The effects of bone morphogenetic protein 2 and thrombopoietin treatment on angiogenic properties of endothelial cells derived from the lung and bone marrow of young and aged, male and female mice

With an aging world population, there is an increased risk of fracture and impaired healing. One contributing factor may be aging-associated decreases in vascular function; thus, enhancing angiogenesis could improve fracture healing. Both bone morphogenetic protein 2 (BMP-2) and thrombopoietin (TPO) have pro-angiogenic effects. The aim of this study was to investigate the effects of treatment with BMP-2 or TPO on the in vitro angiogenic and proliferative potential of endothelial cells (ECs) isolated from lungs (LECs) or bone marrow (BMECs) of young (3-4 months) and old (22-24 months), male and female, C57BL/6J mice. Cell proliferation, vessel-like structure formation, migration, and gene expression were used to evaluate angiogenic properties. In vitro characterization of ECs generally showed impaired vessel-like structure formation and proliferation in old ECs compared to young ECs, but improved migration characteristics in old BMECs. Differential sex-based angiogenic responses were observed, especially with respect to drug treatments and gene expression. Importantly, these studies suggest that NTN1, ROBO2, and SLIT3, along with angiogenic markers (CD31, FLT-1, ANGPT1, and ANGP2) differentially regulate EC proliferation and functional outcomes based on treatment, sex, and age. Furthermore, treatment of old ECs with TPO typically improved vessel-like structure parameters, but impaired migration. Thus, TPO may serve as an alternative treatment to BMP-2 for fracture healing in aging owing to improved angiogenesis and fracture healing, and the lack of side effects associated with BMP-2.

Neonatal Osteomacs and Bone Marrow Macrophages Differ in Phenotypic Marker Expression and Function

Osteomacs (OM) are specialized bone-resident macrophages that are a component of the hematopoietic niche and support bone formation. Also located in the niche are a second subset of macrophages, namely bone marrow-derived macrophages (BM Mφ). We previously reported that a subpopulation of OM co-express both CD166 and CSF1R, the receptor for macrophage colony-stimulating factor (MCSF), and that OM form more bone-resorbing osteoclasts than BM Mφ. Reported here are single-cell quantitative RT-PCR (qRT-PCR), mass cytometry (CyTOF), and marker-specific functional studies that further identify differences between OM and BM Mφ from neonatal C57Bl/6 mice. Although OM express higher levels of CSF1R and MCSF, they do not respond to MCSF-induced proliferation, in contrast to BM Mφ. Moreover, receptor activator of NF-κB ligand (RANKL), without the addition of MCSF, was sufficient to induce osteoclast formation in OM but not BM Mφ cultures. OM express higher levels of CD166 than BM Mφ, and we found that osteoclast formation by CD166^-/- OM was reduced compared with wild-type (WT) OM, whereas CD166^-/- BM Mφ showed enhanced osteoclast formation. CD110/c-Mpl, the receptor for thrombopoietin (TPO), was also higher in OM, but TPO did not alter OM-derived osteoclast formation, whereas TPO stimulated BM Mφ osteoclast formation. CyTOF analyses demonstrated OM uniquely co-express CD86 and CD206, markers of M1 and M2 polarized macrophages, respectively. OM performed equivalent phagocytosis in response to LPS or IL-4/IL-10, which induce polarization to M1 and M2 subtypes, respectively, whereas BM Mφ were less competent at phagocytosis when polarized to the M2 subtype. Moreover, in contrast to BM Mφ, LPS treatment of OM led to the upregulation of CD80, an M1 marker, as well as IL-10 and IL-6, known anti-inflammatory cytokines. Overall, these data reveal that OM and BM Mφ are distinct subgroups of macrophages, whose phenotypic and functional differences in proliferation, phagocytosis, and osteoclast formation may contribute physiological specificity during health and disease. © 2021 American Society for Bone and Mineral Research (ASBMR).

Megakaryocytes promote osteoclastogenesis in aging

Megakaryocytes (MKs) support bone formation by stimulating osteoblasts (OBs) and inhibiting osteoclasts (OCs). Aging results in higher bone resorption, leading to bone loss. Whereas previous studies showed the effects of aging on MK-mediated bone formation, the effects of aging on MK-mediated OC formation is poorly understood. Here we examined the effect of thrombopoietin (TPO) and MK-derived conditioned media (CM) from young (3-4 months) and aged (22-25 months) mice on OC precursors. Our findings showed that aging significantly increased OC formation in vitro. Moreover, the expression of the TPO receptor, Mpl, and circulating TPO levels were elevated in the bone marrow cavity. We previously showed that MKs from young mice secrete factors that inhibit OC differentiation. However, rather than inhibiting OC development, we found that MKs from aged mice promote OC formation. Interestingly, these age-related changes in MK functionality were only observed using female MKs, potentially implicating the sex steroid, estrogen, in signaling. Further, RANKL expression was highly elevated in aged MKs suggesting MK-derived RANKL signaling may promote osteoclastogenesis in aging. Taken together, these data suggest that modulation in TPO-Mpl expression in bone marrow and age-related changes in the MK secretome promote osteoclastogenesis to impact skeletal aging.

Gene discovery from Jatropha curcas by sequencing of ESTs from normalized and full-length enriched cDNA library from developing seeds

BACKGROUND

Jatropha curcas L. is promoted as an important non-edible biodiesel crop worldwide. Jatropha oil, which is a triacylglycerol, can be directly blended with petro-diesel or transesterified with methanol and used as biodiesel. Genetic improvement in jatropha is needed to increase the seed yield, oil content, drought and pest resistance, and to modify oil composition so that it becomes a technically and economically preferred source for biodiesel production. However, genetic improvement efforts in jatropha could not take advantage of genetic engineering methods due to lack of cloned genes from this species. To overcome this hurdle, the current gene discovery project was initiated with an objective of isolating as many functional genes as possible from J. curcas by large scale sequencing of expressed sequence tags (ESTs).

RESULTS

A normalized and full-length enriched cDNA library was constructed from developing seeds of J. curcas. The cDNA library contained about 1 × 10(6) clones and average insert size of the clones was 2.1 kb. Totally 12,084 ESTs were sequenced to average high quality read length of 576 bp. Contig analysis revealed 2258 contigs and 4751 singletons. Contig size ranged from 2-23 and there were 7333 ESTs in the contigs. This resulted in 7009 unigenes which were annotated by BLASTX. It showed 3982 unigenes with significant similarity to known genes and 2836 unigenes with significant similarity to genes of unknown, hypothetical and putative proteins. The remaining 191 unigenes which did not show similarity with any genes in the public database may encode for unique genes. Functional classification revealed unigenes related to broad range of cellular, molecular and biological functions. Among the 7009 unigenes, 6233 unigenes were identified to be potential full-length genes.

CONCLUSIONS

The high quality normalized cDNA library was constructed from developing seeds of J. curcas for the first time and 7009 unigenes coding for diverse biological functions including oil biosynthesis were identified. These genes will serve as invaluable genetic resource for crop improvement in jatropha to make it an ideal and profitable crop for biodiesel production.