Paternal cadmium exposure induces glucolipid metabolic reprogramming in offspring mice via PPAR signaling pathway.

In industrialized societies, the prevalence of metabolic diseases has substantially increased over the past few decades, yet the underlying causes remain unclear. Cadmium (Cd) is a hazardous heavy metal and pervasive environmental endocrine disruptor. Here, we investigate the effects of paternal Cd exposure on offspring glucolipid metabolism. Paternal Cd exposure (1 mg kg-1 body weight) impaired glucose tolerance, increased random serum glucose and fasting serum insulin, elevated serum total cholesterol, and low-density lipoprotein in offspring mice. Untargeted metabolomics analysis of male offspring liver tissue revealed that paternal Cd exposure can affect offspring glucolipid metabolic reprogramming, which involved biosynthesis of phenylalanine, tyrosine and tryptophan, biosynthesis of unsaturated fatty acids, metabolism of linoleic acid, arachidonic acid and α-linolenic acid. Transcriptome sequencing of male offspring liver tissue showed that arachidonic acid metabolism, AMPK signaling pathway, PPAR signaling pathway and adipocytokine signaling pathway were significantly inhibited in the Cd-exposed group. The mRNA expression levels of PPAR signaling pathway related genes (Acsl1, Cyp4a14, Cyp4a10, Cd36, Ppard and Pck1) were significantly decreased. The protein expression levels of ACSL1, CD36, PPARD and PCK1 were also significantly reduced. Collectively, our findings suggest that paternal Cd exposure affect offspring glucolipid metabolic reprogramming via PPAR signaling pathway.

Probucol suppresses osteoclastogenesis via activating Nrf2 signaling and ameliorates ovariectomy-induced bone loss.

Osteoporosis is a systemic and endocrine bone disorder distinguished by declined bone mineral density, compromised bone strength, and destruction of trabecular structure. The abnormally excessive osteoclastogenesis and bone erosion play imperative roles in the progression of osteoporosis. However, treatment of osteoporosis is far from satisfactory due to poor adherence to existing medications and adverse reactions, there is an urgent to develop novel therapies for osteoporosis. Probucol, a synthetic compound with two characteristic phenolic rings, owns anti-inflammatory and antioxidant properties. Accumulating evidence have indicated that intracellular reactive oxygen species (ROS) is closely related to osteoclastogenesis. Hence, we investigated the potential effects of probucol on osteoclastogenesis in vivo and in vitro. In this study, TRAP staining and bone slice resorption assay showed that probucol suppressed RANKL-induced osteoclast formation and function. The mRNA and protein levels of osteoclastogenesis marker genes were reduced by probucol in a concentration-dependent manner. Besides, probucol suppressed osteoclast differentiation by inhibiting ROS production, MAPKs and NF-κB signaling pathways, while Nrf2 silencing reversed the inhibitory effect of probucol on osteoclast formation and function. Consistent with the above findings, in vivo experiments demonstrated that probucol visibly alleviated bone loss caused by estrogen deficiency. In brief, these results showed the potential of anti-oxidant compound probucol in the treatment of osteoporosis, highlighting Nrf2 as a promising target in osteoclast-related disease.

Nonunion of humeral medial condyle fracture caused by excessive functional exercise: a case report and review of the literature.

BACKGROUND: Medial epicondyle fractures are one of the more common humerus fractures, but humeral medial condyle fracture (HMCF) is rare. Nonunion of medial humeral condyle fractures due to functional exercise is less common. CASE PRESENTATION: We report a 5-year-old patient with a nonunion HMCF due to excessive functional exercise, who bruised the elbow 1 year ago and had no positive findings on all imaging studies. On this physical examination, there was a snapping and palpable lump in the elbow joint during movement, but the patient did not feel any discomfort and the range of motion of the joint was normal. X rays and computed tomography (CT) showed that the left HMCF was discontinuous, the broken ends were dislocated, and the joint alignment was poor. Open reduction (OR) and screw fixation was used during the operation, and the patient recovered well at 3-month follow-up. CONCLUSIONS: The rarity and low radiographic appearance of displaced HMCF are easily overlooked and can eventually lead to nonunion HMCF, especially when radiographically difficult to visualize before age 5 years. Therefore, regardless of whether there are signs or imaging abnormalities in the growth process of adolescents, they should be vigilant, shorten the time interval for re-examination, and early detection and timely treatment can avoid some complications caused by this.

Skin grafting treatment of adolescent lower limb avulsion injury.

Background: Under the influence of various factors, the number of lower extremity avulsion injuries in adolescents is increasing year by year. The main modality of treatment is skin grafting. There are many types of skin grafting. Although many studies on skin grafting after avulsion injuries have been published in the past few decades, there are differences in the treatment options for adolescents with post avulsion injuries. Main body: Thorough debridement and appropriate skin grafts are essential for the surgical management of avulsion injuries for optimal prognosis. In the acquisition of grafts, progress has been made in equipment for how to obtain different depths of skin. The severity of the avulsion injury varies among patients on admission, and therefore the manner and type of skin grafting will vary. Especially in adolescents, graft survival and functional recovery are of great concern to both patients and physicians. Therefore, many efforts have been made to improve survival rate and activity. Conclusion: This review summarizes the principles of treatment of avulsion injuries, the historical development of skin grafts, and the selection of skin grafts, hoping to be helpful for future research.

Effect of the Number, Size, and Location of Cannulated Screws on the Incidence of Avascular Necrosis of the Femoral Head in Pediatric Femoral Neck Fractures: A Review of 153 Cases.

BACKGROUND: The correlation between the number, size, and location of cannulated screws and the incidence of avascular necrosis (AVN) in children with femoral neck fractures treated surgically is uncertain. METHODS: We retrospectively reviewed 153 children (mean age: 10.6±3.7 y) with femoral neck fractures treated by internal fixation with 2 (n=112) or 3 (n=41) cannulated screws. The severity of initial displacement was divided into incomplete (type I) and complete (type II, angulation <50 degrees; type III, angulation >50 degrees) fractures. The diameter of the screw was measured and recorded as a percentage of the femoral neck width. The distance (D) between the mid-point of each screw at the base (B) of the femoral neck and at the tip (T) of each screw and the superior and anterior cortices of the femoral neck, respectively, were measured on anteroposterior (AP) and lateral (L) radiographs. Values were expressed as the ratio between the measured distance and the width of the femoral neck (BDAP%, TDAP%, BDL%, and TDL%). The correlation between the number, size, and location of the screws and AVN was analyzed. RESULTS: Patients with type II of initial displacement treated with 2 cannulated screws had a lower AVN rate (21.4%) than those treated with 3 screws (44.8%) (P=0.027). Screw diameter (19%) in patients with AVN was larger than (17%) in patients without AVN (P<0.001); patients with AVN had a lower BDAP% (48.6%) than those without AVN (56.4%) (P<0.001). Screw size and BDAP% were risk factors for AVN (P<0.05). Further, screw diameter >16.5% and BDAP% <51.6% of the femoral neck width were the cutoff values for an increased AVN rate (P<0.05). CONCLUSIONS: Patients treated with 2 cannulated screws showed a lower rate of AVN than patients treated with 3 screws. Screws of larger size and screws closer to the piriformis fossa on AP radiographs increased the risk of AVN in children with femoral neck fractures treated surgically. LEVEL OF EVIDENCE: Level III.

Diaphyseal and Metaphyseal Modeling Defects-Clinical Findings and Identification of WRAP53 Deficiency in Craniometadiaphyseal Dysplasia.

Background: Diaphyseal and metaphyseal modeling defects lead to severe changes in bone mass and shape, which are common features in osteoporosis that linked to non-vertebral fractures. Original mechanism of diaphyseal and metaphyseal modeling defects has proved elusive. Studying rare syndromes can elucidate mechanisms of common disorders and identify potential therapeutic targets. Methods: We evaluated a family pedigree with craniometadiaphyseal dysplasia (CRMDD, OMIM 269300), a genetic disorder that is characterized by cortical-bone thinning, limb deformity, and absent of normal metaphyseal flaring and diaphyseal constriction. Systemic radiographic examination and serum hormone test were made for this rare disease. One patient and her two normal parents were examined by means of whole-exome sequencing (WES) to identify the candidate pathogenic gene and rule out mucopolysaccharidosis and Prader-Willi Syndrome by means of Sanger sequencing. Results: There are several conspicuous radiographic characteristics: (1) bullet-shaped phalanges, (2) long and narrow pelvic inlet, absent of supra-acetabular constriction, (3) round rod-shaped long tubular bones, (4) prominent aiploic mastoid, (5) bending-shaped limb, genua varus and genu varum, and (6) congenital dislocation of elbow. Here, we did not find any wormian bones, and there are several typical clinical characteristics: (1) macrocephaly and wide jaw, (2) Avatar elf-shaped ears, pointed and protruding ears, (3) hypertrophy of limbs, (4) flat feet and giant hand phenomenon, (5) nail dystrophy, (6) limb deformity, (7) high-arched palate, (8) superficial hemangiomas, (9) tall stature, and intellectual disability. In this patient, we found biallelic frameshift deletion mutations in WRAP53, and those two mutations were transmitted from her parents respectively. Conclusions: We describe her clinical and radiological findings and presented a new subtype without wormian bones and with a tall stature. Our study showed that craniometadiaphyseal dysplasia was caused by a deficiency of WRAP53 with autosomal recessive inheritance.

Phalangeal Intra-Articular Osteochondroma Caused a Rare Clinodactyly Deformity in Children: Case Series and Literature Review.

Background: Various factors are discovered in the development of clinodactyly. The purpose of this retrospective study was to present a group of children with a rare clinodactyly deformity caused by phalangeal intra-articular osteochondroma and evaluate the efficacy of various treatment methods. Methods: All child patients that were treated for finger problems in our center between Jan 2017 and Dec 2020 were reviewed. A detailed analysis was made of the diagnosis and treatment methods in eight rare cases. X-rays and histopathology were applied. Results: A preliminary analysis of 405 patients in total was performed, and we included eight cases in our final analysis. This cohort consisted of 2 girls and 6 boys, with a mean age of 5.74 ± 3.22 years (range: 2y5m to 11y). Overall, four patients had their right hand affected and four patients had their left hand affected. One patient was diagnosed as having hereditary multiple osteochondroma (HMO) while the other seven patients were all grouped into solitary osteochondroma. Osteochondroma was proven in all of them by histopathology examination. Preoperative X-rays were used to allow identification and surgery planning in all cases. All osteochondromas were intra-articular and in the distal end of the phalanges, which is located opposite the epiphyseal growth area. All of the osteochondromas developed in half side of the phalanges. The angulation in the finger long axis was measured, and resulted in a mean angulation of 34.63 ± 24.93 degree (range: 10.16-88.91 degree). All of them received surgery, resulting in good appearance and fingers straightening. No recurrence was recorded. Conclusions: This retrospective analysis indicates that 10 degrees can be selected as the angulation level for diagnosis of clinodactyly deformities. What's more important, the abnormal mass proven by X-rays should be included as the classical direct sign for diagnosis. The first choice of treatment is surgery in symptomatic osteochondromas.

PERK signaling pathway in bone metabolism: Friend or foe?

Osteoblasts and osteoclasts participate in the process of bone remodelling to meet the needs of normal growth and development or repair pathological damage. Endoplasmic reticulum stress (ER stress) can break the intracellular homeostasis of osteoclasts and osteoblasts, which is closely related to abnormal bone remodelling. The double-stranded RNA-dependent protein kinase (PKR)-like ER kinase (PERK) is a key transmembrane protein that regulates ER stress, and growing evidence suggests that the PERK pathway plays a crucial role in regulating bone metabolism under both physiological and pathological conditions. Based on the current findings, we summarized the main mechanisms involved in bone metabolism downstream of the PERK pathway, among which elF2α, FOXO1, CaN, Nrf2 and DAG play a role in regulating the differentiation of osteoblasts and osteoclasts. Importantly, strategies by the regulation of PERK pathway exert beneficial effects in preclinical trials of several bone-related diseases. Given the importance and novelty of PERK pathway, we provide an overview and discuss the roles of PERK pathway in regulating bone metabolism and its impact on bone-related diseases. We hope that the development of research in this field will bring a bright future for the treatment of bone-related diseases.

Initial displacement as a risk factor for avascular necrosis of the femoral head in pediatric femoral neck fractures: a review of one hundred eight cases.

PURPOSE: To evaluate the correlation between avascular necrosis (AVN) and the amount (severity) and direction (translation and angulation) of initial displacement of pediatric femoral neck fractures. METHODS: We retrospectively reviewed 108 pediatric patients (mean age 10.3 ± 4.1 years) with femoral neck fractures. The amount of initial translation (T) and angulation (A) was measured on anteroposterior (AP; TAP% and AAP) and lateral (TL% and AL) radiographs. The direction of translation was determined on AP (medial or lateral) and lateral radiographs (anterior or posterior). Furthermore, the presence of a comminuted medial cortex on the AP pelvis radiograph was also recorded. Logistic regression analysis, receiver operating characteristic (ROC) curve analysis, student's t tests, and chi-square tests were used to evaluate the correlation between AVN and the severity and direction of displacement. RESULTS: Twenty-eight out of 108 hips (25.9%) developed AVN of the femoral head. Logistical regression analysis indicated that TAP%, TL%, AAP, and AL were risk factors for AVN (P < 0.05). The analysis of ROC curves found that TAP% over 37.4% and TL% over 29% were the cut-off values for an increased incidence of AVN; similarly, AAP over 8° and AL over 18.6° were the cut-off values for an increased incidence of AVN. The amount of initial translation is a better predictor of AVN than angulation is; fractures with posterior translation (P = 0.002) and/or medial comminution had a significantly higher incidence of AVN (P = 0.005). The mean diagnostic accuracy of translation (74-75%) was significantly higher than that of angulation (65-66%). CONCLUSIONS: Displacement severity and direction are important radiological parameters to be assessed in children with femoral neck fractures. Initial translation better predicts AVN than angulation does. Posterior translation and medial comminution are associated with an increased risk of AVN.

Risk factors for the development of avascular necrosis after femoral neck fractures in children: a review of 239 cases.

AIMS: The aim of this study was to clarify the factors that predict the development of avascular necrosis (AVN) of the femoral head in children with a fracture of the femoral neck. PATIENTS AND METHODS: We retrospectively reviewed 239 children with a mean age of 10.0 years (sd 3.9) who underwent surgical treatment for a femoral neck fracture. Risk factors were recorded, including age, sex, laterality, mechanism of injury, initial displacement, the type of fracture, the time to reduction, and the method and quality of reduction. AVN of the femoral head was assessed on radiographs. Logistic regression analysis was used to evaluate the independent risk factors for AVN. Chi-squared tests and Student's t-tests were used for subgroup analyses to determine the risk factors for AVN. RESULTS: We found that age (p = 0.006) and initial displacement (p = 0.001) were significant independent risk factors. Receiver operating characteristic (ROC) curve analysis indicated that 12 years of age was the cut-off for increasing the rate of AVN. Severe initial displacement (p = 0.021) and poor quality of reduction (p = 0.022) significantly increased the rate of AVN in patients aged 12 years or greater, while in those aged less than 12 years, the rate of AVN significantly increased only with initial displacement (p = 0.048). A poor reduction significantly increased the rate of AVN in patients treated by closed reduction (p = 0.026); screw and plate fixation was preferable to cannulated screw or Kirschner wire (K-wire) fixation for decreasing the rate of AVN in patients treated by open reduction (p = 0.034). CONCLUSION: The rate of AVN increases with age, especially in patients aged 12 years or greater, and with the severity of displacement. In patients treated by closed reduction, anatomical reduction helps to decrease the rate of AVN, while in those treated by open reduction, screw and plate fixation was preferable to fixation using cannulated screws or K-wires. Cite this article: Bone Joint J 2019;101-B:1160-1167.

Traction does not decrease failure of reduction and femoral head avascular necrosis in patients aged 6-24 months with developmental dysplasia of the hip treated by closed reduction: a review of 385 patients and meta-analysis.

This study aimed to investigate the effects of preliminary traction on the rate of failure of reduction and the incidence of femoral head avascular necrosis (AVN) in patients with late-detected developmental dysplasia of the hip treated by closed reduction. A total of 385 patients (440 hips) treated by closed reduction satisfied the inclusion criteria. Patients were divided in two groups according to treatment modality: a traction group (276 patients) and a no-traction group (109 patients). Tönnis grade, rate of failure reduction, AVN rate, acetabular index, center-edge angle of Wiberg, and Severin's radiographic grade were assessed on plain radiographs, and the results were compared between the two groups of patients. In addition, a meta-analysis was performed based on the existing comparative studies to further evaluate the effect of traction on the incidence of AVN. Tönnis grade in the traction group was significantly higher than in the no-traction group (P = 0.021). The overall rate of failure reduction was 8.2%; no significant difference was found between the traction (9.2%) and no-traction groups (5.6%) (P = 0.203). The rates of failure reduction were similar in all Tönnis grades, regardless of treatment modality (P > 0.05). The rate of AVN in the traction group (14%) was similar to that of the no-traction group (14.5%; P = 0.881). Moreover, the rates of AVN were similar in all Tönnis grades, regardless of treatment modality (P > 0.05). The meta-analysis did not identify any significant difference in the AVN rate whether preliminary traction was used or not (odds ratio = 0.76, P = 0.32). At the last follow-up visit, the two groups of patients had comparable acetabular indices, center-edge angles, and Severin's radiographic grades (P > 0.05). In conclusion, preliminary traction does not decrease the failure of reduction and the incidence of AVN in developmental dysplasia of the hip treated by closed reduction between 6 and 24 months of age.

Comparison of different noninvasive diagnostic methods for biliary atresia: a meta-analysis.

BACKGROUND: This study was undertaken to retrospectively analyze the accuracy of different methods in differentiating biliary atresia from neonatal jaundice. METHODS: A search was made in MEDLINE, and the Web of Science for relevant original articles published in English; methodological quality of the included studies was also assessed. Two reviewers extracted data independently. Studies were pooled, summary receiver operating characteristics curve and diagnostic odds ratio (DOR) with corresponding confidence intervals were calculated. RESULTS: For diagnosis of biliary atresia, ultrasonography (US), hepatic scintigraphy (HBS), and magnetic resonance cholangiography (MRCP) had a pooled sensitivity of 74.9% (range: 70.4%-79.1%), 93.4% (range: 90.3%-95.7%) and 89.7% (range: 84.8%-93.4%), a specificity of 93.4% (range: 91.4%-95.1%), 69.2% (range: 65.1%-73.1%) and 64.7% (range: 58.0%-71.0%), a positive likelihood ratio of 12.16 (range: 6.41-23.08), 3.01 (range: 2.15-4.20) and 3.10 (range: 1.59-6.06), a negative likelihood ratio of 0.23 (range: 0.13-0.38), 0.13 (range: 0.06-0.25) and 0.16 (range: 0.06-0.44), DOR of 72.56 (range: 27.34-192.58), 29.88 (range: 12.82-69.64) and 32.48 (range: 8.22-128.29), with an area under the curve of 0.96, 0.91, and 0.92, and Q value of 0.90, 0.85, and 0.85, respectively. CONCLUSIONS: US, HBS and MRCP can be very useful for the diagnostic work-up of neonatal cholestasis. To improve the sensitivity and specificity, several additional measures can be used.

[APPLICATION OF DIGITAL PLANNING WITH BONE PARAMETERS IN DETERMINING OPTIMAL SIZE OF PROSTHESIS].

OBJECTIVE: To investigate the accuracy and value of digital planning with bone parameters in determining the appropriate prosthesis for total hip arthroplasty (THA). METHODS: The preoperative radiographs was taken in 13 cases scheduled for THA between September 2012 and June 2013; the bone parameters were measured by digital template, and the prosthesis was selected and preoperative plan was made. There were 4 males and 9 females with an average age of 54.08 years (range, 41-79 years), including 8 left hips and 5 right hips. The causes were osteonecrosis of the femoral head in 8 cases and femoral neck fracture in 5 cases (3 cases had osteonecrosis of the femoral head). RESULTS: The operation time was 140-254 minutes (mean, 191.8 minutes). Two cases received blood transfusion, and 6 patients received plasma substitutes transfusion. There was no intraoperative fractures or postoperative thrombosis; atherosclerotic plaque occurred in 2 cases. Thirteen cases were followed up 12-24 months with an average of 17.3 months. The pain was relieved and limb function was improved in all patients. Harris score was significantly improved from preoperative 54.0 ± 12.9 to 91.1 ± 4.1 at 3 months after operation (t = 7.259, P = 0.000). Compared with the actual implants, the appropriate sizes of femoral stem was selected in 12 cases (92.31%) (excellent in 9 cases, good in 3 cases, and poor in 1 case), and the appropriate sizes of acetabular cup was selected in 11 cases (84.62%) (excellent in 7 cases, good in 4 cases, and poor in 2 cases). CONCLUSION: Digital planning could increase the accuracy in choosing the size of prosthesis for THA.

Review of the molecular pathogenesis of osteosarcoma.

Treating the osteosarcoma (OSA) remains a challenge. Current strategies focus on the primary tumor and have limited efficacy for metastatic OSA. A better understanding of the OSA pathogenesis may provide a rational basis for innovative treatment strategies especially for metastases. The aim of this review is to give an overview of the molecular mechanisms of OSA tumorigenesis, OSA cell proliferation, apoptosis, migration, and chemotherapy resistance, and how improved understanding might contribute to designing a better treatment target for OSA.

[Treatment of severe displaced proximal humeral fractures with titanium elastic nails in older children].

OBJECTIVE: To evaluate the effectiveness of titanium elastic nails for severe displaced proximal humeral fractures in older children. METHODS: Between April 2009 and July 2012, 31 cases of severe displaced proximal humeral fractures were treated with closed or open reduction and fixation with 2 titanium elastic nails, and the clinical data were retrospectively analyzed. There were 23 boys and 8 girls, aged from 10 to 15 years (mean, 12.8 years). The causes of injury were sports injury (16 cases), traffic accident (11 cases), and falling from height (4 cases). The interval from injury to operation was 6 hours to 7 days (mean, 72 hours). According to Neer-Horwitz classification, 17 cases were rated as type III fracture and 14 cases as type IV fracture. There were 21 cases of metaphyseal fractures and 10 cases of epiphyseal fractures. RESULTS: Satisfactory reduction of fracture and stable fixation were obtained in all patients (closed reduction in 23 cases and open reduction in 8 cases). Primary healing was achieved in all incisions; no infection and neurovascular injury occurred. All patients were followed up 12-36 months with an average of 20 months. X-ray films showed that all fractures healed at 7-10 weeks (mean, 8 weeks). During follow-up, no disturbance of development or angulation deformity caused by premature physeal closure or bone bridge formation was observed. At last follow-up, the average Neer score of the shoulder was 95.7 (range, 83-100). The appearance and motion of the shoulder were normal. There was no significant difference in the upper extremity length between affected side and contralateral side [(67.68 +/- 2.56) cm vs. (67.61 +/- 2.54) cm; t = 1.867, P = 0.072]. CONCLUSION: Titanium elastic nails for severe displaced humeral fractures in older children is a safe and effective method with a low complication incidence.

Closed/open reduction and titanium elastic nails for severely displaced proximal humeral fractures in children.

PURPOSE: The aim of the study was to evaluate the clinical outcome of closed/open reduction and titanium elastic nails (TENs) in children with severely displaced proximal humeral fractures. METHODS: A retrospective study was performed on 37 children suffering from proximal humeral fracture between April 2009 and July 2012. All these patients were treated by closed or open reduction with TEN fixation. The healing process was assessed by radiographic and clinical follow-up for up to 36 months. Radiographic assessment was performed on the scheduled follow-ups to examine fracture healing, remodelling, bone growth and residual deformity. The clinical outcomes were evaluated using the Neer shoulder score and patients' satisfaction report at the final follow-up. Complications related to the treatment were also recorded. RESULTS: All patients had a mean follow-up period of 24 months (12-36) after surgery. All fractures were healed, radiologically, at a median time of eight weeks (seven to ten weeks). There were no major complications related to the treatment. Two patients complained about skin irritation around the sides of the prominent distal ends of the nails. Implant removal took place at an average of 5.8 months post-operatively as an outpatient procedure. There were no observed complications in association with the removal of the hardware. At the final follow-up, the mean Neer shoulder score was 96.65 (range 83-100). Thirty patients were very satisfied with their surgical outcomes and the remaining seven were satisfied. Function of the affected arm returned to normal at the end of the follow-up period in all cases. CONCLUSIONS: Combining closed or open reduction with TEN fixation is recommended for treating severely displaced proximal humeral fractures in children. Our data showed evidence of satisfactory outcomes with a low complication rate and a fast return to normal mobility of the affected arms.

Regulation of PTHrP expression by cyclic mechanical strain in postnatal growth plate chondrocytes.

Mechanical loading has been widely considered to be a crucial regulatory factor for growth plate development, but the exact mechanisms of this regulation are still not completely understood. In the growth plate, parathyroid hormone-related protein (PTHrP) regulates chondrocyte differentiation and longitudinal growth. Cyclic mechanical strain has been demonstrated to influence growth plate chondrocyte differentiation and metabolism, whereas the relationship between cyclic mechanical strain and PTHrP expression is not clear. The objective of this study was to investigate whether short-term cyclic tensile strain regulates PTHrP expression in postnatal growth plate chondrocytes in vitro and to explore whether the organization of cytoskeletal F-actin microfilaments is involved in this process. To this end, we obtained growth plate chondrocytes from 2-week-old Sprague-Dawley rats and sorted prehypertrophic and hypertrophic chondrocytes using immunomagnetic beads coated with anti-CD200 antibody. The sorted chondrocytes were subjected to cyclic tensile strain of varying magnitude and duration at a frequency of 0.5 Hz. We found that cyclic strain regulates PTHrP expression in a magnitude- and time-dependent manner. Incubation of chondrocytes with cytochalasin D, an actin microfilament-disrupting reagent, blocked the induction of PTHrP expression in response to strain. The results suggest that short-term cyclic tensile strain induces PTHrP expression in postnatal growth plate prehypertrophic and hypertrophic chondrocytes and that PTHrP expression by these chondrocytes may subsequently affect growth plate development. The results also support the idea that the organization of cytoskeletal F-actin microfilaments plays an important role in mechanotransduction.

Effects of verapamil on the immediate-early gene expression of bone marrow mesenchymal stem cells stimulated by mechanical strain in vitro.

BACKGROUND: To study the effects of verapamil on the immediate-early genes (IEGs) expression of bone marrow mesenchymal stem cells (MSCs) stimulated by cyclic mechanical strain, in order to deduce the role of calcium ion channel in the cell signaling responses of MSCs to mechanical strain. MATERIAL AND METHODS: MSCs were isolated and cultured, and the passage of 3-6 MSCs were stimulated by mechanical strain and pretreated with or without verapamil. After that, flow cytometry was used to measure the fluorescence intensity of intracellular Ca(2+) immediately. The expression of early-response genes/proteins (c-fos, c-jun and c-myc) were examined by RT-PCR, immunohistochemistry and Western blot. RESULTS: Intracellular Ca(2+) concentration of MSCs significantly changed when stimulated by cyclic strain, and the expression of c-fos, c-jun and c-myc remarkably increased in both mRNA and protein levels, while verapamil pre-treatment partially inhibited these effects (P<0.01). CONCLUSIONS: The changes of the intracellular calcium concentration of MSCs induced by mechanical strain, dependent on the regulation of calcium channel activation, might play a role in the early response of MSCs to cyclic strain.