1G–I. Enhanced ALP staining was anticipated, but not

verified, in the OVX group. ALP expression, while expressed consistently seen throughout osteoblastic differentiation, has been demonstrated to be condition sine qua non for mineralization as demonstrated in ALP knockout mice [34]. OVX animals suffer from accelerated bone turnover, showing stimulated osteoclastic bone resorption and reactive osteoblastic bone formation with a net result of bone loss. Even though eldecalcitol activates mature osteoblasts and induces minimodeling, the activated osteoclastic status in OVX animals may conceal any surplus in bone formation. Osteoblasts may compensate for the abnormal bone destruction by frantically synthesizing osteoid, check details while mineralization seems to be slowed down. After ovariectomy, Parameters that refer to non-mineralized bone matrix such as osteoid surface and mineralizing surface show two- and three-fold increases, respectively, when compared to Sham animals. Osteoblasts in the OVX group, therefore, may not show enhanced expression of ALP because their main function, in a scenario of untamed bone destruction, is rapid bone matrix synthesis, not its mineralization. The histological picture seen after eldecalcitol treatment is quite different from the one obtained with an intermittent PTH regimen, in which we

showed the clear proliferative and osteoblastic activation effects of that hormone [35]. Alternatively, Okuda et al. [23] have shown that ED-71, the former denomination of eldecalcitol, was capable of promoting enhancement of ALP activity and bone nodule formation in bone marrow cells in vitro,

where the influence Navitoclax mouse of osteoclastic Tyrosine-protein kinase BLK bone resorption does not exist. Under our experimental circumstances, it seems that eldecalcitol drives osteoblastic differentiation in vivo with consequent bone minimodeling without noticeable differences in the pattern of ALP staining. The histological data in this study unveiled the consistent presence of a rather particular type of bone formation after eldecalcitol treatment: bone minimodeling. Minimodeling is termed so because magnification is needed to visualize it [36], and it basically consists of bone formation not preceded by osteoclastic bone resorption with cement lines that are typically smooth [37]. Minimodeling in bone has been reported after treatment with bone anabolic agents like PTH [38] and prostaglandin E2[39]. It has been hypothesized that the mechanism guiding minimodeling-based bone formation is the resumption of osteoblastic activity of bone lining cells [40]. In our histological samples, we did observe a dominant presence of plump osteoblasts compared to that of resting bone lining cells in eldecalcitol-treated specimens (Figs. 2C–D). The absence of numerical data regarding the amount of minimodeling-based bone formation and the number of active osteoblasts as opposed to bone lining cells are limitations of this study.