Enhancing Human Treg Cell Induction through Engineered Dendritic Cells and Zinc Supplementation

Regulatory T (Treg) cells hold promise for the ultimate cure of immune-mediated diseases. However, how to effectively restore Treg function in patients remains unknown. Previous reports suggest that activated dendritic cells (DCs) de novo synthesize locally high concentrations of 1,25-dihydroxy vitamin D, i.e., the active vitamin D or 1,25(OH)2D by upregulating the expression of 25-hydroxy vitamin D 1α-hydroxylase. Although 1,25(OH)2D has been shown to induce Treg cells, DC-derived 1,25(OH)2D only serves as a checkpoint to ensure well-balanced immune responses. Our animal studies have shown that 1,25(OH)2D requires high concentrations to generate Treg cells, which can cause severe side effects. In addition, our animal studies have also demonstrated that dendritic cells (DCs) overexpressing the 1α-hydroxylase de novo synthesize the effective Treg-inducing 1,25(OH)2D concentrations without causing the primary side effect of hypercalcemia (i.e., high blood calcium levels). This study furthers our previous animal studies and explores the efficacy of the la-hydroxylase-overexpressing DCs in inducing human CD4+FOXP3+regulatory T (Treg) cells. We discovered that the effective Treg-inducing doses of 1,25(OH)2D were within a range. Additionally, our data corroborated that the 1α-hydroxylase-overexpressing DCs synthesized 1,25(OH)2D within this concentration range in vivo, thus facilitating effective Treg cell induction. Moreover, this study demonstrated that 1α-hydroxylase expression levels were pivotal for DCs to induce Treg cells because physiological 25(OH)D levels were sufficient for the engineered but not parental DCs to enhance Treg cell induction. Interestingly, adding non-toxic zinc concentrations significantly augmented the Treg-inducing capacity of the engineered DCs. Our new findings offer a novel therapeutic avenue for immune-mediated human diseases, such as inflammatory bowel disease, type 1 diabetes, and multiple sclerosis, by integrating zinc with the 1α-hydroxylase-overexpressing DCs.

Transient TKI-resistant CD44+pBAD+ blasts undergo intrinsic homeostatic adaptation to promote the survival of acute myeloid leukemia in vitro

Acute myeloid leukemia (AML) patients have frequent mutations in FMS-like receptor tyrosine kinase 3 (FLT3-mut AML), who respond poorly to salvage chemotherapies and targeted therapies such as tyrosine kinase inhibitors (TKIs). Disease relapse is a common reason of treatment failures in FLT3-mut AML patients, but its intracellular refractory mechanism remains to be discovered. In this study, we designed serial in vitro time-course studies to investigate the biomarkers of TKI-resistant blasts and their survival mechanism. First, we found that a group of transient TKI-resistant blasts were CD44+Phosphorylated-BAD (pBAD)+ and that they could initiate the regrowth of blast clusters in vitro. Notably, TKI-treatments upregulated the compensation pathways to promote PIM2/3-mediated phosphorylation of BAD to initiate the blast survival. Next, we discovered a novel process of intracellular adaptive responses in these transient TKI-resistant blasts, including upregulated JAK/STAT signaling pathways for PIM2/3 expressions and activated SOCS1/SOCS3/PIAS2 inhibitory pathways to down-regulate redundant signal transduction and kinase phosphorylation to regain intracellular homeostasis. Finally, we found that the combination of TKIs with TYK2/STAT4 pathways-driven inhibitors could effectively treat FLT3-mut AML in vitro. In summary, our findings reveal that TKI-treatment can activate a JAK/STAT-PIM2/3 axis-mediated signaling pathways to promote the survival of CD44+pBAD+blasts in vitro. Disrupting these TKIs-activated redundant pathways and blast homeostasis could be a novel therapeutic strategy to treat FLT3-mut AML and prevent disease relapse in vivo.

The potential role of the thymus in immunotherapies for acute myeloid leukemia

Understanding the factors which shape T-lymphocyte immunity is critical for the development and application of future immunotherapeutic strategies in treating hematological malignancies. The thymus, a specialized central lymphoid organ, plays important roles in generating a diverse T lymphocyte repertoire during the infantile and juvenile stages of humans. However, age-associated thymic involution and diseases or treatment associated injury result in a decline in its continuous role in the maintenance of T cell-mediated anti-tumor/virus immunity. Acute myeloid leukemia (AML) is an aggressive hematologic malignancy that mainly affects older adults, and the disease's progression is known to consist of an impaired immune surveillance including a reduction in naïve T cell output, a restriction in T cell receptor repertoire, and an increase in frequencies of regulatory T cells. As one of the most successful immunotherapies thus far developed for malignancy, T-cell-based adoptive cell therapies could be essential for the development of a durable effective treatment to eliminate residue leukemic cells (blasts) and prevent AML relapse. Thus, a detailed cellular and molecular landscape of how the adult thymus functions within the context of the AML microenvironment will provide new insights into both the immune-related pathogenesis and the regeneration of a functional immune system against leukemia in AML patients. Herein, we review the available evidence supporting the potential correlation between thymic dysfunction and T-lymphocyte impairment with the ontogeny of AML (II-VI). We then discuss how the thymus could impact current and future therapeutic approaches in AML (VII). Finally, we review various strategies to rejuvenate thymic function to improve the precision and efficacy of cancer immunotherapy (VIII).

Defective bone repletion in aged Balb/cBy mice was caused by impaired osteoblastic differentiation

INTRODUCTION

This study was undertaken to gain mechanistic information about bone repair using the bone repletion model in aged Balb/cBy mice.

MATERIALS AND METHODS

one month-old (young) mice were fed a calcium-deficient diet for 2 weeks and 8 month-old (adult) and 21-25 month-old (aged) female mice for 4 weeks during depletion, which was followed by feeding a calcium-sufficient diet for 16 days during repletion. To determine if prolonged repletion would improve bone repair, an additional group of aged mice were repleted for 4 additional weeks. Control mice were fed calcium-sufficient diet throughout. In vivo bone repletion response was assessed by bone mineral density gain and histomorphometry. In vitro response was monitored by osteoblastic proliferation, differentiation, and senescence.

RESULTS

 There was no significant bone repletion in aged mice even with an extended repletion period, indicating an impaired bone repletion. This was not due to an increase in bone cell senescence or reduction in osteoblast proliferation, but to dysfunctional osteoblastic differentiation in aged bone cells. Osteoblasts of aged mice had elevated levels of cytosolic and ER calcium, which were associated with increased Cav1.2 and CaSR (extracellular calcium channels) expression but reduced expression of Orai1 and Stim1, key components of Stored Operated Ca2+ Entry (SOCE). Activation of Cav1.2 and CaSR leads to increased osteoblastic proliferation, but activation of SOCE is associated with osteoblastic differentiation.

CONCLUSION

The bone repletion mechanism in aged Balb/cBy mice is defective that is caused by an impaired osteoblast differentiation through reducedactivation of SOCE.

FBP1-Altered Carbohydrate Metabolism Reduces Leukemic Viability through Activating P53 and Modulating the Mitochondrial Quality Control System In Vitro

Acute myeloid leukemia (AML)—the most frequent form of adult blood cancer—is characterized by heterogeneous mechanisms and disease progression. Developing an effective therapeutic strategy that targets metabolic homeostasis and energy production in immature leukemic cells (blasts) is essential for overcoming relapse and improving the prognosis of AML patients with different subtypes. With respect to metabolic regulation, fructose-1,6-bisphosphatase 1 (FBP1) is a gluconeogenic enzyme that is vital to carbohydrate metabolism, since gluconeogenesis is the central pathway for the production of important metabolites and energy necessary to maintain normal cellular activities. Beyond its catalytic activity, FBP1 inhibits aerobic glycolysis—known as the “Warburg effect”—in cancer cells. Importantly, while downregulation of FBP1 is associated with carcinogenesis in major human organs, restoration of FBP1 in cancer cells promotes apoptosis and prevents disease progression in solid tumors. Recently, our large-scale sequencing analyses revealed FBP1 as a novel inducible therapeutic target among 17,757 vitamin-D-responsive genes in MV4-11 or MOLM-14 blasts in vitro, both of which were derived from AML patients with FLT3 mutations. To investigate FBP1′s anti-leukemic function in this study, we generated a new AML cell line through lentiviral overexpression of an FBP1 transgene in vitro (named FBP1-MV4-11). Results showed that FBP1-MV4-11 blasts are more prone to apoptosis than MV4-11 blasts. Mechanistically, FBP1-MV4-11 blasts have significantly increased gene and protein expression of P53, as confirmed by the P53 promoter assay in vitro. However, enhanced cell death and reduced proliferation of FBP1-MV4-11 blasts could be reversed by supplementation with post-glycolytic metabolites in vitro. Additionally, FBP1-MV4-11 blasts were found to have impaired mitochondrial homeostasis through reduced cytochrome c oxidase subunit 2 (COX2 or MT-CO2) and upregulated PTEN-induced kinase (PINK1) expressions. In summary, this is the first in vitro evidence that FBP1-altered carbohydrate metabolism and FBP1-activated P53 can initiate leukemic death by activating mitochondrial reprogramming in AML blasts, supporting the clinical potential of FBP1-based therapies for AML-like cancers.

Combination therapy of insulin-like growth factor I and BTP-2 markedly improves lipopolysaccharide-induced liver injury in mice

Acute liver injury is a common disease without effective therapy in humans. We sought to evaluate a combination therapy of insulin-like growth factor 1 (IGF-I) and BTP-2 in a mouse liver injury model induced by lipopolysaccharide (LPS). We chose this model because LPS is known to increase the expression of the transcription factors related to systemic inflammation (i.e., NFκB, CREB, AP1, IRF 3, and NFAT), which depends on calcium signaling. Notably, these transcription factors all have pleiotropic effects and account for the other observed changes in tissue damage parameters. Additionally, LPS is also known to increase the genes associated with a tissue injury (e.g., NGAL, SOD, caspase 3, and type 1 collagen) and systemic expression of pro-inflammatory cytokines. Finally, LPS compromises vascular integrity. Accordingly, IGF-I was selected because its serum levels were shown to decrease during systemic inflammation. BTP-2 was chosen because it was known to decrease cytosolic calcium, which is increased by LPS. This current study showed that IGF-I, BTP-2, or a combination therapy significantly altered and normalized all of the aforementioned LPS-induced gene changes. Additionally, our therapies reduced the vascular leakage caused by LPS, as evidenced by the Evans blue dye technique. Furthermore, histopathologic studies showed that IGF-I decreased the proportion of hepatocytes with ballooning degeneration. Finally, IGF-I also increased the expression of the hepatic growth factor (HGF) and the receptor for the epidermal growth factor (EGFR), markers of liver regeneration. Collectively, our data suggest that a combination of IGF-I and BTP-2 is a promising therapy for acute liver injury.

Targeting TKI-Activated NFKB2-MIF/CXCLs-CXCR2 Signaling Pathways in FLT3 Mutated Acute Myeloid Leukemia Reduced Blast Viability

Disease relapse is a common cause of treatment failure in FMS-like tyrosine kinase 3 (FLT3) mutated acute myeloid leukemia (AML). In this study, to identify therapeutic targets responsible for the survival and proliferation of leukemic cells (blasts) with FLT3 mutations after gilteritinib (GILT, a 2nd generation tyrosine kinase inhibitor (TKI)) treatment, we performed proteomic screening of cytokine release and in vitro/ex vivo studies to investigate their associated signaling pathways and transcriptional regulation. Here, we report that macrophage migration inhibition factor (MIF) was significantly increased in the supernatant of GILT-treated blasts when compared to untreated controls. Additionally, the GILT-treated blasts that survived were found to exhibit higher expressions of the CXCR2 gene and protein, a common receptor for MIF and pro-inflammatory cytokines. The supplementation of exogenous MIF to GILT-treated blasts revealed a group of CD44High+ cells that might be responsible for the relapse. Furthermore, we identified the highly activated non-classical NFKB2 pathway after GILT-treatment. The siRNA transient knockdown of NFKB2 significantly reduced the gene expressions of MIF, CXCR2, and CXCL5. Finally, treatments of AML patient samples ex vivo demonstrated that the combination of a pharmaceutical inhibitor of the NFKB family and GILT can effectively suppress primary blasts’ secretion of tumor-promoting cytokines, such as CXCL1/5/8. In summary, we provide the first evidence that targeting treatment-activated compensatory pathways, such as the NFKB2-MIF/CXCLs-CXCR2 axis could be a novel therapeutic strategy to overcome TKI-resistance and effectively treat AML patients with FLT3 mutations.

Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation

A major cause of osteoporosis is impaired coupled bone formation. Mechanistically, both osteoclast-derived and bone-derived growth factors have been previously implicated. We hypothesize that the release of bone calcium during osteoclastic bone resorption is essential for coupled bone formation. Osteoclastic resorption increases interstitial fluid calcium locally from the normal 1.8 mM up to 5 mM. MC3T3-E1 osteoprogenitors, cultured in a 3.6 mM calcium medium, demonstrated that calcium signaling stimulated osteogenic cell proliferation, differentiation, and migration. Calcium channel knockdown studies implicated calcium channels, Cav1.2, store-operated calcium entry (SOCE), and calcium-sensing receptor (CaSR) in regulating bone cell anabolic activities. MC3T3-E1 cultured in a 3.6 mM calcium medium expressed increased gene expression of Wnt signaling and growth factors platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and bone morphogenic protein-2 (BMP 2). Our coupling model of bone formation, the Receptor activator of nuclear factor-kappa-Β ligand (RANKL) treated mouse calvaria, confirmed the role of calcium signaling in coupled bone formation by exhibiting increased gene expression for osterix and osteocalcin. Critically, dual immunocytochemistry showed that RANKL treatment increased osterix positive cells and increased fluorescence intensity of Cav1.2 and CaSR protein expression per osterix positive cell. The data established that calcium released by osteoclasts contributed to the regulation of coupled bone formation. CRISPR/Cas-9 knockout of Cav1.2 in osteoprogenitors cultured in basal calcium medium caused a >80% decrease in the expression of downstream osteogenic genes, emphasizing the large magnitude of the effect of calcium signaling. Thus, calcium signaling is a major regulator of coupled bone formation.

Vitamin D activates FBP1 to block the Warburg effect and modulate blast metabolism in acute myeloid leukemia

Acute myeloid leukemia (AML) has the lowest survival rate among the leukemias. Targeting intracellular metabolism and energy production in leukemic cells can be a promising therapeutic strategy for AML. Recently, we presented the successful use of vitamin D (1,25VD3) gene therapy to treat AML mouse models in vivo. In this study, recognizing the importance of 1,25VD3 as one of only 2 molecules (along with glucose) photosynthesized for energy during the beginning stage of life on this planet, we explored the functional role of 1,25VD3 in AML metabolism.

Transcriptome database (RNA-seq) of four different AML cell lines revealed 17,757 genes responding to 1,25VD3-treatment. Moreover, we discovered that fructose-bisphosphatase 1 (FBP1) noticeably stands out as the only gene (out of 17,757 genes) with a 250-fold increase in gene expression, which is known to encode the key rate-limiting gluconeogenic enzyme fructose-1,6-bisphosphatase. The significant increased expression of FBP1 gene and proteins induced by 1,25VD3 was confirmed by qPCR, western blot, flow cytometry, immunocytochemistry and functional lactate assay. Additionally, 1,25VD3 was found to regulate different AML metabolic processes including gluconeogenesis, glycolysis, TCA, de novo nucleotide synthesis, etc. In summary, we provided the first evidence that 1,25 VD3-induced FBP1 overexpression might be a novel therapeutic target to block the “Warburg Effect” to reduce energy production in AML blasts.

The Effects of Insulin-Like Growth Factor I and BTP-2 on Acute Lung Injury

Acute lung injury (ALI) afflicts approximately 200,000 patients annually and has a 40% mortality rate. The COVID-19 pandemic has massively increased the rate of ALI incidence. The pathogenesis of ALI involves tissue damage from invading microbes and, in severe cases, the overexpression of inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). This study aimed to develop a therapy to normalize the excess production of inflammatory cytokines and promote tissue repair in the lipopolysaccharide (LPS)-induced ALI. Based on our previous studies, we tested the insulin-like growth factor I (IGF-I) and BTP-2 therapies. IGF-I was selected, because we and others have shown that elevated inflammatory cytokines suppress the expression of growth hormone receptors in the liver, leading to a decrease in the circulating IGF-I. IGF-I is a growth factor that increases vascular protection, enhances tissue repair, and decreases pro-inflammatory cytokines. It is also required to produce anti-inflammatory 1,25-dihydroxyvitamin D. BTP-2, an inhibitor of cytosolic calcium, was used to suppress the LPS-induced increase in cytosolic calcium, which otherwise leads to an increase in proinflammatory cytokines. We showed that LPS increased the expression of the primary inflammatory mediators such as toll like receptor-4 (TLR-4), IL-1β, interleukin-17 (IL-17), TNF-α, and interferon-γ (IFN-γ), which were normalized by the IGF-I + BTP-2 dual therapy in the lungs, along with improved vascular gene expression markers. The histologic lung injury score was markedly elevated by LPS and reduced to normal by the combination therapy. In conclusion, the LPS-induced increases in inflammatory cytokines, vascular injuries, and lung injuries were all improved by IGF-I + BTP-2 combination therapy.

The importance of vitamin d metabolism as a potential prophylactic, immunoregulatory and neuroprotective treatment for COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has led to a declaration of a Public Health Emergency of International Concern by the World Health Organization. As of May 18, 2020, there have been more than 4.7 million cases and over 316,000 deaths worldwide. COVID-19 is caused by a highly infectious novel coronavirus known as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), leading to an acute infectious disease with mild-to-severe clinical symptoms such as flu-like symptoms, fever, headache, dry cough, muscle pain, loss of smell and taste, increased shortness of breath, bilateral viral pneumonia, conjunctivitis, acute respiratory distress syndromes, respiratory failure, cytokine release syndrome (CRS), sepsis, etc. While physicians and scientists have yet to discover a treatment, it is imperative that we urgently address 2 questions: how to prevent infection in immunologically naive individuals and how to treat severe symptoms such as CRS, acute respiratory failure, and the loss of somatosensation. Previous studies from the 1918 influenza pandemic have suggested vitamin D's non-classical role in reducing lethal pneumonia and case fatality rates. Recent clinical trials also reported that vitamin D supplementation can reduce incidence of acute respiratory infection and the severity of respiratory tract diseases in adults and children. According to our literature search, there are no similar findings of clinical trials that have been published as of July 1st, 2020, in relation to the supplementation of vitamin D in the potential prevention and treatment for COVID-19. In this review, we summarize the potential role of vitamin D extra-renal metabolism in the prevention and treatment of the SARS-CoV-2 infection, helping to bring us slightly closer to fulfilling that goal. We will focus on 3 major topics here: 1. Vitamin D might aid in preventing SARS-CoV-2 infection: Vitamin D: Overview of Renal and Extra-renal metabolism and regulation. Vitamin D: Overview of molecular mechanism and multifaceted functions beyond skeletal homeostasis. Vitamin D: Overview of local immunomodulation in human infectious diseases. Anti-viral infection. Anti-malaria and anti-systemic lupus erythematosus (SLE). 2. Vitamin D might act as a strong immunosuppressant inhibiting cytokine release syndrome in COVID-19: Vitamin D: Suppression of key pro-inflammatory pathways including nuclear factor kappa B (NF-kB), interleukin-6 (IL-6), and tumor necrosis factor (TNF). 3. Vitamin D might prevent loss of neural sensation in COVID-19 by stimulating expression of neurotrophins like Nerve Growth Factor (NGF): Vitamin D: Induction of key neurotrophic factors. .

Discovery of proangiogenic CD44+mesenchymal cancer stem cells in an acute myeloid leukemia patient's bone marrow

Here, we report a unique acute myeloid leukemia (AML) bone marrow-derived mesenchymal stem cell (MSC) with both mesenchymal and endothelial potential, which we have named Mesenchymal Cancer Stem Cells (MCSCs). These MCSCs are CD90-CD13-CD44+ and differ from MSCs in isolation, expansion, differentiation, immunophenotype, and cytokine release profile. Furthermore, blocking CD44 inhibited the proliferation and cluster formation of early MCSCs with lower ICAM-1 protein levels. Similar CD90-CD44+ cancer stem cells have been reported in both gastric and breast cancers, which grew in floating spheres in vitro and exhibited mesenchymal features and high metastatic/tumorigenic capabilities in vivo. Our novel discovery provides the first evidence that certain AMLs may be comprised of both hematopoietic and stromal malignant cells. Targeting MCSCs and their cytokine release has potential as a novel therapeutic approach in AML.

Unique anabolic action of stem cell gene therapy overexpressing PDGFB-DSS6 fusion protein in OVX osteoporosis mouse model

In the present study we sought to improve the efficacy and safety of our Sca1+ PDGFB stem cell gene therapy for osteoporosis in ovariectomized (OVX) mouse model. This therapy is administered by marrow transplantation. We established the promise of this approach by previously showing that this therapy in normal mice increase bone density, increased endosteal cortical and trabecular bone formation, caused de novo trabecular bone formation, increased cortical thickness and improve bone strength. In the current study we produced a fusion gene, PDGFB-DSS6. We reasoned that the DSS6, calcium binding protein would trap the PDGFB at the bone surface and thereby limit the amount of PDGFB required to produce an optimal bone formation response, i.e. efficacy with a lower engraftment. The result shows that indeed with a very low level of engraftment we achieved a large increase in bone formation in the OVX model of bone loss. Serum analysis for biochemical marker of new bone formation showed an approximate 75% increase in alkaline phosphatase levels in Sca1+PDGFB-DSS6 group as compared to other groups. Quantitative analysis of bone by microCT showed a massive increase in trabecular bone density and trabecular connectivity of the femur in the metaphysis in Sca1+ PDGFB-DSS6 group. The increased cortical porosity produced by OVX was replaced by the Sca1+ PDGFB-DSS6 therapy but not by the positive control Sca1+ PDGFB. Additionally, an increase in the femur bone strength was also observed specifically in Sca1+ PDGFB-DSS6 as compared to other treatment groups, emphasizing the functional significance of the observed anabolic action is on bone formation. In future work we will focus on nontoxic preconditioning of our marrow transplantation procedure and also on transcriptional control of therapeutic gene expression to avoid excess bone formation.

Augmentation of the Conversion of 25-hydroxyvitamin D into 1,25-Dihydroxyvitamin D Specifically in Inflamed Intestines for the Treatment of Inflammatory Bowel Disease

An important pathogenic mechanism of inflammatory bowel disease (IBD) is the penetration of intestinal epithelium barrier by luminal microbes, which does not have a clinical solution. In this respect, previous data have shown that Lgr5+ intestinal stem cells (ISCs) can differentiate into all intestinal epithelial cells and that 1,25(OH)2D, i.e. the active vitamin D metabolite, is essential for the development of Lgr5+ ISCs. However, supplementation of native vitamin D, though effectively raising blood 25(OH)D levels, did not reach the expected outcomes in IBD patients. The data suggest that the conversion of 25(OH)D into 1,25(OH)2D cannot meet the demand in intestines. In addition, our recent findings support that direct systemic delivery of the requied 1,25(OH)2D levels to circumvent the insufficient conversion is impossible because of attending hyercalcemia. Here, we propose to augment such conversion specifically in inflamed intestines using engineered macrophages (MAC-CYP cells) that specifically home into inflamed intestines and overexpress 1alpha-hydroxylase (i.e. the physiological enzyme that converts 25[OH]D into 1,25[OH]2D). We showed that intraperitoneally administered MAC-CYP cells homed specifically into inflamed intestines, significantly suppressed ongoing experimental colitis without causing hypercalcemia, and augmented the migration of Lgr5+ ISCs which differentiated into mature intestinal epithelial cells under physiological and colitis conditions. In vitro, we showed that 1,25(OH)2D enhanced the survival of multipotent Lgr5+ ISCs. In conclusion, our data suggest that specific augmentation of 1alpha-hydroxylase activity in inflamed intestines is a promising therapeutic strategy for IBD.

In Vivo Augmentation of Gut-Homing Regulatory T Cell Induction

Inflammatory bowel disease (IBD) is an inflammatory chronic disease in the gastrointestinal tract (GUT). In the United States, there are approximately 1.4 million IBD patients. It is generally accepted that a dysregulated immune response to gut bacteria initiates the disease and disrupts the mucosal epithelial barrier. We recently show that gut-homing regulatory T (Treg) cells are a promising therapy for IBD. Accordingly, this article presents a protocol for in vivo augmentation of gut-homing Treg cell induction. In this protocol, dendritic cells are engineered to produce locally high concentrations of two molecules de novo, active vitamin D (1,25-dihydroxyvitamin D or 1,25[OH]2D) and active vitamin A (retinoic acid or RA). We chose 1,25(OH)2D and RA based on previous findings showing that 1,25(OH)2D can induce the expression of regulatory molecules (e.g., forkhead box P3 and interleukin-10) and that RA can stimulate the expression of gut-homing receptors in T cells. To generate such engineered dendritic cells, we use a lentiviral vector to transduce dendritic cells to overexpress two genes. One gene is the cytochrome P450 family 27 subfamily B member 1 that encodes 25-hydroxyvitamin D 1α-hydroxylase, which physiologically catalyzes the synthesis of 1,25(OH)2D. The other gene is the aldehyde dehydrogenase 1 family member A2 that encodes retinaldehyde dehydrogenase 2, which physiologically catalyzes the synthesis of RA. This protocol can be used for future investigation of gut-homing Treg cells in vivo.

Mechanistic study of the cause of decreased blood 1,25-Dihydroxyvitamin D in sepsis

Background

Vitamin D deficiency, determined by blood levels of 25-hydroxyvitamin D [25(OH) D, i.e. the major vitamin D form in blood], has been shown to associate with all-cause mortalities. We recently demonstrated that blood levels of 1,25-dihydroxyvitamin D [1,25(OH)₂D, i.e. the active vitamin D] were significantly lower in non-survivors compared to survivors among sepsis patients. Unexpectedly, despite the well documented roles of 1,25(OH)₂D in multiple biological functions such as regulation of immune responses, stimulation of antimicrobials, and maintenance of barrier function, 1,25(OH)₂D supplementation failed to improve disease outcomes. These previous findings suggest that, in addition to 1,25(OH)₂D deficiency, disorders leading to the 1,25(OH)₂D deficiency also contribute to mortality among sepsis patients. Therefore, this study investigated the mechanisms leading to sepsis-associated 1,25(OH)₂D deficiency.

Methods

We studied mechanisms known to regulate kidney 25-hydroxylvitamin D 1α-hydroxylase which physiologically catalyzes the conversion of 25(OH) D into 1,25(OH)₂D. Such mechanisms included parathyroid hormone (PTH), insulin-like growth factor 1 (IGF-1), fibroblast growth factor 23 (FGF-23), and kidney function.

Results

We demonstrated in both human subjects and mice that sepsis-associated 1,25(OH)₂D deficiency could not be overcome by increased production of PTH which stimulates 1α-hydroxylase. Further studies showed that this failure of PTH to maintain blood 1,25(OH)₂D levels was associated with decreased blood levels of IGF-1, increased blood levels of FGF-23, and kidney failure. Since the increase in blood levels of FGF-23 is known to associate with kidney failure, we further investigated the mechanisms leading to sepsis-induced decrease in blood levels of IGF-1. Our data showed that blood levels of growth hormone, which stimulates IGF-1 production in liver, were increased but could not overcome the IGF-1 deficiency. Additionally, we found that the inability of growth hormone to restore the IGF-1 deficiency was associated with suppressed expression and signaling of growth hormone receptor in liver.

Conclusions

Because FGF-23 and IGF-1 have multiple biological functions besides their role in regulating kidney 1α-hydroxylase, our data suggest that FGF-23 and IGF-1 are warranted for further investigation as potential agents for the correction of 1,25(OH)₂D deficiency and for the improvement of survival among sepsis patients.

Cyclooxygenase 2 augments osteoblastic but suppresses chondrocytic differentiation of CD90+ skeletal stem cells in fracture sites

Cyclooxygenase 2 (COX-2) is essential for normal tissue repair. Although COX-2 is known to enhance the differentiation of mesenchymal stem cells (MSCs), how COX-2 regulates MSC differentiation into different tissue-specific progenitors to promote tissue repair remains unknown. Because it has been shown that COX-2 is critical for normal bone repair and local COX-2 overexpression in fracture sites accelerates fracture repair, this study aimed to determine the MSC subsets that are targeted by COX-2. We showed that CD90⁺ mouse skeletal stem cells (mSSCs; i.e., CD45^-Tie2^-AlphaV⁺ MSCs) were selectively recruited by macrophage/monocyte chemoattractant protein 1 into fracture sites following local COX-2 overexpression. In addition, local COX-2 overexpression augmented osteoblast differentiation and suppressed chondrocyte differentiation in CD90⁺ mSSCs, which depended on canonical WNT signaling. CD90 depletion data demonstrated that local COX-2 overexpression targeted CD90⁺ mSSCs to accelerate fracture repair. In conclusion, CD90⁺ mSSCs are promising targets for the acceleration of bone repair.

In Vivo Generation of Gut-Homing Regulatory T Cells for the Suppression of Colitis

Current therapies for gut inflammation have not reached the desired specificity and are attended by unintended immune suppression. This study aimed to provide evidence for supporting a hypothesis that direct in vivo augmentation of the induction of gut-homing regulatory T (Treg) cells is a strategy of expected specificity for the treatment of chronic intestinal inflammation (e.g., inflammatory bowel disease). We showed that dendritic cells (DCs), engineered to de novo produce high concentrations of both 1,25-dihydroxyvitamin D, the active vitamin D metabolite, and retinoic acid, an active vitamin A metabolite, augmented the induction of T cells that express both the regulatory molecule Foxp3 and the gut-homing receptor CCR9 in vitro and in vivo. In vivo, the newly generated Ag-specific Foxp3⁺ T cells homed to intestines. Additionally, transfer of such engineered DCs robustly suppressed ongoing experimental colitis. Moreover, CD4⁺ T cells from spleens of the mice transferred with the engineered DCs suppressed experimental colitis in syngeneic hosts. The data suggest that the engineered DCs enhance regulatory function in CD4⁺ T cell population in peripheral lymphoid tissues. Finally, we showed that colitis suppression following in vivo transfer of the engineered DCs was significantly reduced when Foxp3⁺ Treg cells were depleted. The data indicate that maximal colitis suppression mediated by the engineered DCs requires Treg cells. Collectively, our data support that DCs de novo overproducing both 1,25-dihydroxyvitamin D and retinoic acid are a promising novel therapy for chronic intestinal inflammation.

1,25-Dihydroxyvitamin D suppresses M1 macrophages and promotes M2 differentiation at bone injury sites

An indispensable role of macrophages in bone repair has been well recognized. Previous data have demonstrated the copresence of M1 macrophages and mesenchymal stem cells (MSCs) during the proinflammatory stage of bone repair. However, the exact role of M1 macrophages in MSC function and bone repair is unknown. This study aimed to define the role of M1 macrophages at bone injury sites via the function of 1,25-Dihydroxyvitamin D (1,25[OH]2D) in suppressing M1 but promoting M2 differentiation. We showed that 1,25(OH)2D suppressed M1 macrophage-mediated enhancement of MSC migration. Additionally, 1,25(OH)2D inhibited M1 macrophage secretion of osteogenic proteins (i.e., Oncostatin M, TNF-α, and IL-6). Importantly, the 1,25(OH)2D-mediated suppression of osteogenic function in M1 macrophages at the proinflammatory stage was associated with 1,25(OH)2D-mediated reduction of MSC abundance, compromised osteogenic potential of MSCs, and impairment of fracture repair. Furthermore, outside the proinflammatory stage, 1,25(OH)2D treatment did not suppress fracture repair. Accordingly, our data support 2 conclusions: (a) M1 macrophages are important for the recruitment and osteogenic priming of MSCs and, hence, are necessary for fracture repair, and (b) under vitamin D-sufficient conditions, 1,25(OH)2D treatment is unnecessary and can be detrimental if provided during the proinflammatory stage of fracture healing.

Detection of dinitrosyl iron complexes by ozone-based chemiluminescence

Dinitrosyl iron complexes (DNICs) are important intermediates in the metabolism of nitric oxide (NO). They have been considered to be NO storage adducts able to release NO, scavengers of excess NO during inflammatory hypotensive shock, and mediators of apoptosis in cancer cells, among many other functions. Currently, all studies of DNICs in biological matrices use electron paramagnetic resonance (EPR) for both detection and quantification. EPR is limited, however, by its ability to detect only paramagnetic mononuclear DNICs even though EPR-silent binuclear are likely to be prevalent. Furthermore, physiological concentrations of mononuclear DNICs are usually lower than the EPR detection limit (1 μM). We have thus developed a chemiluminescence-based method for the selective detection of both DNIC forms at physiological, pathophysiological, and pharmacologic conditions. We have also demonstrated the use of the new method in detecting DNIC formation in the presence of nitrite and nitrosothiols within biological fluids and tissue. This new method, which can be used alone or in tandem with EPR, has the potential to offer insight about the involvement of DNICs in many NO-dependent pathways.

Deficient arginase II expression without alteration in arginase I expression attenuated experimental autoimmune encephalomyelitis in mice

In the past there have been a multitude of studies that ardently support the role of arginase II (Arg II) in vascular and endothelial disorders; however, the regulation and function of Arg II in autoimmune diseases has thus far remained unclear. Here we report that a global Arg II null mutation in mice suppressed experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. During EAE, both Arg I and Arg II were induced in spinal cords, but only Arg II was induced in spleens and splenic dendritic cells (DCs). DC activation by lipopolysaccharide (LPS), CD40L or TLR8 agonist significantly enhanced Arg II expression without affecting Arg I expression. Conversely, DC differentiating cytokines [IL-4 and granulocyte macrophage-colony-stimulating factor (GM-CSF)] yielded opposite effects. In addition, Arg I and Arg II were regulated differentially during Th1 and Th17 cell polarization. Arg II deficiency in mice delayed EAE onset, ameliorated clinical symptoms and reduced myelin loss, accompanied by a remarkable reduction in the EAE-induced spinal cord expression of Th17 cell markers (IL-17 and RORγt). The abundance of Th17 cells and IL-23+ cells in relevant draining lymph nodes was significantly reduced in Arg II knockout mice. In activated DCs, Arg II deficiency significantly suppressed the expression of Th17-differentiating cytokines IL-23 and IL-6. Interestingly, Arg II deficiency did not lead to any compensatory increase in Arg I expression in vivo and in vitro. In conclusion, Arg II was identified as a factor promoting EAE likely via an Arg I-independent mechanism. Arg II may promote EAE by enhancing DC production of Th17-differentiating cytokines. Specific inhibition of Arg II could be a potential therapy for multiple sclerosis.

Overlapping Peptide Library to Map Qa-1 Epitopes in a Protein

Qa-1 (HLA-E in human) belongs to a group of non-classical major histocompatibility complex 1b (MHC-Ib) molecules. Recent data suggest that Qa-1 molecules play important roles in surveying cells for structural and functional integrity, inducing immune regulation, and limiting immune responses to viral infections. Additionally, functional augmentation of Qa-1-restricted CD8⁺ T cells through epitope immunization has shown therapeutic effects in several autoimmune disease animal models, e.g. experimental allergic encephalomyelitis, collagen-induced arthritis, and non-obese diabetes. Therefore, there is an urgent need for a method that can efficiently and quickly identify functional Qa-1 epitopes in a protein. Here, we describe a protocol that utilizes Qa-1-restricted CD8⁺ T cell lines specific for an overlapping peptide (OLP) library for determining Qa-1 epitopes in a protein. This OLP library contains 15-mer overlapping peptides that cover the whole length of a protein, and adjacent peptides overlap by 11 amino acids. Using this protocol, we recently identified a 9-mer Qa-1 epitope in myelin oligodendrocyte glycoprotein (MOG). This newly mapped MOG Qa-1 epitope was shown to induce epitope-specific, Qa-1-restricted CD8⁺ T cells that enhanced myelin-specific immune regulation. Therefore, this protocol is useful for future investigation of novel targets and functions of Qa-1-restricted CD8⁺ T cells.

Abstract P245: Microrna-145-5p, a Potential Therapeutic Target of Regulating Vascular Calcification

Vascular calcification (VC) occurs in most otherwise normal individuals over 60 years of age and is intimately linked to hypertension with severe cardiovascular complications, resulting in considerable morbidity and sometimes death. VC is characterized by the deposition of bone tissue within the vessel wall. The cause of VC is unknown although considerable progress has been made in characterizing its pathogenesis. There is direct or indirect evidence for several factors which could contribute to VC including, vitamin K deficiency, magnesium deficiency increased parathyroid hormone, increased serum phosphate, increased BMP activity and microRNAs (a small non-coding RNA molecules). The BMP pathway deserves attention because it is the sine qua non of osteoblast differentiation. With respect to microRNAs, these also could be relevant to the cause of VC because microRNAs are known to influence VC, and importantly, microRNAs can change with age. Here, we used an in vitro model to mimic VC using osteogenic medium in a vascular smooth muscle cell (VSMC) line. From microRNA analysis using quantitative real-time PCR we identified a potential key microRNA, miR-145-5p involved in vascular calcification. Specifically, we found that in our in vitro model of VC has a significant decrease in miR-145-5p expression. In silico analysis revealed that miR-145-5p may bind and regulate SMAD5, which mediates the action of BMP. Accordingly, we found an increase in SMAD5 expression at the mRNA level in VC condition in vitro . Based on the foregoing, we now propose the hypothesis that in young normal individuals, miR-145-5p normally suppresses SMAD5 activity in vasculature; whereas, in aging, miR-145-5p expression is impaired which would result in increasing SMAD5 gene expression, as well as its phosphorylation, which in turn would eventually lead to VC. Thus, miR-145-5p might be a potential therapeutic target to regulate VC in the elderly.

Unique Regenerative Mechanism to Replace Bone Lost During Dietary Bone Depletion in Weanling Mice

The present study was undertaken to determine the mechanism whereby calcitropic hormones and mesenchymal stem cell progeny changes are involved in bone repletion, a regenerative bone process that restores the bone lost to calcium deficiency. To initiate depletion, weanling mice with a mixed C57BL/6 (75%) and CD1 (25%) genetic background were fed a calcium-deficient diet (0.01%) for 14 days. For repletion, the mice were fed a control diet containing 1.2% calcium for 14 days. Depletion decreased plasma calcium and increased plasma parathyroid hormone, 1,25(OH)2D (calcitriol), and C-terminal telopeptide of type I collagen. These plasma parameters quickly returned toward normal on repletion. The trabecular bone volume and connectivity decreased drastically during depletion but were completely restored by the end of repletion. This bone repletion process largely resulted from the development of new bone formation. When bromodeoxyuridine (BrdU) was administered in the middle of depletion for 3 days and examined by fluorescence-activated cell sorting at 7 days into repletion, substantial increases in BrdU incorporation were seen in several CD105 subsets of cells of osteoblastic lineage. When BrdU was administered on days 1 to 3 of repletion and examined 11 days later, no increases in BrdU were seen in these subsets. Additionally, osteocytes that stained positively for BrdU were increased during depletion. In conclusion, the results of the present study have established a unique regenerative mechanism to initiate bone repair during the bone insult. Calcium homeostatic mechanisms and the bone repletion mechanism are opposing functions but are simultaneously orchestrated such that both endpoints are optimized. These results have potential clinical relevance for disease entities such as type 2 osteoporosis.

Dendritic cells, engineered to overexpress 25-hydroxyvitamin D 1α-hydroxylase and pulsed with a myelin antigen, provide myelin-specific suppression of ongoing experimental allergic encephalomyelitis

Multiple sclerosis (MS) is caused by immune-mediated damage of myelin sheath. Current therapies aim to block such immune responses. However, this blocking is not sufficiently specific and hence compromises immunity, leading to severe side effects. In addition, blocking medications usually provide transient effects and require frequent administration, which further increases the chance to compromise immunity. In this regard, myelin-specific therapy may provide the desired specificity and a long-lasting therapeutic effect by inducing myelin-specific regulatory T (T_reg) cells. Tolerogenic dendritic cells (TolDCs) are one such therapy. However, ex vivo generated TolDCs may be converted into immunogenic DCs in a proinflammatory environment. In this study, we identified a potential novel myelin-specific therapy that works with immunogenic DCs, hence without the in vivo conversion concern. We showed that immunization with DCs, engineered to overexpress 25-hydroxyvitamin D 1α-hydroxylase for de novo synthesis of a focally high 1,25-dihydroxyvitamin D concentration in the peripheral lymphoid tissues, induced T_reg cells. In addition, such engineered DCs, when pulsed with a myelin antigen, led to myelin-specific suppression of ongoing experimental allergic encephalomyelitis (an MS animal model), and the disease suppression depended on forkhead-box-protein-P3(foxp3)⁺ T_reg cells. Our data support a novel concept that immunogenic DCs can be engineered for myelin-specific therapy for MS.—Li, C.-H., Zhang, J., Baylink, D. J., Wang, X., Goparaju, N. B., Xu, Y., Wasnik, S., Cheng, Y., Berumen, E. C., Qin, X., Lau, K.-H. W., Tang, X. Dendritic cells, engineered to overexpress 25-hydroxyvitamin D 1α-hydroxylase and pulsed with a myelin antigen, provide myelin-specific suppression of ongoing experimental allergic encephalomyelitis.

Effect of aging on stem cells

Pluripotent stem cells have the remarkable self-renewal ability and are capable of differentiating into multiple diverse cells. There is increasing evidence that the aging process can have adverse effects on stem cells. As stem cells age, their renewal ability deteriorates and their ability to differentiate into the various cell types is altered. Accordingly, it is suggested aging-induced deterioration of stem cell functions may play a key role in the pathophysiology of the various aging-associated disorders. Understanding the role of the aging process in deterioration of stem cell function is crucial, not only in understanding the pathophysiology of aging-associated disorders, but also in future development of novel effective stem cell-based therapies to treat aging-associated diseases. This review article first focuses on the basis of the various aging disease-related stem cell dysfunction. It then addresses the several concepts on the potential mechanism that causes aging-related stem cell dysfunction. It also briefly discusses the current potential therapies under development for aging-associated stem cell defects.

Conditional deletion of IGF-I in osteocytes unexpectedly accelerates bony union of the fracture gap in mice

This study evaluated the effects of deficient IGF-I expression in osteocytes on fracture healing. Transgenic mice with conditional knockout (cKO) of Igf1 in osteocytes were generated by crossing Dmp1-Cre mice with Igf1 flox mice. Fractures were created on the mid-shaft of tibia of 12-week-old male cKO mice and wild-type (WT) littermates by three-point bending. At 21 and 28days post-fracture healing, the increases in cortical bone mineral density, mineral content, bone area, and thickness, as well as sub-cortical bone mineral content at the fracture site were each greater in cKO calluses than in WT calluses. There were 85% decrease in the cartilage area and >2-fold increase in the number of osteoclasts in cKO calluses at 14days post-fracture, suggesting a more rapid remodeling of endochondral bone. The upregulation of mRNA levels of osteoblast marker genes (cbfa1, alp, Opn, and Ocn) was greater in cKO calluses than in WT calluses. μ-CT analysis suggested an accelerated bony union of the fracture gap in cKO mice. The Sost mRNA level was reduced by 50% and the Bmp2 mRNA level was increased 3-fold in cKO fractures at 14days post-fracture, but the levels of these two mRNAs in WT fractures were unchanged, suggesting that the accelerated fracture repair may in part act through the Wnt and/or BMP signaling. In conclusion, conditional deletion of Igf1 in osteocytes not only did not impair, but unexpectedly enhanced, bony union of the fracture gap. The accelerated bony union was due in part to upregulation of the Wnt and BMP2 signaling in response to deficient osteocyte-derived IGF-I expression, which in turn favors intramembranous over endochondral bone repair.

Targeting Non-classical Myelin Epitopes to Treat Experimental Autoimmune Encephalomyelitis

Qa-1 epitopes, the peptides that bind to non-classical major histocompatibility complex Ib Qa-1 molecules and are recognized by Qa-1-restricted CD8⁺ regulatory T (Treg) cells, have been identified in pathogenic autoimmune cells that attack myelin sheath in experimental autoimmune encephalomyelitis (EAE, an animal model for multiple sclerosis [MS]). Additionally, immunization with such epitopes ameliorates the EAE. However, identification of such epitopes requires knowledge of the pathogenic autoimmune cells which are largely unknown in MS patients. Hence, we asked whether the CD8⁺ Treg cells could directly target the myelin sheath to ameliorate EAE. To address this question, we analyzed Qa-1 epitopes in myelin oligodendrocyte glycoprotein (MOG that is a protein in myelin sheath). Here, we report identification of a MOG-specific Qa-1 epitope. Immunization with this epitope suppressed ongoing EAE, which was abrogated by CD8⁺ T cell depletion. Additionally, the epitope immunization activated the epitope-specific CD8⁺ T cells which specifically accumulated in the CNS-draining cervical lymph nodes. Finally, CD8⁺ T cells primed by the epitope immunization transferred EAE suppression. Hence, this study reveals a novel regulatory mechanism mediated by the CD8⁺ Treg cells. We propose that immunization with myelin-specific HLA-E epitopes (human homologues of Qa-1 epitopes) is a promising therapy for MS.

Generation of Mesenchymal Stem Cells by Blood Cell Reprogramming

Mesenchymal stem cells (MSCs) have been successfully used to treat multiple diseases in animal studies and clinical trials. Currently, the commonly used MSCs are derived from bone marrow and adipose tissue. Alternative approaches include differentiation of induced pluripotent stem cells (iPSCs) into MSCs, or direct reprogramming of blood cells into MSCs. This review summarizes recent progresses concerning how to generate MSCs by blood cell reprogramming and how studies in cellular reprogramming may help identify new factors to expand or even rejuvenate adult MSCs.

MicroRNA223 promotes pathogenic T-cell development and autoimmune inflammation in central nervous system in mice

Multiple sclerosis (MS) is an incurable central nervous system autoimmune disease. Understanding MS pathogenesis is essential for the development of new MS therapies. In the present study, we identified a novel microRNA (miR) that regulates experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Expression of miR223 was up-regulated specifically in spinal cords and lymphoid organs but not in other examined tissues. A global miR223 knockout (miR223(-/-) ) in mice led to a significant delay in EAE onset, reduction in spinal cord lesion, and lessening of neurological symptoms. These protective effects could be reproduced in bone marrow chimeras reconstituted with miR223(-/-) haematopoietic stem cells. We also found that miR223 deficiency reduced T helper type 1 (Th1) and Th17 infiltration into spinal cords. To address underlying mechanisms, we investigated the role of miR223 in regulating the function, development and interaction of the major immune cells. Expression of the genes associated with dendritic cell (DC) activation (CD86 and MHC II) and Th1 and Th17 differentiation [interleukin-12 (IL-12) and IL-23, respectively] was significantly decreased in the spleens of miR223(-/-) mice bearing EAE. The miR223(-/-) DCs expressed significantly lower levels of basal and lipopolysaccharide-induced IL-12 and IL-23 compared with the wild-type DCs. These data are consistent with the observed lower efficiency of miR223(-/-) DCs to support Th1 and Th17 differentiation from naive T cells over-expressing an EAE antigen-specific T-cell receptor. Our data suggest that miR223 promotes EAE, probably through enhancing DC activation and subsequently the differentiation of naive T cells toward Th1 and Th17 effector cells.

Vitamin D status and metabolism in an ovine pregnancy model: effect of long-term, high-altitude hypoxia

Vitamin D status increases during healthy mammalian pregnancy, but the molecular determinants remain uncharacterized. The first objective of this study was to determine the effects of pregnancy, and the second objective was to examine the role of chronic hypoxia on vitamin D status and metabolism in an ovine model. We analyzed the plasma levels of cholecalciferol, 25-OH-D, and 1α,25-(OH)2D in nonpregnant ewes, near-term pregnant ewes, and their fetuses exposed to normoxia (low altitude) or hypoxia (high-altitude) for 100 days. Hypoxic sheep had increased circulating levels of 25-OH-D and 1α,25-(OH)2D compared with normoxic sheep. Hypoxia increases in 25-OH-D were associated with increased expression of renal 25-hydroxylases CYP2R1 and CYP2J. Pregnancy did not increase further the plasma levels of 25-OH-D, but it significantly increased those of the active metabolite, 1α,25-(OH)2D, in both normoxic and hypoxic ewes. Increased bioactivation of vitamin D correlated with increased expression of the vitamin D-activating enzyme CYP27b1 and decreased expression of the inactivating enzyme CYP24a1 in maternal kidneys and placentas. Hypoxia increased parathyroid hormone levels and further increased renal CYP27b1. Pregnancy and hypoxia decreased the expression of vitamin D receptor (VDR) in maternal kidney and lung, with opposite effects on placental VDR. We conclude that ovine pregnancy is a model of increased vitamin D status, and long-term hypoxia further improves vitamin D status due to pregnancy- and hypoxia-specific regulation of VDR and metabolic enzymes.

Patient-specific cardiovascular progenitor cells derived from integration-free induced pluripotent stem cells for vascular tissue regeneration

Tissue-engineered blood vessels (TEBVs) are promising in regenerating a live vascular replacement. However, the vascular cell source is limited, and it is crucial to develop a scaffold that accommodates new type of vascular progenitor cells and facilitates in vivo lineage specification of the cells into functional vascular smooth muscle cells (VSMCs) to regenerate vascular tissue. In the present study, integration-free human induced pluripotent stem cells (hiPSCs) were established from patient peripheral blood mononuclear cells through episomal vector nucleofection of reprogramming factors. The established hiPSCs were then induced into mesoderm-originated cardiovascular progenitor cells (CVPCs) with a highly efficient directed lineage specification method. The derived CVPCs were demonstrated to be able to differentiate into functional VSMCs. Subcutaneous implantation of CVPCs seeded on macroporous nanofibrous poly(l-lactide) scaffolds led to in vivo VSMC lineage specification and matrix deposition inside the scaffolds. In summary, we established integration-free patient-specific hiPSCs from peripheral blood mononuclear cells, derived CVPCs through directed lineage specification, and developed an advanced scaffold for these progenitor cells to further differentiate in vivo into VSMCs and regenerate vascular tissue in a subcutaneous implantation model. This study has established an efficient patient-specific approach towards in vivo regeneration of vascular tissue.

PDGFB-based stem cell gene therapy increases bone strength in the mouse

Substantial advances have been made in the past two decades in the management of osteoporosis. However, none of the current medications can eliminate the risk of fracture and rejuvenate the skeleton. To this end, we recently reported that transplantation of hematopoietic stem/progenitor cells (HSCs) or Sca1(+) cells engineered to overexpress FGF2 results in a significant increase in lamellar bone matrix formation at the endosteum; but this increase was attended by the development of secondary hyperparathyroidism and severe osteomalacia. Here we switch the therapeutic gene to PDGFB, another potent mitogen for mesenchymal stem cells (MSCs) but potentially safer than FGF2. We found that modest overexpression of PDGFB using a relatively weak phosphoglycerate kinase (PGK) promoter completely avoided osteomalacia and secondary hyperparathyroidism, and simultaneously increased trabecular bone formation and trabecular connectivity, and decreased cortical porosity. These effects led to a 45% increase in the bone strength. Transplantation of PGK-PDGFB-transduced Sca1(+) cells increased MSC proliferation, raising the possibility that PDGF-BB enhances expansion of MSC in the vicinity of the hematopoietic niche where the osteogenic milieu propels the differentiation of MSCs toward an osteogenic destination. Our therapy should have potential clinical applications for patients undergoing HSC transplantation, who are at high risk for osteoporosis and bone fractures after total body irradiation preconditioning. It could eventually have wider application once the therapy can be applied without the preconditioning.

Local administration of AAV-DJ pseudoserotype expressing COX2 provided early onset of transgene expression and promoted bone fracture healing in mice

We have previously obtained compelling proof-of-principle evidence for COX2 gene therapy for fracture repair using integrating retroviral vectors. For this therapy to be suitable for patient uses, a suitable vector with high safety profile must be used. Accordingly, this study sought to evaluate the feasibility of AAV as the vector for this COX2 gene therapy, because AAV raises less safety issues than the retroviral vectors used previously. However, an appropriate AAV serotype is required to provide early increase in and adequate level of COX2 expression that is needed for fracture repair. Herein, we reported that AAV-DJ, an artificial AAV pseudoserotype, is highly effective in delivering COX2 gene to fracture sites in a mouse femoral fracture model. Compared with AAV-2, the use of AAV-DJ led to ~5-fold increase in infectivity in mesenchymal stem cells (MSCs) and provided an earlier and significantly higher level of transgene expression at the fracture site. Injection of this vector at a dose of 7.5 × 10(11) genomic copies led to high COX2 level at the fracture site on day 3 after injections and significantly promoted fracture union at 21 days, as analyzed by radiography and μ-CT. The therapeutic effect appears to involve enhanced osteoblastic differentiation of MSCs and remodeling of callus tissues to laminar bone. This interpretation is supported by the enhanced expression of several key genes participating in the fracture repair process. In conclusion, AAV-DJ is a promising serotype for the AAV-based COX2 gene therapy of fracture repair in humans.

Targeted 25-hydroxyvitamin D3 1α-hydroxylase adoptive gene therapy ameliorates dss-induced colitis without causing hypercalcemia in mice

Systemic 1,25(OH)2D3 treatment ameliorating murine inflammatory bowel diseases (IBD) could not be applied to patients because of hypercalcemia. We tested the hypothesis that increasing 1,25(OH)2D3 synthesis locally by targeting delivery of the 1α-hydroxylase gene (CYP27B1) to the inflamed bowel would ameliorate IBD without causing hypercalcemia. Our targeting strategy is the use of CD11b(+)/Gr1(+) monocytes as the cell vehicle and a macrophage-specific promoter (Mac1) to control CYP27B1 expression. The CD11b(+)/Gr1(+) monocytes migrated initially to inflamed colon and some healthy tissues in dextran sulfate sodium (DSS) colitis mice; however, only the migration of monocytes to the inflamed colon was sustained. Adoptive transfer of Gr1(+) monocytes did not cause hepatic injury. Infusion of Mac1-CYP27B1-modified monocytes increased body weight gain, survival, and colon length, and expedited mucosal regeneration. Expression of pathogenic Th17 and Th1 cytokines (interleukin (IL)-17a and interferon (IFN)-α) was decreased, while expression of protective Th2 cytokines (IL-5 and IL-13) was increased, by the treatment. This therapy also enhanced tight junction gene expression in the colon. No hypercalcemia occurred following this therapy. In conclusion, we have for the first time obtained proof-of-principle evidence for a novel monocyte-based adoptive CYP27B1 gene therapy using a mouse IBD model. This strategy could be developed into a novel therapy for IBD and other autoimmune diseases.

Role of Osteocyte-derived Insulin-Like Growth Factor I in Developmental Growth, Modeling, Remodeling, and Regeneration of the Bone

The osteocyte has long been considered to be the primary mechanosensory cell in the bone. Recent evidence has emerged that the osteocyte is also a key regulator of various bone and mineral metabolism and that its regulatory effects are in part mediated through locally produced osteocyte-derived factors, such as sclerostin, receptor activator of nuclear factor-kappa B ligand (RANKL), and fibroblast growth factor (FGF)-23. Osteocytes secrete large amounts of insulin-like growth factor (IGF)-I in bone. Although IGF-I produced locally by other bone cells, such as osteoblasts and chondrocytes, has been shown to play important regulatory roles in bone turnover and developmental bone growth, the functional role of osteocyte-derived IGF-I in the bone and mineral metabolism has not been investigated and remains unclear. However, results of recent studies in osteocyte Igf1 conditional knockout transgenic mice have suggested potential regulatory roles of osteocyte-derived IGF-I in various aspects of bone and mineral metabolism. In this review, evidence supporting a regulatory role for osteocyte-derived IGF-I in the osteogenic response to mechanical loading, the developmental bone growth, the bone response to dietary calcium depletion and repletion, and in fracture repair is discussed. A potential coordinated regulatory relationship between the effect of osteocyte-derived IGF-I on bone size and the internal organ size is also proposed.

Characterization of an animal model of pregnancy-induced vitamin D deficiency due to metabolic gene dysregulation

Vitamin D deficiency has been associated with pregnancy complications such as preeclampsia, gestational diabetes, and recurrent miscarriage. Therefore, we hypothesized differences in vitamin D status between healthy [Sprague-Dawley (SD) and Lewis (LW)] and complicated [Brown Norway (BN)] rat pregnancies. In SD, LW, and BN rats, we analyzed the maternal plasma levels of the vitamin D metabolites 25-OH-D and 1,25-(OH)2-D at prepregnancy, pregnancy, and postpartum. Analysis of the active metabolite 1,25-(OH)2-D showed a twofold increase in pregnant SD and LW rats but a nearly 10-fold decrease in pregnant BN rats compared with nonpregnant controls. BN rats had a pregnancy-dependent upregulation of CYP24a1 expression, a key enzyme that inactivates vitamin D metabolites. In contrast, the maternal renal expression of CYP24a1 in SD and LW rats remained constant throughout pregnancy. Analysis of the vitamin D receptor (VDR) indicated that LW and SD but not BN rats experience a pregnancy-induced 10-fold decrease in maternal renal VDR protein levels. Further analysis of bisulfite-converted and genomic DNA indicated that the observed differences in maternal renal regulation of CYP24a1 during pregnancy and lactation are not due to differences in CYP24a1 promoter methylation or single-nucleotide polymorphisms. Finally, supplementation with 1,25-(OH)2-D significantly improved the reproductive phenotype of BN rats by increasing litter size and maternal-fetal weight outcomes. We conclude that BN rats represent a novel animal model of pregnancy-specific vitamin D deficiency that is linked to pregnancy complications. Vitamin D deficiency in BN rats correlates with maternal renal CYP24a1 upregulation followed by CYP27b1 upregulation.

ENU mutation mapped to a distal region of chromosome 11 is a major determinant of bone size

Using a phenotype driven n-ethyl-nitrosourea (ENU) screen in growth hormone-deficient mice, we have identified a mutant (named 14104) that exhibited a smaller bone size. Phenotype measurements by microcomputed tomography revealed that mutant mice exhibited a 43 and 34% reduction in tissue area and bone area, respectively at the femur middiaphysis. Dynamic histomorphometry revealed a 30 and 15% lower bone formation rate at the periosteal and endosteal surface, respectively. Breaking strength of the femur was reduced by 30% in the mutant mice. To determine if the 14104 locus is involved in a mechanical loading signaling pathway, the skeletal anabolic response to tibia axial loading was evaluated. The increase in trabecular response in the loaded region was severely compromised by the 14014 mutation. To identify the location of mutation, we performed linkage analysis using 62 polymorphic markers in the B6-DBA/2J F2 mice. The genome-wide linkage analysis identified the location of the mutation to a 72 to 83 cM region on chromosome 11 with peak logarithm of the odds scores of 15 for periosteal circumference at marker D11mit338. Sequence analysis revealed no mutation in the coding region of 11 potential candidate genes. Based on these data and published data on the skeletal phenotype of genes in this region, we concluded that the 109-119 Mb region of chromosome 11 harbors a bone size gene that regulates periosteal bone formation. The mutant strain developed in this study provides an important tool to identify a novel mechanosensitive gene that determines bone size during postnatal development.

Osteocyte-derived insulin-like growth factor I is essential for determining bone mechanosensitivity

This study sought to determine whether deficient Igf1 expression in osteocytes would affect loading-induced osteogenic response. Tibias of osteocyte Igf1 conditional knockout (KO) mice (generated by cross-breeding Igf1 floxed mice with Dmp1-Cre transgenic mice) and wild-type (WT) littermates were subjected to four-point bending for 2 wk. Microcomputed tomography confirmed that the size of tibias of conditional mutants was smaller. Loading with an equivalent loading strain increased periosteal woven bone and endosteal lamellar bone formation in WT mice but not in conditional KO mice. Consistent with the lack of an osteogenic response, the loading failed to upregulate expression of early mechanoresponsive genes (Igf1, Cox-2, c-fos) or osteogenic genes (Cbfa-1, and osteocalcin) in conditional KO bones. The lack of osteogenic response was not due to reduced osteocyte density or insufficient loading strain. Deficient osteocyte Igf1 expression reduced the loading-induced upregulation of expression of canonical Wnt signaling genes (Wnt10b, Lrp5, Dkk1, sFrp2). The loading also reduced (by 40%) Sost expression in WT mice, but the loading not only did not reduce but upregulated (~1.5-fold) Sost expression in conditional KO mice. Conditional disruption of Igf1 in osteocytes also abolished the loading-induced increase in the bone β-catenin protein level. These findings suggest an impaired response in the loading-induced upregulation of the Wnt signaling in conditional KO mice. In summary, conditional disruption of Igf1 in osteocytes abolished the loading-induced activation of the Wnt signaling and the corresponding osteogenic response. In conclusion, osteocyte-derived IGF-I plays a key determining role in bone mechanosensitivity.

Efficient generation of integration-free ips cells from human adult peripheral blood using BCL-XL together with Yamanaka factors

The ability to efficiently generate integration-free induced pluripotent stem cells (iPSCs) from the most readily available source-peripheral blood-has the potential to expedite the advances of iPSC-based therapies. We have successfully generated integration-free iPSCs from cord blood (CB) CD34(+) cells with improved oriP/EBNA1-based episomal vectors (EV) using a strong spleen focus forming virus (SFFV) long terminal repeat (LTR) promoter. Here we show that Yamanaka factors (OCT4, SOX2, MYC, and KLF4)-expressing EV can also reprogram adult peripheral blood mononuclear cells (PBMNCs) into pluripotency, yet at a very low efficiency. We found that inclusion of BCL-XL increases the reprogramming efficiency by approximately 10-fold. Furthermore, culture of CD3(-)/CD19(-) cells or T/B cell-depleted MNCs for 4-6 days led to the generation of 20-30 iPSC colonies from 1 ml PB, an efficiency that is substantially higher than previously reported. PB iPSCs express pluripotency markers, form teratomas, and can be induced to differentiate in vitro into mesenchymal stem cells, cardiomyocytes, and hepatocytes. Used together, our optimized factor combination and reprogramming strategy lead to efficient generation of integration-free iPSCs from adult PB. This discovery has potential applications in iPSC banking, disease modeling and regenerative medicine.

Cellular and molecular mechanisms of accelerated fracture healing by COX2 gene therapy: studies in a mouse model of multiple fractures

This study sought to determine the cellular and molecular mechanisms of cyclooxygenase-2 (COX2) gene therapy to accelerate fracture repair in a mouse multiple tibial fractures model. The lenti-COX2 (or lenti-gfp control vector) was injected into fractures on day 1 post-fracture. At days 3-7, the COX2 treatment increased Sdf1-, Cxcr4-, Nes-, and Podxl-expressing mesenchymal stem cells (MSCs) within fracture calluses, suggesting an enhanced MSC recruitment or expansion. The COX2-treated mice formed smaller cartilaginous calluses that had less cartilage tissues than control mice. The expression of Sox9 mRNA was 7-fold less in COX2-treated than in control calluses at day 14, implying that COX2 reduces chondrocytic differentiation of MSCs. The therapy also enhanced angiogenesis as reflected by increased immunostaining of CD31, vWF, and α-SMA over controls in the cartilaginous callus at day 14-21. At which time, the COX2 gene therapy promoted bony remodeling of the cartilaginous callus to bridge the fracture gap that was accompanied by 2-fold increase in osteoclasts along the surface of the woven bone and an onset of osteogenesis. Blocking angiogenesis with daily injection of endostatin from day 4 to day 10 into fracture sites blocked the COX2-mediated reduction of callus size that was associated with an increase in hypertrophic chondrocytes and concomitant reduction in osteoclasts. In conclusion, COX2 accelerates fracture healing in part through three biological actions: 1) increased recruitment/expansion of MSCs; 2) decreased cartilaginous callus formation; and 3) increased angiogenesis-dependent cartilage remodeling. These effects were associated with an earlier onset of bony bridging of the fracture gap.

1,25-Dihydroxyvitamin D3 suppresses TLR8 expression and TLR8-mediated inflammatory responses in monocytes in vitro and experimental autoimmune encephalomyelitis in vivo

1,25-Dihydroxyvitamin D3 (1,25(OH)₂D₃) suppresses autoimmunity and inflammation; however, the mechanism of its action has not been fully understood. We sought in this study to determine whether the anti-immune/anti-inflammatory action of 1,25(OH)₂D₃ is in part mediated through an interplay between 1,25(OH)₂D₃ and toll-like receptor (TLR)7/8 signaling. 1,25(OH)₂D₃ treatment prior to and/or following experimental autoimmune encephalomyelitis (EAE) induction effectively reduced inflammatory cytokine expression in the spinal cord and ameliorated EAE. These effects were accompanied with a reduction in expression of several TLRs with the most profound effect observed for TLR8. The expression of TLR8 adaptor protein MyD88 was also significantly reduced by 1,25(OH)₂D₃. To determine the molecular mechanism by which 1,25(OH)₂D₃ suppresses EAE induction of TLR8 and inflammatory cytokine expression, we evaluated whether 1,25(OH)₂D₃ can directly inhibit TLR8 signaling and the resulting inflammatory responses in human THP-1 monocytes. 1,25(OH)₂D₃ treatment not only significantly reduced TLR8 expression but also the expression or activity of MyD88, IRF-4, IRF-7 and NF-kB in monocytes challenged with TLR8 ligands. TLR8 promoter-luciferase reporter assays indicated that 1,25(OH)₂D₃ decreases TLR8 mRNA level in part via inhibiting TLR8 gene transcription activity. As a result of inhibition on TLR8 signaling cascade at various stages, 1,25(OH)₂D₃ significantly diminished the TLR8 target gene expression (TNF-α and IL-1β). In summary, our novel findings suggest that TLR8 is a new target of 1,25(OH)₂D₃ and may mediate the anti-inflammatory action of 1,25(OH)₂D₃. Our findings also point to a destructive role of TLR8 in EAE and shed lights on pathogenesis of multiple sclerosis.

Disruption of the insulin-like growth factor-1 gene in osteocytes impairs developmental bone growth in mice

This study evaluated the role of osteocyte-derived insulin-like growth factor 1 (IGF-1) in developmental bone growth by assessing the bone phenotype of osteocyte Igf1 conditional knockout (KO) mice, generated by crossing the Dmp1-driven Cre-expressing transgenic mice with Igf1 floxed mice containing loxP sites that flank exon 4 of the Igf1 gene. The periosteal diameter of femurs of homozygous conditional KO mutants was 8-12% smaller than wild-type (WT) littermates. The conditional mutants had 14-20%, 10-21%, and 15-31% reduction in total, trabecular, and cortical bone mineral contents, respectively. However, there were no differences in the total, trabecular, or cortical bone mineral densities, or in trabecular bone volume, thickness, number, and separation at secondary spongiosa between the mutants and WT littermates. The conditional KO mutants showed reduction in dynamic bone formation parameters at both periosteal and endosteal surfaces at the mid-diaphysis and in trabecular bone formation rate and resorption parameters at secondary spongiosa. The lower plasma levels of PINP and CTx in conditional KO mice support a regulatory role of osteocyte-derived IGF-1 in the bone turnover. The femur length of conditional KO mutants was 4-7% shorter due to significant reduction in the length of growth plate and hypertropic zone. The effect on periosteal expansion appeared to be bigger than that on longitudinal bone growth. The conditional KO mice had 14% thinner calvaria than WT littermates, suggesting that deficient osteocyte IGF-1 production also impairs developmental growth of intramembraneous bone. Conditional disruption of Igf1 in osteocytes did not alter plasma levels of IGF-1, calcium, or phosphorus. In summary, this study shows for the first time that osteocyte-derived IGF-1 plays an essential role in regulating bone turnover during developmental bone growth.

Transgenic overexpression of pregnancy-associated plasma protein-A in skeletal muscle of mice increases myofiber size and central nucleation in sedentary muscle and promotes muscle regeneration in the injured muscle

OBJECTIVE

While there is compelling evidence for an anabolic role of PAPP-A, an IGFBP protease, in muscle development, its effect on dynamic regulation of muscle regeneration has not been investigated. In this study, we evaluated the effect of transgenic PAPP-A overexpression in skeletal muscle of mice on myofiber formation in intact and crush-injured tibialus anterior muscle.

DESIGN

Skeletal muscle in transgenic mice overexpressing human PAPP-A in skeletal muscle was subjected to crush-injury. Myofiber formation and myogenic gene expression were then evaluated in injured or intact muscle of PAPP-A transgenic mice and wild-type mice.

RESULTS

In the intact muscle, aging PAPP-A transgenic (Tg.) mice (age of 12 months) showed more than a 2-fold increase in both myofiber size and number of nuclei per myofiber compared with their wild-type (Wt.) littermates. Myofibers with centered nuclei, a hallmark of muscle regeneration, were increased from <1% in Wt. mice to 65% in Tg. muscle. In the injured muscle, reduced inflammatory cell infiltration and increased new myofiber size and the area occupied by new myofibers were observed in PAPP-A transgenic mice compared to wild-type littermates. MyoD and creatine kinase in the injured muscle was also significantly increased in the Tg. mice. Although TNF-α induced PAPP-A expression in skeletal myoblast culture and its expression increased upon injury, abrogation of TNF-α signaling in TNF-α receptor knockout mice had no impact on the extent of injury induction of PAPP-A. We also found that TGF-β expression was significantly increased following muscle injury in vivo and treatment with recombinant TGF-β in vitro significantly enhanced PAPP-A expression in skeletal myoblasts.

CONCLUSION

Our findings demonstrate that exogenous PAPP-A can promote recovery of muscle injury in aging mice albeit the expression of endogenous PAPP-A had already been increased dramatically upon muscle injury.

Erythroid promoter confines FGF2 expression to the marrow after hematopoietic stem cell gene therapy and leads to enhanced endosteal bone formation

Fibroblast growth factor-2 (FGF2) has been demonstrated to be a promising osteogenic factor for treating osteoporosis. Our earlier study shows that transplantation of mouse Sca-1(+) hematopoietic stem/progenitor cells that are engineered to express a modified FGF2 leads to considerable endosteal/trabecular bone formation, but it also induces adverse effects like hypocalemia and osteomalacia. Here we report that the use of an erythroid specific promoter, β-globin, leads to a 5-fold decrease in the ratio of serum FGF2 to the FGF2 expression in the marrow cavity when compared to the use of a ubiquitous promoter spleen focus-forming virus (SFFV). The confined FGF2 expression promotes considerable trabeculae bone formation in endosteum and does not yield anemia and osteomalacia. The avoidance of anemia in the mice that received Sca1(+) cells transduced with FGF2 driven by the β-globin promoter is likely due to attenuation of high-level serum FGF2-mediated stem cell mobilization observed in the SFFV-FGF2 animals. The prevention of osteomalacia is associated with substantially reduced serum Fgf23/hypophosphatemia, and less pronounced secondary hyperparathyroidism. Our improved stem cell gene therapy strategy represents one step closer to FGF2-based clinical therapy for systemic skeletal augmentation.

Targeted overexpression of osteoactivin in cells of osteoclastic lineage promotes osteoclastic resorption and bone loss in mice

This study sought to test whether targeted overexpression of osteoactivin (OA) in cells of osteoclastic lineage, using the tartrate-resistant acid phosphase (TRAP) exon 1B/C promoter to drive OA expression, would increase bone resorption and bone loss in vivo. OA transgenic osteoclasts showed ∼2-fold increases in OA mRNA and proteins compared wild-type (WT) osteoclasts. However, the OA expression in transgenic osteoblasts was not different. At 4, 8, and 15.3 week-old, transgenic mice showed significant bone loss determined by pQCT and confirmed by μ-CT. In vitro, transgenic osteoclasts were twice as large, had twice as much TRAP activity, resorbed twice as much bone matrix, and expressed twice as much osteoclastic genes (MMP9, calciton receptor, and ADAM12), as WT osteoclasts. The siRNA-mediated suppression of OA expression in RAW264.7-derived osteoclasts reduced cell size and osteoclastic gene expression. Bone histomorphometry revealed that transgenic mice had more osteoclasts and osteoclast surface. Plasma c-telopeptide (a resorption biomarker) measurements confirmed an increase in bone resorption in transgenic mice in vivo. In contrast, histomorphometric bone formation parameters and plasma levels of bone formation biomarkers (osteocalcin and pro-collagen type I N-terminal peptide) were not different between transgenic mice and WT littermates, indicating the lack of bone formation effects. In conclusion, this study provides compelling in vivo evidence that osteoclast-derived OA is a novel stimulator of osteoclast activity and bone resorption.

Leptin receptor (Lepr) is a negative modulator of bone mechanosensitivity and genetic variations in Lepr may contribute to the differential osteogenic response to mechanical stimulation in the C57BL/6J and C3H/HeJ pair of mouse strains

This study investigated the role of leptin receptor (Lepr) signaling in determining the bone mechanosensitivity and also evaluated whether differences in the Lepr signaling may contribute to the differential osteogenic response of the C57BL/6J (B6) and C3H/HeJ (C3H) pair of mouse strains to mechanical stimuli. This study shows that a loading strain of ∼2,500 με, which was insufficient to produce a bone formation response in B6 mice, significantly increased bone formation parameters in leptin-deficient ob(-)/ob(-) mice and that a loading strain of ∼3,000 με also yielded greater osteogenic responses in Lepr-deficient db(-)/db(-) mice than in wild-type littermates. In vitro, a 30-min steady shear stress increased [(3)H]thymidine incorporation and Erk1/2 phosphorylation in ob(-)/ob(-) osteoblasts and db(-)/db(-) osteoblasts much greater than those in corresponding wild-type osteoblasts. The siRNA-mediated suppression of Lepr expression in B6 osteoblasts enhanced (but in osteoblasts of C3H (the mouse strain with poor bone mechanosensitivity) restored) their anabolic responses to shear stress. The Lepr signaling (leptin-induced Jak2/Stat3 phosphorylation) in C3H osteoblasts was higher than that in B6 osteoblasts. One of the three single nucleotide polymorphisms in the C3H Lepr coding region yielded an I359V substitution near the leptin binding region, suggesting that genetic variation of Lepr may contribute to a dysfunctional Lepr signaling in C3H osteoblasts. In conclusion, Lepr signaling is a negative modulator of bone mechanosensitivity. Genetic variations in Lepr, which result in a dysfunctional Lepr signaling in C3H mice, may contribute to the poor osteogenic response to loading in C3H mice.

Prevention of colorectal cancer with vitamin D

The fact that colorectal cancer (CRC) is the second leading cause of cancer mortality in the United States emphasizes the need for more effective preventive and therapeutic modalities. There is growing evidence that vitamin D may reduce the incidence of CRC. Results of epidemiologic, in vitro, in vivo animal and clinical studies suggest that a low serum vitamin D level may be a serious risk factor for CRC and a high serum vitamin D level may reduce the risk of CRC. On a molecular level, vitamin D suppresses CRC development and growth by affecting cell proliferation, differentiation, apoptosis, and angiogenesis. Vitamin D insufficiency and CRC are common in the elderly population. Vitamin D insufficiency is simple to screen for and treatable with vitamin D supplementation. Serum 25-hydroxyvitamin D (calcidiol) is the best measure of vitamin D status and should be checked routinely for individuals with risk factors for CRC. Maintaining serum concentrations of calcidiol above 32 ng/ml (80 nmol/l) in individuals whose serum calcidiol level is low may help prevent CRC as well as osteoporosis, fractures, infections, and cardiovascular disease. Daily calcidiol intake of 1000 International Units can increase serum vitamin D to sufficient levels in most elderly persons and, based on available data, may substantially lower the incidence of CRC with minimal risks.

Marrow stromal cell-based cyclooxygenase 2 ex vivo gene-transfer strategy surprisingly lacks bone-regeneration effects and suppresses the bone-regeneration action of bone morphogenetic protein 4 in a mouse critical-sized calvarial defect model

This study evaluated whether the murine leukemia virus (MLV)-based cyclooxygenase-2 (Cox-2) ex vivo gene-transfer strategy promotes healing of calvarial defects and/or synergistically enhances bone morphogenetic protein (BMP) 4-mediated bone regeneration. Gelatin scaffolds impregnated with mouse marrow stromal cells (MSCs) transduced with MLV-expressing BMP4, Cox-2, or a control gene were implanted into mouse calvarial defects. Bone regeneration was assessed by X-ray, dual-energy X-ray absorptiometry, and histology. In vitro, Cox-2 or prostanglandin E(2) enhanced synergistically the osteoblastic differentiation action of BMP4 in mouse MSCs. In vivo, implantation of BMP4-expressing MSCs yielded massive bone regeneration in calvarial defects after 2 weeks, but the Cox-2 strategy surprisingly did not promote bone regeneration even after 4 weeks. Staining for alkaline phosphatase (ALP)-expressing osteoblasts was strong throughout the defect of animals receiving BMP2/4-expressing cells, but defects receiving Cox-2-expressing cells displayed weak ALP staining along the edge of original intact bone, indicating that the Cox-2 strategy lacked bone-regeneration effects. The Cox-2 strategy not only lacked bone-regeneration effects but also suppressed the BMP4-induced bone regeneration. In vitro coculture of Cox-2-expressing MSCs with BMP4-expressing MSCs in gelatin scaffolds reduced BMP4 mRNA transcript levels, suggesting that Cox-2 may promote BMP4 gene silencing in BMP4-expressing cells, which may play a role in the suppressive action of Cox-2 on BMP4-mediated bone formation. In summary, the Cox-2 ex vivo gene-transfer strategy not only lacks bone-regeneration effects but also suppresses the bone-regeneration action of BMP4 in healing of calvarial defects.