Sex specific emergence of trisomic Dyrk1a -related skeletal phenotypes in the development of a Down syndrome mouse model.

Skeletal insufficiency affects all individuals with Down syndrome (DS) or Trisomy 21 (Ts21) and may alter bone strength throughout development due to a reduced period of bone formation and early attainment of peak bone mass compared to typically developing individuals. Appendicular skeletal deficits also appear in males before females with DS. In femurs of male Ts65Dn DS model mice, cortical deficits were pronounced throughout development, but trabecular deficits and Dyrk1a overexpression were transitory until postnatal day (P) 30 when there were persistent trabecular and cortical deficits and Dyrk1a was trending overexpression. Correction of DS-related skeletal deficits by a purported DYRK1A inhibitor or through genetic means beginning at P21 was not effective at P30, but germline normalization of Dyrk1a improved male bone structure by P36. Trabecular and cortical deficits in female Ts65Dn mice were evident at P30 but subsided by P36, typifying periodic developmental skeletal normalizations that progressed to more prominent bone deficiencies. Sex-dependent differences in skeletal deficits with a delayed impact of trisomic Dyrk1a are important to find temporally specific treatment periods for bone and other phenotypes associated with Ts21. Summary Statement: Analyzing developing bone and gene expression in Ts65Dn Down syndrome model mice revealed timepoints during development when trisomic Dyrk1a overexpression linked to appendicular skeletal abnormalities. Dyrk1a was not always overexpressed.

Increased dosage and treatment time of Epigallocatechin-3-gallate (EGCG) negatively affects skeletal parameters in normal mice and Down syndrome mouse models.

Bone abnormalities affect all individuals with Down syndrome (DS) and are linked to abnormal expression of DYRK1A, a gene found in three copies in people with DS and Ts65Dn DS model mice. Previous work in Ts65Dn male mice demonstrated that both genetic normalization of Dyrk1a and treatment with ~9 mg/kg/day Epigallocatechin-3-gallate (EGCG), the main polyphenol found in green tea and putative DYRK1A inhibitor, improved some skeletal deficits. Because EGCG treatment improved mostly trabecular skeletal deficits, we hypothesized that increasing EGCG treatment dosage and length of administration would positively affect both trabecular and cortical bone in Ts65Dn mice. Treatment of individuals with DS with green tea extract (GTE) containing EGCG also showed some weight loss in individuals with DS, and we hypothesized that weights would be affected in Ts65Dn mice after EGCG treatment. Treatment with ~20 mg/kg/day EGCG for seven weeks showed no improvements in male Ts65Dn trabecular bone and only limited improvements in cortical measures. Comparing skeletal analyses after ~20mg/kg/day EGCG treatment with previously published treatments with ~9, 50, and 200 mg/kg/day EGCG showed that increased dosage and treatment time increased cortical structural deficits leading to weaker appendicular bones in male mice. Weight was not affected by treatment in mice, except for those given a high dose of EGCG by oral gavage. These data indicate that high doses of EGCG, similar to those reported in some treatment studies of DS and other disorders, may impair long bone structure and strength. Skeletal phenotypes should be monitored when high doses of EGCG are administered therapeutically.

Skeletal Deficits in Male and Female down Syndrome Model Mice Arise Independent of Normalized Dyrk1a Expression in Osteoblasts.

Trisomy 21 (Ts21) causes alterations in skeletal development resulting in decreased bone mass, shortened stature and weaker bones in individuals with Down syndrome (DS). There is a sexual dimorphism in bone mineral density (BMD) deficits associated with DS with males displaying earlier deficits than females. The relationships between causative trisomic genes, cellular mechanisms, and influence of sex in DS skeletal abnormalities remain unknown. One hypothesis is that the low bone turnover phenotype observed in DS results from attenuated osteoblast function, contributing to impaired trabecular architecture, altered cortical geometry, and decreased mineralization. DYRK1A, found in three copies in humans with DS, Ts65Dn, and Dp1Tyb DS model mice, has been implicated in the development of postnatal skeletal phenotypes associated with DS. Reduced copy number of Dyrk1a to euploid levels from conception in an otherwise trisomic Ts65Dn mice resulted in a rescue of appendicular bone deficits, suggesting DYRK1A contributes to skeletal development and homeostasis. We hypothesized that reduction of Dyrk1a copy number in trisomic osteoblasts would improve cellular function and resultant skeletal structural anomalies in trisomic mice. Female mice with a floxed Dyrk1a gene (Ts65Dn,Dyrk1afl/wt) were mated with male Osx-Cre+ (expressed in osteoblasts beginning around E13.5) mice, resulting in reduced Dyrk1a copy number in mature osteoblasts in Ts65Dn,Dyrk1a+/+/Osx-Cre P42 male and female trisomic and euploid mice, compared with littermate controls. Male and female Ts65Dn,Dyrk1a+/+/+ (3 copies of DYRK1A in osteoblasts) and Ts65Dn,Dyrk1a+/+/Osx-Cre (2 copies of Dyrk1a in osteoblasts) displayed similar defects in both trabecular architecture and cortical geometry, with no improvements with reduced Dyrk1a in osteoblasts. This suggests that trisomic DYRK1A does not affect osteoblast function in a cell-autonomous manner at or before P42. Although male Dp1Tyb and Ts65Dn mice exhibit similar skeletal deficits at P42 in both trabecular and cortical bone compartments between euploid and trisomic mice, female Ts65Dn mice exhibit significant cortical and trabecular deficits at P42, in contrast to an absence of genotype effect in female Dp1Tyb mice in trabecular bone. Taken together, these data suggest skeletal deficits in DS mouse models and are sex and age dependent, and influenced by strain effects, but are not solely caused by the overexpression of Dyrk1a in osteoblasts. Identifying molecular and cellular mechanisms, disrupted by gene dosage imbalance, that are involved in the development of skeletal phenotypes associated with DS could help to design therapies to rescue skeletal deficiencies seen in DS.

Current Analysis of Skeletal Phenotypes in Down Syndrome.

PURPOSE: Down syndrome (DS) is caused by trisomy 21 (Ts21) and results in skeletal deficits including shortened stature, low bone mineral density, and a predisposition to early onset osteoporosis. Ts21 causes significant alterations in skeletal development, morphology of the appendicular skeleton, bone homeostasis, age-related bone loss, and bone strength. However, the genetic or cellular origins of DS skeletal phenotypes remain unclear. RECENT FINDINGS: New studies reveal a sexual dimorphism in characteristics and onset of skeletal deficits that differ between DS and typically developing individuals. Age-related bone loss occurs earlier in the DS as compared to general population. Perturbations of DS skeletal quality arise from alterations in cellular and molecular pathways affected by the overexpression of trisomic genes. Sex-specific alterations occur in critical developmental pathways that disrupt bone accrual, remodeling, and homeostasis and are compounded by aging, resulting in increased risks for osteopenia, osteoporosis, and fracture in individuals with DS.

Interaction of sexual dimorphism and gene dosage imbalance in skeletal deficits associated with Down syndrome.

All individuals with Down syndrome (DS), which results from trisomy of human chromosome 21 (Ts21), present with skeletal abnormalities typified by craniofacial features, short stature and low bone mineral density (BMD). Differences in skeletal deficits between males and females with DS suggest a sexual dimorphism in how trisomy affects bone. Dp1Tyb mice contain three copies of all of the genes on mouse chromosome 16 that are homologous to human chromosome 21, males and females are fertile, and therefore are an excellent model to test the hypothesis that gene dosage influences the sexual dimorphism of bone abnormalities in DS. Dp1Tyb as compared to control littermate mice at time points associated with bone accrual (6 weeks) and skeletal maturity (16 weeks) showed deficits in BMD and trabecular architecture that occur largely through interactions between sex and genotype and resulted in lower percent bone volume in all female and Dp1Tyb male mice. Cortical bone in Dp1Tyb as compared to control mice exhibited different changes over time influenced by sex × genotype interactions including reduced cortical area in both male and female Dp1Tyb mice. Mechanical testing analyses suggested deficits in whole bone properties such as bone mass and geometry, but improved material properties in female and Dp1Tyb mice. Sexual dimorphisms and the influence of trisomic gene dosage differentially altered cellular properties of male and female Dp1Tyb bone. These data establish sex, gene dosage, skeletal site and age as important factors in skeletal development of DS model mice, paving the way for identification of the causal dosage-sensitive genes. Skeletal differences in developing male and female Dp1Tyb DS model mice replicated differences in less-studied adolescents with DS and established a foundation to understand the etiology of trisomic bone deficits.

Post-operative urinary retention after lower extremity arthroplasty and the peri-operative role of selective alpha-1 adrenergic blocking agents in adult male patients: a propensity-matched retrospective cohort study.

PURPOSE: The purpose of this study was to determine whether male patients taking pre-operative selective alpha-1 adrenergic blocking agents have a lower likelihood of developing post-operative urinary retention (POUR) and a shorter length of hospitalization following lower extremity arthroplasty. METHODS: A retrospective cohort study was conducted of patients who underwent primary or revision total hip or knee arthroplasty, or unicompartmental knee arthroplasty at an academic institution from January 2002 to May 2014. A cohort of male patients aged 35 and older who were taking a selective alpha-1 blocker prior to surgery (N = 229) were compared with a control group (N = 330) not taking one of these medications. Propensity score-matched logistic regression was performed to isolate the effect of taking a selective alpha-1 blocker on POUR. RESULTS: When evaluating for the outcome of POUR while controlling for age, hypertension, benign prostatic hyperplasia, urinary tract infections, type of anaesthesia, and procedure, those patients taking an alpha-1 blocker had a 12.1% decreased relative risk (95% CI 3.4 to 20.8%; p = 0.007) of developing POUR compared with patients not taking these medications. Mean length of stay was 3.8 days (95% CI 3.6 to 4.1) in the cohort taking selective alpha-1 blockers compared with 4.7 days (95% CI 4.4 to 4.9) for the control cohort. CONCLUSIONS: After controlling for known risk factors for the development of POUR, the use of selective alpha-1 blockers pre-operatively reduces the risk of developing urinary retention after lower extremity arthroplasty and is associated with a 1-day decreased length of stay.

The AAHKS Clinical Research Award: Prophylactic Tamsulosin Does Not Reduce the Risk of Urinary Retention Following Lower Extremity Arthroplasty: A Double-Blinded Randomized Controlled Trial.

BACKGROUND: Postoperative urinary retention (POUR) is common. Selective alpha-1 adrenergic antagonists, such as tamsulosin, are effective for treating urinary retention. The purpose of this study is to determine whether perioperative prophylactic tamsulosin reduces the incidence of POUR following total hip and knee arthroplasty. METHODS: Male patients 35 years of age and older undergoing primary total hip or knee arthroplasty at a single center from 2015 to 2018 were eligible for inclusion. Patients were randomized to receive tamsulosin 0.4 mg or placebo daily for 5 days preoperatively, the morning of surgery, and the first postoperative day. The incidence of POUR was determined during the postoperative hospitalization. RESULTS: A total of 176 patients were enrolled in the study. Two patients were withdrawn prior to randomization. The remaining 174 were randomized to tamsulosin (n = 87) or placebo (n = 87). After an additional 43 patients were withdrawn prior to surgery, 131 patients completed the study (tamsulosin, n = 64; placebo, n = 67). A total of 42 patients (32.1%) developed POUR, with 18 cases (28.1%) in the tamsulosin group and 24 cases (35.8%) in the placebo group (P = .345), resulting in an odds ratio of 0.701 and a risk difference of 7.69%. CONCLUSION: Prophylactic tamsulosin did not reduce the incidence of POUR after hip and knee arthroplasty compared to placebo. The odds ratio indicates an approximately 30% decreased odds of developing POUR in the tamsulosin group, albeit not statistically significant. Tamsulosin does not appear to be effective as a prophylactic measure for reducing POUR in male hip and knee arthroplasty patients.

Return to Play After Osteochondral Autograft Transplantation of the Capitellum: A Systematic Review.

PURPOSE: To determine the rate of return to play and to identify lesion or osteochondral graft characteristics that may influence the return to competitive athletics after osteochondral autograft transplantation (OAT) for symptomatic osteochondritis dissecans (OCD) lesions. METHODS: A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A duplicate search of PubMed, Embase, Scopus, Web of Science, and CENTRAL databases was performed, beginning from the database inception dates through July 2016, for all articles evaluating the return to play after OAT for OCD lesions of the capitellum. A methodological quality assessment was completed for all included studies. Patient demographics, osteochondral lesion and graft characteristics, the number of patients, and timing of return to competitive activity were collected and evaluated. Association between graft size/number, the time to osseous healing, and return to sport was evaluated. RESULTS: Seven articles met the inclusion criteria. All included studies were case series of moderate quality with a mean Methodological Index for Non-Randomized Studies score of 12/16. Overall, 94% (119/126) of patients undergoing OAT for OCD lesions of the capitellum successfully returned to competitive sports. The mean reported time for unrestricted return to athletic competition after OAT was 5.6 months (range, 3-14 months). CONCLUSIONS: Current best evidence suggests that OAT is successful in treating advanced OCD lesions of the capitellum and returning athletes to high-level competition. Evidence supporting the association between the size and number of grafts used and the time to osseous healing and return to sport is currently limited. Our assessment of the time to return to athletic competition was limited because of variable surgical technique, postoperative rehabilitation protocols, and outcome assessment. LEVEL OF EVIDENCE: Level IV, systematic review of Level IV studies.

Biceps and Triceps Ruptures in Athletes.

Although rare, biceps and triceps tendon ruptures constitute significant injuries that can lead to profound disability if left untreated, especially in the athletic population. Biceps rupture is more common than triceps rupture, with both resulting from a forceful eccentric load. Surgical repair is the treatment method of choice for tendinous ruptures in athletes. Nonoperative management is rarely indicated in this population and is typically reserved for individuals with partial ruptures that quickly regain strength and function. Surgical anatomy, evaluation, diagnosis, and surgical management of these injuries are covered in this article.