Pathogenesis of tendinous xanthoma: histopathological study of the extremities of Watanabe heritable hyperlipidemic rabbits

Mild hypercholesterolemia impacts achilles sub-tendon mechanical properties in young rats

BACKGROUND

Hypercholesterolemia is associated with tendon pathology, but the reasons underpinning this relationship are not well understood. Cholesterol can accumulate in the tendon non-collagenous matrix which may affect both global and local tissue mechanics. Changes to the local strain environment within tendon may have significant implications for mechanosensitive tenocytes. Here, we investigated the association between elevated blood cholesterol and presence of tendon lipids in the Achilles tendon. We expected lipids to be localised in the proteoglycan-rich inter-sub-tendon matrix (ISTM), therefore we also sought to examine the impact of this on the biomechanical and viscoelastic properties of the ISTM.

METHODS

The Achilles tendons of 32 young wild-type (SD) and 32 apolipoprotein E knock-out rats (ApoE^-/-) were harvested at 15.6 ± 2.3 weeks of age. 32 specimens underwent histological examination to assess the distribution of lipids throughout sub-tendons and ISTM. The remaining specimens were prepared for biomechanical testing, where the ISTM between the gastrocnemius and soleus sub-tendons was subjected to shear load mechanical testing. A sub-set of tests were video recorded to enable a strain analysis.

RESULTS

ApoE^-/- serum cholesterol was double that of SD rats (mean 2.25 vs. 1.10 mg/ml, p < 0.001) indicating a relatively mild hypercholesterolemia phenotype. Nonetheless, we found histological evidence of esterified lipids in the ISTM and unesterified lipids in the sub-tendons, although the location or intensity of staining was not appreciably different between rat strains. Despite a lack of observable histological differences in lipid content between groups, there were significant differences in the mechanical and viscoelastic behaviour of the Achilles sub-tendon matrix.

CONCLUSION

Even slightly elevated cholesterol may result in subtle changes to tendon biomechanical properties and hence injury risk. The young age of our cohort and the mild phenotype of our ApoE^-/- rats are likely to have limited our findings and so we also conclude that the ApoE^-/- rat model is not well suited for investigating the biomechanical impact of tendon xanthomas on Achilles sub-tendon function.

The impact of mild hypercholesterolemia on injury repair in the rat patellar tendon

Hypercholesterolemia is associated with tendon pathology and injury prevalence. Lipids can accumulate in the tendon's extracellular spaces, which may disrupt its hierarchical structure and the tenocytes physicochemical environment. We hypothesized that the tendon's ability to repair after injury would be attenuated with elevated cholesterol levels, leading to inferior mechanical properties. Fifty wild-type (sSD) and 50 apolipoprotein E knock-out rats (ApoE^{-/ -} ) were given a unilateral patellar tendon (PT) injury at 12 weeks old; the uninjured limb served as a control. Animals were euthanized at 3-, 14,- or 42-days postinjury and PT healing was investigated. ApoE^{-/ -} serum cholesterol was double that of SD rats (mean: 2.12 vs. 0.99 mg/mL, p < 0.001) and cholesterol level was related to the expression of several genes after injury; notably rats with higher cholesterol demonstrated a blunted inflammatory response. There was little physical evidence of tendon lipid content or differences in injury repair between groups, therefore we were not surprised that tendon mechanical or material properties did not differ between strains. The young age and the mild phenotype of our ApoE^{-/ -} rats might explain these findings. Hydroxyproline content was positively related to total blood cholesterol, but this result did not translate to observable biomechanical differences, perhaps due to the narrow range of cholesterol levels observed. Tendon inflammatory and healing activity is modulated at the mRNA level even with a mild hypercholesterolemia. These important initial impacts need to be investigated as they may contribute to the known consequences of cholesterol on tendons in humans.

Is there a relation between plantar fasciitis and total cholesterol levels?

BACKGROUND

The main objective of this study is to investigate the relationship between hypercholesterolemia and Plantar Fasciitis (PF).

METHODS

The study includes patients who presented to the orthopedics outpatient clinic with heel pain and were diagnosed with PF. The control group was composed of patients who came to the orthopedics outpatient clinic, with complaints other than heel pain. The two groups were compared in terms of epidemiological data, total cholesterol (TC) levels, and hypercholesterolemia prevalence. We also performed an in-group analysis of PF patients in terms of age, sex, body mass index, and duration of symptoms.

RESULTS

There were 238 patients (mean age, 46.7) in the PF group and 240 patients (mean age, 47.9) in the control group. There was a significant difference between the PF group and the control group in TC levels (207.6 ± 47.5 versus 195.1 ± 30.1, p = 0.001). Hypercholesterolemia (TC level > 240 mg/dL) was found in 22.7% (n = 54) of the patients in the PF group whereas in the control group this rate was 10.8% (n = 26) (p < 0.001). It was seen that the TC levels were significantly higher in patients over the age of 45 in the PF group (p = 0.038). We also found that TC levels were higher in PF patients with symptoms for longer than a year (p = 0.026).

CONCLUSION

Significantly higher TC levels were found in PF patients in comparison with other orthopedic outpatients. Besides, being over the age of 45 and having a duration of symptoms longer than a year is associated with higher cholesterol levels for PF patients.

LEVEL OF CLINICAL EVIDENCE

4.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Rabbit

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the laboratory rabbit used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

The History of the WHHL Rabbit, an Animal Model of Familial Hypercholesterolemia (I) - Contribution to the Elucidation of the Pathophysiology of Human Hypercholesterolemia and Coronary Heart Disease

Animal models that closely resemble both human disease findings and their onset mechanism have contributed to the advancement of biomedical science. The Watanabe heritable hyperlipidemic (WHHL) rabbit and its advanced strains (the coronary atherosclerosis-prone and the myocardial infarction-prone WHHL rabbits) developed at Kobe University (Kobe, Japan), an animal model of human familial hypercholesterolemia, have greatly contributed to the elucidation of the pathophysiology of human lipoprotein metabolism, hypercholesterolemia, atherosclerosis, and coronary heart disease, as described below. 1) The main part of human lipoprotein metabolism has been elucidated, and the low-density lipoprotein (LDL) receptor pathway hypothesis derived from studies using fibroblasts was proven in vivo. 2) Oxidized LDL accumulates in the arterial wall, monocyte adhesion molecules are expressed on arterial endothelial cells, and monocyte-derived macrophages infiltrate the arterial intima, resulting in the formation and progression of atherosclerosis. 3) Coronary lesions differ from aortic lesions in lesion composition. 4) Factors involved in the development of atherosclerosis differ between the coronary arteries and aorta. 5) The rupture of coronary lesions requires secondary mechanical forces, such as spasm, in addition to vulnerable plaques. 6) Specific lipid molecules in the blood have been identified as markers of the progression of coronary lesions. At the end of the breeding of the WHHL rabbit family at Kobe University, this review summarizes the history of the development of the WHHL rabbit family and their contribution to biomedical science.

Xanthoma Combined With Gout Infiltration of the Achilles Tendon: A Case Report

Xanthoma is a rare condition mostly caused by hyperlipidemia. The pathogenesis of gout is hyperuricemia, which is caused by a disorder of purine metabolism and/or a decrease in uric acid excretion. Xanthoma combined with gout is very rare. This case report presents magnetic resonance images of a case of xanthoma combined with gout infiltration of the Achilles tendon.

Tendon pathology in hypercholesterolaemia patients: Epidemiology, pathogenesis and management

Tendon pathology is a general term used to describe a group of musculoskeletal conditions related to tendons and surrounding structures. There is only limited evidence available regarding the exact aetiology and natural history of tendon pathology. In hypercholesterolaemia environments, lipids could accumulate within the extracellular matrix of the tendon and thus affect the mechanical properties of the tendon. Current evidence suggested that hypercholesterolaemia was an important risk factor in the development and progression of tendon pathology. The severity of hypercholesterolaemia was correlated with the severity of tendon pathology.

The translational potential of this article: Hypercholesterolaemia lead to the structural, inflammatory and mechanical changes in tendons, which predispose hypercholesterolaemia patients to a greater risk of tendon pathology. Measurements of serum cholesterol are suggested to be performed in patients presenting with tendon pathology. The strict control of hypercholesterolaemia would mitigate the development and progression of tendon pathology.

Perioperative Serum Lipid Status and Statin Use Affect the Revision Surgery Rate After Arthroscopic Rotator Cuff Repair

BACKGROUND

Recent animal studies have demonstrated that hyperlipidemia is associated with poor tendon-bone healing after rotator cuff repair; however, these findings have not been substantiated in human studies.

PURPOSE

To examine any association between hyperlipidemia and the failure of arthroscopic rotator cuff repair requiring revision surgery and to investigate whether the use of statin lipid-lowering agents had any influence on observed associations.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From a national insurance database, patients who underwent arthroscopic rotator cuff repair with perioperative lipid levels (total cholesterol, low-density lipoprotein [LDL], and triglycerides) recorded were reviewed. For each lipid test, patients were stratified into normal, moderate, and high groups based on published standards. For the total cholesterol and LDL cohorts, a subgroup analysis of patients stratified by statin use was performed. The primary outcome measure was ipsilateral revision rotator cuff surgery, including revision repair or debridement. A logistic regression analysis controlling for patient demographics and comorbidities was utilized for comparison.

RESULTS

There were 30,638 patients included in the study. The rate of revision rotator cuff surgery was significantly increased in patients with moderate (odds ratio [OR], 1.20; 95% CI, 1.03-1.40; P = .022) and high total cholesterol levels (OR, 1.36; 95% CI, 1.10-1.55; P = .006) compared with patients with normal total cholesterol levels perioperatively. Within each of these groups, patients without statin use had significantly higher rates of revision surgery, while those with statin prescriptions did not. The absolute risk reduction for statin use ranged from 0.24% to 1.87% when stratified by the total cholesterol level, yielding a number needed to treat from 54 to 408 patients. The rate of revision surgery was significantly increased in patients with moderate (OR, 1.24; 95% CI, 1.10-1.41; P = .001) and high LDL levels (OR, 1.46; 95% CI, 1.08-1.99; P = .014) compared with patients with normal LDL levels perioperatively. Again, patients without statin prescriptions had significantly increased rates of revision surgery, whereas patients with statin use did not. The absolute risk reduction for statin use ranged from 0.26% to 1.89% when stratified by the LDL level, yielding a number needed to treat from 53 to 387 patients. There were no significant differences in the rates of revision rotator cuff surgery between patients with moderate and high triglyceride levels compared with patients with normal triglyceride levels.

CONCLUSION

The present study found a significant association between moderate and high perioperative total cholesterol and LDL levels and the rate of revision surgery after primary arthroscopic rotator cuff repair. Furthermore, the use of statin agents appeared to mitigate the need for revision rotator cuff repair. Further prospective studies are necessary to validate these preliminary findings and determine if better perioperative lipid control can improve clinical outcomes after arthroscopic rotator cuff repair.

Marked Multiple Tendinitis at the Onset of Rheumatoid Arthritis in a Patient with Heterozygous Familial Hypercholesterolemia: Ultrasonographic Observation

A 59-year-old woman who had been diagnosed with heterozygous familial hypercholesterolemia developed rheumatoid arthritis (RA). She presented with marked tendinitis of the Achilles tendons, patellar tendons, and finger extensor tendons at the onset of RA. Ultrasonographic examination revealed that tendon lesions were predominantly tendinitis rather than paratenonitis, and that the tendinitis was of the noninsertional variety, rather than the insertional variety. Preexisting tendon xanthomas might have contributed to the unusually dominant noninsertional tendinitis of multiple tendons.

Xanthomatous Infiltration of the Rotator Cuff and Long Head of Biceps with Rotator Cuff Tear in a Patient with Mixed Hyperlipidemia: A Case Report with MRI Imaging

Xanthomatous infiltration may rarely affect the rotator cuff muscles and long head of the biceps tendon. It is the deposition of cholesterol within the rotator cuff muscles and long head of the biceps tendon resulting from hyperlipidemia, specifically high triglyceride and total cholesterol levels. As more commonly seen with xanthomatous infiltration and tear of the Achilles tendon, there may also be an association with rotator cuff tendon deposition and tear. MRI images of xanthomatous infiltration with rotator cuff tear in a 77 year old man with hyperlipidemia are detailed in the following case report.