Associations between childhood maltreatment and physiological dysregulation in adulthood: Methodological decisions and implications.

BACKGROUND: Childhood maltreatment is linked with health problems in adulthood. Theoretical models suggest that maltreatment leads to dysregulation in several bodily systems, and this has been corroborated using measures of physiological function (i.e., biomarkers). Methodological decisions involving the measurement of maltreatment and dimension reduction with respect to biomarkers (i.e., combining information across multiple measures) may influence research findings. OBJECTIVE: The present study compares associations between childhood maltreatment and adult physiological dysregulation using multiple dimension reduction approaches and measures of maltreatment. PARTICIPANTS AND SETTING: Participants were recruited, as children, to a prospective study of the correlates and consequences of childhood maltreatment. 253 participants were retained and provided biomarker data at midlife. Physiological dysregulation was operationalized with a conventional allostatic load approach and a novel statistical distance approach. METHODS: Regression models were employed with allostatic load or statistical distance as the outcome and prospectively or retrospectively measured child maltreatment as the primary predictor. RESULTS: When using allostatic load as the outcome, prospectively measured childhood maltreatment was positively associated with physiological dysregulation (b = 0.70, SE = 0.31, p = 0.02). When using statistical distance as the outcome, retrospectively measured childhood maltreatment was positively associated with physiological dysregulation (b = 0.69, SE = 0.19 p < 0.001). CONCLUSIONS: We report a positive association between childhood maltreatment and physiological dysregulation at midlife. However, the significance and magnitude of effects varied with different maltreatment and physiological dysregulation measures. Further review of the methods used to study adult health conditions and their relation to childhood maltreatment is needed.

Importance of Control Groups for Evaluating Long-Term Behavioral and Cognitive Outcomes of Controlled Cortical Impact in Immature Rats.

Therapies are limited for pediatric traumatic brain injury (TBI), especially for the very young who can experience long-term consequences to learning, memory, and social behavior. Animal models of pediatric TBI have yielded mechanistic insights, but demonstration of clinically relevant long-term behavioral and/or cognitive deficits has been challenging. We characterized short- and long-term outcomes in a controlled cortical impact (CCI) model of pediatric TBI using a panel of tests between 2 weeks and ∼4 months after injury. Male rats with CCI at postnatal Day (PND) 10 were compared with three control groups: Naïve, Anesthesia, and Craniotomy. Motor testing (PND 25-33), novel object recognition (NOR; PND 40-50), and multiple tasks in water maze (WM; PND 65-100) were followed by social interaction tests (PND 120-140). Anesthesia rats performed the same as Naïve rats in all tasks. TBI rats, when compared with Naïve controls, had functional impairments across most tests studied. The most sensitive cognitive processes affected by TBI included those that required fast one-trial learning (NOR, WM), flexibility of acquired memory traces (reversals in WM), response strategies (WM), or recognition memory in the setting of reciprocal social interactions. Both TBI and Craniotomy groups demonstrated increased rates of decision making across several WM tasks, suggesting disinhibition of motor responses. When the TBI group was compared with the Craniotomy group, however, deficits were detected in a limited number of outcomes. The latter included learning speed (WM), cognitive flexibility (WM), and social recognition memory. Notably, effects of craniotomy, when compared with Naïve controls, spanned across multiple tasks, and in some tasks, could reach the effect sizes observed in TBI. These results highlight the importance of appropriate control groups in pediatric CCI models. In addition, the study demonstrates the high sensitivity of comprehensive cognitive testing to detect long-term effects of early-age craniotomy and TBI and provides a template for future testing of experimental therapies.

Predictors of maternal-origin microchimerism in young women in the Philippines.

OBJECTIVES: Microchimerism is the presence of a small quantity of cells or DNA from a genetically distinct individual. This phenomenon occurs with bidirectional maternal-fetal exchange during pregnancy. Microchimerism can persist for decades after delivery and have long-term health implications. However, little is known about why microchimerism is detectable at varying levels in different individuals. We examine the variability and the following potential determinants of maternal-origin microchimerism (MMc) in young women in the Philippines: gestational duration (in utero exposure to MMc), history of being breastfed (postpartum exposure to MMc), maternal telomere length (maternal cells' ability to replicate and persist), and participant's pregnancies in young adulthood (effect of adding fetal-origin microchimerism to preexisting MMc). MATERIALS AND METHODS: Data are from the Cebu Longitudinal Health and Nutrition Survey, a population-based study of infant feeding practices and long-term health outcomes. We quantified MMc using quantitative PCR (qPCR) in 89 female participants, ages 20-22, and analyzed these data using negative binomial regression. RESULTS: In a multivariate model including all predictors, being breastfed substantially predicted decreased MMc (detection rate ratio = 0.15, p = 0.007), and there was a trend of decreasing MMc in participants who had experienced more pregnancies (detection rate ratio = 0.55, p = 0.057). DISCUSSION: These results might be explained by breastfeeding having lasting impact on immune regulatory networks, thus reducing MMc persistence. MMc may also decrease in response to the introduction of fetal-origin microchimerism with pregnancies experienced in adulthood.

A Neutrophil Activation Biomarker Panel in Prognosis and Monitoring of Patients With Rheumatoid Arthritis.

OBJECTIVE: Exaggerated neutrophil activation and formation of neutrophil extracellular traps (NETs) are linked to inflammation and autoimmunity, including rheumatoid arthritis (RA). However, whether NETs are present in the circulation of RA patients and contribute to inflammation and disease progression has not been carefully addressed. We undertook this study to assess markers of neutrophil activation and NET formation in plasma samples, investigating whether they add clinical value in improving the determination of prognosis and monitoring in RA patients. METHODS: Markers of neutrophil activation (calprotectin) and cell death (NETs) were analyzed, using enzyme-linked immunosorbent assay, in serum and plasma obtained from patients in 3 cross-sectional RA cohorts and sex-matched healthy controls. A longitudinal inception cohort (n = 247), seen for a median follow-up of 8 years, was used for predictive analyses. RESULTS: Markers of neutrophil activation and cell death were increased in RA patients compared to healthy individuals (P < 0.0001). Calprotectin levels correlated with the Clinical Disease Activity Index (r = 0.53, P < 0.0001) and could be used to distinguish between patients with disease in remission and those with active disease, an observation not seen when examining C-reactive protein levels. A biomarker panel consisting of anti-citrullinated protein antibody and calprotectin could predict erosive disease (odds ratio [OR] 7.5, P < 0.0001) and joint space narrowing (OR 4.9, P = 0.001). NET levels were associated with markers of inflammation (P = 0.0002). Furthermore, NETs and a "neutrophil activation signature" biomarker panel had good predictive value in identifying patients who were developing extraarticular nodules (OR 5.6, P = 0.006). CONCLUSION: Neutrophils undergo marked activation and cell death in RA. Neutrophil biomarkers can provide added clinical value in the monitoring and prognosis of RA patients and may allow for early preventive treatment intervention.

Disease progression in relation to pre-onset parity among women with rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) often ameliorates during pregnancy and flares postpartum, but the relationship of pregnancy and childbirth to RA prognosis is unclear. We examined RA severity for association with parity prior to RA onset and asked whether time from birth (latency) and/or the mother's HLA genotype influenced results. METHODS: A cohort study was conducted of 222 women previously identified in a prospective study of newly diagnosed RA, who returned for follow-up evaluation a median of 8 years later. Stratified analyses using Mantel-Haenszel methods were conducted to evaluate 5 RA severity measures based on hand and wrist radiographs, physical exams, and Health Assessment Questionnaires for association with parity. RESULTS: Overall, we observed little evidence of altered risk of progression to severe RA in relation to pre-onset parity, adjusting for RA onset age and time to follow-up. Stratifying parous women who had only live births by latency (<15 years/15+ years) showed no difference in risk of severe RA compared to nulligravid women. Live birth deliveries were significantly protective for women with 0 but not for those with 1 or 2 copies of the RA risk-associated HLA-DRB1 shared epitope sequence for erosion score (RR 0.26 95% CI 0.09-0.89) and joint count (RR 0.28 95% CI 0.09-0.87). CONCLUSION: We observed little evidence of difference in severe RA by pre-onset parity overall. However, among women not predisposed to RA by possessing the risk-associated HLA genotype, parous women who had only live births had lower risk of progression to severe RA as measured by erosion score and joint count.

Phosphatidylinositol-5-phosphate 4-kinase gamma accumulates at the spindle pole and prevents microtubule depolymerization.

BACKGROUND: A previous screen of a human kinase and phosphatase shRNA library to select genes that mediate arsenite induction of spindle abnormalities resulted in the identification of phosphatidylinositol-5-phosphate 4-kinase type-2 gamma (PIP4KIIγ), a phosphatidylinositol 4,5-bisphosphate (PIP2)-synthesizing enzyme. In this study, we explored how PIP4KIIγ regulates the assembly of mitotic spindles. RESULTS: PIP4KIIγ accumulates at the spindle pole before anaphase, and is required for the assembly of functional bipolar spindles. Depletion of PIP4KIIγ enhanced the spindle pole accumulation of mitotic centromere-associated kinesin (MCAK), a microtubule (MT)-depolymerizing kinesin, and resulted in a less stable spindle pole-associated MT. Depletion of MCAK can ameliorate PIP4KIIγ depletion-induced spindle abnormalities. In addition, PIP2 binds to polo-like kinase (PLK1) and reduces PLK1-mediated phosphorylation of MCAK. These results indicate that PIP4KIIγ and PIP2 may negatively regulate the MT depolymerization activity of MCAK by reducing PLK1-mediated phosphorylation of MCAK. Consequently, depletion of PLK1 has been shown to counteract the PIP4KIIγ depletion-induced instability of spindle pole-associated MT and cell resistance to arsenite. CONCLUSIONS: Our current results imply that PIP4KIIγ may restrain MT depolymerization at the spindle pole through attenuating PLK1-mediated activation of MCAK before anaphase onset.

False-Positive Rates for Nerve Conduction Studies and Ultrasound in Patients Without Clinical Signs and Symptoms of Carpal Tunnel Syndrome.

PURPOSE: The purpose of the study was to determine the rate of false positives for nerve conduction studies (NCSs) and ultrasound (US) in a population without signs and symptoms of carpal tunnel syndrome (CTS) using a CTS-6 score of 0 as the reference standard. METHODS: Patients were included in this study if they were referred for NCSs for a reason other than CTS (cubital tunnel syndrome and/or cervical radiculopathy) and they had a CTS-6 score of 0. An US measurement of the cross-sectional area (CSA) of the median nerve at the level of the carpal tunnel inlet was performed by a certified ultrasound technician. An a priori CSA cutoff of 10 mm2 or greater measured using US at the carpal tunnel inlet qualified as a positive diagnosis. The NCSs were performed and interpreted according to national standards by a certified electrodiagnostician. All patients in this study were considered to not have a diagnosis of CTS based on the CTS-6 of 0. RESULTS: Forty hands with a CTS-6 of 0 were included in this study. The US was positive in 9 of 40(23%) and NCS was positive in 17 of 40 (43%). There were only 2 patients with a false-positive US that did not also have a positive NCS. However, there were 11 patients who had a false-positive NCS that did not have a positive US. CONCLUSIONS: This prospective cohort series has demonstrated that US has a lower false-positive rate than NCSs in asymptomatic patients as measured by the CTS-6 diagnostic tool. Studies with a low false-positive rate are preferred when ordering a confirmatory diagnostic test. Therefore, if a confirmatory diagnostic test is desired, we recommend that US be used rather than NCSs. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.

Baseline Characteristics of the Median Nerve on Ultrasound Examination.

Background: Previous studies using ultrasound for diagnosis of carpal tunnel syndrome have reported on relatively small series of patients, leading to large standard deviations and/or confidence intervals for the mean cross-sectional area of the median nerve. The purpose of this study is to define the CSA of the median nerve in a large cohort of patients. Methods: Patients (n = 175) without history of carpal tunnel release were recruited. All participants were evaluated using the Carpal Tunnel Syndrome-6 questionnaire, a validated clinical diagnostic tool, with a score of 12 or greater considered positive for CTS. Ultrasound examination was performed on both wrists of all participants using a 13-6 MHz linear array transducer. Results: The mean median nerve CSA was significantly larger (P < .001) for patients with a positive (mean = 11.16, SD = 2.51) versus negative CTS-6 result (mean = 6.91, SD = 2.06). There was a significant correlation (.527, P < .001, n = 349) between CSA and CTS-6 score. Logistic regression analysis determined that a CSA of 10 mm2 optimized sensitivity and specificity at 80% and 88%, respectively. Accuracy was 87.9%. Conclusions: A significant difference in mean CSA was found between patients with and without CTS. Median nerve CSA showed a statistically significant positive correlation with CTS-6. Similar to prior studies, a CSA of 10 mm2 was determined to be the optimal cutoff. In this large series of patients, ultrasound was a sensitive, specific, and accurate test for confirmation of a clinical diagnosis of CTS.

Geriatric distal femur fracture: Are we underestimating the rate of local and systemic complications?

BACKGROUND: Low energy distal femur fractures often occur in a fragile elderly population that is prone to local and systemic complications following operative treatment of extremity fractures. The nonunion rate and early complication rate following laterally based locked plating in this specific fracture are not well described. METHODS: We conducted a retrospective cohort study conducted at three affiliated tertiary care hospitals to evaluate nonunion, early post operative complications, discharge disposition, length of stay, and mortality in patients over 60 years old undergoing laterally based locked plating of a low energy distal femur fracture. RESULTS: Forty-four out of 176 patients were deceased at one year (25%). Predictors of one year mortality included older age, higher Charlson Comorbidity Index (CCI), and delay to surgery greater than 2days (p<0.001). Of 99 patients alive and with follow up at one year, 24 (24%) developed a nonunion and 21 of 24 required nonunion surgery. Development of a surgical site infection was statistically significantly correlated with development of nonunion. Age and CCI did not predict development of nonunion. Average length of stay was 10days and 82% of patients were discharged to a skilled nursing facility. Thirty eight percent of patients experienced at least one postoperative systemic complication. CONCLUSIONS: Laterally based locked plating of the low energy geriatric distal femur fracture is most often followed by a tumultuous post-operative course with a high rate of local and systemic complications including death, nonunion, and extended hospital stays. LEVEL OF EVIDENCE: Level III prognostic.

HSP70 regulates the function of mitotic centrosomes.

To establish a functional bipolar mitotic spindle, the centrosome expands and matures, acquiring enhanced activities for microtubule (MT) nucleation and assembly at the onset of mitosis. However, the regulatory mechanisms of centrosome maturation and MT assembly from the matured centrosome are largely unknown. In this study, we showed that heat shock protein (HSP) 70 considerably accumulates at the mitotic centrosome during prometaphase to metaphase and is required for bipolar spindle assembly. Inhibition or depletion of HSP70 impaired the function of mitotic centrosome and disrupted MT nucleation and polymerization from the spindle pole, and may thus result in formation of abnormal mitotic spindles. In addition, HSP70 may associate with NEDD1 and γ-tubulin, two pericentriolar material (PCM) components essential for centrosome maturation and MT nucleation. Loss of HSP70 function disrupted the interaction between NEDD1 and γ-tubulin, and reduced their accumulation at the mitotic centrosome. Our results thus demonstrate a role for HSP70 in regulating centrosome integrity during mitosis, and indicate that HSP70 is required for the maintenance of a functional mitotic centrosome that supports the assembly of a bipolar mitotic spindle.

Bold, Sedentary Fathead Minnows Have More Parasites.

Parasites that rely on trophic transmission can manipulate the behavior of an intermediate host to compromise the host's antipredator competence and increase the probability of reaching the next host. Selection for parasite manipulation is diminished when there is significant risk of host death to causes other than consumption by a suitable definitive host for the parasite. Consequently, behavioral manipulation by parasites can be expected to be subtle. Ornithodiplostomum ptychocheilus (Op) is a trematode parasite that has a bird-snail-fish host life cycle. Fathead minnows are a common intermediate host of Op, where metacercariae encyst in the minnow brain. In this study, we report a link between metacercarial intensity and behavior in fathead minnows. In the field, we found that roaming distance by free-living minnows over 24 h was negatively correlated with parasite intensity. In the laboratory, we found that boldness in an open field test was positively correlated with parasite intensity. These parasite-induced behavioral changes may render infected minnows more susceptible to predators, which would serve to facilitate trophic transmission of parasites to the bird host.

Recurrent anterior cervical wound abscesses following cervical corpectomy and fusion surgery from an odontogenic source mimicking an esophageal perforation: a case report.

CONTEXT: Infection is an uncommon complication of anterior cervical spine surgery. Most deep postoperative infections are thought to be related to occult esophageal perforation. Direct inoculation from the oropharynx has not been previously reported in the literature. PURPOSE: The purpose of this study is to report a case of recurrent infection after anterior cervical decompression and fusion suspected to have resulted from direct communication between the oropharynx and deep neck space. STUDY DESIGN: This study is a case report. METHODS: This study included longitudinal clinical and radiological follow-up. RESULTS: A 48-year-old woman who underwent anterior cervical corpectomy and fusion from C3 to C6 and posterior spinal fusion from C3 to C7 presented at 2 weeks and 5 months postoperatively with a deep neck space infection. She underwent surgical debridement each time. Workup of the second infection found a subtle cortical breach in the mandible at the site of prior invasive dental work. CONCLUSIONS: This case describes the workup and management of a patient who presented with recurrent deep neck space infection following anterior cervical spine surgery. This is the first report of a postoperative infection related to direct communication between the oropharynx and deep neck space via a cortical breach of the mandible.

High-Grade Leiomyosarcoma Arising in a Previously Replanted Limb.

Sarcoma development has been associated with genetics, irradiation, viral infections, and immunodeficiency. Reports of sarcomas arising in the setting of prior trauma, as in burn scars or fracture sites, are rare. We report a case of a leiomyosarcoma arising in an arm that had previously been replanted at the level of the elbow joint following traumatic amputation when the patient was eight years old. He presented twenty-four years later with a 10.8 cm mass in the replanted arm located on the volar forearm. The tumor was completely resected and pathology examination showed a high-grade, subfascial spindle cell sarcoma diagnosed as a grade 3 leiomyosarcoma with stage pT2bNxMx. The patient underwent treatment with brachytherapy, reconstruction with a free flap, and subsequently chemotherapy. To the best of our knowledge, this is the first case report of leiomyosarcoma developing in a replanted extremity. Development of leiomyosarcoma in this case could be related to revascularization, scar formation, or chronic injury after replantation. The patient remains healthy without signs of recurrence at three-year follow-up.

Vertical Tears of the Lateral Meniscus: Effects on In Vitro Tibiofemoral Joint Mechanics.

BACKGROUND: Lateral meniscal tears are often seen with acute anterior cruciate ligament (ACL) injury and may be left in situ, repaired, or treated with meniscectomy. Clinical studies have shown good outcomes with vertical tears left in situ and poor outcomes following meniscectomy. However, clinically relevant studies are needed to establish a biomechanical foundation for treatment of these tears, particularly regarding the effects of meniscectomy. PURPOSE: To compare tibiofemoral joint mechanics following vertical lateral meniscal tears and meniscectomies. We hypothesized that a peripheral vertical tear of the lateral meniscus would alter joint mechanics, increasing contact pressure and area, and that more drastic effects would be seen following meniscectomy, at higher knee flexion angles, and with increased loads. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen cadaveric knees (average age, 55 ± 12 years) were tested with 5 lateral meniscus states: intact, short vertical tear, extended vertical tear, posterior horn partial meniscectomy (rim intact), and posterior horn subtotal meniscectomy (rim excised). The specimens were loaded axially at knee flexion angles of 0°, 30°, and 60°, and musculotendinous forces were applied, simulating a 2-legged squat. Intra-articular contact pressures were measured using pressure-sensitive Fuji film. Kinematic data were acquired through digitization of fiducial markers. RESULTS: Vertical tears did not cause a significant change in contact pressure or area. Partial meniscectomy increased maximum contact pressures in the lateral compartment at 30° and 60° from 5.3 MPa to 7.2 MPa and 7.6 MPa, respectively (P = .02, P = .007). Subtotal meniscectomy (8.4 MPa) significantly increased contact pressure compared with partial meniscectomy (7.6 MPa) at 60° (P = .04). Both meniscectomy states significantly increased contact pressures with increasing flexion from 0° to 60° (P < .001, P < .001). CONCLUSION: Vertical tears of the lateral meniscus during a simulated 2-legged squat did not significantly change contact pressures and areas compared with an intact meniscus. However, treating these tears with partial and complete meniscectomy significantly increased maximum contact pressures. CLINICAL RELEVANCE: Biomechanical evidence supports treating vertical lateral meniscus tears with meniscal-sparing techniques as opposed to meniscectomy, which may lead to progressive degenerative joint disease from altered joint biomechanics.

Cryotherapy suppresses tendon inflammation in an animal model.

Cryotherapy (or cold treatment) has been a popular treatment to relieve pain caused by injuries to tissues such as tendons. However, the exact mechanisms behind the beneficial effects of cryotherapy in tendons remain largely unclear. As prostaglandin E2 (PGE2) is known to be a major mediator of acute inflammation in tissues, which is related to tissue pain, we hypothesized that the beneficial effects of cryotherapy in tendons are mediated by downregulation of PGE2 levels. To test this hypothesis, we applied cold treatment to mouse patellar and Achilles tendons using two animal models: exhaustive mouse treadmill running and acute mouse tendon injury by needle penetration. We then measured the levels of PGE2 and protein expression levels of COX-2, an enzyme responsible for PGE2 production in tissues, under both experimental conditions. We found that treadmill running increased PGE2 levels in both patellar and Achilles tendons compared to control mice without running. Cold treatment for 30 min after treadmill running was sufficient to reduce PGE2 levels to near baseline control levels in both tendons. An extension of cold treatment to 60 min resulted only in a marginal decrease in patellar tendons, but a marked decrease in Achilles tendons. Moreover, COX-2 protein levels in both tendons were also lowered by cold treatment, suggesting that the reduction of PGE2 levels in tendons by cold treatment is at least in part due to the decreased COX-2 expression. Similarly, in the acutely injured tendons, 30 min of cold treatment after needle penetration reduced PGE2 levels when compared to the controls at room temperature (22°C). This decrease was sustained up to at least 3 h after the administration of cryotherapy. Given that PGE2 is a known pain sensitiser, the results of this study suggest that the ability of cold treatment to reduce pain may be attributable to its ability to decrease PGE2 production in tendons.

Differential properties of human ACL and MCL stem cells may be responsible for their differential healing capacity.

BACKGROUND: The human anterior cruciate ligament (hACL) and medial collateral ligament (hMCL) of the knee joint are frequently injured, especially in athletic settings. It has been known that, while injuries to the MCL typically heal with conservative treatment, ACL injuries usually do not heal. As adult stem cells repair injured tissues through proliferation and differentiation, we hypothesized that the hACL and hMCL contain stem cells exhibiting unique properties that could be responsible for the differential healing capacity of the two ligaments. METHODS: To test the above hypothesis, we derived ligament stem cells from normal hACL and hMCL samples from the same adult donors using tissue culture techniques and characterized their properties using immunocytochemistry, RT-PCR, and flow cytometry. RESULTS: We found that both hACL stem cells (hACL-SCs) and hMCL stem cells (hMCL-SCs) formed colonies in culture and expressed stem cell markers nucleostemin and stage-specific embryonic antigen-4 (SSEA-4). Moreover, both hACL-SCs and hMCL-SCs expressed CD surface markers for mesenchymal stem cells, including CD44 and CD90, but not those markers for vascular cells, CD31, CD34, CD45, and CD146. However, hACL-SCs differed from hMCL-SCs in that the size and number of hACL-SC colonies in culture were much smaller and grew more slowly than hMCL-SC colonies. Moreover, fewer hACL-SCs in cell colonies expressed stem cell markers STRO-1 and octamer-binding transcription factor-4 (Oct-4) than hMCL-SCs. Finally, hACL-SCs had less multi-differentiation potential than hMCL-SCs, evidenced by differing extents of adipogenesis, chondrogenesis, and osteogenesis in the respective induction media. CONCLUSIONS: This study shows for the first time that hACL-SCs are intrinsically different from hMCL-SCs. We suggest that the differences in their properties contribute to the known disparity in healing capabilities between the two ligaments.

Mouse treadmill running enhances tendons by expanding the pool of tendon stem cells (TSCs) and TSC-related cellular production of collagen.

Exercise is known to enhance tendon size and strength, but the stem cell-based mechanisms for such exercise-induced effects are largely unknown. This study aims to explore these mechanisms by using a mouse treadmill running model to examine the effects of exercise on newly discovered tendon stem cells (TSCs). After treadmill running, patellar TSCs (PTSCs) and Achilles TSCs (ATSCs) were isolated from the mice, and their proliferation was measured in vitro. We found that treadmill running nearly doubled proliferation rates of both PTSCs and ATSCs compared to cage control mice. Moreover, using a mixed tendon cell culture consisting of TSCs and tenocytes, cellular production of collagen was found to increase by 70% and 200% in PTSCs and ATSCs, respectively, from the treadmill running group over cells from the cage control group. These findings suggest that exercise exerts its anabolic effects on tendons at least in part by increasing proliferation to expand the pool of TSCs and also by increasing TSC-related cellular production of collagen, the predominant component of tendons.