Stimulation of skeletal stem cells in the growth plate promotes linear bone growth.

Recently, skeletal stem cells were shown to be present in the epiphyseal growth plate (epiphyseal skeletal stem cells, epSSCs), but their function in connection with linear bone growth remains unknown. Here, we explore the possibility that modulating the number of epSSCs can correct differences in leg length. First, we examined regulation of the number and activity of epSSCs by Hedgehog (Hh) signaling. Both systemic activation of Hh pathway with Smoothened agonist (SAG) and genetic activation of Hh pathway by Patched1 (Ptch1) ablation in Pthrp-creER Ptch1fl/fl tdTomato mice promoted proliferation of epSSCs and clonal enlargement. Transient intra-articular administration of SAG also elevated the number of epSSCs. When SAG-containing beads were implanted into the femoral secondary ossification center of 1 leg of rats, this leg was significantly longer 1 month later than the contralateral leg implanted with vehicle-containing beads, an effect that was even more pronounced 2 and 6 months after implantation. We conclude that Hh signaling activates growth plate epSSCs, which effectively leads to increased longitudinal growth of bones. This opens therapeutic possibilities for the treatment of differences in leg length.

Clonal Genetic Tracing using the Confetti Mouse to Study Mineralized Tissues.

Labeling an individual cell in the body to monitor which cell types it can give rise to and track its migration through the organism or determine its longevity can be a powerful way to reveal mechanisms of tissue development and maintenance. One of the most important tools currently available to monitor cells in vivo is the Confetti mouse model. The Confetti model can be used to genetically label individual cells in living mice with various fluorescent proteins in a cell type-specific manner and monitor their fate, as well as the fate of their progeny over time, in a process called clonal genetic tracing or clonal lineage tracing. This model was generated almost a decade ago and has contributed to an improved understanding of many biological processes, particularly related to stem cell biology, development, and renewal of adult tissues. However, preserving the fluorescent signal until image collection and simultaneous capturing of various fluorescent signals is technically challenging, particularly for mineralized tissue. This publication describes a step-by-step protocol for using the Confetti model to analyze growth plate cartilage that can be applied to any mineralized or nonmineralized tissue.

Schwann cell precursors contribute to skeletal formation during embryonic development in mice and zebrafish.

Immature multipotent embryonic peripheral glial cells, the Schwann cell precursors (SCPs), differentiate into melanocytes, parasympathetic neurons, chromaffin cells, and dental mesenchymal populations. Here, genetic lineage tracing revealed that, during murine embryonic development, some SCPs detach from nerve fibers to become mesenchymal cells, which differentiate further into chondrocytes and mature osteocytes. This occurred only during embryonic development, producing numerous craniofacial and trunk skeletal elements, without contributing to development of the appendicular skeleton. Formation of chondrocytes from SCPs also occurred in zebrafish, indicating evolutionary conservation. Our findings reveal multipotency of SCPs, providing a developmental link between the nervous system and skeleton.

A radical switch in clonality reveals a stem cell niche in the epiphyseal growth plate.

Longitudinal bone growth in children is sustained by growth plates, narrow discs of cartilage that provide a continuous supply of chondrocytes for endochondral ossification1. However, it remains unknown how this supply is maintained throughout childhood growth. Chondroprogenitors in the resting zone are thought to be gradually consumed as they supply cells for longitudinal growth1,2, but this model has never been proved. Here, using clonal genetic tracing with multicolour reporters and functional perturbations, we demonstrate that longitudinal growth during the fetal and neonatal periods involves depletion of chondroprogenitors, whereas later in life, coinciding with the formation of the secondary ossification centre, chondroprogenitors acquire the capacity for self-renewal, resulting in the formation of large, stable monoclonal columns of chondrocytes. Simultaneously, chondroprogenitors begin to express stem cell markers and undergo symmetric cell division. Regulation of the pool of self-renewing progenitors involves the hedgehog and mammalian target of rapamycin complex 1 (mTORC1) signalling pathways. Our findings indicate that a stem cell niche develops postnatally in the epiphyseal growth plate, which provides a continuous supply of chondrocytes over a prolonged period.

Tumor necrosis factor α modulates sodium-activated potassium channel SLICK in rat dorsal horn neurons via p38 MAPK activation pathway.

The dorsal horn (DH) of the spinal cord is the integrative center that processes and transmits pain sensation. Abnormal changes in ion channel expression can enhance the excitability of pain-related DH neurons. Sodium-activated potassium (KNa) channels are highly expressed particularly in the central nervous system; however, information about whether rat DH neurons express the SLICK channel protein is lacking, and the direct effects on SLICK in response to inflammation and the potential signaling pathway mediating such effects are yet to be elucidated. Here, using cultured DH neurons, we have shown that tumor necrosis factor-α inhibits the total outward potassium current IK and the KNa current predominantly as well as induces a progressive loss of firing accommodation. However, we found that this change in channel activity is offset by the p38 inhibitor SB202190, thereby suggesting the modulation of SLICK channel activity via the p38 MAPK pathway. Furthermore, we have demonstrated that the tumor necrosis factor-α modulation of KNa channels does not occur at the level of SLICK channel gating but arises from possible posttranslational modification.

Evaluation of transforaminal endoscopic lumbar discectomy in the treatment of lumbar disc herniation.

PURPOSE: The purpose of this study was to evaluate the efficacy of transforaminal endoscopic lumbar discectomy (TELD) in the treatment of lumbar disc herniation (LDH) and to identify the relationship between TELD efficacy and age. METHODS: A total of 207 consecutive LDH patients who had undergone TELD with the THESSYS system from January 2013 to September 2014 were divided into two groups on the basis of their age, with 108 cases in the ≤ 45-year-old age group and 99 cases in the >45-year-old group. The Oswestry Disability Index (ODI) was used to quantify the pain relief. The degree of pain and disability were measured on the basis of the visual analog scale (VAS) and the modified MacNab criteria. Complications, duration of hospital stay, surgical costs, and operation time were recorded and compared between the two groups. Spearman's coefficient of rank correlation was used to assess the learning curves for TELD. RESULTS: The mean pre-operative and postoperative VAS and ODI scores significantly improved in both age ≤ 45 group and age >45 group, with no significant differences between them. In age ≤45 group, 56 % had excellent outcomes, 28 % good, 14 % fair, and 3 % poor. In the age >45 group, 51 % had excellent outcomes, 20 % good, 25 % fair, and 4 % poor. The average lengths of hospital stay for the age ≤ 45 group and age >45 group were 6.8 and 8.4 days, respectively. The mean time to return to work or normal activities was ten days for the age ≤ 45 group and 15 days for the age >45 group. The mean operative time for the age ≤ 45 group was 94 minutes and that for age >45 group was 97 minutes. The surgical cost of age ≤ 45 group was 15,480 RMB, which was lower than the 16,381 RMB of age >45 group. A total of 14 patients in the age ≤ 45 group and 13 patients in age >45 group used analgesic medications. Three and five recurrences were reported in the age ≤ 45 group and age >45, respectively. The steep learning curves of operative time plotted against the number of surgeries conducted suggest that the TELD technique can be mastered quickly in terms of reducing the duration of operation. CONCLUSIONS: The efficacy of TELD is relatively good for the selected young and elderly patients in this study. Therefore, age is not a predictor of TELD surgery-related outcomes.

In vivo and in vitro expression of the RASAL1 gene in human gastric adenocarcinoma and its clinicopathological significance.

Recent studies have suggested that the RAS protein activator like-1 (RASAL1) is a potential tumor suppressor, which is found to be reduced in certain human cancers. Its downregulation is involved in the progression of malignancies. However, whether or not RASAL1 plays a role in the development of gastric cancer remains to be determined. Our study aimed to clarify the role of RASAL1 in the progression of gastric adenocarcinoma. The expression of RASAL1 in primary gastric adenocarcinoma tissue specimens was determined by immunohistochemistry. The expression of RASAL1 mRNA and protein was detected by RT-PCR and western blotting in gastric adenocarcinoma cell lines with varying differentiation statuses, including well-differentiated MKN-28, moderately differentiated SGC-7901 and poorly differentiated BGC-823, respectively. A normal gastric epithelial cell line, GES-l, was used as the control line. The immunohistochemical results revealed that the expression of the RASAL1 protein was mainly observed in the cytoplasm. Among 50 cases of gastric adenocarcinoma tissues, 12 cases were identified as (-), 23 cases (+), 13 cases (++) and 2 cases (+++). Among 50 cases of normal gastric tissues, 16 cases were (++) and 34 cases (+++). The expression of the RASAL1 protein was found to be decreased in the gastric adenocarcinoma tissue compared with normal gastric tissue (p<0.01). Moreover, in the gastric carcinoma tissues, the expression of RASAL1 was correlated with carcinoma diameter, differentiation grades, invasive depth, lymph node metastasis and TNM. Additionally, the RASAL1 mRNA and proteins were decreased in the three gastric adenocarcinoma cell lines compared with the normal gastric epithelial cell line GES-l. In addition, the downregulation of RASAL1 correlated with the differentiation status of cancer cell lines. Based on the above investigation, we conclude that expression of the RASAL1 gene is decreased in gastric carcinoma tissues and cell lines. The results indicate that RASAL1 may be important in the tumorigenesis and development of gastric carcinoma.