Gaucher disease iPSC-derived osteoblasts have developmental and lysosomal defects that impair bone matrix deposition

Abstract

Gaucher disease (GD) is caused by bi-allelic mutations in GBA1, the gene that encodes acid β-glucocerebrosidase (GCase). Individuals affected by GD have hematologic, visceral and bone abnormalities, and in severe cases there is also neurodegeneration. To shed light on the mechanisms by which mutant GBA1 causes bone disease, we examined the ability of human induced pluripotent stem cells (iPSC) derived from patients with Types 1, 2 and 3 GD, to differentiate to osteoblasts and carry out bone deposition. Differentiation of GD iPSC to osteoblasts revealed that these cells had developmental defects and lysosomal abnormalities that interfered with bone matrix deposition. Compared with controls, GD iPSC-derived osteoblasts exhibited reduced expression of osteoblast differentiation markers, and bone matrix protein and mineral deposition were defective. Concomitantly, canonical Wnt/β catenin signaling in the mutant osteoblasts was downregulated, whereas pharmacological Wnt activation with the GSK3β inhibitor CHIR99021 rescued GD osteoblast differentiation and bone matrix deposition. Importantly, incubation with recombinant GCase (rGCase) rescued the differentiation and bone-forming ability of GD osteoblasts, demonstrating that the abnormal GD phenotype was caused by GCase deficiency. GD osteoblasts were also defective in their ability to carry out Ca2+-dependent exocytosis, a lysosomal function that is necessary for bone matrix deposition. We conclude that normal GCase enzymatic activity is required for the differentiation and bone-forming activity of osteoblasts. Furthermore, the rescue of bone matrix deposition by pharmacological activation of Wnt/β catenin in GD osteoblasts uncovers a new therapeutic target for the treatment of bone abnormalities in GD.

Bone development and remodeling in metabolic disorders

“…Several groups decided to use human induced Pluripotent Stem Cells (iPSC)‐derived osteoblasts to address the unknown of the bone pathology in GD. The main study so far is the one recently published by Ricardo Feldman's group . They showed that GD iPSC‐derived osteoblasts had developmental and lysosomal defects that impaired bone matrix deposition.…”

Versatility of Induced Pluripotent Stem Cells (iPSCs) for Improving the Knowledge on Musculoskeletal Diseases

“…Specifically, evidence that reprogrammed cells can be differentiated into osteoblasts [ 54 , 55 , 56 ], chondrocytes [ 57 , 58 , 59 , 60 ], myoblasts [ 61 ], nucleus pulposus cells [ 47 , 48 , 49 ] and tenocytes [ 62 ] has recently impacted musculoskeletal research and changed orthopedic medicine. Nevertheless, the use of iPSCs for studying the wide variety of musculoskeletal conditions has been explored to a limited extent ( Table 1 ) in comparison with conditions affecting nervous or cardiac pathologies, even when investigating genetic disorders where symptoms affect several organs or systems [ 63 , 64 , 65 , 66 ].…”

“…Panicker et al [ 66 ] using iPSCs shed light on the mechanisms that could lead to GD. This disease is developed due to alterations in the gene that encodes acid β-glucocerebrosidase and causes bone abnormalities in patients.…”

“…This disease is developed due to alterations in the gene that encodes acid β-glucocerebrosidase and causes bone abnormalities in patients. By generating iPSCs from patients with GD and differentiating them into osteoblasts, they found that these cells had developmental defects and lysosomal abnormalities that interfered with bone matrix deposition, thus discovering a new therapeutic target for the treatment of bone abnormalities in GD [ 66 ].…”

Disparate Bone Anabolic Cues Activate Bone Formation by Regulating the Rapid Lysosomal Degradation of Sclerostin Protein

“…As with many lysosomal storage disorders, patients with Gaucher disease exhibit skeletal dysplasias and low bone mass (41). Gaucher disease iPSC-derived osteoblasts display defective osteoblast differentiation and mineralization caused by defects in Wnt/-catenin signaling, an effect that is reversed by treatment with recombinant GCase (42). Accordingly, we speculated that this suppression of -catenin signaling and osteoblast differentiation and function may be a consequence of defects in sclerostin control, as sclerostin inhibits both of these processes.…”