The Activity of Peptides of the Calcitonin Family in Bone.

Calcitonin was discovered over 50 yr ago as a new hormone that rapidly lowers circulating calcium levels. This effect is caused by the inhibition of calcium efflux from bone, as calcitonin is a potent inhibitor of bone resorption. Calcitonin has been in clinical use for conditions of accelerated bone turnover, including Paget's disease and osteoporosis; although in recent years, with the development of drugs that are more potent inhibitors of bone resorption, its use has declined. A number of peptides that are structurally similar to calcitonin form the calcitonin family, which currently includes calcitonin gene-related peptides (αCGRP and ßCGRP), amylin, adrenomedullin, and intermedin. Apart from being structurally similar, the peptides signal through related receptors and have some overlapping biological activities, although other activities are peptide specific. In bone, in vitro studies and administration of the peptides to animals generally found inhibitory effects on osteoclasts and bone resorption and positive effects on osteoblasts and bone formation. Surprisingly, studies in genetically modified mice have demonstrated that the physiological role of calcitonin appears to be the inhibition of osteoblast activity and bone turnover, whereas amylin inhibits osteoclast activity. The review article focuses on the activities of peptides of the calcitonin family in bone and the challenges in understanding the relationship between the pharmacological effects and the physiological roles of these peptides.

Non-technical skills of Norwegian medical students at different training sites: a comparative, observational cohort study.

PURPOSE: Mastering non-technical skills (NTS) is a fundamental part of the training of new physicians to perform effectively and safely in the medical practice environment. Ideally, they learn these skills during medical school. Decentralized medical education is being implemented increasingly worldwide. Two of the three training sites studied, Bodø (a regional hospital) and Finnmark (a rural local hospital), implemented decentralized medical education. The third training site was the main campus in Tromsø, located at an urban university hospital. The training in Finnmark emphasised training in non-technical skills using simulation to a larger extent than the two other university campuses. This study aimed to compare the NTS performance of medical students in their last year of education at three different training sites of the same university. METHODS: This blinded cohort study included students from the three training sites who participated in identical multi-professional simulations over a six-year period. Eight raters evaluated the video recordings of eight students from each training site using the Norwegian Medical Students Non-Technical Skills (NorMS-NTS) tool. The NorMS-NTS tool, which comprises four categories and 13 elements, assesses the NTS of Norwegian medical students and assigns an overall global score. Pairwise significant differences in the NTS performance levels between the training sites studied were assessed using Tukey's test. RESULTS: The overall NTS performance levels of the medical students from Finnmark (mean 4.5) were significantly higher than those of the students from Tromsø (mean 3.8) and Bodø (mean 3.5). Similarly, the NTS performance levels at category-level of the students in Finnmark were significantly higher than those of the students from Bodø and Tromsø. Except for one category, no significant differences were observed between the students from Bodø and Tromsø in terms of the overall or category-level NTS performance. CONCLUSION: The NTS performance levels of the medical students from Finnmark, which implements rural, decentralized medical education, were significantly higher than those of the students from Tromsø and Bodø.

The development of a tool to assess medical students' non-technical skills - The Norwegian medical students' non-technical skills (NorMS-NTS).

PURPOSE: New physicians need to master non-technical skills (NTS), as high levels of NTS have been shown to increase patient safety. It has also been shown that NTS can be improved through training. This study aimed to establish the necessary NTS for Norwegian medical students to create a tool for formative and summative assessments. METHODS: Focus group interviews were conducted with colleagues and patients of newly graduated physicians. Interviews were then analyzed using card sort methods, and the identified NTS were used to establish a framework. Focus groups commented on a prototype of an NTS assessment tool. Finally, we conducted a search of existing tools and literature. The final tool was developed based on the combined inputs. RESULTS: We created Norwegian medical students' non-technical skills (NorMS-NTS) assessment tool containing four main categories; together comprising 13 elements and a rating scale for the NTS of the person observed. CONCLUSIONS: The NorMS-NTS represents a purpose-made tool for assessing newly graduated physicians' NTS. It is similar to existing assessment tools but based on domain-specific user perspectives obtained through focus group interviews and feedback, integrated with results from a literature search, and with consideration of existing NTS tools.

Collecting evidence of validity for an assessment tool for Norwegian medical students' non-technical skills (NorMS-NTS): usability and reliability when used by novice raters.

BACKGROUND: The NorMS-NTS tool is an assessment tool for assessing Norwegian medical students' non-technical skills (NTS). The NorMS-NTS was designed to provide student feedback, training evaluations, and skill-level comparisons among students at different study sites. Rather than requiring extensive rater training, the tool should capably suit the needs of busy doctors as near-peer educators. The aim of this study was to examine the usability and preliminary assess validity of the NorMS-NTS tool when used by novice raters. METHODS: This study focused on the usability of the assessment tool and its internal structure. Three raters used the NorMS-NTS tool to individually rate the team leader, a medical student, in 20 video-recorded multi-professional simulation-based team trainings. Based on these ratings, we examined the tools' internal structure by calculating the intraclass correlation coefficient (ICC) (version 3.1) interrater reliability, internal consistency, and observability. After the rating process was completed, the raters answered a questionnaire about the tool's usability. RESULTS: The ICC agreement and the sum of the overall global scores for all raters were fair: ICC (3,1) = 0.53. The correlation coefficients for the pooled raters were in the range of 0.77-0.91. Cronbach's alpha for elements, categories and global score were mostly above 0.90. The observability was high (95%-100%). All the raters found the tool easy to use, none of the elements were redundant, and the written instructions were helpful. The raters also found the tool easier to use once they had acclimated to it. All the raters stated that they could use the tool for both training and teaching. CONCLUSIONS: The observed ICC agreement was 0.08 below the suggested ICC level for formative assessment (above 0.60). However, we know that the suggestion is based on the average ICC, which is always higher than a single-measure ICC. There are currently no suggested levels for single-measure ICC, but other validated NTS tools have single-measure ICC in the same range. We consider NorMS-NTS as a usable tool for formative assessment of Norwegian medical students' non-technical skills during multi-professional team training by raters who are new to the tool. It is necessary to further examine validity and the consequences of the tool to fully validate it for formative assessments.

Ethnicity, sex, and socioeconomic disparities in the treatment of traumatic rotator cuff injuries in Aotearoa/New Zealand.

HYPOTHESIS AND BACKGROUND: Traumatic rotator cuff injuries can be a leading cause of prolonged shoulder pain and disability and contribute to significant morbidity and health care costs. Previous studies have shown evidence of sociodemographic disparities with these injuries. The purpose of this nationwide study was to better understand these disparities based on ethnicity, sex, and socioeconomic status, in order to inform future health care strategies. METHODS: Accident Compensation Corporation (ACC) is a no-fault comprehensive compensation scheme encompassing all of Aotearoa/New Zealand (population in 2018, 4.7 million). Using the ACC database, traumatic rotator cuff injuries were identified between January 2010 and December 2018. Injuries were categorized by sex, ethnicity, age, and socioeconomic deprivation index of the claimant. RESULTS: During the 9-year study period, there were 351,554 claims accepted for traumatic rotator cuff injury, which totaled more than NZ$960 million. The greatest proportion of costs was spent on vocational support (49.8%), then surgery (26.3%), rehabilitation (13.1%), radiology (8.1%), general practitioner (1.6%), and "Other" (1.1%). Asian, Maori (indigenous New Zealanders), and Pacific peoples were under-represented in the age-standardized proportion of total claims and had lower rates of surgery than Europeans. Maori had higher proportion of costs spent on vocational support and lower proportions spent on radiology, rehabilitation, and surgery than Europeans. Males had higher number and costs of claims and were more likely to have surgery than females. There were considerably fewer claims from areas of high socioeconomic deprivation. DISCUSSION AND CONCLUSION: This large nationwide study demonstrates the important and growing economic burden of rotator cuff injuries. Indirect costs, such as vocational supports, are a major contributor to the cost, suggesting improving treatment and rehabilitation protocols would have the greatest economic impact. This study has also identified sociodemographic disparities that need to be addressed in order to achieve equity in health outcomes.

Crew Autonomy During Simulated Medical Event Management on Long Duration Space Exploration Missions.

OBJECTIVE: Our primary aim was to investigate crew performance during medical emergencies with and without ground-support from a flight surgeon located at mission control. BACKGROUND: There are gaps in knowledge regarding the potential for unanticipated in-flight medical events to affect crew health and capacity, and potentially compromise mission success. Additionally, ground support may be impaired or periodically absent during long duration missions. METHOD: We reviewed video recordings of 16 three-person flight crews each managing four unique medical events in a fully immersive spacecraft simulator. Crews were randomized to two conditions: with and without telemedical flight surgeon (FS) support. We assessed differences in technical performance, behavioral skills, and cognitive load between groups. RESULTS: Crews with FS support performed better clinically, were rated higher on technical skills, and completed more clinical tasks from the medical checklists than crews without FS support. Crews with FS support also had better behavioral/non-technical skills (information exchange) and reported significantly lower cognitive demand during the medical event scenarios on the NASA-TLX scale, particularly in mental demand and temporal demand. There was no significant difference between groups in time to treat or in objective measures of cognitive demand derived from heart rate variability and electroencephalography. CONCLUSION: Medical checklists are necessary but not sufficient to support high levels of autonomous crew performance in the absence of real-time flight surgeon support. APPLICATION: Potential applications of this research include developing ground-based and in-flight training countermeasures; informing policy regarding autonomous spaceflight, and design of autonomous clinical decision support systems.

A high-fat diet has negative effects on tendon resident cells in an in vivo rat model.

BACKGROUND: Tendinopathy is a major complication of diet-induced obesity. However, the effects of a high-fat diet (HFD) on tendon have not been well characterised. We aimed to determine: [1] the impact of a HFD on tendon properties and gene expression; and [2] whether dietary transition to a control diet (CD) could restore normal tendon health. METHODS: Sprague-Dawley rats were randomised into three groups from weaning and fed either a: CD, HFD or HFD for 12 weeks and then CD thereafter (HF-CD). Biomechanical, histological and structural evaluation of the Achilles tendon was performed at 17 and 27 weeks of age. Tail tenocytes were isolated with growth rate and collagen production determined. Tenocytes and activated THP-1 cells were exposed to conditioned media (CM) of visceral adipose tissue explants, and gene expression was analysed. RESULTS: There were no differences in the biomechanical, histological or structural tendon properties between groups. However, tenocyte growth and collagen production were increased in the HFD group at 27 weeks. There was lower SOX-9 expression in the HFD and HF-CD groups at 17 weeks and higher expression of collagen-Iα1 and matrix metalloproteinase-13 in the HFD group at 27 weeks. THP-1 cells exposed to adipose tissue CM from animals fed a HFD or HF-CD had lower expression of Il-10 and higher expression of Il-1ß. CONCLUSIONS: In this rodent model, a HFD negatively altered tendon cell characteristics. Dietary intervention restored some gene expression changes; however, adipose tissue secretions from the HF-CD group promoted an increased inflammatory state in macrophages. These changes may predispose tendon to injury and adverse events later in life.

Age-related differences in hamstring tendon used as autograft in reconstructive anterior cruciate ligament surgery.

PURPOSE: The hamstring tendon is the most commonly used autograft material in reconstructive surgeries of anterior cruciate ligament (ACL) tears. Younger patients have worse surgical outcomes, with a higher risk of re-rupture. We hypothesized that age-related changes in hamstring tendon properties affect the tendon's propensity to rupture when used as an autograft in ACL reconstructions. The purpose of this study was to compare hamstring tendon samples obtained from people aged 20 years or younger to samples obtained from older people. METHODS: Superfluous hamstring tendon material was collected from 13 young donors (aged 16-20 years) and 17 older donors undergoing ACL reconstructive surgery. Sections of the tendon samples were used for biomechanical testing, structural analysis of collagen fibrils by electron microscopy, and global analysis of gene expression by microarrays. RESULTS: We found that tendon samples from the older group had lower Young's modulus than the younger group (P = 0.015), whereas the stress to failure was similar in the two groups. We found no difference in the average diameter of collagen fibrils between the two groups. Microarray analysis identified 162 differentially expressed genes (fold change ≥ 1.5, P < 0.05), with overrepresentation of several biological processes, including regulation of adhesion, migration, inflammation, and differentiation (fold enrichment > 2.0, false discovery rate P < 0.05). CONCLUSION: The hamstring tendon from younger people has higher stiffness than tendon from older people, and the profile of gene expression in tendon varies with age. These differences may negatively affect the performance of the hamstring tendon in ACL reconstructions in younger people.

Modelling gluteus medius tendon degeneration and repair in a large animal model.

INTRODUCTION: Gluteus medius tendon tears often occur in the context of chronic tendinopathy and remain a difficult clinical problem. Surgical repair is challenging as it is often delayed and performed in degenerative tendons. No animal model currently exists to mimic the delayed repair of tendinopathic gluteus medius tears. The aims of this study were to develop a chronic model of gluteus medius tendinopathy and tear and then compare this model to an acute gluteus medius tear and repair. MATERIALS AND METHODS: Six gluteus medius muscles were dissected and examined in mature sheep to confirm anatomical similarity to the human counterpart. Ten separate adult sheep underwent tendon detachment, followed by relook and histological sampling at 6 and 16 weeks to assess the extent of tendon degeneration. Six adult sheep underwent tendon repair at 6 weeks and were later assessed for healing of the tendon and compared to a further four adult sheep who underwent an acute tendon detachment and repair procedure. RESULTS: The sheep gluteus medius muscle consisted of three compartments, the anterior, middle and posterior. All compartments inserted via the common tendon on the superolateral aspect of the greater trochanter. At both 6 and 16 weeks, there was significant tendinopathic changes on histology compared to controls as assessed by modified Movin's score (p = 0.018, p = 0.047) but no difference between the 6- and 16-week groups (p = 0.25). There were significant differences between delayed and acute repair in both histological appearance (p = 0.025) and biomechanical properties (p = 0.019), with acute repair superior in both. CONCLUSIONS: Tendon detachment for 6 weeks is sufficient to produce histological changes similar to chronic tendinopathy and repair of this degenerative tendon results in significantly poorer healing when compared to an acute repair model. Animal models for gluteus medius tears should use a delayed repair model to improve clinical validity.

A Novel In Vitro and In Silico System for Analyzing Complex Mechanobiological Behavior of Chondrocytes in Three-Dimensional Hydrogel Constructs.

Physiological loading is essential for the maintenance of articular cartilage through the regulation of tissue remodeling. To correctly understand the behavior of chondrocytes in their native environment, cell stimulating devices and bioreactors have been developed to examine the effect of mechanical stimuli on chondrocytes. This study describes the design and validation of a novel system for analyzing chondrocyte deformation patterns. This involves an in vitro mechanical device for a controlled application of multi-axial-loading regimes to chondrocyte-seeded agarose constructs and in silico models for analyzing chondrocyte deformation patterns. The computer-controlled device precisely applies compressive, tensile, and shear strains to hydrogel constructs using a customizable macro-based program. The synchronization of the displacements is shown to be accurate with a 1.2% error and is highly reproducible. The device design allows housing for up to eight novel designed free-swelling three-dimensional hydrogel constructs. Constructs include mesh ends and are optimized to withstand the application of up to 7% mechanical tensile and 15% shear strains. Constructs were characterized through mapping the strain within as mechanical load was applied and was validated using light microscopy methods, chondrocyte viability using live/dead imaging, and cell deformation strains. Images were then analyzed to determine the complex deformation strain patterns of chondrocytes under a range of dynamic mechanical stimulations. This is one of the first systems that have characterized construct strains to cellular strains. The features in this device make the system ideally suited for a systematic approach for the investigation of the response of chondrocytes to a complex physiologically relevant deformation profile.

Toxicity of tranexamic acid (TXA) to intra-articular tissue in orthopaedic surgery: a scoping review.

PURPOSE: Intra-articular administration of tranexamic acid (TXA) in orthopaedic arthroplasty and arthroscopic procedures has become increasingly common over the past decade. However, several recent reports have shown that TXA has the potential to be cytotoxic to cartilage, tendon and synovium. Our aim was to review the literature for evidence of toxic effects from TXA exposure to intra-articular tissue. METHODS: A scoping review methodology was used to search for studies assessing the toxic effects of TXA exposure to intra-articular tissues. MEDLINE, EMBASE, SCOPUS and The Cochrane Library were searched. Relevant information was extracted and synthesis of the retrieved data followed a basic content analytical approach. RESULTS: A total of 15 laboratory studies were retrieved. No clinical studies reporting a toxic effect of TXA on intra-articular tissue were identified in our search. Studies were analysed according to species of origin, tissue of origin and study setting (in vitro, ex vivo, or in vivo). There was increasing cytotoxicity to chondrocytes, tenocytes, synoviocytes and periosteum-derived cells with TXA concentrations beyond 20 mg/ml. Monolayer cell cultures appear more susceptible to TXA exposure, than three-dimensional and explant culture models. In vivo studies have not demonstrated a major toxic effect. CONCLUSIONS: Current evidence suggests a dose-dependent toxic effect on cartilage, tendon, and synovial tissue. Concentrations of 20 mg/ml or less are expected to be safe. There is a significant body of evidence to suggest the need for caution with intraarticular administration of TXA. There is a need for further human clinical trials in order to clarify the long-term safety of TXA topical application.

Medical Event Management for Future Deep Space Exploration Missions to Mars.

BACKGROUND: Long-duration exploration missions (LDEMs), such as voyages to Mars, will present unique medical challenges for astronaut crews, including communication delays and the inability to return to Earth early. Medical events threaten crewmember lives and increase the risk of mission failure. Managing a range of potential medical events will require excellent technical and nontechnical skills (NTSs). We sought to identify medical events with potential for rescue, range them according to the potential impact on crew health and mission success during LDEMs, and develop a list of NTSs to train for management of in-flight medical events. MATERIALS AND METHODS: Twenty-eight subject matter experts with specializations in surgery, medicine, trauma, spaceflight operations, NTS training, simulation, human factors, and organizational psychology completed online surveys followed by a 2-d in-person workshop. They identified and rated medical events for survivability, mission impact, and impact of crewmember NTSs on outcomes in space. RESULTS: Sudden cardiac arrest, smoke inhalation, toxic exposure, seizure, and penetrating eye injury emerged as events with the highest potential mission impact, greatest potential for survival, and that required excellent NTS for successful management. Key NTS identified to target in training included information exchange, supporting behavior, communication delivery, and team leadership/followership. CONCLUSIONS: With a planned Mars mission on the horizon, training countermeasures need to be developed in the next 3-5 y. These results may inform policy, selection, medical system design, and training scenarios for astronauts to manage in-flight medical events on LDEMs. Findings may extend to surgical and medical care in any rural and remote location.

The pathological features of hip abductor tendon tears - a cadaveric study.

BACKGROUND: The hip abductors are crucial in maintaining pelvic stability. Tears in these tendons are common and often debilitating. There is uncertainty regarding both the histological and macroscopic features of hip abductor tears. This study aims to clarify both the macroscopic and microscopic features of the tendon and enthesis in hip abductor tendon tears. METHODS: Thirty-six cadavers with an average age of 81 were dissected, and the hip abductor mechanisms removed en-bloc. The presence, location and size of the tears were recorded and analysed. The samples were processed into histological blocks and viewed using both transmitted and polarised light. Tendon histology was graded using the modified Movin's score in three sections (deep, middle and superficial layers) and the enthesis graded separately using 5-point criteria. Analysis of variance was used to confirm histological features associated with tears. RESULTS: Tears were found in 24 of 36 samples (67%). The most common finding was an isolated tear in the gluteus minimus (46%), followed by concurrent gluteus medius and gluteus minimus tears (33%). Histology revealed significantly more degeneration in both the tendon (p = 0.0005) and enthesis (p = 0.0011) when tears were present. Furthermore, these changes were concentrated in the deeper layers of the tendon (p = 0.0002) and enthesis (p = 0.003). CONCLUSION: This study demonstrated degeneration as the primary pathology underlying hip abductor tendon tears. Degenerative changes occur in both the tendon and enthesis, with the deeper layers predominantly affected. These findings are important for guiding surgical repair techniques and to aid the development of novel materials and biologics.

Diverticulosis and nine connective tissue disorders: epidemiological support for an association.

Purpose: An underlying connective tissue disorder (CTD) may predispose to formation of intestinal diverticula. We assess the association of diverticulosis with nine selected CTDs, to inform the pathophysiology of diverticula. Methods: A population-based period-prevalence study. Individuals (3.5 million New Zealand residents born 1901-1986) with a health system record 1999-2016 were grouped into those with a hospital diagnosis of diverticulosis or diverticulitis (ICD-10-AM K57), and those without. Also recorded were any hospital diagnoses of nine selected CTDs. The association of exposure to diverticulosis and each CTD was assessed using logistic regressions adjusted for age, gender, ethnicity and region. Results: In all, 85,958 (2.4%) people had a hospital diagnosis of diverticulosis. Hospitalisation with diverticulosis was highly significantly associated with rectal prolapse (adjusted odds ratio [OR] = 3.9), polycystic kidney disease (OR = 3.8), heritable syndromes (Marfan or Ehlers-Danlos) (OR = 2.4), female genital prolapse (OR = 2.3), non-aortic aneurysm (OR = 2.3), aortic aneurysm (OR = 2.2), inguinal hernia (OR = 1.9) and dislocations of shoulder and other joints (OR = 1.7), but not subarachnoid haemorrhage (OR = 1.0). Conclusion: People with diverticulosis are more likely to have colonic extracellular matrix (ECM)/connective tissue alterations in anatomical areas other than the bowel, suggesting linked ECM/connective tissue pathology. Although biases may exist, the results indicate large-scale integrated studies are needed to investigate underlying genetic pathophysiology of colonic diverticula, together with fundamental biological studies to investigate cellular phenotypes and ECM changes.

Overlay repair with a synthetic collagen scaffold improves the quality of healing in a rat rotator cuff repair model.

BACKGROUND: Augmenting repairs with extracellular matrix-based scaffolds is a common option for rotator cuff tears. In this study, a new collagen scaffold was assessed for its efficacy in augmenting rotator cuff repair. METHODS: The collagen scaffold was assessed in vitro for cytocompatibility and retention of tenocyte phenotype using alamarBlue assays, fluorescent imaging, and real-time polymerase chain reaction. Immunogenicity was assessed in vitro by the activation of human monocytes. In vivo, by use of a modified rat rotator cuff defect model, supraspinatus tendon repairs were carried out in 40 animals. Overlay augmentation with the collagen scaffold was compared with unaugmented repairs. At 6 and 12 weeks postoperatively, the repairs were tested biomechanically to evaluate repair strength, as well as histologically to assess quality of healing. RESULTS: The collagen scaffold supported human tendon-derived cell growth in vitro, with cells demonstrating proliferation and appearing morphologically tenocytic over the experimental period. No immunogenic responses were provoked compared with suture material control. In vivo, augmentation with the scaffold improved the histologic scores at 12 weeks (8.4 of 15 vs 6.4 of 15, P = .032). However, no significant difference was detected with mechanical testing. CONCLUSION: The new collagen scaffold was supportive of cell growth in vitro and generated a minimal acute inflammatory response. In vivo, we observed an improvement in the histologic appearance of the repair at 12 weeks. However, a meaningful increase in biomechanical strength was not achieved. Further modification and improvement of the scaffold are required prior to consideration for clinical use.

The Activity of Adiponectin in Bone.

The adipokine adiponectin affects multiple target tissues and plays important roles in glucose metabolism and whole-body energy homeostasis. Circulating adiponectin levels in obese people are lower than in non-obese, and increased serum adiponectin is associated with weight loss. Numerous clinical studies have established that fat mass is positively related to bone mass, a relationship that is maintained by communication between the two tissues through hormones and cytokines. Since adiponectin levels inversely correspond to fat mass, its bone effects and its potential contribution to the relationship between fat and bone have been investigated. In clinical observational studies, adiponectin was found to be negatively associated with bone mineral density, suggesting it might be a negative regulator of bone metabolism. In order to identify the mechanisms that underlie the activity of adiponectin in bone, a large number of laboratory studies in vitro and in animal models of mice over-expressing or deficient of adiponectin have been carried out. Results of these studies are not entirely congruent, partly due to variation among experimental systems and partly due to the complex nature of adiponectin signaling, which involves a combination of multiple direct and indirect mechanisms.

Synthesis and in vitro bone cell activity of analogues of the cyclohexapeptide dianthin G.

The cyclohexapeptide natural product dianthin G promotes osteoblast (bone-forming cell) proliferation in vitro at nanomolar concentrations, and is therefore considered a promising candidate for the treatment of osteoporosis. An N(α)-methyl amide bond scan of dianthin G was performed to probe the effect of modifying amide bonds on osteoblast proliferation. In addition, to provide greater structural diversity, a series of dicarba dianthin G analogues was synthesised using ring closing metathesis. Dianthin G and one novel dicarba analogue increased the number of human osteoblasts and importantly they did not increase osteoclast (bone-resorbing cell) differentiation in bone marrow cells.

Structure activity relationship study on the peptide hormone preptin, a novel bone-anabolic agent for the treatment of osteoporosis.

Preptin is a 34-residue pancreatic hormone shown to be anabolic to bone in vitro and in vivo. The bone activity of preptin resides within the (1-16) N-terminal fragment. Due to its peptidic nature, the truncated fragment of preptin is enzymatically unstable; however it provides an attractive framework for the creation of stable analogues using various peptidomimetic techniques. An alanine scan of preptin (1-16) was undertaken which showed that substitution of Ser at position 3 or Pro at position 14 did not inhibit the proliferative activity of preptin in primary rat osteoblasts (bone-forming cells). Importantly, Ser-3 to Ala substitution also showed a significant activity on osteoblast differentiation in vitro and increased the formation of mineralised bone matrix. Additional modifications with non-proteinogenic amino acids at position 3 improved the stability in liver microsomes, but diminished the osteoblast proliferative activity. In addition, to provide greater structural diversity, a series of macrocyclic preptin (1-16) analogues was synthesised using head-to-tail and head-to-side chain macrolactamisation as well as ring-closing metathesis. However, a detrimental effect on osteoblast activity was observed upon macrocyclisation.

Applying Physiologically Relevant Strains to Tenocytes in an In Vitro Cell Device Induces In Vivo Like Behaviors.

We have developed a novel cell stretching device (called Cell Gym) capable of applying physiologically relevant low magnitude strains to tenocytes on a collagen type I coated membrane. We validated our device thoroughly on two levels: (1) substrate strains, (2) cell level strains. Our cell level strain results showed that the applied stretches were transferred to cells accurately (∼90%). Our gene expression data showed that mechanically stimulated tenocytes (4%) expressed a lower level of COL I gene. COX2 gene was increased but did not reach statistical significance. Our device was then tested to see if it could reproduce results from an in vivo study that measured time-dependent changes in collagen synthesis. Our results showed that collagen synthesis peaked at 24 hrs after exercise and then decreased, which matched the results from the in vivo study. Our study demonstrated that it is important to incorporate physiologically relevant low strain magnitudes in in vitro cell mechanical studies and the need to validate the device thoroughly to operate the device at small strains. This device will be used in designing novel tendon tissue engineering scaffolds in the future.