Effect of Combined Teriparatide and Monthly Risedronate Therapy on Cancellous Bone Mass in Orchidectomized Rats: A Bone Histomorphometry Study

Mesenchymal stem cell-based therapy for osteoporotic bones: Effects of the interaction between cells from healthy and osteoporotic rats on osteoblast differentiation and bone repair

AIMS

Cell therapy utilizing mesenchymal stem cells (MSCs) from healthy donors (HE-MSCs) is a promising strategy for treating osteoporotic bone defects. This study investigated the effects of interaction between HE-MSCs and MSCs from osteoporotic donors (ORX-MSCs) on osteoblast differentiation of MSCs and of HE-MSCs on bone formation in calvarial defects of osteoporotic rats.

MATERIALS AND METHODS

Osteoporosis was induced by orchiectomy (ORX) and its effects on the bone were evaluated by femur microtomography (μCT) and osteoblast differentiation of bone marrow MSCs. HE- and ORX-MSCs were cocultured, and osteoblast differentiation was evaluated using genotypic and phenotypic parameters. HE-MSCs were injected into the calvarial defects of osteoporotic rats, and bone formation was evaluated by μCT, histology, and gene expression of osteoblast markers.

KEY FINDINGS

ORX-induced osteoporosis was revealed by reduced bone morphometric parameters and osteoblast differentiation in ORX-MSCs. HE-MSCs partially recovered the osteogenic potential of ORX-MSCs, whereas HE-MSCs were mildly affected by ORX-MSCs. Additionally, the bone morphogenetic protein and wingless-related integration site signaling pathway components were similarly modulated in cocultures involving ORX-MSCs. HE-MSCs induced meaningful bone formation, highlighting the effectiveness of cell therapy even in osteoporotic bones.

SIGNIFICANCE

These results provide new perspectives on the development of cell-based therapies to regenerate bone defects in patients with disorders that affect bone tissue.

The effect of caponization on tibia bone histomorphometric properties of crossbred roosters

The negative effect of caponization on the structural, geometric and mechanical parameters of femur and tibia has been shown in a few studies. Nevertheless, its influence on tibia bone microarchitecture is still largely unknown. Therefore, this study aimed to assess the effect of castration on the microstructural parameters of the trabecular and compact bone of tibia bone in crossbred chickens. The experiment involved 96 roosters derived from crossing Yellowleg Partridge hens ([Formula: see text]-33) and Rhode Island Red cockerels (R-11) fattened until the 16th, 20th and 24th week of life. Animals were randomly divided into 2 groups of 48 each. Group I (control) consisted of intact roosters and group II (experimental) consisted of birds subjected to caponization at the 8th week of age. The castration surgery had no influence on some properties within compact bone such as osteon diameter On.Dm, osteon perimeter On.Pm, osteon area On.Ar, osteocyte lacunar number Ot.Lc.N, osteon bone area On.B.Ar, osteon wall thickness On.W.Th as well as thick-mature collagen content in all analyzed age groups of animals. Nevertheless, our results demonstrate that castration caused a decrease of Haversian canal area Hc.Ar, osteocyte lacunar area Ot.Lc.Ar and osteocyte lacunar porosity Ot.Lc.Po among the 16-week-old birds, decrease of Haversian canal perimeter Hc.Pm and increase of fraction of bone area On.B.Ar/On.Ar among 16- and 24-week-old individuals and also an increase of osteocyte lacunar density Ot.Lc.Dn in the osteons of the oldest roosters. Additionally, some microstructural parameters of trabecular bone show the negative effect of caponization. The youngest 16-week-old capons were characterized by thinnin the trabecular in the epiphysis part of tibia. Moreover, in the case of 24-week-old, there is an increase in the trabecular separation Tb.Sp with simultaneous decrease of trabecular number Tb.N compared to roosters, which may suggest the increase of the bone resorption among the oldest individuals. The increased bone turnover in the epiphysis part of the tibia bone also indicates changes in the collagen fibers distribution, where among 20-week-old animals there is a decrease in the content of immature thin collagen fibers with simultaneous increase in the content of mature thick collagen fibers. Furthermore, among the oldest 24-week-old individuals we can observe the increased thick-to-thin collagen ratio, which may be a sign of slowing down in bone formation.

Localization of Minodronate in Mouse Femora Through Isotope Microscopy

Minodronate is highlighted for its marked and sustained effects on osteoporotic bones. To determine the duration of minodronate's effects, we have assessed the localization of the drug in mouse bones through isotope microscopy, after labeling it with a stable nitrogen isotope ([(15)N]-minodronate). In addition, minodronate-treated bones were assessed by histochemistry and transmission electron microscopy (TEM). Eight-week-old male ICR mice received [(15)N]-minodronate (1 mg/kg) intravenously and were sacrificed after 3 hr, 24 hr, 1 week, and 1 month. Isotope microscopy showed that [(15)N]-minodronate was present mainly beneath osteoblasts rather than nearby osteoclasts. At 3 hr after minodronate administration, histochemistry and TEM showed osteoclasts with well-developed ruffled borders. However, osteoclasts were roughly attached to the bone surfaces and did not feature ruffled borders at 24 hr after minodronate administration. The numbers of tartrate-resistant acid phosphatase-positive osteoclasts and alkaline phosphatase-reactive osteoblastic area were not reduced suddenly, and apoptotic osteoclasts appeared in 1 week and 1 month after the injections. Von Kossa staining demonstrated that osteoclasts treated with minodronate did not incorporate mineralized bone matrix. Taken together, minodronate accumulates in bone underneath osteoblasts rather than under bone-resorbing osteoclasts; therefore, it is likely that the minodronate-coated bone matrix is resistant to osteoclastic resorption, which results in a long-lasting and bone-preserving effect.