Role of fibroblasts and fibroblast-derived growth factors in periprosthetic angiogenesis

Inhibitory effects of Formononetin on CoCrMo particle-induced osteoclast activation and bone loss through downregulating NF-κB and MAPK signaling

Wear particle-induced osteoclast over-activation is a major contributor to periprosthetic osteolysis and aseptic loosening, which can cause pathological bone loss and destruction. Hence, inhibiting excessive osteoclast-resorbing activity is an important strategy for preventing periprosthetic osteolysis. Formononetin (FMN) has been shown to have protective effects against osteoporosis, but no previous study has evaluated the effects of FMN on wear particle-induced osteolysis. In this study, we found that FMN alleviated CoCrMo alloy particles (CoPs)-induced bone loss in vivo and inhibited the formation and bone-resorptive function of osteoclasts in vitro. Moreover, we revealed that FMN exerted inhibitory effects on the expression of osteoclast-specific genes via the classical NF-κB and MAPK signaling pathways in vitro. Collectively, FMN is a potential therapeutic agent for the prevention and treatment of periprosthetic osteolysis and other osteolytic bone diseases.

Macrophage inhibits the osteogenesis of fibroblasts in ultrahigh molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis

Background

In the ultrahigh molecular weight polyethylene (UHMWPE) prosthetic environment, fibroblasts affected by wear particles have the capacity of osteogenesis to reduce osteolysis. We aimed to assess the effects of macrophages on the osteogenic capability of fibroblasts treated with UHMWPE wear particles.

Methods

The effect of different concentrations of UHMWPE (0, 0.01, 0.1, and 1 mg/ml, respectively) on macrophage proliferation were validated by MTT assay to determine the optimum one. The fibroblasts viability was further determined in the co-culture system of UHMWPE particles and macrophage supernatants. The experiment was designed as seven groups: (A) fibroblasts only; (B) fibroblasts + 1 mg/ml UHMWPE particles; and (C1–C5) fibroblasts + 1/16, 1/8, 1/4, 1/2, and 1/1 supernatants of macrophage cultures stimulated by 1 mg/ml UHMWPE particles vs. fibroblast complete media, respectively. Alizarin red staining was used to detect calcium accumulation. The expression levels of osteogenic proteins were detected by Western blot and ELISA, including alkaline phosphatase (ALP) and osteocalcin (OCN).

Results

The concentration of 0.1 mg/ml was considered as the optimum concentration for macrophage proliferation due to the survival rate and was highest among the four concentrations. Fibroblast viability was better in the group of fibroblasts + 1/16 ratio of macrophage supernatants stimulated by 1 mg/ml of UHMWPE particles than the other groups (1:8, 1:4, 1:2, 1:1). ALP and OCN expressions were significantly decreased in the group of fibroblasts + 1/4, 1/2, and 1/1 supernatants stimulated by 1 mg/ml of UHMWPE particles compared with other groups (1/8, 1/16) and the group of fibroblasts + 1 mg/ml UHMWPE (p < 0.5).

Conclusions

Macrophages are potentially involved in the periprosthetic osteolysis by reducing the osteogenic capability of fibroblasts treated with wear particles generated from UHMWPE materials in total hip arthroplasty.

Immunobiology of periprosthetic inflammation and pain following ultra-high-molecular-weight-polyethylene wear debris in the lumbar spine

INTRODUCTION

Wear debris-induced osteolysis is a common cause of arthroplasty failure in several joints including the knee, hip and intervertebral disc. Debris from the prosthesis can trigger an inflammatory response that leads to aseptic loosening and prosthesis failure. In the spine, periprosthetic pain also occurs following accumulation of wear debris through neovascularization of the disc. The role of the immune system in the pathobiology of periprosthetic osteolysis of joint replacements is debatable. Areas covered: We discussed the stimulation of pro-inflammatory and pro-protective and pro-regenerative pathways due to debris from the prosthetics. The balance between the two pathways may determine the outcome results. Also, the role of cytokines and immune cells in periprosthetic inflammation in the etiology of osteolysis is critically reviewed. Expert commentary: Therapies targeting the inflammatory process associated with ultra-high-molecular-weight polyethylene wear debris could reduce implant failure. Additionally, therapies targeting neovascularization of discs following arthroplasty could mitigate periprosthetic pain.

Prevascularization of natural nanofibrous extracellular matrix for engineering completely biological three-dimensional prevascularized tissues for diverse applications

Self-sustainability after implantation is one of the critical obstacles facing large engineered tissues. A preformed functional vascular network provides an effective solution for solving the mass transportation problem. With the support of mural cells, endothelial cells (ECs) can form microvessels within engineered tissues. As an important mural cell, human mesenchymal stem cells (hMSCs) not only stabilize the engineered microvessel network, but also preserve their multi-potency when grown under optimal culture conditions. A prevascularized hMSC/extracellular matrix (ECM) sheet fabricated by the combination of hMSCs, ECs and a naturally derived nanofibrous ECM scaffold offers great opportunity for engineering mechanically strong and completely biological three-dimensional prevascularized tissues. The objective of this study was to create a prevascularized hMSC/ECM sheet by co-culturing ECs and hMSCs on a nanofibrous ECM scaffold. Physiologically low oxygen (2% O2 ) was introduced during the 7 day hMSC culture to preserve the stemness of hMSCs and thereby their capability to secrete angiogenic factors. The ECs were then included to form microvessels under normal oxygen (20% O2 ) for up to 7 days. The results showed that a branched and mature vascular network was formed in the co-culture condition. Angiogenic factors vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and angiopoietin-1 (Ang-1) were significantly increased by low-oxygen culture of hMSCs, which further stabilized and supported the maturation of microvessels. A differentiation assay of the prevascularized ECM scaffold demonstrated a retained hMSC multi-potency in the hypoxia cultured samples. The prevascularized hMSC/ECM sheet holds great promise for engineering three-dimensional prevascularized tissues for diverse applications.

Periprosthetic UHMWPE Wear Debris Induces Inflammation, Vascularization, and Innervation After Total Disc Replacement in the Lumbar Spine

BACKGROUND

The pathophysiology and mechanisms driving the generation of unintended pain after total disc replacement (TDR) remain unexplored. Ultrahigh-molecular-weight polyethylene (UHMWPE) wear debris from TDRs is known to induce inflammation, which may result in pain.

QUESTIONS/PURPOSES

The purpose of this study was to determine whether (1) periprosthetic UHMWPE wear debris induces immune responses that lead to the production of tumor necrosis factor-α (TNFα) and interleukin (IL)-1ß, the vascularization factors, vascular endothelial growth factor (VEGF) and platelet-derived growth factor-bb (PDGFbb), and the innervation/pain factors, nerve growth factor (NGF) and substance P; (2) the number of macrophages is associated with the production of the aforementioned factors; (3) the wear debris-induced inflammatory pathogenesis involves an increase in vascularization and associated innervation.

METHODS

Periprosthetic tissues from our collection of 11 patients with contemporary TDRs were evaluated using polarized light microscopy to quantify UHMWPE wear particles. The major reason for revision (mean implantation time of 3 years [range, 1-6 years]) was pain. For control subjects, biopsy samples from four patients with degenerative disc disease with severe pain and autopsy samples from three normal patients with no history of back pain were also investigated. Immunohistochemistry and histology were used to identify secretory factors, macrophages, and blood vessels. Immunostained serial sections were imaged at ×200 magnification and using MATLAB and NIH ImageJ, a threshold was determined for each factor and used to quantify positive staining normalized to tissue sectional area. The Mann-Whitney U test was used to compare results from different patient groups, whereas the Spearman Rho test was used to determine correlations. Significance was based on p < 0.05.

RESULTS

The mean percent area of all six inflammatory, vascularization, and innervation factors was higher in TDR tissues when compared with normal disc tissues. Based on nonparametric data analysis, those factors showing the most significant increase included TNFα (5.17 ± 1.76 versus 0.05 ± 0.03, p = 0.02), VEGF (3.02 ± 1.01 versus 0.02 ± 0.002, p = 0.02), and substance P (4.15 ± 1.01 versus 0.08 ± 0.04, p = 0.02). The mean percent area for IL-1ß (2.41 ± 0.66 versus 0.13 ± 0.13, p = 0.01), VEGF (3.02 ± 1.01 versus 0.34 ± 0.29, p = 0.04), and substance P (4.15 ± 1.01 versus 1.05 ± 0.46, p = 0.01) was also higher in TDR tissues when compared with disc tissues from patients with painful degenerative disc disease. Five of the factors, TNFα, IL-1ß, VEGF, NGF, and substance P, strongly correlated with the number of wear particles, macrophages, and blood vessels. The most notable correlations included TNFα with wear particles (p < 0.001, ρ = 0.63), VEGF with macrophages (p = 0.001, ρ = 0.71), and NGF with blood vessels (p < 0.001, ρ = 0.70). Of particular significance, the expression of PDGFbb, NGF, and substance P was predominantly localized to blood vessels/nerve fibers.

CONCLUSIONS

These findings indicate wear debris-induced inflammatory reactions can be linked to enhanced vascularization and associated innervation/pain factor production at periprosthetic sites around TDRs. Elucidating the pathogenesis of inflammatory particle disease will provide information needed to identify potential therapeutic targets and treatment strategies to mitigate pain and potentially avoid revision surgery.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Chemokines Associated with Pathologic Responses to Orthopedic Implant Debris

Despite the success in returning people to health saving mobility and high quality of life, the over 1 million total joint replacements implanted in the US each year are expected to eventually fail after approximately 15-25 years of use, due to slow progressive subtle inflammation to implant debris compromising the bone implant interface. This local inflammatory pseudo disease state is primarily caused by implant debris interaction with innate immune cells, i.e., macrophages. This implant debris can also activate an adaptive immune reaction giving rise to the concept of implant-related metal sensitivity. However, a consensus of studies agree the dominant form of this response is due to innate reactivity by macrophages to implant debris danger signaling (danger-associated molecular pattern) eliciting cytokine-based and chemokine inflammatory responses. This review covers implant debris-induced release of the cytokines and chemokines due to activation of the innate (and the adaptive) immune system and how this leads to subsequent implant failure through loosening and osteolysis, i.e., what is known of central chemokines (e.g., IL-8, monocyte chemotactic protein-1, MIP-1, CCL9, CCL10, CCL17, and CCL22) associated with implant debris reactivity as related to the innate immune system activation/cytokine expression, e.g., danger signaling (e.g., IL-1β, IL-18, IL-33, etc.), toll-like receptor activation (e.g., IL-6, tumor necrosis factor α, etc.), bone catabolism (e.g., TRAP5b), and hypoxia responses (HIF-1α). More study is needed, however, to fully understand these interactions to effectively counter cytokine- and chemokine-based orthopedic implant-related inflammation.

Chronic inflammation in biomaterial-induced periprosthetic osteolysis: NF-κB as a therapeutic target

Biomaterial-induced tissue responses in patients with total joint replacement are associated with the generation of wear particles, which may lead to chronic inflammation and local bone destruction (periprosthetic osteolysis). Inflammatory reactions associated with wear particles are mediated by several important signaling pathways, the most important of which involves the transcription factor NF-κB. NF-κB activation is essential for macrophage recruitment and maturation, as well as the production of pro-inflammatory cytokines and chemokines such as TNF-α, IL-1β, IL-6 and MCP1. In addition, NF-κB activation contributes to osteoclast differentiation and maturation via RANK/RANKL signaling, which increases bone destruction and reduces bone formation. Targeting individual downstream cytokines directly (such as TNF-α or IL-1β) may not effectively prevent wear particle induced osteolysis. A more logical upstream therapeutic approach may be provided by direct modulation of the core IκB/IKKα/β/NF-κB signaling pathway in the local environment. However, the timing, dose and strategy for administration should be considered. Suppression of chronic inflammation via inhibition of NF-κB activity in patients with malfunctioning joint replacements may be an effective strategy to mitigate wear particle induced periprosthetic osteolysis.

Role and regulation of VEGF and its receptors 1 and 2 in the aseptic loosening of total hip implants

It was hypothesized that vascular endothelial growth factor (VEGF) in fibroblasts participates in aseptic loosening of total hip replacement (THR) implants. Therefore, osteoarthritic (OA) samples (n = 11) were compared with synovial membrane-like interface tissues from revision THR (n = 10). VEGF-A and its receptors were stained using streptavidin-immunoperoxidase method. Their regulation by hypoxia and cytokines were studied in cultured fibroblasts using quantitative real-time polymerase chain reaction (qRT-PCR). VEGFR1(+) lining cells (p < 0.01), stromal fibroblast-like cells (p = 0.001) and stromal macrophage-like cells (p < 0.05) were more numerous in rTHR than in OA. As to VEGFR2(+), only stromal fibroblast-like cells in rTHR outnumbered those found in OA (p < 0.05). VEGFRs in synovial fibroblasts were not affected by hypoxia, but VEGF increased 2.4-fold (p < 0.05). Interleukin-4 up-regulated VEGFR1 expression 23-fold. This is the first study to describe a difference between rTHR and OA in VEGF receptors, particularly VEGFR1. Hypoxia increased VEGF, but the VEGFR1 increase in the lining and stroma is probably IL-4 driven, in accordance with the M2-type macrophage dominance in interface tissues. VEGF/VEGFR system is also affected by hypoxia and may play a role in angiogenesis and bone pathology in aseptic loosening of total hip implants.

Sonic Hedgehog on microparticles and neovascularization

Neovascularization represents a pivotal process consisting in the development of vascular network during embryogenesis and adult life. Postnatally, it arises mainly through angiogenesis, which has physiological and pathological roles in health and disease. Blood vessel formation results as tightly regulated multistep process which needs coordination and precise regulation of the balance of proangiogenic and antiangiogenic factors. Sonic Hedgehog (SHH), a morphogen belonging to Hedgehog (HH) family proteins, is implicated in a remarkably wide variety of process, including vessel development. Recent evidence demonstrate that, in addition to the classic factors, microvesicles (MVs), both microparticles (MPs) and exosomes, small vesicles released distinct cellular compartments, are involved in modulation of neovascularization. MPs generated from T lymphocytes undergoing both activation and apoptosis harbor at their surface SHH and play a crucial role in modulation of neovascularization. They are able to modulate the different steps implicated in angiogenesis process in vitro and to enhance postischemic neovascularization in vivo. As the consequence, we suggest that the MPs carrying SHH contribute to generation of a vascular network and may represent a new therapeutic approach to treat pathologies associated with failed angiogenesis.

Tuning the dependency between stiffness and permeability of a cell encapsulating hydrogel with hydrophilic pendant chains

The mechanical stiffness of a hydrogel plays a significant role in regulating the phenotype of cells that adhere to its surface. However, the effect of hydrogel stiffness on cells cultured within its matrix is not well understood, because of the intrinsic inverse dependency between the permeability and stiffness of hydrogels. This study therefore presents an advanced biomaterial design strategy to decrease the inverse dependency between permeability and stiffness of a cell encapsulating hydrogel. Hydrogels were made by cross-linking poly(ethylene glycol) diacrylate (PEGDA) and poly(ethylene glycol) monoacrylate (PEGMA), with PEGMA acting as a pendant polymer chain. Increasing the mass fraction of PEGMA while keeping the total polymer concentration constant led to a decrease in the elastic modulus (E) of the hydrogel, but caused a minimal increase in the swelling ratio (Q). The size and hydrophobicity of the end groups of pendant PEG chains further fine tuned the dependency between Q and E of the hydrogel. Pure PEGDA hydrogels with varying molecular weights, which show the same range of E but a much greater range of Q, were used as a control. Fibroblasts encapsulated in PEGDA-PEGMA hydrogels displayed more significant biphasic dependencies of cell viability and vascular endothelial growth factor (VEGF) expression on E than those encapsulated in pure PEGDA hydrogels, which were greatly influenced by Q. Overall, the hydrogel design strategy presented in this study will be highly useful to better regulate the phenotype and ultimately improve the therapeutic efficacy of a wide array of cells used in various biology studies and clinical settings.

Metallosis following Knee Arthroplasty: A Histological and Immunohistochemical Study

Metallosis represents a rare and severe complication of knee replacement surgery. It is caused by the infiltration and accumulation of metallic debris into the peri-prosthetic structures, deriving from friction between metallic prosthetic components. In knee arthroplasty, this event generally occurs as a result of polyethylene wear of the tibial or metal-back patellar component. The real incidence of metallosis is still unknown, although it seems to be more frequent in hip than in knee arthroplasty. The metallic debris induces a massive release of cytokines from inflammatory cells, making a revision necessary whenever osteolysis and loosening of the prosthesis occur. We report four patients who underwent revision of their knee arthroplasty because of severe metallosis. In one of these patients, polyethylene wear had determined friction between the metal-back patellar component and the anterior portion of the femoral component. In the remaining three cases, metallosis was caused by friction between the femoral and tibial prosthetic metal surfaces, resulting from full-thickness wear of the tibial polyethylene. T lymphocytes were activated by metal particles present in periprosthetic membranes. In all patients, one-stage revision was necessary, with rapid pain disappearance and a complete functional recovery of the knee joint.

Total ankle arthroplasty in the rheumatoid patient

Total ankle replacement in the rheumatoid patient is a feasible and effective treatment for ankle arthritis. The benefits of ankle prosthesis are good pain relief, acceptable function, and patient satisfaction. It is a joint-sparing procedure for restoring functionality. All investigators of total ankle replacement feel that, as clinicians gain experience with the procedure and related products, difficulties and risks associated with the procedure will decline. Following an early history of failure and poor patient satisfaction, more recent results have shown promise.

Different apoptosis modalities in periprosthetic membranes

This study reports on an investigation into apoptotic and proliferation signals in leukocyte and membrane fibroblasts in periprosthetic membranes collected during revision surgery for loosened total hip joint arthroplasty. Cementless and cemented prosthesis were studied under both aseptic and septic conditions. Fluorescence colocalization immunohistochemistry and colorimetric immunohistochemistry were used to investigate cell death signals. In aseptic cementless prosthesis macrophages and membrane fibroblasts show high bax signal, implying the occurrence of toxic/oxidative cell death caused by the debris of titanium alloy metal implant. Instead in aseptic cemented prosthesis only a moderate number of apoptotic leukocytes were observed, whilst the fibroblasts were affected by a diffuse apoptotic-like cell death, the Co-Cr ions debris released from cemented stem, may be at basis of apoptotic cell death induction. Furthermore cement debris is recognized to induce macrophages to produce cytokine, that may be responsible for the cell death observed and implant failure. The septic environment seems to protect leukocytes cell death. Septic cementless prosthesis showed only a few apoptotic leukocytes, instead fibroblasts remain affected by cell death signals. Similarly in septic cemented prosthesis, scanty apoptotic leukocytes were detected, whereas membrane fibroblasts showed an increase in proliferation index (Ki-67) along with caspase-3 activation. These findings indicate some kind of caspase-3 involvement in tissue proliferation, rather than in cell death pathway. Apoptotic periprosthetic sites have been interpreted as signs of inflammation resolution and normal tissue turnover. Nevertheless apoptosis may also be a sign of cell renewal associated to tissue proliferation.

Cyclooxygenase-2 mediates dialysate-induced alterations of the peritoneal membrane

During peritoneal dialysis (PD), exposure of the peritoneal membrane to nonphysiologic solutions causes inflammation, ultimately leading to altered structure and function. Myofibroblasts, one of the cell types that contribute to dysfunction of the peritoneal membrane, can originate from mesothelial cells (MCs) by epithelial-to-mesenchymal transition (EMT), a process that has been associated with an increased rate of peritoneal transport. Because cyclooxygenase-2 (COX-2) is induced by inflammation, we studied the role of COX-2 in the deterioration of the peritoneal membrane. We observed that nonepithelioid MCs found in peritoneal effluent expressed higher levels of COX-2 than epithelioid MCs. The mass transfer coefficient for creatinine correlated with MC phenotype and with COX-2 levels. Although COX-2 was upregulated during EMT of MCs in vitro, COX-2 inhibition did not prevent EMT. In a mouse model of PD, however, COX-2 inhibition with Celecoxib resulted in reduced fibrosis and in partial recovery of ultrafiltration, outcomes that were associated with a reduction of inflammatory cells. Furthermore, PD fluid with a low content of glucose degradation products did not induce EMT or COX-2; the peritoneal membranes of mice treated with this fluid showed less worsening than mice exposed to standard fluid. In conclusion, upregulation of COX-2 during EMT may mediate peritoneal inflammation, suggesting COX-2 inhibition as a potential strategy to ameliorate peritoneal deterioration in PD patients.

Cytokine-controlled RANKL and osteoprotegerin expression by human and mouse synovial fibroblasts: fibroblast-mediated pathologic bone resorption

OBJECTIVE

To determine whether proinflammatory cytokine treatment or the complete absence of select cytokines modulates the expression of RANKL and osteoprotegerin (OPG) in synovial fibroblasts.

METHODS

Fibroblasts were isolated from normal and rheumatoid human synovium and from normal or arthritic joints of wild-type and cytokine gene-deficient (interleukin-4-knockout [IL-4 (-/-)] and interferon-gamma-knockout [IFNgamma (-/-)]) mice. Fibroblasts were stimulated with proinflammatory cytokines (tumor necrosis factor alpha [TNFalpha], IL-1beta, and IL-17) or antiosteoclastogenic cytokines (IL-4 and IFNgamma), alone or in combination, and the expression of RANKL and OPG was measured.

RESULTS

Proinflammatory cytokine-stimulated fibroblasts from rheumatoid and arthritic mouse joints expressed higher levels of RANKL and OPG than those from normal joints. IL-4 suppressed RANKL expression and increased OPG expression, IFNgamma reduced the production of both RANKL and OPG, and IL-17 had only a modest effect on the expression of RANKL or OPG. Additive effects of combination treatment (TNFalpha/IL-17 or IL-1beta/IL-17) were observed only in the human system. Extensive destruction was observed in the arthritic joints of IL-4 (-/-) mice, with a corresponding upward shift of the RANKL:OPG ratios. However, an IL-17 deficiency did not attenuate arthritis or reduce bone resorption.

CONCLUSION

Proinflammatory cytokines induce the expression of RANKL and OPG in both human and murine synovial fibroblasts. The RANKL:OPG ratios are shifted in favor of bone protection by IL-4 treatment, and, to a lesser extent, by IFNgamma treatment. Unexpectedly, an IL-17 deficiency alone does not induce reduced inflammatory bone destruction. Our results suggest that synovial fibroblasts may significantly contribute to bone resorption through modulation of RANKL and OPG production in a cytokine-rich milieu of inflamed joints.