Inhibition of overactive TGF-β attenuates progression of heterotopic ossification in mice

Acquired heterotopic ossification (HO) is a painful and debilitating disease characterized by extraskeletal bone formation after injury. The exact pathogenesis of HO remains unknown. Here we show that TGF-β initiates and promotes HO in mice. We find that calcified cartilage and newly formed bone resorb osteoclasts after onset of HO, which leads to high levels of active TGF-β that recruit mesenchymal stromal/progenitor cells (MSPCs) in the HO microenvironment. Transgenic expression of active TGF-β in tendon induces spontaneous HO, whereas systemic injection of a TGF-β neutralizing antibody attenuates ectopic bone formation in traumatic and BMP-induced mouse HO models, and in a fibrodysplasia ossificans progressive mouse model. Moreover, inducible knockout of the TGF-β type II receptor in MSPCs inhibits HO progression in HO mouse models. Our study points toward elevated levels of active TGF-β as inducers and promoters of ectopic bone formation, and suggest that TGF-β might be a therapeutic target in HO.

Angiogenesis stimulated by elevated PDGF-BB in subchondral bone contributes to osteoarthritis development

Increased subchondral bone angiogenesis with blood vessels breaching the tidemark into the avascular cartilage is a diagnostic feature of human osteoarthritis. However, the mechanisms that initiate subchondral bone angiogenesis remain unclear. We show that abnormally increased platelet-derived growth factor-BB (PDGF-BB) secretion by mononuclear preosteoclasts induces subchondral bone angiogenesis, contributing to osteoarthritis development. In mice after destabilization of the medial meniscus (DMM), aberrant joint subchondral bone angiogenesis developed during an early stage of osteoarthritis, before articular cartilage damage occurred. Mononuclear preosteoclasts in subchondral bone secrete excessive amounts of PDGF-BB, which activates platelet-derived growth factor receptor-β (PDGFR-β) signaling in pericytes for neo-vessel formation. Selective knockout of PDGF-BB in preosteoclasts attenuates subchondral bone angiogenesis and abrogates joint degeneration and subchondral innervation induced by DMM. Transgenic mice that express PDGF-BB in preosteoclasts recapitulate pathological subchondral bone angiogenesis and develop joint degeneration and subchondral innervation spontaneously. Our study provides the first evidence to our knowledge that PDGF-BB derived from preosteoclasts is a key driver of pathological subchondral bone angiogenesis during osteoarthritis development and offers a new avenue for developing early treatments for this disease.

PDGF-BB regulates splitting angiogenesis in skeletal muscle by limiting VEGF-induced endothelial proliferation

VEGF induces normal or aberrant angiogenesis depending on its dose in the microenvironment around each producing cell in vivo. This transition depends on the balance between VEGF-induced endothelial stimulation and PDGF-BB-mediated pericyte recruitment, and co-expression of PDGF-BB normalizes aberrant angiogenesis despite high VEGF doses. We recently found that VEGF over-expression induces angiogenesis in skeletal muscle through an initial circumferential vascular enlargement followed by longitudinal splitting, rather than sprouting. Here we investigated the cellular mechanism by which PDGF-BB co-expression normalizes VEGF-induced aberrant angiogenesis. Monoclonal populations of transduced myoblasts, expressing similarly high levels of VEGF alone or with PDGF-BB, were implanted in mouse skeletal muscles. PDGF-BB co-expression did not promote sprouting and angiogenesis that occurred through vascular enlargement and splitting. However, enlargements were significantly smaller in diameter, due to a significant reduction in endothelial proliferation, and retained pericytes, which were otherwise lost with high VEGF alone. A time-course of histological analyses and repetitive intravital imaging showed that PDGF-BB co-expression anticipated the initiation of vascular enlargement and markedly accelerated the splitting process. Interestingly, quantification during in vivo imaging suggested that a global reduction in shear stress favored the initiation of transluminal pillar formation during VEGF-induced splitting angiogenesis. Quantification of target gene expression showed that VEGF-R2 signaling output was significantly reduced by PDGF-BB co-expression compared to VEGF alone. In conclusion, PDGF-BB co-expression prevents VEGF-induced aberrant angiogenesis by modulating VEGF-R2 signaling and endothelial proliferation, thereby limiting the degree of circumferential enlargement and enabling efficient completion of vascular splitting into normal capillary networks despite high VEGF doses.

Harmine enhances type H vessel formation and prevents bone loss in ovariectomized mice

Recently, researchers identified a distinct vessel subtype called type H vessels that couple angiogenesis and osteogenesis. We previously found that type H vessels are reduced in ovariectomy (OVX)-induced osteoporotic mice, and preosteoclasts are able to secrete platelet-derived growth factor-BB (PDGF-BB) to stimulate type H vessel formation and thereby to promote osteogenesis. This study aimed to explore whether harmine, a β-carboline alkaloid, is capable of preventing bone loss in OVX mice by promoting preosteoclast PDGF-BB-induced type H vessel formation.

METHODS

The impact of harmine on osteoclastogenesis of RANKL-stimulated RAW264.7 cells was verified by gene expression analysis and tartrate-resistant acid phosphatase (TRAP) staining. Enzyme-linked immunosorbent assay (ELISA) was conducted to test PDGF-BB production by preosteoclasts. A series of angiogenesis-related assays in vitro were performed to assess the pro-angiogenic effects of the conditioned media from RANKL-stimulated RAW264.7 cells treated with or without harmine. Meanwhile, the role of PDGF-BB in this process was determined. In vivo, OVX mice were intragastrically administrated with harmine emulsion or an equal volume of vehicle. 2 months later, bone samples were collected for µCT, histological, immunohistochemical and immunofluorescent analyses to evaluate bone mass, osteogenic and osteoclastic activities, as well as the numbers of type H vessels. Bone marrow PDGF-BB concentrations were assessed by ELISA.

RESULTS

Exposure of RANKL-stimulated RAW264.7 cells to harmine enhanced the formation of preosteoclasts and the production of PDGF-BB. Harmine augmented the ability of RANKL-stimulated RAW264.7 cells to promote angiogenesis of endothelial cells, whereas the effect was blocked by PDGF-BB inhibition. In vivo, the oral administration of harmine emulsion to OVX mice resulted in enhanced trabecular bone mass and osteogenic responses, increased numbers of preosteoclasts, as well as reduced numbers of osteoclasts and fat cells. Moreover, OVX mice treated with harmine exhibited higher levels of bone marrow PDGF-BB and much more type H vessels in bone.

CONCLUSION

Harmine may exert bone-sparing effects by suppression of osteoclast formation and promotion of preosteoclast PDGF-BB-induced angiogenesis.

Defining Endothelial Cell-Derived Factors That Promote Pericyte Recruitment and Capillary Network Assembly

OBJECTIVE

We sought to identify and investigate the functional role of the major endothelial cell (EC)-derived factors that control pericyte recruitment to EC tubes and pericyte-induced tube maturation during capillary network formation. Approach and Results: We identify PDGF (platelet-derived growth factor)-BB, PDGF-DD, ET (endothelin)-1, TGF (transforming growth factor)-β, and HB-EGF (heparin-binding epidermal growth factor), as the key individual and combined regulators of pericyte assembly around EC tubes. Using novel pericyte only assays, we demonstrate that PDGF-BB, PDGF-DD, and ET-1 are the primary direct drivers of pericyte invasion. Their addition to pericytes induces invasion as if ECs were present. In contrast, TGF-β and HB-EGF have minimal ability to directly stimulate pericyte invasion. In contrast, TGF-β1 can act as an upstream pericyte primer to stimulate invasion in response to PDGFs and ET-1. HB-EGF stimulates pericyte proliferation along with PDGFs and ET-1. Using EC-pericyte cocultures, individual, or combined blockade of these EC-derived factors, or their pericyte receptors, using neutralizing antibodies or chemical inhibitors, respectively, interferes with pericyte recruitment and proliferation. As individual factors, PDGF-BB and ET-1 have the strongest impact on these events. However, when the blocking reagents are combined to interfere with each of the above factors or their receptors, more dramatic and profound blockade of pericyte recruitment, proliferation, and pericyte-induced basement membrane deposition occurs. Under these conditions, ECs form tubes that become much wider and less elongated as if pericytes were absent.

CONCLUSIONS

Overall, these new studies define and characterize a functional role for key EC-derived factors controlling pericyte recruitment, proliferation, and pericyte-induced basement membrane deposition during capillary network assembly.

Preservation of type H vessels and osteoblasts by enhanced preosteoclast platelet-derived growth factor type BB attenuates glucocorticoid-induced osteoporosis in growing mice

Survival of chronic diseases in childhood is often achieved utilizing glucocorticoids, but comes with significant side effects, including glucocorticoid-induced osteoporosis (GIO). Knowledge of the mechanism of GIO is limited to the adult skeleton. We explored the effect of genetic loss and inhibition of cathepsin K (Ctsk) as a potential treatment target in a young GIO mouse model as genetic loss of cathepsin K results in a mild form of osteopetrosis secondary to impaired osteoclast bone resorption with maintenance of bone formation. We first characterized the temporal osteoclast and osteoblast progenitor populations in Ctsk^-/- and wild type (WT) mice in the primary and secondary spongiosa, as sites representative of trabecular bone modeling and remodeling, respectively. In the primary spongiosa, Ctsk^-/- mice had decreased numbers of osteoclasts at young ages (2 and 4 weeks) and increased osteoblast lineage cells at later age (8 weeks) relative to WT littermates. In the secondary spongiosa, Ctsk^-/- mice had greater numbers of osteoclasts and osteoblast lineage cells relative to WT littermates. We next developed a young GIO mouse model with prednisolone 10 mg/m²/day injected intraperitoneally daily from 2 through 6 weeks of age. Overall, WT-prednisolone mice had lower bone volume per tissue volume, whereas Ctsk^-/--prednisolone mice maintained a similar bone volume relative to Ctsk^-/--vehicle controls. WT-prednisolone mice exhibited a decreased number of osteoclasts, tartrate-resistant acid phosphatase and platelet-derived growth factor type BB (PDGF-BB) co-positive cells, type H endothelial cells, and osteoblasts relative to WT-vehicle mice in both the primary and secondary spongiosa. Interestingly, Ctsk^-/--prednisolone mice demonstrated a paradoxical response with increased numbers of all parameters in primary spongiosa and no change in secondary spongiosa. Finally, treatment with a cathepsin K inhibitor prevented WT-prednisolone decline in osteoclasts, osteoblasts, type H vessels, and bone volume. These data demonstrate that cells in the primary and secondary spongiosa respond differently to glucocorticoids and genetic manipulation. Inhibition of osteoclast resorption that preserves osteoclast coupling factors, such as through inhibition of cathepsin K, may be a potential preventive treatment strategy against GIO in the growing skeleton.

Quantitative 3D imaging of the cranial microvascular environment at single-cell resolution

Vascularization is critical for skull development, maintenance, and healing. Yet, there remains a significant knowledge gap in the relationship of blood vessels to cranial skeletal progenitors during these processes. Here, we introduce a quantitative 3D imaging platform to enable the visualization and analysis of high-resolution data sets (>100 GB) throughout the entire murine calvarium. Using this technique, we provide single-cell resolution 3D maps of vessel phenotypes and skeletal progenitors in the frontoparietal cranial bones. Through these high-resolution data sets, we demonstrate that CD31hiEmcnhi vessels are spatially correlated with both Osterix+ and Gli1+ skeletal progenitors during postnatal growth, healing, and stimulated remodeling, and are concentrated at transcortical canals and osteogenic fronts. Interestingly, we find that this relationship is weakened in mice with a conditional knockout of PDGF-BB in TRAP+ osteoclasts, suggesting a potential role for osteoclasts in maintaining the native cranial microvascular environment. Our findings provide a foundational framework for understanding how blood vessels and skeletal progenitors spatially interact in cranial bone, and will enable more targeted studies into the mechanisms of skull disease pathologies and treatments. Additionally, our technique can be readily adapted to study numerous cell types and investigate other elusive phenomena in cranial bone biology.

ETS variant 5 promotes colorectal cancer angiogenesis by targeting platelet-derived growth factor BB

ETS transcription factors play important roles in tumor cell invasion, differentiation and angiogenesis. In this study, we initially demonstrated that ETS translocation variant 5 (ETV5) is abnormally upregulated in colorectal cancer (CRC), is positively correlated with CRC tumor size, lymphatic metastasis and tumor node metastasis (TNM) stage and indicates shorter survival and disease-free survival in CRC patients. In vitro and in vivo experiments revealed that the downregulation of ETV5 could significantly suppress CRC cell proliferation. Moreover, overexpression of ETV5 could stimulate CRC angiogenesis in vitro and in vivo, which is consistent with RNA-seq results. Then, we identified platelet-derived growth factor BB (PDGF-BB) as a direct target of ETV5 that plays an important role in ETV5-mediated CRC angiogenesis through an angiogenesis antibody microarray. Additionally, PDGF-BB could activate VEGFA expression via the PDGFR-β/Src/STAT3 pathway in CRC cells and appeared to be positively correlated with ETV5 in CRC tissues. Finally, we revealed that ETV5 could bind directly to the promoter region of PDGF-BB and regulate its expression through ChIP and luciferase assays. Overall, our study suggested that the transcription factor ETV5 could stimulate CRC malignancy and promote CRC angiogenesis by directly targeting PDGF-BB. These findings suggest that EVT5 may be a potential new diagnostic and prognostic marker in CRC and that targeting ETV5 might be a potential therapeutic option for inhibiting CRC angiogenesis.

Functional regulatory mechanism of smooth muscle cell-restricted LMOD1 coronary artery disease locus

Recent genome-wide association studies (GWAS) have identified multiple new loci which appear to alter coronary artery disease (CAD) risk via arterial wall-specific mechanisms. One of the annotated genes encodes LMOD1 (Leiomodin 1), a member of the actin filament nucleator family that is highly enriched in smooth muscle-containing tissues such as the artery wall. However, it is still unknown whether LMOD1 is the causal gene at this locus and also how the associated variants alter LMOD1 expression/function and CAD risk. Using epigenomic profiling we recently identified a non-coding regulatory variant, rs34091558, which is in tight linkage disequilibrium (LD) with the lead CAD GWAS variant, rs2820315. Herein we demonstrate through expression quantitative trait loci (eQTL) and statistical fine-mapping in GTEx, STARNET, and human coronary artery smooth muscle cell (HCASMC) datasets, rs34091558 is the top regulatory variant for LMOD1 in vascular tissues. Position weight matrix (PWM) analyses identify the protective allele rs34091558-TA to form a conserved Forkhead box O3 (FOXO3) binding motif, which is disrupted by the risk allele rs34091558-A. FOXO3 chromatin immunoprecipitation and reporter assays show reduced FOXO3 binding and LMOD1 transcriptional activity by the risk allele, consistent with effects of FOXO3 downregulation on LMOD1. LMOD1 knockdown results in increased proliferation and migration and decreased cell contraction in HCASMC, and immunostaining in atherosclerotic lesions in the SMC lineage tracing reporter mouse support a key role for LMOD1 in maintaining the differentiated SMC phenotype. These results provide compelling functional evidence that genetic variation is associated with dysregulated LMOD1 expression/function in SMCs, together contributing to the heritable risk for CAD.

FSP1-positive fibroblasts are adipogenic niche and regulate adipose homeostasis

Adipocyte progenitors reside in the stromal vascular fraction (SVF) of adipose tissues that are composed of fibroblasts, immune cells, and endothelial cells. It remains to be elucidated how the SVF regulates adipocyte progenitor fate determination and adipose homeostasis. Here, we report that fibroblast-specific protein-1 (FSP1)⁺ fibroblasts in the SVF are essential to adipose homeostasis. FSP1⁺ fibroblasts, devoid of adipogenic potential, are adjacent to the preadipocytes in the SVF. Ablation of FSP1⁺ fibroblasts in mice severely diminishes fat content of adipose depots. Activation of canonical Wnt signaling in the FSP1⁺ fibroblasts results in gradual loss of adipose tissues and resistance to diet-induced obesity. Alterations in the FSP1⁺ fibroblasts reduce platelet-derived growth factor (PDGF)-BB signaling and result in the loss of preadipocytes. Reduced PDGF-BB signaling, meanwhile, impairs the adipogenic differentiation capability of preadipocytes by regulating matrix metalloproteinase (MMP) expression, extracellular matrix remodeling, and the activation of Yes-associated protein (YAP) signaling. Thus, FSP1⁺ fibroblasts are an important niche essential to the maintenance of the preadipocyte pool and its adipogenic potential in adipose homeostasis.

White adipose tissue (WAT), which consists mostly of adipocytes, is not only a passive energy storage but also an active metabolic and endocrine organ in the body. The importance of maintaining proper adipose mass is emphasized by the fact that both adipose tissue excess—in obese individuals—and deficiency have adverse metabolic consequences. In order to maintain the number of adipocytes, there is a continuous turnover from preadipocytes in adults. Like any other adult stem cells and progenitor cells, cell fate and differentiation capability of preadipocytes are tightly regulated by a highly specialized niche. However, what constitutes the preadipocyte niche, and how the niche regulates preadipocyte function and adipose homeostasis, remain poorly known. In this study, we have identified fibroblast-specific protein-1 (FSP1)⁺ fibroblasts in the WAT stromal vascular fraction (SVF) of mice as the niche for preadipocytes. We show that FSP1⁺ fibroblasts with aberrant Wnt signaling fail to maintain the preadipocyte pool and its differentiation potential, resulting in loss of adipose tissue. We conclude that FSP1⁺ fibroblasts are a niche for preadipocytes and regulate adipose tissue homeostasis in adult mice.

The involvement of TGF-β1 /FAK/α-SMA pathway in the antifibrotic impact of rice bran oil on thioacetamide-induced liver fibrosis in rats

The objective of the current study is to investigate the effect of rice bran oil (RBO) on hepatic fibrosis as a characteristic response to persistent liver injuries. Rats were randomly allocated into five groups: the negative control group, thioacetamide (TAA) group (thioacetamide 100 mg/kg thrice weekly for two successive weeks, ip), RBO 0.2 and 0.4 groups (RBO 0.2mL and 0.4 mL/rat/day, po) and standard group (silymarin 100 mg/kg/day, po) for two weeks after TAA injection. Blood and liver tissue samples were collected for biochemical, molecular, and histological analyses. Liver functions, oxidative stress, inflammation, liver fibrosis markers were assessed. The obtained results showed that RBO reduced TAA-induced liver fibrosis and suppressed the extracellular matrix formation. Compared to the positive control group, RBO dramatically reduced total bilirubin, AST, and ALT blood levels. Furthermore, RBO reduced MDA and increased GSH contents in the liver. Simultaneously RBO downregulated the NF-κβ signaling pathway, which in turn inhibited the expression of some inflammatory mediators, including Cox-2, IL-1β, and TNF-α. RBO attenuated liver fibrosis by suppressing the biological effects of TGF-β1, α-SMA, collagen I, hydroxyproline, CTGF, and focal adhesion kinase (FAK). RBO reduced liver fibrosis by inhibiting hepatic stellate cell activation and modulating the interplay among the TGF-β1 and FAK signal transduction. The greater dosage of 0.4 mL/kg has a more substantial impact. Hence, this investigation presents RBO as a promising antifibrotic agent in the TAA model through inhibition of TGF-β1 /FAK/α-SMA.

Regulation of autophagy by controlling Erk1/2 and mTOR for platelet-derived growth factor-BB-mediated vascular smooth muscle cell phenotype shift

AIMS

Vascular smooth muscle cell (VSMC) phenotype shift is involved in the pathophysiology of vascular injury or platelet-derived growth factor (PDGF)-induced abnormal proliferation and migration of VSMCs. We aimed to investigate the underlying mechanism involved in PDGF-mediated signaling pathways and autophagy regulation followed by VSMC phenotype shift.

MAIN METHODS

The proliferation, migration and apoptosis of cultured rat aortic VSMCs were measured, and cells undergoing phenotype shift and autophagy were examined. Specific inhibitors for target proteins in signaling pathways were applied to clarify their roles in regulating cell functions.

KEY FINDINGS

PDGF-BB stimulation initiated autophagy activation and synthetic phenotype transition by decreasing α-smooth muscle-actin (SMA), calponin and myosin heavy chain (MHC) and increasing osteopontin (OPN) expression. However, U0126, a potent extracellular signal-regulated kinase 1/2 (Erk1/2) inhibitor, decreased PDGF-BB-induced LC3 expression, while rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), increased it. Furthermore, U0126 decreased the expresseion of autophagy-related genes (Atgs) such as beclin-1, Atg7, Atg5, and Atg12-Atg5 complex, indicating that Erk1/2 is a regulator of PDGF-BB-induced VSMC autophagy. Regardless of autophagy inhibition by U0126 or activation by rapamycin, the PDGF-BB-induced decrease in SMA, calponin and MHC and increase in OPN expression were inhibited. Furthermore, PDGF-BB-stimulated VSMC proliferation, migration and proliferating cell nuclear antigen (PCNA) expression were inhibited by U0126 and rapamycin.

SIGNIFICANCE

These findings suggest that PDGF-BB-induced autophagy is strongly regulated by Erk1/2, an mTOR-independent pathway, and any approach for targeting autophagy modulation is a potential therapeutic strategy for addressing abnormal VSMC proliferation and migration.

Transgenic Silkworm-Based Silk Gland Bioreactor for Large Scale Production of Bioactive Human Platelet-Derived Growth Factor (PDGF-BB) in Silk Cocoons

Human platelet derived growth factor (PDGF) is a major therapeutic protein with great demand in the clinical setting; however, its rate of supply is far from meeting needs. Here, we provide an effective strategy to produce PDGF-BB in large quantities using a transgenic silkworm. The codon-optimized PDGF-B gene regulated by the highly efficient sericin-1 expression system was integrated into the genome of a silkworm. The high transcriptional expression of the PDGF-BB gene in the transgenic silkworm competitively inhibited the transcription expression of the endogenous sericin-1 gene which caused a significant 37.5% decline. The PDGF-BB synthesized in the middle silk gland (MSG) of transgenic silkworms could form a homodimer through intermolecular disulfide bonds, which is then secreted into sericin lumen and finally, distributed in the sericin layer of the cocoon. In this study, a protein quantity of approximately 0.33 mg/g was found in the cocoon. Following a purification process, approximately 150.7 μg of recombinant PDGF-BB with a purity of 82% was purified from 1 g of cocoons. Furthermore, the bioactivity assays showed that the purified recombinant PDGF-BB was able to promote the growth, proliferation and migration of NIH/3T3 cells significantly. These results suggest that the silk gland bioreactor can produce active recombinant PDGF-BB as an efficient mitogen and wound healing agent.

Thymosin β4 protects against aortic aneurysm via endocytic regulation of growth factor signaling

Vascular stability and tone are maintained by contractile smooth muscle cells (VSMCs). However, injury-induced growth factors stimulate a contractile-synthetic phenotypic modulation which increases susceptibility to abdominal aortic aneurysm (AAA). As a regulator of embryonic VSMC differentiation, we hypothesized that Thymosin β4 (Tβ4) may function to maintain healthy vasculature throughout postnatal life. This was supported by the identification of an interaction with low density lipoprotein receptor related protein 1 (LRP1), an endocytic regulator of platelet-derived growth factor BB (PDGF-BB) signaling and VSMC proliferation. LRP1 variants have been implicated by genome-wide association studies with risk of AAA and other arterial diseases. Tβ4-null mice displayed aortic VSMC and elastin defects that phenocopy those of LRP1 mutants, and their compromised vascular integrity predisposed them to Angiotensin II-induced aneurysm formation. Aneurysmal vessels were characterized by enhanced VSMC phenotypic modulation and augmented PDGFR-β signaling. In vitro, enhanced sensitivity to PDGF-BB upon loss of Tβ4 was associated with dysregulated endocytosis, with increased recycling and reduced lysosomal targeting of LRP1-PDGFR-β. Accordingly, the exacerbated aneurysmal phenotype in Tβ4-null mice was rescued upon treatment with the PDGFR-β antagonist Imatinib. Our study identifies Tβ4 as a key regulator of LRP1 for maintaining vascular health, and provides insights into the mechanisms of growth factor-controlled VSMC phenotypic modulation underlying aortic disease progression.

Effects of hyperbaric oxygen therapy on the expression levels of the inflammatory factors interleukin-12p40, macrophage inflammatory protein-1β, platelet-derived growth factor-BB, and interleukin-1 receptor antagonist in keloids

BACKGROUND

Our study aimed to screen and explore the expression of inflammatory factors in keloid patients and to investigate how hyperbaric oxygen (HBO) therapy affects the expression levels of interleukin-12p40 (IL-12p40), macrophage inflammatory protein-1β (MIP-1β), platelet-derived growth factor-BB (PDGF-BB), and interleukin-1 receptor antagonist (IL-1Ra).

OBJECTIVE

30 patients were randomly selected and divided into the following 3 groups: keloid samples from keloid patients treated with HBO therapy (A), keloid samples from keloid patients treated without HBO therapy (B), and normal control skin samples derived from individuals who had no clear scarring (C). Each group included 10 samples.

METHODS

Inflammatory factors in the keloid tissues were measured with the MILLIPLEX multiplexed Luminex system. Hematoxylin and eosin staining, immunohistochemical staining, and Western blotting were used to observe the morphological differences in different tissues and the expression levels.

RESULTS

The expression levels of inflammatory mediators, including IL-12p40, MIP-1β, PDGF-BB, and IL-1Ra, in keloid tissues were significantly different from those in samples of normal skin. Hematoxylin and eosin staining showed significantly greater inflammatory infiltration in keloid tissue. Significantly different expression levels were observed in group A, B, and C.

CONCLUSION

Significantly altered levels of inflammatory factors in the samples from keloid patients were observed, suggesting that formation of a keloid is potentially related to inflammatory responses. HBO therapy could significantly affect the expression levels of IL-12p40, MIP-1β, PDGF-BB, and IL-1Ra, indicating that the effects of HBO therapy are associated with the attenuation of inflammatory responses.

GIT1 is critical for formation of the CD31hiEmcnhi vessel subtype in coupling osteogenesis with angiogenesis via modulating preosteoclasts secretion of PDGF-BB

G protein-coupled receptor kinase 2 interacting protein-1 (GIT1) is a scaffold protein that plays a vital role in bone modeling and remodeling during osteogenesis coupled with angiogenesis. Recent studies have shown that a specialized subset of vascular endothelium strongly positive for CD31 and Endomucin (CD31^hiEmcn^hi) is coupled with anabolic bone formation. Based on our previous finding that GIT1 knockout (GIT1 KO) mice have impaired angiogenesis and bone formation, we hypothesized that GIT1 affects formation of the CD31^hiEmcn^hi vessel subtype. In the current study, GIT1 knockout (GIT1 KO) mice displayed a significant decrease in trabecular bone mass and CD31^hiEmcn^hi vessel number, compared to their wild-type counterparts. In the fracture healing mouse model, GIT1 KO mice contained a lower number of CD31^hiEmcn^hi vessels in fracture callus at days 7 and 14. However, no significant differences in the number of preosteoclasts in bone marrow, trabecular bone and callus in GIT1 KO mice were observed, compared with wild-type mice. Notably, concentrations of serum platelet-derived growth factor-BB(PDGF-BB) secreted by preosteoclasts associated with CD31^hiEmcn^hi vessel formation were lower in GIT1 KO mice. In addition, PDGF-BB-associated expression of phosphorylated extracellular signal-regulated kinase- 1/2 (ERK1/2) and specificity protein 1 (SP1) was significantly decreased in preosteoclasts of GIT1 KO mice. These results collectively suggest that GIT1 is a critical participant in formation of the CD31^hiEmcn^hi vessel subtype, highlighting a novel biologic function of this scaffold protein in preosteoclasts.

A Promising Candidate in Tendon Healing Events—PDGF-BB

Tendon injuries are one of the most common musculoskeletal disorders for which patients seek medical aid, reducing not only the quality of life of the patient but also imposing a significant economic burden on society. The administration of growth factors at the wound site is a feasible solution for enhancing tendon healing. Platelet-derived growth factor-BB (PDGF-BB) has a well-defined safety profile compared to other growth factors and has been approved by the Food and Drug Administration (FDA). The purpose of this review is to summarize the role of PDGF-BB in tendon healing through a comprehensive review of the published literature. Experimental studies suggest that PDGF-BB has a positive effect on tendon healing by enhancing inflammatory responses, speeding up angiogenesis, stimulating tendon cell proliferation, increasing collagen synthesis and increasing the biomechanics of the repaired tendon. PDGF-BB is regarded as a promising candidate in tendon healing. However, in order to realize its full potential, we still need to carefully consider and study key issues such as dose and application time in the future, so as to explore further applications of PDGF-BB in the tendon healing process.

Bone-derived PDGF-BB drives brain vascular calcification in male mice

Brain vascular calcification is a prevalent age-related condition often accompanying neurodegenerative and neuroinflammatory diseases. The pathogenesis of large-vessel calcifications in peripheral tissue is well studied, but microvascular calcification in the brain remains poorly understood. Here, we report that elevated platelet-derived growth factor BB (PDGF-BB) from bone preosteoclasts contributed to cerebrovascular calcification in male mice. Aged male mice had higher serum PDGF-BB levels and a higher incidence of brain calcification compared with young mice, mainly in the thalamus. Transgenic mice with preosteoclast-specific Pdgfb overexpression exhibited elevated serum PDGF-BB levels and recapitulated age-associated thalamic calcification. Conversely, mice with preosteoclast-specific Pdgfb deletion displayed diminished age-associated thalamic calcification. In an ex vivo cerebral microvascular culture system, PDGF-BB dose-dependently promoted vascular calcification. Analysis of osteogenic gene array and single-cell RNA-Seq (scRNA-Seq) revealed that PDGF-BB upregulated multiple osteogenic differentiation genes and the phosphate transporter Slc20a1 in cerebral microvessels. Mechanistically, PDGF-BB stimulated the phosphorylation of its receptor PDGFRβ (p-PDGFRβ) and ERK (p-ERK), leading to the activation of RUNX2. This activation, in turn, induced the transcription of osteoblast differentiation genes in PCs and upregulated Slc20a1 in astrocytes. Thus, bone-derived PDGF-BB induced brain vascular calcification by activating the p-PDGFRβ/p-ERK/RUNX2 signaling cascade in cerebrovascular cells.

Semaphorin-3A protects against neointimal hyperplasia after vascular injury

BACKGROUND

Neointimal hyperplasia is a prominent pathological event during in-stent restenosis. Phenotype switching of vascular smooth muscle cells (VSMCs) from a differentiated/contractile to a dedifferentiated/synthetic phenotype, accompanied by migration and proliferation of VSMCs play an important role in neointimal hyperplasia. However, the molecular mechanisms underlying phenotype switching of VSMCs have yet to be fully understood.

METHODS

The mouse carotid artery ligation model was established to evaluate Sema3A expression and its role during neointimal hyperplasia in vivo. Bioinformatics analysis, chromatin immunoprecipitation (ChIP) assays and promoter-luciferase reporter assays were used to examine regulatory mechanism of Sema3A expression. SiRNA transfection and lentivirus infection were performed to regulate Sema3A expression. EdU assays, Wound-healing scratch experiments and Transwell migration assays were used to assess VSMC proliferation and migration.

FINDINGS

In this study, we found that semaphorin-3A (Sema3A) was significantly downregulated in VSMCs during neointimal hyperplasia after vascular injury in mice and in human atherosclerotic plaques. Meanwhile, Sema3A was transcriptionally downregulated by PDGF-BB via p53 in VSMCs. Furthermore, we found that overexpression of Sema3A inhibited VSMC proliferation and migration, as well as increasing differentiated gene expression. Mechanistically, Sema3A increased the NRP1-plexin-A1 complex and decreased the NRP1-PDGFRβ complex, thus inhibiting phosphorylation of PDGFRβ. Moreover, we found that overexpression of Sema3A suppressed neointimal hyperplasia after vascular injury in vivo.

INTERPRETATION

These results suggest that local delivery of Sema3A may act as a novel therapeutic option to prevent in-stent restenosis.

Autophagy-Related Activation of Hepatic Stellate Cells Reduces Cellular miR-29a by Promoting Its Vesicular Secretion

BACKGROUND & AIMS

Liver fibrosis arises from long-term chronic liver injury, accompanied by an accelerated wound healing response with interstitial accumulation of extracellular matrix (ECM). Activated hepatic stellate cells (HSC) are the main source for ECM production. MicroRNA29a (miR-29a) is a crucial antifibrotic miRNA that is repressed during fibrosis, resulting in up-regulation of collagen synthesis.

METHODS

Intracellular and extracellular miRNA levels of primary and immortalized myofibroblastic HSC in response to profibrogenic stimulation by transforming growth factor β (TGFβ) or platelet-derived growth factor-BB (PDGF-BB) or upon inhibition of vesicular transport and autophagy processes were determined by quantitative polymerase chain reaction. Autophagy flux was studied by electron microscopy, flow cytometry, immunoblotting, and immunocytochemistry. Hepatic and serum miR-29a levels were quantified by using both liver tissue and serum samples from a cohort of chronic hepatitis C virus patients and a murine CCl4 induced liver fibrosis model.

RESULTS

In our study, we show that TGFβ and PDGF-BB resulted in decrease of intracellular miR-29a and a pronounced increase of vesicular miR-29a release into the supernatant. Strikingly, miR-29a vesicular release was accompanied by enhanced autophagic activity and up-regulation of the autophagy marker protein LC3. Moreover, autophagy inhibition strongly prevented miR-29a secretion and repressed its targets' expression such as Col1A1. Consistently, hepatic miR-29a loss and increased LC3 expression in myofibroblastic HSC were associated with increased serum miR-29a levels in CCl4-treated murine liver fibrosis and specimens of hepatitis C virus patients with chronic liver disease.

CONCLUSIONS

We provide evidence that activation-associated autophagy in HSC induces release of miR-29a, whereas inhibition of autophagy represses fibrogenic gene expression in part through attenuated miR-29a secretion.

Wound Dressing Selection Is Critical to Enhance Platelet-Rich Fibrin Activities in Wound Care

The use of platelet-rich fibrin (PRF) is investigated in ulcer management because it provides a healing milieu rich in growth factors and cytokines. Although crucial, the relevance of secondary dressings is under-researched and no data support the use of any particular dressing in preference to another. We assessed the properties of different dressing categories, including alginates, hydrocolloids, foams, hydrofibers, films, meshes and gauzes, in terms of affinity for PRF, releasate management (retention/extrusion) and the kinetics of cytokine release as well as the influence of each combination product, [PRF + dressing], on dermal cell behaviour, aiming to provide useful information for choosing the most adequate dressing for each particular patient. Active dressings including alginates, hydrofibers, foams and hydrocolloids blend with PRF, creating a diverse combination of products with different performances. Alginate and hydrofiber showed the highest affinity but moderate retention of releasate, without interfering with cell functions. Instead, the foam sequestered the releasate and hindered the release of growth factors, thereby compromising cell activities. Film and mesh presented very poor releasate retention and performed similarly to PRF by itself. Affinity index and releasate management explained 79% of platelet-derived growth factor (PDGF-BB) concentration variability, p < 0.001. Cell proliferation depended on the ability of the combination product to retain/release supernatant, PDGF-BB concentration and cell adhesion R² = 0.91, p = 0.014.

Overexpression of Tumor Necrosis Factor-Like Ligand 1 A in Myeloid Cells Aggravates Liver Fibrosis in Mice

Macrophages are the master regulator of the dynamic fibrogenesis-fibrosis resolution paradigm. TNF-like ligand 1 aberrance (TL1A) was found to be able to induce intestinal inflammation and fibrosis. Furthermore, significantly increased TL1A had been detected in liver tissues and mononuclear cells of patients with primary biliary cirrhosis (PBC). This study was to investigate the effect of myeloid cells with constitutive TL1A expression on liver fibrogenesis. We found that TL1A expressions in liver tissues and macrophages were significantly increased in mice with liver fibrosis induced by injection of carbon tetrachloride (CCl4). TL1A overexpression in myeloid cells induced liver function injury, accelerated the necrosis and apoptosis of hepatocytes, recruited macrophages, and promoted activation of hepatic stellate cells (HSCs) and fibrosis. In vitro results of our study showed that TL1A overexpression in macrophages promoted secretion of platelet-derived growth factor-BB (PDGF-BB), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β). Culturing macrophages with TL1A overexpression could accelerate the activation and proliferation of primary HSCs. These results indicated that constitutive TL1A expression in myeloid cells exacerbated liver fibrosis, probably through macrophage recruitment and secretion of proinflammatory and profibrotic cytokines.

Hepatocyte Ninjurin2 promotes hepatic stellate cell activation and liver fibrosis through the IGF1R/EGR1/PDGF-BB signaling pathway

BACKGROUND

Liver fibrogenesis is orchestrated by the paracrine signaling interaction between several resident cell types regulating the activation of hepatic stellate cells (HSCs). However, the molecular mechanisms underlying paracrine regulation are largely unknown. The aim of this study is to elucidate the role of Ninjurin2 in the crosstalk between hepatocytes and HSCs and better understand the implications of Ninjurin2 in liver fibrosis.

METHODS

Ninj2 knockout mice (Ninj2^-/-) and hepatocyte-specific Ninj2 overexpression mice (Ninj2^Hep-tg) were constructed and followed by the induction of liver fibrosis using methionine- and choline-deficient (MCD) diet. The relationship between Ninjurin2 and liver fibrosis phenotype was evaluated in vivo by measurement of fibrotic markers and related genes. We used an in vitro transwell cell co-culture model to examine the impact of Ninjurin2 in hepatocytes on the crosstalk to HSCs. The interaction of Ninjurin2 and IGF1R and the regulation of PI3K-AKT-EGR1 were analyzed in vivo and in vitro. Finally, an inhibitory Ninjurin2 peptide was injected intravenously via the tail vein to investigate whether inhibiting of Ninjurin2 cascade can attenuate MCD diet-induced liver fibrosis in mice.

RESULTS

We found that hepatic Ninjurin2 expression was significantly increased in fibrotic human liver and MCD diet-induced liver injury mouse models. In the mouse model, hepatocyte-specific overexpression of Ninj2 exacerbates MCD-induced liver fibrosis, while global Ninj2 knockout reverses the phenotype. To mimic hepatocyte-HSC crosstalk during liver fibrosis, we used co-culture systems containing hepatocytes and HSCs and determined that Ninjurin2 overexpression in hepatocytes directly activates HSCs in vitro. Mechanistically, Ninjurin2 directly interacts with insulin-like growth factor 1 receptor (IGF1R) and increases the hepatocyte secretion of the fibrogenic cytokine, platelet-derived growth factor-BB (PDGF-BB) through IGF1R-PI3K-AKT-EGR1 cascade. Inhibition of PDGFRB signaling in HSCs can abolish the profibrogenic effect of Ninjurin2. In addition, we demonstrated that a specific inhibitory Ninjurin2 peptide containing an N-terminal adhesion motif mitigates liver fibrosis and improves hepatic function in the mouse models by negatively regulating the sensitivity of IGF1R to IGF1 in hepatocytes.

CONCLUSION

Hepatic Ninjurin2 plays a key role in liver fibrosis through paracrine regulation of PDGF-BB/PDGFRB signaling in HSCs, and the results suggesting Ninjurin2 may be a potential therapeutic target.

Propranolol prevents liver cirrhosis by inhibiting hepatic stellate cell activation mediated by the PDGFR/Akt pathway

Propranolol is known to reduce portal pressure by decreasing blood flow to the splanchnic circulation and the liver. However, it is unknown if propranolol improves fibrogenesis and sinusoidal remodeling in the cirrhotic liver. The aim of this study was to investigate the therapeutic effects of propranolol on carbon tetrachloride (CCl₄)-induced liver fibrosis in a mouse model and the intrinsic mechanisms underlying those effects. In this study, a hepatic cirrhosis mouse model was induced by CCl₄ administration for 6 weeks. Propranolol was simultaneously administered orally in the experimental group. Liver tissue and blood samples were collected for histological and molecular analyses. LX-2 cells induced by platelet-derived growth factor-BB (PDGF-BB) were used to evaluate the anti-fibrogenic effect of propranolol in vitro. The results showed that treatment of mice with CCl₄ induced hepatic fibrosis, as evidenced by inflammatory cell infiltration, collagen deposition and abnormal vascular formation in the liver tissue. All these changes were significantly attenuated by propranolol treatment. Furthermore, we also found that propranolol inhibited PDGF-BB-induced hepatic stellate cell migration, fibrogenesis, and PDGFR/Akt phosphorylation. Taken together, propranolol might prevent CCl₄-induced liver injury and fibrosis at least partially through inhibiting the PDGF-BB-induced PDGFR/Akt pathway. The anti-fibrogenic effect of propranolol may support its status as a first-line treatment in patients with chronic liver disease.

Total flavonoids of Rhizoma Drynariae enhances CD31hiEmcnhi vessel formation and subsequent bone regeneration in rat models of distraction osteogenesis by activating PDGF‑BB/VEGF/RUNX2/OSX signaling axis

Total flavonoids of Rhizoma Drynariae (TFRD), extracted from the kidney‑tonifying Traditional Chinese medicine Rhizoma Drynariae, can be effective in treating osteoporosis, bone fractures and defects. However, the pharmacological effects of TFRD on the specific vessel subtype CD31hiEmcnhi during distraction osteogenesis (DO) remains unclear. The present study aimed to investigate the effects of TFRD on CD31hiEmcnhi vessels in a rat model of DO. In the present study, tibial DO models were established using 60 rats with a distraction rate of 0.2 mm per day for 20 days. Co‑immunofluorescence staining of CD31 and endomucin (Emcn) was conducted to determine CD31hiEmcnhi vessels. Radiographic, angiographic and histological analyses were performed to assess bone and vessel formation. Tube formation, alkaline phosphatase (ALP) and Von Kossa staining assays were performed to test angiogenesis of endothelial precursor cells (EPCs) and osteogenesis of bone marrow‑derived mesenchymal stem cells (BMSCs). Additionally, expression levels of platelet‑derived growth factor (PDGF)‑BB, VEGF, runt‑related transcription factor 2 (RUNX2) and Osterix (OSX) were determined by western blotting and reverse transcription‑quantitative PCR. The in vivo assays demonstrated that TFRD markedly promoted CD31hiEmcnhi vessel formation during DO, whereas PDGF‑BB neutralizing antibody suppressed vessel formation. Furthermore, the ALP, Von Kossa staining and tube formation assays indicated that TFRD notably elevated the angiogenic capacity of EPCs and osteogenic capacity of BMSCs under stress conditions, which was significantly suppressed by blocking PDGF‑BB. The protein and mRNA levels of PDGF‑BB, VEGF, RUNX2 and OSX were upregulated by TFRD, but downregulated by blocking PDGF‑BB. Thus, TFRD could facilitate CD31hiEmcnhi vessel formation and subsequently enhance angiogenic‑osteogenic coupling to regenerate bone defects during DO via the PDGF‑BB/VEGF/RUNX2/OSX signaling axis, which indicated that CD31hiEmcnhi vessels could be a potential novel therapeutic target for DO, and TFRD may represent a promising drug for promoting bone regeneration in DO by increasing CD31hiEmcnhi vessels.