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212 ACAM, 2019, volume 9, issue 6

Annals of Clinical and Analytical Medicine

The role of TNF‐α in fracture in children

Muhannad Mohammed Alnefaie 1*, Abdulaziz Abdullah Alosaimi 1, Abdullah Abdulatif Hijr Allahiany2, Adel Awwadh Almutairy 3 (1) Taif university, Children Hospital, Saudi Arabia (2) Hera General Hospial, Saudi Arabia (3) College of Medicine, Umm Al-Qura University, Saudi Arabia

Received date 24/8/2019; revised date 16/10/2019; accepted date 3/11/2019

*Corresponding author, Email: [email protected] Abstract

In the inflammatory stage, immune system provides the fracture site with many of immune cells as and other types, which release pro-inflammatory cytokines as -alpha (TNF-α), interlukine-1(IL-1) and interlukine-6 (IL-6). In the present review we attempt to elaborate the role of TNF-α in fracture healing. The electronic search conducted in MEDLINE and EBASE databases which resulted in 115 studies. A total of 115 studies were screened by reading their title and abstracts, 112 studies of them were irrelevant and only three studies were included in this review. Local treatment with TNF-α at low concentration displayed pivotal role in enhancing fracture healing in human fracture fragments and in murine model fracture.

Keywords: Immune, Growth factor, Bone, Fracture, Children

Introduction fracture. Moreover, the repair of damaged bone, requires coordinating participations of hematopoietic Fractures represent one of the major clinical and many types of immune cells in the injured tissue problems in the world [1]. Fracture healing has been marrow, which conjunct with the vascular and known as complex process of repair bone and skeletal cells to regenerate the damaging in bone [4, surrounded tissues by primary bone healing (rigid 5]. In the inflammatory stage, immune system ) and secondary bone healing which provides the fracture site with many of immune cells contains three main stages; inflammation, repairing as macrophages and other types, which release pro- and remodeling [2, 3]. As other wound repairing inflammatory cytokines as tumor necrosis factor- responses, fracture healing induces the innate alpha (TNF-α), interlukine-1(IL-1) and interlukine-6 immune system to release immune cells to the site of (IL-6) [6]. It was reported that, these pro- ACAM, 2019, volume 9, issue 2 213 inflammatory cytokines improved synthesis of A total of 115 studies were screened by reading their extracellular matrix, stimulating angiogenesis and title and abstracts, 112 studies of them were endogenous fibro-genic cells recruiting in the injury irrelevant and only three studies [1, 16, 17] were site [6, 7]. Pro-inflammatory cytokine TNF-α was included in this review. In general sample size ranged reported as central mediator in inflammation between 4 to 358 samples. The study of Glass, et al. response. TNF-α has two receptors TNFR1 and [1] reported that, TNF-α displayed pivotal role in TNFR2, and their role in bone repair was investigated enhancing fracture healing in human fracture bone [5, 8]. It’s reported that, TNFR1 has ability to fragments and in open tibial fractures in a murine mediate inflammatory function of TNF-α which model. In murine model (in vivo), addition of 1 induces the inflammatory [9]. While, ng/mL of TNF-α at the fracture site accelerated TNFR2 has beneficial effect in anti-inflammatory healing, also in human fracture bone fragments, TNF- reaction [10]. David and Schett, [11] revealed that all α promotes muscle-derived stromal cells (MDSC) functions of TNF-α in bone are depending on migration and osteogenic differentiation at low TNFR1. The role of TNF-α in fracture healing was concentrations in vitro. In addition to these results extensively studied. Previous studies recorded they revealed that, TNF-α had inhibitory effect on important regulatory roles for TNF-α in healing when used at high concentrations. remodeling, homeostasis [12, 13]. Recently, The same results were recorded by Chan, et al [16] nonessential regulating for TNF-α in bone when their results showed that, the local treatment of remodeling was reported by David and Schett,[11] rhTNF at low dose (1 ng/mL) improved fracture and TNF-α caused decreasing in (derived healing but in the early phase of repair (within 24 h from monocyte and ) activity and of injury) in fragility fractures murine model. increasing in differentiation which Addition of rhTNF recorded positive effect on accelerate the synthesis and calcification of bone neutrophil recruitment and promoted recruitment of [11]. Also, Abbas et al [14] displayed that TNF α monocytes through CCL2 production. At the same inhibited pre osteoblast activity via its TNFR1 time, their results demonstrated that, anti-TNF and receptor. Furthermore, Timmen et al. [15] concluded neutrophils depletion or inhibition of chemokine that from their results, the highly levels of TNF-α receptor CCR2 impaired fracture healing. during chronic inflammation have a negative effect on fracture healing. In the present review we attempt to elaborate the role of TNF-α in fracture healing. The study of Kayal, et al. [17] showed negative effect of diabetes on fracture healing. Diabetes induced an up-regulation of proapoptotic genes during the transition phase from to bone in fracture Methods healing. Their results revealed that, diabetes caused increasing of apoptosis by over The electronic search conducted in MEDLINE and production of TNF-α, the later stimulates EBASE databases using keywords such as “fracture, chondrocyte apoptosis and up-regulates apoptotic TNF-a AND, healing and union) which resulted in genes levels through FOXO1 activation. 115 studies. The eligible articles that aimed to study the role of TNF-α in fracture healing in children were screened. The irrelevant articles were excluded and Discussion the results were synthesized only for 3 eligible studies. as complex organs represent the main supporting system for animal and human bodies, Results more than that there are many functions for skeletal system as hematopoiesis, regulation and storage The search on the role of TNF-α on the fracture minerals and facilitation of locomotion [18]. healing was carried out in PMC in the last ten years. Therefore, bone repair is an urgent needed must be 214 ACAM, 2019, volume 9, issue 6 done rapidly and accurately when bone undergoes that, fracture healing was inhibited by daily many problems as open fractures, fragility fractures administration of high dose of TNF (400 (osteoporotic) and diabetic fracture [1]. During micrograms/kg) which caused inhibition of fracture healing, a cascade of events is involved; differentiation for mesenchymal cells into inflammatory reaction is the first one of them, occurs . The positive role of low doses of within minutes of bone injury [19]. In this stage, TNF-α in fracture healing is by recruitment and immune response provides the fracture site with osteogenic differentiation of muscle-derived immune cells as macrophages and other types, which mesenchymal stromal cells which induced callus release many types of pro-inflammatory cytokines as formation during fracture repair [1]. Furthermore, tumor necrosis factor-alpha (TNF-α) [6]. In this TNF-α could improve fracture healing when used at systematic review we summarize the role of TNF-α low concentration in early phase of fracture repair in bone fracture healing. Local treatment with TNF-α [16]. These results agree with that reported by [21, at low concentration displayed pivotal role in 22] when their results showed that, TNF-α promoted enhancing fracture healing in human fracture bone osteogenic differentiation of derived in fragments and in murine model fracture. TNF-α was a time and dose dependent manner. The other able to promote muscle-derived stromal cells included study in this review was by Kayal, et al. migration and osteogenic differentiation which [17] which revealed negative effect of TNF-α in accelerate fracture healing Glass, et al. [1]. These diabetes fracture healing. This effect was by over results were confirmed by Chan, et al [16] when their production of TNF-α, which stimulates chondrocyte results recorded that, low dose (1 ng/mL) of rhTNF apoptosis and up-regulates apoptotic genes levels by improved fracture healing but in the early phase of FOXO1 activation. In summary we can conclude that repair in fragility fractures murine model. This effect from consistence results obtained of included studies of rhTNF was by promoting recruitment of in this review which proved the local treatment of monocytes through CCL2 production. The studies of TNF-α at low concentration in early phase of fracture [1] and [16] were in harmony when they reported enhanced bone fracture healing. that, the low levels of TNF-α improved fracture repair and the high levels of TNF-α had inhibitory Conclusions effect on fracture healing. This was reported previously; Timmen et al. [15] Indicated to that, the Local treatment with TNF-α at low highly levels of TNF-α during chronic inflammation concentration displayed pivotal role in had negative effect on fracture healing. Also, enhancing fracture healing in human fracture Hashimoto [20] studied the effects of TNF on the bone fragments and in murine model fracture healing of fractured ribs in rats. Their results showed

Acknowledgments

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