IGF Binding Protein-5 Induces Cell Senescence

A Single-Short Partial Reprogramming of the Endothelial Cells decreases Blood Pressure via attenuation of EndMT in Hypertensive Mice

Background

Small artery remodeling and endothelial dysfunction are hallmarks of hypertension. Growing evidence supports a likely causal association between cardiovascular diseases and the presence of endothelial-to-mesenchymal transition (EndMT), a cellular transdifferentiation process in which endothelial cells (ECs) partially lose their identity and acquire additional mesenchymal phenotypes. EC reprogramming represents an innovative strategy in regenerative medicine to prevent deleterious effects induced by cardiovascular diseases.

Methods

Using a partial reprogramming of ECs, via overexpression of Oct-3/4, Sox-2, and Klf-4 (OSK) transcription factors, we aimed to bring ECs back to a youthful phenotype in hypertensive mice. Primary ECs were infected with lentiviral vectors (LV) containing the specific EC marker cadherin 5 (Cdh5) and the fluorescent reporter enhanced green fluorescence protein (EGFP) with empty vector (LVCO) or with OSK (LV-OSK). Confocal microscopy and western blotting analysis were used to confirm the OSK overexpression. Cellular migration, senescence, and apoptosis were evaluated. Human aortic ECs (HAoECs) from male and female normotensive and hypertensive patients were analyzed after OSK or control treatments for their endothelial nitric oxide synthase (eNOS) levels, nitric oxide (NO), and genetic profile. Male and female normotensive (BPN/3J) and hypertensive (BPH/2J) mice were treated with an intravenous (i.v.) injection of LVCO or LV-OSK and evaluated 10 days post-infection. The blood pressure, cardiac function, vascular reactivity of small arteries, in vivo EGFP signal and EndMT inhibition were analyzed.

Results

OSK overexpression induced partial EC reprogramming in vitro , and these cells showed endothelial progenitor cell (EPC)-like features with lower migratory capability. OSK treatment of hypertensive BPH/2J mice normalized blood pressure and resistance arteries hypercontractility, via the attenuation of EndMT and elastin breaks. EGFP signal was detected in vivo in the prefrontal cortex of both BPN/3J and BPH/2J-treated mice, but OSK induced angiogenesis only in male BPN/3J mice. OSK-treated human ECs from hypertensive patients showed high eNOS activation and NO production, with low ROS formation. Single-cell RNA analysis showed that OSK alleviated EC senescence and EndMT, restoring their phenotypes in human ECs from hypertensive patients.

Conclusion

Overall, these data indicate that OSK treatment and EC reprogramming can decrease blood pressure and reverse hypertension-induced vascular damage.

Cellular senescence in cancer: molecular mechanisms and therapeutic targets

Aging exhibits several hallmarks in common with cancer, such as cellular senescence, dysbiosis, inflammation, genomic instability, and epigenetic changes. In recent decades, research into the role of cellular senescence on tumor progression has received widespread attention. While how senescence limits the course of cancer is well established, senescence has also been found to promote certain malignant phenotypes. The tumor-promoting effect of senescence is mainly elicited by a senescence-associated secretory phenotype, which facilitates the interaction of senescent tumor cells with their surroundings. Targeting senescent cells therefore offers a promising technique for cancer therapy. Drugs that pharmacologically restore the normal function of senescent cells or eliminate them would assist in reestablishing homeostasis of cell signaling. Here, we describe cell senescence, its occurrence, phenotype, and impact on tumor biology. A "one-two-punch" therapeutic strategy in which cancer cell senescence is first induced, followed by the use of senotherapeutics for eliminating the senescent cells is introduced. The advances in the application of senotherapeutics for targeting senescent cells to assist cancer treatment are outlined, with an emphasis on drug categories, and the strategies for their screening, design, and efficient targeting. This work will foster a thorough comprehension and encourage additional research within this field.

IGFBP5 Promotes Neuronal Apoptosis in a 6-OHDA-Toxicant Model of Parkinson's Disease by Inhibiting the Sonic Hedgehog Signaling Pathway

INTRODUCTION

Parkinson's disease (PD) is the most common neurodegenerative disease worldwide. Studies have shown that insulin-like growth factor-binding protein 5 (IGFBP5) may contribute to methamphetamine-induced neurotoxicity and neuronal apoptosis in PC-12 cells and rat striatum. Here, we studied the expression and role of IGFBP5 in the 6-OHDA-toxicant model of PD.

METHODS

PC-12 and SH-SY5Y cells were exposed to 50 μm 6-OHDA for 24 h. qRT-PCR, western blotting, CCK-8 assay, EdU staining, annexin V staining, and immunofluorescence were performed to study the effects of IGFBP5-specific siRNAs. The effects of IGFBP5 on a rat 6-OHDA model of PD were confirmed by performing behavioral tests, tyrosine hydroxylase (TH) immunofluorescence staining, and western blotting.

RESULTS

In the GSE7621 dataset, IGFBP5 was highly expressed in the substantia nigra tissues of PD patients compared to healthy controls. In PC-12 and SH-SY5Y cells, IGFBP5 was upregulated following 6-OHDA exposure in a dose-dependent manner. Silencing of IGFBP5 promoted PC-12 and SH-SY5Y proliferation and inhibited apoptosis under 6-OHDA stimulation. Silencing of IGFBP5 relieved 6-OHDA-induced TH-positive neuron loss. Hedgehog signaling pathway was predicted as a downstream signaling pathway of IGFBP5. Negative regulation between IGFBP5 and sonic hedgehog (SHH) signaling pathway was confirmed in vitro. The effects of IGFBP5 silencing on SH-SY5Y cells were partially reversed using cyclopamine, a direct inhibitor of the SHH signaling pathway. In addition, silencing of IGFBP5 attenuated motor deficits and neuronal damage in 6-OHDA-induced PD rats.

CONCLUSION

Elevated IGFBP5 expression may be involved in 6-OHDA-induced neurotoxicity through regulation of the SHH signaling pathway.

Immunoengineering Biomaterials for Musculoskeletal Tissue Repair across Lifespan

Musculoskeletal diseases and injuries are among the leading causes of pain and morbidity worldwide. Broad efforts have focused on developing pro-regenerative biomaterials to treat musculoskeletal conditions; however, these approaches have yet to make a significant clinical impact. Recent studies have demonstrated that the immune system is central in orchestrating tissue repair and that targeting pro-regenerative immune responses can improve biomaterial therapeutic outcomes. However, aging is a critical factor negatively affecting musculoskeletal tissue repair and immune function. Hence, understanding how age affects the response to biomaterials is essential for improving musculoskeletal biomaterial therapies. This review focuses on the intersection of the immune system and aging in response to biomaterials for musculoskeletal tissue repair. The article introduces the general impacts of aging on tissue physiology, the immune system, and the response to biomaterials. Then, it explains how the adaptive immune system guides the response to injury and biomaterial implants in cartilage, muscle, and bone and discusses how aging impacts these processes in each tissue type. The review concludes by highlighting future directions for the development and translation of personalized immunomodulatory biomaterials for musculoskeletal tissue repair.

Insulin-like growth factor binding protein 5 accelerate the senescence of periodontal ligament stem cells

Evidences have showed stem cell mediated tissue regeneration is a promising method for the treatment of periodontitis. Insulin-like growth factor binding proteins-5 (IGFBP5) is a member of the insulin growth factor (IGFs) family and plays a regulatory role in cell proliferation and differentiation. Our previous study showed that IGFBP5 can promote osteogenic differentiation of periodontal ligament stem cells (PDLSCs) and enhance periodontal tissue regeneration mediated by PDLSCs. However, the function of IGFBP5 in the process of PDLSCs senescence remains unclear. The present study showed IGFBP5 mRNA level was highly expressed in passage-induced aged PDLSCs cells. IGFBP5 knockdown decreased the ratio of senescence associated β-galactosidase (SA-β-Gal) positive cells, enhanced the activity of TERT, and down-regulated the expression levels of P16, P21, P53 mRNA and protein. Overexpression of IGFBP5 increased the ratio of SA-β-Gal positive staining PDLSCs, decreased the activity of telomerase TERT, and up-regulated the expression levels of P16, P21, P53 mRNA and protein related to PDLSCs senescence. In conclusion, IGFBP5 can accelerate the senescence of PDLSCs, indicating the potential target for maintaining the "young state" of stem cells.

Heterogenous Differences in Cellular Senescent Phenotypes in Pre-Eclampsia and IUGR following Quantitative Assessment of Multiple Biomarkers of Senescence

Premature ageing of the placenta in pregnancy outcomes is associated with the persistent presence of oxidative stress and placental insufficiency reducing its functional capacity. In this study, we investigated cellular senescence phenotypes of pre-eclampsia and IUGR pregnancies by simultaneously measuring several biomarkers of senescence. Maternal plasma and placental samples were collected at term gestation from nulliparous women undergoing pre-labour elective caesarean section with pre-eclampsia without intrauterine growth restriction (PE; n = 5), pre-eclampsia associated with intrauterine growth restriction (n = 8), intrauterine growth restriction (IUGR < 10th centile; n = 6), and age-matched controls (n = 20). Placental absolute telomere length and senescence gene analysis was performed by RTqPCR. The expression of cyclin-dependent kinase inhibitors (p21 and p16) was determined by Western blot. Senescence-associated secretory phenotypes (SASPs) were evaluated in maternal plasma by multiplex ELISA assay. Placental expression of senescence-associated genes showed significant increases in CHEK1, PCNA, PTEN, CDKN2A, and CCNB-1 (p < 0.05) in pre-eclampsia, while TBX-2, PCNA, ATM, and CCNB-1 expression were evident (p < 0.05) and were significantly decreased in IUGR compared with controls. Placental p16 protein expression was significantly decreased in pre-eclampsia only compared with controls (p = 0.028). IL-6 was significantly increased in pre-eclampsia (0.54 pg/mL ± 0.271 vs. 0.3 pg/mL ± 0.102; p = 0.017) while IFN-γ was significantly increased in IUGR (4.6 pg/mL ± 2.2 vs. 2.17 pg/mL ± 0.8; p = 0.002) compared with controls. These results provide evidence of premature senescence in IUGR pregnancies, and while cell cycle checkpoint regulators are activated in pre-eclampsia, the cellular phenotype is one of cell repair and subsequent proliferation rather than progression to senescence. The heterogeneity of these cellular phenotypes highlights the complexity of characterising cellular senescence and may equally be indicative of the differing pathophysiological insults unique to each obstetric complication.

A Pro-Regenerative Environment Triggers Premalignant to Malignant Transformation of Senescent Hepatocytes

Unfortunately, available liver cancer treatments are associated with modest survival advantage. The biggest factor improving survival is early detection, but the current understanding of early transformation events is limited. Therefore, we set up a model to study these early events and investigated the relationship of premalignant, senescent hepatocytes, a regenerative environment, and the influence of secreted factors on liver tumorigenesis. Oncogene-induced senescence (OIS) was triggered in a subset of mouse hepatocytes, which under normal conditions, are eliminated by immunosurveillance. Inducing liver damage and regeneration was sufficient to trigger immunosurveillance escape of OIS hepatocytes, resulting in premalignant to malignant transformation and hepatocellular tumor development. Trefoil factor 3 (TFF3) was found to be overexpressed in OIS hepatocytes and in hepatocellular carcinoma. TFF3 deficiency strongly attenuated malignant transformation by increasing insulin-like growth factor binding protein 5 (IGFBP5) expression, which consequently dampened IGF receptor signaling. Furthermore, analysis of precancerous liver tissue validated TFF3 as an early liver cancer biomarker. Altogether, these findings provide mechanistic insights into early transformation and immunosurveillance escape in liver cancer, revealing TFF3 and IGFBP5 to be important players with opposite roles in tumorigenesis.

SIGNIFICANCE

Liver damage induces a compensatory regenerative response that can drive premalignant to malignant transformation of senescent hepatocytes.

Insulin-like growth factor binding protein 5b of Trachinotus ovatus and its heparin-binding motif play a critical role in host antibacterial immune responses via NF-κB pathway

Introduction

Insulin-like growth factor binding protein 5 (IGFBP5) exerts an essential biological role in many processes, including apoptosis, cellular differentiation, growth, and immune responses. However, compared to mammalians, our knowledge of IGFBP5 in teleosts remains limited.

Methods

In this study, TroIGFBP5b, an IGFBP5 homologue from golden pompano (Trachinotus ovatus) was identified. Quantitative real-time PCR (qRT-PCR) was used to check its mRNA expression level in healthy condition and after stimulation. In vivo overexpression and RNAi knockdown method were performed to evaluate the antibacterial profile. We constructed a mutant in which HBM was deleted to better understand the mechanism of its role in antibacterial immunity. Subcellular localization and nuclear translocation were verified by immunoblotting. Further, proliferation of head kidney lymphocytes (HKLs) and phagocytic activity of head kidney macrophages (HKMs) were detected through CCK-8 assay and flow cytometry. Immunofluorescence microscopy assay (IFA) and dual luciferase reporter (DLR) assay were used to evaluate the activity in nuclear factor-κB (NF-κβ) pathway.

Results

The TroIGFBP5b mRNA expression level was upregulated after bacterial stimulation. In vivo, TroIGFBP5b overexpression significantly improved the antibacterial immunity of fish. In contrast, TroIGFBP5b knockdown significantly decreased this ability. Subcellular localization results showed that TroIGFBP5b and TroIGFBP5b-δHBM were both present in the cytoplasm of GPS cells. After stimulation, TroIGFBP5b-δHBM lost the ability to transfer from the cytoplasm to the nucleus. In addition, rTroIGFBP5b promoted the proliferation of HKLs and phagocytosis of HKMs, whereas rTroIGFBP5b-δHBM, suppressed these facilitation effects. Moreover, the in vivo antibacterial ability of TroIGFBP5b was suppressed and the effects of promoting expression of proinflammatory cytokines in immune tissues were nearly lost after HBM deletion. Furthermore, TroIGFBP5b induced NF-κβ promoter activity and promoted nuclear translocation of p65, while these effects were inhibited when the HBM was deleted.

Discussion

Taken together, our results suggest that TroIGFBP5b plays an important role in golden pompano antibacterial immunity and activation of the NF-κβ signalling pathway, providing the first evidence that the HBM of TroIGFBP5b plays a critical role in these processes in teleosts.

Insulin-like growth factor binding protein 5: Diverse roles in cancer

Insulin-like growth factor binding proteins (IGFBPs) and the associated signaling components in the insulin-like growth factor (IGF) pathway regulate cell differentiation, proliferation, apoptosis, and adhesion. Of the IGFBPs, insulin-like growth factor binding protein 5 (IGFBP5) is the most evolutionarily conserved with a dynamic range of IGF-dependent and -independent functions, and studies on the actions of IGFBP5 in cancer have been somewhat paradoxical. In cancer, the IGFBPs respond to external stimuli to modulate disease progression and therapeutic responsiveness in a context specific manner. This review discusses the different roles of IGF signaling and IGFBP5 in disease with an emphasis on discoveries within the last twenty years, which underscore a need to clarify the IGF-independent actions of IGFBP5, the impact of its subcellular localization, the differential activities of each of the subdomains, and the response to elements of the tumor microenvironment (TME). Additionally, recent advances addressing the role of IGFBP5 in resistance to cancer therapeutics will be discussed. A better understanding of the contexts in which IGFBP5 functions will facilitate the discovery of new mechanisms of cancer progression that may lead to novel therapeutic opportunities.

Insulin-like growth factor binding proteins 7 prevents dental pulp-derived mesenchymal stem cell senescence via metabolic downregulation of p21

Cellular senescence affects the efficacy of mesenchymal stem cells (MSCs)-mediated tissue regeneration. Insulin-like growth factor binding proteins-7 (IGFBP7), as a member of the IGF family, is associated with osteogenic differentiation and the senescence of MSCs, but its exact function and mechanism remain unclear. We found IGFBP7 promoted the osteogenic differentiation and prevented the senescence of dental pulp-derived MSCs (DPSCs), as observed in the gain-of-function and loss-of-function analyses, the senescence-associated marker p21 showed the most pronounced expression changes. We demonstrated that IGFBP7 activated the biological activity of SIRT1 deacetylase via metabolism, resulting in a deacetylation of H3K36ac and a decrease of the binding affinity of H3K36ac to p21 promoter, thereby reducing the transcription of p21, which ultimately prevents DPSCs senescence and promotes tissue regeneration. The activation of the mitochondrial electron transport chain (ETC) by Coenzyme Q10 could rescue the promotion of DPSC senescence induced by the knockdown of IGFBP7, whereas the inhibition of ETC by rotenone attenuated the prevention of DPSC senescence induced by IGFBP7 overexpression. In conclusion, our present results reveal a novel function of IGFBP7 in preventing DPSC senescence via the metabolism-induced deacetylation of H3K36ac and reduction of p21 transcription, suggesting that IGFBP7 is a potential target for promoting tissue regeneration in an aging environment.

Long-Term IGF1 Stimulation Leads to Cellular Senescence via Functional Interaction with the Thioredoxin-Interacting Protein, TXNIP

The growth hormone (GH)–insulin-like growth factor-1 (IGF1) signaling pathway plays a major role in orchestrating cellular interactions, metabolism, growth and aging. Studies from worms to mice showed that downregulated activity of the GH/IGF1 pathway could be beneficial for the extension of lifespan. Laron syndrome (LS) is an inherited autosomal recessive disorder caused by molecular defects of the GH receptor (GHR) gene, leading to congenital IGF1 deficiency. Life-long exposure to minute endogenous IGF1 levels in LS is associated with low stature as well as other endocrine and metabolic deficits. Epidemiological surveys reported that patients with LS have a reduced risk of developing cancer. Studies conducted on LS-derived lymphoblastoid cells led to the identification of a novel link between IGF1 and thioredoxin-interacting protein (TXNIP), a multifunctional mitochondrial protein. TXNIP is highly expressed in LS patients and plays a critical role in cellular redox regulation by thioredoxin. Given that IGF1 affects the levels of TXNIP under various stress conditions, including high glucose and oxidative stress, we hypothesized that the IGF1–TXNIP axis plays an essential role in helping maintain a physiological balance in cellular homeostasis. In this study, we show that TXNIP is vital for the cell fate choice when cells are challenged by various stress signals. Furthermore, prolonged IGF1 treatment leads to the establishment of a premature senescence phenotype characterized by a unique senescence network signature. Combined IGF1/TXNIP-induced premature senescence can be associated with a typical secretory inflammatory phenotype that is mediated by STAT3/IL-1A signaling. Finally, these mechanistic insights might help with the understanding of basic aspects of IGF1-related pathologies in the clinical setting.

Single-cell analysis of menstrual endometrial tissues defines phenotypes associated with endometriosis

BACKGROUND

Endometriosis is a common, complex disorder which is underrecognized and subject to prolonged delays in diagnosis. It is accompanied by significant changes in the eutopic endometrial lining.

METHODS

We have undertaken the first single-cell RNA-sequencing (scRNA-Seq) comparison of endometrial tissues in freshly collected menstrual effluent (ME) from 33 subjects, including confirmed endometriosis patients (cases) and controls as well as symptomatic subjects (who have chronic symptoms suggestive of endometriosis but have not been diagnosed).

RESULTS

We identify a unique subcluster of proliferating uterine natural killer (uNK) cells in ME-tissues from controls that is almost absent from endometriosis cases, along with a striking reduction of total uNK cells in the ME of cases (p < 10^-16). In addition, an IGFBP1+ decidualized subset of endometrial stromal cells are abundant in the shed endometrium of controls when compared to cases (p < 10^-16) confirming findings of compromised decidualization of cultured stromal cells from cases. By contrast, endometrial stromal cells from cases are enriched in cells expressing pro-inflammatory and senescent phenotypes. An enrichment of B cells in the cases (p = 5.8 × 10^-6) raises the possibility that some may have chronic endometritis, a disorder which predisposes to endometriosis.

CONCLUSIONS

We propose that characterization of endometrial tissues in ME will provide an effective screening tool for identifying endometriosis in patients with chronic symptoms suggestive of this disorder. This constitutes a major advance, since delayed diagnosis for many years is a major clinical problem in the evaluation of these patients. Comprehensive analysis of ME is expected to lead to new diagnostic and therapeutic approaches to endometriosis and other associated reproductive disorders such as female infertility.

Plasma proteome profiling of healthy individuals across the life span in a Sicilian cohort with long-lived individuals

The study of healthy human aging is important for shedding light on the molecular mechanisms behind aging to promote well-being and to possibly predict and/or avoid the development of age-related disorders such as atherosclerosis and diabetes. Herein, we have employed an untargeted mass spectrometry-based approach to study age-related protein changes in a healthy Sicilian plasma cohort including long-lived individuals. This approach confirmed some of the previously known proteins correlated with age including fibulin-1, dystroglycan, and gamma-glutamyl hydrolase. Furthermore, our findings include novel proteins that correlate with age and/or with location and uric acid, which could represent a unique signature for healthy aging.

Establishment of three heterogeneous subtypes and a risk model of low-grade gliomas based on cell senescence-related genes

Background

Cellular senescence is a key element in the occurrence and progression of a variety of tumors. As a result, cellular senescence-related markers can be categorized based on the prognosis status of patients. Due to the heterogeneity and the complexity of the tumor microenvironment (TME), the long-term effectiveness of low-grade glioma (LGG) treatment remains a clinical challenge. Consequently, developing and refining effective treatment approaches to aid with LGG management is critical.

Methods

Based on the expressions of cell senescence-related genes (CSRGs) acquired from the cellAge database, consensus clustering was utilized to identify stable molecular subtypes. Clinical features, immune infiltration, route modifications, and genetic changes of various subtypes were also assessed. Following that, the least absolute shrinkage and selection operator (LASSO) regression and univariate Cox regression analysis were used for developing the cell senescence-related risk score (CSRS) model. Finally, a correlation study of the CSRS model with molecular, immunological, and immunotherapy parameters was performed.

Results

C1, C2, and C3, are the three senescence-related subtypes that were identified. Patients belonging to the C1 subtype had poor prognoses and a substantial proportion of them was in the grade G3. The differentially expressed genes (DEGs) among the three subtypes were used to develop the CSRS model. In both the training and independent validation cohort, the model had a high area under the receiver operating characteristic (ROC) curve in predicting the overall survival (OS) of patients. As a result, this model can predict clinical features and responses to immunotherapy in a variety of patients and it is a potential independent prognostic factor for LGG.

Conclusion

This research discovered three LGG subtypes related to cell senescence and created a CSRS model for six genes. Cell senescence was highly associated with unfavorable prognosis in LGG. The CSRS model can be used to predict the prognosis of patients and identify patients who would benefit from immunotherapy.

Role of Peritoneal Mesothelial Cells in the Progression of Peritoneal Metastases

Peritoneal metastatic cancer comprises a heterogeneous group of primary tumors that originate in the peritoneal cavity or metastasize into the peritoneal cavity from a different origin. Metastasis is a characteristic of end-stage disease, often indicative of a poor prognosis with limited treatment options. Peritoneal mesothelial cells (PMCs) are a thin layer of cells present on the surface of the peritoneum. They display differentiated characteristics in embryonic development and adults, representing the first cell layer encountering peritoneal tumors to affect their progression. PMCs have been traditionally considered a barrier to the intraperitoneal implantation and metastasis of tumors; however, recent studies indicate that PMCs can either inhibit or actively promote tumor progression through distinct mechanisms. This article presents a review of the role of PMCs in the progression of peritoneum implanted tumors, offering new ideas for therapeutic targets and related research.

Knockout of HDAC9 Gene Enhances Foot-and-Mouth Disease Virus Replication

Foot-and-mouth disease virus (FMDV) is a highly contagious viral disease that mainly infects cloven-hoofed animals. Propagation of FMDV by cell culture is an important method to preserve viral biological and antigenic characteristics, which is crucial in FMD monitoring and vaccine production. However, only a few cell lines are sensitive to FMDV, and there is still a lot of room for improvement. Acetylation is an important post-translational modification, which is dynamically regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs). However, the study of the relationship between FMDV and HDACs is still unclear. HDAC9 belongs to the class II of HDACs family; in this study, HDAC9 knockout (KO) BHK-21 cells were successfully established using CRISPR/cas9 technology. The results of karyotype analysis, growth curve analysis, and morphological observation showed that the HDAC9 knockout cell line was stable in growth and morphological characteristics. After infection with FMDV, the expression of viral RNA and protein, viral titers, and the copies of viral RNA in HDAC9-KO cells were significantly higher than those in NC cells. Meanwhile, RNA-seq technology was used to sequence HDAC9-KO cells and NC cells infected and uninfected with FMDV. It was found that the differentially expressed innate immune factors containing NFKBIA, SOD2, IL2RG, BCL2L1, CXCL1/2/3, and IL1RAP have significantly enriched in the Jak-STAT, NOD-like receptor, Toll-like receptor, NF-κB, and MAPK signaling pathway. RT-qPCR was performed to detect the expression level of differentially expressed genes and showed consistency with the RNA-seq data. These results preliminarily reveal the role of HDAC9 in host antiviral innate immune response, and the HDAC9-KO cell line could also serve as a useful tool for FMDV research.

GH and Senescence: A New Understanding of Adult GH Action

Replicative senescence occurs due to an inability to repair DNA damage and activation of p53/p21 and p16INK4 pathways. It is considered a preventive mechanism for arresting proliferation of DNA-damaged cells. Stably senescent cells are characterized by a senescence-associated secretory phenotype (SASP), which produces and secretes cytokines, chemokines, and/or matrix metalloproteinases depending on the cell type. SASP proteins may increase cell proliferation, facilitating conversion of premalignant to malignant tumor cells, triggering DNA damage, and altering the tissue microenvironment. Further, senescent cells accumulate with age, thereby aggravating age-related tissue damage. Here, we review a heretofore unappreciated role for growth hormone (GH) as a SASP component, acting in an autocrine and paracrine fashion. In senescent cells, GH is activated by DNA-damage-induced p53 and inhibits phosphorylation of DNA repair proteins ATM, Chk2, p53, and H2AX. Somatotroph adenomas containing abundant intracellular GH exhibit increased somatic copy number alterations, indicative of DNA damage, and are associated with induced p53/p21. As this pathway restrains proliferation of DNA-damaged cells, these mechanisms may underlie the senescent phenotype and benign nature of slowly proliferating pituitary somatotroph adenomas. In highly proliferative cells, such as colon epithelial cells, GH induced in response to DNA damage suppresses p53, thereby triggering senescent cell proliferation. As senescent cells harbor unrepaired DNA damage, GH may enable senescent cells to evade senescence and reenter the cell cycle, resulting in acquisition of harmful mutations. These mechanisms, at least in part, may underlie pro-aging effects of GH observed in animal models and in patients with chronically elevated GH levels.

Sorafenib, rapamycin, and venetoclax attenuate doxorubicin-induced senescence and promote apoptosis in HCT116 cells

Emerging evidence has shown that the therapy-induced senescent growth arrest in cancer cells is of durable nature whereby a subset of cells can reinstate proliferative capacity. Promising new drugs named senolytics selectively target senescent cells and commit them into apoptosis. Accordingly, senolytics have been proposed as adjuvant cancer treatment to cull senescent tumor cells, and thus, screening for agents that exhibit senolytic properties is highly warranted. Our study aimed to investigate three agents, sorafenib, rapamycin, and venetoclax for their senolytic potential in doxorubicin-induced senescence in HCT116 cells. HCT116 cells were treated with one of the three agents, sorafenib (5 µM), rapamycin (100 nM), or venetoclax (10 µM), in the absence or presence of doxorubicin (1 µM). Senescence was evaluated using microscopy-based and flow cytometry-based Senescence-associated-β-galactosidase staining (SA-β-gal), while apoptosis was assessed using annexin V-FITC/PI, and Muse caspase-3/-7 activity assays. We screened for potential genes through which the three drugs exerted senolytic-like action using the Human Cancer Pathway Finder PCR array. The three agents reduced doxorubicin-induced senescent cell subpopulations and significantly enhanced the apoptotic effect of doxorubicin compared with those treated only with doxorubicin. The senescence genes IGFBP5 and BMI1 and the apoptosis genes CASP7 and CASP9 emerged as candidate genes through which the three drugs exhibited senolytic-like properties. These results suggest that the attenuation of doxorubicin-induced senescence might have shifted HCT116 cells to apoptosis by exposure to the tested pharmacological agents. Our work argues for the use of senolytics to reduce senescence-mediated resistance in tumor cells and to enhance chemotherapy efficacy.

Dynamic Aging: Channeled Through Microenvironment

Aging process is a complicated process that involves deteriorated performance at multiple levels from cellular dysfunction to organ degeneration. For many years research has been focused on how aging changes things within cell. However, new findings suggest that microenvironments, circulating factors or inter-tissue communications could also play important roles in the dynamic progression of aging. These out-of-cell mechanisms pass on the signals from the damaged aging cells to other healthy cells or tissues to promote systematic aging phenotypes. This review discusses the mechanisms of how senescence and their secretome, NAD⁺ metabolism or circulating factors change microenvironments to regulate systematic aging, as well as the potential therapeutic strategies based on these findings for anti-aging interventions.

Single cell RNA sequencing identifies IGFBP5 and QKI as ciliated epithelial cell genes associated with severe COPD

Background

Whole lung tissue transcriptomic profiling studies in chronic obstructive pulmonary disease (COPD) have led to the identification of several genes associated with the severity of airflow limitation and/or the presence of emphysema, however, the cell types driving these gene expression signatures remain unidentified.

Methods

To determine cell specific transcriptomic changes in severe COPD, we conducted single-cell RNA sequencing (scRNA seq) on n = 29,961 cells from the peripheral lung parenchymal tissue of nonsmoking subjects without underlying lung disease (n = 3) and patients with severe COPD (n = 3). The cell type composition and cell specific gene expression signature was assessed. Gene set enrichment analysis (GSEA) was used to identify the specific cell types contributing to the previously reported transcriptomic signatures.

Results

T-distributed stochastic neighbor embedding and clustering of scRNA seq data revealed a total of 17 distinct populations. Among them, the populations with more differentially expressed genes in cases vs. controls (log fold change >|0.4| and FDR = 0.05) were: monocytes (n = 1499); macrophages (n = 868) and ciliated epithelial cells (n = 590), respectively. Using GSEA, we found that only ciliated and cytotoxic T cells manifested a trend towards enrichment of the previously reported 127 regional emphysema gene signatures (normalized enrichment score [NES] = 1.28 and = 1.33, FDR = 0.085 and = 0.092 respectively). Among the significantly altered genes present in ciliated epithelial cells of the COPD lungs, QKI and IGFBP5 protein levels were also found to be altered in the COPD lungs.

Conclusions

scRNA seq is useful for identifying transcriptional changes and possibly individual protein levels that may contribute to the development of emphysema in a cell-type specific manner.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01675-2.

The Impact of Spaceflight and Microgravity on the Human Islet-1+ Cardiovascular Progenitor Cell Transcriptome

Understanding the transcriptomic impact of microgravity and the spaceflight environment is relevant for future missions in space and microgravity-based applications designed to benefit life on Earth. Here, we investigated the transcriptome of adult and neonatal cardiovascular progenitors following culture aboard the International Space Station for 30 days and compared it to the transcriptome of clonally identical cells cultured on Earth. Cardiovascular progenitors acquire a gene expression profile representative of an early-stage, dedifferentiated, stem-like state, regardless of age. Signaling pathways that support cell proliferation and survival were induced by spaceflight along with transcripts related to cell cycle re-entry, cardiovascular development, and oxidative stress. These findings contribute new insight into the multifaceted influence of reduced gravitational environments.

Senescent Colon and Breast Cancer Cells Induced by Doxorubicin Exhibit Enhanced Sensitivity to Curcumin, Caffeine, and Thymoquinone

Cellular senescence is a process of physiological growth arrest that can be induced by intrinsic or extrinsic stress signals. Some cancer therapies are associated with senescence of cancer cells with a typical cell cycle arrest. Doxorubicin (Dox) induces senescence by a p53-dependent pathway and telomere dysfunction of numerous cancers. However, cellular senescence induces suppression in proliferation activity, and these cells will remain metabolically active and play an important role in tumor relapse and development of drug resistance. In the current study, we investigated the apoptotic effect of curcumin (Cur), caffeine (Caff), and thymoquinone (TQ) on senescent colon cancer HCT116 and breast cancer MCF7 cell lines treated with Dox. Results showed typical senescence markers including decreased bromodeoxyuridine incorporation, increased accumulation of senescence-associated β-galactosidase (SA-β-gal), cell cycle arrest, and upregulation of p53, P-p53, and p21 proteins. Annexin-V analysis by flow cytometry revealed 2- to 6-fold increases in annexin-V–positive cells in Dox-treated MCF7 and HCT116 cells by Cur (15 µM), Caff (10 mM), and TQ (50 µM; P < .001). In comparison between proliferative and senescent of either HCT116 or MCF7 cells, Caff at 15 mM and TQ at 25 µM induced significant increases in apoptosis of Dox-treated cells compared with proliferative cells (P < .001). Data revealed that Cur, Caff, and TQ potentially induced apoptosis of both proliferative and senescent HCT116 and MCF7 cells. In vivo and clinical trials are of great importance to validate this result.

Beneficial Effects of a Mixture of Algae and Extra Virgin Olive Oils on the Age-Induced Alterations of Rodent Skeletal Muscle: Role of HDAC-4

Aging is associated with a progressive decline in skeletal muscle mass, strength and function (sarcopenia). We have investigated whether a mixture of algae oil (25%) and extra virgin olive oil (75%) could exert beneficial effects on sarcopenia. Young (3 months) and old (24 months) male Wistar rats were treated with vehicle or with the oil mixture (OM) (2.5 mL/kg) for 21 days. Aging decreased gastrocnemius weight, total protein, and myosin heavy chain mRNA. Treatment with the OM prevented these effects. Concomitantly, OM administration decreased the inflammatory state in muscle; it prevented the increase of pro-inflammatory interleukin-6 (IL-6) and the decrease in anti-inflammatory interleukin-10 (IL-10) in aged rats. The OM was not able to prevent aging-induced alterations in either the insulin-like growth factor I/protein kinase B (IGF-I/Akt) pathway or in the increased expression of atrogenes in the gastrocnemius. However, the OM prevented decreased autophagy activity (ratio protein 1A/1B-light chain 3 (LC3b) II/I) induced by aging and increased expression of factors related with muscle senescence such as histone deacetylase 4 (HDAC-4), myogenin, and IGF-I binding protein 5 (IGFBP-5). These data suggest that the beneficial effects of the OM on muscle can be secondary to its anti-inflammatory effect and to the normalization of HDAC-4 and myogenin levels, making this treatment an alternative therapeutic tool for sarcopenia.

Bidirectional Enhancement of Cell Proliferation Between Iron Oxide Nanoparticle-Labeled Mesenchymal Stem Cells and Choroid Plexus in a Cell-Based Therapy Model of Ischemic Stroke

PURPOSE

Stem cell therapy for ischemic stroke has shown success in experimental settings, but its translation into clinical practice is challenging. The choroid plexus (CP) plays a regulatory role in neural regeneration. Mesenchymal stem cells (MSCs) promote neurogenesis in the ventricular-subventricular zone. However, it is unclear whether MSCs interact with the CP in brain tissue repair.

METHODS

Rat (r)MSCs were labeled with iron oxide nanoparticles (IONs) and transduced with red fluorescent protein, and then injected into the brain of rats with ischemic stroke and monitored over time by magnetic resonance imaging. The functional recovery of rats was determined by the corner test score, Modified Neurological Severity score, and stroke volume. MSCs and CP were also co-cultured for 14 days, and the medium was analyzed with a cytokine array.

RESULTS

In vivo imaging and histologic analysis revealed that ION-labeled MSCs were mainly located at the injection site and migrated to the infarct area and to the CP. Functional recovery was greater in rats treated with MSCs as compared to those that received mock treatment. Bidirectional enhancement of proliferation in MSCs and CP was observed in the co-culture; moreover, MSCs migrated to the CP. Cytokine analysis revealed elevated levels of proliferation- and adhesion-related cytokines and chemokines in the culture medium. Wikipathway predictions indicated that insulin-like growth factor 1/Akt signaling (WP3675), chemokine signaling pathway (WP2292), and spinal cord injury (WP2432) are involved in the increased proliferation and migration of MSCs co-cultured with the CP.

CONCLUSION

Crosstalk with the CP enhances MSC proliferation and migration in a transwell assay. Moreover, MRI reveals MSC migration towards the CP in an ischemic stroke model. The secreted factors resulting from this interaction have therapeutic potential for promoting functional recovery in the brain after ischemic stroke.

Differential gene expression in skin RNA of horses affected with degenerative suspensory ligament desmitis

BACKGROUND

Equine degenerative suspensory ligament desmitis (DSLD) is a systemic connective tissue disorder first identified in Peruvian Paso horses but afflicting other horse breeds as well. Inappropriate accumulation of proteoglycans in connective tissues, most prominently in tendons and ligaments, leads to progressive and debilitating lameness and pain. It is largely unknown what drives the overproduction of proteoglycans, but our previous studies suggest involvement of bone morphogenetic protein 2 (BMP2), a member of the transforming growth factor-β (TGFβ) family, impacting synthesis of proteoglycans. To identify potential players in pathogenesis of DSLD a new approach utilizing next generation sequencing was undertaken.

METHODS

Next generation sequencing was performed using RNA extracted from skin biopsies of six control Peruvian Pasos and six horses with DSLD (4 Peruvian Pasos and 2 warmbloods). The CuffDiff result sets were validated with algorithms used to run them. This was based on the determined false discovery rates derived from the P values adjusted for multiple testing for any given result.

RESULTS

Bioinformatics analysis of transcriptomes revealed differential expression of over 1500 genes, including increased expression of genes for several growth factors (most prominently BMP2, FGF5, CTGF, many members of the EGF family), and mediators of signaling (Fos, Myc, MAPK system), and keratins. Two genes encoding for enzymes involved in synthesis of hyaluronan were also overexpressed. Gene expression was decreased for protein cores of many proteoglycans, several growth factors, most collagens, and many peptides with immune function.

CONCLUSIONS

The overexpression of BMP2 correlates well with our previous data. However, the decrease in expression of numerous proteoglycans was unexpected. A mutation in a gene of a less characterized proteoglycan and/or glycosyltransferase with subsequent increased production of hyaluronan and/or a proteoglycan(s) undetected in our study could account for the systemic proteoglycan deposition. Decreased collagen gene expression indicates abnormal connective tissue metabolism. The increased expression of keratin genes and FGF5 supports reports of skin abnormalities in DSLD. Underexpression of immune function genes corresponds with lack of inflammation in DSLD tissues. Finally, though the proteoglycan and/or glycosaminoglycan abundant in DSLD has not been identified, we validated our previous data, including overexpression of BMP2, and systemic nature of DSLD due to disturbed metabolism of the extracellular matrix.

Normal Aging and Its Role in Cancer Metastasis

Metastasis is the most common cause of death, with treatments failing to provide a durable response. Aging is a key prognostic factor in many cancers. Emerging data suggest that normal age-related changes in the tumor microenvironment can contribute to metastatic progression. These changes encompass secreted factors, biophysical changes, and changes in both stromal and immune cell populations. These data also highlight the importance of conducting studies in preclinical models of appropriate age. Ultimately, therapies may also need to be tailored to reflect patient age, as markers of metastatic disease differ in young and aged populations. In this review, we will discuss some of the changes that occur during aging that increase the metastatic capacity of tumor cells.

Role of Tumor and Stroma-Derived IGF/IGFBPs in Pancreatic Cancer

Pancreatic cancer (PC) is the utmost stroma-rich cancer, which is accompanied by fibrotic reactions that stimulate interactions between tumor cells and stroma to promote tumor progression. Considerable research evidence denotes that insulin-like growth factor (IGF)/IGF binding proteins (IGFBP) signaling axis facilitate tumor growth, metastasis, drug resistance, and thereby facilitate PC into an advanced stage. The six members of IGFBPs were initially considered as passive carriers of free IGFs; however, current evidence revealed their functions beyond the endocrine role in IGF transport. Though numerous efforts have been made in blocking IGF/IGFBPs, the targeted therapies remain unsuccessful due to the complexity of tumor-stromal interactions in the pancreas. In this review, we explore the emerging evidence of the various roles of the tumor as well as stroma derived IGF/IGFBPs and highlight as a novel therapeutic target against PC progression.

Mid-trimester amniotic fluid proteome's association with spontaneous preterm delivery and gestational duration

BACKGROUND

Amniotic fluid is clinically accessible via amniocentesis and its protein composition may correspond to birth timing. Early changes in the amniotic fluid proteome could therefore be associated with the subsequent development of spontaneous preterm delivery.

OBJECTIVE

The main objective of this study was to perform unbiased proteomics analysis of the association between mid-trimester amniotic fluid proteome and spontaneous preterm delivery and gestational duration, respectively. A secondary objective was to validate and replicate the findings by enzyme-linked immunosorbent assay using a second independent cohort.

METHODS

Women undergoing a mid-trimester genetic amniocentesis at Sahlgrenska University Hospital/Östra between September 2008 and September 2011 were enrolled in this study, designed in three analytical stages; 1) an unbiased proteomic discovery phase using LC-MS analysis of 22 women with subsequent spontaneous preterm delivery (cases) and 37 women who delivered at term (controls), 2) a validation phase of proteins of interest identified in stage 1, and 3) a replication phase of the proteins that passed validation using a second independent cohort consisting of 20 cases and 40 matched controls.

RESULTS

Nine proteins were nominally significantly associated with both spontaneous preterm delivery and gestational duration, after adjustment for gestational age at sampling, but none of the proteins were significant after correction for multiple testing. Several of these proteins have previously been described as being associated with spontaneous PTD etiology and six of them were thus validated using enzyme linked immunosorbent assay. Two of the proteins passed validation; Neutrophil gelatinase-associated lipocalin and plasminogen activator inhibitor 1, but the results could not be replicated in a second cohort.

CONCLUSIONS

Neutrophil gelatinase-associated lipocalin and Plasminogen activator inhibitor 1 are potential biomarkers of spontaneous preterm delivery and gestational duration but the findings could not be replicated. The negative findings are supported by the fact that none of the nine proteins from the exploratory phase were significant after correction for multiple testing.

Increase of circulating IGFBP-4 following genotoxic stress and its implication for senescence

Senescent cells secrete several molecules, collectively named senescence-associated secretory phenotype (SASP). In the SASP of cells that became senescent following several in vitro chemical and physical stress, we identified the IGFBP-4 protein that can be considered a general stress mediator. This factor appeared to play a key role in senescence-paracrine signaling. We provided evidences showing that genotoxic injury, such as low dose irradiation, may promote an IGFBP-4 release in bloodstream both in mice irradiated with 100 mGy X-ray and in human subjects that received Computer Tomography. Increased level of circulating IGFBP-4 may be responsible of pro-aging effect. We found a significant increase of senescent cells in the lungs, heart, and kidneys of mice that were intraperitoneally injected with IGFBP-4 twice a week for two months. We then analyzed how genotoxic stressors may promote the release of IGFBP-4 and the molecular pathways associated with the induction of senescence by this protein.

How the ageing microenvironment influences tumour progression

Most cancers arise in individuals over the age of 60. As the world population is living longer and reaching older ages, cancer is becoming a substantial public health problem. It is estimated that, by 2050, more than 20% of the world's population will be over the age of 60 - the economic, healthcare and financial burdens this may place on society are far from trivial. In this Review, we address the role of the ageing microenvironment in the promotion of tumour progression. Specifically, we discuss the cellular and molecular changes in non-cancerous cells during ageing, and how these may contribute towards a tumour permissive microenvironment; these changes encompass biophysical alterations in the extracellular matrix, changes in secreted factors and changes in the immune system. We also discuss the contribution of these changes to responses to cancer therapy as ageing predicts outcomes of therapy, including survival. Yet, in preclinical studies, the contribution of the aged microenvironment to therapy response is largely ignored, with most studies designed in 8-week-old mice rather than older mice that reflect an age appropriate to the disease being modelled. This may explain, in part, the failure of many successful preclinical therapies upon their translation to the clinic. Overall, the intention of this Review is to provide an overview of the interplay that occurs between ageing cell types in the microenvironment and cancer cells and how this is likely to impact tumour metastasis and therapy response.

Paracrine senescence of human endometrial mesenchymal stem cells: a role for the insulin-like growth factor binding protein 3

Stress-induced premature cell senescence is well recognized to be accompanied by emerging the senescence-associated secretory phenotype (SASP). Secreted SASP factors can promote the senescence of normal neighboring cells through autocrine/paracrine pathways and regulate the senescence response, as well. Regarding human endometrium-derived mesenchymal stem cells (MESCs), the SASP regulation mechanisms as well as paracrine activity of senescent cells have not been studied yet. Here, we examined the role of insulin-like growth factor binding protein 3 (IGFBP3) in the paracrine senescence induction in young MESCs. The H₂O₂-induced premature senescence of MESCs led to increased IGFBP3 in conditioned media (CM). The inhibitory analysis of both MAPK and PI3K signaling pathways showed that IGFBP3 releasing from senescent cells is mainly regulated by PI3K/Akt pathway activity. IGFBP3 appears to be an important senescence-mediating factor as its immunodepletion from the senescent CM weakened the pro-senescent effect of CM on young MESCs and promoted their growth. In contrast, young MESCs acquired the senescence phenotype in response to simultaneous addition of recombinant IGFBP3 (rIGFBP3). The mechanism of extracellular IGFBP3 internalization was also revealed. The present study is the first to demonstrate a significant role of extracellular IGFBP3 in paracrine senescence induction of young MESCs.

Microdialysis-Assessed Exercised Muscle Reveals Localized and Differential IGFBP Responses to Unilateral Stretch Shortening Cycle Exercise

Microdialysis allows for a preview into local muscle metabolism and can provide physiological insight that blood measurements cannot. Purpose: To examine the potential differential IGF-I system regulation in interstitial fluid during unilateral stretch shortening cycle exercise. Methods: 10 men (26 ± 7 year) performed unilateral jumping [stretch shortening cycle (SSC) exercise at 50% of optimal jump height] until volitional fatigue on a sled apparatus. Biological sampling took place using a catheter inserted into an antecubital vein (serum), and 100 kDa microdialysis probes inserted into the thigh muscle of each exercise/control leg (dialysate). Serum was drawn before (Pre; -3 h) and after SSC [Post I (+0 h), II (+3 h), or III (+20 h)]; dialysate was sampled for 2 h before (Pre), during/immediately after (Ex), and 3 h into recovery (Rec) following SSC. IGF-I system parameters (free/total IGF-I and IGFBPs 1-6) were measured with immunoassays. Interstitial free IGF-I was estimated from dialysate IGF-I and relative recovery (ethanol) correction. Data were analyzed with repeated measures ANOVA. Results: Serum total IGF-I remained elevated +3 h (Post II: 182.8 ± 37.6 vs. Pre: 168.3 ± 35.0 ng/mL, p < 0.01), but returned to baseline by +20 h (Post III vs. Pre, p = 0.31). No changes in serum free IGF-I were noted. Serum BP-1 and -3 increased over baseline, but not until + 20 h after SSC (Post III vs. Pre: 7.6 ± 4.9 vs. 3.7 ± 2.3 and 1,048.6 ± 269.2 vs. 891.4 ± 171.2 ng/mL, respectively). We observed a decreased serum BP-6 +3 h after SSC (p < 0.01), followed by a return to baseline at +20 h (p = 0.64 vs. Pre). There were no exercise-induced changes in serum BP-2, -4, or -5. Unlike serum, there were no changes in dialysate or interstitial free IGF-I in either leg (p > 0.05). Dialysate BP-1 remained increased in both exercise and control legs through 3 h into recovery (Rec vs. Pre, p < 0.01). Dialysate BP-3 also demonstrated a prolonged elevation over Pre SSC concentrations, but in the exercise leg only (Ex and Rec vs. Pre, p < 0.04). We observed a prolonged decrease in dialysate BP-5 (Ex and Rec vs. Pre, p < 0.03) and an increase in BP-4 IP in the exercise leg only. There were no changes relative to Pre SSC in dialysate BP-2 or -6. Conclusions: Unilateral exercise drives differential regulation of the IGF-I system at both local and systemic levels. More specifically, this is the first study to demonstrate that localized exercise increases IGFBP-3, IGFBP-4 and decreases in IGFBP-5 in muscle interstitial fluid.

Insulin-Like Growth Factor Binding Protein-5 in Physiology and Disease

Insulin-like growth factor (IGF) signaling is regulated by a conserved family of IGF binding proteins (IGFBPs) in vertebrates. Among the six distinct types of IGFBPs, IGFBP-5 is the most highly conserved across species and has the broadest range of biological activities. IGFBP-5 is expressed in diverse cell types, and its expression level is regulated by a variety of signaling pathways in different contexts. IGFBP-5 can exert a range of biological actions including prolonging the half-life of IGFs in the circulation, inhibition of IGF signaling by competing with the IGF-1 receptor for ligand binding, concentrating IGFs in certain cells and tissues, and potentiation of IGF signaling by delivery of IGFs to the IGF-1 receptor. IGFBP-5 also has IGF-independent activities and is even detected in the nucleus. Its broad biological activities make IGFBP-5 an excellent representative for understanding IGFBP functions. Despite its evolutionary conservation and numerous biological activities, knockout of IGFBP-5 in mice produced only a negligible phenotype. Recent research has begun to explain this paradox by demonstrating cell type-specific and physiological/pathological context-dependent roles for IGFBP-5. In this review, we survey and discuss what is currently known about IGFBP-5 in normal physiology and human disease. Based on recent in vivo genetic evidence, we suggest that IGFBP-5 is a multifunctional protein with the ability to act as a molecular switch to conditionally regulate IGF signaling.