Tibial Growth Plate Research Articles

Lower limb deformities and limb length discrepancies in hereditary multiple exostoses.

There is a high rate of lower limb deformity and limb length discrepancy in patients with hereditary multiple exostoses (HME). The aim of this study was to evaluate the type and frequency of lower limbs axial deviation and limb length discrepancy and the type of exostoses being risk factors for theses deformities. We retrospectively reviewed standing full-length radiograph of 32 HME patients (64 limbs) followed in our institution between October 2009 and December 2020. Patient demographics were recorded. Radiographic analysis of the coronal limb alignment was performed, limb length discrepancy was measured and topography of the exostoses was recorded. We propose a classification of lower legs in 2 groups and 4 types according to the presence and the location of exostoses. In group I, there is an intertibio- fibular exostose with fibular origin at the level of the tibiofibular joints. In type IA, at the level of the distal tibiofibular joint with ascension of the distal fibula; in type IB at the level of the proximal tibiofibular joint with a bracketing effect on the proximal tibia and a lateral slope of the proximal tibial growth plate; the type IC is combining features of both IA and IB. In group II, there is no intertibio-fibular exostose coming from the fibula and no growth abnormality is obvious. A clinically notable lower limb discrepancy (LLD) of ≥2 cm was found in 19% of our patients. Approximately 33% of patients had a knee valgus deformity and 44% had an ankle valgus deformity. The knee valgus deformity was due to fibular growth anomalies and not to distal femur anomalies. The majority of lower legs had fibular growth anomalies (72%) which was a significant risk factor for knee valgus deformity and leg length discrepancy. On the contrary, we found no correlation between number, location and volume of distal femoral exostoses and genu valgum nor leg length discrepancy. Presence of intertibio-fibular exostoses is a risk factor for knee valgus deformity and leg length discrepancy. The presence of these exostoses should lead to a close follow-up of the patient.

The heterogeneous mechanical properties of adolescent growth plate cartilage: A study in rabbit

The growth plate is a cartilaginous tissue that functions to lengthen bones in children. When fractured, however, the growth plate can lose this critical function. Our understanding of growth plate fracture and mechanobiology is currently hindered by sparse information on the growth plate’s microscale spatial gradients in mechanical properties. In this study, we performed microindentation across the proximal tibia growth plate of 9-week-old New Zealand White rabbits (n = 15) to characterize spatial variations in mechanical properties using linear elastic and nonlinear poroelastic material models. Mean indentation results for Hertz reduced modulus ranged from 380 to 690 kPa, with a peak in the upper hypertrophic zone and significant differences (p < 0.05) between neighboring zones. Using a subset of these animals (n = 7), we characterized zonal structure and extracellular matrix content of the growth plate through confocal fluorescent microscopy and Raman spectroscopy mapping. Comparison between mechanical properties and matrix content across the growth plate showed that proteoglycan content correlated with compressive modulus. This study is the first to measure poroelastic mechanical properties from microindentation across growth plate cartilage and to discern differing mechanical properties between the upper and lower hypertrophic zones. This latter finding may explain the location of typical growth plate fractures. The spatial variation in our reported mechanical properties emphasize the heterogeneous structure of the growth plate which is important to inform future regenerative implant design and mechanobiological models.

Rebound predictors of varus-valgus deformities around the knee corrected by guided growth.

Coronal plane deformities around the knee are rather common condition in children. Guided growth by temporary hemiepiphysiodesis is considered to be the preferred primary treatment in many cases. Despite the popularity of hemiepiphysiodesis, the incidence of recurrence of deformity and predictors for rebound are not well defined. The objectives of this study were to determine the incidence of the recurrence of varus-valgus deformities around the knee treated by temporary hemiepiphysiodesis and possible predictors for the rebound. We retrospectively reviewed medical records and x-ray images of 130 patients with varus-valgus deformities around the knee treated by tension-band (eight-plate) hemiepiphysiodesis, between the years 2006 and 2016 in our institution. The incidence of rebound of varus-valgus deformities around the knee and possible predictors were analyzed. Rebound of the deformity was observed in 10% of patients. Risk factors found to be in correlation with recurrence include young age, deformity of proximal tibia, proximal tibial medial growth plate beaking, and comorbidities (like metabolic disorders, multiple hereditary exostoses and genetic syndromes). The results of this study show that there is a noteworthy incidence of rebound in patients treated by temporary hemiepiphysiodesis for coronal deformities around the knee. The risk factors are also outlined. These patients, especially the ones with risk factors, require close surveillance until maturity. Level III-Case control study.

Напружено-деформований стан проксимального відділу великогомілкової кістки дитини при tibia vara в умовах однобічного блокування проксимальної росткової зони фіксаторами різних типів

Актуальність. Сучасним стандартом хірургічного лікування фронтальних епіметафізарних деформацій колінного суглоба у дітей є метод керованого росту. Для тимчасового блокування росткової зони використовуються різні фіксатори: скоби Блаунта, пластини з гвинтами. Проте дослідження, присвячені вивченню напружено-деформованого стану при використанні зазначених фіксаторів, відсутні.Мета: дослідження напружено-деформованого стану моделі проксимального відділу великогомілкової кістки дитини при однобічному блокуванні росткової зони фіксаторами різних типів в умовах навантажень, характерних для tibia vara.Матеріали і методи. За допомогою програми Solid Works створена і проаналізована методом кінцевих елементів 3D-модель проксимального відділу великогомілкової кістки дитини з латеральним блокуванням одним із 3 фіксаторів: скоба Блаунта, блокована пластина, стандартна пластина в умовах навантаження, характерних для tibia vara.Результати. В умовах навантаження, характерних для tibia vara, відзначено збільшення напружень у медіальній частині росткової зони. При однобічному блокуванні фіксаторами виявлено нові зони підвищених навантажень у кістковій тканині метаепіфіза нижче від росткової зони. Найбільше напруження у фіксаторах відзначено в зоні контакту проксимального гвинта з пластиною, а також у верхній частині скоби.Висновок. Варусна деформація проксимального відділу великогомілкової кістки веде до підвищення навантажень у медіальній частині проксимальної росткової зони. Використання різних фіксаторів для однобічного блокування проксимальної росткової зони великогомілкової кістки призводить до появи відмінних напружень у проксимальному її епіметафізі. До мінімального підвищення напружень у кістковій тканині метафіза приводять варіанти фіксації із застосуванням пластин, а використання скоб Блаунта значно підвищує напруження в кістковій тканині в ділянці розташування скоб.

Evaluation of Intra-Articular Injection of Bevacizumab on the Prevention of Physeal Bar Formation in Type 4 Salter Harris Model in Rats: A Pilot Study

Background: This study was designed to achieve a new method as a preventive treatment for complications of growth plate fractures. In this study, we investigate the effect of intra-articular injection of anti-vascular endothelial growth factor (anti-VEGF) antibody bevacizumab on the repair process of articular cartilage in a type 4 Salter Harris injury model.&#x0D; Methods: A Salter Harris injury was created on the proximal tibial growth plate of 14 rats by a 1.8 mm drill. The rats were randomly classified into two groups: group LD, administration of high-dose intra-articular injection of bevacizumab (250 μg), and group HD, administration of low-dose intra-articular injection of bevacizumab (50 μg) after injury. The rats were killed 2 months postoperatively and their tibia underwent micro-computed tomography (CT) analysis, histological assessment, and measurement of tibial bone length.&#x0D; Results: Bony bar formation was observed in 71% of the samples in the high-dose group and in 100% of the low-dose group. Relative increase in physeal cartilage thickness (P = 0.007) and decrease in bony bar formation (P = 0.029) were observed significantly in the high dose group. There was no significant difference in tibia length between the two groups (P = 0.150).&#x0D; Conclusion: Intra-articular administration of bevacizumab demonstrated positive restorative effects. We suggest this method of treatment due to its potential of improving cartilage repair and capability to be used as a main or adjacent treatment in osteochondral defects.

Varus knee deformity in adolescent soccer players

The lower limb axis develops dynamically throughout the first and second decades of life. In recent years, with respect to youth athletes, we have been facing a progressive increase in the intensity of exercise during training and competition (involving increased time, frequency, and power), and, as a result, there hasbeen an increase in the number of acute and chronic overuse injuries. There are some sports with a higher incidence of injuries, one of which is soccer. A review of literature for the past 15 years with a focus on varus knee deformities in adolescent soccer players showed that varus axial deformities of the lower limbsoccur more frequently in soccer players than in the general population and in athletes from other sport, probably due to the specific loading pattern in soccer training. Varus deformities alter knee biomechanics, which results in medial joint space overloading, and consequently an early onset of degenerative joint disease. In addition, bowlegs predisposes athletes to patellofemoral pain syndrome and meniscal lesions. The etiology of genu varum in soccer is thought to be multifactorial, ranging from the natural selection of players to mechanical overload of the proximal medial tibial growth plate. A growing number of clinical reports and animal studies have indicated that intensive sport training may precipitate pathologic changes of the knee joint growth plate, and even produce a growth disturbance.

EXTH-70. ESTABLISHMENT OF INTRAVENTRICULAR SHH INHIBITION AS A THERAPEUTIC OPTION IN YOUNG PATIENTS WITH MEDULLOBLASTOMA

Abstract Medulloblastoma is the most common malignant brain tumor in children. The embryonal tumor arises in the posterior fossa and disseminates via the cerebrospinal fluid. Medulloblastoma divides in four molecular subgroups, one of which is characterized by mutations in the sonic-hedgehog (SHH) -pathway. SHH inhibition provides an elegant way of targeted therapy. The small molecule Vismodegib allosterically inhibits Smoothened (SMO), an upstream activator of SHH. Unfortunately, Vismodegib has shown to cause irreversible premature epiphyseal growth plate fusions in preclinical studies and clinical trials, preventing its systemic application in children (Kimura et al. 2008; Robinson et al. 2017). We established an intraventricular therapy with Vismodegib, combining the benefits of targeted drug delivery and minimizing systemic side effects. In a mouse model for SHH medulloblastoma, we compare intraventricular, oral and placebo treatment regarding effects on survival, tumor biology, and bone morphology. Math1-cre::Ptch1 Fl/Fl mice show a homozygous loss of PTCH1 in Math1-positive cells, resulting in SHH-pathway overactivation and development of SHH medulloblastomas. At postnatal day 11-13, Math1-cre::Ptch1 Fl/Fl mice were randomized in four treatment arms: group A (n= 9) received placebo intrathecally, B (n= 9) received Vismodegib 200 mg/kd/d orally, C (n= 19) received Vismodegib 0.2 mg/kg/d intrathecally, and D (n= 8) received Vismodegib 1.6 mg/kg/d intrathecally. Kaplan-Meier survival analysis showed a significant survival benefit for 1.6 mg/kg/d intraventricular Vismodegib compared to placebo (p= 0.012). Bone histology and X-ray analysis of intraventricular treated mice showed intact femoral and tibial growth plates, in contrast to orally treated mice that developed skeletal malformations. Further analyses such as DNA sequencing, gene expression analysis, and histological evaluation are ongoing and will add to the picture of the anti-tumor effects of intraventricular SHH-inhibition. Based on the preliminary experimental results, we conclude that intrathecal application of a SMO-inhibitor might evolve as a promising new way of targeted treatment of SHH medulloblastomas.

Salter-Harris Type 2 Injury of the Proximal Tibial Epiphysis in a 15-year-old Athlete: A Rare Case Report.

Background:Proximal tibial epiphyseal injuries in adolescents are uncommon accounting to 0.5 to 3 % of all epiphyseal injuries. Although rare, the proximity of popliteal artery puts this region at an increased risk of vascular injury and compartment syndrome. Also, premature closure of the growth plate can cause restrictions in growth and angular malformations. The fractures may often be missed on routine X-rays. Frequent monitoring and further testing should be done to better diagnose these injuries.Case History:We present a case of an adolescent football player (15 years old) who injured his left knee and was diagnosed to have Salter- Harris II proximal tibial epiphyseal injury. Routine radiographs revealed minimal widening in his epiphysis anteriorly when compared to his contralateral knee. Magnetic resonance imaging (MRI) findings revealed a fracture passing through the growth plate of proximal tibia exiting posteriorly into the tibial metaphysis. Management included closed manipulation and plaster cast immobilization with regular follow-ups. At the end of 1.5 years, the patient had full range of motion without any residual deformities.Conclusions:High clinical suspicion is required to diagnose these rare injuries. When in doubt, MRI is advocated to better delineate the fracture as the potential complications can be limb threatening. Anatomical reduction and adequate immobilization should be done to prevent deformities and good functional outcome in the long term.

Characterisation of Growth Plate Dynamics in Murine Models of Osteoarthritis.

The purpose of this study was to investigate growth plate dynamics in surgical and loading murine models of osteoarthritis, to understand whether abnormalities in these dynamics are associated with osteoarthritis development. 8-week-old C57BL/6 male mice underwent destabilisation of medial meniscus (DMM) (n = 8) surgery in right knee joints. Contralateral left knee joints had no intervention (controls). In 16-week-old C57BL/6 male mice (n = 6), osteoarthritis was induced using non-invasive mechanical loading of right knee joints with peak force of 11N. Non-loaded left knee joints were internal controls. Chondrocyte transiency in tibial articular cartilage and growth plate was confirmed by histology and immunohistochemistry. Tibial subchondral bone parameters were measured using microCT and correlated to 3-dimensional (3D) growth plate bridging analysis. Higher expression of chondrocyte hypertrophy markers; Col10a1 and MMP13 were observed in tibial articular cartilage chondrocytes of DMM and loaded mice. In tibial growth plate, Col10a1 and MMP13 expressions were widely expressed in a significantly enlarged zone of proliferative and hypertrophic chondrocytes in DMM (p=0.002 and p<0.0001, respectively) and loaded (both p<0.0001) tibiae of mice compared to their controls. 3D quantification revealed enriched growth plate bridging and higher bridge densities in medial compared to lateral tibiae of DMM and loaded knee joints of the mice. Growth plate dynamics were associated with increased subchondral bone volume fraction (BV/TV; %) in medial tibiae of DMM and loaded knee joints and epiphyseal trabecular bone volume fraction in medial tibiae of loaded knee joints. The results confirm articular cartilage chondrocyte transiency in a surgical and loaded murine models of osteoarthritis. Herein, we reveal spatial variation of growth plate bridging in surgical and loaded osteoarthritis models and how these may contribute to anatomical variation in vulnerability of osteoarthritis development.

Analysis of the effects of isotretinoin on the premature epiphyseal closure in pediatric populations: a literature review.

Oral isotretinoin, a systemic retinoid and a vitamin A derivative, has been widely utilized to treat acne in both adult and pediatric populations. Additionally, systemic retinoids have also been utilized to treat neuroblastoma in pediatric patients. Common side effects associated with oral isotretinoin include dry eyes, dry mouth, elevated liver enzymes, depression, and arthralgia. Less common side effects of isotretinoin include hearing loss, pseudotumor cerebri, anaphylaxis, and skeletal abnormalities including growth arrest. The U.S. Food and Drug Administration (FDA) has received reports of premature epiphyseal closure in patients treated with isotretinoin retinoids, which are commonly prescribed by primary care providers as a treatment for acne. It is important to raise awareness of the potential side effects of isotretinoin to enable informed treatment decisions before beginning an isotretinoin regimen. This chapter aims to elucidate that isotretinoin, given at various doses and durations, has been associated with growth plate abnormalities, which can lead to premature epiphyseal closure. Two databases were utilized for the literature review and were conducted at different time periods. Our literature review was conducted between December 2020 and June 2021, utilizing PubMed with the following search terms: "isotretinoin" and "isotretinoin and premature epiphyseal closure." In April 2021, we searched the FDA's "Drug Data and Adverse Event Report System" utilizing the terms "isotretinoin" and "epiphysis premature fusion." We included in our query reports of patients worldwide under 18years of age with premature epiphyseal closure or growth plate damage secondary to isotretinoin. Studies published in English between 1980 and 2020 were also included, as well as background sources relating to an isotretinoin profile with side effects and dosing. We narrowed our search to exclude patients with a history of growth plate disorders due to trauma, malignancy, or other pathological processes, as well as patients with growth arrest due to endocrine factors. Growth plate abnormalities associated with retinoid derivatives other than isotretinoin were also excluded. A total of 28 items were selected for our literature review including: one FDA drug label, one FDA website of adverse reactions, 19 supplemental articles, six case reports, and one case series of premature epiphyseal closure secondary to isotretinoin. The FDA received 41 reports worldwide of premature epiphyseal closure related to isotretinoin in patients under 18years of age. Additionally, premature epiphyseal closure and growth plate abnormalities occurred in nine patients with various durations and doses of isotretinoin ranging from the lowest dose of 0.5mg/kg/day for a few months to 3.5mg/kg/day for years. Isotretinoin-induced premature epiphyseal closure and growth plate deformities seem to be linked to higher doses of isotretinoin for the duration of months to years. There have been reported cases of premature epiphyseal closure in individuals receiving therapeutic doses of isotretinoin for acne treatment, which are much lower compared to the high doses utilized for neuroblastoma. Based on this study, isotretinoin appears to impact the growth plates of proximal tibia and distal femur. A cause-and-effect relationship between isotretinoin and premature epiphyseal closure cannot be concluded.

Enhanced Extracellular Matrix Degradation in Growth Plate Contributes to Manganese Deficiency-Induced Tibial Dyschondroplasia in Broiler Chicks.

Manganese (Mn) is a crucial trace element for poultry nutrition, and its deficiency compromises tibial cartilage development, leading to perosis and a higher incidence of slipped tendon. Tibial dyschondroplasia (TD) is a metabolic cartilage disease characterized by disruption of endochondral bone formation, which is closely related to extracellular matrix (ECM) degradation, in which Mn deficiency plays an important role. Previous studies have confirmed the role of matrix metalloproteinases (MMPs) in the pathogenesis of TD, but whether dysregulated ECM degradation and MMP expression profiles in growth plate are involved in Mn deficiency-induced avian TD has not been fully elucidated yet. Thus, this study was conducted to clarify these issues. Firstly, we successfully established TD model induced by Mn deficiency in broiler chicks. Mn deficiency decreased the number of chondrocytes, contents of proteoglycan, and type II collagen in tibial growth plate, demonstrating the tibial growth plate damage with enhanced ECM degradation. Also, Mn deficiency inhibited the Nrf2 signaling pathway and enhanced the protein levels of NLRP3, active caspase-1, and active IL-1β in tibial growth plate, indicating the oxidative stress and inflammatory response in Mn deficiency-induced TD. Additionally, upregulated expression levels of MMPs (MMP1, 9, and 13) were observed in tibial growth plate of Mn deficiency group. In summary, these findings suggest that Mn deficiency-enhanced ECM degradation is involved in avian TD, which may be correlated with oxidative stress, inflammatory response, and upregulation of MMPs.

Manganese deficiency induces avian tibial dyschondroplasia by inhibiting chondrocyte proliferation and differentiation

Manganese (Mn) is an essential trace element for bone growth, and its deficiency has been shown to increase the incidence of leg abnormalities in fast-growing broilers, such as tibial dyschondroplasia (TD). Proliferation and differentiation of growth plate chondrocyte are critical for tibia development, but their roles in Mn deficiency-induced TD remains to be elucidated. Thirty 1-day-old Arbor Acres chicks were randomly divided into two groups and fed with control diet (60 mg Mn/kg diet) and Mn-deficiency diet (22 mg Mn/kg diet) for 42 days, respectively. Mn deficiency-induced TD model was successfully established and samples from proximal tibia metaphysis and growth plate were collected for assays. Pathological observation showed that Mn deficiency induced morphological abnormality and irregular arrangement of chondrocytes in proliferative and hypertrophic zone of tibial growth plate. Also, Mn deficiency decreased mRNA and protein expression levels of type II collagen and type X collagen in tibial growth plate, indicating the impairment of proliferating and hypertrophic chondrocytes. Moreover, down-regulated gene expression levels of Sox9, Tgf-β, Ihh, Runx2, Mef2c and Bmp-2 were shown in tibial growth plate of Mn-deficiency group, demonstrating that Mn deficiency inhibited the transcription levels of key regulators to disrupt chondrocyte proliferation and differentiation. Collectively, these findings confirmed that Mn deficiency affected the proliferation and differentiation of chondrocytes in tibial growth plate via inhibiting related regulatory factors, leading to TD in broilers.

G-Protein-Coupled Estrogen Receptor-1 Positively Regulates the Growth Plate Chondrocyte Proliferation in Female Pubertal Mice.

Estrogen enhances long bone longitudinal growth during early puberty. Growth plate chondrocytes are the main cells that contribute to long bone elongation. The role of G-protein-coupled estrogen receptor-1 (GPER-1) in regulating growth plate chondrocyte function remains unclear. In the present study, we generated chondrocyte-specific GPER-1 knockout (CKO) mice to investigate the effect of GPER-1 in growth plate chondrocytes. In control mice, GPER-1 was highly expressed in the growth plates of 4- and 8-week-old mice, with a gradual decline through 12 to 16 weeks. In CKO mice, the GPER-1 expression in growth plate chondrocytes was significantly lower than that in the control mice (80% decrease). The CKO mice also showed a decrease in body length (crown–rump length), body weight, and the length of tibias and femurs at 8 weeks. More importantly, the cell number and thickness of the proliferative zone of the growth plate, as well as the thickness of primary spongiosa and length of metaphysis plus diaphysis in tibias of CKO mice, were significantly decreased compared with those of the control mice. Furthermore, there was also a considerable reduction in the number of proliferating cell nuclear antigens and Ki67-stained proliferating chondrocytes in the tibia growth plate in the CKO mice. The chondrocyte proliferation mediated by GPER-1 was further demonstrated via treatment with a GPER-1 antagonist in cultured epiphyseal cartilage. This study demonstrates that GPER-1 positively regulates chondrocyte proliferation at the growth plate during early puberty and contributes to the longitudinal growth of long bones.

DDIT3/CHOP promotes autophagy in chondrocytes via SIRT1-AKT pathway

Endoplasmic reticulum (ER) stress can initiate autophagy via unfolded protein response (UPR). As a key downstream gene of UPR, DDIT3/CHOP is expressed in chondrocytes. However, the regulation mechanism of DDIT3/CHOP on autophagy in chondrocytes remains unclear. In this study, the expression levels of autophagic markers Beclin1 and LC3B were found to decrease while p62 increase in the tibial growth plate and costal primary chondrocytes from DDIT3/CHOP KO mice. In vitro, overexpressing DDIT3/CHOP induced autophagy in ATDC5 chondrocytes, displaying an elevated immunofluorescence signal of LC3B and elevated numbers of autophagosomes and autolysosomes. Analysis of the gain- and loss-of-function indicated that the protein level of Beclin1 and the ratio of LC3BII/I increased in DDIT3/CHOP overexpression cells, whereas decreased in DDIT3/CHOP knockdown cells. The decreased level of p62 and additional accumulation of LC3BII caused by chloroquine (CQ) further indicated that DDIT3/CHOP enhanced autophagic flux. Mechanistically, we found that DDIT3/CHOP binds directly to the promoter of SIRT1 to promote its expression by CHIP, qRT-PCR, and Western blot analysis. In addition, SIRT1 enhanced autophagic activity in ATDC5 cells, and inhibition or activation of SIRT1 partially reversed the effect of overexpressing or downregulating DDIT3/CHOP on autophagy. Furthermore, AKT signaling was found to be responsible for DDIT3/CHOP-regulated autophagy in ATDC5 cells. SIRT1 knockdown reversed the effect of DDIT3/CHOP overexpression on AKT signaling. In conclusion, our data clarifies that DDIT3/CHOP promotes autophagy in ATDC5 chondrocytes through the SIRT1-AKT pathway. These results were also confirmed in the primary chondrocytes.

The effects of in ovo administered bisphenol A on tibial growth plate histology in chicken

The aim of this study was to determine of the effects of in ovo administered BPA on embryonic development of the tibial growth plate using histological methods in chickens. Three hundred and ten fertile eggs of Isa Brown laying parent stock were divided into five groups as untreated control, vehicle-injected control, 50, 100, and 250 μg/egg BPA. At the 13th, 18th, and 21st days of incubation, eggs were randomly opened from each group until 10 live embryos were obtained. Embryos were weighed and crown-rump length was measured. Tibial tissue samples were taken from embryos. Tibia weight, relative tibia weight and tibia length were determined. Tissue samples were fixed in 10% buffered formalin solution. Sections were stained with Safranin O staining methods and zones in the growth plate were measured. Also, proliferating cell nuclear antigen (PCNA) was stained immunohistochemically. The mortality in the BPA treated groups was higher than untreated control group. The results have revealed that mean relative embryo weights, crown-rump length, mean tibia weight, relative tibia weight, and tibia length of BPA treated groups were significantly lower when compared to the untreated control and vehicle-injected control groups. Also, proliferative zone get significantly narrowed, whereas the transitional and hypertrophic zone thickened and PCNA positive chondrocytes increased in growth plate of BPA treated groups. These results have suggested that developmental exposure to BPA adversely affected development of the tibial growth plate.

Specificity for the Epiphyseal Round Cell Layer is Significantly Associated With Height GWAS​

Human height is a model polygenic trait with thousands of height-related SNPs identified in GWAS to date. An important determinant of height is the proliferation and hypertrophy of growth plate chondrocytes during childhood long bone elongation. Connecting the expression of specific genes that affect skeletal biology to associated variants in GWAS remains a difficult challenge. To connect the genetics of height and growth plate gene expression, we studied the relationship between gene expression in the murine growth plate and common-variant associations from GWAS of height. To obtain gene expression data from the growth plate, we dissected three layers of murine tibial growth plates, extracted RNA from each layer, and measured expression using the Affymetrix GeneChip 430 3.0. For each gene, we derived a specificity score for each growth plate layer, and SNP-level p-values from a published GWAS of height (N~700000) were combined into gene-level p-values using MAGMA. We then used MAGMA to test for association between specificity of expression for each growth plate layer and the GWAS gene level p-values for height. We found that specificity for the round cell layer is significantly associated with height GWAS p-values (p = 8.5x10-9). This association remains when we condition on each of the other cell layers and on membership in a set of genes from OMIM that cause skeletal growth disorders (3.3x10-8 < p < 4.1x10-6). We replicated this result in a RNA-seq dataset of maturing chondrocytes sampled at three time points during development in vitro (days 3, 5, and 10): we found that z-scores for expression in the earliest two days of development are significantly associated with gene-level p-values from height GWAS (pDay3 = 1.2x10-21 and pDay5 = 2.0x10-20) and that this association remains after conditioning on the other timepoints and on the OMIM gene set (3.1x10-20 < pDay3 < 8.3x10-5; 3.7x10-19 < pDay5 < 0.002). We then performed pathway analysis of genes that are both highly specific to the round layer and highly significant in GWAS using Enrichr. Together, our results suggest that genes expressed in early chondrocyte development (the round cell layer) are particularly relevant to the contribution of growth plate-expressed genes to height. This conclusion both sheds light on the regulation of human skeletal growth and also helps prioritize relevant genes implicated from the height GWAS in skeletal biology.

Physeal Fractures of Distal Tibia: A Systematic Review and Meta-analysis.

Fractures involving the distal tibia growth plate are common in children. Injury or treatment that damages the growth plate may result in progressive angular deformity or leg length discrepancy. There is no consensus on treatment and follow-up of these injuries. This study aims to describe which factors increase the risk of premature physeal closure (PPC). A systematic review and meta-analysis were performed. Altogether 395 articles were reviewed, and ultimately 12 of them were found eligible, comprising 1997 patients. The most usual type of fracture was Salter-Harris (SH) II (n=855, 49%) followed by SH III (n=296, 17%) and SH I (n=261, 15%). The risk of PPC according to number of reduction attempts, method of treatment, and residual displacement was the primary outcome. The total rate of PPC was 13% (n=245). The PPC rate varied from 0.2% to 42% across the studies. Patients with SH IV fractures were most likely to develop PPC (20%), followed by those with SH II (12%) (P<0.05) and repeated (>2) reduction maneuvers were associated with a higher risk of PPC (pooled odds ratio, 8.5; 95% confidence interval, 6.3-12.17; P<0.05). Open reduction was associated with a lower risk of PPC when analyzing only displaced fractures (odds ratio, 0.63; 95% confidence interval, 0.38-0.91; P<0.05). This meta-analysis implies that residual displacement after reduction is the most significant factor in predicting PPC. It seems that open reduction might reduce the PPC rate among patients with dislocated fractures. In addition, there is some evidence that a higher number of reduction attempts correlates positively with the risk of PPC.

Thm2 interacts with paralog, Thm1, and sensitizes to Hedgehog signaling in postnatal skeletogenesis.

Mutations in the intraflagellar transport-A (IFT-A) gene, THM1, have been identified in skeletal ciliopathies. Here, we report a genetic interaction between Thm1, and its paralog, Thm2, in postnatal skeletogenesis. THM2 localizes to primary cilia, but Thm2 deficiency does not affect ciliogenesis and Thm2-null mice survive into adulthood. However, by postnatal day 14, Thm2-/-; Thm1aln/+ mice exhibit small stature and small mandible. Radiography and microcomputed tomography reveal Thm2-/-; Thm1aln/+ tibia are less opaque and have reduced cortical and trabecular bone mineral density. In the mutant tibial growth plate, the proliferation zone is expanded and the hypertrophic zone is diminished, indicating impaired chondrocyte differentiation. Additionally, mutant growth plate chondrocytes show increased Hedgehog signaling. Yet deletion of one allele of Gli2, a major transcriptional activator of the Hedgehog pathway, exacerbated the Thm2-/-; Thm1aln/+ small phenotype, and further revealed that Thm2-/-; Gli2+/- mice have small stature. In Thm2-/-; Thm1aln/+ primary osteoblasts, a Hedgehog signaling defect was not detected, but bone nodule formation was markedly impaired. This indicates a signaling pathway is altered, and we propose that this pathway may potentially interact with Gli2. Together, our data reveal that loss of Thm2 with one allele of Thm1, Gli2, or both, present new IFT mouse models of osteochondrodysplasia. Our data also suggest Thm2 as a modifier of Hedgehog signaling in postnatal skeletal development.

English

Tetramethyl thiuram disulfide (thiram) is an important dithiocarbamate bactericide; it has been widely used for the control of various diseases in fruits, vegetables, seeds and food grains. However, it also causes environmental pollution problems and poses a threat to human health to a certain extent. Thiram induces tibial dyschondroplasia (TD) by causing oxidative stress and antioxidants imbalance in tibial growth plate in poultry. TD is a skeletal abnormality in fastgrowing poultry birds. It has been considered an economically important disease in poultry that affects poultry industry by carcass loss at meat processing plant due to decrease in disease resistance, production performance, and carcass quality and induces breast cysts and osteomyelitis worldwide. Oxidative stress is developed due to the imbalance of free radical oxygen, which disrupts the equilibrium state of oxidant and antioxidant tending to oxidation. This review is based on the current research, mainly to explore the relationship and mechanism between tibial dyschondroplasia and oxidative stress induced by thiram, which provides a new theoretical foundation for the further research of the related mechanism.

Cluster of differentiation 147 (CD147) expression is linked with thiram induced chondrocyte’s apoptosis via Bcl-2/Bax/Caspase-3 signalling in tibial growth plate under chlorogenic acid repercussion

Tibial dyschondroplasia (TD) is a metabolic disease of young poultry that affects bone andcartilage's growth. It mostly occurs in broilers due to thiram toxicity in the feed. In this disease, tibial cartilage is not yet ripe for ossification, but it also results in lameness, death, and moral convictions of commercial poultry due to numerous apoptotic changes on cell level. These changes serve a cardinal role in this situation. Many potential problems indicate that chlorogenic acid (CGA) performs an extensive role in controlling apoptosis's perception. However, the actual role of CGA in TD affected chondrocytes in-vitro is still unidentified. The current study investigates the imperceptible insight of CGA on chondrocyte’s apoptosis via B-cell lymphoma 2 (Bcl-2), Bcl-2 associated x-protein (Bax), and Caspase-3 with CD147 signalling. The expression of these markers was investigated by Immunofluorescence, western blot analysis, and reverse transcription-quantitative polymerase chain (RT-qPCR). Chondrocytes from the growth plate of tibia were isolated, cultured, and processed. A sub-lethal thiram (2.5 μg/mL) was used to induce cytotoxicity and then treated with an optimum dose (40 μg/ mL) of CGA. According to the results, thiram distorted chondrocyte cells with enhanced apoptotic rate. But, in case of CGA, high expression of CD147 enhanced cell viability of chondrocytes, accompanied by downregulation of Bax/Caspase-3 signalling with the upregulation of Bcl-2. The first possibility has ruled out in the present study by the observation that the cells apoptosis marker, Caspase-3 showed a significant change in CD147 overexpressing cells. Conversely, immunodepletion of CD147 with enhanced cleavage of Caspase-3, indicating the activation of apoptosis in chondrocytes cells. Therefore, these findings suggest a novel insight about CD147 in thiram induced TD about the regulation of Bcl-2/Bax/Caspase-3 apoptosis-signalling axis.