Osteoarthritis therapy--are there still unmet needs?

Association between osteoarthritis and unmet medical needs in Korea: limitations in activities as a mediator

Background

The role of limitations in activities in relation to unmet needs is not clarified. This study aimed to analyze the effects of osteoarthritis on unmet medical needs and the mediating effects of limitations in activities.

Methods

A total number of 10,129 population aged ≥50 years were included using data from the Korean National Health and Nutrition Examination Survey from January 2010 to December 2013. Osteoarthritis was defined as Kellgren-Lawrence grade ≥ 2 in the knee, hip, and lumbar spine joints with pain reported to have lasted for ≥3 months. Limitations in activities were defined as currently experiencing restricted daily and social activities. Unmet medical needs were analyzed after they were further divided into availability, accessibility, and acceptability. Causal mediation analysis was employed to analyze mediating effects.

Results

The osteoarthritis group had a higher odds ratio (OR: 1.65; 95% confidence interval [CI], 1.56–1.75) for the total effects of osteoarthritis on unmet medical needs than the non-osteoarthritis group. Furthermore, the OR for the indirect effects mediated by limitations in activities was higher in the osteoarthritis group (OR: 1.07; 95% CI, 1.05–1.08), indicating that 13.2% of the total effect was mediated. When the analysis was further classified according to cause, the mediating effect of limitations in activities was the strongest at 23.9% for unmet medical needs due to lack of transportation accessibility.

Conclusions

Osteoarthritis exerts significant effects on the experience of unmet medical needs, and limitations in activities mediate such experiences of unmet medical needs in osteoarthritis patients.

Etoricoxib improves osteoarthritis pain relief, joint function, and quality of life in the extreme elderly

Etoricoxib is a selective cyclooxygenase-2 inhibitor, with a lower risk of gastrointestinal toxicity compared to traditional nonsteroidal anti-inflammatory drugs (NSAIDs). We evaluated the effectiveness and tolerability of etoricoxib in extremely elderly patients with chronic pain due to osteoarthritis (OA). A prospective, single-center, single-arm study was conducted, enrolling 19 extremely elderly men with OA (mean age 85.9, range 79-96 years), who responded inadequately to NSAIDs or other analgesics. Patients were switched to etoricoxib, 60 mg once daily for 4 weeks, without prior medication washout. Data were recorded before and after etoricoxib treatment. The primary endpoint was improvement in pain, assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) after the 4-week treatment. Other endpoints included the Brief Pain Inventory Short Form (BPI-SF), Treatment Satisfaction Questionnaire for Medication (TSQM), Short Form 36 (SF36), and European Quality of Life-5 Dimensions (EQ-5D). Safety and tolerability were assessed by collecting adverse events data. Pain and disability scores measured by WOMAC index were lower after treatment (pain, p ≤ 0.001; disability, p = 0.020). BPI-SF showed a significant improvement in joint function when walking and performing normal work (walking, p = 0.021; normal work, p = 0.030). SF36 scores improved for 7 out of 11 items after etoricoxib treatment (#1, p = 0.032; #4, p = 0.026; #5, p = 0.017; #6, p = 0.008; #7, p = 0.009; #8, p = 0.013; and #10, p = 0.038). EQ-5D showed a significant improvement in visual analogue scale scores (p = 0.036). TSQM results demonstrated a higher patient perception of overall satisfaction. No adverse events were reported. Pain relief, joint function, quality of life, and treatment satisfaction improved significantly in elderly patients with OA after etoricoxib administration.

Effect of the interaction between MiR-200b-3p and DNMT3A on cartilage cells of osteoarthritis patients

The aim of this research is to explore the effect of miR-200b-3p targeting DNMT3A on the proliferation and apoptosis of osteoarthritis (OA) cartilage cells. Quantitative RT-PCR was performed to analyse the expression of miR-200b-3p, DNMT3A, MMP1, MMP3, MMP9, MMP13 and COL II in normal and OA cartilage tissues. The dual-luciferase reporter assay and Western blot assay were conducted to confirm the targeting relationship between miR-200b-3p and DNMT3A. We also constructed eukaryotic expression vector to overexpress miR-200b-3p and DNMT3A. We detected the expression level of MMPs and COL II in stable transfected cartilage cells using RT-PCR and Western blot. Cell proliferation and apoptosis were evaluated using the MTS, pellet culture and Hoechst 33342 staining method. Finally, we explored the effect of miR-200b-3p targeting DNMT3A on the proliferation and apoptosis of OA cartilage cells. The results of RT-PCR indicated that both miR-200b-3p and COL II were down-regulated in OA cartilage tissues, while the expression of DNMT3A and MMPs was up-regulated in OA cartilage tissues. The expressions of DNMT3A, MMPs and COL II detected by Western blot showed the same trend of the results of RT-PCR. The dual-luciferase reporter assay and Western blot assay confirmed the targeting relationship between miR-200b-3p and DNMT3A. In overexpressed miR-200b-3p cartilage cells, DNMT3A and MMPs were significantly down-regulated, COL II was significantly up-regulated, cell viability was enhanced and apoptosis rate was decreased (P < 0.05). In overexpressed DNM3T cartilage cells, MMPs were significantly up-regulated, COL II was significantly down-regulated, cell viability was weakened and apoptosis rate was increased (P < 0.05). MiR-200b-3p inhibited the secretion of MMPs, promoted the synthesis of COL II and enhanced the growth and proliferation of OA cartilage cells through inhibiting the expression of DNMT3A.

Acupuncture for chronic pain and depression in primary care: a programme of research

Background

There has been an increase in the utilisation of acupuncture in recent years, yet the evidence base is insufficiently well established to be certain about its clinical effectiveness and cost-effectiveness. Addressing the questions related to the evidence base will reduce uncertainty and help policy- and decision-makers with regard to whether or not wider access is appropriate and provides value for money.

Aim

Our aim was to establish the most reliable evidence on the clinical effectiveness and cost-effectiveness of acupuncture for chronic pain by drawing on relevant evidence, including recent high-quality trials, and to develop fresh evidence on acupuncture for depression. To extend the evidence base we synthesised the results of published trials using robust systematic review methodology and conducted a randomised controlled trial (RCT) of acupuncture for depression.

Methods and results

We synthesised the evidence from high-quality trials of acupuncture for chronic pain, consisting of musculoskeletal pain related to the neck and low back, osteoarthritis of the knee, and headache and migraine, involving nearly 18,000 patients. In an individual patient data (IPD) pairwise meta-analysis, acupuncture was significantly better than both sham acupuncture (p < 0.001) and usual care (p < 0.001) for all conditions. Using network meta-analyses, we compared acupuncture with other physical therapies for osteoarthritis of the knee. In both an analysis of all available evidence and an analysis of a subset of better-quality trials, using aggregate-level data, we found acupuncture to be one of the more effective therapies. We developed new Bayesian methods for analysing multiple individual patient-level data sets to evaluate heterogeneous continuous outcomes. An accompanying cost-effectiveness analysis found transcutaneous electrical nerve stimulation (TENS) to be cost-effective for osteoarthritis at a threshold of £20,000 per quality-adjusted life-year when all trials were synthesised. When the analysis was restricted to trials of higher quality with adequate allocation concealment, acupuncture was cost-effective. In a RCT of acupuncture or counselling compared with usual care for depression, in which half the patients were also experiencing comorbid pain, we found acupuncture and counselling to be clinically effective and acupuncture to be cost-effective. For patients in whom acupuncture is inappropriate or unavailable, counselling is cost-effective.

Conclusion

We have provided the most robust evidence from high-quality trials on acupuncture for chronic pain. The synthesis of high-quality IPD found that acupuncture was more effective than both usual care and sham acupuncture. Acupuncture is one of the more clinically effective physical therapies for osteoarthritis and is also cost-effective if only high-quality trials are analysed. When all trials are analysed, TENS is cost-effective. Promising clinical and economic evidence on acupuncture for depression needs to be extended to other contexts and settings. For the conditions we have investigated, the drawing together of evidence on acupuncture from this programme of research has substantially reduced levels of uncertainty. We have identified directions for further research. Our research also provides a valuable basis for considering the potential role of acupuncture as a referral option in health care and enabling providers and policy-makers to make decisions based on robust sources of evidence.

Trial registration

Current Controlled Trials ISRCTN63787732.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Novel Autotaxin Inhibitors for the Treatment of Osteoarthritis Pain: Lead Optimization via Structure-Based Drug Design

In an effort to develop a novel therapeutic agent aimed at addressing the unmet need of patients with osteoarthritis pain, we set out to develop an inhibitor for autotaxin with excellent potency and physical properties to allow for the clinical investigation of autotaxin-induced nociceptive and neuropathic pain. An initial hit identification campaign led to an aminopyrimidine series with an autotaxin IC50 of 500 nM. X-ray crystallography enabled the optimization to a lead compound that demonstrated favorable potency (IC50 = 2 nM), PK properties, and a robust PK/PD relationship.

Anti-inflammatory and chondroprotective effects of atorvastatin in a cartilage explant model of osteoarthritis

OBJECTIVE

This study aimed to assess the chondroprotective potential of atorvastatin in rat's cartilage explant culture model of osteoarthritis, stimulated by interleukin-1β (IL-1β).

MATERIALS AND METHODS

The cartilage explants were treated with 20 ng/ml IL-1β alone or with 20 ng/ml IL-1β + various concentration of atorvastatin (1, 3, or 10 µM dissolved in DMSO) and incubated at 37 °C for 24 h. Also, control (0.25% DMSO), stimulated (20 ng IL-1β) and treatment (atorvastatin 10 µM) cartilage explants were incubated without and with 1400W (10 µM). After 24 h of incubation, TNF-α, PGE2, MMP-13, TIMP-1, NO, and superoxide anion formation (O2(-)) concomitant with glycosaminoglycans (GAGs) were estimated in the medium.

RESULTS

Atorvastatin inhibited IL-1β-induced GAGs release, TNF-α, MMP-13, and O2(-) with no effect on TIMP-1 and NO. In addition, the source of NO in normal and atorvastatin-treated cartilage was eNOS, while for IL-1β-stimulated cartilage it was iNOS. The cartilage degradation was associated with the combined effects of increased NO and O2 (-) rather than only NO.

CONCLUSION

The present study suggests that atorvastatin has the ability to protect cartilage degradation following IL-1β-stimulated cartilage in in vitro OA model and supports additional therapeutic application of atorvastatin in OA.

The SAR development of substituted purine derivatives as selective CB2 agonists for the treatment of chronic pain

Osteoarthritis (OA) and the associated joint pain are highly prevalent and a leading cause of disability. We have previously reported the identification of a series of purines as selective CB2 agonists and the identification of compound 1 as a clinical candidate for the treatment of joint pain. In this article we describe the further SAR development of the purine scaffold leading to the discovery of compound 6 as a potent, CNS penetrating CB2 agonist with high selectivity for CB2 over CB1 and oral efficacy in animal models of chronic OA pain.

Dynamic regulation of P-glycoprotein in human brain capillaries

Considering its role as a major blood-brain barrier gatekeeper, the dynamic regulation of the efflux transporter P-glycoprotein is of considerable functional relevance. In particular, disease-associated alterations in transport function might affect central nervous system drug efficacy. Thus, targeting regulatory signaling cascades might render a basis for novel therapeutic approaches. Using capillaries freshly prepared from patient tissue resected during epilepsy surgery, we demonstrate dynamic regulation of P-glycoprotein in human brain capillaries. Glutamate proved to up-regulate P-glycoprotein efflux transport in a significant manner via endothelial NMDA receptors. Both inhibition of cyclooxygenase-2 and antagonism at the glycine-binding site of the NMDA receptor prevented the glutamate-mediated induction of P-glycoprotein transport function in human capillaries. In conclusion, the data argue against species differences in the signaling factors increasing endothelial P-glycoprotein transport function in response to glutamate exposure. Targeting of cyclooxygenase-2 and of the NMDA receptor glycine-binding site was confirmed as an efficacious approach to control P-glycoprotein function. The findings might render a basis for translational development of add-on approaches to improve brain penetration and efficacy of drugs.

Pro-apoptotic effects of tepoxalin, a cyclooxygenase/lipoxygenase dual inhibitor, on canine synovial fibroblasts

Canine osteoarthritis occurs frequently and causes secondary synovitis. Administration of nonsteroidal anti-inflammatory drugs (NSAIDs) is one of the major therapeutic options for pain management of joint diseases. Tepoxalin has an unique property as an NSAIDs that suppresses both cyclooxygenase and lipoxygenase. The purpose of this study was to evaluate antiproliferative effects of tepoxalin on cultured canine synovial cells. Cytotoxic effects of tepoxalin, carprofen, meloxicam and AA-861 on cultured canine synoviocytes were evaluated by MTT colorimetric assay. Apoptosis was detected by morphological observations with Giemsa or annexin V/Hoechst 33342 staining and by the inhibition of caspase-3 activity with N-Ac-Asp-Glu-Val-Asp-CHO (Ac-DEVD-CHO). Cytotoxic effects of tepoxalin were evident in comparison with the effects of carprofen or meloxicam. The same tendency of cytotoxicity was observed when 5-lipoxygenase was inhibited by AA-861. The morphological findings and contradictory effects of Ac-DEVD-CHO with regard to the cytotoxicity proved the proapoptotic effects of tepoxalin. In conclusion, tepoxalin might control osteoarthritic synovitis by inducing apoptosis in proliferating synoviocytes, while most NSAIDs that selectively inhibit cyclooxygenase-2 most likely would not suppress synovial proliferation.

Using 18F-FDG microPET imaging to measure the inhibitory effects of Clematis chinensis Osbeck on the pro-inflammatory and degradative mediators associated with inflammatory arthritis

AIM OF THE STUDY

This study examined the modulating effects of Clematis chinensis Osbeck (Ranunculaeae) on pro-inflammatory and degradative mediators associated with inflammatory arthritis.

MATERIALS AND METHODS

Primary human chondrocytes (PHC) were stimulated with IL-1β or lipopolysaccharide (LPS) to induce the enhanced release of prostaglandin E(2) (PGE(2)), metalloproteinase (MMP-3 and -13), and cyclooxygenase-2 (COX-2) protein expression. The (18)F-FDG microPET imaging system was used to evaluate the anti-arthritic effects of Clematis chinensisin vivo.

RESULTS

The acetone extracted Clematis chinensis (CC6) contained the most total saponins compared to other solvent's extracts and showed significant and dose-dependent inhibitory effects on PGE(2), MMP-3, -13, and COX-2 productions by LPS-stimulated PHC. Furthermore, CC6 also exerted inhibitory effects on 2-(18)F-fluoro-2-deoxy-d-glucose ((18)F-FDG) uptake when assessed by positron emission tomography (PET) uptake in the joints and serum PGE(2) of rabbits with knee joints injected with LPS.

CONCLUSION

The results suggest the significant chondroprotective effects of Clematis chinensis are through its anti-inflammatory and MMPs inhibitory abilities. Meanwhile, we established a new analysis method to evaluate the Chinese herbal anti-arthritic effects.

Effect of Phellodendron amurense in protecting human osteoarthritic cartilage and chondrocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional medicine has been widely using Phellodendron amurense Rupr. (Rutaceae) to treat various inflammatory diseases including arthritis.

AIM OF THE STUDY

This study investigated the effects of Phellodendron amurense in protecting cartilage, including regulating the levels of aggrecanases, matrix metalloproteinases (MMPs)/tissue inhibitor of metalloproteinase (TIMP), proinflammatory cytokines and signaling of the mitogen activated protein kinase (MAPK) pathway in human osteoarticular cartilage and chondrocytes.

MATERIALS AND METHODS

Explants from human osteoarthritis cartilage were cultured alone or in IL-1α for 7 days with or without Phellodendron amurense ethanol extract or celecoxib (40, 100, 200μg/ml). The effect of Phellodendron amurense on matrix degradation induced by IL-1α in human articular cartilage was assessed by staining, and the quantities of sulfated glycosaminoglycan (GAG) and type II collagen were calculated from the culture media. The levels of aggrecanases, MMPs, TIMP, and PGE(2) in the culture media were investigated using an enzyme-linked immunosorbent assay (ELISA). In addition, reverse transcription polymerase chain reaction (RT-PCR) evaluated the mRNA expression of aggrecanases, MMPs and TIMP. Furthermore, Western blot analysis was performed to identify the roles that Phellodendron amurense played in the ERK, JNK and p38 signaling pathways.

RESULTS

Phellodendron amurense showed no evident cytotoxicity on human articular cartilage. Phellodendron amurense significantly inhibited the IL-1α-induced degradation of GAG and type II collagen from human osteoarticular cartilage in a concentration-dependent manner. Celecoxib did not significantly inhibit IL-1α-induced release of GAG and only slightly reduced type II collagen. Phellodendron amurense also dose-dependently decreased the levels of aggrecanase-1 and -2, MMP-1, -3, and -13, whereas it increased TIMP-1 expression in human osteoarticular cartilage. Celecoxib only decreased MMP-1 and MMP-13 levels in human osteoarticular cartilage. In addition, Phellodendron amurense reduced the phosphorylation of extracellular signal regulated kinase (ERK)1/2, Jun NH2-terminal kinase (JNK) and activated phospho-p38 MAPK in a dose-dependent manner in human osteoarthritic chondrocytes.

CONCLUSIONS

Phellodendron amurense inhibited osteoarticular cartilage and chondrocyte destruction by inhibiting proteoglycan release and type II collagen degradation, down-regulating aggrecanases, MMP activities and phospho-ERK1/2, JNK and p38 MAP kinase signaling, and up-regulating TIMP-1 activity. Therefore, our results suggest that Phellodendron amurense is a potential therapeutic agent to protect cartilage against OA progression.

Intra-articular drug delivery: the challenge to extend drug residence time within the joint

The rationale behind developing sustained release microsphere formulations of non-steroidal anti-inflammatory drugs (NSAIDs) administered via the intra-articular (IA) route is to minimise the systemic bioavailability and attendant side-effects associated with oral drug administration. Overall dose is reduced whilst therapeutic benefit within the joint is maintained. The potential benefits of IA therapy for osteoarthritis (OA) are not achieved using currently available medications and delivery vehicles due to the rapid clearance of therapeutic substances from the synovial space. There is a need for sustained release delivery systems if the potential of IA drug administration is to be realised. Rationally designed microspheres taken up by synovial macrophages offer a strategy to sustain drug delivery within the joint, and to deliver NSAIDs directly to pivotal inflammatory cells. The efficacy of microsphere candidates may be evaluated in large animal models of OA. The principles of IA microsphere drug delivery may also be applicable to other classes of drugs.

Modulating P-glycoprotein regulation: future perspectives for pharmacoresistant epilepsies?

Enhanced brain efflux of antiepileptic drugs by the blood-brain barrier transporter P-glycoprotein is discussed as one mechanism contributing to pharmacoresistance of epilepsies. P-glycoprotein overexpression has been proven to occur as a consequence of seizure activity. Therefore, blocking respective signaling events should help to improve brain penetration and efficacy of P-glycoprotein substrates. A series of recent studies revealed key signaling factors involved in seizure-associated transcriptional activation of P-glycoprotein. These data suggested several interesting targets, including the N-methyl-d-aspartate (NMDA) receptor, the inflammatory enzyme cyclooxygenase-2, and the prostaglandin E2 EP1 receptor. These targets have been further evaluated in rodent models, demonstrating that targeting these factors can control P-glycoprotein expression, improve antiepileptic drug brain penetration, and help to overcome pharmacoresistance. In general, the approach offers particular advantages over transporter inhibition as it preserves basal transporter function. In this review the different strategies for blocking P-glycoprotein upregulation, including their therapeutic promise and drawbacks are discussed. Moreover, pros and cons of the approach are compared to those of alternative strategies to overcome transporter-associated resistance. Regarding future perspectives of the novel approach, there is an obvious need to more clearly define the clinical relevance of transporter overexpression. In this context current efforts are discussed, including the development of imaging tools that allow an evaluation of P-glycoprotein function in individual patients.

Standardization of pain measurements in clinical trials

Standardization of the measurement of pain in clinical trials will reduce variability, thus improving the quality of the data and reducing the number of patients needed to conduct pain trials. Standardization applies to the physical and psychosocial environment surrounding the patient, and there are many elements within this environment that can be effectively controlled. For example, the appearance of the examination room can be selected for neutrality and influences from visitors and staff can be minimized. Training is an important aspect of the standardization process and should be provided to all study staff. Staff training should first provide orientation on the protocol objectives and procedures and then a thorough discussion of the pain measures being used and how assessments will be conducted. Furthermore, as the patient is ultimately responsible for assessing his or her level of pain, it is important to train the patient to make reliable and accurate assessments of pain.

Epidural local anesthetic plus corticosteroid for the treatment of cervical brachial radicular pain: single injection versus continuous infusion

BACKGROUND

Efficacy of epidural local anesthetics plus steroids for the treatment of cervicobrachial pain is uncertain.

METHODS

A prospective study randomized 160 patients with cervicobrachial pain resistant to conventional therapy. Patients were divided into 4 groups on the basis of the time between pain onset and treatment initiation: group A, 40 patients with pain onset 15 to 30 days; group B, 40 patients with pain from 31 to 60 days; group C, 40 patients, 61 to 180 days; and group D, 40 patients with pain >180 days. Patients of each group were randomized to receive an epidural block with bupivacaine and methylprednisolone at intervals of 4 to 5 days (Single injection) or continuous epidural bupivacaine every 6, 12, or 24 hours plus methylprednisolone every 4 to 5 days (Continuos epidural). The maximum duration of treatment (9 blocks in Single injection, and 30 days in Continuos epidural) was dependent on achieving Pain Control (PC) > or =80% [PC is defined by this formulae: (100) (VAS(initial)-VAS(final))/VAS(initial)]. Follow-up at 1 month and 6 months compared PC and the number of pain-free hours of sleep.

RESULTS

One hundred forty-one patients completed the study. The 4 groups had similar characteristics. At the 1-month and 6-month follow-up analysis based on the time between pain onset and treatment initiation showed that patients of group D, who received the Continuous epidural treatment, had significantly greater PC and significantly more pain-free hours of sleep compared with similar patients in Single injection.

CONCLUSIONS

Therapy with continuous epidural local anesthetic and methylprednisolone provides better control of chronic cervicobrachial pain compared with Single injection. These results are discussed with respect to the possible mechanism of action of the drugs and may relate to the physiopathologic mechanisms associated with neuronal plasticity that result in chronic pain.

Anti-inflammatory sesquiterpene-quinones from the New Zealand sponge Dysidea cf. cristagalli

The inhibition of superoxide production by human neutrophils has been used to screen New Zealand's unique biota for anti-inflammatory natural products. Bioactivity-directed isolation on an extract of the sponge Dysidea cf. cristagalli led to a new sesquiterpene-quinone (4) with anti-inflammatory activity, plus acetylated hydroquinone (3). These compounds inhibited superoxide production in vitro with IC50's of 3 microM (3) and 11 microM (4).

Therapeutic effects of PG201, an ethanol extract from herbs, through cartilage protection on collagenase-induced arthritis in rabbits

In order to assess the therapeutic effects of PG201 (an ethanol extract from herbs) on osteoarthritis, we investigated whether PG201 could suppress the disease progression of collagenase-induced arthritis (CNIA) in rabbits. The right knees of rabbits were injected intra-articularly with collagenase, and the rabbits were orally treated with distilled water (DW), PG201 (200 mg/kg) or diclofenac (DCF, 10 mg/kg) once a day for 8 weeks. Oral administration of PG201 significantly suppressed the stiffness and bone space narrowing. Cartilage erosion and GAG release (p<0.01) were considerably reduced in the knee joints. As well, the mRNA expression of matrix degradation enzymes including MMP-1, -3, and -13 was decreased. On the contrary, the concentrations of TIMP-2 in the synovial fluids were considerably amplified in the PG201 treated group (p<0.01), but not in the DCF treated group. The pathologic inflammatory molecules involved in cartilage destruction such as IL-1beta, PGE2, and NO were also diminished by PG201. Taken together, these results indicate that PG201 has therapeutic effects on CNIA through the prominent protection of cartilage. PG201 indeed has great potential as a form of treatment for osteoarthritis.

Anti-inflammatory agents for the treatment of musculoskeletal pain and arthritis

Pain produced by musculoskeletal disorders commonly misconceived as having mechanical etiology often is caused by inflammatory mechanisms. Simple analgesics (ie, those that lack anti-inflammatory action) often are used to treat musculoskeletal pain when an anti-inflammatory analgesic may be more effective for the painful condition. This review addresses the anti-inflammatory agents available for the symptomatic management of common inflammatory musculoskeletal conditions including osteoarthritis, rheumatoid arthritis, and low back pain.