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Effects of aging on osteogenic response and heterotopic ossification following burn injury in mice.

ABSTRACT: Heterotopic ossification (HO) is a common and debilitating complication of burns, traumatic brain injuries, and musculoskeletal trauma and surgery. Although the exact mechanism of ectopic bone formation is unknown, mesenchymal stem cells (MSCs) capable of osteogenic differentiation are known to play an essential role. Interestingly, the prevalence of HO in the elderly population is low despite the high overall occurrence of musculoskeletal injury and orthopedic procedures. We hypothesized that a lower osteogenicity of MSCs would be associated with blunted HO formation in old compared with young mice. In vitro osteogenic differentiation of adipose-derived MSCs from old (18-20 months) and young (6-8 weeks) C57/BL6 mice was assessed, with or without preceding burn injury. In vivo studies were then performed using an Achilles tenotomy with concurrent burn injury HO model. HO formation was quantified using ?CT scans, Raman spectroscopy, and histology. MSCs from young mice had more in vitro bone formation, upregulation of bone formation pathways, and higher activation of Smad and nuclear factor kappa B (NF-?B) signaling following burn injury. This effect was absent or blunted in cells from old mice. In young mice, burn injury significantly increased HO formation, NF-?B activation, and osteoclast activity at the tenotomy site. This blunted, reactive osteogenic response in old mice follows trends seen clinically and may be related to differences in the ability to mount acute inflammatory responses. This unique characterization of HO and MSC osteogenic differentiation following inflammatory insult establishes differences between age populations and suggests potential pathways that could be targeted in the future with therapeutics.

SUBMITTER: Peterson JR

PROVIDER: S-EPMC4291203 | biostudies-other | 2015 Jan

REPOSITORIES: biostudies-other

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Effects of aging on osteogenic response and heterotopic ossification following burn injury in mice.

Peterson Jonathan R JR Eboda Oluwatobi N ON Brownley R Cameron RC Cilwa Katherine E KE Pratt Lauren E LE De La Rosa Sara S Agarwal Shailesh S Buchman Steven R SR Cederna Paul S PS Morris Michael D MD Wang Stewart C SC Levi Benjamin B

Stem cells and development 20150101 2

Heterotopic ossification (HO) is a common and debilitating complication of burns, traumatic brain injuries, and musculoskeletal trauma and surgery. Although the exact mechanism of ectopic bone formation is unknown, mesenchymal stem cells (MSCs) capable of osteogenic differentiation are known to play an essential role. Interestingly, the prevalence of HO in the elderly population is low despite the high overall occurrence of musculoskeletal injury and orthopedic procedures. We hypothesized that a ...[more]

PMID: 25122460

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Project description:ObjectiveTo demonstrate the pro-osteogenic effect of burn injury on heterotopic bone formation using a novel burn ossicle in vivo model.BackgroundHeterotopic ossification (HO), or the abnormal formation of bone in soft tissue, is a troubling sequela of burn and trauma injuries. The exact mechanism by which burn injury influences bone formation is unknown. The aim of this study was to develop a mouse model to study the effect of burn injury on heterotopic bone formation. We hypothesized that burn injury would enhance early vascularization and subsequent bone formation of subcutaneously implanted mesenchymal stem cells.MethodsMouse adipose-derived stem cells were harvested from C57/BL6 mice, transfected with a BMP-2 adenovirus, seeded on collagen scaffolds (ossicles), and implanted subcutaneously in the flank region of 8 adult mice. Burn and sham groups were created with exposure of 30% surface area on the dorsum to 60°C water or 30°C water for 18 seconds, respectively (n = 4/group). Heterotopic bone volume was analyzed in vivo by micro-computed tomography for 3 months. Histological analysis of vasculogenesis was performed with platelet endothelial cell adhesion molecule staining. Osteogenic histological analysis was performed by Safranin O, Picrosirius red, and aniline blue staining. Qualitative analysis of heterotopic bone composition was completed with ex vivo Raman spectroscopy.ResultsSubcutaneously implanted ossicles formed heterotopic bone. Ossicles from mice with burn injuries developed significantly more bone than sham control mice, analyzed by micro-computed tomography at 1, 2, and 3 months (P < 0.05), and had enhanced early and late endochondral ossification as demonstrated by Safranin O, Picrosirius red, and aniline blue staining. In addition, burn injury enhanced vascularization of the ossicles (P < 0.05). All ossicles demonstrated chemical composition characteristic of bone as demonstrated by Raman spectroscopy.ConclusionsBurn injury increases the predilection to osteogenic differentiation of ectopically implanted ossicles. Early differences in vascularity correlated with later bone development. Understanding the role of burn injury on heterotopic bone formation is an important first step toward the development of treatment strategies aimed to prevent unwanted and detrimental heterotopic bone formation.

Project description:We previously reported the development of a new acquired neurogenic HO (NHO) mouse model, combining spinal cord transection (SCI) and chemical muscle injury. Pathological mechanisms responsible for ectopic osteogenesis after central neurological damage are still to be elucidated. In this study, we first hypothesized that peripheral nervous system (PNS) might convey pathological signals from injured spinal cord to muscles in NHO mouse model. Secondly, we sought to determine whether SCI could lead to intramuscular modifications of BMP2 signaling pathways. Twenty one C57Bl6 mice were included in this protocol. Bilateral cardiotoxin (CTX) injection in hamstring muscles was associated with a two-stage surgical procedure, combining thoracic SCI with unilateral peripheral denervation. Volumes of HO (Bone Volume, BV) were measured 28 days after surgery using micro-computed tomography imaging techniques and histological analyses were made to confirm intramuscular osteogenesis. Volume comparisons were conducted between right and left hind limb of each animal, using a Wilcoxon signed rank test. Quantitative polymerase chain reaction (qPCR) was performed to explore intra muscular expression of BMP2, Alk3 and Id1. Nineteen mice survive the complete SCI and peripheral denervation procedure. When CTX injections were done right after surgery (n = 7), bilateral HO were detected in all animals after 28 days. Micro-CT measurements showed significantly increased BV in denervated paws (1.47 mm3 +/- 0.5) compared to contralateral sides (0.56 mm3 +/-0.4), p = 0.03. When peripheral denervation and CTX injections were performed after sham SCI surgery (n = 6), bilateral HO were present in three mice at day 28. Quantitative PCR analyses showed no changes in intra muscular BMP2 expression after SCI as compared to control mice (shamSCI). Peripheral denervation can be reliably added to spinal cord transection in NHO mouse model. This new experimental design confirms that neuro inflammatory mechanisms induced by central or peripheral nervous system injury plays a key role in triggering ectopic osteogenesis.

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Effects of aging on osteogenic response and heterotopic ossification following burn injury in mice.

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Effects of aging on osteogenic response and heterotopic ossification following burn injury in mice.

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