Recurrence of heterotopic ossification after removal in patients with traumatic brain injury: A systematic review

AbstractObjectiveA systematic review of the literature to determine whether in patients with neurological heterotopic ossification (NHO) after traumatic brain injury, the extent of the neurological sequelae, the timing of surgery and the extent of the initial NHO affect the risk of NHO recurrence.Data sourcesWe searched MEDLINE via PubMed and Cochrane library for articles published up to June 2015. Results were compared with epidemiological studies using data from the BANKHO database of 357 patients with central nervous system (CNS) lesions who underwent 539 interventions for troublesome HO.ResultsA large number of studies were published in the 1980s and 1990s, most showing poor quality despite being performed by experienced surgical teams. Accordingly, results were contradictory and practices heterogeneous. Results with the BANKHO data showed troublesome NHO recurrence not associated with aetiology, sex, age at time of CNS lesion, multisite HO, or “early” surgery (before 6months). Equally, recurrence was not associated with neurological sequelae or disease extent around the joint.ConclusionsThe recurrence of NHO is not affected by delayed surgery, neurological sequelae or disease extent around the joint. Surgical excision of NHO should be performed as soon as comorbid factors are under control and the NHO is sufficiently constituted for excision

Characterization of the signaling pathways leading to ectopic osteogenesis after spinal cord injury in a mouse model of neurogenic heterotopic ossification

La morbi-mortalité associée aux lésions vertébro-médullaires traumatiques (SCI) reste significative malgré les progrès réalisés en matière de prise en charge médicale et rééducative. Des complications secondaires musculosquelettiques, spasticité, amyotrophie ou ossifications hétérotopiques (HO), continuent de grever le pronostic fonctionnel de ces patients faute de thérapies préventives efficaces. Si les perturbations neuro-immunes et neuroendocrines engendrées par les lésions du système nerveux central (CNS) font l’objet d’un intérêt croissant, leur rôle dans la perte de l’homéostasie tissulaire, en particulier au niveau du muscle strié squelettique demeure mal compris.L’objectif de ce travail était de caractériser la nature et la cinétique de l’effet pro-ostéogénique observé après SCI dans un modèle murin d’HO neurogènes (NHO). Différentes procédures expérimentales in-vivo ont été utilisées pour évaluer l’influence de la systématisation et de la sévérité de l’atteinte neurologique sur la formation des NHO, ainsi que pour préciser la chronologie des processus physiopathologiques impliqués. Des techniques d’ablation pharmacologiques et de quantification moléculaire par qPCR et ELISA ont permis de mieux comprendre le rôle des hormones de stress et des neuropeptides nociceptifs dans ce modèle.Les principaux résultats obtenus ont mis en évidence l’aspect multiphasique des perturbations induites par la lésion médullaire sur le muscle en cours de régénération. Le relargage rapide de neuropeptides crée des conditions micro-environnementales altérant la clairance des débris nécrotiques et favorisant l’expression ectopique du programme ostéogénique. Le processus d’ossification intra-membraneuse s’organisant autour des débris minéralisés est secondairement régulé par une signalisation adrénergique spécifique impliquant les récepteurs beta de type1.Au-delà de l’amélioration de la compréhension mécanistique d’un modèle préclinique d’HO neurogène, ce travail supporte le développement de stratégies thérapeutiques séquentielles et ciblées dans la prévention des complications secondaires chez le patient blessé médullaire.Despite promising advances in experimental therapies and robotic rehabilitation, traumatic spinal cord injury (SCI) is still a common cause of potentially life-threatening and/or severely disabling complications. Besides the loss of motor function, SCI patients can secondarily experience muscle spasticity, atrophy and heterotopic ossifications (HO) that negatively impact on both their recovery and quality of life. Increasing evidence suggests that neuro-immune and/or neuro-metabolic dysfunction after SCI may interfere with peripheral organ homeostasis and tissue repair. Whether this can also drive the development of ectopic osteogenesis remains unknown.In this work, we investigated the nature and the kinetics of SCI-induced effects that derail the fate of muscle progenitors in a mouse model of acquired neurogenic HO. We conducted different types of spinal cord lesions to explore the influence of neurological injury level and severity. We then clarified the role of neuropeptides and stress hormones signals in the development of NHO through tissular quantification (ELISA, qPCR), surgical approaches (e.g. adrenalectomy), pharmacologic studies and chemical ablation.Our main results are that spinal cord lesions can interfere with muscular regeneration at various levels of a complex multi-steps process, beginning within the first hours of combined insults. This cascade of interconnected events starts with immediate and critical metabolic changes affecting the endogenous stem/progenitor cell niche. Secondarily, plasmatic release of epinephrine further impairs muscle regeneration, promoting the development of an ectopic intramembranous ossification process.Better understanding of the kinetics governing SCI-induced deregulations in skeletal muscle maintenance is crucial to develop effective preventive strategies against wasting disuse and aberrant repair in paralysed patients. Given the unravelled importance of timing, sequential targeted therapies could prove a promising path forward to maximally reduce and/or prevent NHO in at-risk patients

Ostéogenèse ectopique associée aux traumatismes vertébro-médullaires : étude des voies d’induction dans un modèle murin d’ossification hétérotopiques neurogènes

Despite promising advances in experimental therapies and robotic rehabilitation, traumatic spinal cord injury (SCI) is still a common cause of potentially life-threatening and/or severely disabling complications. Besides the loss of motor function, SCI patients can secondarily experience muscle spasticity, atrophy and heterotopic ossifications (HO) that negatively impact on both their recovery and quality of life. Increasing evidence suggests that neuro-immune and/or neuro-metabolic dysfunction after SCI may interfere with peripheral organ homeostasis and tissue repair. Whether this can also drive the development of ectopic osteogenesis remains unknown.In this work, we investigated the nature and the kinetics of SCI-induced effects that derail the fate of muscle progenitors in a mouse model of acquired neurogenic HO. We conducted different types of spinal cord lesions to explore the influence of neurological injury level and severity. We then clarified the role of neuropeptides and stress hormones signals in the development of NHO through tissular quantification (ELISA, qPCR), surgical approaches (e.g. adrenalectomy), pharmacologic studies and chemical ablation.Our main results are that spinal cord lesions can interfere with muscular regeneration at various levels of a complex multi-steps process, beginning within the first hours of combined insults. This cascade of interconnected events starts with immediate and critical metabolic changes affecting the endogenous stem/progenitor cell niche. Secondarily, plasmatic release of epinephrine further impairs muscle regeneration, promoting the development of an ectopic intramembranous ossification process.Better understanding of the kinetics governing SCI-induced deregulations in skeletal muscle maintenance is crucial to develop effective preventive strategies against wasting disuse and aberrant repair in paralysed patients. Given the unravelled importance of timing, sequential targeted therapies could prove a promising path forward to maximally reduce and/or prevent NHO in at-risk patients.La morbi-mortalité associée aux lésions vertébro-médullaires traumatiques (SCI) reste significative malgré les progrès réalisés en matière de prise en charge médicale et rééducative. Des complications secondaires musculosquelettiques, spasticité, amyotrophie ou ossifications hétérotopiques (HO), continuent de grever le pronostic fonctionnel de ces patients faute de thérapies préventives efficaces. Si les perturbations neuro-immunes et neuroendocrines engendrées par les lésions du système nerveux central (CNS) font l’objet d’un intérêt croissant, leur rôle dans la perte de l’homéostasie tissulaire, en particulier au niveau du muscle strié squelettique demeure mal compris.L’objectif de ce travail était de caractériser la nature et la cinétique de l’effet pro-ostéogénique observé après SCI dans un modèle murin d’HO neurogènes (NHO). Différentes procédures expérimentales in-vivo ont été utilisées pour évaluer l’influence de la systématisation et de la sévérité de l’atteinte neurologique sur la formation des NHO, ainsi que pour préciser la chronologie des processus physiopathologiques impliqués. Des techniques d’ablation pharmacologiques et de quantification moléculaire par qPCR et ELISA ont permis de mieux comprendre le rôle des hormones de stress et des neuropeptides nociceptifs dans ce modèle.Les principaux résultats obtenus ont mis en évidence l’aspect multiphasique des perturbations induites par la lésion médullaire sur le muscle en cours de régénération. Le relargage rapide de neuropeptides crée des conditions micro-environnementales altérant la clairance des débris nécrotiques et favorisant l’expression ectopique du programme ostéogénique. Le processus d’ossification intra-membraneuse s’organisant autour des débris minéralisés est secondairement régulé par une signalisation adrénergique spécifique impliquant les récepteurs beta de type1.Au-delà de l’amélioration de la compréhension mécanistique d’un modèle préclinique d’HO neurogène, ce travail supporte le développement de stratégies thérapeutiques séquentielles et ciblées dans la prévention des complications secondaires chez le patient blessé médullaire

Local and systemic factors drive ectopic osteogenesis in regenerating muscles of spinal-cord-injured mice in a lesion-level-dependent manner

International audienceNeuroimmune dysfunction is thought to promote the development of several acute and chronic complications in spinal cord injury (SCI) patients. Putative roles for adrenal stress hormones and catecholamines are increasingly being recognized, yet how these adversely affect peripheral tissue homeostasis and repair under SCI conditions remains elusive. Here, we investigated their influence in a mouse model of SCI with acquired neurogenic heterotopic ossification. We show that spinal cord lesions differentially influence muscular regeneration in a level-dependent manner and through a complex multi-step process that creates an osteopermissive environment within the first hours of injury. This cascade of events is shown to critically involve adrenergic signals and drive the acute release of the neuropeptide, substance P. Our findings generate new insights into the kinetics and processes that govern SCI-induced deregulations in skeletal muscle homeostasis and regeneration, thereby aiding the development of sequential therapeutic strategies that can prevent or attenuate neuromusculoskeletal complications in SCI patients

Peripheral denervation participates in heterotopic ossification in a spinal cord injury model

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

Anterior approach of femoral nerve.

<p>A: skin incision through inguinal fold. B: femoral neuro-vascular bundle exposure. C: proximal part of femoral nerve laying over psoas muscle.</p

Sciatic nerve excision procedure by posterior approach.

<p>A: skin incision over posterior surface of proximal hind limb exposes superficial muscular layers [gluteus maximus (1) and biceps femoralis (2)]. B: Biceps femoralis retraction allows sciatic nerve identification. C: Pelvic insertion of gluteus maximus muscle is freed to expose deep muscular layers [gluteus medius and gluteus minimus (3)]. D & E: Greater trochanter (4) exposure after deep muscles retraction. Sciatic nerve is followed throughout its course towards the sciatic notch. E: Proximal cut of sciatic nerve. F: Divisional branches of the sciatic nerve to hamstring muscles.</p

Muscular samples after SCI and CTX injection.

<p>HES staining showed bone matrix (1), osteocytes (white arrow) mineralized nodules (2), regenerated muscular fibers (3) infiltration of inflammatory cells (4).</p

QPCR analyses of BMP signaling pathway in muscular samples of C57bl6 mice, 18 hours after spinal cord injury (SCI) or sham surgery (sham SCI).

<p>Studied genes were BMP2, Alk3 (encoding BMP type 1 receptor) and ID1 (encoding inhibitor Of DNA Binding 1, HLH Protein). For each gene, presented results are the means of qPCR triplicate results, reported to housekeeping genes 18S and GADPH. p values were 0.08 and 0.76 respectively for BMP2/18S and BMP2/GADPH; 0.05 and 0.9 respectively for AlK3/18S and AlK3/GADPH; 0.8 and 0.15 respectively for ID1/18S and ID1/GADPH.</p