Effects of joint immobilization and treadmill exercise on marrow adipose tissue and trabecular bone after anterior cruciate ligament reconstruction in the rat proximal tibial epiphysis

Preventing effects of anterior cruciate ligament reconstruction on the trabecular bone remodeling in the rat proximal tibial epiphysis

A previous study reported that in patients with anterior cruciate ligament (ACL) injury, subchondral bone density in the proximal tibia was reduced in the antero-medial region, while it was increased in the postero-medial region. Anterior tibial instability due to ACL injury may be the cause of the remodeling in the proximal tibial epiphysis. The aim of this study was to determine whether re-stabilization of tibial instability by ACL reconstruction prevents remodeling in the rat proximal tibial epiphysis and if so, to find optimal timing of ACL reconstruction after ACL transection. ACL-transected rats were divided into immediate, early, and delayed ACL reconstruction (1, 14, and 28 days after ACL transection, respectively) groups. Some ACL-transected rats were reared without ligament reconstruction. Untreated rats were used as controls. At 56 days after ACL transection, trabecular bone mass in the proximal tibia was assessed histologically by measuring the trabecular bone area. ACL transection decreased the trabecular bone area in the antero-medial region of the proximal tibia, while it did not alter trabecular bone area in the postero-medial region. This trabecular bone loss in the antero-medial region was prevented when reconstruction was performed 1 day after ACL transection, but not prevented by ACL reconstruction performed in later period, 14 or 28 days after ACL transection. Our results suggest that ACL reconstruction surgery should be performed as early as possible to prevent trabecular bone loss in the antero-medial region of the proximal tibia.

Concurrent effects of high-intensity interval training and vitamin D supplementation on bone metabolism among women diagnosed with osteoporosis: a randomized controlled trial

BACKGROUND

Osteoporosis is often responsible for bone fragility and increased fracture risk due to the micro-architectural deterioration of bone tissue. In addition to nutritional supplements, exercise is considered an adjunct factor in safeguarding bone health. This study aimed to investigate the effects of 16-week high-intensity interval training (HIIT) and vitamin D supplementation on bone mineral density (BMD) in women with osteoporosis.

TRIAL DESIGN

This study used a four-arm pretest-posttest experimental randomized controlled design.

METHODS

One hundred twenty sedentary women aged (30-50 years), diagnosed with osteoporosis were recruited in this study. Patients were randomly classified into four groups with 30 patients in each group: control group (normal daily activities), exercise group (HIIT-exercise for 16 weeks), Vitamin D group (vitamin D 800IU/ day for 16 weeks), and concurrent group (HIIT exercise plus vitamin D for 16 weeks). Anthropometric measurements, BMD, and serum levels of vitamin 25-(OH) D, Osteocalcin, s-BAP, and calcium were estimated in all participants before and after exercise training.

RESULTS

Serum samples revealed that bone resorption markers, osteocalcin, total calcium, s-BAP, and vitamin 25(OH) D significantly improved in all groups; there was greater improvement in the HIIT training-vitamin D group than in the HIIT training, vitamin D, and control groups. Furthermore, the HIIT training-vitamin D group showed improvements in hip (right and left) and lumbar spine BMD than the HIIT training, Vitamin D, and Control groups. BMD improvements correlated positively with serum osteocalcin levels and total calcium and negatively with BMI and s-BAP.

CONCLUSIONS

Sixteen weeks of HIIT and vitamin D consumption showed greater benefits for BMD levels in women with osteoporosis than either vitamin D consumption or HIIT training alone. Therefore, HIIT plus vitamin D consumption may be a strategic option to prevent BMD reduction with aging or to slow demineralization.

TRIAL REGISTRATION

The study protocol was retrospectively registered at 'ClinicalTrials.gov PRS' under the trial identifier NCT06624657, dated 1/10/2024.

Long-term observation of marrow adipose tissue and trabecular bone in the rat proximal tibial epiphysis after anterior cruciate ligament reconstruction: effects of immobilization and non-weightbearing

Anterior cruciate ligament (ACL) injury and subsequent reconstruction induce marrow adipose tissue (MAT) accumulation accompanied by bone loss. Short-term immobilization or non-weightbearing after ACL reconstruction further promotes MAT accumulation. However, it is unclear if combining immobilization and non-weightbearing synergistically promotes MAT accumulation. Additionally, it is unknown whether MAT increase induced by immobilization or non-weightbearing can be reversed through remobilization or reloading. We aimed to address these questions. ACL-reconstructed rats were divided into four groups: no intervention, immobilization, non-weightbearing, or immobilization plus non-weightbearing. Immobilization and non-weightbearing were applied for 2 weeks, after which all rats were allowed to move unrestricted. Intact rats were used as controls. The marrow adiposity and trabecular bone in the proximal tibia were histologically assessed at 2-, 4-, and 12-weeks post-surgery. ACL reconstruction induced MAT accumulation and trabecular bone loss accompanied by increased osteoclastogenesis. Two weeks of immobilization and non-weightbearing after ACL reconstruction individually promoted MAT accumulation, but the combined use of these interventions had a similar impact on MAT accumulation as either of each intervention. Importantly, the increased MAT induced by immobilization or non-weightbearing did not reverse even after remobilization or reloading. Neither immobilization, non-weightbearing, nor both conditions combined after ACL reconstruction further decreased trabecular bone compared to no intervention. These findings suggest no synergistic effect of immobilization and non-weightbearing on MAT accumulation, and MAT accumulation induced by 2 weeks of both immobilization or non-weightbearing did not decrease even after at least 10 weeks of remobilization or reloading. MAT accumulation due to both immobilization and non-weightbearing did not have negative effects on trabecular bone.

Review of osteokines in spinal cord injury: potential biomarkers during rehabilitation

After spinal cord injury (SCI), mechanical unloading, denervation, as well as negative changes in blood supply, inflammation state, and hormone levels produce significant negative effects on bone density, leading to a high prevalence of osteoporosis after SCI. It has been recently discovered that skeletal bone also has endocrine functions. Osteokines, secreted from bone tissue, could play multiple roles in regulating bone density, muscle mass, glucose metabolism, and functions of the central nervous system-changes in the osteokine levels after SCI have been detected. Therefore, bone density and osteokine levels should be stressed in clinical settings. Clinical treatment measures for bone loss after SCI include exercise training, physical agent therapy, acupuncture, and so on. According to previous studies, these treatments could affect the expression levels of osteokines. In conclusion, bone loss and changes in osteokines after SCI are worthy of great attention during the rehabilitation of SCI. Osteokines could become biomarkers during SCI rehabilitation, reflecting both bone density and systemic functions. This review summarized recent findings regarding bone loss after SCI, changes in osteokines, and the effect of rehabilitation therapies, with a particular emphasis on the local and systemic regulatory roles of osteokines, as well as their potential as biomarkers during SCI rehabilitation.

The Effects of Corticosteroid Administration and Treadmill Exercise on Marrow Adipose Tissue and Trabecular Bone after Anterior Cruciate Ligament Reconstruction in Rats

We aimed to investigate the effects of short-term corticosteroid administration after anterior cruciate ligament (ACL) reconstruction on marrow adipose tissue (MAT) and trabecular bone mass, as well as to examine whether treadmill exercise can mitigate MAT increase and trabecular bone deterioration caused by corticosteroid. ACL-reconstructed rats were divided into groups: no intervention, daily treadmill exercise (60 min/day), administration of the steroidal drug dexamethasone (250 μg/kg on days 0-5, 7, and 9 post-operatively), or dexamethasone administration combined with treadmill exercise. Untreated rats were served as controls. At day 10 or 30 post-operatively, histological assessments were performed in the proximal tibial epiphysis. MAT accumulation and trabecular bone loss were observed after ACL reconstruction. Dexamethasone promoted MAT accumulation at day 10 post-operatively but did not affect the trabecular bone loss. The MAT accumulation caused by dexamethasone reversed within 21 days after discontinuation. Treadmill exercise did not influence the changes in the MAT and trabecular bone areas. Short-term corticosteroid administration after ACL reconstruction promoted MAT accumulation while not affecting trabecular bone area. The MAT accumulation resulting from corticosteroid administration was reversible after discontinuation. Treadmill exercise could not mitigate the accumulation of MAT caused by corticosteroid administration and did not affect trabecular bone area.

Effects of Weight Bearing on Marrow Adipose Tissue and Trabecular Bone after Anterior Cruciate Ligament Reconstruction in the Rat Proximal Tibial Epiphysis

The effects of mechanical unloading after anterior cruciate ligament (ACL) reconstruction on bone and marrow adipose tissue (MAT) are unclear. We investigated weight bearing effects on bone and MAT after ACL reconstruction. Rats underwent unilateral knee ACL transection and reconstruction, followed by hindlimb unloading (non-weight bearing), no intervention (low-weight bearing, the hindlimb standing time ratio (STR; operated/contralateral) during treadmill locomotion ranging from 0.55 to 0.91), or sustained morphine administration (moderate-weight bearing, STR ranging from 0.80 to 0.95). Untreated rats were used as controls. At 7 or 14 days after surgery, changes in trabecular bone and MAT in the proximal tibial were assessed histologically. Histological assessments at 7 or 14 days after surgery showed that ACL reconstruction without post-operative intervention did not significantly change trabecular bone and MAT areas. Hindlimb unloading after ACL reconstruction induced MAT accumulation with adipocyte hyperplasia and hypertrophy within 14 days, but did not significantly affect trabecular bone area. Increased weight bearing through morphine administration did not affect trabecular bone and MAT parameters. Our results suggest that early weight bearing after ACL reconstruction is important in reducing MAT accumulation, and that reduction in weight bearing alone is not sufficient to induce bone loss early after ACL reconstruction.