Bone biomarkers in patients with chronic traumatic spinal cord injury

Multifaceted Pathophysiology and Secondary Complications of Chronic Spinal Cord Injury: Focus on Pressure Injury

Background/Objectives: Spinal cord injury (SCI) is a complex medical condition with widespread effects that extend beyond motor and sensory impairments. In addition to nervous system damage, SCI patients experience various secondary complications, including vascular dysfunction, altered body composition, and metabolic disturbances. Among the most common secondary pathologies is the development of pressure injuries (PIs), chronic wounds that significantly affect quality of life and can be challenging to treat. Understanding the physiological and cellular mechanisms behind these complications is crucial for improving care and therapeutic outcomes. Methods: We conducted a comprehensive literature search in PubMed, Scopus, and Google Scholar using keywords related to spinal cord injury, pressure ulcer/pressure injuries, metabolic and vascular dysfunction, biomechanics, and regenerative therapies. Studies were selected based on their relevance to the pathophysiology, risk factors, and novel therapeutic approaches for PIs in SCI patients. Results: Vascular dysfunction, characterized by impaired blood flow and microcirculatory issues, predisposes SCI patients to ischemia and tissue necrosis, particularly in areas subjected to prolonged pressure. Additionally, changes in body composition, such as increased adiposity and muscle atrophy, further compromise tissue integrity and healing capacity. The inflammatory response, mediated by cytokines such as IL-1, IL-6, and TNF-α, exacerbates these effects by sustaining a pro-inflammatory environment that delays the transition of macrophages to the M2 phenotype, critical for wound healing. External factors, such as poor nutrition, infections, and immobility, also play a significant role in worsening the wound healing process. Conclusions: Chronic SCI induces a cascade of physiological changes that predispose patients to the development of PIs and complicate their recovery. The intricate interplay of vascular, metabolic, and inflammatory responses creates a hostile environment for wound healing. A deeper understanding of these systemic effects is essential not only for developing targeted therapeutic strategies to improve chronic wound healing but also for refining preventive approaches that minimize their occurrence. Advancing this knowledge will ultimately help enhance the quality of life for individuals with SCI.

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

The use of alkaline phosphatase as a bone turnover marker after spinal cord injury: A scoping review of human and animal studies

BACKGROUND

Serum alkaline phosphatase (ALP) is measured as an indicator of bone or liver disease. Bone-specific alkaline phosphatase (B-ALP) is an isoform of ALP found in the bone tissue which can predict fractures and heterotopic ossification.

OBJECTIVE

The aim of this scoping review was to explore the current use of ALP and B-ALP in studies using humans or animal models of SCI, and to identify ways to advance future research using ALP and B-ALP as a bone marker after SCI.

RESULTS

HUMAN STUDIES: 42 studies were included. The evidence regarding changes or differences in ALP levels in individuals with SCI compared to controls is conflicting. For example, a negative correlation between B-ALP and total femur BMD was observed in only one of three studies examining the association. B-ALP seemed to increase after administration of teriparatide, and to decrease after treatment with denosumab. The effects of exercise on ALP and B-ALP levels are heterogeneous and depend on the type of exercise performed. ANIMAL STUDIES: 11 studies were included. There is uncertainty regarding the response of ALP or B-ALP levels after SCI; levels increased after some interventions, including vibration protocols, curcumin supplementation, cycles in electromagnetic field or hyperbaric chamber. Calcitonin or bisphosphonate administration did not affect ALP levels.

CONCLUSION

Researchers are encouraged to measure the bone-specific isoform of ALP rather than total ALP in future studies in humans of animal models of SCI.

Bisphosphonates Alleviate Bone Loss in People with Acute Spinal Cord Injury：A Systematic Review and Meta-Analysis

OBJECTIVE

Bone loss is not to be underestimated in people with acute spinal cord injury (SCI). Bisphosphonates can inhibit the bone resorption of osteoclast. To study whether the early application of bisphosphonates can alleviate bone loss after acute SCI, we included 7 randomized controlled trials for meta-analysis.

METHODS

Seven randomized controlled trials were found in literature databases. The percentage change in bone mineral density (BMD) at different sites were primary outcomes and serum bone turnover markers were secondary outcomes. A random-effects model was selected for meta-analysis.

RESULTS

There were significant differences in the percentage change in BMD of the lumbar spine, total hip, and femoral neck between the bisphosphonates and control groups, but not in the percentage change in distal femur BMD. Besides, there were no statistically significant differences between the groups in the bone formation marker Procollagen type 1 N propeptide; bisphosphonates were effective in reducing the C-terminal telopeptide at the 6-month follow-up, but not at the 12-month follow-up. Subgroup analysis of the effects of zoledronate showed positive effects on BMD of the lumbar spine, total hip, and femoral neck at the 6-month follow-up and showed positive effects on BMD of the total hip and femoral neck at the 12-month follow-up.

CONCLUSIONS

Bisphosphonates can effectively alleviate the bone loss of the lumbar spine, total hip, and femoral neck in patients with acute SCI, and early application is advocated.

Vertebral insufficiency fractures as a cause of autonomic dysreflexia in a patient with chronic tetraplegia: A case report

Context: Osteoporosis is a known complication in spinal cord injury patients and can result in an increased risk of fractures and associated morbidity. Bone demineralization is most common in long bones below the level of injury. The pathogenesis is complex and not fully understood.Findings: We present the case of a 65-year-old male with chronic spinal cord injury who was found to have multiple vertebral compression fractures causing autonomic dysreflexia and new onset spasticity.Conclusion/Clinical Relevance: This case illustrates the need for improved awareness, diagnosis, and prevention for this disease process.

Unilateral cervical spinal cord injury induces bone loss and metabolic changes in non-human primates (Macaca fascicularis)

BACKGROUND/OBJECTIVE

The deleterious effects of chronic spinal cord injury (SCI) on the skeleton in rats, especially the lower extremities, has been proved previously. However, the long-term skeletal changes after SCI in non-human primates (NHP) have been scarcely studied. This study aimed to evaluate the bone loss in limbs and vertebrae and the bone metabolic changes in NHP after unilateral cervical spinal cord contusion injury.

METHODS

Twelve Macaca fascicularis were randomly divided into the SCI (n=8) and the Sham (n=4) groups. The SCI models were established using hemi-contusion cervical spinal cord injury on fifth cervical vertebra (C5), and were further evaluated by histological staining and neurophysiological monitoring. Changes of bone microstructures, bone biomechanics, and bone metabolism markers were assessed by micro-CT, micro-FEA and serological kit.

RESULTS

The NHP hemi-contusion cervical SCI model led to consistent unilateral limb dysfunction and potential plasticity in the face of loss of spinal cord. Furthermore, the cancellous bone mass of ipsilateral humerus and radius decreased significantly compared to the contralateral side. The bone volume fraction of humerus and radius were 17.2% and 20.1% on the ipsilateral while 29.0% and 30.1% on the contralateral respectively. Similarly, the thickness of the cortical bone in the ipsilateral forelimbs was significantly decreased, as well as the bone strength of the ipsilateral forelimbs. These changes were accompanied by diminished concentration of osteocalcin and total procollagen type 1 N-terminal propeptide (t-P1NP) as well as increased level of β-C-terminal cross-linking telopeptide of type 1collagen (β-CTX) in serological testing.

CONCLUSIONS

The present study demonstrated that hemi-SCI induced loss of bone mass and compromised biomechanical performance in ipsilateral forelimbs, which could be indicated by both muscle atrophy and serological changes of bone metabolism, and associated with a consistent loss of large-diameter cells of sensory neurons in the dorsal root ganglia.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Our study, for the first time, demonstrated the bone loss in limbs and vertebrae as well as the bone metabolic changes in non-human primates after unilateral spinal cord injury (SCI). This may help to elucidate the role of muscle atrophy, serological changes and loss of sensory neurons in the mechanisms of SCI-induced osteoporosis, which would be definitely better compared with rodent models.

Serum Concentration of Bone Metabolism Biomarkers in Goats during the Transition Period

Objective

During the transition period, the animal experiences a series of nutritional, physiological, and social changes. The objective of the present study was to evaluate the influence of the periparturient period in goats on the serum concentrations of the bone biomarkers osteocalcin (OC), bone-specific alkaline phosphatase (b-ALP), and pyridinoline cross-links (PYD).

Method

Blood samples were collected from fifteen female goats during the periparturient period 3 wk before expected parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (.

Results

Compared to a value of 77.67 ± 47.6 ng/mL at T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (P > 0.05). Compared to a value of 42.00 ± 19.50 U/L at T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (T -3), within 12 h of parturition (P > 0.05). Compared to a value of 42.00 ± 19.50 U/L at T -3), within 12 h of parturition (T -3), within 12 h of parturition (P > 0.05). Compared to a value of 42.00 ± 19.50 U/L at T -3), within 12 h of parturition (T -3), within 12 h of parturition (P > 0.05). Compared to a value of 42.00 ± 19.50 U/L at.

Conclusion

The results of this study showed that the bone formation biomarkers (OC and b-ALP) did not change significantly during the periparturient period, while the bone resorption biomarker decreased significantly at parturition compared to 3 wk before and 3 wk after parturition. The significantly increased serum estrogen around parturition may have had a role in the increased bone resorption at this time.

Assessment of Metabolic and Nutritional Imbalance in Mechanically Ventilated Multiple Trauma Patients: From Molecular to Clinical Outcomes

The critically ill polytrauma patient is characterized by a series of metabolic changes induced by inflammation, oxidative stress, sepsis, and primary trauma, as well as associated secondary injuries associated. Metabolic and nutritional dysfunction in the critically ill patient is a complex series of imbalances of biochemical and genetic pathways, as well as the interconnection between them. Therefore, the equation changes in comparison to other critical patients or to healthy individuals, in which cases, mathematical equations can be successfully used to predict the energy requirements. Recent studies have shown that indirect calorimetry is one of the most accurate methods for determining the energy requirements in intubated and mechanically ventilated patients. Current research is oriented towards an individualized therapy depending on the energy consumption (kcal/day) of each patient that also takes into account the clinical dynamics. By using indirect calorimetry, one can measure, in real time, both oxygen consumption and carbon dioxide production. Energy requirements (kcal/day) and the respiratory quotient (RQ) can be determined in real time by integrating these dynamic parameters into electronic algorithms. In this manner, nutritional therapy becomes personalized and caters to the patients’ individual needs, helping patients receive the energy substrates they need at each clinically specific time of treatment.

Can the positive association of osteocalcin with testosterone be unmasked when the preeminent hypothalamic-pituitary regulation of testosterone production is impaired? The model of spinal cord injury

PURPOSE

Osteocalcin (OCN), released from the bone matrix during the resorption phase, in its undercarboxylated form, stimulates testosterone (T) biosynthesis in mouse and a loss-of-function mutation of its receptor was associated with hypergonadotropic hypogonadism in humans. Nevertheless, when population-based studies have explored the OCN-T association, conflicting results have been reported. Hypothesizing that the evidence of a positive association between OCN and T could have been hindered by the preeminent role of a well-functioning hypothalamus-pituitary axis in promoting T biosynthesis, we explored this association in men with chronic spinal cord injury (SCI), exhibiting high prevalence of non-hypergonadotropic androgen deficiency.

METHODS

Fifty-five consecutive men with chronic SCI underwent clinical/biochemical evaluations, including measurements of total T (TT), OCN and 25(OH)D levels. Free T (FT) levels were calculated by the Vermeulen formula. Comorbidity was scored by Charlson comorbidity index (CCI).

RESULTS

A biochemical androgen deficiency (TT < 300 ng/dL) was observed in 15 patients (27.3%). TT was positively correlated with OCN, 25(OH)D and leisure time physical activity and negatively correlated with age, BMI and CCI. OCN was also positively correlated with calculated FT and negatively correlated with BMI and HOMA-IR. At the multiple linear regression analyses, a positive association of OCN with TT and calculated FT persisted after adjustment for confounders.

CONCLUSIONS

The positive association here found between OCN and T levels in men with chronic SCI reinforces the notion that a bone-testis axis is also functioning in humans and suggests that it can be unmasked when the preeminent hypothalamic-pituitary regulation of T production is impaired.

Daily parathyroid hormone administration enhances bone turnover and preserves bone structure after severe immobilization-induced bone loss

Immobilization, as a result of motor‐complete spinal cord injury (SCI), is associated with severe osteoporosis. Whether parathyroid hormone (PTH) administration would reduce bone loss after SCI remains unclear. Thus, female mice underwent sham or surgery to produce complete spinal cord transection. PTH (80 μg/kg) or vehicle was injected subcutaneously (SC) daily starting on the day of surgery and continued for 35 days. Isolated tibias and femurs were examined by microcomputed tomography scanning (micro‐CT) and histology and serum markers of bone turnover were measured. Micro‐CT analysis of tibial metaphysis revealed that the SCI‐vehicle animals exhibited 49% reduction in fractional trabecular bone volume and 18% in trabecular thickness compared to sham‐vehicle controls. SCI‐vehicle animals also had 15% lower femoral cortical thickness and 16% higher cortical porosity than sham‐vehicle counterparts. Interestingly, PTH administration to SCI animals restored 78% of bone volume, increased connectivity to 366%, and lowered structure model index by 10% compared to sham‐vehicle animals. PTH further favorably attenuated femoral cortical bone loss to 5% and prevented the SCI‐associated cortical porosity. Histomorphometry evaluation of femurs of SCI‐vehicle animals demonstrated a marked 49% and 38% decline in osteoblast and osteoclast number, respectively, and 35% reduction in bone formation rate. In contrast, SCI‐PTH animals showed preserved osteoblast and osteoclast numbers and enhanced bone formation rate. Furthermore, SCI‐PTH animals had higher levels of bone formation and resorption markers than either SCI‐ or sham‐vehicle groups. Collectively, these findings suggest that intermittent PTH receptor activation is an effective therapeutic strategy to preserve bone integrity after severe immobilization.

The Relationship Between Dietary Intakes of Amino Acids and Bone Mineral Density Among Individuals with Spinal Cord Injury

OBJECTIVES

The effect of dietary protein intake on bone mineral density (BMD) has not been explained in patients with spinal cord injury (SCI). In this study, we looked at the relationship between BMD and higher protein intake in patients with SCI while controlling for possible confounders.

METHODS

Patients with SCI, who were referred to the Brain and Spinal Cord Injury Research Center between November 2010 and April 2012, were included in the study. In total, the dietary intakes of 103 patients were assessed by 24-hour dietary recall interviews. We used dual-energy X-ray absorptiometry to measure BMD in the femoral neck, trochanter, intertrochanteric zone, hip, and lumbar vertebras.

RESULTS

Eighty-six men and 17 women participated in this study. Protein intake was negatively associated with the BMD of lumbar vertebrae (p = 0.001, r = -0.37 for T-score and p = 0.030, r = -0.24 for Z-score). The BMD of lumbar vertebrae were negatively associated with intake of tryptophan, isoleucine, lysine, cysteine, and tyrosine (p = 0.007, 0.005, 0.009, 0.008, and 0.008 for T-score, respectively). Higher intakes of threonine, leucine, methionine, phenylalanine, valine, and histidine were related to a lower BMD of lumbar vertebrae (p = 0.006, 0.010, 0.009, 0.010, 0.009, and 0.008 respectively for T-scores).

CONCLUSIONS

We found that high protein intake led to a lower BMD of lumbar vertebrae in patients with SCI after controlling for confounders including demographic and injury-related characteristics and calcium intake. No relationship between higher amino acids intake and BMD of the femur and hip was detected. Intake of alanine, arginine, and aspartic acid were not related to BMD.

Musculoskeletal Effects of 2 Functional Electrical Stimulation Cycling Paradigms Conducted at Different Cadences for People With Spinal Cord Injury: A Pilot Study

OBJECTIVE

To compare the musculoskeletal effects of low cadence cycling with functional electrical stimulation (FES) with high cadence FES cycling for people with spinal cord injury (SCI).

DESIGN

Randomized pre-post design.

SETTING

Outpatient rehabilitation clinic.

PARTICIPANTS

Participants (N=17; 14 men, 3 women; age range, 22-67y) with C4-T6 motor complete chronic SCI were randomized to low cadence cycling (n=9) or high cadence cycling (n=8).

INTERVENTIONS

Low cadence cycling at 20 revolutions per minute (RPM) and high cadence cycling at 50 RPM 3 times per week for 6 months. Cycling torque (resistance per pedal rotation) increased if targeted cycling cadence was maintained.

MAIN OUTCOME MEASURES

Dual-energy x-ray absorptiometry was used to assess distal femur areal bone mineral density, magnetic resonance imaging was used to assess to assess trabecular bone microarchitecture and cortical bone macroarchitecture and thigh muscle volume, and biochemical markers were used to assess bone turnover. It was hypothesized that subjects using low cadence cycling would cycle with greater torque and therefore show greater musculoskeletal improvements than subjects using high cadence cycling.

RESULTS

A total of 15 participants completed the study. Low cadence cycling obtained a maximal average torque of 2.9±2.8Nm, and high cadence cycling obtained a maximal average torque of 0.8±0.2Nm. Low cadence cycling showed greater decreases in bone-specific alkaline phosphatase, indicating less bone formation (15.5% decrease for low cadence cycling, 10.7% increase for high cadence cycling). N-telopeptide decreased 34% following low cadence cycling, indicating decreased resorption. Both groups increased muscle volume (low cadence cycling by 19%, high cadence cycling by 10%). Low cadence cycling resulted in a nonsignificant 7% increase in apparent trabecular number (P=.08) and 6% decrease in apparent trabecular separation (P=.08) in the distal femur, whereas high cadence cycling resulted in a nonsignificant (P>.3) 2% decrease and 3% increase, respectively.

CONCLUSIONS

This study suggests that the greater torque achieved with low cadence cycling may result in improved bone health because of decreased bone turnover and improved trabecular bone microarchitecture. Longer-term outcome studies are warranted to identify the effect on fracture risk.

Relationship between leptin and adiponectin concentrations in plasma and femoral and spinal bone mineral density in spinal cord-injured individuals

BACKGROUND CONTEXT

Previously, the associations between leptin and adiponectin levels with bone mineral density (BMD) have been reported in different populations, and occasionally, controversial results have been demonstrated. Until now, these relationships in spinal cord-injured individuals have not yet been described.

PURPOSE

We tried to investigate the correlation between leptin and adiponectin concentrations in plasma and BMD in Iranian patients with spinal cord injury (SCI).

STUDY DESIGN/SETTING

Cross-sectional investigation.

PATIENT SAMPLE

Referred patients with SCI who did not meet our exclusion criteria such as pregnancy, lactation, amputation, history of diabetes, cancer, endocrinology disease, and use of special medications entered the study.

OUTCOME MEASURES

Bone mineral density of femoral neck, trochanter, intertrochanteric zone, total hip, and lumbar vertebrae assessed by dual-energy X-ray absorptiometry and serum leptin and adiponectin levels measured by blood sample analysis using immunoassay techniques.

METHODS

Patient demographic characteristics were measured during face-to-face visits. Injury level and Spinal cord Injury Association (ASIA) score were assessed by clinical examination and were confirmed by imaging aids. Measured levels of leptin and adiponectin and dual-energy X-ray absorptiometry results were analyzed with partial correlation analysis method after adjustment for weight, body mass index (BMI), and age.

RESULTS

Total of 104 patients (19 females and 85 males) entered this investigation. Higher leptin concentration was significantly associated with higher BMD in femoral neck (p=.006, r=0.73), femoral intertrochanteric zone (p=.001, r=0.83), and hip (p=.001, r=0.81) only in female patients, whereas no such association was detected in male participants after adjusting for BMI and age. Leptin and adiponectin levels were not associated with lumbar spine BMD in both genders. Neither injury level nor ASIA score and plegia type (paraplegia or tetraplegia) influenced on leptin and adiponectin concentrations.

CONCLUSIONS

We found no association between leptin concentration and BMD in male individuals, whereas a positive correlation between leptin and BMD of femoral neck, intertrochanter, and hip was observed in female patients that shows a sexual polymorphism in this relationship. However, by considering the low number of female participants, these results should be interpreted cautiously. Lumbar spine BMD was associated with neither leptin nor adiponectin level in both genders.

Influence of racing on the serum concentrations of acute-phase proteins and bone metabolism biomarkers in racing greyhounds

This study was designed to evaluate the influence of racing on the serum concentrations of the acute-phase proteins (APPs) C-reactive protein (CRP), haptoglobin (Hp) and serum amyloid A (SAA) in 32 endurance-racing greyhounds. The study also aimed to investigate the effect of a 7 km race on the bone biomarkers osteocalcin (OC), bone-specific alkaline phosphatase (b-ALP) and pyridinoline cross-links (PYD). Total white blood cell (WBC) count, and the serum concentrations of cortisol, tumour necrosis factor-α (TNF-α), vitamin D and testosterone were also determined. Blood samples were collected 24 h prior to (T0) and within 2 h of completion of the race (T1). Compared to baseline values, WBC count did not change significantly (P = 0.2300), serum cortisol, Hp and SAA increased, while TNF-α and CRP decreased (P <0.0001 for each). There were no significant differences between the pre- and post-race serum concentrations of OC and PYD (P = 0.9500 and P = 0.2600, respectively), but serum b-ALP increased significantly (P = 0.0004). Serum concentrations of vitamin D and testosterone increased after racing (P = 0.0100 and P <0.0001, respectively). In this study, a 7 km race stimulated an acute-phase response, demonstrated by significant increases in the serum concentrations Hp and SAA in racing greyhounds. Increased serum b-ALP post-race probably indicates a change in bone metabolism and deserves further study.

Is lipid profile associated with bone mineral density and bone formation in subjects with spinal cord injury?

Purpose. The association between serum lipids and bone mineral density (BMD) has been investigated previously but, up to now, these relationships have not yet been described in spinal cord injury (SCI). We tried to assess the correlation between serum triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) and BMD in male subjects with SCI. Methods. Dual-energy X-ray absorptiometry (DXA) was used to assess BMD in femoral neck, trochanter, intertrochanteric zone, and lumbar vertebras. Blood samples were taken to measure serums lipids and bone biomarkers including osteocalcin, cross-linked type I collagen (CTX), and bone alkaline phosphatase (BALP). Partial correlation analysis was used to evaluate the relationships between mentioned measurements after adjustment for weight and age. Results. We found a positive correlation between HDL and femoral neck BMD (P: 0.004, r = 0.33). HDL was negatively correlated with osteocalcin (P: 0.017, r = -0.31) which was not in consistency with its relationship with BMD. TC and LDL were not related to CTX, BALP and BMD. Conclusion. This study does not support a strong association between serum lipids and BMD in subjects with SCI. Moreover it seems that positive association between HDL and BMD is not mediated through increased bone formation.