A slow release formulation of insulin as a treatment for osteoarthritis

The Role of Exerkines in the Treatment of Knee Osteoarthritis: From Mechanisms to Exercise Strategies

With the increasing prevalence of knee osteoarthritis (KOA), the limitations of traditional treatments, such as their limited efficacy in halting disease progression and their potential side effects, are becoming more evident. This situation has prompted scientists to seek more effective strategies. In recent years, exercise therapy has gained prominence in KOA treatment due to its safety, efficacy, and cost-effectiveness, which are underpinned by the molecular actions of exerkines. Unlike conventional therapies, exerkines offer specific advantages by targeting inflammatory responses, enhancing chondrocyte proliferation, and slowing cartilage degradation at the molecular level. This review explores the potential mechanisms involved in and application prospects of exerkines in KOA treatment and provides a comprehensive analysis of their role. Studies show that appropriate exercise not only promotes overall health, but also positively impacts KOA by stimulating exerkine production. The effectiveness of exerkines, however, is influenced by exercise modality, intensity, and duration of exercise, making the development of personalized exercise plans crucial for KOA patients. Based on these insights, this paper proposes targeted exercise strategies designed to maximize exerkine benefits, aiming to provide novel perspectives for KOA prevention and treatment.

Genetic proxies for therapy of insulin drug targets and risk of osteoarthritis: a drug-target Mendelian randomization analysis

BACKGROUND

The potential effects of insulin therapy on osteoarthritis (OA) risk are poorly understood. This study aimed to explore the causal relationship between insulin therapy and OA.

METHODS

Mendelian randomization (MR) analysis was performed to examine the association between genetically proxied inhibition of insulin targets and the risk of overall, hip (HOA) and knee OA (KOA). We then performed univariable MR using summary statistics regarding insulin target genes derived from the DrugBank database. Data related to blood glucose reduction levels were used as a proxy for insulin levels. Two phenotypes, type 2 diabetes, and glycosylated hemoglobin levels, were selected as positive controls to confirm the direction and validity of the proxies. The OA datasets were derived from the UK Biobank cohort. Multivariable MR was adjusted for body mass index, sedentary behavior, cigarette smoking, frequency of alcohol intake, age, and genetic sex.

RESULTS

Genetically proxied insulin therapy was associated with an increased risk of overall OA [odds ratio (OR):1.2595; 95% confidence interval (CI):1.0810-1.4675] and HOA (OR:1.4218; 95%CI:1.1240-1.7985), which remained consistent across multiple MR methods. After adjusting for confounders, we found evidence supporting a significant causal link with a higher risk of overall OA and HOA. A further two-step MR analysis revealed no significant mediation effects from the six mediators in the associations.

CONCLUSION

There was a causal association between genetically proxied insulin therapy and a higher risk of OA, especially HOA.

Beyond mechanical loading: The metabolic contribution of obesity in osteoarthritis unveils novel therapeutic targets

Osteoarthritis (OA) is a prevalent progressive disease that frequently coexists with obesity. For several decades, OA was thought to be the result of ageing and mechanical stress on cartilage. Researchers' perspective has been greatly transformed when cumulative findings emphasized the role of adipose tissue in the diseases. Nowadays, the metabolic effect of obesity on cartilage tissue has become an integral part of obesity research; hoping to discover a disease-modifying drug for OA. Recently, several adipokines have been reported to be associated with OA. Particularly, metrnl (meteorin-like) and retinol-binding protein 4 (RBP4) have been recognized as emerging adipokines that can mediate OA pathogenesis. Accordingly, in this review, we will summarize the latest findings concerned with the metabolic contribution of obesity in OA pathogenesis, with particular emphasis on dyslipidemia, insulin resistance and adipokines. Additionally, we will discuss the most recent adipokines that have been reported to play a role in this context. Careful consideration of these molecular mechanisms interrelated with obesity and OA will undoubtedly unveil new avenues for OA treatment.

The association between diabetes mellitus and functionality in knee osteoarthritis: a cross-sectional study

Objective: The aim of this study was to determine the roles of diabetes mellitus (DM) on quality of life, function of knee, and muscle strength in patients with knee osteoarthritis (OA). Material and Method: This single-center, case-control study prospectively enrolled outpatients with knee OA visiting a physical therapy and rehabilitation clinic. The patients were grouped according to the presence of DM diagnosis. Demographic data, disease duration, and medical treatments of patients were recorded. Clinical parameters, radiographic grading (Kellgren-Lawrence grades), functional scales of the knee and quality of life were evaluated. Results: The study included 82 participants [age: 61.3±6.7 years; female: 76.8%]. The mean Western Ontario and McMaster Universities Osteoarthritis Index of OA patients with (n=37) and without DM (n=45) were 45.79±18.04 vs. 65.94±16.23, respectively (p=0.003). The Hb A1c levels showed a negative correlation with Knee Injury and Osteoarthritis Outcome Score components (pain, quality of life, sports, daily activities, symptom duration) (p

Role of nitric oxide in type 1 diabetes-induced osteoporosis

Type 1 diabetes (T1D)-induced osteoporosis is characterized by decreased bone mineral density, bone quality, rate of bone healing, bone formation, and increased bone resorption. Patients with T1D have a 2-7-fold higher risk of osteoporotic fracture. The mechanisms leading to increased risk of osteoporotic fracture in T1D include insulin deficiency, hyperglycemia, insulin resistance, lower insulin-like growth factor-1, hyperglycemia-induced oxidative stress, and inflammation. In addition, a higher probability of falling, kidney dysfunction, weakened vision, and neuropathy indirectly increase the risk of osteoporotic fracture in T1D patients. Decreased nitric oxide (NO) bioavailability contributes to the pathophysiology of T1D-induced osteoporotic fracture. This review discusses the role of NO in osteoblast-mediated bone formation and osteoclast-mediated bone resorption in T1D. In addition, the mechanisms involved in reduced NO bioavailability and activity in type 1 diabetic bones as well as NO-based therapy for T1D-induced osteoporosis are summarized. Available data indicates that lower NO bioavailability in diabetic bones is due to disruption of phosphatidylinositol 3‑kinase/protein kinase B/endothelial NO synthases and NO/cyclic guanosine monophosphate/protein kinase G signaling pathways. Thus, NO bioavailability may be boosted directly or indirectly by NO donors. As NO donors with NO-like effects in the bone, inorganic nitrate and nitrite can potentially be used as novel therapeutic agents for T1D-induced osteoporosis. Inorganic nitrites and nitrates can decrease the risk for osteoporotic fracture probably directly by decreasing osteoclast activity, decreasing fat accumulation in the marrow cavity, increasing osteoblast activity, and increasing bone perfusion or indirectly, by improving hyperglycemia, insulin resistance, and reducing body weight.

The Effect of Intraarticular Insulin on Chondral Defect Repair

OBJECTIVE

The aim of this study is to evaluate the effects of intraarticular insulin on the treatment of chondral defects.

DESIGN

Twenty-four mature New Zealand rabbits were randomly divided into 3 groups as control (Group 1), microfracture (Group 2), and microfracture and insulin (Group 3). Four-millimeter full-thickness cartilage defects were created to the weight-bearing surface on the medial femoral condyles of each rabbit. In the first group, any additional interventions were not performed. Microfracture was performed on defects in groups 2 and 3. Additionally, 10 IU of insulin glargine was administrated into the knee joints of the third group. Three months after surgery, the knee joints were harvested and cartilage quality was assessed according to Wakitani and ICRS (International Cartilage Repair Society) scores histopathologically. Insulin injections were performed into the knees of 2 additional rabbits without creating a cartilage defect to evaluate the potential adverse effects of insulin on healthy cartilage (Group 4).

RESULTS

The total ICRS and Wakitani scores of the insulin group were found to be significantly lower than the microfracture group but similar to the control group. No negative effects of insulin on healthy cartilage were detected. Intraarticular insulin after surgery has led to a statistically significant decrease in systemic blood sugar levels whereas the decrease observed after administration to intact tissues was not statistically significant.

CONCLUSIONS

Insulin had a negative influence on the quality of cartilage regeneration and had no effect on healthy cartilage. Intraarticular insulin administration does not cause significant systemic effects in intact tissue.

Insulin Exacerbates Inflammation in Fibroblast-Like Synoviocytes

Osteoarthritis (OA) is considered the most frequent degenerative disease and is characterized by cartilage degradation and synovial inflammation. Fibroblast-like synoviocytes (FLSs) are vital to synovial inflammation in OA. Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and hyperinsulinemia (HINS) and has been demonstrated to be an independent risk factor for OA. Autophagy is involved in the processes of various inflammatory diseases, and autophagy inhibition can stimulate OA development. Thus, we aimed to investigate the role of insulin in the inflammatory phenotype and autophagy of FLSs in OA. The data showed that cell viability and proinflammatory cytokine production in FLSs were both increased after insulin stimulation. We also found that high insulin could promote macrophage infiltration and chemokine production but inhibited autophagy in FLSs. To further explore the potential mechanisms, the effects of insulin on PI3K/Akt/mTOR and NF-ĸB signaling activation were evaluated. The results indicated that insulin activated PI3K/Akt/mTOR/NF-ĸB signaling, and the above-mentioned inflammatory responses, including autophagy inhibition, were notably attenuated by specific signaling inhibitors in the presence of high insulin. Moreover, the data showed that a positive feedback loop existed between proinflammatory cytokines (e.g., IL-1β, IL-6, and TNF-α) and PI3K/mTOR/Akt/NF-ĸB signaling in FLSs, and insulin enhanced this feedback loop to accelerate OA progression. Our study suggests that insulin may be a novel therapeutic strategy for OA prevention and treatment in the future.

Effects of nutrition and hormones on functional appliance treatment outcome in patients with skeletal Class II malocclusion

BACKGROUND

Functional appliances has been used for treatment of skeletal Class II malocclusion for a long time; however, the real skeletal effects, mandibular growth particularly, remain insufficient. Several auxiliary approaches have been attempted with the hope of enhancing treatment effects. In this review, we summarize and discuss the use of additional nutrition and hormones to assist the functional appliance treatment on patients with skeletal Class II malocclusion.

METHODS

Relevant articles were identified by electronic research in MEDLINE Ovid using keywords such as "nutrition," "hormone," "functional appliance," "orthodontics," "maxillofacial development," and "maxillofacial abnormalities." References of related articles were assessed for relevant studies to identify additional published references.

RESULTS

The literature search yielded 239 studies. According to the current literature, use of additional nutrition and hormones, including growth hormones, sex hormones, insulin, and insulin-like growth factor I, seem to improve the effects of functional appliance treatment on patients with skeletal Class II malocclusion.

CONCLUSIONS

The current evidence indicates that additional nutrition or hormones might improve the treatment effects on mandibular hypoplasia compared with the functional appliance alone, which is a promising approach and calls for further studies.

[there any association of metabolic disturbances with joint destruction and pain?]

Osteoarthritis and type 2 diabetes mellitus represent two the most common chronic diseases. They possess many shared epidemiologic traits, have common risk factors, and embody heterogeneous multifactorial pathologies, which develop due to interaction of genetic an environmental factors. In addition, these diseases are often occurring in the same patient. In spite of the differences in clinical manifestation both diseases have similar disturbances of cellular metabolism, primarily associated with ATP production and utilization. The review discusses molecular mechanisms determining pathophysiological processes associated with glucose and lipid metabolism as well as the means aiming to alleviate the disturbances of energy metabolism as a new a therapeutic approach.

Biomaterial-engineered intra-articular drug delivery systems for osteoarthritis therapy

Osteoarthritis (OA) is a progressive and degenerative disease, which is no longer confined to the elderly. So far, current treatments are limited to symptom relief, and no valid OA disease-modifying drugs are available. Additionally, OA relative joint is challenging for drug delivery, since the drugs experience rapid clearance in joint, showing a poor bioavailability. Existing therapeutic drugs, like non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids, are not conducive for long-term use due to adverse effects. Though supplementations, including chondroitin sulfate and glucosamine, have shown beneficial effects on joint tissues in OA, their therapeutic use is still debatable. New emerging agents, like Kartogenin (KGN) and Interleukin-1 receptor antagonist (IL-1 ra), without a proper formulation, still will not work. Therefore, it is urgent to establish a suitable and efficient drug delivery system for OA therapy. In this review, we pay attention to various types of drug delivery systems and potential therapeutic drugs that may escalate OA treatments.

Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils

A synthetic derivative, GnRH [6-D-Phe], stable against enzymatic degradation, self-assembles and forms nanostructures and fibrils upon a pH shift in the presence of different concentrations of Zn²⁺in vitro. Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR–FTIR) revealed the existence of higher order assembly of Zn²⁺: GnRH [6-D-Phe]. Nuclear Magnetic Resonance spectroscopy (NMR) indicated a weak interaction between Zn²⁺ and GnRH [6-D-Phe]. Atomic Force Microscopy (AFM) showed the existence of GnRH [6-D-Phe] oligomers and fibrils. Molecular Dynamic (MD) simulation of the 10:1 Zn²⁺: GnRH [6-D-Phe] explored the interaction and dimerization processes. In contrast to already existing short peptide fibrils, GnRH [6-D-Phe] nanostructures and fibrils form in a Tris-buffered pH environment in a controlled manner through a temperature reduction and a pH shift. The lyophilized Zn²⁺: GnRH [6-D-Phe] assembly was tested as a platform for the sustained delivery of GnRH [6-D-Phe] and incorporated into two different oil vehicle matrices. The in vitro release was slow and continuous over 14 days and not influenced by the oil matrix.

Effects of medication-treated diabetes on incidence and progression of knee osteoarthritis: a longitudinal analysis of the Osteoarthritis Initiative data

Diabetes has been proposed as a factor involved in the pathogenesis of osteoarthritis (OA). Currently, there is a lack of research evaluating the prospective impact of diabetes on OA structural outcomes. In this study, we assessed the effects of medication-treated diabetes on incidence and progression of knee OA. We analysed longitudinal data from the multi-center, longitudinal, prospective observational Osteoarthritis Initiative (OAI) study. The main outcomes were radiographic OA incidence (development of Kellgren-Lawrence grade 2 with joint space narrowing, JSN) and progression (increase in semiquantitative JSN or a new knee replacement). For the study of incidence, we selected participants with KL <2 or /KL = 2 without JSN at baseline (incidence sample). To evaluate progression, we selected participants with baseline JSN <3 (progression sample). We used generalized estimating equations (GEE) logistic regression with adjustment for potential confounders to evaluate the effects of medication-treated diabetes on knee OA incidence and progression. We studied 3725 knees (3498 non-diabetic and 228 diabetic) in the incidence sample and 3594 knees (3335 non-diabetic and 259 diabetic) in the progression sample. Medication-treated diabetes did not have an effect on knee OA incidence (odds ratio, OR 0.53, 95% confidence interval, CI 0.23-1.5). There was an independent association between medication-treated diabetes and reduced progression of knee OA [OR 0.66, 95% CI (0.44-0.98)]. Medication-treated diabetes has no effect on knee OA incidence but reduces knee OA progression. The role of diabetes and anti-diabetic drugs in knee OA progression needs further exploration.

Insulin and vanadium protect against osteoarthritis development secondary to diabetes mellitus in rats

OBJECTIVE

Diabetic complications such as cardiovascular disease and osteoarthritis (OA) are among the common public health problems. The effect of insulin on OA secondary to diabetes has not been investigated before in animal models. Therefore, we sought to determine whether insulin and the insulin-mimicking agent, vanadium can protect from developing OA in diabetic rats.

METHODS

Type 1 diabetes mellitus (T1DM) was induced in Sprague-Dawley rats and treated with insulin and/or vanadium. Tissues harvested from the articular cartilage of the knee joint were examined by scanning electron microscopy, and blood samples were assayed for oxidative stress and inflammatory biomarkers.

RESULTS

Eight weeks following the induction of diabetes, a profound damage to the knee joint compared to the control non-diabetic group was observed. Treatment of diabetic rats with insulin and/or vanadium differentially protected from diabetes-induced cartilage damage and deteriorated fibrils of collagen fibers. The relative biological potencies were insulin + vanadium >> insulin > vanadium. Furthermore, there was about 2- to 5-fold increase in TNF-α (from 31.02 ± 1.92 to 60.5 ± 1.18 pg/ml, p < 0.0001) and IL-6 (from 64.67 ± 8.16 to 338.0 ± 38.9 pg/ml, p < 0.0001) cytokines and free radicals measured as TBARS (from 3.21 ± 0.37 to 11.48 ± 1.5 µM, p < 0.0001) in the diabetic group, which was significantly reduced with insulin and or vanadium. Meanwhile, SOD decreased (from 17.79 ± 8.9 to 8.250.29, p < 0.0001) and was increased with insulin and vanadium. The relative potencies of the treating agents on inflammatory and oxidative stress biomarkers were insulin + vanadium >> insulin > vanadium.

CONCLUSION

The present study demonstrates that co-administration of insulin and vanadium to T1DM rats protect against diabetes-induced OA possibly by lowering biomarkers of inflammation and oxidative stress.

Insulin decreases autophagy and leads to cartilage degradation

OBJECTIVE

Autophagy, a key homeostasis mechanism, is defective in Osteoarthritis (OA) and Type 2 Diabetes (T2D). T2D has been proposed as a risk factor for OA. We hypothesized that diabetes impairs articular cartilage integrity by decreasing autophagy. Our objective was to investigate the effects of high glucose and insulin, characteristics of T2D, on cartilage homeostasis.

METHODS

Immortalized human chondrocytes (TC28a2) and primary human chondrocytes (HC) were cultured in 25 mM or 0 mM glucose and treated with insulin (10, 100, 500 nM) for 2, 6 or 24 h. Activity of LC3-II, Akt and rpS6 was evaluated by Western blotting (WB). Human cartilage explants were cultivated with 25 mM glucose and insulin (100,1000 nM) for 24 h to evaluate histopathology. MMP-13 and IL-1β expression was determined by immunohistochemistry and WB. Effects of Rapamycin (10 μM) were analyzed by WB. LC3 and rpS6 expression was determined by WB in chondrocytes from Healthy, Non Diabetic-OA and Diabetic-OA patients.

RESULTS

Insulin downregulates autophagy by reducing LC3 II expression and increasing Akt and rpS6 phosphorylation. Loss of proteoglycans and increased MMP-13 and IL-1β expression was observed after insulin treatment. Autophagy activation by rapamycin reversed insulin effects. Importantly, chondrocytes from diabetic-OA patients showed decreased LC3 and increased p-rpS6 expression compared to Healthy and Non-Diabetic OA patients.

CONCLUSIONS

These results suggest that decreased autophagy might be a mechanism by which diabetes influences cartilage degradation. Pharmacological activation of autophagy may be an effective therapeutic approach to prevent T2D-induced cartilage damage.

Knee Osteoarthritis in Type 2 Diabetes Mellitus: Does Insulin Therapy Retard Osteophyte Formation?

OBJECTIVE

The aim of this study was to investigate whether or not radiographic changes observed in knee osteoarthritis (OA) in type 2 diabetes mellitus (T2DM) patients on insulin therapy differed from those not on insulin.

MATERIAL AND METHODS

A cross-sectional study was performed in 311 subjects: 211 T2DM patients and 100 without diabetes (controls) in Mubarak Hospital, Kuwait. Patients were categorized into 3 groups: T2DM patients not on insulin (G1, n = 99), T2DM patients on insulin (G2, n = 112) and a nondiabetic control group (G3, n = 100). Plain X-ray of both knees was used to assess the changes of knee OA and graded using the Kellegren-Lawrence scale (0-4) and the Osteoarthritis Research Society International Atlas grading scale (0-3). A total of 622 knee X-rays were evaluated. SPSS version 21.0 was used for data analysis.

RESULTS

A highly significant association (p < 0.0001) was observed for joint space narrowing (JSN) as well as for osteophyte formation between the three groups. Comparing G2 and G3, a highly significant association (p < 0.0001) was retained for JSN [201 (89.7%) vs. 199 (99.5%)] and for osteophyte formation [26 (11.7%) vs. 72 (36.0%)]. Comparing G1 and G2, significantly less osteophyte formation was noted in G2 patients compared to G1 patients [26 (11.7%) vs. 39 (19.7%), p = 0.02]. Multivariate logistic regression analysis showed that the G2 group had less chance of osteophyte formation than either the G1 group or G3 control group (OR = 0.294, p = 0.008 and OR = 0.098, p < 0.001, respectively).

CONCLUSION

Our findings show that T2DM patients with OA knees on insulin therapy have less radiographic osteophytes compared to T2DM patients not on insulin.

Expression of matrix metalloproteinases-8 and -9 and their tissue inhibitor in the condyles of diabetic rats with mandibular advancement

The present study aimed to evaluate the effects of type 1 diabetes mellitus on the condylar response during treatment with a functional appliance. Sprague-Dawley rats were divided into 3 groups, normal (NG), diabetes (DG) and diabetes with insulin-treatment (TG). Bite-jumping appliances were fitted to the rats in the experimental groups. At 7, 14, 21 and 28 days following fitting, animals were sacrificed and condyles were excised and processed using routine histological techniques. The expression of matrix metalloproteinase (MMP)-8, MMP-9 and tissue inhibitor of metalloproteinase-1 (TIMP-1) was detected using immunohistochemical analysis. Mandibular advancement increased the expression levels of MMP-8 (peaked on day 28), MMP-9 (peaked on day 21), TIMP-1 (peaked on days 21 and 28) and the ratio of MMP-8 to TIMP-1 and MMP-9 to TIMP-1. In the DG, diabetes decreased the expression levels of MMP-8 and MMP-9 induced by mandibular advancement and increased the expression levels of TIMP-1 compared with that of the NG. The ratio of MMP-8 to TIMP-1 and MMP-9 to TIMP-1 also showed a significant decrease in the DG compared with that of the NG. A recovery of these parameters was observed in the TG. Diabetes significantly altered the condylar response, which was triggered by mandibular advancement, and weakened subsequent bone deposition. The results from the TG were not significantly different from that of the NG.

Drug delivery systems for intra-articular treatment of osteoarthritis

INTRODUCTION

Intra-articular (IA) drug delivery is very useful in the treatment of osteoarthritis (OA), the most common chronic joint affliction. However, the therapeutic effect of IA administration depends mostly on the efficacy of drug delivery.

AREAS COVERED

The present article reviews the current status of IA therapy for OA treatment as well as its rationale. Outlines of drug delivery parameters such as release profile, retention time, distribution, size and transport that influence the drug's biological performance in the joints are summarized. New delivery systems, currently under investigation, including liposome, nanoparticle, microparticle and hydrogel formulations are introduced. Functionalized drug delivery systems by targeting and thermoresponsiveness that are being investigated for OA treatment via IA therapy are also addressed.

EXPERT OPINION

Several delivery systems, including liposome, microparticles, nanoparticles and hydrogels, have been investigated for the sustained drug delivery to the joints. These can be advanced by the use of functionalized drug delivery systems that can lead targeting to specific regions and thermoresponsiveness for prolonged drug release in the joints. Further advances will bring forth new biocompatible and biodegradable materials as a drug carrier or new combination regimens. Future innovations in this field should be directed toward the development of adapted delivery systems that can induce tissue regeneration in OA patients.

Association of hand or knee osteoarthritis with diabetes mellitus in a population of Hispanics from Puerto Rico

BACKGROUND

Although a higher prevalence of osteoarthritis (OA) has been reported among diabetes mellitus (DM) patients, inconsistencies and limitations of observational studies have precluded a conclusive association.

OBJECTIVE

The objective of this study was to evaluate the association of hand or knee OA with DM in a population of Hispanics from Puerto Rico.

METHODS

A cross-sectional study was performed in 202 subjects (100 adult DM patients as per the National Diabetes Data Group Classification and 102 nondiabetic subjects). Osteoarthritis of hand and knee was ascertained using the American College of Rheumatology classification criteria. Sociodemographic characteristics, health-related behaviors, comorbidities, pharmacotherapy, and DM clinical manifestations were determined. Multivariable logistic regression was used to evaluate the association of DM with hand or knee OA and to evaluate factors associated with hand or knee OA among DM patients.

RESULTS

The mean (SD) age for DM patients was 51.6 (13.1) years; 64.0% were females. The mean (SD) DM duration was 11.0 (10.4) years. The prevalence of OA in patients with DM and nondiabetic subjects was 49.0% and 26.5%, respectively (P < 0.01). In the multivariable analysis, patients with DM had 2.18 the odds of having OA when compared with nondiabetic subjects (95% confidence interval [CI], 1.12-4.24). In a subanalysis among DM patients, female patients were more likely to have hand or knee OA (odds ratio [95% CI], 5.06 [1.66-15.66]), whereas patients who did not use insulin alone for DM therapy were more likely to have OA (odds ratio [95% CI], 4.44 [1.22-16.12]).

CONCLUSIONS

In this population of Hispanics from Puerto Rico, DM patients were more likely to have OA of hands or knees than were nondiabetic subjects. This association was retained in multivariable models accounting for established risk factors for OA. Among DM patients, females were at greater risk for OA, whereas the use of insulin was negatively associated.

Modeling the Insulin-Like Growth Factor System in Articular Cartilage

IGF signaling is involved in cell proliferation, differentiation and apoptosis in a wide range of tissues, both normal and diseased, and so IGF-IR has been the focus of intense interest as a promising drug target. In this computational study on cartilage, we focus on two questions: (i) what are the key factors influencing IGF-IR complex formation, and (ii) how might cells regulate IGF-IR complex formation? We develop a reaction-diffusion computational model of the IGF system involving twenty three parameters. A series of parametric and sensitivity studies are used to identify the key factors influencing IGF signaling. From the model we predict the free IGF and IGF-IR complex concentrations throughout the tissue. We estimate the degradation half-lives of free IGF-I and IGFBPs in normal cartilage to be 20 and 100 mins respectively, and conclude that regulation of the IGF half-life, either directly or indirectly via extracellular matrix IGF-BP protease concentrations, are two critical factors governing the IGF-IR complex formation in the cartilage. Further we find that cellular regulation of IGF-II production, the IGF-IIR concentration and its clearance rate, all significantly influence IGF signaling. It is likely that negative feedback processes via regulation of these factors tune IGF signaling within a tissue, which may help explain the recent failures of single target drug therapies aimed at modifying IGF signaling.

Expression and function of the insulin receptor in normal and osteoarthritic human chondrocytes: modulation of anabolic gene expression, glucose transport and GLUT-1 content by insulin

OBJECTIVE

Chondrocytes respond to insulin, but the presence and role of the specific high affinity insulin receptor (InsR) has never been demonstrated. This study determined whether human chondrocytes express the InsR and compared its abundance and function in normal and osteoarthritis (OA) human chondrocytes.

DESIGN

Cartilage sections were immunostained for detection of the InsR. Non-proliferating chondrocyte cultures from normal and OA human cartilage were treated with 1nM or 10nM insulin for various periods. InsR, insulin-like growth factor receptor (IGFR), aggrecan and collagen II mRNA levels were assessed by real time RT-PCR. InsR, glucose transporter (GLUT)-1, phospho-InsRbeta and phospho-Akt were evaluated by western blot and immunofluorescence. Glucose transport was measured as the uptake of [3H]-2-Deoxy-d-Glucose (2-DG).

RESULTS

Chondrocytes staining positively for the InsR were scattered throughout the articular cartilage. The mRNA and protein levels of the InsR in OA chondrocytes were approximately 33% and 45%, respectively, of those found in normal chondrocytes. Insulin induced the phosphorylation of the InsRbeta subunit. Akt phosphorylation and 2-DG uptake increased more intensely in normal than OA chondrocytes. Collagen II mRNA expression increased similarly in normal and OA chondrocytes while aggrecan expression remained unchanged. The Phosphoinositol-3 Kinase (PI3K)/Akt pathway was required for both basal and insulin-induced collagen II expression.

CONCLUSIONS

Human chondrocytes express functional InsR that respond to physiologic insulin concentrations. The InsR seems to be more abundant in normal than in OA chondrocytes, but these still respond to physiologic insulin concentrations, although some responses are impaired while others appear fully activated. Understanding the mechanisms that regulate the expression and function of the InsR in normal and OA chondrocytes can disclose new targets for the development of innovative therapies for OA.

Biodegradable insulin-loaded PLGA microspheres fabricated by three different emulsification techniques: investigation for cartilage tissue engineering

Growth, differentiation and migration factors facilitate the engineering of tissues but need to be administered with defined gradients over a prolonged period of time. In this study insulin as a growth factor for cartilage tissue engineering and a biodegradable PLGA delivery device were used. The aim was to investigate comparatively three different microencapsulation techniques, solid-in-oil-in-water (s/o/w), water-in-oil-in-water (w/o/w) and oil-in-oil-in-water (o/o/w), for the fabrication of insulin-loaded PLGA microspheres with regard to protein loading efficiency, release and degradation kinetics, biological activity of the released protein and phagocytosis of the microspheres. Insulin-loaded PLGA microspheres prepared by all three emulsification techniques had smooth and spherical surfaces with a negative zeta potential. The preparation technique did not affect particle degradation nor induce phagocytosis by human leukocytes. The delivery of structurally intact and biologically active insulin from the microspheres was shown using circular dichroism spectroscopy and a MCF7 cell-based proliferation assay. However, the insulin loading efficiency (w/o/w about 80%, s/o/w 60%, and o/o/w 25%) and the insulin release kinetics were influenced by the microencapsulation technique. The results demonstrate that the w/o/w microspheres are most appropriate, providing a high encapsulation efficiency and low initial burst release, and thus these were finally used for cartilage tissue engineering. Insulin released from w/o/w PLGA microspheres stimulated the formation of cartilage considerably in chondrocyte high density pellet cultures, as determined by increased secretion of proteoglycans and collagen type II. Our results should encourage further studies applying protein-loaded PLGA microspheres in combination with cell transplants or cell-free in situ tissue engineering implants to regenerate cartilage.

Osteoporosis in diabetes mellitus: Possible cellular and molecular mechanisms

Osteoporosis, a global age-related health problem in both male and female elderly, insidiously deteriorates the microstructure of bone, particularly at trabecular sites, such as vertebrae, ribs and hips, culminating in fragility fractures, pain and disability. Although osteoporosis is normally associated with senescence and estrogen deficiency, diabetes mellitus (DM), especially type 1 DM, also contributes to and/or aggravates bone loss in osteoporotic patients. This topic highlight article focuses on DM-induced osteoporosis and DM/osteoporosis comorbidity, covering alterations in bone metabolism as well as factors regulating bone growth under diabetic conditions including, insulin, insulin-like growth factor-1 and angiogenesis. Cellular and molecular mechanisms of DM-related bone loss are also discussed. This information provides a foundation for the better understanding of diabetic complications and for development of early screening and prevention of osteoporosis in diabetic patients.

Intra-articular depot formulation principles: role in the management of postoperative pain and arthritic disorders

The joint cavity constitutes a discrete anatomical compartment that allows for local drug action after intra-articular injection. Drug delivery systems providing local prolonged drug action are warranted in the management of postoperative pain and not least arthritic disorders such as osteoarthritis. The present review surveys various themes related to the accomplishment of the correct timing of the events leading to optimal drug action in the joint space over a desired time period. This includes a brief account on (patho)physiological conditions and novel potential drug targets (and their location within the synovial space). Particular emphasis is paid to (i) the potential feasibility of various depot formulation principles for the intra-articular route of administration including their manufacture, drug release characteristics and in vivo fate, and (ii) how release, mass transfer and equilibrium processes may affect the intra-articular residence time and concentration of the active species at the ultimate receptor site.

Arthroscopic debridement of the osteoarthritic knee combined with hyaluronic acid (Orthovisc) treatment: a case series and review of the literature

Objective

An evaluation of safety and efficacy of high molecular weight hyaluronan (HA) delivered at the time of arthroscopic debridement of the osteoarthritic knee.

Methods

Thirty consecutive patients who met inclusion and exclusion criteria underwent arthroscopic debridement by a single surgeon and concomitant delivery of 6 ml/90 mg HA (Orthovisc^®). These patients were evaluated preoperatively, at 6 weeks, 3 and 6 months post-operatively. Evaluations consisted of WOMAC pain score, SF-36 Physical Component Summary (PCS) score and complications.

Results

No complications occurred during this study. Pre-op average WOMAC pain score was 6.8 +/- 3.5 (n = 30) with a reduction to 3.4 +/- 3.1 at 6 weeks (n = 27). Final average WOMAC pain score improved to 3.2 +/- 3.8 at six months (n = 23). No patients had deterioration of the WOMAC pain score. Mean pre-operative SF-36 PCS score was 39.0 +/- 10.4 with SF-36 PCS score of the bottom 25th percentile at 29.9 (n = 30). Post procedure and HA delivery, mean PCS score at 6 weeks improved to 43.7 +/- 8.0 with the bottom 25th percentile at 37.5 (n = 27). At 6 months, mean PCS score was 48.0 +/- 9.8 with the bottom 25th percentile improved to 45.8 (n = 23).

Conclusion

The results show that concomitant delivery of high molecular weight hyaluronan (Orthovisc^® – 6 ml/90 mg) is safe when given at the time of arthroscopic debridement of the osteoarthritic knee. By delivering HA (Orthovisc^®) at the time of the arthroscopic debridement, there may be a decreased risk of joint infection and/or injection site pain. Furthermore, the combination of both procedures show efficacy in reducing WOMAC pain scores and improving SF-36 PCS scores over a six month period.

Emulsion-based synthesis of PLGA-microspheres for the in vitro expansion of porcine chondrocytes

The in vitro cell expansion of autologous chondrocytes is of high interest in regenerative medicine since these cells can be used to treat joint cartilage defects. In order to preserve chondrocyte phenotype, while optimizing adhesion on microspheres, several processing parameters for the microsphere synthesis were varied. In this study three different polylactide-co-glycolides were used with differing lactide-glycolide ratios (85:15 and 50:50) and differing inherent viscosities. An emulsion route was established, where the polymer was dissolved in chloroform and then injected into a stirred polyvinyl alcohol-water solution at different polymer concentrations and different stirring velocities to produce microspheres with varying diameters. The sphere size distribution and morphology was analyzed using image processing software on SEM pictures. Based on previous experiments with commercial microspheres, three optimum samples were selected for further investigations. The degradation of the microspheres was determined in a long-term experiment in culture medium for 3 months. Adherent cells were characterized after 3 and 5 days by FDA+EB vital staining and in SEM.

Notochord cells regulate intervertebral disc chondrocyte proteoglycan production and cell proliferation

STUDY DESIGN

Non-chondrodystrophic dog notochord cell conditioned medium was used to evaluate chondrocyte proteoglycan production and cell proliferation.

OBJECTIVES

To evaluate the responsiveness of bovine disc-derived chondrocytes to notochord-cell conditioned medium with respect to proteoglycan and cell proliferation. In addition, to examine phenotypic changes of notochord cells cultured in monolayered as compared to 3-dimensional culture.

SUMMARY OF BACKGROUND DATA

Non-chondrodystrophic dogs maintain their intervertebral disc notochord cells into adulthood and are protected from having degenerative disc disease develop. The chondrodystrophic breeds such as beagles do not preserve these cells and have disc disease develop much earlier in life. The role of the notochord cell within the disc nucleus is poorly understood.

METHODS

Canine notochord cells were cultured within alginate beads in serum-deficient conditions using Dulbecco modified Eagle medium to produce notochord cell conditioned medium (NCCM). NCCM was used to stimulate bovine disc chondrocytes from which we evaluated proteoglycan production and cell proliferation as compared to chondrocytes grown in DMEM alone. In addition, parallel cultures of notochord cells were seeded within alginate beads as well as in monolayer and cultured in order to examine for differences in phenotype between the 2 culture conditions.

RESULTS

The morphologic aspects of the intervertebral disc between the species differed markedly. A dose- dependent relationship was seen between proteoglycan production and NCCM concentration across various concentrations of NCCM in repeated experiments. Although there was a 4-fold increase in cell proliferation under all NCCM concentrations, this increase in cell proliferation was not dose dependent in the concentrations tested. Unlike chondrocytes, notochord cells do not adhere to tissue culture plate (monolayer) until at least day 4-6, do not markedly alter their phenotype, and rapidly assume masses of cells while floating within tissue culture medium.

CONCLUSIONS

The biology of the disc-derived chondrocyte is profoundly affected by NCCM in that various concentrations of NCCM activate proteoglycan production in a dose-dependent fashion. However, in the doses tested in our study, cell proliferation was increased but in a nondose-dependent fashion. Notochord cells retain their phenotype even in monolayer and through the development of floating intimately associated masses of cells suggest the development and maintenance of cell-cell interaction. These masses of cells are retained even after 6 days in culture when they do attach to the tissue plate surface. The persistence of notochord cells in non-chondrodystrophic dog species suggests that these in vitro studies may mirror the milieu of the disc in vivo, in which the notochord cell may play a key role in disc homeostasis.

Lipidic implants for controlled release of bioactive insulin: effects on cartilage engineered in vitro

Controlled release systems for growth factors and morphogens are potentially powerful tools for the engineering or the treatment of living tissues. However, due to possible instabilities of the protein during manufacture, storage, and release, in the development of new release systems it is paramount to investigate into the maintenance of bioactivity of the protein. Within this study, recently developed protein releasing lipid matrix cylinders of 2 mm diameter and 2 mm height made from glycerol tripalmitate were manufactured in a compression process without further additives. Insulin in different concentrations (0.2%, 1%, and 2%) served as model protein. The bioactivity of the protein released from the matrices was investigated in a long-term cartilage engineering culture for up to four weeks; additionally, the release profiles were determined using ELISA. Insulin released from the matrices increased the wet weights of the cartilaginous cell-polymer constructs (up to 3.2-fold), the amount of GAG and collagen in the constructs (up to 2.4-fold and 3.2-fold, respectively) and the GAG and collagen content per cell (1.8-fold and 2.5-fold, respectively), compared to the control. The dose-dependent effects on tissue development correlated well with release profiles from the matrices with different insulin loading. In conclusion, the lipid matrices, preserving the bioactivity of incorporated and released protein, are suggested as a suitable carrier system for use in tissue engineering or for the localized treatment of tissues with highly potent protein drugs such as used in the therapy of brain cancer or neurodegenerative CNS diseases.

Development of a biologic prosthetic composite for cartilage repair

At present there is no satisfactory treatment for deep osteochondral defects. Here we report the development of a biologic prosthetic composite containing periosteum from 2-month-old rabbits and a porous tantalum scaffold. When cultured under chondrogenic conditions, the composites form a robust hyaline-like cartilage outgrowth that is attached to the porous scaffold by fibrous tissue ingrowth. The mechanical properties of these composites are similar to those of normal osteochondral plugs after only 6 weeks in culture. Thus, porous tantalum scaffolds are compatible with the chondrogenic capacity of periosteum. We hypothesize that these periosteum-porous tantalum composites will be useful for the repair of major osteochondral defects. However, in vivo experiments using biological resurfacing of large osteochondral defects with a porous tantalum scaffold and autologous periosteal graft in animal models are necessary to further explore this possibility. The implications of a successful method for cartilage regeneration would be great in terms of the number of patients affected and the quality of life for each of those patients.

Microarrays of small molecules embedded in biodegradable polymers for use in mammalian cell-based screens

We developed a microarray-based system for screening small molecules in mammalian cells. This system is compatible with image-based screens and requires fewer than 100 cells per compound. Each compound is impregnated in a 200-microm-diameter disc composed of biodegradable poly-(D),(L)-lactide/glycolide copolymer. Cells are seeded on top of these discs, and compounds slowly diffuse out, affecting proximal cells. In contrast with microtiter-based screening, this system does not involve the use of wells or walls between each compound-treated group of cells. We demonstrate detection of the effects of a single compound in a large microarray, that diverse compounds can be released in this format, and that extended release over several days is feasible. We performed a small synthetic lethal screen and identified a compound (macbecin II) that has reduced activity in cells with RNA interference-mediated decrease in the expression of tuberous sclerosis 2. Thus, we have developed a microarray-based screening system for testing the effects of small molecules on mammalian cells by using an imaging-based readout. This method will be useful to those performing small-molecule screens to discover new chemical tools and potential therapeutic agents.