, 2). In parallel, isolation of chondrocytes or bone marrow derived mesenchymal stromal cells (MSCs) has yielded cell-based strategies that have shown long- term beneficial effects in a specific cohort of patients, specifically in traumatic cartilage lesions (2). This latter finding shows that patient stratification of OA is an important tool to both match patients for a specific treatment and to develop novel therapies, especially disease modifying drugs. In order to create disease stage specific therapies, the use of next generation analysis tools such as RNAseq and metabolomics, has the potential to decipher specific cellular and molecular endotypes. Alongside greater understanding of the clinical phenotype (e.g. imaging, pain, co- morbidities), therapies can be designed to alleviate the symptoms of OA at specific points of the disease in patients. This talk will outline the current biological understanding of OA and discuss how patient stratification could assist in the design of innovative therapies for the disease.

Acknowledgements: This presentation was supported by the COST action, CA21110 – Building an open European Network on Osteoarthritis Research (NetwOArk)

Osteoarthritis (OA) is the most common degenerative joint disorder. Its multifactorial etiology includes age, sex, joint overloading, genetic or nervous influences. In particular, the autonomic nervous system is increasingly gaining in importance. Its two branches, the sympathetic (SNS) and parasympathetic nervous system, are well-balanced under healthy conditions. OA patients seem to be prone to an autonomic imbalance and therefore, we analyzed their autonomic status.

More than 200 participants including patients with early and late stage knee OA (before and 1 year after knee replacement surgery) and healthy probands (age-matched) were analyzed. Heart rate variability was measured via electrocardiogram to assess long-term sympathetic (low-frequency=LF) and parasympathetic (high-frequency=HF, pRR50) activities or general variability (RMSSD, SDRR). Serum cortisol concentrations were measured by ELISA. Perceived chronic stress (PSQ) was assessed via questionnaire. Multivariant regression was performed for data analysis. LF/HF value of early OA was slightly increased compared to healthy controls but significantly higher compared to late OA patients before (p>0.05) and after TKR (p>0.01). HF in late OA patients before TKR was significantly decreased compared to patients after TKR (p>0.001) or healthy controls (p>0.05). Healthy probands exhibited the highest SDRR values, early OA patients had slightly lower levels and late OA patients before TKR displayed significantly reduced SDRR (p>0.001). The same differences were observed in pRR50 and RMSSD. Serum cortisol concentrations and PSQ scores increased in late OA patients before TKR. At the time point of TKR, women with beta blocker medication had significantly higher age (71 ± 9 years) than those without (63 ± 12 years)(p>0.01). An autonomic dysfunction with sympathetic dominance occurs in OA patients. The fact that beta blocker medication in women delayed the need of TKR indicates that SNS inhibition might counteract OA. Future therapeutic interventions for OA should consider a systemic approach with special regard on the ANS.

Translational models for OA have used a variety of small (mouse, rat) and large (sheep, pig) animal models to evaluate the efficacy of a specific therapy. Clinical trials based on the results of these animal models have yielded mixed results with respect to the treatment of the disease. Due to greater stringency in EU regulations in the use of animal models for research, ex vivo models of OA (e.g. cartilage explants, bioreactors) are being developed to mimic human joint motion as well as the inflammatory milieu (e.g. IL-1β) that can be used to understand efficacy of therapy in a physiological environment. The development of these models can enable therapies to undergo clinical trials in patients without the necessity for long-term animal studies. This presentation will describe the state of the art in this field and will discuss whether there is potential to speed up translation from bench to bedside in the future.

The HIPGEN study funded under EU Horizon 2020 (Grant 7792939) has the aim to investigate the potential of the first regenerative cell therapy for the improvement of recovery after muscle injury in hip fracture patients. For this aim we intramuscularly injected placental derived mesenchymal stromal cells during hip fracture arthroplasty. Despite not having reached the primary endpoint, which was the Short Physical Performance Battery, we could observe an increase in abductor muscle strength and a faster return to balance looking at symmetry in insole measurements during follow up.

Bone regeneration is a complex but very well organized process in which the immune system has a decisive role. The adaptive immune system and its experience level (percentage of effector and memory T cells) has been proven to influence the healing cascade especially in the early healing phases. This opens the possibility of an early intervention to enhance bone healing during the primary clinical treatment. Patients stratified for possible delayed bone healing could benefit from immunomodulatory treatment approaches. In pre-clinical studies cells and signaling molecules have been identified that could represent promising candidates to help patients in need.

The rotator cuff tendinopathy is one of the most common shoulder problems leading to full-thickness rotator cuff tendon tear and, eventually, to degenerative arthritis. Recent research on rotator cuff tendon degeneration has focused on its relationship to cell death. The types of cell death known to be associated with rotator cuff tendon degeneration are apoptosis, necrosis, and autophagic cell death. The increased incidence of cell death in degenerative tendon tissue may affect the rates of collagen synthesis and repair, possibly weakening tendon tissue and increasing the risk of tendon rupture. The biomolecular mechanisms of the degenerative changes leading to apoptotic cell death in rotator cuff tenofibroblasts have been identified as oxidative-stress-related cascade mechanisms. Furthermore, apoptosis, necrosis, and autophagic cell death are all known to be mediated by oxidative stress, a condition in which ROS (reactive oxygen species) are overproduced. Lower levels of oxidative stress trigger apoptosis; higher levels mediate necrosis. Although the signaltransduction pathway leading to autophagy has not yet been fully established, ROS are known to be essential to autophagy. A neuronal theory regarding rotator cuff degeneration has been developed from the findings that glutamate, a neural transmitter, is present in increased concentrations in tendon tissues with tendinopathy and that it induces rat supraspinatus tendon cell death. Recent studies have reported that hypoxia involved in rotator cuff tendon degeneration. Because antioxidants are known to scavenge for intracellular ROS, some studies have been conducted to determine whether antioxidants can reduce cell death in rotator cuff tendon-origin fibroblasts. The first study reported that an antioxidant has the ability to reduce apoptosis in oxidative-stressed rotator cuff tenofibroblasts. The second study reported that antioxidants have both antiapoptotic effects and antinecrotic effects on rotator cuff tendon-origin fibroblasts exposed to an oxidative stimulus. The third study reported that an antioxidant has antiautophagic-cell-death effects on rotator cuff tendon-origin fibroblasts exposed to an oxidative stimulus. The fourth study reported that glutamate markedly increases cell death in rotator cuff tendonorigin fibroblasts. The glutamate-induced cytotoxic effects were reduced by an antioxidant, demonstrating its cytoprotective effects against glutamate-induced tenofibroblast cell death. The fifth study reported that hypoxia significantly increases intracellular ROS and apoptosis. The hypoxia-induced cytotoxic effects were markedly attenuated by antioxidants, demonstrating their cytoprotective effects against hypoxia-induced tenofibroblast cell death. In conclusion, antioxidants have cytoprotective effects on tenofibroblasts exposed in vitro to an oxidative stressor, a neurotransmitter, or hypoxia. These cytoprotective effects result from antiapoptotic, antinecrotic, and antiautophagic actions involving the inhibition of ROS formation. These findings suggest that antioxidants may have therapeutic potential for rotator cuff tendinopathy. Further studies must be conducted in order to apply these in vitro findings to clinical situations.

Osteoarthritis (OA) is the most common joint disease, affecting approximately 16% of the adult population worldwide. The chronic inflammation in the joint leads to the breakdown of cartilage, which leads to permanent pain and limitations in everyday life at an early stage of the disease. To date, there is no therapy that can interrupt the inflammatory state or reverse cartilage damage. The PROTO consortium (funded by the EU Horizon Europe program, Grant 101095635) aims to prevent the development of OA by correcting a pathological biomechanical pattern by a digital training intervention and to treat early stage OA with an innovative allogeneic cell therapy.

More and more evidences showed that cartilage harbored local progenitor cells that could differentiate toward osteoblast, chondrocyte, and adipocyte. However, our previous results showed that osteoarthritis derived chondroprogenitor cells (OA-CPC) exhibited strong osteogenic potential even in chondrogenic condition. How to promote their chondrogenic potential is the key for cartilage repair and regeneration in osteoarthritis. Recently, lipid availability was proved to determine skeletal progenitor fate. Therefore, we aim to determine whether lipid inhibition under 3D culture condition could enhance OA-CPC chondrogenesis. Moreover, glucose concentration was also evaluated for chondrogenic capacity. Although there are many researches showed that lower glucose promotes chondrogenesis, in our results, we found that OA-CPC in high concentration of glucose (4.5g/L) with lipid inhibitor (GW1100) showed strongest chondrogenic potential, which could form largest cell pellet with strong proteoglycan staining, COL II expression and no COL I expression. Besides, COL2A1 was increased and COL10A1 was decreased significantly by GW1100 under high glucose condition in 2D culture. Interestingly, although the expression level of MMP13 was not changed by GW1100 at RNA and protein level, less MMP13 protein secreted out of cell nuclear. In summary, we estimated that higher glucose and lower lipid supplies benefit OA-CPC chondrogenesis and cartilage repair.

3D accurate measurements of the skeletal structures of the foot, in physiological and impaired subjects, are now possible using Cone-Beam CT (CBCT) under real-world loading conditions. In detail, this feature allows a more realistic representation of the relative bone-bone interactions of the foot as they occur under patient-specific body weight conditions. In this context, varus/valgus of the hindfoot under altered conditions or the thinning of plantar tissues that occurs with advancing age are among the most complex and interesting to represent, and numerous measurement proposals have been proposed. This study aims to analyze and compare these measurements from CBCT in weight-bearing scans in a clinical population. Sixteen feet of diabetic patients and ten feet with severe adult flatfoot acquired before/after corrective surgery underwent CBCT scans (Carestream, USA) while standing on the leg of interest. Corresponding 3D shapes of each bone of the shank and hindfoot were reconstructed (Materialise, Belgium). Six different techniques found in the literature were used to calculate the varus/valgus deformity, i.e., the inclination of the hindfoot in the frontal plane of the shank, and the distance between the ground and the metatarsal heads was calculated along with different solutions for the identification of possible calcifications. Starting with an accurate 3D reconstruction of the skeletal structures of the foot, a wide range of measurements representing the same angle of hindfoot alignment were found, some of them very different from each other. Interesting correlations were found between metatarsal height and subject age, significant in diabetic feet for the fourth and fifth metatarsal bones. Finally, CBCT allows 3D assessment of foot deformities under loaded conditions. The observed traditional measurement differences and new measurement solutions suggest that clinicians should consider carefully the anatomical and functional concepts underlying measurement techniques when drawing clinical and surgical conclusions.

In relation to regenerative therapies in osteoarthritis and cartilage repair, mesenchymal stromal cells (MSCs) have immunomodulatory functions and influence macrophage behaviour. Macrophages exist as a spectrum of pro-(M1) and anti-(M2) inflammatory phenotypic subsets. In the context of cartilage repair, we investigated MSC-macrophage crosstalk, including specifically the priming of cartilage cells by macrophages to achieve a regenerative rather than fibrotic outcome. Human monocytes were isolated from blood cones and differentiated towards M1 and M2 macrophages. Monocytes (Mo), M1 and M2 macrophages were cultured directly and indirectly (trans-well system) with human bone marrow derived MSCs. MSCs were added during M1 polarisation and separately to already induced M1 cells. Outcomes (M1/M2 markers and ligands/receptors) were evaluated using RT-qPCR and flow cytometry. Influence on chondrogenesis was assessed by applying M1 and M2 macrophage conditioned media (CM) sequentially to cartilage derived cells (recapitulating an acute injury environment). RT-qPCR was used to evaluate chondrogenic/fibrogenic gene transcription. The ratio of M2 markers (CD206 or CD163) to M1 markers (CD38) increased when MSCs were added to Mo/M1 macrophages, regardless of culture system used (direct or indirect). Pro-inflammatory markers (including TNFβ) decreased. CXCR2 expression by both M1 macrophages and MSCs decreased when MSCs were added to differentiated M1 macrophages in transwell. When adding initially M1 CM (for 12 hours) followed by M2 CM (for 12 hours) sequentially to chondrocytes, there was a significant increase of Aggrecan and Collagen type 2 gene expression and decrease in fibroblastic cell surface markers (PDPN/CD90). Mo/M1 macrophages cultured with MSCs, directly or indirectly, are shifted towards a more M2 phenotype. Indirect culture suggests this effect can occur via soluble signaling mediators. Sequential exposure of M1CM followed by M2CM to chondrocytes resulted in increased chondrogenic and reduced fibrotic gene expression, suggesting that an acute pro-inflammatory stimulus may prime chondrocytes before repair.

The current procedures being applied in the clinical setting to address osteoporosis-related delayed union and nonunion bone fractures have been found to present mostly suboptimal outcomes. As a result, bone tissue engineering (BTE) solutions involving the development of implantable biomimetic scaffolds to replace damaged bone and support its regeneration are gaining interest. The piezoelectric properties of the bone tissue, which stem primarily from the significant presence of piezoelectric type I collagen fibrils in the tissue's extracellular matrix (ECM), play a key role in preserving the bone's homeostasis and provide integral assistance to the regeneration process. However, despite their significant potential, these properties of bone tend to be overlooked in most BTE-related studies. In order to bridge this gap in the literature, novel hydroxyapatite (HAp)-filled osteoinductive and piezoelectric poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-TrFE) electrospun nanofibers were developed to replicate the bone's fibrous ECM composition and electrical features. Different HAp nanoparticle concentrations (1–10%, wt%) were tested to assess their effect on the physicochemical and biological properties of the resulting fibers. The fabricated scaffolds displayed biomimetic collagen fibril-like diameters, while also presenting mechanical features akin to type I collagen. The increase in HAp presence was found to enhance both surface and piezoelectric properties of the fibers, with an improvement in scaffold wettability and increase in β-phase nucleation (translating to increased piezoelectricity) being observed. The HAp-containing scaffolds also exhibited an augmented bioactivity, with a more comprehensive surface mineralization of the fibers being obtained for the scaffolds with the highest HAp concentrations. Improved osteogenic differentiation of seeded human mesenchymal stem/stromal cells was achieved with the addition of HAp, as confirmed by an increased ALP activity, calcium deposition and upregulated expression of key osteogenic markers. Overall, our findings highlight, for the first time, the potential of combining PVDF-TrFE and HAp to develop electroactive and osteoinductive nanofibers for BTE.

Acknowledgements: The authors thank FCT for funding through the projects InSilico4OCReg (PTDC/EME-SIS/0838/2021), OptiBioScaffold (PTDC/EME-SIS/4446/2020) and BioMaterARISES (EXPL/CTM-CTM/0995/2021), the PhD scholarship (2022.10572.BD) and to the research institutions iBB (UIDB/04565/2020 and UIDP/04565/2020) and Associate Laboratory i4HB (LA/P/0140/2020).

Gait measurements can vary due to various intrinsic and extrinsic factors, and this variability becomes more pronounced using inertial sensors in a free-living environment. Therefore, identifying and quantifying the sources of variability is essential to ensure measurement reliability and maintain data quality.

This study aimed to determine the variability of daily accelerations recorded by an inertial sensor in a group of healthy individuals. Ten participants, four males and six females, with a mean age of 50 years (range: 29–61) and BMI of 26.9 kg/m² (range: 21.4–36.8), were included. A single accelerometer continuously recorded lower limb accelerations over two weeks. We extracted and analyzed the accelerations of three consecutive strides within walking bouts if the time difference between the bouts was more than two hours. Multivariate mixed-effects modeling was performed on both the discretized acceleration waveforms at 101 points (0–100) and the harmonics of the signals in the frequency domain to determine the variance components for different subjects, days, bouts, and steps as the random effect variables. Intraclass correlation coefficients (ICCs) were calculated for between-day, between-bout, and between-step comparisons.

The results showed that the ICCs for the between-day, between-bout, and between-step comparisons were 0.73, 0.82, 0.99 for the vertical axis; 0.64, 0.75, 0.99 for the anteroposterior axis; and 0.55, 0.96, 0.97 for the mediolateral axis. For the signal harmonics, the respective ICCs were 0.98, 0.98, 0.99 for the vertical axis; 0.54, 0.93, 0.98 for the anteroposterior axis; and 0.69, 0.78, 0.95 for the mediolateral axis.

Overall, this study demonstrated that accelerations recorded continuously for multiple days in a free-living environment exhibit high variability, mainly between days, and some variability arising from differences between walking bouts during different times within days. However, reliable and repeatable gait measurements can be obtained by identifying and quantifying the sources of variability.

The use of implant biomaterials for prosthetic reconstructive surgery and osteosynthesis is consolidated in the orthopaedic field, improving the quality of life of patients and allowing for healthy and better ageing. However, there is the lack of advanced innovative methods to investigate the potentialities of smart biomaterials, particularly for the study of local effects of implant and osteointegration. Despite the complex process of osseointegration is difficult to recreate in vitro, the growing challenges in developing alternative models require to set-up and validate new approaches. Aim of the present study is to evaluate an advanced in vitro tissue culture model of osteointegration of titanium implants in human trabecular bone. Cubic samples (1.5×1.5 cm) of trabecular bone were harvested as waste material from hip arthroplasty surgery (CE AVEC 829/2019/Sper/IOR); cylindrical defects (2 mm Ø, 6 mm length) were created, and tissue specimens assigned to the following groups: 1) empty defects- CTR-; 2) defects implanted with a cytotoxic copper pin (Merck cod. 326429)- CTR+; 3) defects implanted with standard titanium pins of 6 µm-rough (ZARE S.r.l) -Ti6. Tissue specimens were cultured in mini rotating bioreactors in standard conditions, weekly assessing viability. At the 8-week-timepoint, immunoenzymatic, microtomographic, histological and histomorphometric analyses were performed. The model was able to simulate the effects of implantation of the materials, showing a drop in viability in CTR+, differently from Ti6 which appears to have a trophic effect on the bone. MicroCT and histological analysis supported the results, with lower BV/TV and Tb.Th values observed in CTR- compared to CTR+ and Ti6 and signs of matrix and bone deposition at the implant site. The collected data suggest the reliability of the tested model which can recreate the osseointegration process in vitro and can therefore be used for preliminary evaluations to reduce and refine in vivo preclinical models.

Acknowledgment: This work was supported by Emilia-Romagna Region for the project “Sviluppo di modelli biologici in vitro ed in silico per la valutazione e predizione dell'osteointegrazione di dispositivi medici da impianto nel tessuto osseo”

Chronic low back pain (CLBP) is the most common cause of disability worldwide, and lumbar spine fusion (LSF) is often chosen to treat pain caused by advanced degenerative disease when clinical treatment failed certain cases, the post-surgical outcomes are not what was expected. Several studies highlight how important are. In psychological variables during the postoperative spine surgery period. The aim of this study is to assess the role of preoperative depression on postoperative clinical outcomes. We included patients who underwent LSF since December 2021. Preoperative depression was assessed administering Beck Depression Inventory questionnaire (BDI). And pain and disability were evaluated at 1, 3, and 6 months, administering respectively Visual Analogic Scale (VAS) and Oswestry Disability Index (ODI). As statistical analysis Mann-Whitney test was performed. We included 46 patients, 20 female (43,5%) and 26 male (56,5%) with an average age of 64,2. The population was divided in two groups, fixing the BDI cut-off point at 10. Patients with BDI < 10 points (N=28) had normal mental health status, instead patients with BDI > 10 points (N=16) had depressive disorders. At 3 months patients with healthy mental status reported statistically significant reduction of pain (U = 372,5, p = .006) and improvement of disability but without statistical significancy (U = 318, p = 0,137). At 6 months patients without psychological disease reported statistically significant reduction of pain (U = 342, p = 0,039) and disability (U = 372,5, p = 0,006).

This study demonstrates the correlation between pre-existing depressive state and poorer clinical outcomes after spine surgery. These results are consistent with the literature. Therefore, during the surgical decision making it is crucial to take psychological variables into account in order to predict the results after surgery and inform patients on the potential influence of mental status.

Spontaneous muscle regenerative potential is limited, as severe injuries incompletely recover and result in chronic inflammation. Current therapies are restricted to conservative management, not providing a complete restitutio ad integrum; therefore, alternative therapeutic strategies are welcome, such as cell-based therapies with stem cells or Peripheral Blood Mononuclear Cells (PBMCs). Here, we described two different in vitro myogenic models: a 2D perfused system and a 3D bioengineered scaffold within a perfusion bioreactor. Both models were assembled with human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and human primary skeletal myoblasts (hSkMs) to study induction and maintenance of myogenic phenotype in presence of PBMCs. When hBM-MSCs were cultured with human primary skeletal myoblasts (hSkMs) in medium supplemented with 10 ng/mL of bFGF; cells showed increased expression of myogenic-related gene, such as Desmin and Myosin Heavy Chain II (MYH2) after 21 days, and a prevalent expression of anti-inflammatory cytokines (IL10, 15-fold). Next, PBMCs were added in an upper transwell chamber and hBM-MSCs significantly upregulated myogenic genes throughout the culture period, while pro-inflammatory cytokines (e.g., IL12A) were downregulated. In 3D, hBM-MSCs plus hSkMs embedded in fibrin-based scaffolds, cultured in dynamic conditions, showed that all myogenic-related genes tended to be upregulated in the presence of PBMCs, and Desmin and MYH2 were also detected at protein level, while pro-inflammatory cytokine genes were significantly downregulated in the presence of PBMCs. In conclusion, our works suggest that hBM-MSCs have a versatile myogenic potential, enhanced and modulated by PMBCs. Moreover, our 3D biomimetic approach seemed to better resemble the tissue architecture allowing an efficient in vitro cellular cross-talk.

The aim of this scoping review is to understand the extent and type of evidence in relation to the use of guided growth for correcting rotational deformities of long bones. Guided growth is routinely used to correct angular deformities in long bones in children. It has also been proven to be a viable method to correct rotational deformities, but the concept is not yet fully examined. Databases searched include Medline, Embase, Cochrane Library, Web of Science and Google Scholar.

All identified citations were uploaded into Rayyan.ai and screened by at least two reviewers. The search resulted in 3569 hits. 14 studies were included: 1 review, 3 clinical trials and 10 pre-clinical trials. Clinical trials: a total of 21 children (32 femurs and 5 tibiae) were included. Surgical methods were 2 canulated screws connected by cable, PediPlates obliquely oriented, and separated Hinge Plates connected by FiberTape. Rotation was achieved in all but 1 child. Adverse effects reported include limb length discrepancy (LLD), knee stiffness and rebound of rotation after removal of tethers. 2 pre-clinical studies were ex-vivo studies, 1 using 8-plates on Sawbones and 1 using a novel z-shaped plates on human cadaver femurs. There were 5 lapine studies (2 using femoral plates, 2 using tibial plates and 1 using an external device on tibia), 1 ovine (external device on tibia), 1 bovine (screws and cable on metacarp) and a case-report on a dog that had an external device spanning from femur to tibia. Rotation was achieved in all studies. Adverse effects reported include implant extrusions, LLD, articular deformities, joint stiffness and rebound. All included studies conclude that guided growth is a viable treatment for rotational deformities of long bones, but there is great variation in models and surgical methods used, and in reported adverse effects.

Cell culture on tissue culture plastic (TCP) is widely used across biomedical research to understand the in vivo environment of a targeted biological system. However, growing evidence indicates that the characteristics of cells investigated in this way differ substantially from their characteristics in the human body. The limitations of TCP monolayer cell cultures are especially relevant for chondrocytes, the cell population responsible for producing cartilage matrix, because their zonal organization in hyaline cartilage is not preserved in a flattened monolayer assay. Here, we contrast the response of primary human chondrocytes to inflammatory cytokines, tumor necrosis factor-alpha and interferon-gamma, via transcriptional, translational, and histological profiling, when grown either on TCP or within a 3D cell pellet (scaffold-less). We focus on anti-apoptotic (Bcl2), pro-apoptotic (Bax, Mff, Fis1), and senescent (MMP13, MMP1, PCNA, p16, p21) markers. We find that the 3D environment of the chondrocyte has a profound effect on the behavior and fate of the cell; in TCP monolayer cultures, chondrocytes become anti-apoptotic and undergo senescence in response to inflammatory cytokines, whereas in 3D cell pellet cultures, they exhibit a pro-apoptotic response. Our findings demonstrate that chondrocyte culture environment plays a pivotal role in cell behavior, which has important implications for the clinical applicability of in vitro research of cartilage repair. Although there are practical advantages to 2D cell cultures, our data suggest researchers should be cautious when drawing conclusions if they intend to extrapolate findings to in vivo phenomena. Our data demonstrates opposing chondrocyte responses in relation to apoptosis and senescence, which appear to be solely reliant on the environment of the culture system. This biological observation highlights that proper experimental design is crucial to increase the clinical utility of cartilage repair experiments and streamline their translation to therapy development.

Our musculoskeletal system has a limited capacity for repair. This has led to increased interest in the development of tissue engineering and biofabrication strategies for the regeneration of musculoskeletal tissues such as bone, ligament, tendon, meniscus and articular cartilage. This talk will demonstrate how different musculoskeletal tissues, specifically cartilage, bone and osteochondral defects, can be repaired using emerging biofabrication and 3D bioprinting strategies. This will include examples from our lab where cells and/or growth factors are bioprinted into constructs that can be implanted directly into the body, to approaches where biomimetic tissues are first engineered in vitro before in vivo implantation. The efficacy of these different biofabrication strategies in different preclinical studies will be reviewed, and lessons from the relative successes and failures of these approaches to tissue regeneration will be discussed.