CXCR4 mediates the effects of IGF-1R signaling in rodent bone homeostasis and fracture repair.

Non-union fractures have considerable clinical and economic burdens and yet the underlying pathogenesis remains largely undetermined. The fracture healing process involves cellular differentiation, callus formation and remodeling, and implies the recruitment and differentiation of mesenchymal stem cells that are not fully characterized. C-X-C chemokine receptor 4 (CXCR4) and Insulin-like growth factor 1 receptor (IGF-1R) are expressed in the fracture callus, but their interactions still remain elusive. We hypothesized that the regulation of CXCR4 by IGF-1R signaling is essential to maintain the bone homeostasis and to promote fracture repair. By using a combination of in vivo and in vitro approaches, we found that conditional ablation of IGF-1R in osteochondroprogenitors led to defects in bone formation and mineralization that associated with altered expression of CXCR4 by a discrete population of endosteal cells. These defects were corrected by AMD3100 (a CXCR4 antagonist). Furthermore, we found that the inducible ablation of IGF-1R in osteochondroprogenitors led to fracture healing failure, that associated with an altered expression of CXCR4. In vivo AMD3100 treatment improved fracture healing and normalized CXCR4 expression. Moreover, we determined that these effects were mediated through the IGF-1R/Insulin receptor substrate 1 (IRS-1) signaling pathway. Taken together, our studies identified a novel population of endosteal cells that is functionally regulated through the modulation of CXCR4 by IGF-1R signaling, and such control is essential in bone homeostasis and fracture healing. Knowledge gained from these studies has the potential to accelerate the development of novel therapeutic interventions by targeting CXCR4 signaling to treat non-unions.

A randomised placebo-controlled clinical trial on the efficacy of local lidocaine injections and oral citalopram for the treatment of complex regional pain syndrome.

BACKGROUND: Complex regional pain syndrome (CRPS) is a neuropathic pain condition with no universally recognised treatment. The study evaluates the efficacy of a therapeutic protocol consisting of oral citalopram and lidocaine injections in patients affected by CRPS. METHODS: Between January 2010 and December 2014, 150 consecutive patients with CRPS were enrolled in the study and randomly assigned into three groups: group one - lidocaine injection and oral citalopram; group two - lidocaine injection and oral placebo; and group three - injective and oral placebo. The Impairment Sum Score (ISS) was used to assess the severity of CRPS before, as well as at regular intervals after treatment commenced. Statistical significance (p < 0.05) was determined by paired t-tests. RESULTS: The combined treatment proved to be more effective (ISS 47.6 to 12.6) than local anaesthetic alone (ISS 47.5 to 21.5) and to placebo (ISS 47.2 to 29.9). CONCLUSION: This study indicates that CRPS may be managed with well-tolerated association of oral citalopram and lidocaine injections.

Rates, Risks, and Time to Fracture in Patients Undergoing Laparoscopic Vertical Sleeve Gastrectomy versus Roux-en-Y Gastric Bypass.

Objective: To assess the rates, risks, and time to fracture in patients undergoing laparoscopic vertical sleeve gastrectomy (VSG) versus those undergoing Roux-en-Y gastric bypass (RYGB). Summary Background Data: Metabolic and bariatric surgery has been implicated in significant bone loss and may increase fracture risk. Preoperative patient characteristics that might impact fracture risk and the time to fractures have not been established. Furthermore, the patient characteristics that might impact fracture risk and the time to fractures by surgical approach are unknown. Methods: This population-based retrospective cohort analysis used Humana claims data from January 1, 2007 to March 31, 2017, and included 4073 patients undergoing laparoscopic RYGB and VSG as a first surgical intervention for weight loss. The primary outcomes were the incidence of fractures (Humeral, Radial or Ulnar, Pelvic, Hip, and Vertebral) within 48 months after laparoscopic VSG versus RYGB and days to these fractures. Results: An analysis of total fractures (odds ratio [OR] 0.53; 95% confidence interval [CI], 0.38-0.73), vertebral fractures (OR 0.61; 95% CI, 0.38-0.99), hip fractures (OR 0.36; 95% CI, 0.15-0.84), and humeral fractures (OR 0.44; 95% CI, 0.22-0.90) demonstrated a reduction in fracture risk in patients undergoing VSG versus RYGB. Furthermore, postmenopausal status was independently associated with increased odds of total fractures and hip fractures (OR 2.18; 95% CI, 1.06-4.50; OR 5.83; 95% CI, 1.16-29.27; respectively). Likewise, osteoporosis at the time of surgery was associated with increased odds of total fractures (OR 1.61; 95% CI, 1.09-2.37), vertebral fractures (OR 2.01; 95% CI, 1.19-3.39), and hip fractures (OR 2.38; 95% CI, 1.19-4.77). Except for a significantly decreased odds of vertebral fractures in osteoporotic patients undergoing VSG versus RYGB (OR 0.41; 95% CI, 0.18-0.95), osteoporotic or postmenopausal status at the time of surgery was not found to increase odds of fracture depending on surgical intervention. However, time to fracture (total) and for all site-specific fractures, except for pelvic fractures, was significantly reduced in postmenopausal women undergoing RYGB versus VSG. Time to fracture (total) and for all site-specific fractures except pelvic and radial or ulnar fractures was significantly reduced in osteoporotic patients undergoing RYGB versus VSG. Conclusions and Relevance: Though bariatric surgery is associated with several health-related benefits, increased fracture risk is an important factor to discuss with patients undergoing bariatric surgery. Bariatric surgery strategy, RYGB versus VSG, carries a differential risk of fracture, with RYGB carrying a higher risk of fracture and decreased time to fracture. Furthermore, patients who are postmenopausal or osteoporotic at the time of surgery carry an increased risk of total fractures, independent of bariatric surgery strategy. Being mindful of patient-specific fracture risk after bariatric surgery may help anticipate, identify, and prevent fractures.

Roux-en-Y gastric bypass decreases serum inflammatory markers and cardiovascular risk factors in obese diabetics.

BACKGROUND: Obesity and type 2 diabetes mellitus are associated with elevated levels of inflammatory markers. This chronic inflammation is known to contribute to increased risk of cardiovascular disease in these populations. Laparoscopic Roux-en-Y gastric bypass is associated with a high rate of diabetes remission. We hypothesize that laparoscopic Roux-en-Y gastric bypass decreases systemic inflammatory markers and cardiovascular disease risk factors in obese diabetics. METHODS: This was a single-institution prospective cohort study of 61 obese patients with type 2 diabetes mellitus. A total of 30 patients underwent laparoscopic Roux-en-Y gastric bypass surgery, and 31 patients underwent standard medical therapy with diabetes support and education. Collected data included preoperative and postoperative inflammatory biomarkers and clinical parameters. RESULTS: Twelve months after undergoing laparoscopic Roux-en-Y gastric bypass, controlling for sex and age, there was a significant correlation between a change in interleukin-6 and a change in systolic blood pressure (Spearman r = 0.41, P = .03). Similarly, when sex and age were controlled for in the laparoscopic Roux-en-Y gastric bypass group, a statistically significant relationship remained between percent excess weight loss and change in interleukin-6 (P = .001). CONCLUSION: A significant relationship exists between decreased systemic interleukin-6 levels and both excess weight loss and lowered systolic blood pressure after laparoscopic Roux-en-Y gastric bypass in obese patients with diabetes mellitus. These correlations may explain the decreased risk of cardiovascular disease after surgical weight reduction in this patient population.

Role of Prx1-expressing skeletal cells and Prx1-expression in fracture repair.

The healing capacity of bones after fracture implies the existence of adult regenerative cells. However, information on identification and functional role of fracture-induced progenitors is still lacking. Paired-related homeobox 1 (Prx1) is expressed during skeletogenesis. We hypothesize that fracture recapitulates Prx1's expression, and Prx1 expressing cells are critical to induce repair. To address our hypothesis, we used a combination of in vivo and in vitro approaches, short and long-term cell tracking analyses of progenies and actively expressing cells, cell ablation studies, and rodent animal models for normal and defective fracture healing. We found that fracture elicits a periosteal and endosteal response of perivascular Prx1+ cells that participate in fracture healing and showed that Prx1-expressing cells have a functional role in the repair process. While Prx1-derived cells contribute to the callus, Prx1's expression decreases concurrently with differentiation into cartilaginous and bone cells, similarly to when Prx1+ cells are cultured in differentiating conditions. We determined that bone morphogenic protein 2 (BMP2), through C-X-C motif-ligand-12 (CXCL12) signaling, modulates the downregulation of Prx1. We demonstrated that fracture elicits an early increase in BMP2 expression, followed by a decrease in CXCL12 that in turn down-regulates Prx1, allowing cells to commit to osteochondrogenesis. In vivo and in vitro treatment with CXCR4 antagonist AMD3100 restored Prx1 expression by modulating the BMP2-CXCL12 axis. Our studies represent a shift in the current research that has primarily focused on the identification of markers for postnatal skeletal progenitors, and instead we characterized the function of a specific population (Prx1+ cells) and their expression marker (Prx1) as a crossroad in fracture repair. The identification of fracture-induced perivascular Prx1+ cells and regulation of Prx1's expression by BMP2 and in turn by CXCL12 in the orchestration of fracture repair, highlights a pathway in which to investigate defective mechanisms and therapeutic targets for fracture non-union.

Association of Bariatric Surgery With Risk of Fracture in Patients With Severe Obesity.

Importance: Given the complex relationship between body mass index, body composition, and bone density and the correlative nature of the studies that have established the prevailing notion that higher body mass indices may be protective against osteopenia and osteoporosis and, therefore, fracture, the absolute risk of fracture in patients with severe obesity who undergo either Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) compared with those who do not undergo bariatric surgery is unknown. Objective: To assess the rates of fractures associated with obesity and compare rates between those who do not undergo bariatric surgery, those who undergo RYGB, and those who undergo SG. Design, Setting, and Participants: In this retrospective multicenter cohort study of Medicare Standard Analytic Files derived from Medicare parts A and B records from January 2004 to December 2014, patients classified as eligible for bariatric surgery using the US Centers of Medicare & Medicaid criteria who either did not undergo bariatric surgery or underwent RYGB or SG were exactly matched in a 1:1 fashion based on their age, sex, Elixhauser Comorbidity Index, hypertension, smoking status, nonalcoholic fatty liver disease, hyperlipidemia, type 2 diabetes, osteoporosis, osteoarthritis, and obstructive sleep apnea status. Data were analyzed from November to December 2019. Exposures: RYGB or SG. Main Outcomes and Measures: The primary outcome measured in this study was the odds of fracture overall based on exposure to bariatric surgery. Secondary outcomes included the odds of type of fracture (humerus, radius or ulna, pelvis, hip, vertebrae, and total fractures) based on exposure to bariatric surgery. Results: A total of 49 113 patients were included and were equally made up of 16 371 bariatric surgery-eligible patients who did not undergo weight loss surgery, 16 371 patients who had undergone RYGB, and 16 371 patients who had undergone SG. Each group consisted of an equal number of 4109 men (25.1%) and 12 262 women (74.9%) and had an equal distribution of ages, with 11 780 patients (72.0%) 64 years or younger, 4230 (25.8%) aged 65 to 69 years, 346 (2.1%) aged 70 to 74 years, and 15 (0.1%) aged 75 to 79 years. Patients undergoing RYGB were found to have no significant difference in odds of fractures compared with bariatric surgery-eligible patients who did not undergo surgery. Patients undergoing undergone SG were found to have decreased odds of fractures of the humerus (odds ratio [OR], 0.57; 95% CI, 0.45-0.73), radius or ulna (OR, 0.38; 95% CI, 0.25-0.58), hip (OR, 0.49; 95% CI, 0.33-0.74), pelvis (OR, 0.34; 95% CI, 0.18-0.64), vertebrae (OR, 0.60; 95% CI, 0.48-0.74), or fractures in general (OR, 0.53; 95% CI, 0.46-0.62). Compared with patients undergoing SG, patients undergoing RYGB had a significantly greater risk of total fractures (OR, 1.79; 95% CI, 1.55-2.06) and humeral fractures (OR, 1.60; 95% CI, 1.24-2.07). Conclusions and Relevance: In this cohort study, bariatric surgery was associated with a reduced risk of fracture in bariatric surgery-eligible patients. Sleeve gastrectomy might be the best option for weight loss in patients in which fractures could be a concern, as RYGB may be associated with an increased fracture risk compared with SG.

Effects of Roux-en-Y Gastric Bypass on Osteoclast Activity and Bone Density in Morbidly Obese Patients with Type 2 Diabetes.

INTRODUCTION: Roux-en-Y gastric bypass (RYGB) is a well-established treatment for morbid obesity and type 2 diabetes. The effects of RYGB on bone metabolism and bone health are largely unknown. OBJECTIVE: Determine the changes in osteoclast function and bone density 1 year after RYGB as compared with a control group undergoing a diabetes support and education program (DSE). DESIGN: A prospective cohort study with patients matched for weight and age assigned to RYGB or DSE. SETTING: Large academic institution. PATIENTS OR OTHER PARTICIPANTS: Patients with type 2 diabetes mellitus and morbid obesity (body mass index greater than 35 kg/m2). INTERVENTION: Subjects either received laparoscopic RYBG or DSE, which consisted of nutritional, exercise, and dietary counseling performed by a certified diabetic educator and a nutritionist three times over a year. MAIN OUTCOME MEASURE: Osteoclast activity, bone mineral density. RESULTS: One year after, intervention subjects undergoing RYGB have a 280% increase in osteoclast activity as compared with a 7.6% increase in the DSE control group (P < 0.001). Furthermore, there was a statistically significant increase in sclerostin levels in subjects undergoing RYGB compared with an increase in the control group. The total bone mineral density was statistically unchanged within 1 year of intervention in both groups. A statistically significant decrease in bone mineral density in the left ribs (decrease of 6.8%, P < 0.05) and lumbar spine (decrease of 4.0%, P < 0.05) was seen 1 year after RYGB. CONCLUSIONS: There is a significant increase in osteoclast activity observed 1 year after RYGB; the long-term clinical implications of this increased bone metabolism are unknown.

Perioperative changes in prouroguanylin hormone response in severely obese subjects after bariatric surgery.

BACKGROUND: Prouroguanylin is a gut hormone converted into uroguanylin in the hypothalamus. Uroguanylin induces satiety through guanylyl-cyclase-2C receptor signaling. However, little is known about the role of this hormone in regulating human food intake. METHODS: In prospective-cohort study, prouroguanylin profile changes were determined during meal stimulation in obese patients 2 weeks before and 2 weeks after Roux-en-Y gastric bypass surgery. We also investigated whether these changes play a role in the anorexigenic effect of Roux-en-Y gastric bypass. RESULTS: The study enrolled 8 healthy lean volunteers and 10 obese patients with type 2 diabetes. Prouroguanylin levels were postprandially decreased at 30 minutes (P = .04) and 60 minutes (P = .008) in obese patients before surgery, and they were increased at 60 minutes (P = .003), 90 minutes (P = .008), and 120 minutes (P = .009) after surgery. We observed a significant difference (P = .001) in fasting prouroguanylin levels before (8.82 ± 1.2 ng/mL) and after (6.05 ± 1.2 ng/mL) Roux-en-Y gastric bypass. Hunger ratings in the fasted state did not change after Roux-en-Y gastric bypass. Instead, subjects demonstrated significantly (P = .01) lower hunger visual analog scale scores than before Roux-en-Y gastric bypass. No correlations between circulating prouroguanylin levels and hunger perception were found before or after Roux-en-Y gastric bypass. CONCLUSION: Prouroguanylin levels decrease after meal stimulation in obese patients, and they increase after Roux-en-Y gastric bypass, but no correlations exist with hunger visual analog scale scores.

Tissue engineering a tendon-bone junction with biodegradable braided scaffolds.

BACKGROUND: Tendons play an important role in transferring stress between muscles and bones and in maintaining the stability of joints. Tendon tears are difficult to heal and are associated with high recurrence rates. So, the objective of this study was to develop a biodegradable scaffold for tendon-bone junction regeneration. METHODS: Two types of polylactic acid (PLA) yarns, having fibers with round and four deep grooved cross-sections, were braided into tubular scaffolds and cultured with murine Transforming growth factor beta type II receptor (Tgfbr2)-expressing joint progenitor cells. The scaffolds were designed to mimic the mechanical, immuno-chemical and biological properties of natural mouse tendon-bone junctions. Three different tubular scaffolds measuring 2 mm in diameter were braided on a Steeger 16-spindle braiding machine and biological and mechanical performance of the three scaffolds were evaluated. RESULTS: The mechanical test results indicated that three different braided scaffold structures provided a wide range of mechanical properties that mimic the components of tendon bone junction and results of the biological tests confirmed cell viability, active cell attachment and proliferation throughout all three scaffolds. CONCLUSIONS: This study has identified that the three proposed types of braided scaffolds with some improvement in their structures have the potential to be used as scaffolds for the regeneration of a tendon bone tissue junction.

TGF-ß type 2 receptor-mediated modulation of the IL-36 family can be therapeutically targeted in osteoarthritis.

Mechanisms that govern the shift from joint homeostasis to osteoarthritis (OA) remain unknown. Here, we identify a pathway used for joint development and homeostasis, and its role in OA. Using a combination of transgenic, pharmacological, and surgical conditions in mouse and human tissues, we found that TGF-ß signaling promotes joint homeostasis through regulation of the IL-36 family. We identified IL-36 receptor antagonist (IL-36 in mice and IL-36RN in humans) as a potential disease-modifying OA drug. Specifically, OA development was associated with IL-36α up-regulation and IL-36Ra down-regulation in mice with tissue-specific postnatally induced ablation of Tgfbr2, mice treated with a TGF-ß signaling inhibitor, mice with posttraumatic OA, and aging mice with naturally occurring OA. In human cartilage, OA severity was associated with decreased TGFBR2 and IL-36RN, whereas IL-36α increased. Functionally, intra-articular treatment with IL-36Ra attenuated OA development in mice, and IL-36RN reduced MMP13 in human OA chondrocytes. These findings highlight the relevance of TGFBR2-IL-36 interplay in joint homeostasis and IL-36RN as a potential therapeutic agent for OA.

Wnt signaling in bone, kidney, intestine, and adipose tissue and interorgan interaction in aging.

Over the last two decades, it has become increasingly apparent that Wnt signaling plays a critical role in development and adult tissue homeostasis in multiple organs and in the pathogenesis of many diseases. In particular, a crucial role for Wnt signaling in bone development and bone tissue homeostasis has been well recognized. Numerous genome-wide association studies confirmed the importance of Wnt signaling in controlling bone mass. Moreover, ample evidence suggests that Wnt signaling is essential for kidney, intestine, and adipose tissue development and homeostasis. Recent emerging evidence demonstrates that Wnt signaling may play a fundamental role in the aging process of those organs. New discoveries show that bone is not only the major reservoir for calcium and phosphate storage, but also the largest organ with multiple functions, including mineral and energy metabolism. The interactions among bone, kidney, intestine, and adipose tissue are controlled and regulated by several endocrine signals, including FGF23, klotho, sclerostin, osteocalcin, vitamin D, and leptin. Since the aging process is characterized by structural and functional decline in almost all tissues and organs, understanding the Wnt signaling-related interactions among bone, kidney, intestine, and adipose tissue in aging may shed light on the pathogenesis of age-related diseases.

Bifid median nerve and carpal tunnel syndrome: an uncommon anatomical variation.

Dear sir, one of the most common entrapment neuropathy syndromes in clinical practice is "Entrapment of median nerve in carpal tunnel" also called "Carpal tunnel syndrome (CTS)" (Aydin et al., 2007; Huisstede et al., 2010). This syndrome is caused by entrapment of the median nerve in the wrist (Preston and Shapiro, 2005) when the pressure increases in the carpal tunnel. A high division of the median nerve proximal to the carpal tunnel, also known as a bifid median nerve, is a rare anatomic variation that may be associated with CTS and with persistent median vessels (Lanz, 1977). This anatomic variation has an incidence of 0,8% to 2,3% in patients with CTS. Lanz (1977) has characterized this anatomic condition of the median nerve in the carpal tunnel. These anatomic variants have been classified into four groups: - Group 0: extraligamentous thenar branch (standard anatomy); - Group 1: variations of the course of the thenar branch; - Group 2: accessory branches at the distal portion of the carpal tunnel; - Group 3: divided or duplicated median nerve inside the carpal tunnel; - Group 4: accessory branches proximal to the carpal tunnel. During dissection of the wrist performed for the treatment of a CTS under local anesthesia, we found an anatomical variation of the median nerve that was divided in two branches inside the carpal tunnel (Group 3 of Lanz Classification) and in which its radial branch passed through its own compartment. The two parts of the nerve seems to be unequal in size (Fig. 1). Moreover the nerve passed in carpal tunnel associated with a median artery, so we classified this variation in the group 3b of Lanz Classification (Fig. 2). The persistence of median artery coexisting with a bifid median nerve has been widely reported in surgical literature (Lanz, 1977; Barbe et al., 2005). Before surgical intervention clinical evaluation of patient and electrophysiological examination showed no differences compared to a non bifid median nerve entrapment syndrome. In conclusion the bifid median nerve may facilitate compression of median nerve in the carpal tunnel because of its increased cross sectional area even if it has no electrophysiological or clinical differential diagnosis in case of CTS. The aim of this letter is aware the physicians in order to borne in mind the possible presence of a median nerve variation during dissection of carpal tunnel in order to avoid the damage of this non common anatomical structures.

Extracorporeal Shock Wave Therapy: An Emerging Treatment Modality for Retracting Scars of the Hands.

Prolonged and abnormal scarring after trauma, burns and surgical procedures often results in a pathologic scar. We evaluated the efficacy of unfocused shock wave treatment, alone or in combination with manual therapy, on retracting scars on the hands. Scar appearance was assessed by means of the modified Vancouver Scar Scale; functional hand mobility was evaluated using a range-of-motion scale, whereas a visual analogue score was implemented for detecting any improvements in referred pain. Additionally, biopsy specimens were collected for clinico-pathologic correlation. For each active treatment group, statistically significant improvements in modified Vancouver Scar Scale were recorded as early as five treatment sessions and confirmed 2 wk after the last treatment session. Analogous results were observed when assessing pain and range of movement. Histopathological examination revealed significant increases in dermal fibroblasts in each active treatment group, as well as in neoangiogenetic response and type-I collagen concentration.

BMP2 Regulation of CXCL12 Cellular, Temporal, and Spatial Expression is Essential During Fracture Repair.

The cellular and humoral responses that orchestrate fracture healing are still elusive. Here we report that bone morphogenic protein 2 (BMP2)-dependent fracture healing occurs through a tight control of chemokine C-X-C motif-ligand-12 (CXCL12) cellular, spatial, and temporal expression. We found that the fracture repair process elicited an early site-specific response of CXCL12(+)-BMP2(+) endosteal cells and osteocytes that was not present in unfractured bones and gradually decreased as healing progressed. Absence of a full complement of BMP2 in mesenchyme osteoprogenitors (BMP2(cKO/+)) prevented healing and led to a dysregulated temporal and cellular upregulation of CXCL12 expression associated with a deranged angiogenic response. Healing was rescued when BMP2(cKO/+) mice were systemically treated with AMD3100, an antagonist of CXCR4 and agonist for CXCR7 both receptors for CXCL12. We further found that mesenchymal stromal cells (MSCs), capable of delivering BMP2 at the endosteal site, restored fracture healing when transplanted into BMP2(cKO/+) mice by rectifying the CXCL12 expression pattern. Our in vitro studies showed that in isolated endosteal cells, BMP2, while inducing osteoblastic differentiation, stimulated expression of pericyte markers that was coupled with a decrease in CXCL12. Furthermore, in isolated BMP2(cKO/cKO) endosteal cells, high expression levels of CXCL12 inhibited osteoblastic differentiation that was restored by AMD3100 treatment or coculture with BMP2-expressing MSCs that led to an upregulation of pericyte markers while decreasing platelet endothelial cell adhesion molecule (PECAM). Taken together, our studies show that following fracture, a CXCL12(+)-BMP2(+) perivascular cell population is recruited along the endosteum, then a timely increase of BMP2 leads to downregulation of CXCL12 that is essential to determine the fate of the CXCL12(+)-BMP2(+) to osteogenesis while departing their supportive role to angiogenesis. Our findings have far-reaching implications for understanding mechanisms regulating the selective recruitment of distinct cells into the repairing niches and the development of novel pharmacological (by targeting BMP2/CXCL12) and cellular (MSCs, endosteal cells) interventions to promote fracture healing.

Synovial joints: from development to homeostasis.

Synovial joint morphogenesis occurs through the condensation of mesenchymal cells into a non-cartilaginous region known as the interzone and the specification of progenitor cells that commit to the articular fate. Although several signaling molecules are expressed by the interzone, the mechanism is poorly understood. For treatments of cartilage injuries, it is critical to discover the presence of joint progenitor cells in adult tissues and their expression gene pattern. Potential stem cell niches have been found in different joint regions, such as the surface zone of articular cartilage, synovium, and groove of Ranvier. Inherited joint malformations as well as joint-degenerating conditions are often associated with other skeletal defects and may be seen as the failure of morphogenic factors to establish the correct microenvironment in cartilage and bone. Therefore, exploring how joints form can help us understand how cartilage and bone are damaged and develop drugs to reactivate this developing mechanism.

Are HDL levels lower in children with type 1 diabetes and concurrent celiac disease compared with children with type 1 diabetes only?

Celiac disease (CD) is associated with type 1 diabetes mellitus (T1DM), which is known to be associated with abnormal lipid profiles. We aimed to examine the impact of CD on lipid profiles in persons with T1DM. Subjects with T1DM were identified by database and medical record review. Patients were classified as T1DM+CD or T1DM based on CD antibody and endoscopy results. The most recent (before age 20 years) non-fasting lipid panel (NFLP) prior to CD diagnosis for T1DM+CD subjects was compared to the most recent NFLP for T1DM subjects. Adjusted analysis showed T1DM+CD had lower HDL compared with T1DM (T1DM+CD 51.4 mg/dL, T1DM 62.2 mg/dL, p=0.017). There were no other differences in NFLP. In our sample, patients with T1DM+CD had lower HDL levels. Considering the increased cardiovascular disease risk of patients with T1DM, those who also have CD may be at even greater risk due to the association with lower HDL.

Expression levels of insulin receptor substrate-1 modulate the osteoblastic differentiation of mesenchymal stem cells and osteosarcoma cells.

The insulin-like growth factor-1 system, including its critical mediator insulin receptor substrate-1 (IRS-1), is involved in regulating osteosarcoma (OS) cell proliferation or differentiation. The aim of this study is to define the role of IRS-1 in OS cells by assessing the contribution of IRS-1 in the differentiation of human and murine OS cell lines and mouse mesenchymal stem cells (MSCs) and found that the basal level of IRS-1 is important for the initiation of differentiation. Both down-regulation and over-expression of IRS-1 inhibited osteoblastic differentiation. In vivo studies showed that OS cells over-expressing IRS-1 have increased metastatic potential and tumor growth. The proteasome inhibitor MG-132 led to an increase in IRS-1 protein level that inhibited osteoblastic differentiation, suggesting a role for proteasomal regulation in maintaining the appropriate expression level of IRS-1. Thus, precise regulation of IRS-1 expression level is critical for determining the differentiating capacity of MSCs and OS cells, and that derangement of IRS-1 levels can be a critical step in OS transformation.

Necdin-E2F4 interaction provides insulin-sensitizing effect after weight loss induced by gastric bypass surgery.

BACKGROUND: The insulin-like growth factor-1 (IGF-1) signaling pathway promotes adipocyte differentiation and, therefore, insulin sensitivity by suppression of necdin expression, which represses peroxisome proliferator-activated receptor-gamma promoter activity by interaction with E2F4 in mouse adipocytes. The aim of the present study was to test the hypothesis that this pathway represents one of the mechanisms by which Roux-en-Y gastric bypass surgery (RYGB) induces resolution of insulin resistance. METHODS: Clinical samples were collected and the key biomarkers measured to test the hypothesis that the IGF-1 pathway represents 1 of the mechanisms by which RYGB induces resolution of insulin resistance in obese individuals. RESULTS: Free IGF-1 levels were significantly greater in the post-RYGB patients than in the pre-RYGB obese patients (2.55 ± 1.54 versus 1.32 ± .65 µg/L, P = .03) and similar to that in normal weight controls (2.54 ± 1.27 µg/L). Necdin and E2F4 gene expression in the adipose tissue was significantly downregulated after RYGB compared with obese and were similar to the levels observed in the controls. In mature human adipocytes cultured in vitro, treatment with des-IGF-1 induced downregulation of necdin and E2F4 gene expression in a dose-dependent manner (P = .01). CONCLUSION: After RYGB, the insulin/IGF-1 signaling pathway is activated and could account for the observed decrease in the expression of necdin, which represses peroxisome proliferator-activated receptor-gamma promoter activity by interaction with E2F4. This could represent one of the mechanisms that induce resolution of insulin resistance after RYGB.

Joint TGF-ß type II receptor-expressing cells: ontogeny and characterization as joint progenitors.

TGF-ß type II receptor (Tgfbr2) signaling plays an essential role in joint-element development. The Tgfbr2(PRX-1KO) mouse, in which the Tgfbr2 is conditionally inactivated in developing limbs, lacks interphalangeal joints and tendons. In this study, we used the Tgfbr2-ß-Gal-GFP-BAC mouse as a LacZ/green fluorescent protein (GFP)-based read-out to determine: the spatial and temporally regulated expression pattern of Tgfbr2-expressing cells within joint elements; their expression profile; and their slow-cycling labeling with bromodeoxyuridine (BrdU). Tgfbr2-ß-Gal activity was first detected at embryonic day (E) 13.5 within the interphalangeal joint interzone. By E16.5, and throughout adulthood, Tgfbr2-expressing cells clustered in a contiguous niche that comprises the groove of Ranvier and the synovio-entheseal complex including part of the perichondrium, the synovium, the articular cartilage superficial layer, and the tendon's entheses. Tgfbr2-expressing cells were found in the synovio-entheseal complex niche with similar temporal pattern in the knee, where they were also detected in meniscal surface, ligaments, and the synovial lining of the infrapatellar fat pad. Tgfbr2-ß-Gal-positive cells were positive for phospho-Smad2, signifying that the Tgfbr2 reporter was accurate. Developmental-stage studies showed that Tgfbr2 expression was in synchrony with expression of joint-morphogenic genes such as Noggin, GDF5, Notch1, and Jagged1. Prenatal and postnatal BrdU-incorporation studies showed that within this synovio-entheseal-articular-cartilage niche most of the Tgfbr2-expressing cells labeled as slow-proliferating cells, namely, stem/progenitor cells. Tgfbr2-positive cells, isolated from embryonic limb mesenchyme, expressed joint progenitor markers in a time- and TGF-ß-dependent manner. Our studies provide evidence that joint Tgfbr2-expressing cells have anatomical, ontogenic, slow-cycling trait and in-vivo and ex-vivo expression profiles of progenitor joint cells.

Comparison of microCT and an inverse finite element approach for biomechanical analysis: results in a mesenchymal stem cell therapeutic system for fracture healing.

An important concern in the study of fracture healing is the ability to assess mechanical integrity in response to candidate therapeutics in small-animal systems. In recent reports, it has been proposed that microCT image-derived densitometric parameters could be used as a surrogate for mechanical property assessment. Recently, we have proposed an inverse methodology that iteratively reconstructs the modulus of elasticity of the lumped soft callus/hard callus region by integrating both intrinsic mechanical property (from biomechanical testing) and geometrical information (from microCT) within an inverse finite element analysis (FEA) to define a callus quality measure. In this paper, data from a therapeutic system involving mesenchymal stem cells is analyzed within the context of comparing traditional microCT densitometric and mechanical property metrics. In addition, a novel multi-parameter regression microCT parameter is analyzed as well as our inverse FEA metric. The results demonstrate that the inverse FEA approach was the only metric to successfully detect both longitudinal and therapeutic responses. While the most promising microCT-based metrics were adequate at early healing states, they failed to track late-stage mechanical integrity. In addition, our analysis added insight to the role of MSCs by demonstrating accelerated healing and was the only metric to demonstrate therapeutic benefits at late-stage healing. In conclusion, the work presented here indicates that microCT densitometric parameters are an incomplete surrogate for mechanical integrity. Additionally, our inverse FEA approach is shown to be very sensitive and may provide a first-step towards normalizing the often challenging process of assessing mechanical integrity of healing fractures.