Therapeutic effects of MSCs, genetically modified MSCs, and NFĸB-inhibitor on chronic inflammatory osteolysis in aged mice

The number of total joint replacements is increasing, especially in elderly patients, and so too are implant-related complications such as prosthesis loosening. Wear particles from the prosthesis induce a chronic inflammatory reaction and subsequent osteolysis, leading to the need for revision surgery. This study investigated the therapeutic effect of NF-ĸB decoy oligodeoxynucleotides (ODN), mesenchymal stem cells (MSCs), and genetically-modified NF-ĸB sensing interleukin-4 over-secreting MSCs (IL4-MSCs) on chronic inflammation in aged mice. The model was generated by continuous infusion of contaminated polyethylene particles into the intramedullary space of the distal femur of aged mice (15-17 months old) for 6 weeks. Local delivery of ODN showed increased bone mineral density (BMD), decreased osteoclast-like cells, increased alkaline phosphatase (ALP)-positive area, and increased M2/M1 macrophage ratio. Local injection of MSCs and IL4-MSCs significantly decreased osteoclast-like cells and increased the M2/M1 ratio, with a greater trend for IL4-MSCs than MSCs. MSCs significantly increased ALP-positive area and BMD values compared with the control. The IL4-MSCs demonstrated higher values for both ALP-positive area and BMD. These findings demonstrated the therapeutic effects of ODN, MSCs, and IL4-MSCs on chronic inflammatory osteolysis in aged mice. The two MSC-based therapies were more effective than ODN in increasing the M2/M1 macrophage ratio, reducing bone resorption, and increasing bone formation. Specifically, MSCs were more effective in increasing bone formation, and IL4-MSCs were more effective in mitigating inflammation. This study suggests potential therapeutic strategies for treating wear particle-associated inflammatory osteolysis after arthroplasty in the elderly.

Longitudinal Cognitive Decline in Patients With Mild Cognitive Impairment or Dementia Due to Alzheimer's Disease

Sensitive cognitive assessments accurately detect and track cognitive decline in Alzheimer's disease. The Cogstate battery was used to measure cognitive change in cognitively normal participants and in individuals with mild cognitive impairment and mild Alzheimer's disease enrolled in the Australian Imaging, Biomarker and Lifestyle Rate of Change Substudy. Over 18 months, verbal episodic memory performance declined for mild cognitive impairment and mild Alzeheimer's disease groups when compared to cognitively normal participants. Frequent assessments of episodic memory may facilitate early detection of cognitive decline due to Alzheimer's disease.

Ageing attenuates bone healing by mesenchymal stem cells in a microribbon hydrogel with a murine long bone critical-size defect model

BACKGROUND

Despite the high incidence of fractures and pseudoarthrosis in the aged population, a potential role for the use of mesenchymal stem cells (MSCs) in the treatment of bone defects in elderly patients has not been elucidated. Inflammation and the innate immune system, including macrophages, play crucial roles in the differentiation and activation of MSCs. We have developed lentivirus-transduced interleukin 4 (IL4) over-expressing MSCs (IL4-MSCs) to polarize macrophages to an M2 phenotype to promote bone healing in an established young murine critical size bone defect model. In the current study, we explore the potential of IL4-MSCs in aged mice.

METHODS

A 2 mm femoral diaphyseal bone defect was created and fixed with an external fixation device in 15- to 17-month-old male and female BALB/c mice. Microribbon (µRB) scaffolds (Sc) with or without encapsulation of MSCs were implanted in the defect sites. Accordingly, the mice were divided into three treatment groups: Sc-only, Sc + MSCs, and Sc + IL4-MSCs. Mice were euthanized six weeks after the surgery; subsequently, MicroCT (µCT), histochemical and immunohistochemical analyses were performed.

RESULTS

µCT analysis revealed that bone formation was markedly enhanced in the IL4-MSC group. Compared with the Sc-only, the amount of new bone increased in the Sc + MSCs and Sc + IL4-MSC groups. However, no bridging of bone was observed in all groups. H&E staining showed fibrous tissue within the defect in all groups. Alkaline phosphatase (ALP) staining was increased in the Sc + IL4-MSC group. The Sc + IL4-MSCs group showed a decrease in the number of M1 macrophages and an increase in the number of M2 macrophages, with a significant increase in the M2/M1 ratio.

DISCUSSION

IL4 promotes macrophage polarization to an M2 phenotype, facilitating osteogenesis and vasculogenesis. The addition of IL4-MSCs in the µRB scaffold polarized macrophages to an M2 phenotype and increased bone formation; however, complete bone bridging was not observed in any specimens. These results suggest that IL4-MSCs are insufficient to heal a critical size bone defect in aged mice, as opposed to younger animals. Additional therapeutic strategies are needed in this challenging clinical scenario.

Efficacy and safety of ivermectin for the treatment of COVID-19: a systematic review and meta-analysis

BACKGROUND

Ivermectin became a popular choice for COVID-19 treatment among clinicians and the public following encouraging results from pre-print trials and in vitro studies. Early reviews recommended the use of ivermectin based largely on non-peer-reviewed evidence, which may not be robust. This systematic review and meta-analysis assessed the efficacy and safety of ivermectin for treating COVID-19 based on peer-reviewed randomized controlled trials (RCTs) and observational studies (OSs).

METHODS

MEDLINE, EMBASE and PubMed were searched from 1 January 2020 to 1 September 2021 for relevant studies. Outcomes included time to viral clearance, duration of hospitalization, mortality, incidence of mechanical ventilation and incidence of adverse events. RoB2 and ROBINS-I were used to assess risk of bias. Random-effects meta-analyses were conducted. GRADE was used to evaluate quality of evidence.

RESULTS

Three OSs and 14 RCTs were included in the review. Most RCTs were rated as having some concerns in regards to risk of bias, while OSs were mainly rated as having a moderate risk of bias. Based on meta-analysis of RCTs, the use of ivermectin was not associated with reduction in time to viral clearance, duration of hospitalization, incidence of mortality and incidence of mechanical ventilation. Ivermectin did not significantly increase incidence of adverse events. Meta-analysis of OSs agrees with findings from RCT studies.

CONCLUSIONS

Based on very low to moderate quality of evidence, ivermectin was not efficacious at managing COVID-19. Its safety profile permits its use in trial settings to further clarify its role in COVID-19 treatment.

PROTOCOL REGISTRATION

The review was prospectively registered in PROSPERO (CRD42021275302).

Sex Differences in Mesenchymal Stem Cell Therapy With Gelatin-Based Microribbon Hydrogels in a Murine Long Bone Critical-Size Defect Model

Mesenchymal stem cell (MSC)-based therapy and novel biomaterials are promising strategies for healing of long bone critical size defects. Interleukin-4 (IL-4) over-expressing MSCs within a gelatin microribbon (µRB) scaffold was previously shown to enhance the bridging of bone within a critical size femoral bone defect in male Balb/c mice. Whether sex differences affect the healing of this bone defect in conjunction with different treatments is unknown. In this study, we generated 2-mm critical-sized femoral diaphyseal bone defects in 10–12-week-old female and male Balb/c mice. Scaffolds without cells and with unmodified MSCs were implanted immediately after the primary surgery that created the bone defect; scaffolds with IL-4 over-expressing MSCs were implanted 3 days after the primary surgery, to avoid the adverse effects of IL-4 on the initial inflammatory phase of fracture healing. Mice were euthanized 6 weeks after the primary surgery and femurs were collected. MicroCT (µCT), histochemical and immunohistochemical analyses were subsequently performed of the defect site. µRB scaffolds with IL-4 over-expressing MSCs enhanced bone healing in both female and male mice. Male mice showed higher measures of bone bridging and increased alkaline phosphatase (ALP) positive areas, total macrophages and M2 macrophages compared with female mice after receiving scaffolds with IL-4 over-expressing MSCs. Female mice showed higher Tartrate-Resistant Acid Phosphatase (TRAP) positive osteoclast numbers compared with male mice. These results demonstrated that sex differences should be considered during the application of MSC-based studies of bone healing.

Mesenchymal Stem Cells and NF-κB Sensing Interleukin-4 Over-Expressing Mesenchymal Stem Cells Are Equally Effective in Mitigating Particle-Associated Chronic Inflammatory Bone Loss in Mice

Wear particles from total joint arthroplasties (TJAs) induce chronic inflammation, macrophage infiltration and lead to bone loss by promoting bone destruction and inhibiting bone formation. Inhibition of particle-associated chronic inflammation and the associated bone loss is critical to the success and survivorship of TJAs. The purpose of this study is to test the hypothesis that polyethylene particle induced chronic inflammatory bone loss could be suppressed by local injection of NF-κB sensing Interleukin-4 (IL-4) over-expressing MSCs using the murine continuous polyethylene particle infusion model. The animal model was generated with continuous infusion of polyethylene particles into the intramedullary space of the femur for 6 weeks. Cells were locally injected into the intramedullary space 3 weeks after the primary surgery. Femurs were collected 6 weeks after the primary surgery. Micro-computational tomography (μCT), histochemical and immunohistochemical analyses were performed. Particle-infusion resulted in a prolonged pro-inflammatory M1 macrophage dominated phenotype and a decrease of the anti-inflammatory M2 macrophage phenotype, an increase in TRAP positive osteoclasts, and lower alkaline phosphatase staining area and bone mineral density, indicating chronic particle-associated inflammatory bone loss. Local injection of MSCs or NF-κB sensing IL-4 over-expressing MSCs reversed the particle-associated chronic inflammatory bone loss and facilitated bone healing. These results demonstrated that local inflammatory bone loss can be effectively modulated via MSC-based treatments, which could be an efficacious therapeutic strategy for periprosthetic osteolysis.

Suppression of NF-κB-induced chronic inflammation mitigates inflammatory osteolysis in the murine continuous polyethylene particle infusion model

Wear particle-associated bone loss (periprosthetic osteolysis) constrains the longevity of total joint arthroplasty (TJA). Wear particles induce a prolonged upregulation of nuclear factor kappa B (NF-κB) signaling in macrophages and osteoclasts. Synthetic double-stranded oligodeoxynucleotides (ODNs) can prevent the binding of NF-κB to the promoter regions of targeted genes and inhibit genetic activation. We tested the hypothesis that polyethylene-particle induced chronic inflammatory bone loss could be suppressed by local delivery of NF-κB decoy ODNs in murine in vivo model. Polyethylene particles were continuously infused into the medullary cavity of the distal femur for 6 weeks to induce chronic inflammation, and micro-computational tomography and immunohistochemical analysis were performed. Particle-induced chronic inflammation resulted in lower BMD values, an increase in osteoclastogenesis and nuclear translocation of p65, a prolonged M1 pro-inflammatory macrophage phenotype, and a decrease of M2 anti-inflammatory macrophage phenotype. Delayed timing of local infusion of NF-κB decoy ODN for the last 3 weeks reversed polyethylene-particle associated chronic inflammatory bone loss and facilitated bone healing. This study demonstrated that polyethylene-particle associated chronic inflammatory osteolysis can be effectively modulated via interference with the NF-κB pathway; this minimally invasive intervention could potentially be an efficacious therapeutic strategy for periprosthetic osteolysis after TJA.

Enhancing titre and production stability of paenibacillin from Paenibacillus polymyxa by sequential drug resistance screening

AIMS

Paenibacillin is a naturally biosynthesized antimicrobial lantibiotic peptide which is produced by wild-type Paenibacillus polymyxa OSY-DF in low but detectable levels. The aim was to increase paenibacillin titre and production consistency through sequential drug resistance screening.

METHODS AND RESULTS

Spontaneous mutants of P. polymyxa OSY-DF were isolated by subjecting the bacterium to two rounds of screening for resistance to rifampicin, which targets RNA polymerase, and gentamicin, which targets ribosomes. Changes in antimicrobial production of the mutants were monitored using a bioassay method. A spontaneous mutant, P. polymyxa OSY-EC, capable of producing high paenibacillin titre, was selected and compared phenotypically to the wild-type strain. The mutant was found to produce paenibacillin at five-fold higher titre than the wild type. The mutant constantly produced paenibacillin while the wild type produced the antimicrobial agent variably. Fourier transformation mid-infrared spectroscopy revealed an interclass distance of 6·4 between the wild type and the mutant strain, suggesting significant phenotypic change during the mutation.

CONCLUSIONS

P. polymyxa OSY-EC, a spontaneous mutant capable of consistent production of high paenibacillin titre, was isolated from the wild type after sequential screening on rationally selected antibiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study will help make paenibacillin available for large-scale testing by interested researchers and industries seeking applications that improve food safety and quality.

Different Effects of Intramedullary Injection of Mesenchymal Stem Cells During the Acute vs. Chronic Inflammatory Phase on Bone Healing in the Murine Continuous Polyethylene Particle Infusion Model

Chronic inflammation is a common feature in many diseases of different organ systems, including bone. However, there are few interventions to mitigate chronic inflammation and preserve host tissue. Previous in vitro studies demonstrated that preconditioning of mesenchymal stem cells (pMSCs) using lipopolysaccharide and tumor necrosis factor-α polarized macrophages from a pro-inflammatory to an anti-inflammatory phenotype and increased osteogenesis compared to unaltered MSCs. In the current study, we investigated the local injection of MSCs or pMSCs during the acute versus chronic inflammatory phase in a murine model of inflammation of bone: the continuous femoral intramedullary polyethylene particle infusion model. Chronic inflammation due to contaminated polyethylene particles decreased bone mineral density and increased osteoclast-like cells positively stained with leukocyte tartrate resistant acid phosphatase (TRAP) staining, and resulted in a sustained M1 pro-inflammatory macrophage phenotype and a decreased M2 anti-inflammatory phenotype. Local injection of MSCs or pMSCs during the chronic inflammatory phase reversed these findings. Conversely, immediate local injection of pMSCs during the acute inflammatory phase impaired bone healing, probably by mitigating the mandatory acute inflammatory reaction. These results suggest that the timing of interventions to facilitate bone healing by modulating inflammation is critical to the outcome. Interventions to facilitate bone healing by modulating acute inflammation should be prudently applied, as this phase of bone healing is temporally sensitive. Alternatively, local injection of MSCs or pMSCs during the chronic inflammatory phase may be a potential intervention to mitigate the adverse effects of contaminated particles on bone.

PDGF-BB and IL-4 co-overexpression is a potential strategy to enhance mesenchymal stem cell-based bone regeneration

BACKGROUND

Mesenchymal stem cell (MSC)-based therapy has the potential for immunomodulation and enhancement of tissue regeneration. Genetically modified MSCs that over-express specific cytokines, growth factors, or chemokines have shown great promise in pre-clinical studies. In this regard, the anti-inflammatory cytokine interleukin (IL)-4 converts pro-inflammatory M1 macrophages into an anti-inflammatory M2 phenotype; M2 macrophages mitigate chronic inflammation and enhance osteogenesis by MSC lineage cells. However, exposure to IL-4 prematurely inhibits osteogenesis of MSCs in vitro; furthermore, IL-4 overexpressing MSCs inhibit osteogenesis in vivo during the acute inflammatory period. Platelet-derived growth factor (PDGF)-BB has been shown to enhance osteogenesis of MSCs with a dose-dependent effect.

METHODS

In this study, we generated a lentiviral vector that produces PDGF-BB under a weak promoter (phosphoglycerate kinase, PGK) and lentiviral vector producing IL-4 under a strong promoter (cytomegalovirus, CMV). We infected MSCs with PDGF-BB and IL-4-producing lentiviral vectors separately or in combination to investigate cell proliferation and viability, protein expression, and the capability for osteogenesis.

RESULTS

PDGF-BB and IL-4 co-overexpression was observed in the co-infected MSCs and shown to enhance cell proliferation and viability, and osteogenesis compared to IL-4 overexpressing MSCs alone.

CONCLUSIONS

Overexpression of PDGF-BB together with IL-4 mitigates the inhibitory effect of IL-4 on osteogenesis by IL-4 overexpressing MSCS. PDGF-BB and IL-4 overexpressing MSCs may be a potential strategy to facilitate osteogenesis in scenarios of both acute and chronic inflammation.

A method of assessing essential amino acid availability from microbial and ruminally undegraded protein in lactating dairy cows

The objective of this study was to extend a stable isotope-based assessment of AA absorption from rumen-degradable protein (RDP) sources to include determination of essential AA (EAA) availability from microbial protein (MCP). To demonstrate the technique, a study using a 2 × 2 factorial arrangement of treatments applied in a repeated 4 × 4 Latin square design was undertaken. Factors were high and low rumen-degradable protein and high and low starch. Twelve lactating cows were blocked into 3 groups according to days in milk and randomly assigned to the 4 treatment sequences. Each period was 14 d in length with 10 d of adaption followed by 4 d of ruminal infusions of ¹⁵N-labeled ammonium sulfate. On the last day of each period, a ¹³C-labeled AA mixture was infused into the jugular vein over a 6-h period to assess total AA entry. Rumen, blood, urine, and milk samples were collected during the infusions. Ruminal bacteria and blood samples were assessed for AA enrichment. Total plasma AA absorption rates were derived for 6 EAA from plasma ¹³C AA enrichment. Absorption of 6 EAA from MCP was calculated from total AA absorption based on ¹⁵N enrichment in blood and rumen bacteria. Essential AA absorption rates from total protein, MCP, and rumen-undegradable protein were derived with standard errors of the mean of 6, 14, and 14%, respectively. An average of 45% of absorbed EAA were from MCP, which varied among 6 EAA and was interactively affected by starch and RDP in diets. Microbial AA availability measured by isotope dilution method increased with the high RDP diets and was unaffected by starch level, except for Met, which decreased with high starch. Microbial protein outflow, estimated from urinary purine derivatives, increased with RDP and was not significantly affected by starch. This was consistent with measurements from the isotope dilution method. Total AA absorption rates measured from isotope dilution were similar to estimates from CNCPS (v. 6.55), but a lower proportion of absorbed AA was derived from MCP for the former method. Compared with the isotope and CNCPS estimates, the Fleming model underestimated microbial EAA and total EAA availability. An average of 58% of the absorbed EAA was converted into milk, which varied among individual AA and was interactively affected by starch and RDP in diets. The isotope dilution approach is advantageous because it provides estimates of EAA availability for individual EAA from rumen-undegradable protein and MCP directly with fewer errors of measurement than can be achieved with intestinal disappearance methods.

Interleukin-4 overexpressing mesenchymal stem cells within gelatin-based microribbon hydrogels enhance bone healing in a murine long bone critical-size defect model

Mesenchymal stem cell (MSC)-based therapy is a promising strategy for bone repair. Furthermore, the innate immune system, and specifically macrophages, plays a crucial role in the differentiation and activation of MSCs. The anti-inflammatory cytokine Interleukin-4 (IL-4) converts pro-inflammatory M1 macrophages into a tissue regenerative M2 phenotype, which enhances MSC differentiation and function. We developed lentivirus-transduced IL-4 overexpressing MSCs (IL-4 MSCs) that continuously produce IL-4 and polarize macrophages toward an M2 phenotype. In the current study, we investigated the potential of IL-4 MSCs delivered using a macroporous gelatin-based microribbon (μRB) scaffold for healing of critical-size long bone defects in Mice. IL-4 MSCs within μRBs enhanced M2 marker expression without inhibiting M1 marker expression in the early phase, and increased macrophage migration into the scaffold. Six weeks after establishing the bone defect, IL-4 MSCs within μRBs enhanced bone formation and helped bridge the long bone defect. IL-4 MSCs delivered using macroporous μRB scaffold is potentially a valuable strategy for the treatment of critical-size long bone defects.

Quantitative mitochondrial DNA copy number determination using droplet digital PCR with single-cell resolution

Mitochondria are involved in a number of diverse cellular functions, including energy production, metabolic regulation, apoptosis, calcium homeostasis, cell proliferation, and motility, as well as free radical generation. Mitochondrial DNA (mtDNA) is present at hundreds to thousands of copies per cell in a tissue-specific manner. mtDNA copy number also varies during aging and disease progression and therefore might be considered as a biomarker that mirrors alterations within the human body. Here, we present a new quantitative, highly sensitive droplet digital PCR (ddPCR) method, droplet digital mitochondrial DNA measurement (ddMDM), to measure mtDNA copy number not only from cell populations but also from single cells. Our developed assay can generate data in as little as 3 h, is optimized for 96-well plates, and also allows the direct use of cell lysates without the need for DNA purification or nuclear reference genes. We show that ddMDM is able to detect differences between samples whose mtDNA copy number was close enough as to be indistinguishable by other commonly used mtDNA quantitation methods. By utilizing ddMDM, we show quantitative changes in mtDNA content per cell across a wide variety of physiological contexts including cancer progression, cell cycle progression, human T cell activation, and human aging.

Online Learning of Gait Models From Older Adult Data

This paper proposes a novel approach for online, individualized gait analysis, based on an adaptive periodic model of any gait signal. The proposed method learns a model of the gait cycle during online measurement, using a continuous representation that can adapt to inter- and intra-personal variability by creating an individualized model. Once the algorithm has converged to the input signal, key gait events can be identified based on the estimated gait phase and amplitude. The approach is implemented and tested on retirement home resident 6 min walk (6MW) data using wearable accelerometers at the ankle. The proposed approach converges within approximately four gait cycles and achieves 3% error in detecting initial swing events.11 An early version of this work was presented in [1]. A more extensive description of related work and an extended method, including optimization of learning rates, were added to this paper. Further, this paper applies and evaluates the method to a new and much larger gait dataset taken from older adults who each have a variety of medical conditions. Therefore, the experimental protocol was also updated and the results are entirely novel.

Abstract P1-08-05: Type 2 diabetes and survival outcomes among a multi-ethnic cohort of breast cancer patients

BACKGROUND: With increasing prevalence of type 2 diabetes, it has become one of the common comorbidities among breast cancer patients. Few contemporary studies have examined the effect of preexisting diabetes on survival outcomes in breast cancer patients. Furthermore, both breast cancer mortality and diabetes prevalence are higher in African American women compared to Caucasian women, yet data on whether diabetes can explain racial disparity in breast cancer mortality is scarce.

OBJECTIVE: To compare clinopathological characteristics and survival outcomes between breast cancer patients with and without co-existing diabetes, and to explore the contribution of diabetes to breast cancer survival differences between African Americans and Caucasians.

METHODS: We analyzed data from the Chicago Multiethnic Epidemiologic Breast Cancer Cohort (ChiMEC) comprising of 3170 histologically confirmed breast cancer patients diagnosed between 2004 and 2017. The cohort consists of 55% Caucasians, 38% African Americans, and 7% other ethnicities. Cox models were used to analyze data on several clinical outcomes.

Table 1 Unadjusted HR (95% CI)pAdjusted HR (95% CI)*pAll-cause mortality2.20 (1.65-2.92)<0.0011.79 (1.33-2.43<0.001Breast Cancer-specific mortality1.61 (1.06-2.44)0.0251.97 (1.27-3.05)0.002Non-breast cancer mortality3.14 (2.11-4.69)<0.0011.62 (1.06-2.47)0.025Time to recurrence1.18 (0.76-1.85)0.461.41 (0.89-2.25)0.15Recurrence-free survival1.73 (1.32-2.26)<0.0011.68 (1.27-2.22)<0.001*Adjusted for age, race, stage, hormone therapy, and chemotherapy

RESULTS: 245 patients (8%) in the cohort had co-existing diabetes at time of breast cancer diagnosis, with African Americans having highest prevalence (14%). Patients with diabetes were older (mean 66 vs. 56 years old) and had higher proportion of obesity (67% vs. 34%) and Charlson comorbidity index >2 (27% vs. 10%) than those without diabetes. The two groups were similar in terms of surgery, radiation, and hormonal therapy received, while patients with diabetes had slightly more advanced stage (15% vs. 10%). After adjusting for multiple prognostic factors, patients with diabetes had a 97% higher risk of dying from breast cancer and a 62% fold higher risk dying from other causes than patients without diabetes (Table). The two groups had no significant difference in risk of recurrence. In addition, the hazard ratio (HR) comparing African Americans with Caucasians was 2.35 (95% confidence interval [CI] 1.90-2.91), and it changed to 2.19 (95% CI 1.76-2.33) after the adjustment for diabetes.

CONCLUSIONS: Pre-existing diabetes among breast cancer patients was associated with higher risk of breast cancer specific and all-cause mortality. About 11% of racial disparities in breast cancer mortality could be attributed to higher difference in diabetes prevalence in African American patients. Further research investigating how pre-existing diabetes may influence breast cancer treatment and survival are warranted.

Citation Format: Neerukonda AR, Olopade OI, Huang E, Huo D. Type 2 diabetes and survival outcomes among a multi-ethnic cohort of breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-05.

Telomere length and telomerase activity in T cells are biomarkers of high-performing centenarians

It is generally recognized that the function of the immune system declines with increased age and one of the major immune changes is impaired T-cell responses upon antigen presentation/stimulation. Some "high-performing" centenarians (100+ years old) are remarkably successful in escaping, or largely postponing, major age-related diseases. However, the majority of centenarians ("low-performing") have experienced these pathologies and are forced to reside in long-term nursing facilities. Previous studies have pooled all centenarians examining heterogeneous populations of resting/unstimulated peripheral blood mononuclear cells (PBMCs). T cells represent around 60% of PBMC and are in a quiescence state when unstimulated. However, upon stimulation, T cells rapidly divide and exhibit dramatic changes in gene expression. We have compared stimulated T-cell responses and identified a set of transcripts expressed in vitro that are dramatically different in high- vs. low-performing centenarians. We have also identified several other measurements that are different between high- and low-performing centenarians: (a) The amount of proliferation following in vitro stimulation is dramatically greater in high-performing centenarians compared to 67- to 83-year-old controls and low-performing centenarians; (b) telomere length is greater in the high-performing centenarians; and (c) telomerase activity following stimulation is greater in the high-performing centenarians. In addition, we have validated a number of genes whose expression is directly related to telomere length and these are potential fundamental biomarkers of aging that may influence the risk and progression of multiple aging conditions.

A method for measuring the distribution of the shortest telomeres in cells and tissues

Improved methods to measure the shortest (not just average) telomere lengths (TLs) are needed. We developed Telomere Shortest Length Assay (TeSLA), a technique that detects telomeres from all chromosome ends from <1 kb to 18 kb using small amounts of input DNA. TeSLA improves the specificity and efficiency of TL measurements that is facilitated by user friendly image-processing software to automatically detect and annotate band sizes, calculate average TL, as well as the percent of the shortest telomeres. Compared with other TL measurement methods, TeSLA provides more information about the shortest telomeres. The length of telomeres was measured longitudinally in peripheral blood mononuclear cells during human aging, in tissues during colon cancer progression, in telomere-related diseases such as idiopathic pulmonary fibrosis, as well as in mice and other organisms. The results indicate that TeSLA is a robust method that provides a better understanding of the shortest length of telomeres.

Short telomeres are a hallmark of senescence and can result in genomic instability as well as cancer progression. Here, the authors present TeSLA, a technique to accurately detect telomeres under 1 kb in length.

Radiocarbon constraints on the glacial ocean circulation and its impact on atmospheric CO2

While the ocean’s large-scale overturning circulation is thought to have been significantly different under the climatic conditions of the Last Glacial Maximum (LGM), the exact nature of the glacial circulation and its implications for global carbon cycling continue to be debated. Here we use a global array of ocean–atmosphere radiocarbon disequilibrium estimates to demonstrate a ∼689±53 ¹⁴C-yr increase in the average residence time of carbon in the deep ocean at the LGM. A predominantly southern-sourced abyssal overturning limb that was more isolated from its shallower northern counterparts is interpreted to have extended from the Southern Ocean, producing a widespread radiocarbon age maximum at mid-depths and depriving the deep ocean of a fast escape route for accumulating respired carbon. While the exact magnitude of the resulting carbon cycle impacts remains to be confirmed, the radiocarbon data suggest an increase in the efficiency of the biological carbon pump that could have accounted for as much as half of the glacial–interglacial CO₂ change.

Establishing the efficiency of the biological carbon pump is needed to constrain the impact of ocean circulation on the carbon cycle. Here, the authors compile a global array of ocean–atmosphere radiocarbon disequilibrium estimates and evaluate the strength of the carbon pump over the last glacial maximum.

Increased Frequency of BK Virus-Specific Polyfunctional CD8+ T Cells Predict Successful Control of BK Viremia After Kidney Transplantation

BACKGROUND

BK virus infection remains an important cause of loss of allograft function after kidney transplantation. We sought to determine whether polyfunctional T cells secreting multiple cytokines simultaneously, which have been shown to be associated with viral control, could be detected early after start of BK viremia, which would provide insight into the mechanism of successful antiviral control.

METHODS

Peripheral blood mononuclear cells collected during episodes of BK viral replication were evaluated by multiparameter flow cytometry after stimulation by overlapping peptide pools of BK virus antigen to determine frequency of CD8+ and CD4+ T cells expressing 1 or more cytokines simultaneously, as well as markers of T-cell activation, exhaustion, and maturation.

RESULTS

BK virus controllers, defined as those with episodes of BK viremia of 3 months or less, had an 11-fold increase in frequency of CD8+ polyfunctional T cells expressing multiple cytokines, as compared with patients with prolonged episodes of BK viremia. Patients with only low level BK viremia expressed low frequencies of polyfunctional T cells. Polyfunctional T cells were predominantly of the effector memory maturation subtype and expressed the cytotoxicity marker CD107a.

CONCLUSIONS

Noninvasive techniques for immune assessment of peripheral blood can provide insight into the mechanism of control of BK virus replication and may allow for future patient risk stratification and customization of immune suppression at the onset of BK viremia.

Application of Hyperbranched Block Copolymers as Templates for the Generation of Nanoporous Organosilicates

A general route to organic–inorganic hybrids with nanophase morphologies has been elaborated with the objective of ultimately generating nanoporosity in organosilicates. Hyperbranched block copolymers prepared by either the sequential or concurrent polymerization of an ABC monomer ( γ-( ∊-caprolactone) 2-bromo-2-dimethylpropionate) with a BCD monomer (2-hydroxyethyl methacrylate) were used as the macromolecular templates. The two monomers, each polymerizing by different chemistries, for example ring-opening polymerization and atom transfer radical polymerization, bear initiating centres that are targeted for the functionality located on the accompanying monomer. Consequentially, a branched polymer is obtained which avoids the traditional multistep procedures. The branching density was altered simply by the addition of the appropriate AB ( ∊-caprolactone) and/or CD (methyl methacrylate) comonomers. These polymers were readily soluble initially in the organosilicate prepolymer (methyl silsesquioxane), however, upon the onset of crosslinking, both the solubility parameters and molecular weight of the organosilicate (polymethylsilsesquioxane) change, causing the hyperbranched polymer to phase separate by a nucleation and growth process. The organic polymer was selectively removed by thermolysis, producing a nanoporous inorganic structure. The size and shape of the pores are identical to those of the initial hybrid morphology. A significant reduction in the dielectric constant was achieved by simply replacing a portion of the glass matrix with air, which has a dielectric constant of 1.0.

Perifosine as a potential novel anti-telomerase therapy

Most tumors circumvent telomere-length imposed replicative limits through expression of telomerase, the reverse transcriptase that maintains telomere length. Substantial evidence that AKT activity is required for telomerase activity exists, indicating that AKT inhibitors may also function as telomerase inhibitors. This possibility has not been investigated in a clinical context despite many clinical trials evaluating AKT inhibitors. We tested if Perifosine, an AKT inhibitor in clinical trials, inhibits telomerase activity and telomere maintenance in tissue culture and orthotopic xenograft models as well as in purified CLL samples from a phase II Perifosine clinical trial. We demonstrate that Perifosine inhibits telomerase activity and induces telomere shortening in a wide variety of cell lines in vitro, though there is substantial heterogeneity in long-term responses to Perifosine between cell lines. Perifosine did reduce primary breast cancer orthotopic xenograft tumor size, but did not impact metastatic burden in a statistically significant manner. However, Perifosine reduced telomerase activity in four of six CLL patients evaluated. Two of the patients were treated for four to six months and shortening of the shortest telomeres occurred in both patients' cells. These results indicate that it may be possible to repurpose Perifosine or other AKT pathway inhibitors as a novel approach to targeting telomerase.