Impact of the COVID-19 pandemic on the productivity and career prospects of musculoskeletal researchers.

Academic researchers faced a multitude of challenges posed by the COVID-19 pandemic, including widespread shelter-in-place orders, workplace closures, and cessation of in-person meetings and laboratory activities. The extent to which these challenges impacted musculoskeletal researchers, specifically, is unknown. We developed an anonymous web-based survey to determine the pandemic's impact on research productivity and career prospects among musculoskeletal research trainees and faculty. There were 116 musculoskeletal (MSK) researchers with varying demographic backgrounds who completed the survey. Of respondents, 48.3% (n = 56) believed that musculoskeletal funding opportunities decreased because of COVID-19, with faculty members more likely to hold this belief compared to nonfaculty researchers (p = 0.008). Amongst MSK researchers, 88.8% (n = 103) reported research activity was limited by COVID-19, and 92.2% (n = 107) of researchers reported their research was not able to be refocused on COVID-19-related topics, with basic science researchers less likely to be able to refocus their research compared to clinical researchers (p = 0.030). Additionally, 47.4% (n = 55) reported a decrease in manuscript submissions since the onset of the pandemic. Amongst 51 trainee researchers, 62.8% (n = 32) reported a decrease in job satisfaction directly attributable to the COVID-19 pandemic. In summary, study findings indicated that MSK researchers struggled to overcome challenges imposed by the pandemic, reporting declines in funding opportunities, research productivity, and manuscript submission. Trainee researchers experienced significant disruptions to critical research activities and worsening job satisfaction. Our findings motivate future efforts to support trainees in developing their careers and target the recovery of MSK research from the pandemic stall.

Intradiscal inflammatory stimulation induces spinal pain behavior and intervertebral disc degeneration in vivo.

Degeneration of the intervertebral disc (IVD) results in a range of symptomatic (i.e., painful) and asymptomatic experiences. Components of the degenerative environment, including structural disruption and inflammatory cytokine production, often correlate with pain severity. However, the role of inflammation in the activation of pain and degenerative changes has been complex to delineate. The most common IVD injury model is puncture; however, it initiates structural damage that is not representative of the natural degenerative cascade. In this study, we utilized in vivo injection of lipopolysaccharide (LPS), a pro-inflammatory stimulus, into rat caudal IVDs using 33G needles to induce inflammatory activation without the physical tissue disruption caused by puncture using larger needles. LPS injection increased gene expression of pro-inflammatory cytokines (Tnfa, Il1b) and macrophage markers (Inos, Arg1), supported by immunostaining of macrophages (CD68, CCR7, Arg1) and systemic changes in blood cytokine and chemokine levels. Disruption of the IVD structural integrity after LPS injection was also evident through changes in histological grading, disc height, and ECM biochemistry. Ultimately, intradiscal inflammatory stimulation led to local mechanical hyperalgesia, demonstrating that pain can be initiated by inflammatory stimulation of the IVD. Gene expression of nociceptive markers (Ngf, Bdnf, Cgrp) and immunostaining for neuron ingrowth (PGP9.5) and sensitization (CGRP) in the IVD were also shown, suggesting a mechanism for the pain exhibited. To our knowledge, this rat IVD injury model is the first to demonstrate local pain behavior resulting from inflammatory stimulation of caudal IVDs. Future studies will examine the mechanistic contributions of inflammation in mediating pain.

Sex differences in the biomechanical and biochemical responses of caudal rat intervertebral discs to injury.

Background: Intervertebral disc degeneration (IDD) is a major cause of low back pain (LBP) worldwide. Sexual dimorphism, or sex-based differences, appear to exist in the severity of LBP. However, it is unknown if there are sex-based differences in the inflammatory, biomechanical, biochemical, and histological responses of intervertebral discs (IVDs). Methods: Caudal (Coccygeal/Co) bone-disc-bone motion segments were isolated from multiple spinal levels (Co8 to Co14) of male and female Sprague-Dawley rats. Changes in motion segment biomechanics and extracellular matrix (ECM) biochemistry (glycosaminoglycan [GAG], collagen [COL], water, and DNA content) were evaluated at baseline and in response to chemical insult (lipopolysaccharide [LPS]) or puncture injury ex vivo. We also investigated the contributions of Toll-like receptor (TLR4) signaling on responses to LPS or puncture injury ex vivo, using a small molecule TLR4 inhibitor, TAK-242. Results: Findings indicate that IVD motion segments from female donors had greater nitric oxide (NO) release in LPS groups compared to male donors. HMGB1 release was increased in punctured discs, but not LPS injured discs, with no sex effect. Although both male and female discs exhibited reductions in dynamic moduli in response to LPS and puncture injuries, dynamic moduli from female donors were higher than male donors across all groups. In uninjured (baseline) samples, a significant sex effect was observed in nucleus pulposus (NP) DNA and water content. Female annulus fibrosus (AF) also had higher DNA, GAG, and COL content (normalized by dry weight), but lower water content than male AF. Additional injury- and sex-dependent effects were observed in AF GAG/DNA and COL/DNA content. Finally, TAK-242 improved the dynamic modulus of female but not male punctured discs. Conclusions: Our findings demonstrate that there are differences in rat IVD motion segments based on sex, and that the response to injury in inflammatory, biomechanical, biochemical, and histological outcomes also exhibit sex differences. TLR4 inhibition protected against loss of mechanical integrity of puncture-injured IVD motion segments, with differences responses based on donor sex.

An in vivo model of ligamentum flavum hypertrophy from early-stage inflammation to fibrosis.

Multi-joint disease pathologies in the lumbar spine, including ligamentum flavum (LF) hypertrophy and intervertebral disc (IVD) bulging or herniation contribute to lumbar spinal stenosis (LSS), a highly prevalent condition characterized by symptomatic narrowing of the spinal canal. Clinical hypertrophic LF is characterized by a loss of elastic fibers and increase in collagen fibers, resulting in fibrotic thickening and scar formation. In this study, we created an injury model to test the hypothesis that LF needle scrape injury in the rat will result in hypertrophy of the LF characterized by altered tissue geometry, matrix organization, composition and inflammation. An initial pilot study was conducted to evaluate effect of needle size. Results indicate that LF needle scrape injury using a 22G needle produced upregulation of the pro-inflammatory cytokine Il6 at 1 week post injury, and increased expression of Ctgf and Tgfb1 at 8 weeks post injury, along with persistent presence of infiltrating macrophages at 1, 3, and 8 weeks post injury. LF integrity was also altered, evidenced by increases in LF tissue thickness and loss of elastic tissue by 8 weeks post injury. Persistent LF injury also produced multi-joint effects in the lumbar IVD, including disc height loss at the injury and adjacent to injury level, with degenerative IVD changes observed in the adjacent level. These results demonstrate that LF scrape injury in the rat produces structural and molecular features of LF hypertrophy and IVD height and histological changes, dependent on level. This model may be useful for testing of therapeutic interventions for treatment of LSS and IVD degeneration associated with LF hypertrophy.

Nuclear Factor Kappa B Over-Activation in the Intervertebral Disc Leads to Macrophage Recruitment and Severe Disc Degeneration.

Objective: Low back pain (LBP) is the leading cause of global disability and is thought to be driven primarily by intervertebral disc (IVD) degeneration (DD). Persistent upregulation of catabolic enzymes and inflammatory mediators have been associated with severe cases of DD. Nuclear factor kappa B (NF-κB) is a master transcription regulator of immune responses and is over expressed during inflammatory-driven musculoskeletal diseases, including DD. However, its role in triggering DD is unknown. Therefore, this study investigated the effect of NF-κB pathway over-activation on IVD integrity and DD pathology. Methods: Using skeletally mature mouse model, we genetically targeted IVD cells for canonical NF-κB pathway activation via expression of a constitutively active form of inhibitor of κB kinase B (IKKß), and assessed changes in IVD cellularity, structural integrity including histology, disc height, and extracellular matrix (ECM) biochemistry, biomechanics, expression of inflammatory, catabolic, and neurotropic mediators, and changes in macrophage subsets, longitudinally up to 6-months post activation. Results: Prolonged NF-κB activation led to severe structural degeneration, with a loss of glycosaminoglycan (GAG) content and complete loss of nucleus pulposus (NP) cellularity. Structural and compositional changes decreased IVD height and compressive mechanical properties with prolonged NF-κB activation. These alterations were accompanied by increases in gene expression of inflammatory molecules ( Il1b, Il6, Nos2 ), chemokines ( Mcp1 , Mif ), catabolic enzymes ( Mmp3, Mmp9, Adamts4 ), and neurotrophic factors ( Bdnf , Ngf ) within IVD tissue. Increased recruitment of activated F4/80 + macrophages exhibited a greater abundance of pro-inflammatory (CD38 + ) over inflammatory-resolving (CD206 + ) macrophage subsets in the IVD, with temporal changes in the relative abundance of macrophage subsets over time, providing evidence for temporal regulation of macrophage polarization in DD in vivo, where macrophages participate in resolving the inflammatory cascade but promote fibrotic transformation of the IVD matrix. We further show that NF-κB driven secretory factors from IVD cells increase macrophage migration and inflammatory activation, and that the secretome of inflammatory-resolving macrophages mitigates effects of NF-κB overactivation. Conclusion: Overall the observed results suggest prolonged NF-κB activation can induce severe DD, acting through increases in inflammatory cytokines, chemotactic proteins, catabolic enzymes, and the recruitment and inflammatory activation of a macrophage cell populations, that can be mitigated with inflammatory-resolving macrophage secretome.

Bullying, harassment, and discrimination of musculoskeletal researchers and the impact of the COVID-19 pandemic: an international study.

PURPOSE: Bullying, harassment, and discrimination (BHD) are prevalent in academic, scientific, and clinical departments, particularly orthopedic surgery, and can have lasting effects on victims. As it is unclear how BHD affects musculoskeletal (MSK) researchers, the following study assessed BHD in the MSK research community and whether the COVID-19 pandemic, which caused hardships in other industries, had an impact. METHODS: A web-based anonymous survey was developed in English by ORS Spine Section members to assess the impact of COVID-19 on MSK researchers in North America, Europe, and Asia, which included questions to evaluate the personal experience of researchers regarding BHD. RESULTS: 116 MSK researchers completed the survey. Of respondents, 34.5% (n = 40) focused on spine, 30.2% (n = 35) had multiple areas of interest, and 35.3% (n = 41) represented other areas of MSK research. BHD was observed by 26.7% (n = 31) of respondents and personally experienced by 11.2% (n = 13), with mid-career faculty both observing and experiencing the most BHD. Most who experienced BHD (53.8%, n = 7) experienced multiple forms. 32.8% (n = 38) of respondents were not able to speak out about BHD without fear of repercussions, with 13.8% (n = 16) being unsure about this. Of those who observed BHD, 54.8% (n = 17) noted that the COVID-19 pandemic had no impact on their observations. CONCLUSIONS: To our knowledge, this is the first study to address the prevalence and determinants of BHD among MSK researchers. MSK researchers experienced and observed BHD, while many were not comfortable reporting and discussing violations to their institution. The COVID-19 pandemic had mixed-effects on BHD. Awareness and proactive policy changes may be warranted to reduce/eliminate the occurrence of BHD in this community.

Blocking toll-like receptor 4 mitigates static loading induced pro-inflammatory expression in intervertebral disc motion segments.

While the anabolic effects of mechanical loading on the intervertebral disc (IVD) have been extensively studied, inflammatory responses to loading have not been as well characterized. Recent studies have highlighted a significant role of innate immune activation, particularly that of toll-like receptors (TLRs), in IVD degeneration. Biological responses of intervertebral disc cells to loading depend on many factors that include magnitude and frequency. The goals of this study were to characterize the inflammatory signaling changes in response to static and dynamic loading of IVD and investigate the contributions of TLR4 signaling in response to mechanical loading. Rat bone-disc-bone motion segments were loaded for 3 hr under a static load (20 % strain, 0 Hz) with or without an additional low-dynamic (4 % dynamic strain, 0.5 Hz) or high-dynamic (8 % dynamic strain, 3 Hz) strain, and results were compared to unloaded controls. Some samples were also loaded with or without TAK-242, an inhibitor of TLR4 signaling. The magnitude of NO release into the loading media (LM) was correlated with the applied frequency and strain magnitudes across different loading groups. Injurious loading profiles, such as static and high-dynamic, significantly increased Tlr4 and Hmgb1 expression while this result was not observed in the more physiologically relevant low-dynamic loading group. TAK-242 co-treatment decreased pro-inflammatory expression in static but not dynamic loaded groups, suggesting that TLR4 plays a direct role in mediating inflammatory responses of IVD to static compression. Overall, the microenvironment induced by dynamic loading diminished the protective effects of the TAK-242, suggesting that TLR4 plays a direct role in mediating inflammatory responses of IVD to static loading injury.

Harmonization and standardization of nucleus pulposus cell extraction and culture methods.

Background: In vitro studies using nucleus pulposus (NP) cells are commonly used to investigate disc cell biology and pathogenesis, or to aid in the development of new therapies. However, lab-to-lab variability jeopardizes the much-needed progress in the field. Here, an international group of spine scientists collaborated to standardize extraction and expansion techniques for NP cells to reduce variability, improve comparability between labs and improve utilization of funding and resources. Methods: The most commonly applied methods for NP cell extraction, expansion, and re-differentiation were identified using a questionnaire to research groups worldwide. NP cell extraction methods from rat, rabbit, pig, dog, cow, and human NP tissue were experimentally assessed. Expansion and re-differentiation media and techniques were also investigated. Results: Recommended protocols are provided for extraction, expansion, and re-differentiation of NP cells from common species utilized for NP cell culture. Conclusions: This international, multilab and multispecies study identified cell extraction methods for greater cell yield and fewer gene expression changes by applying species-specific pronase usage, 60-100 U/ml collagenase for shorter durations. Recommendations for NP cell expansion, passage number, and many factors driving successful cell culture in different species are also addressed to support harmonization, rigor, and cross-lab comparisons on NP cells worldwide.

Toward defining the role of the synovium in mitigating normal articular cartilage wear and tear.

Cartilage repair has been studied extensively in the context of injury and disease, but the joint's management of regular sub-injurious damage to cartilage, or 'wear and tear,' which occurs due to normal activity, is poorly understood. We hypothesize that this cartilage maintenance is mediated in part by cells derived from the synovium that migrate to the worn articular surface. Here, we demonstrate in vitro that the early steps required for such a process can occur. First, we show that under physiologic mechanical loads, chondrocyte death occurs in the cartilage superficial zone along with changes to the cartilage surface topography. Second, we show that synoviocytes are released from the synovial lining under physiologic loads and attach to worn cartilage. Third, we show that synoviocytes parachuted onto a simulated or native cartilage surface will modify their behavior. Specifically, we show that synoviocyte interactions with chondrocytes lead to changes in synoviocyte mechanosensitivity, and we demonstrate that cartilage-attached synoviocytes can express COL2A1, a hallmark of the chondrogenic phenotype. Our findings suggest that synoviocyte-mediated repair of cartilage 'wear and tear' as a component of joint homeostasis is feasible and is deserving of future study.

Controversies in spine research: Organ culture versus in vivo models for studies of the intervertebral disc.

Intervertebral disc degeneration is a common cause of low back pain, the leading cause of disability worldwide. Appropriate preclinical models for intervertebral disc research are essential to achieving a better understanding of underlying pathophysiology and for the development, evaluation, and translation of more effective treatments. To this end, in vivo animal and ex vivo organ culture models are both widely used by spine researchers; however, the relative strengths and weaknesses of these two approaches are a source of ongoing controversy. In this article, members from the Spine and Preclinical Models Sections of the Orthopedic Research Society, including experts in both basic and translational spine research, present contrasting arguments in support of in vivo animal models versus ex vivo organ culture models for studies of the disc, supported by a comprehensive review of the relevant literature. The objective is to provide a deeper understanding of the respective advantages and limitations of these approaches, and advance the field toward a consensus with respect to appropriate model selection and implementation. We conclude that complementary use of several model types and leveraging the unique advantages of each is likely to result in the highest impact research in most instances.

Race, But Not Gender, Is Associated With Admissions Into Orthopaedic Residency Programs.

BACKGROUND: Orthopaedic surgery is one of the most competitive but least diverse surgical specialties, with ever-increasing academic achievements (such as test scores) shown by applicants. Prior research shows that white applicants had higher United States Medical Licensing Exam (USMLE) Step 1 and Step 2 Clinical Knowledge scores as well as higher odds of Alpha Omega Alpha status compared with Black, Hispanic, and other applicant groups. Yet, it still remains unknown whether differences in application metrics by race/ethnicity sufficiently explain the underrepresentation of certain racial or ethnic minority groups in orthopaedic residency programs. QUESTIONS/PURPOSES: In this study, we sought to determine (1) the relative weight of academic variables for admission into orthopaedic residency, and (2) whether race and gender are independently associated with admission into an orthopedic residency. METHODS: The Electronic Residency Application System (ERAS) data from the Association of American Medical Colleges (AAMC) and the National Board of Medical Examiners (NBME) of first-time MD applicants (n = 8966) for orthopaedic surgery residency positions in the United States and of admitted orthopaedic residents (n = 6218) from 2005 to 2014 were reviewed. This dataset is the first and most comprehensive of its kind to date in orthopaedic surgery. Academic metrics, such as USMLE Step 1 and Step 2 Clinical Knowledge scores, number of publications, Alpha Omega Alpha status, volunteer experiences, work experience, as well as race and gender, were analyzed using hierarchical logistic regression models. The first model analyzed the association of academic metrics with admission into orthopaedic residency. In the second model, we added race and gender and controlled for metrics of academic performance. To determine how well the models simulated the actual admissions data, we computed the receiver operating characteristics (ROC) including the area under curve (AUC), which measures the model's ability to simulate which applicants were admitted or not admitted, with an AUC = 1.0 representing a perfect simulation. The odds ratio and confidence interval of each variable were computed. RESULTS: When only academic variables were analyzed in the first model, Alpha Omega Alpha status (odds ratio 2.12 [95% CI 1.80 to 2.50]; p < 0.001), the USMLE Step 1 score (OR 1.04 [95% CI 1.03 to 1.04]; p < 0.001), the USMLE Step 2 Clinical Knowledge score (OR 1.01 [95% CI 1.01 to 1.02]; p < 0.001), publication count (OR 1.04 [95% CI 1.03 to 1.05]; p < 0.001), and volunteer experience (OR 1.03 [95% CI 1.01 to 1.04]; p < 0.001) were associated with admissions into orthopaedics while work and research experience were not. This model yielded a good prediction of the results with an AUC of 0.755. The second model, in which the variables of race and gender were added to the academic variables, also had a good prediction of the results with an AUC of 0.759. This model indicates that applicant race, but not gender, is associated with admissions into orthopaedic residency. Applicants from Asian (OR 0.78 [95% CI 0.67 to 0.92]), Black (OR 0.63 [95% CI 0.51 to 0.77], Hispanic (OR 0.48 [95% CI 0.36 to 0.65]), or other race groups (OR 0.65 [95% CI 0.55 to 0.77]) had lower odds of admission into residency compared with white applicants. CONCLUSION: Minority applicants, but not women, have lower odds of admission into orthopaedic surgery residency, even when accounting for academic performance metrics. Changes in the residency selection processes are needed to eliminate the lower admission probability of qualified minority applicants in orthopaedic residency and to improve the diversity and inclusion of orthopaedic surgery. Changes including increasing the diversity of the selection committee, bias training, blinding applications before review, removal of metrics with history of racial disparities from an interviewer's candidate profile before an interview, and use of holistic application review (where an applicants' experiences, attributes, and academic metrics are all considered) can improve the diversity landscape in training. In addition, cultivating an environment of inclusion will be necessary to address these long-standing trends in orthopaedic surgery. CLINICAL RELEVANCE: Race, but not gender, is associated with the odds of acceptance into orthopaedic surgery residency despite equivalent academic metrics. Changes in residency selection processes are suggested to eliminate the lower admission probability of qualified minority applicants into orthopaedic residency and to improve the diversity and inclusion of orthopaedic surgery.

Transient neonatal shoulder paralysis causes early osteoarthritis in a mouse model.

Neonatal brachial plexus palsy (NBPP) occurs in approximately 1.5 of every 1,000 live births. The majority of children with NBPP recover function of the shoulder. However, the long-term risk of osteoarthritis (OA) in this population is unknown. The purpose of this study was to investigate the development of OA in a mouse model of transient neonatal shoulder paralysis. Neonatal mice were injected twice per week for 4 weeks with saline in the right supraspinatus muscle (Saline, control) and botulinum toxin A (BtxA, transient paralysis) in the left supraspinatus muscle, and then allowed to recover for 20 or 36 weeks. Control mice received no injections, and all mice were sacrificed at 24 or 40 weeks. BtxA mice exhibited abnormalities in gait compared to controls through 10 weeks of age, but these differences did not persist into adulthood. BtxA shoulders had decreased bone volume (-9%) and abnormal trabecular microstructure compared to controls. Histomorphometry analysis demonstrated that BtxA shoulders had higher murine shoulder arthritis scale scores (+30%), and therefore more shoulder OA compared to controls. Articular cartilage of BtxA shoulders demonstrated stiffening of the tissue. Compared with controls, articular cartilage from BtxA shoulders had 2-fold and 10-fold decreases in Dkk1 and BMP2 expression, respectively, and 3-fold and 14-fold increases in Col10A1 and BGLAP expression, respectively, consistent with established models of OA. In summary, a brief period of paralysis of the neonatal mouse shoulder was sufficient to generate early signs of OA in adult cartilage and bone.

Three-Dimensional-Printed Flexible Scaffolds Have Tunable Biomimetic Mechanical Properties for Intervertebral Disc Tissue Engineering.

The intervertebral disc (IVD) exhibits complex structure and biomechanical function, which supports the weight of the body and permits motion. Surgical treatments for IVD degeneration (e.g., lumbar fusion, disc replacement) often disrupt the mechanical environment of the spine which lead to adjacent segment disease. Alternatively, disc tissue engineering strategies, where cell-seeded hydrogels or fibrous biomaterials are cultured in vitro to promote matrix deposition, do not recapitulate the complex IVD mechanical properties. In this study, we use 3D printing of flexible polylactic acid (FPLA) to fabricate a viscoelastic scaffold with tunable biomimetic mechanics for whole spine motion segment applications. We optimized the mechanical properties of the scaffolds for equilibrium and dynamic moduli in compression and tension by varying fiber spacing or porosity, generating scaffolds with de novo mechanical properties within the physiological range of spine motion segments. The biodegradation analysis of the 3D printed scaffolds showed that FPLA exhibits lower degradation rate and thus has longer mechanical stability than standard PLA. FPLA scaffolds were biocompatible, supporting viability of nucleus pulposus (NP) cells in 2D and in FPLA+hydrogel composites. Composite scaffolds cultured with NP cells maintained baseline physiological mechanical properties and promoted matrix deposition up to 8 weeks in culture. Mesenchymal stromal cells (MSCs) cultured on FPLA adhered to the scaffold and exhibited fibrocartilaginous differentiation. These results demonstrate for the first time that 3D printed FPLA scaffolds have de novo viscoelastic mechanical properties that match the native IVD motion segment in both tension and compression and have the potential to be used as a mechanically stable and biocompatible biomaterial for engineered disc replacement.

Oral Administration of a Chemically Modified Curcumin, TRB-N0224, Reduced Inflammatory Cytokines and Cartilage Erosion in a Rabbit ACL Transection Injury Model.

OBJECTIVE: To evaluate the effects of TRB-N0224, a chemically modified curcumin (CMC) with zinc binding properties and improved pharmacokinetics, in a rabbit anterior cruciate ligament (ACL) transection injury-induced model of osteoarthritis (OA). DESIGN: Thirty-eight skeletally mature New Zealand white rabbits were studied in 4 groups: a sham with arthrotomy (n = 6), control with ACL transection (n = 6), and 2 treatment groups with ACL transection and administration of TRB-N0224 at low (25 mg/kg/day) (n = 13) and high (50 mg/kg/day) (n = 13) doses. After euthanization at 12 weeks, outcomes were measured by post-necropsy gross morphology, biomechanics, and cartilage and synovium histology. Rabbit blood ELISA quantified cytokine and matrix metalloproteinase (MMP) concentrations at 0, 4, 8, and 12 weeks. RESULTS: Both treatment doses had fewer distal femoral condyle erosive defects than the control; the low dose demonstrated a mean 78% decrease (P < 0.01). Histologically, the low- and high-dose treatment groups had fewer cartilage pathologic changes and less severe synovitis than the control. CMC alone did not have a major effect on the biomechanics of healthy cartilage or cartilage in the ACL transection model, as demonstrated in 5 of the 6 measured properties/regions (P < 0.05). ELISA results suggested that the key mediators of OA, (interleukin) IL-1ß, IL-6, TNFα (tumor necrosis factor-α), MMP-9, and MMP-13, had decreased concentrations with TRB-N0224 treatment at different time points between weeks 4 to 12 (P < 0.05). CONCLUSIONS: In the pathogenesis of OA, an imbalance exists between catabolic and anabolic mediators. These results suggest the potential of TRB-N0224 to modulate MMP and cytokine levels, slowing the macroscopic and histopathological progression of OA.

Actomyosin contractility confers mechanoprotection against TNFα-induced disruption of the intervertebral disc.

Inflammation triggers degradation of intervertebral disc extracellular matrix (ECM), a hallmark of disc degeneration that contributes to back pain. Mechanosensitive nucleus pulposus cells are responsible for ECM production, yet the impact of a proinflammatory microenvironment on cell mechanobiology is unknown. Using gain- and loss-of-function approaches, we show that tumor necrosis factor-α (TNFα)-induced inflammation alters cell morphology and biophysical properties (circularity, contractility, cell stiffness, and hydraulic permeability) in a mechanism dependent on actomyosin contractility in a three-dimensional (3D) culture. We found that RhoA activation rescued cells from TNFα-induced mechanobiological disruption. Using a novel explant-in-hydrogel culture system, we demonstrate that nuclear factor kappa-B nuclear translocation and transcription are mechanosensitive, and its downstream effects on ECM degradation are regulated by actomyosin contractility. Results define a scaling relationship between circularity, contractility, and hydraulic permeability that is conserved from healthy to inflammatory microenvironments and is indicative of cell mechanobiological control across scales in 3D.

Avidin grafted dextran nanostructure enables a month-long intra-discal retention.

Low back pain is often the direct result of degeneration of the intervertebral disc. A wide range of therapeutics including anti-catabolic, pro-anabolic factors and chemo-attractants that can stimulate resident cells and recruit endogenous progenitors are under consideration. The avascular nature and the dense matrix of this tissue make it challenging for systemically administered drugs to reach their target cells inside the nucleus pulposus (NP), the central gelatinous region of the intervertebral disc (IVD). Therefore, local intra-discal injection of therapeutic drugs directly into the NP is a clinically relevant delivery approach, however, suffers from rapid and wide diffusion outside the injection site resulting in short lived benefits while causing systemic toxicity. NP has a high negative fixed charge density due to the presence of negatively charged aggrecan glycosaminoglycans that provide swelling pressures, compressive stiffness and hydration to the tissue. This negative fixed charge density can also be used for enhancing intra-NP residence time of therapeutic drugs. Here we design positively charged Avidin grafted branched Dextran nanostructures that utilize long-range binding effects of electrostatic interactions to bind with the intra-NP negatively charged groups. The binding is strong enough to enable a month-long retention of cationic nanostructures within the NP following intra-discal administration, yet weak and reversible to allow movement to reach cells dispersed throughout the tissue. The branched carrier has multiple sites for drug conjugation and can reduce the need for multiple injections of high drug doses and minimize associated side-effects, paving the way for effective clinical translation of potential therapeutics for treatment of low back pain and disc degeneration.

Confocal scanning of intervertebral disc cells in 3D: Inside alginate beads and in native microenvironment.

The interaction between cells and their extracellular matrix (ECM) is crucial to maintain both tissue and cellular homeostasis. Indeed, cell phenotype is significantly affected by the 3D microenvironment. Although highly convenient, isolating cells from the intervertebral disc (IVD) and growing them in 2D on plastic or glass substrates, causes them to rapidly lose their phenotype and consequently alter their gene and protein expression. While characterization of cells in their native or simulated 3D environment is preferred, such approaches are complexed by limitations in phenotypic readouts. In the current article, we describe a detailed protocol to study nucleus pulposus cells in 3D-embedded in alginate as a permeable cell-staining reservoir, as well as adaptation for cell staining and imaging in their native ECM. This method allows for detection of phenotypical and cytoskeletal changes in cells within native tissue or 3D alginate beads using confocal microscopy, without the need for histological processing.

Correction to: Translating Mechanobiology to the Clinic: A Panel Discussion from the 2018 CMBE Conference.

[This corrects the article DOI: 10.1007/s12195-018-0556-5.].

Academic Metrics Do Not Explain the Underrepresentation of Women in Orthopaedic Training Programs.

BACKGROUND: Among medical specialties, orthopaedic surgery persistently has one of the lowest representations of women in residency programs. This study examined whether differences exist in the academic metrics of the orthopaedic residency applicants and enrolled candidates by sex, which may be contributing to the persistent underrepresentation of women. Differences in enrollment rate in orthopaedic residency programs also were analyzed. We hypothesized that academic metrics were similar for female and male applicants and thus do not explain the underrepresentation of women in training programs. METHODS: Academic data of first-time applicants (n = 9,133) and candidates who enrolled in an orthopaedic residency (n = 6,381) in the U.S. from 2005 to 2014 were reviewed. The United States Medical Licensing Examination (USMLE) Step-1 and Step-2 Clinical Knowledge (CK) scores, Alpha Omega Alpha (AΩA) Honor Medical Society status, number of publications, and volunteer experiences were compared by sex and were analyzed over time. RESULTS: From 2005 to 2014, representation of female applicants increased from 12.6% to 16.0%, corresponding with an increase in the percentage of enrolled female residents (from 12.9% to 16.1%); 70.3% of male and 67.1% of female applicants to orthopaedic residency enrolled as residents (p = 0.082). Mean academic metrics increased significantly over time for applicants and enrolled candidates, irrespective of sex. Comparing by sex, the mean USMLE Step-1 scores of male applicants and enrolled candidates were approximately 2% higher than those of female applicants (p < 0.0001). Volunteer experiences of female applicants and enrolled candidates were 12% higher compared with male applicants (p < 0.0001). There was no significant difference in USMLE Step-2 CK scores, number of publications, or AΩA status by sex. CONCLUSIONS: The enrollment rate of male and female applicants in orthopaedic residencies was similar and did not change during the 10-year study period. The academic metrics of applicants and enrolled candidates have increased significantly. The academic metrics were found to be comparable by sex; the differences in USMLE Step-1 scores and volunteer experiences were small relative to the magnitude of accomplishments that these values represent. The growth rate of the proportion of women in orthopaedic residencies lags other surgical subspecialties but appears to be independent of academic metrics.

Underrepresented Minority Applicants Are Competitive for Orthopaedic Surgery Residency Programs, but Enter Residency at Lower Rates.

INTRODUCTION: Orthopaedic surgery residency programs have the lowest representation of ethnic/racial minorities compared with other specialties. This study compared orthopaedic residency enrollment rates and academic metrics of applicants and matriculated residents by race/ethnicity. METHODS: Data on applicants from US medical schools for orthopaedic residency and residents were analyzed from 2005 to 2014 and compared between race/ethnic groups (White, Asian, Black, Hispanic, and Other). RESULTS: Minority applicants comprised 29% of applicants and 25% of enrolled candidates. Sixty-one percent of minority applicants were accepted into an orthopaedic residency versus 73% of White applicants (P < 0.0001). White and Asian applicants and residents had higher USMLE Step 1. White applicants and matriculated candidates had higher Step 2 Clinical Knowledge scores and higher odds of Alpha Omega Alpha membership compared with Black, Hispanic, and Other groups. Publication counts were similar in all applicant groups, although Hispanic residents had significantly more publications. Black applicants had more volunteer experiences. CONCLUSIONS: In orthopaedic surgery residency, minority applicants enrolled at a lower rate than White and Asian applicants. The emphasis on USMLE test scores and Alpha Omega Alpha membership may contribute to the lower enrollment rate of minority applicants. Other factors such as conscious or unconscious bias, which may contribute, were not evaluated in this study.