Stricture dilation via balloon-assisted endoscopy in Crohn's disease: approach and intraprocedural outcomes with the single-balloon and double-balloon systems

Background

Despite recent emerging literature involving the utility of endoscopic balloon dilation (EBD) of strictures via balloon-assisted endoscopy (BAE), specifically regarding the management of Crohn's disease (CD), the optimal clinical approach with balloon systems has been largely neglected in academic literature.

Objectives

This study assesses the intra-procedural success and safety of EBD via BAE for small bowel CD strictures while detailing our clinical approach and technique. Secondarily, we compare the single-balloon endoscope (SBE) and double-balloon endoscope (DBE) systems for EBD-related outcomes.

Design

Retrospective consecutive patient cohort analysis.

Methods

We retrospectively assessed a consecutive small bowel CD patient cohort undergoing BAE at the University of Alberta Hospital endoscopy unit from 2013 to 2020. The primary endpoint discerned the safety and immediate success rate of EBD during endoscopy, and comparisons of the dilation parameters and efficacy of SBE versus DBE were assessed as secondary outcomes.

Results

During the study period, 87 patients (44 male) with a mean age of 56 ± 14.7 years underwent 179 endoscopic procedures (92 DBE and 87 SBE). Of 358 strictures encountered, 320 (89.4%) were successfully dilated and traversed. The mean maximum dilation diameter was 15.76 ± 2.10 mm. There were no perforations or major adverse events.

Conclusion

EBD via BAE is a safe procedure in small bowel CD with a high intraprocedural success rate. Overall, SBE had a higher success rate in traversing strictures before and after dilation using our technique. This analysis is limited by the retrospective nature of our study and must be balanced against the inherent benefits of the DBE system.

A novel smartphone application for the tracking of procedural numbers and trainee experience in gastrointestinal endoscopy

OBJECTIVES

The tracking and documentation of procedures in gastrointestinal endoscopy including therapeutic interventions is an essential but challenging process. The University of Alberta has developed a smartphone app to help facilitate this task. This study evaluated the functionality, usefulness, and user satisfaction of this app.

METHODS

Four Gastroenterology (GI) residents and two therapeutic endoscopy fellows participated in the study. The trainees submitted all their data into the app from the procedures in which they participated hands-on for one year, data was collected and analyzed on the app and the website associated with it.

RESULTS

Trainees were able to register the procedures immediately after each procedure without difficulty, this data was available to be reviewed at anytime in the app and associated website. Furthermore, the data collected was able to be transformed into tables and graphs on the app website. The total number of procedures and therapeutic interventions performed were easily accessed in the app and website at anytime. The app facilitated the calculation of the cecal intubation rate in colonoscopy and the cannulation rate in ERCP for the therapeutic endoscopy trainee. Trainees reported excellent experience with the app capabilities.

CONCLUSIONS

A novel smartphone app was useful in collecting meaningful data submitted by gastrointestinal endoscopy trainees, furthermore, through an associated website, it was capable to create graphs and tables to show and facilitate the calculation of meaningful data such as key performance indicators.

A randomized controlled trial of a multicomponent online stress reduction intervention in inflammatory bowel disease

BACKGROUND

Psychological stress negatively impacts inflammatory bowel disease (IBD) outcomes. Patients have prioritized access to online interventions; yet, the data on these have been limited by mixed in-person/online interventions, low adherence, and non-randomized controlled trial (RCT) design.

OBJECTIVES

We assessed the efficacy of and adherence to a 12-week online multicomponent stress reduction intervention in IBD.

DESIGN

This is a RCT.

METHODS

Adult participants on stable IBD medical therapy with elevated stress levels from four centers were randomized to intervention or control groups. Intervention participants received a 12-week online program including a weekly yoga, breathwork and meditation video (target 2-3 times/week), a weekly cognitive behavioral therapy/positive psychology informed video activity, and weekly 10-min check-ins by a study team member. Control participants received weekly motivational messages by email. All patients received standard of care IBD therapy. The primary outcome was Cohen's Perceived Stress Scale (PSS). Secondary outcomes evaluated mental health, resilience, health-related quality of life (HRQoL), symptom indices, acceptability, adherence, and inflammatory biomarkers. Analysis of covariance was used to determine between-group differences.

RESULTS

Of 150 screened patients, 101 were randomized to the intervention (n = 49) and control (n = 52) groups (mean age: 42.5 ± 14.1 years; M:F 1:3, 48% with ulcerative colitis and 52% with Crohn's disease). The between-group PSS improved by 22.4% (95% confidence interval, 10.5-34.3, p < 0.001). Significant improvements were seen in mental health, resilience, and HRQoL measures, with a median satisfaction score of 89/100 at the end of the 12 weeks. In the 44/49 patients who completed the intervention, 91% achieved program adherence targets.

CONCLUSION

This 12-week online intervention improved perceived stress, mental health, and HRQoL, but did not impact IBD symptom indices or inflammatory biomarkers. The program was readily adopted and adhered to by participants with high retention rates. After iterative refinement based on participant feedback, future studies will evaluate the impact of a longer/more intense intervention on disease course.

REGISTRATION

ClinicalTrials.gov Identifier NCT03831750.

PLAIN LANGUAGE SUMMARY

An online stress reduction intervention in inflammatory bowel disease patients improves stress, mental health, and quality of life People with inflammatory bowel disease (IBD) have high levels of stress, anxiety, and depression. Although IBD patients have expressed the need for online mental wellness interventions, the existing data to support these interventions in IBD are limited. In this trial, 101 IBD patients had the chance to participate in a 12-week online stress reduction intervention. In those patients randomly selected to participate in the online intervention, each week they received the following: a 20- to 30-min yoga, breathwork, and meditation video that they were asked to do 2-3 times a week, a 10- to 20-min mental wellness activity they were asked to do once during the week, and a 10-min telephone check-in with a study team member. Participants who were not selected to use the online intervention received a weekly motivational message by email. In all, 90 of the 101 participants (89%) completed the study with the mean age of participants being 43 years and the majority being females (75%). Ninety-one percent of participants who completed the intervention met the program target of doing the yoga, breathwork, and meditation video at least 2 times per week. Significant improvements were seen in perceived stress (by 22.4%), depression (by 29.5%), anxiety (by 23.7%), resilience (by 10.6%), and quality of life (by 8.9%). No changes were seen in IBD severity or in blood markers of inflammation. In conclusion, this study demonstrates evidence that a 12-week online stress reduction intervention had low dropout rates, high adherence and beneficial effects on stress, mental health, and quality of life measures. Continued feedback will be sought from study participants and our IBD patient partners to refine the intervention and assess the impact in future studies of patients with active IBD, as well as the impact of a longer/more intense intervention.

Concomitant 5-Aminosalicylate Therapy in Moderate-to-Severe Ulcerative Colitis Patients Escalated to Infliximab Is Not Beneficial

BACKGROUND AND AIMS

While there is recent literature to support the discontinuation of 5-aminosalicylate (5-ASA) upon the initiation of biologics, continuing 5-ASA after treatment failure is relatively common. We aimed to assess the impact of concomitant 5-ASA therapy on clinical outcomes in ulcerative colitis (UC) patients escalated to infliximab.

METHODS

This is a retrospective chart review of patients with moderate-to-severe UC started on infliximab between January 2012 and December 2017 at the University of Alberta. The primary outcome was clinical remission (partial Mayo score < 2) at 6 and 12 months. Secondary outcomes included endoscopic (endoscopic Mayo < 2) and deep remission (combined clinical and endoscopic remission) as well as the need for rescue therapy, hospitalization or colectomy. Univariate and multivariate logistic regression models were used to estimate the odds ratios and 95% CI for the outcomes.

RESULTS

One hundred and twenty-one patients were followed over a period of 47 (SD = 34) months. Patients on 5-ASA had increased concomitant immunomodulator use (73.3% vs. 54.1%, p = 0.03). There was no difference in clinical remission at 6 (aOR 2.59, p = 0.07) or 12 months (aOR 0.43, p = 0.06). At 12 months, patients on concomitant 5-ASA were less likely to achieve endoscopic (aOR 0.08, p = 0.01) and deep remission (aOR 0.07, p = 0.02). Adverse outcomes such as need for rescue therapy, hospitalization, and colectomy did not differ between the groups.

CONCLUSIONS

Our data suggest that 5-ASA may be stopped in patients with moderate-to-severe UC who have been escalated to infliximab therapy as it has no additional benefit to control inflammation.

Double-Balloon Endoscopy in Crohn Disease: A Tertiary Referral Center Experience

BACKGROUND

Crohn disease (CD) affects the small bowel in 80% of patients. Double balloon endoscopy (DBE) provides the potential for direct and extensive mucosal visualization with the potential for diagnostic monitoring and therapeutic intervention. This study aimed to investigate the safety and effectiveness of DBE in small-bowel CD.

METHODS

From our DBE database, patients with CD at the time of index DBE (January 2004-January 2013) were identified. Data collection included demographics, CD phenotype (age at diagnosis, disease location, disease activity), procedural information, adverse events (perforation, pancreatitis, death), therapeutic intervention (stricture dilation), and outcome (escalation or maintenance of existing therapy, referral to surgery).

RESULTS

A total of 184 DBEs were performed in patients with inflammatory bowel disease over 162 endoscopic sessions. In this cohort, 115 patients had previously diagnosed CD. A diagnosis of CD was made in 22 patients. Of those with known CD, 140 DBEs were performed in 82 patients; DBE findings led to escalation of medical therapy in 26% of patients, maintenance of therapy in 26% of patients, and surgery in 18% of patients. We considered DBE to have failed in 11% (n = 18) of patients. During 46 endoscopic sessions, in 29 patients, 103 strictures were dilated via balloon dilation. Of patients undergoing dilation with clinical follow-up, 19 of 24 (79%) patients were surgery-free during the study period. Overall, there were 2 perforations.

CONCLUSIONS

We found that DBE is a safe and effective procedure in patients with suspected or established CD. Furthermore, patients undergoing dilation of strictures via DBE had an 80% surgery-free rate within the follow-up period.

Pregnancy-Related Beliefs and Concerns of Inflammatory Bowel Disease Patients Modified After Accessing e-Health Portal

Objective

Poor inflammatory bowel disease (IBD)-specific reproductive knowledge is associated with concerns and medication noncompliance. Having shown an educational portal can improve knowledge, we evaluated its effectiveness for addressing IBD patients’ reproductive and medication concerns.

Methods

Adult IBD participants (aged 18 to 45 years) were invited to access an e-health portal providing information on heritability, fertility, surgery, pregnancy outcomes, delivery, postpartum, and breastfeeding in the context of IBD and IBD medications. At pre-, post-, and 6+-month postintervention, participants completed a questionnaire on IBD-specific pregnancy concerns, medication concerns from the Beliefs About Medicines Questionnaire (BMQ), and medication adherence via the Medication Adherence Rating Scale (MARS). The Wilcoxon signed-rank test was used to compare median differences between scores (95% confidence).

Results

Demographics for 78 (70.3%) participants completing postintervention questionnaires: median age 29.3 (interquartile range: 25.6 to 32.9) years; 54 (69.2%) Crohn’s disease; 21 (26.9%) ulcerative colitis; 63 (80.3%) females, 5 (7.9%) pregnant; and 19 (30.2%) previously pregnant. Postintervention, the median number of reproductive concerns decreased from 3 to 1, and remained stable 6+ months later (P < 0.001*). The median BMQ score decreased from 28 to 25, and remained stable 6+ months later (P = 0.032*). Participants adherent to medications increased from 82.4% to 87.8% postintervention (P = 0.099).

Conclusion

Using an e-health portal may potentially reduce IBD-specific reproductive and medications concerns. An e-health portal is feasible as one component of managing IBD patient’s reproductive and medication concerns during preconception and pregnancy.

Preoperative Ustekinumab Treatment Is Not Associated With Increased Postoperative Complications in Crohn's Disease: A Canadian Multi-Centre Observational Cohort Study

BACKGROUND

Ustekinumab (UST), an anti-IL12/23 inhibitor is indicated for moderate-to-severe Crohn's disease (CD). However, it is unclear if patients treated with UST are at increased risk for postoperative complications.

AIM

To evaluate the postoperative safety outcomes in UST-treated CD patients.

METHODS

A multicentre cohort study of UST-treated CD patients at two tertiary care centres (University of Calgary, University of Alberta, Canada) undergoing abdominal surgery between 2009 and 2016 was performed. Postoperative outcomes were compared against a control cohort of anti-TNF-treated patients over the same time-period. The primary outcome was occurrence of postoperative complications up to six months postoperatively, stratified by timing (early <30 days vs. late complications ≥30 days).

RESULTS

Twenty UST-treated patients and 40 anti-TNF-treated patients were included with a median preoperative treatment exposure of 6.5 months and 18 months, respectively (p=0.01). Bowel obstruction was the most common surgical indication in both cohorts. UST-treated patients were more likely to require an ostomy (70.0% vs. 12.5%, p<0.001) and be on combination therapy with either systemic corticosteroids or concurrent immunomodulators (azathioprine or methotrexate) (25.0% vs. 2.5%, p=0.01). Despite the increased concomitant use of immunosuppression in the UST-treated cohort, there were no significant differences in early or late postoperative wound infections (1/20 in UST-cohort, 2/40 in anti-TNF cohort, p=1.00), anastomotic leak (0/20 in UST-cohort, 3/40 in anti-TNF cohort, p=0.54), or postoperative ileus/obstruction (3/20 in UST-cohort, 4/40 in anti-TNF cohort, p=0.67).

CONCLUSIONS

CD patients receiving preoperative UST did not experience an increase in postoperative complications, despite increased use of concurrent immunosuppression.

Clinical, endoscopic and radiographic outcomes with ustekinumab in medically-refractory Crohn's disease: real world experience from a multicentre cohort

BACKGROUND

Ustekinumab is a monoclonal antibody targeting interleukins-12 and -23, with efficacy in Crohn's disease (CD) demonstrated in clinical trials.

AIM

To assess the real-world clinical, endoscopic and radiographic response and remission outcomes achieved with ustekinumab in medically-refractory CD.

METHODS

A retrospective multicentre cohort study was performed on CD patients receiving ustekinumab between 2011 and 2016. The primary outcome was achievement of clinical and objective steroid-free response and remission at 3, 6 and 12 months. Clinical response and remission were defined by reduction in Harvey Bradshaw Index (HBI) of ≥3 points and an HBI ≤4 points respectively. Objective response was defined by improvement in endoscopic or radiographic CD, as assessed by ileocolonoscopy, contrast-enhanced ultrasound or CT/MR enterography. Objective remission was defined by endoscopic mucosal healing or complete resolution of inflammatory parameters on radiographic assessment.

RESULTS

A total of 167 CD patients were treated with ustekinumab. 95.2% (159/167) previously failed anti-TNF therapy. Median follow-up was 45.6 weeks (IQR: 24.4-88.9). At 3 months, clinical response was achieved in 38.9% (65/167) and remission in 15.0% (25/167) of patients. At 6 months, clinical response was achieved in 60.3% (91/151) and remission in 25.2% (38/151) of patients. At 12 months, clinical response was achieved in 59.5% (66/111) and remission in 27.9% (31/111) of patients. Endoscopic or radiographic response was demonstrated in 54.5% (67/123) at 6 months and 55.8% (48/86) of patients at 12 months.

CONCLUSIONS

Ustekinumab is an effective therapeutic option for inducing and maintaining clinical, endoscopic and radiographic response in patients with Crohn's disease failing anti-TNF therapy.

Lymphoproliferative disorders in inflammatory bowel disease patients on immunosuppression: Lessons from other inflammatory disorders

Immunosuppressive agents, such as thiopurines, methotrexate, and biologics, have revolutionized the treatment of inflammatory bowel disease (IBD). However, a number of case reports, case control studies and retrospective studies over the last decade have identified a concerning link between immunosuppression and lymphoproliferative disorders (LPDs), the oncological phenomenon whereby lymphocytes divide uncontrollably. These LPDs have been associated with Epstein-Barr virus (EBV) infection in which the virus provides the impetus for malignant transformation while immunosuppression hampers the immune system’s ability to detect and clear these malignant cells. As such, the use of immunosuppressive agents may come at the cost of increased risk of developing LPD. While little is known about the LPD risk in IBD, more is known about immunosuppression in the post-transplantation setting and the development of EBV associated post-transplantation lymphoproliferative disorders (PTLD). In review of the PTLD literature, evidence is available to demonstrate that certain immune suppressants such as cyclosporine and T-lymphocyte modulators in particular are associated with an increased risk of PTLD development. As well, high doses of immunosuppressive agents and multiple immunosuppressive agent use are also linked to increased PTLD development. Here, we discuss these findings in context of IBD and what future studies can be taken to understand and reduce the risk of EBV-associated LPD development from immunosuppression use in IBD.

Adalimumab dose escalation is effective for managing secondary loss of response in Crohn's disease

BACKGROUND

The efficacy of adalimumab in maintaining remission in Crohn's disease patients may wane over time, leading to secondary loss of response that is often managed with dose escalation. However, the response to adalimumab dose escalation and long-term outcomes after escalation have not been well evaluated.

AIMS

To characterise the short- and long-term clinical responses to adalimumab dose escalation for secondary loss of response.

METHODS

A retrospective cohort study evaluating Crohn's disease out-patients requiring adalimumab dose escalation for secondary loss of response from 2003 to 2013 was conducted. The primary outcome was the proportion of patients achieving symptomatic clinical response to dose escalation and subsequent development of tertiary loss of response. Duration of regained response was assessed by Kaplan-Meier analysis.

RESULTS

Ninety-two CD patients met inclusion criteria with mean duration of follow-up of 170.2 weeks (±129.6 weeks). Disease distribution was predominantly ileal (37/92, 40.2%) or ileocolonic (43/92, 46.7%), with equal distribution of inflammatory (34.8%), stricturing (27.2%), and penetrating (38.0%) disease phenotypes. At 24 weeks post-dose escalation, 74/92 (80.4%) patients had symptomatic clinical response. Among responders, median duration of sustained response was 69.2 weeks (IQR 29.4-107.1) but 42/74 (56.8%) responders experienced subsequent tertiary loss of response at a median time of 47.9 weeks (IQR 24.7-80.3). C-reactive protein >10.0 mg/L at the time of dose escalation predicted tertiary loss of response in univariate analysis (OR 3.32, 95% CI: 1.18-9.37).

CONCLUSIONS

In patients with Crohn's disease, adalimumab dose escalation is effective for recapturing symptomatic response after secondary loss of response, but more than half will eventually experience a tertiary loss of response.

Crohn's disease outpatients treated with adalimumab have an earlier secondary loss of response and requirement for dose escalation compared to infliximab: a real life cohort study

BACKGROUND

The efficacy of anti-tumor necrosis factor alpha agents in maintaining remission in Crohn's disease may wane over time, leading to secondary loss of response that can often be overcome with dose escalation. Comparison of secondary loss of response of adalimumab and infliximab during long-term treatment of CD in a real-life IBD clinic has not been previously evaluated.

METHODS

A retrospective cohort study was conducted evaluating outpatients with CD on a maintenance regimen with adalimumab or infliximab from 200 to 2013 and who experienced a secondary loss of response. All infliximab-treated patients were anti-TNF naïve. Adalimumab-treated patients were stratified by prior anti-TNF exposure. Kaplan-Meier analysis was conducted to compare time to loss of response.

RESULTS

218 CD patients met inclusion criteria (117 infliximab, 101 adalimumab). Median follow-up duration was 170.0weeks for infliximab and 122.0weeks for adalimumab (p=0.61). The proportion of patients with secondary loss of response was similar for infliximab-treated - 51.3% (60/117) compared to adalimumab patients naïve to anti-TNF therapy - 60.5% (23/38) (p=0.32), and adalimumab patients with prior anti-TNF exposure - 65.1% (41/63) (p=0.08). Median time to secondary loss of response was longer for infliximab patients (99.3wk, IQR 55.7-168.5) compared to both adalimumab patients naïve to anti-TNF therapy (58.9wk, IQR 29.0-85.7) (p=0.03), and adalimumab patients with prior anti-TNF exposure (52.7wk, IQR 20.1-85.0) (p<0.001).

CONCLUSIONS

Over 50% of CD patients treated with infliximab and adalimumab develop secondary loss of response. Time to loss of response was shorter in patients treated with adalimumab compared to those treated with infliximab. Prior anti-TNF exposure further accelerated time to loss of response.

Effects of dried plum supplementation on bone metabolism in adult C57BL/6 male mice

Dietary supplementation of dried plum (DP) prevents bone loss and restores bone mass in osteopenic animal models. This study was designed to determine the effects of DP supplementation on bone metabolic activity over time using adult (6-month-old) male C57BL/6 mice (n = 40) receiving control (CON = AIN93 M) or CON+DP 25 % (w/w) diets for 4 or 12 weeks. After 4 weeks of treatment, animals consuming the DP diet had a higher whole-body bone mineral density, vertebral trabecular bone volume (BV/TV), and femoral cortical thickness compared to the CON animals. In the distal metaphysis of the femur, BV/TV was increased in the DP-treated animals, but only after 12 weeks. Bone histomorphometric analyses revealed that DP decreased osteoblast surface (67 %) and osteoclast surface (62 %) at 4 weeks, but these surfaces normalized to the CON animals by 12 weeks. Coincident with these changes, the mineralizing surface (MS/BS) and cancellous bone formation rate (BFR/BS) were reduced at 4 weeks in the DP group compared to the CON, but by 12 weeks of DP supplementation, BFR/BS (~twofold) and MS/BS (~1.7-fold) tended to be increased (p < 0.10). The relative abundance of RNA for key regulators of osteoblast and osteoclast differentiation and indicators of osteoblast activity were reduced in the DP group at 4 weeks with no difference between groups at 12 weeks. These results indicate that supplementing the diet with DP initially suppressed cancellous bone turnover, but a biphasic response occurs over time, resulting in a positive effect on bone mass and structure.

Comparison of MR enteroclysis with video capsule endoscopy in the investigation of small-intestinal disease

Purpose

To evaluate the diagnostic accuracy of MR enteroclysis and to compare it to video capsule endoscopy (VCE) in the analysis of suspected small-bowel disease.

Methods

We performed a retrospective analysis of 77 patients who underwent both MR enteroclysis and VCE and compared the findings of these studies with the findings of enteroscopy, surgery, or with the results of clinical follow-up lasting ≥2 years.

Results

Findings included malignant neoplasms (n = 13), benign neoplasms (n = 10), refractory celiac disease (n = 4), Crohn’s disease (n = 2) and miscellaneous conditions (n = 10). Specificity of MR enteroclysis was higher than that of VCE (0.97 vs. 0.84, P = 0.047), whereas sensitivity was similar (0.79 vs. 0.74, P = 0.591). In 2/32 (6.3%) patients with both negative VCE and negative MR enteroclysis a positive diagnosis was established, compared to 5/11 (45.5%) patients in whom VCE was positive and MR enteroclysis was negative (likelihood ratio 8.1; P = 0.004), 9/11 (81.8%) patients in whom MR enteroclysis was positive and VCE was negative (likelihood ratio 23.5; P < 0.0001), and all 23 patients in whom both VCE and MR enteroclysis showed abnormalities (likelihood ratio 60.8; P < 0.0001).

Conclusions

VCE and MR enteroclysis are complementary modalities. In our study-population, MR enteroclysis was more specific than VCE, while both produced the same sensitivity.

Lesions of T-cell-mediated kidney allograft rejection in mice do not require perforin or granzymes A and B

Organ allograft rejection is strongly associated with the presence of alloreactive cytotoxic T cells but the role of cytotoxicity in the pathologic lesions is unclear. Previous studies showed that the principal lesions of kidney rejection - interstitial infiltration, tubulitis, and endothelial arteritis - are T-cell-dependent and antibody-independent. We studied the role of cytotoxic granule components perforin and granzymes A and B in the evolution of the T-cell-mediated lesions of mouse kidney transplant rejection. By real-time RT-PCR, allografts rejecting in wild-type hosts at days 5, 7, 21, and 42 showed massively elevated and persistent expression of perforin and granzymes A and B, but evolution of tubulitis and arteritis did not correlate with increasing granzyme or perforin expression. Allografts transplanted into hosts with disrupted genes for perforin or granzymes A and B showed no change in tubulitis, arteritis, or MHC induction. Thus the development of the histologic lesions diagnostic of T-cell-mediated kidney transplant rejection are associated with but not mediated by perforin or granzyme A or B. Together with previous graft survival studies, these results indicate that the granule-associated cytotoxic mechanisms of T cells are not the effectors of T-cell-mediated allograft rejection.

bFGF administration lowers the phosphate threshold for mineralization in bone marrow stromal cells

Basic fibroblast growth factor (bFGF) is a potent mitogen and acts as an autocrine/paracrine factor for osteoblasts. Long-term administration of bFGF in vivo increases osteoblast number and stimulates matrix formation, but induces hypophosphatemia and impairs matrix mineralization. The goal of this study was to examine the interaction between bFGF and low levels of organic phosphate in an effort to better understand the possible long-term therapeutic effects of bFGF. These data show that in vitro administration of bFGF accelerates the calcification process and lowers the phosphate threshold needed for successful bone nodule formation. This correlates well with the observed upregulation of mRNA production for alkaline phosphatase and osteocalcin at day 7. These findings help elucidate the mechanisms of bFGF action on bone marrow stromal cell differentiation and mineralization and indicate that the delay in mineralization observed in vivo may not be caused by decreased phosphate availability alone.

Skeletal unloading induces resistance to insulin-like growth factor I on bone formation

Skeletal unloading results in an inhibition of bone formation associated with a decrease in osteoblast number, impaired mineralization of bone, and altered proliferation and differentiation of osteoprogenitor cells. Although such changes are likely to be mediated by multiple factors, resistance to the growth-promoting action of insulin-like growth factor I (IGF-I) has been hypothesized to play an important role. To determine whether skeletal unloading induces resistance to IGF-I on bone formation, we examined the response of unloaded (hindlimb elevation) and normally loaded tibia and femur to IGF-I administration. To eliminate the variable of endogenous growth hormone production and secretion during exogenous IGF-I administration, we used growth hormone-deficient dwarf rats (dw-4). The rats were given IGF-I (2.5 mg/kg/day) or vehicle during 7 and 14 days of unloading or normal loading. This significantly increased the serum level of IGF-I in both the normally loaded and unloaded rats. Unloading did not affect the serum level of IGF-I in the vehicle-treated rats. IGF-I markedly increased periosteal bone formation at the tibiofibular junction of normally loaded rats. Unloading decreased bone formation in the vehicle-treated rats, and blocked the ability of IGF-I to increase bone formation. On the other hand, IGF-I increased periosteal bone formation at the midpoint of the humerus (normally loaded in this model) in both hindlimb-elevated and normally loaded rats. IGF-I significantly increased osteogenic colony number, total ALP activity, and total mineralization in bone marrow osteoprogenitor (BMOp) cells of normally loaded rats. Unloading reduced these parameters in the vehicle-treated rats, and blocked the stimulation by IGF-I. Furthermore, IGF-I administration (10 ng/ml) in vitro significantly increased cell proliferation of the BMOp cells isolated from normally loaded bone, but not that of cells from unloaded bone. These results indicate that skeletal unloading induces resistance to IGF-I on bone formation.

Mechanical and chemical characteristics of mineral produced by basic fibroblast growth factor-treated bone marrow stromal cells in vitro

It has been shown that various organ and cell cultures exhibit increased mineral formation with the addition of basic fibroblast growth factor (bFGF) and phosphate ions in the medium. However, to date there has been no attempt to relate the chemical composition of mineral formed in vitro to a measure of its mechanical properties. This information is important for understanding the in vivo mineralization process, the development of in vitro models, and the design of tissue-engineered bone substitutes. In this study we examined the reduced modulus; hardness; and mineral-to-matrix, crystallinity, carbonate-to-mineral, and calcium-to-phosphorus ratios of mineral formed by bFGF-treated rat-derived bone marrow stromal cells in vitro. The cells were treated with 1 or 3 mM beta-glycerophosphate for 3 and 4 weeks. Both mechanical parameters, reduced modulus and hardness, increased with increasing beta-glycerophosphate concentration. The only chemical measure of the mineral composition that exhibited the same dependency was the mineral-to-matrix ratio. The values of crystallinity and carbonate fraction were similar to those for intact cortical bone, but the calcium-to-phosphorus ratio was substantially lower than that of normal bone. These data indicate that the mineral formed by bFGF-treated bone cells is mechanically and chemically different from naturally formed lamellar bone tissue after 4 weeks in culture. These results can be used to improve in vitro models of mineral formation as well as enhance the design of tissue-engineered bone substitutes.

Spaceflight alters bone mechanics and modeling drifts in growing rats

BACKGROUND

Alterations in bone metabolism may be a particularly serious consequence of spaceflight and a major obstacle to long-term space exploration. The effects of spaceflight on bone mechanics are unclear. This study examined the effects of spaceflight on bone mechanics in a growing rat model during a 17-d mission aboard the space shuttle (STS-78).

METHODS

There were 18 rats that were divided into 3 experimental groups: flight rats (n = 6), ground-based control rats housed in an animal enclosure module (AEM, n = 6), and ground-based control rats housed in standard vivarium caging (n = 6). At the conclusion of the mission, rat femurs were tested in three-point bending followed by static and dynamic bone histomorphometry.

RESULTS

Maximum stress was unaffected by spaceflight, but flexural rigidity was significantly decreased in flight animals. Much of the decrease appeared to be the result of decreases in tissue properties (elastic modulus) rather than structural changes within the bone. No significant differences in cortical bone mass or geometry were observed. In contrast, endocortical resorption was significantly decreased in flight rats accompanied by a nonsignificant decrease in periosteal bone formation, suggesting alterations in bone modeling drifts during spaceflight. For nearly all measured indices, ground-based AEM rats displayed values intermediate to flight and ground-based vivarium rats.

CONCLUSIONS

Spaceflight can impair tissue properties in femoral cortical bone during growth without significant decreases in bone mass or geometry.

Long-term measurement of bone strain in vivo: the rat tibia

Despite the importance of strain in regulating bone metabolism, knowledge of strains induced in bone in vivo during normal activities is limited to short-term studies. Biodegeneration of the bond between gauge and bone is the principle cause of this limitation. To overcome the problem of bond degeneration, a unique calcium phosphate ceramic (CPC) coating has been developed that permits long-term attachment of microminiature strain gauges to bone. Using this technique, we report the first long-term measurements of bone strain in the rat tibia. Gauges, mounted on the tibia, achieved peak or near peak bonding at 7 weeks. Measurements were made between 7-10 weeks. Using ambulation on a treadmill, the pattern and magnitude of strain measured in the tibia remained relatively constant between 7-10 weeks post implantation. That strain levels were similar at 7 and 10 weeks suggests that gauge bonding is stable. These data demonstrate that CPC-coated strain gauges can be used to accurately measure bone strain for extended periods, and provide an in vivo assessment of tibial strain levels during normal ambulation in the rat.

Osteoblasts respond to pulsatile fluid flow with short-term increases in PGE(2) but no change in mineralization

Although there is no consensus as to the precise nature of the mechanostimulatory signals imparted to the bone cells during remodeling, it has been postulated that deformation-induced fluid flow plays a role in the mechanotransduction pathway. In vitro, osteoblasts respond to fluid shear stress with an increase in PGE(2) production; however, the long-term effects of fluid shear stress on cell proliferation and differentiation have not been examined. The goal of this study was to apply continuous pulsatile fluid shear stresses to osteoblasts and determine whether the initial production of PGE(2) is associated with long-term biochemical changes. The acute response of bone cells to a pulsatile fluid shear stress (0.6 +/- 0.5 Pa, 3.0 Hz) was characterized by a transient fourfold increase in PGE(2) production. After 7 days of static culture (0 dyn/cm(2)) or low (0.06 +/- 0.05 Pa, 0.3 Hz) or high (0.6 +/- 0.5 Pa, 3.0 Hz) levels of pulsatile fluid shear stress, the bone cells responded with an 83% average increase in cell number, but no statistical difference (P > 0.53) between the groups was observed. Alkaline phosphatase activity per cell decreased in the static cultures but not in the low- or high-flow groups. Mineralization was also unaffected by the different levels of applied shear stress. Our results indicate that short-term changes in PGE(2) levels caused by pulsatile fluid flow are not associated with long-term changes in proliferation or mineralization of bone cells.