Altered postnatal expression of insulin-like growth factor-I (IGF-I) and type X collagen preceding the Perthes' disease-like lesion of a rat model

Legg-Calve-Perthes' disease: an opportunity to prevent blindness?

Legg-Calve-Perthes' disease (LCP) is defined as avascular necrosis of the femoral head in a child and may present to a variety of disciplines from general practice to orthopaedics, paediatrics, rheumatology and more. The Stickler syndromes are a group of disorders of type II, IX and XI collagen associated with hip dysplasia, retinal detachment, deafness and cleft palate. The pathogenesis of LCP disease remains an enigma but there have been a small number of cases reporting variants in the gene encoding the α1 chain of type II collagen (COL2A1). Variants in COL2A1 are known to cause type 1 Stickler syndrome (MIM 108300, 609508), which is a connective tissue disorder with a very high risk of childhood blindness, and it is also associated with dysplastic development of the femoral head. It is unclear whether COL2A1 variants make a definitive contribution to both disorders, or whether the two are indistinguishable using current clinical diagnostic techniques. In this paper, we compare the two conditions and present a case series of 19 patients with genetically confirmed type 1 Stickler syndrome presenting with a historic diagnosis of LCP. In contrast to isolated LCP, children with type 1 Stickler syndrome have a very high risk of blindness from giant retinal tear detachment, but this is now largely preventable if a timely diagnosis is made. This paper highlights the potential for avoidable blindness in children presenting to clinicians with features suggestive of LCP disease but with underlying Stickler syndrome and proposes a simple scoring system to assist clinicians.

MicroRNA sequence analysis of plasma exosomes in early Legg-Calvé-Perthes disease

The pathogenesis of Legg-Calvé-Perthes disease (LCPD) has not been fully elucidated, and studies on epigenetic changes that may contribute to the pathogenesis of LCPD are rare. MicroRNAs (miRNAs) are epigenetic modifications that play a critical role in gene regulation. This study aimed to determine the expression profiles of circulating exosomal miRNAs and examine the role of exosomal miRNAs in LCPD. Exosomes were extracted from the plasma of three patients with LCPD and three matched healthy volunteers. Total exosomal miRNAs were isolated, and next-generation sequencing and bioinformatic approaches were performed. The top 10 most differentially upregulated miRNAs were identified, and qRT-PCR validation was performed using additional 10 matches. In Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, plasma exosomes were used in verifying osteoclastogenesis and the endothelial dysfunction phenotypes involved. The elevated miRNAs in LCPD plasma exosomes were tested for osteoclastogenesis and endothelial dysfunction in vitro. Sequencing results revealed the expression profiles of plasma exosomal miRNAs with differential expression from the DESeq-identified miRNA profiles in LCPD versus controls in a pairwise comparison. Gene Ontology and KEGG pathway analyses indicated that the predicted target genes of different miRNAs were mainly enriched in the endothelial and osteoclast cells related to signaling pathways. Functional phenotype experiments showed that the plasma exosomes in the LCPD group promoted osteoclastogenesis and endothelial cell dysfunction. qRT-PCR experiments showed that nine miRNAs in circulating exosomes in LCPD patients were higher than those in the healthy controls. miR-3133, miR-4644, miR-4693-3p, and miR-4693-5p promoted endothelial dysfunction, and miR-3133, miR-4693-3p, miR-4693-5p, miR-141-3p and miR-30a promoted osteoclastogenesis in vitro. This study demonstrated that plasma exosomes from LCPD promote endothelial cell dysfunction and osteoclastogenesis likely through their miRNAs, which might contribute to the development of LCPD.

Osteonecrosis of Femoral Head is Associated with Congenital Multiple Pituitary Hormone Deficiency: Report of Three Cases and Literature Review

Objective: Pituitary hormones are critical for bone development and maturation. It is currently unknown whether congenital multiple pituitary hormone deficiency (CMPHD) is associated with osteonecrosis of femoral head (ONFH). Methods: Clinical presentations and hormonal profiles of three patients with CMPHD and ONFH were retrospectively described. The incidence of ONFH in this population was studied. Results: (1) Congenital hypopituitarism was diagnosed in three patients. Femoral epiphyseal fusion in these patients was markedly delayed, and they had very low bone mineral density. (2) Hip pain, which is the main presentation of ONFH, occurred at the age of 20-30 years. ONFH induced by excessive glucocorticoids was excluded. (3) The estimated incidence of ONFH was approximately 694:100,000. Conclusions: CMPHD, especially a lack of growth and sex hormones, may contribute to ONFH.

Bilateral coxofemoral degenerative joint disease in a juvenile male yellow-eyed penguin (Megadyptes antipodes)

A juvenile, male, yellow-eyed penguin (Megadyptes antipodes) with abnormal stance and decreased mobility was captured, held in captivity for approximately 6 weeks, and euthanized due to continued clinical signs. Radiographically, there was bilateral degenerative joint disease with coxofemoral periarticular osteophyte formation. Grossly, the bird had bilaterally distended, thickened coxofemoral joints with increased laxity, and small, roughened and angular femoral heads. Histologically, the left femoral articular cartilage and subchondral bone were absent, and the remaining femoral head consisted of trabecular bone overlain by fibrin and granulation tissue. There was no gross or histological evidence of infection. The historic, gross, radiographic, and histopathologic findings were most consistent with bilateral aseptic femoral head degeneration resulting in degenerative joint disease. Although the chronicity of the lesions masked the initiating cause, the probable underlying causes of aseptic bilateral femoral head degeneration in a young animal are osteonecrosis and osteochondrosis of the femoral head. To our knowledge, this is the first reported case of bilateral coxofemoral degenerative joint disease in a penguin.

ACTH protects against glucocorticoid-induced osteonecrosis of bone

We report that adrenocorticotropic hormone (ACTH) protects against osteonecrosis of the femoral head induced by depot methylprednisolone acetate (depomedrol). This therapeutic response likely arises from enhanced osteoblastic support and the stimulation of VEGF by ACTH; the latter is largely responsible for maintaining the fine vascular network that surrounds highly remodeling bone. We suggest examining the efficacy of ACTH in preventing human osteonecrosis, a devastating complication of glucocorticoid therapy.

Osteonecrosis of femoral head in the stroke-prone spontaneously hypertensive rats, especially old rats

The average life span of stroke-prone spontaneously hypertensive rats (SHRSP) is about eight months. Male SHRSPs at 40 weeks old were used to study the idiopathic osteonecrosis of the femoral head (ION). The control group showed about 40% old necrosis and 20% early necrosis. The group administered with steroid hormone showed an increasing degeneration of adipocyte in the bone marrow, and 20% fresh necrosis was recognized. Furthermore, we observed the adipocyte change as well as early necrosis occurring among old necrosis sites. The study of aged rats may provide further understanding into the pathogenesis of ION.

A histological and ultrastructural study of the iliac crest apophysis in Legg-Calve-Perthes disease

BACKGROUND

Legg-Calve-Perthes disease (LCPD) is a common hip disorder in children characterized by avascular necrosis of the proximal capital femoral epiphysis. The underlying etiology of the vascular disturbance is still unknown, but it is suggested that LCPD may be a part of a generalized constitutional disorder associated with growth disturbance of bone and cartilage tissue. In this study, the biopsy specimens of the iliac crest apophysis from LCPD patients were examined histologically and ultrastructurally to determine preexisting generalized abnormalities of endochondral ossification.

METHODS

Iliac crest apophysis cartilage was taken during Salter innominate osteotomy from 11 children (8 boys and 3 girls) with LCPD at an average age of 7.8 years. As controls, the samples were also obtained from 10 children (2 boys and 8 girls) at an average age of 6.3 years undergoing Salter osteotomy due to residual acetabular dysplasia after reduction of developmental dysplasia of the hip. Each iliac crest apophysis specimen was examined histologically (Toluidine blue staining and Sudan III staining) and ultrastructurally.

RESULTS

Although there were no obvious differences in Toluidine blue-stained sections of the iliac crest cartilage between LCPD and control patients, the Sudan III-positive chondrocytes in the resting cartilage were more prominent in the LCPD specimens than in the control specimens. These sudanophilic granules were confirmed to be lipid droplets by electron microscopic examinations. Ultrastructural examinations of the resting chondrocytes from 3 LCPD patients demonstrated numerous cytoplasmic inclusion bodies with electron dense materials, which were similar to those seen in some of the mucopolysaccharidoses.

CONCLUSIONS

Increased lipid droplets and numerous cytoplasmic inclusions filled with fibrillar materials were suggestive of the initial metabolic changes of the chondrocytes, which may have a pivotal role in degenerating matrix and lead to vulnerability of the cartilage tissue. Our results indicated that generalized insufficiency in growth cartilage metabolism may be related to the onset of the disease in some LCPD patients.

Zoledronic acid improves femoral head sphericity in a rat model of perthes disease

We hypothesized that the bisphosphonate zoledronic acid (ZA) could improve femoral head sphericity in Perthes disease by changing the balance between bone resorption and new bone formation. This study tests the effect of ZA in an established model of Perthes disease, the spontaneously hypertensive rat (SHR). One hundred and twenty 4-week old SHR rats were divided into three groups of 40: saline monthly, 0.015 mg/kg ZA weekly, or 0.05 mg/kg ZA monthly. At 15 weeks DXA measurements documented that femoral head BMD was increased by 18% in ZA weekly and 21% in ZA monthly compared to controls (p<0.01). Femoral head sphericity in animals with osteonecrosis was improved in ZA-treatment groups (p<0.01) as measured by epiphyseal quotient (EQ). The proportion of "flat" heads (EQ0.40) was significantly reduced from 32% in saline-treated animals to 12% in weekly ZA and 3% in monthly ZA (p<0.01). Histologically there was a similar prevalence of osteonecrosis in all groups. The prevalence of ossification delay was significantly reduced by ZA treatment (p<0.01). Zoledronic acid favorably altered femoral head shape in this spontaneous model of osteonecrosis in growing rats. Translation of these results to Perthes disease could mean that deformity of the femoral head may be modified in children, perhaps reducing the need for surgical intervention in childhood and adult life.

Osteonecrosis of the femoral head of laboratory animals: the lessons learned from a comparative study of osteonecrosis in man and experimental animals

Animal models of osteonecrosis of the femoral head are indispensable to the understanding of successful treatment modalities for avascular necrosis of the femoral head in adults and in children with Legg-Calvé-Perthes disease. Many of these models adequately reflect the current "vascular deprivation" theory regarding the etiology of the disease. In addition to spontaneous occurrence, surgical- and corticosteroid-induced models are suitable, common experimental ones. Osteonecrosis of spontaneously hypertensive rats appears to be due to defective bone formation and compression of the arteries entering the femoral head at its lateral facets by daily weight-bearing loads. Successful modeling of surgical-induced femoral capital necrosis can be a challenge in animals with a dual epiphyseal blood supply. High doses of corticosteroids are a pivotal risk factor in the development of osteonecrosis. The pathogenesis of corticosteroid-induced osteonecrosis likely resides in reduced blood flow. Steroids may reduce blood flow by numerous mechanisms, including marrow adipocytic hypertrophy leading to sinusoidal compression, venous stasis and, eventually, obstruction of the arteries, and arterial occlusion by fat emboli and lipid-loaded fibrin-platelet thrombi. Other, less common varieties of osteonecrosis include those secondary to endotoxin-induced disseminated intravascular coagulation, immune reactions, immoderately low or high temperatures, and high-impact-related injuries. Common to these diverse forms of osteonecrosis are fibrin thrombi clogging arterioles and small arteries.

Pathogenesis and natural history of osteonecrosis

BACKGROUND AND OBJECTIVES

Osteonecrosis (avascular necrosis) is a relatively common disorder seen by both rheumatologists and orthopedic surgeons. The vast majority of cases are secondary to trauma. However, for non-traumatic cases, there often remains a diagnostic challenge in defining the cause of bone death. The goal of this article is to review data extensively in the medical literature with respect to the pathogenesis of osteonecrosis, its natural history, and treatment.

METHODS

A review of 524 studies on osteonecrosis was performed, of which 213 were selected and cited.

RESULTS

Non-traumatic osteonecrosis has been associated with corticosteroid usage, alcoholism, infections, hyperbaric events, storage disorders, marrow infiltrating diseases, coagulation defects, and some autoimmune diseases. However, a large number of idiopathic cases of osteonecrosis have been described without an obvious etiologic factor. Although corticosteroids can produce osteonecrosis, careful history is always warranted to identify other risk factors. The pathogenesis of non-traumatic osteonecrosis appears to involve vascular compromise, bone and cell death, or defective bone repair as the primary event. Our understanding of the pathogenesis of osteonecrosis is now much better defined and skeletal scintigraphy and magnetic resonance imaging have enhanced diagnosis greatly. Early detection is important because the prognosis depends on the stage and location of the lesion, although the treatment of femoral head osteonecrosis remains primarily a surgical one.

CONCLUSIONS

Osteonecrosis has been associated with a wide range of conditions. Many theories have been proposed to decipher the mechanism behind the development of osteonecrosis but none have been proven. Because osteonecrosis may affect patients with a variety of risk factors, it is important that caregivers have a heightened index of suspicion. Early detection may affect prognosis because prognosis is dependent on the stage and location of the disease. In particular, the disease should be suspected in patients with a history of steroid usage, especially in conjunction with other illnesses that predispose the patient to osteonecrosis.

RELEVANCE

A better understanding of the pathophysiology, diagnosis and treatment of osteonecrosis will help the physician determine which patients are at risk for osteonecrosis, facilitating early diagnosis and better treatment options.

Roles of growth hormone and insulin-like growth factor 1 in mouse postnatal growth

To examine the relationship between growth hormone (GH) and insulin-like growth factor 1 (IGF1) in controlling postnatal growth, we performed a comparative analysis of dwarfing phenotypes manifested in mouse mutants lacking GH receptor, IGF1, or both. This genetic study has provided conclusive evidence demonstrating that GH and IGF1 promote postnatal growth by both independent and common functions, as the growth retardation of double Ghr/Igf1 nullizygotes is more severe than that observed with either class of single mutant. In fact, the body weight of these double-mutant mice is only approximately 17% of normal and, in absolute magnitude ( approximately 5 g), only twice that of the smallest known mammal. Thus, the growth control pathway in which the components of the GH/IGF1 signaling systems participate constitutes the major determinant of body size. To complement this conclusion mainly based on extensive growth curve analyses, we also present details concerning the involvement of the GH/IGF1 axis in linear growth derived by a developmental study of long bone ossification in the mutants.