Larson, Dirk R.

Objective: To determine the optimal environmental conditions for chondrogenic differentiation of human adipose tissue–derived mesenchymal stromal/stem cells (AMSCs). In this investigation we specifically investigate the role of oxygen tension and 3-dimensional (3D) culture systems. Design: Both AMSCs and primary human chondrocytes were cultured for 21 days in chondrogenic media under normoxic (21% oxygen) or hypoxic (2% oxygen) conditions using 2 distinct 3D culture methods (high-density pellets and poly-ε-caprolactone [PCL] scaffolds). Histologic analysis of chondro-pellets and the expression of chondrocyte-related genes as measured by reverse transcriptase quantitative polymerase chain reaction were used to evaluate the efficiency of differentiation. Results: AMSCs are capable of expressing established cartilage markers including COL2A1, ACAN, and DCN when grown in chondrogenic differentiation media as determined by gene expression and histologic analysis of cartilage markers. Expression of several cartilage-related genes was enhanced by low oxygen tension, including ACAN and HAPLN1. The pellet culture environment also promoted the expression of hypoxia-inducible cartilage markers compared with cells grown on 3D scaffolds. Conclusions: Cell type–specific effects of low oxygen and 3D environments indicate that mesenchymal cell fate and differentiation potential is remarkably sensitive to oxygen. Genetic programming of AMSCs to a chondrocytic phenotype is effective under hypoxic conditions as evidenced by increased expression of cartilage-related biomarkers and biosynthesis of a glycosaminoglycan-positive matrix. Lower local oxygen levels within cartilage pellets may be a significant driver of chondrogenic differentiation.

Background: Reconstruction of anterior cruciate ligament (ACL) tears may potentially prevent the development of secondary meniscal injuries and arthritis. Purpose/Hypothesis: The purpose of this study was to (1) evaluate the protective benefit of ACL reconstruction (ACLR) in preventing subsequent meniscal tears or arthritis, (2) determine if earlier ACLR (<1 year after injury) offers greater protective benefits than delayed reconstruction (≥1 year after injury), and (3) evaluate factors predictive of long-term sequelae after ACLR. The hypothesis was that the incidence of secondary meniscal tears, arthritis, and total knee arthroplasty (TKA) would be higher in patients treated nonoperatively after ACL tears than patients treated with surgical reconstruction. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective study included a population-based incidence cohort of 964 patients with new-onset, isolated ACL tears between 1990 and 2000 as well as an age- and sex-matched cohort of 964 patients without ACL tears. A chart review was performed to collect information related to the initial injury, treatment, and outcomes. A total of 509 patients were treated with early ACLR, 91 with delayed ACLR, and 364 nonoperatively. All patients were retrospectively followed (range, 2 months to 25 years) to determine the development of subsequent meniscal tears, arthritis, or TKA. Results: At a mean follow-up of 13.7 years, patients treated nonoperatively after ACL tears had a significantly higher likelihood of developing a secondary meniscal tear (hazard ratio [HR], 5.4; 95% CI, 3.8-7.6), being diagnosed with arthritis (HR, 6.0; 95% CI, 4.3-8.4), and undergoing TKA (HR, 16.7; 95% CI, 5.0-55.2) compared with patients treated with ACLR. Similarly, patients treated with delayed ACLR had a higher likelihood of developing a secondary meniscal tear (HR, 3.9; 95% CI, 2.2-6.9) and being diagnosed with arthritis (HR, 6.2; 95% CI, 3.4-11.4) compared with patients treated with early ACLR. Age >21 years at the time of injury, articular cartilage damage, and medial/lateral meniscal tears were predictive of arthritis after ACLR. Conclusion: Patients treated with ACLR have a significantly lower risk of secondary meniscal tears, symptomatic arthritis, and TKA when compared with patients treated nonoperatively after ACL tears. Similarly, early ACLR significantly reduces the risk of subsequent meniscal tears and arthritis compared with delayed ACLR.

Background: The incidence of isolated anterior cruciate ligament (ACL) tears in the general population is not well defined. Purpose/Hypothesis: The purpose of this study was to define the population-based incidence of ACL tears, describe trends in ACL injuries over time, and evaluate changes in the rate of surgical management. The hypothesis was that the incidence of ACL injury and the rate of subsequent ACL reconstruction increase over time. Study Design: Cohort study; Level of evidence, 3. Methods: The study population included 1841 individuals who were diagnosed with new-onset, isolated ACL tears (without concomitant ligament injury that required surgery) between January 1, 1990, and December 31, 2010. The complete medical records were reviewed to confirm diagnosis and to extract injury and treatment details. Age- and sex-specific incidence rates were calculated and adjusted to the 2010 US population. Poisson regression analyses were performed to examine incidence trends by age, sex, and calendar period. Results: The overall age- and sex-adjusted annual incidence of ACL tears was 68.6 per 100,000 person-years. Incidence was significantly higher in male patients than in females (81.7 vs 55.3 per 100,000, P < .001). The incidence of isolated ACL tears decreased significantly over time in males ( P < .001) but remained relatively stable in females. Age-specific patterns differed in male and female patients, with a peak in incidence (241.0 per 100,000) between 19 and 25 years in males and a peak in incidence (227.6 per 100,000) between 14 and 18 years in females. The rate of ACL reconstruction increased significantly over time in all age groups ( P < .001). Conclusion: With an annual incidence of 68.6 per 100,000 person-years, isolated ACL tears remain a common orthopaedic injury. Differences in age-specific incidence trends in male and female patients may potentially reflect differences in sports participation patterns through the high school and college years. The significant increase in the rate of ACL reconstruction over time may reflect changing surgical indications or an increasing desire among patients to return to high levels of activity after ACL injury.

Abstract The incidence of multiple myeloma (MM) is twice as high in blacks compared with whites. MM consists of several different cytogenetic subtypes, with differing presentations, response to therapy, and prognosis. The studies that have characterized the distribution of the primary cytogenetic abnormalities by fluorescence in-situ hybridization (FISH) testing have been primarily conducted in white populations, and more data are needed on whether the distribution of these cytogenetic abnormalities differs in black compared with white MM patients, and to determine if the increased prevalence of MM in blacks is related to specific subtypes of the disease. In this multi-center study, we examined four common clinically assessed cytogenetic subtypes (t(11;14), t(4;14), del13q, and del17p) at time of MM diagnosis in 245 black patients from 3 clinics who had prior FISH testing available in medical records. We compared the prevalence of these subtypes with our previously characterized Mayo Clinic cohort which was all Caucasian (n=484). The t(11;14) translocation was seen in 9 of 245 (4%) black patients with MM; this was significantly lower than the rate of t(11;14) translocations seen in white patients from Mayo Clinic (18%), p &lt; 0.0001). In contrast to t(11;14), the prevalence of the t(4;14) translocation across the two groups was similar (p= 0.92). We conclude that the prevalence of t(11;14) translocation is significantly lower in blacks with myeloma compared with whites. Our findings suggest that the distribution of cytogenetic subtypes found in MM may differ significantly by race, and further studies assessing differences in the prevalence of other primary cytogenetic abnormalities such as trisomies, t(6;14), t(14;16), and t(14;20) are needed. Furthermore, these results support the hypothesis previously put forth that there are several different subtypes of multiple myeloma that may be defined by the major cytogenetic translocations. Since these results differ from those previously reported (Baker et al 2013, Blood), we are conducting further analyses of these data to examine possible factors that could account for the differential association of translocation by race, including probes used. Citation Format: Alexandra Joelle Greenberg, Sunita Philip, Agne Paner, Sylvia Velinova, Ashraf Badros, Rosalind Catchatorian, Dirk Larson, Rhett Ketterling, Robert A. Kyle, Shaji Kumar, Celine M. Vachon, S. Vincent Rajkumar. Evidence of decreased prevalence of the t(11;14) translocation in black patients with multiple myeloma: A multi-center study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 272. doi:10.1158/1538-7445.AM2014-272

ABSTRACTCarpal tunnel syndrome (CTS) is a peripheral neuropathy characterized by non‐inflammatory fibrosis of the subsynovial connective tissues (SSCT). A rabbit model of CTS was developed to test the hypothesis that SSCT fibrosis causes the neuropathy. We used a cell‐seeded collagen‐gel contraction model to characterize the fibrosis in this model in terms of cellular mechanics, specifically to compare the ability of SSCT cells from the rabbit model and normal rabbits to contract the gel, and to assess the effect of transforming growth factor‐β1,which is upregulated in CTS, on these cells. SSCT fibrosis was induced in six retired breeder female rabbits which were sacrificed at 6 weeks (N = 3) and 12 weeks (n = 3). An additional two rabbits served as controls. SSCT was harvested according to a standard protocol. Gels seeded with SSCT cells from rabbits sacrificed at 6 weeks had significantly higher tensile strength (p < 0.001) and Young's modulus (p < 0.001) than gels seeded with cells from rabbits sacrificed at 12 weeks or control animals. TGF‐β1 significantly increased the decay time constant (p < 0.001), tensile strength (p < 0.001), and Young's modulus (p < 0.001) regardless of the cell source. This model may be useful in screening therapeutic agents that may block SSCT fibrosis, identifying possible candidates for CTS treatment. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:668–674, 2015.

Abstract Objective To determine the prognosis of patients with non‐secretory myeloma. Methods We studied 124 patients diagnosed with multiple myeloma who had no monoclonal protein detected on serum and urine immunofixation at diagnosis and on all subsequent follow‐up testing (non‐secretory myeloma). The overall survival ( OS ) of patients with non‐secretory myeloma was compared with 6953 patients with typical myeloma seen during the same time period in whom a monoclonal protein was detected at the time of diagnosis. Results One hundred and twenty‐four patients met criteria for non‐secretory multiple myeloma. The median follow‐up was 102 months (range, 1–204 months). The median progression‐free survival with initial therapy was 28.6 months, and the median OS was 49.3 months. There was a significant improvement in OS since 2001; median survival 43.8 months (prior to 2001) vs. 99.2 months (2001–2012), P < 0.001. OS was superior in patients with a normal baseline FLC ratio ( n = 10) compared to patients with an abnormal ratio ( n = 19), medians not reached in both groups. Prior to 2001, OS was similar in non‐secretory myeloma ( n = 86) and secretory myeloma ( n = 4011), median 3.6 vs. 3.5 yr, respectively, P = 0.63. However, among patients diagnosed between 2001 and 2012, OS was superior in non‐secretory myeloma ( n = 36) compared to secretory myeloma ( n = 2942), median 8.3 vs. 5.4 yr, respectively, P = 0.03. Conclusions Non‐secretory myeloma is an uncommon subtype of multiple myeloma. In the last decade, there has been an improvement in the survival of non‐secretory myeloma and appears superior to secretory myeloma.

Abstract The plasma cell malignancy Multiple Myeloma (MM) is a rare but deadly form of cancer with 5 year survival rates of ∼30%. Epidemiological studies have suggested that MM exacts an especially heavy burden on African American (AA) patients. We examined a multi-ethnic cohort of MM tumors to assess potential differences in the frequency of molecular events in tumors derived from either African American (AA) or European American (EA) patients. The frequency of 14q32 translocation breakpoints at the IgH locus was compared among a series of data from 115 AA MM patients from three studies and EA MM from the Eastern Cooperative Oncology Group (ECOG). In addition, we analyzed matching genome-wide copy number and transcriptional data among 45 AA MM tumors and 196 EA MM tumors to determine differences in the frequency of molecular events in tumors from these populations. No differences were found for specific translocation subtypes; however, we detected a statistically significant difference in the overall frequency of IgH translocations between the two groups, which occurred more frequently in EA patients (52% vs. 40%; p = 0.032). When assessing genomic copy number events previously shown to be associated with poor outcome in MM, frequencies of alterations were not significant after correcting for multiple testing. Furthermore, there was not a significant difference in the association of high-risk disease using expression profiling. Our study represents the first comprehensive assessment of the frequency and distribution of molecular alterations in MM tumors from both AA and EA patients and could help shed light on possible biological features associated with population differences in incidence and outcome in MM. Citation Format: Angela S. Baker, Esteban Braggio, Susana Jacobus, Sungwon Jung, Dirk Larson, Terry Therneau, Angela Dispenzieri, Scott A. Van Wier, Gregory Ahmann, Joan Levy, Louise Perkins, Seungchan Kim, Kim Henderson, David Vesole, S. Vincent Rajkumar, Dianne F. Jelinek, John Carpten, Rafael Fonseca. Characterization of myeloma tumors from a multi-ethnic cohort using cytogenetics and genomic analysis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2021. doi:10.1158/1538-7445.AM2013-2021

Key Points Survival in ET is superior to that of PV, regardless of mutational status, but remains inferior to the sex- and age-matched US population. JAK2/CALR/MPL mutational status is prognostically informative in PMF, regarding overall and leukemia-free survival.

AbstractNoninflammatory subsynovial connective tissue (SSCT) fibrosis with nerve compression is a prominent feature of carpal tunnel syndrome (CTS). Studies have shown that SSCT matrix synthesis and material property changes in CTS are associated with increased activity of transforming growth factor (TGF)‐β1. The aim of this study were to (1) investigate the ability of SSCT fibroblasts from CTS patients and unaffected individuals to contract a collagen gel ring and (2) determine how the addition of TGF‐β1 affects this ability. SSCT fibroblasts from three normal cadavers and three age‐matched female patients who had undergone surgery for CTS were used. Results showed patient cell‐seeded gels had a significantly higher contraction rate (p < 0.001) than control cells, and fully contracted gel rings possessed a significantly higher tensile strength (p = 0.003) and stiffness (p < 0.001). Furthermore, TGF‐β1 significantly intensified contraction rate (p < 0.001), tensile strength (p < 0.001), and stiffness (p < 0.001). In conclusion, SSCT cells from normal donors and CTS patients contract collagen gel rings differently, and this ability is affected by TGF‐β1 treatment. This cell‐seeded collagen gel model may be useful for developing new methods of stopping or eliminating the effect of TGF‐β1 on the SSCT fibroblasts and surrounding matrix, which might aid in the identification of medical treatment for CTS. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 574–580, 2015.

A significant issue in research on the epidemiology of injury relates not to the numerator (injury), but to the denominator: exposure time. Most hockey injury studies “assume” equivalent playing time. This assumption is not problematic for large investigations designed to establish differences in concussion rates between levels of participation. However, the assumption is a serious issue when investigators are testing differences in rules, coaching programs, skills training, and behavioral interventions. Because players are at higher risk for injuries when fatigued, individual exposure time is important. Until recently, analyzing individual playing times for ice hockey teams has been a daunting task, as it involved the hand-written recording of times using a grid and check marks. During the 2011–2012 season, a computer-based program, Time on Ice (TOI), was used to expedite the accurate recording of individual exposure, including shorthanded and power-play situations. The purpose of using TOI software in this study was to ensure that its results were in agreement with the exposure times recorded manually using a paper-and-pencil grid. Preliminary results from six games (12 records of data) showed that exposure time ranged from 6.3 to 26.4 min when using manual recording and 8.3 to 33.2 min when using TOI. These methods were concluded to be in agreement. Now that software has been developed exclusively for the task of tracking time on ice, it is recommended that exposure time be measured when injuries such as concussion are being evaluated and causation is being determined. The Sport Performance Analyzer TOI system is commercially available.