Full-thickness supraspinatus tears are associated with more synovial inflammation and tissue degeneration than partial-thickness tears.

BACKGROUND: The objective of this study was to determine whether the tear size of a supraspinatus tendon correlated with synovial inflammation and tendon degeneration in patients who underwent shoulder arthroscopy for rotator cuff repair. We hypothesized that increased synovial inflammation would correlate with greater tear size of the supraspinatus tendon at the time of surgery. MATERIALS AND METHODS: Tissue from the synovium, bursa, torn supraspinatus tendon, and subscapularis tendon was obtained from patients during shoulder arthroscopy to evaluate the messenger RNA expression of proinflammatory cytokines, tissue remodeling, and angiogenesis factors in the tendon, bursa, and synovium. Additional tissue was fixed to determine histologic changes including inflammation, vascular ingrowth, and collagen organization. RESULTS: Increased expression of interleukin 1ß, interleukin 6, cyclooxygenase 2, matrix metalloproteinase (MMP) 9, and vascular endothelial growth factor was found in the synovium of patients with full-thickness tears versus partial-thickness tears (P < .05). In the supraspinatus tendon, increased expression of MMP-1, MMP-9, MMP-13, and vascular endothelial growth factor was found in the full-thickness group. The upregulation of these genes in the full-thickness group was consistent with enhanced synovial inflammation, greater vascular ingrowth, and the loss of collagen organization in both supraspinatus and subscapularis tendons as determined by histology. CONCLUSION: Increased synovial inflammation and tissue degeneration correlate with the tear size of the supraspinatus tendon. A better understanding of the relationship between synovial inflammation and the progression of tendon degeneration can help in the design of novel and effective treatments to limit the advancement of rotator cuff disease and to improve their clinical outcomes.

HIF1α Regulates Early Metabolic Changes due to Activation of Innate Immunity in Nuclear Reprogramming.

Innate immune signaling has recently been shown to play an important role in nuclear reprogramming, by altering the epigenetic landscape and thereby facilitating transcription. However, the mechanisms that link innate immune activation and metabolic regulation in pluripotent stem cells remain poorly defined, particularly with regard to key molecular components. In this study, we show that hypoxia-inducible factor 1α (HIF1α), a central regulator of adaptation to limiting oxygen tension, is an unexpected but crucial regulator of innate immune-mediated nuclear reprogramming. HIF1α is dramatically upregulated as a consequence of Toll-like receptor 3 (TLR3) signaling and is necessary for efficient induction of pluripotency and transdifferentiation. Bioenergetics studies reveal that HIF1α regulates the reconfiguration of innate immune-mediated reprogramming through its well-established role in throwing a glycolytic switch. We believe that results from these studies can help us better understand the influence of immune signaling in tissue regeneration and lead to new therapeutic strategies.

Posttraumatic Chondrocyte Apoptosis in the Murine Xiphoid.

OBJECTIVE: To demonstrate posttraumatic chondrocyte apoptosis in the murine xiphoid after a crush-type injury and to ultimately determine the pathway (i.e., intrinsic or extrinsic) by which chondrocytes undergo apoptosis in response to mechanical injury. DESIGN: The xiphoids of adult female wild-type mice were injured with the use of a modified Kelly clamp. Postinjury xiphoid cartilage was analyzed via 3 well-described independent means of assessing apoptosis in chondrocytes: hematoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and activated caspase-3 staining. RESULTS: Injured specimens contained many chondrocytes with evidence of apoptosis, which is characterized by cell shrinkage, chromatin condensation, nuclear fragmentation, and the liberation of apoptotic bodies. There was a statistically significant increase in the number of chondrocytes undergoing apoptosis in the injured specimens as compared with the uninjured specimens. CONCLUSIONS: Chondrocytes can be stimulated to undergo apoptosis as a result of mechanical injury. These experiments involving predominantly cartilaginous murine xiphoid in vivo establish a baseline for future investigations that employ the genetic and therapeutic modulation of chondrocyte apoptosis in response to mechanical injury.

Chondrocyte death and cartilage degradation after autologous osteochondral transplantation surgery in a rabbit model.

BACKGROUND: Autologous osteochondral transplantation surgery requires an impact force on the graft that may cause chondrocyte death and matrix degradation. This study attempted to determine the degree to which this occurs in a rabbit model shortly after the procedure. HYPOTHESIS: Impaction of a press-fit autologous osteochondral graft in vivo results in chondrocyte necrosis, apoptosis, and matrix degradation at early time points. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty New Zealand White rabbits underwent unilateral osteochondral transplantation (OT) surgeries, and 10, bilateral sham surgeries. Fifteen animals were sacrificed at time zero (10 sham-0 limbs, 10 OT-0 limbs), and 15, 4 days after surgery (10 sham-4 limbs, 10 OT-4 limbs). Chondrocyte viability/necrosis was determined with cell vital staining. Chondrocyte apoptosis was determined by TUNEL, Bcl-2, and M30 assays. Cartilage matrix degradation was determined by routine light and polarized light microscopy and COL2-3/4C(short) immunohistochemistry. Statistical analysis was performed with a 2-way analysis of variance (P < .05). RESULTS: There were significantly fewer viable cells in OT-4 than in sham-4. A similar difference in cell viability was found in OT-0 versus sham-0. There were more TUNEL-positive cells in OT-4 as compared with OT-0, sham-0, and sham-4; however, there was little or no staining of Bcl-2 and M30. Mankin scores were higher in both OT groups versus both sham groups at time zero and day 4. The OT-4 group had positive staining for COL2-3/4C(short) that corresponded with a loss of collagen birefringence at the superficial zone. CONCLUSION: Osteochondral transplantation procedures performed by tamping a press-fit graft induce chondrocyte necrosis and matrix metalloproteinase-mediated cartilage matrix degradation. However, apoptosis was not found to a major contributor to cell death in this model. CLINICAL RELEVANCE: Results of osteochondral transplantation procedures may be improved by atraumatic insertion and fixation techniques or by pharmacologic agents that can block these degradative processes.

The maturation of mucus-secreting gastric epithelial progenitors into digestive-enzyme secreting zymogenic cells requires Mist1.

Continuous regeneration of digestive enzyme (zymogen)-secreting chief cells is a normal aspect of stomach function that is disrupted in precancerous lesions (e.g. metaplasias, chronic atrophy). The cellular and genetic pathways that underlie zymogenic cell (ZC) differentiation are poorly understood. Here, we describe a gene expression analysis of laser capture microdissection purified gastric cell populations that identified the bHLH transcription factor Mist1 as a potential ZC regulatory factor. Our molecular and ultrastructural analysis of proliferation, migration and differentiation of the gastric unit in Mist1(-/-) and control mice supports a model whereby wild-type ZC progenitors arise as neck cells in the proliferative (isthmal) zone of the gastric unit and become transitional cells (TCs) with molecular and ultrastructural characteristics of both enzyme-secreting ZCs and mucus-secreting neck cells as they migrate to the neck-base zone interface. Thereafter, they rapidly differentiate into mature ZCs as they enter the base. By contrast, Mist1(-/-) neck cells differentiate normally, but ZCs in the mature, basal portion of the gastric unit uniformly exhibit multiple apical cytoplasmic structural abnormalities. This defect in terminal ZC differentiation is also associated with markedly increased abundance of TCs, especially in late-stage TCs that predominantly have features of immature ZCs. Thus, we present an in vivo system for analysis of ZC differentiation, present molecular evidence that ZCs differentiate from neck cell progenitors and identify Mist1 as the first gene with a role in this clinically important process.

Molecular characterization of mouse gastric zymogenic cells.

Zymogenic cells (ZCs), acid-producing parietal cells (PCs), and mucus-secreting pit cells are the principal epithelial lineages in the stomachs of adult mice and humans. Each lineage is derived from the multipotent gastric stem cell and undergoes perpetual renewal within discrete mucosal invaginations (gastric units). In this report, we analyze the molecular features of ZCs and their contributions to gastric epithelial homeostasis. GeneChip analysis yielded a dataset of 57 mRNAs encoding known proteins and 14 ESTs enriched in adult mouse ZCs. This dataset, obtained from comparisons of cellular populations purified by counterflow elutriation and lectin panning, was validated by real-time quantitative reverse transcription-PCR studies of the in vivo expression of selected genes using cells harvested from different regions of gastric units by laser capture microdissection. ZC-enriched mRNAs include regulators of angiogenesis (e.g. platelet-derived growth factors A and B). Because PCs are enriched in transcripts encoding other angiogenic factors (e.g. Vegfb), the contributions of these two lineages to vascular development was examined by performing quantitative three-dimensional imaging of the capillary networks that surround gastric units in two types of mice. In normal adult gnotobiotic FVB/N animals, network density is on average 2-fold higher in ZC- and PC-containing units located in the proximal (corpus) region of the stomach compared with units positioned in the distal (antral) region that lack these lineages (p < 0.01). Gnotobiotic transgenic mice with an engineered ablation of all ZCs and PCs have a 2-fold reduction in capillary network density in their corpus region gastric units compared with the corpus units of normal littermates (p < 0.01). These results support an emerging theme that angiogenesis in the adult mouse gut is modulated by cross-talk between its epithelial lineages and the underlying mesenchyme.