Ucma, also known as Upper zone of growth plate and Cartilage Matrix Associated protein or Gla Rich Protein (GRP), is a vitamin K-dependent protein. It plays important roles in regulating mineralization, especially in processes related to vascular smooth muscle cell (VSMC) calcification and osteochondrogenic differentiation. It is involved in the SMAD-dependent BMP signalling pathway, which is crucial for these processes [1,3].

Ucma-/-mice showed increased mineralization and expression of osteo/chondrogenic markers in VSMCs, suggesting that Ucma is an inhibitor of mineralization [1]. However, surprisingly, normal skeletal development was not affected in Ucma-deficient mice, though Ucma might be involved in skeletal homeostasis and mechanical properties during challenging conditions like ageing or disease [2].

In conclusion, Ucma is an important regulator of mineralization and osteochondrogenic differentiation. Studies using Ucma-deficient mouse models have revealed its non-essential role in normal skeletal development but potential significance in skeletal homeostasis and disease-related conditions such as vascular calcification and perhaps osteoarthritis, where its levels are associated with disease severity [1,2,4].