Lysyl oxidase modulates the osteoblast differentiation of primary mouse calvaria cells

Abstract

Lysyl oxidase (LOX) is an extracellular amine oxidase that mediates the formation of collagen fibers. Thus far, five LOX family genes [LOX, lysyl oxidase-like (LOXL)1, LOXL2, LOXL3 and LOXL4] have been identified in humans, each encoding the characteristic C-terminal domains that are required for amine oxidase activity. During osteoblastogenesis, collagen fibers function as a three-dimensional scaffold for organizing mineral deposition. In this study, to assess the functional roles of the LOX family members in osteoblastogenesis, we investigated the temporal expression of these genes as a function of phenotypic development during the osteoblast differentiation of primary cultured mouse calvaria cells. Of the LOX family members, only LOX was prominently expressed during osteoblast differentiation. LOX expression was highest on day 9 of differentiation, as shown by RT-PCR and western blot analysis. The expression pattern of collagen, type I, alpha 2 (COL1A2), which encodes the α2-chain of mouse collagen type I, was similar to that of LOX. The total amine oxidase activity of the differentiating calvaria cells exhibited a temporal pattern that paralleled LOX expression, reaching the highest level on day 9 of differentiation. We also noted that the inhibition of the amine oxidase activity of LOX significantly suppressed both mineral nodule formation and the expression of osteoblast marker genes during the differentiation of primary calvaria cells. Taken together, these findings suggest that the LOX-mediated organization of collagen fibers in the extracellular matrix is an important regulator of osteoblastogenesis.

Impaired Gastric Hormone Regulation of Osteoblasts and Lysyl Oxidase Drives Bone Disease in Diabetes Mellitus

“…Data indicated that LOX was the predominant isoform expressed in the nondiabetic primary osteoblasts, followed by LOXL1 (Fig. A ), consistent with data published by others . We then performed relative quantification of each isoform from qRT‐PCR data in the diabetic versus nondiabetic cells using GAPDH as internal control.…”

“…4A), consistent with data published by others. (46) We then performed relative quantification of each isoform from qRT-PCR data in the diabetic versus nondiabetic cells using GAPDH as internal control. Results show that diabetic primary bone cells showed a 90% reduction in LOX expression, whereas LOXL1 was reduced by 50% and LOXL2 to LOXL4 were unaffected ( Figure 4B).…”

Enzymatic and non-enzymatic functions of the lysyl oxidase family in bone

“…These early studies did not measure the role of each LOX isoform in osteoblast differentiation or collagen accumulation, and gene expression studies were done only on the LOX isoform. A recent study has indicated that LOX is by far the principal lysyl oxidase isoform expressed in developing osteoblasts in vitro [61], with kinetics of expression similar to an earlier publication focused only on LOX [60]. Calvaria osteoblasts from LOX−/− perinatal mice exhibited deficient osteoblast differentiation and abnormal collagen fibril diameters [62].…”

Genes involved in angiogenesis and circulatory system development are differentially expressed in porcine epithelial oviductal cells during long-term primary in vitro culture – a transcriptomic study

“…Although our research doesn't indicate it, according to literature COL1A2 also interacts with another up-regulated gene -LOX (lysyl oxidase). LOX mediates collagen fiber organization in the ECM which is important in osteoblastogenesis regulation [42]. The aberrations in collagen type I cross-linking have been observed in bone disorders including osteopetrosis or osteoporosis [43,44].…”