Repression of osteocyte Wnt/beta-catenin signaling is an early event in the progression of renal osteodystrophy

Chronic kidney diseasemineral bone disorder (CKD-MBD) is defined by abnormalities in mineral and hormone metabolism, bone histomorphometric changes, and/or the presence of soft-tissue calcification. Emerging evidence suggests that features of CKD-MBD may occur early in disease progression and are associated with changes in osteocyte function. To identify early changes in bone, we utilized the jck mouse, a genetic model of polycystic kidney disease that exhibits progressive renal disease. At 6 weeks of age, jck mice have normal renal function and no evidence of bone disease but exhibit continual decline in renal function and death by 20 weeks of age, when approximately 40% to 60% of them have vascular calcification. Temporal changes in serum parameters were identified in jck relative to wild-type mice from 6 through 18 weeks of age and were subsequently shown to largely mirror serum changes commonly associated with clinical CKD-MBD. Bone histomorphometry revealed progressive changes associated with increased osteoclast activity and elevated bone formation relative to wild-type mice. To capture the early molecular and cellular events in the progression of CKD-MBD we examined cell-specific pathways associated with bone remodeling at the protein and/or gene expression level. Importantly, a steady increase in the number of cells expressing phosphor-Ser33/37-beta-catenin was observed both in mouse and human bones. Overall repression of Wnt/beta-catenin signaling within osteocytes occurred in conjunction with increased expression of Wnt antagonists (SOST and sFRP4) and genes associated with osteoclast activity, including receptor activator of NF-?B ligand (RANKL). The resulting increase in the RANKL/osteoprotegerin (OPG) ratio correlated with increased osteoclast activity. In late-stage disease, an apparent repression of genes associated with osteoblast function was observed. These data confirm that jck mice develop progressive biochemical changes in CKD-MBD and suggest that repression of the Wnt/beta-catenin pathway is involved in the pathogenesis of renal osteodystrophy. (C) 2012 American Society for Bone and Mineral Research.

Facial lesions caused by renal osteodystrophy in a patient with chronic renal insufficiency: a case report

PURPOSE: Chronic renal insufficiency (CRI) is the last stage of a chronic renal condition in which the kidney loses its filtration and endocrine functions. Chronic endocrine hypofunction causes generalized damage to the body known as Uremic Syndrome, which affects the central nervous system as well as the cardiovascular, hematologic, dermatologic, ophthalmic, endocrine, respiratory, gastrointestinal and skeletal systems. The present study reports the case of a female patient with CRI who presented facial osteodystrophy of the osteitis fibrosa type, and highlights the main features of this condition. CASE DESCRIPTION: A 24-year old, female, Caucasian patient presented chronic glomerulonephritis recurrence and lost the transplanted kidney five years before, undergoing arteriovenous fistula hemodialysis three times a week. She presented swelling of the left masseter area with a hard consistency on palpation, covered by intact skin, swelling at the bottom of the left atrium, with a hard consistency on palpation, a mucosa-like color and absence of inflammation signs, suggesting expansive bone lesions on the face. These features were compatible with hyperparathyroidism brown tumor and/or osteodystrophy. The CT scan showed expansive bone lesions of heterogeneous appearance on the left jaw, maxilla/nasal floor, and right frontotemporal suture areas. The clinical and histopathological characteristics of the lesion, in association with PHT hormone high serum levels led to renal osteodystrophy diagnosis. The patient was referred to the nephrology services. CONCLUSION: Osteodystrophic bone alterations have a high prevalence in renal disease patients, and the dentist must take these alterations into consideration in bone lesion diagnosis for this specific group of patients.