Retraction Note to: Explore on the effect of ATF6 on cell growth and apoptosis in cartilage development.

The Editor-in-Chief has retracted the article by Han et al. (2014) because Fig. 3a-d are also published as Fig. 5b-e in Liu et al. (2012), and Fig. 3a, c, d are also published as Fig. 5a, d, e in Guo et al. (2014).

XBP1S, a BMP2-inducible transcription factor, accelerates endochondral bone growth by activating GEP growth factor.

We previously reported that transcription factor XBP1S binds to RUNX2 and enhances chondrocyte hypertrophy through acting as a cofactor of RUNX2. Herein, we report that XBP1S is a key downstream molecule of BMP2 and is required for BMP2-mediated chondrocyte differentiation. XBP1S is up-regulated during chondrocyte differentiation and demonstrates the temporal and spatial expression pattern during skeletal development. XBP1S stimulates chondrocyte differentiation from mesenchymal stem cells in vitro and endochondral ossification ex vivo. In addition, XBP1S activates granulin-epithelin precursor (GEP), a growth factor known to stimulate chondrogenesis, and endogenous GEP is required, at least in part, for XBP1S-stimulated chondrocyte hypertrophy, mineralization and endochondral bone formation. Furthermore, XBP1S enhances GEP-stimulated chondrogenesis and endochondral bone formation. Collectively, these findings demonstrate that XBP1S, a BMP2-inducible transcription factor, positively regulates endochondral bone formation by activating GEP chondrogenic growth factor.

Explore on the effect of ATF6 on cell growth and apoptosis in cartilage development.

We previously report that BMP2 mediates mild ER stress-activated ATF6 and directly regulates XBP1S splicing in the course of chondrogenesis. The mammalian unfolded protein response (UPR) protects the cell against the stress of misfolded proteins in the endoplasmic reticulum (ER). Failure to adapt to ER stress causes the UPR to trigger apoptosis. The transcription factor activating transcription factor 6 (ATF6), a key regulator of the UPR, is known to be important for ER stress-mediated apoptosis and cell growth, but the molecular mechanism underlying these processes remains unexplored. In this study, we demonstrate that ATF6 is differentially expressed during BMP2-stimulated chondrocyte differentiation and exhibits prominent expression in growth plate chondrocytes. ATF6 can enhance the level of IRE1a-spliced XBP1S protein in chondrogenesis. IRE1a and ATF6 can synergistically regulate endogenous XBP1S gene expression in chondrogenesis. Furthermore, overexpression ATF6 inhibited, while ATF6-knockdown enhanced, the cell proliferation in chondrocyte development with G1 phase arresting, S phase reducing and G2-M phase delaying. Besides, Ad-ATF6 can activate, whereas knockdown ATF6 by an siRNA-silencing approach inhibited, ER stress-mediated apoptosis in chondrogenesis induced by BMP2, as assayed by cleaved caspase3, CHOP, p-JNK expression in the course of chondrocyte differentiation. On the other hand, FCM, TUNEL assay and immunohistochemistry analysis also proved this result in vitro and in vivo. It was demonstrated that Ad-ATF6 activation of the ER stress-specific caspase cascade in developing chondrocyte tissue. Collectively, these findings reveal a novel critical role of ATF6 in regulating ER stress-mediated apoptosis in chondrocyte differentiation and the molecular mechanisms involved.

XBP1S associates with RUNX2 and regulates chondrocyte hypertrophy.

BMP2 (bone morphogenetic protein 2) is known to activate unfolded protein response signaling molecules, including XBP1S and ATF6. However, the influence on XBP1S and ATF6 in BMP2-induced chondrocyte differentiation has not yet been elucidated. In this study, we demonstrate that BMP2 mediates mild endoplasmic reticulum stress-activated ATF6 and directly regulates XBP1S splicing in the course of chondrogenesis. XBP1S is differentially expressed during BMP2-stimulated chondrocyte differentiation and exhibits prominent expression in growth plate chondrocytes. This expression is probably due to the activation of the XBP1 gene by ATF6 and splicing by IRE1a. ATF6 directly binds to the 5'-flanking regulatory region of the XBP1 gene at its consensus binding elements. Overexpression of XBP1S accelerates chondrocyte hypertrophy, as revealed by enhanced expression of type II collagen, type X collagen, and RUNX2; however, knockdown of XBP1S via the RNAi approach abolishes hypertrophic chondrocyte differentiation. In addition, XBP1S associates with RUNX2 and enhances RUNX2-induced chondrocyte hypertrophy. Altered expression of XBP1S in chondrocyte hypertrophy was accompanied by altered levels of IHH (Indian hedgehog) and PTHrP (parathyroid hormone-related peptide). Collectively, XBP1S may be a novel regulator of hypertrophic chondrocyte differentiation by 1) acting as a cofactor of RUNX2 and 2) affecting IHH/PTHrP signaling.

Treatment of scaphoid nonunion: pedicled vascularized bone graft vs. traditional bone graft.

The clinical results of the application of pedicled vascularized bone graft (VBG) from Lister's tubercle vs. traditional bone graft (TBG) were evaluated and compared. Thirteen cases of symptomatic scaphoid nonunion were treated between January 2011 and December 2012, including 7 cases subject to VBG and the rest 6 cases to TBG, respectively. Outcomes were assessed by modified Mayo wrist score system. All cases were followed up for an average period of 3.5 months after operation. The results showed that total scores in VBG group were 86.4±9.4 after operation with excellent result in 4 cases, good in 2 and acceptable in one, and those in TBG group were 71.7±9.3 after operation with good result in 2 cases, acceptable in 3 and disappointing in one. Total score of wrist function was significantly improved in VBG group as compared with TBG group (P<0.05). Our study suggests that VBG method is more effective for treating scaphoid nonunion than TBG method.

Total spondylectomy of C2 and circumferential reconstruction via combined anterior and posterior approach to cervical spine for axis tumor surgery.

As a result of the complex anatomy in upper cervical spine, the operative treatment of axis neoplasms is always complicated. Although the procedure for the second cervical vertebra (C2) surgery had been described previously in diverse approaches and reconstruction forms, each has its own limitations and restrictions that usually result in less satisfactory conclusions. The purpose of this study was to evaluate the operation efficacy for axis tumors by using a combined anterior (retropharyngeal) cervical and posterior approach in achieving total resection of C2 and circumferential reconstruction. Eight consecutive C2 tumor patients with mean age of 47.6 years in our institute sequentially underwent vertebra resection and fixation through aforementioned approach from Jan. 2006 to Dec. 2010. No surgical mortality or severe morbidity occurred in our group. In terms of complications, 2 cases developed transient difficulty in swallowing liquids (one of them experienced dysphonia) and 1 developed cerebrospinal fluid leakage (CSFL) that was resolved later. During a mean follow-up period of 31.9 months, the visual analogue scale (VAS) and Japanese orthopedic association (JOA) score revealed that the pain level and neurological function in all patients were improved postoperatively, and there was no evidence of fixation failure and local recurrence. It is concluded that the anterior cervical retropharyngeal approach permits a visible exposure to facilitate the C2 vertebra resection and perform an effective anterior reconstruction at the same time. The custom-made mesh cage applied in our cases can be acted as a firm and convenient implant in circumferential fixation.

[The effect on BiP regulation of IRE1a promoter transcription activity and protein expression].

Usually, secreted or transmembrane proteins complete their three-dimension folding within endoplasmic reticulum (ER). Under the conditions of nutrient depletion, cell differentiation, or other stress statuses, misfolded or unfolded proteins aggregate within ER, and consequently cause ER stress and Unfolded Protein Response (UPR). In response to ER stress, BiP (Binding immunoglobulin protein) dissociates with IRE1a (Inositol-requiring kinase 1) and binds to unfolded proteins as a molecular chaperone in helping maintain their correct structure. Co-related to BiP's dissociation, IRE1a oglimerizes and activated its endoribonuclease domain by transautophosphorylation. Activated IRE1a then, by cleaving mRNA of Xbp1 and activating its transcription activity, triggers UPR. In this paper, in order to determine effect of BiP on transcription activity of IRE1a, we cloned promoter region of IRE1a into reporter gene analysis vector and found that BiP could upregulate promoter activity of IRE1a. Then, we constructed another 6 truncated promoter reporter vectors of IRE1a and pinpoint the core promoter activity region. Furthermore, both our RT-PCR and Western blot results showed that BiP could upregulate mRNA transcription level and protein expression level of IRE1a. Base on these findings, we can propose that, in order to alleviate ER stress caused by the misfolded or malfolded proteins, BiP could upregulate expression of IRE1a by increase its promoter activity. This study may suggest a novel signal pathway on IRE1a regulation in ER stress.

XBP1S protects cells from ER stress-induced apoptosis through Erk1/2 signaling pathway involving CHOP.

The mammalian unfolded protein response (UPR) protects the cell against the stress of misfolded proteins in the endoplasmic reticulum (ER), and the transcription factor X-box binding protein 1 spliced (XBP1S), a regulator of the UPR, is known to be important for ER stress (ERS)-mediated apoptosis and cell growth, but the molecular mechanism underlying these processes remains unexplored. Here, we report that knockdown of XBP1S by an siRNA silencing approach increased the expression of ERS-associated molecules. The overexpression of XBP1S stimulated, whereas its knockdown inhibited, cell proliferation in chondrocytes and chondrosarcoma cells; in addition, overexpression of XBP1S inhibited, while its repression enhanced, ERS-mediated apoptosis in chondrocytes and chondrosarcoma cells. Furthermore, XBP1S-mediated inhibition of apoptosis in response to ERS is through the Erk1/2 signaling pathway and down-regulation CHOP transcription factor. CHOP is one of the key downstream molecules known to be involved in ERS-mediated apoptosis. Collectively, these findings reveal a novel critical role of XBP1S in ERS-mediated apoptosis and the molecular mechanisms involved.

ATF4 and IRE1α inhibit DNA repair protein DNA-dependent protein kinase 1 induced by heat shock.

With the increase of environment temperature, more and more attentions are payed to the effects of heat stress. Cells under heat shock either are adapted to the condition or are damaged and dead. In this paper, we found that heat shock induced endoplasmic reticulum (ER) stress. ATF4, PERK, and IRE1α were induced by heat shock of 45 °C in the transcriptional level. Under the stress of 45 °C, PERK was phosphorylated and XBP1s was detected. The result indicated that heat shock could induce the ER stress. We found that heat shock of 45 °C induced the dysregulation of HSP70 and DNA-PKcs, and downregulated the expression of PARP1 and XRCC1. Further results showed that after the knockdown of ATF4 or IRE1α, the expression of DNA-PKcs and XRCC1 were increased. It was indicated that ATF4 and IRE1α could inhibit the expression of DNA-PKcs and XRCC1 under the heat stress. Our results suggested that heat shock could activate ER stress. IRE1α and ATF4, as the important ER stress molecules, could inhibit the expression of DNA repair proteins DNA-PKcs, XRCC1, and HSP70 under heat shock. Downregulation of DNA repair proteins could aggravate the cell damage that may cause cell apoptosis. This may explain that heat shock could increase the lethality of chemotherapeutic drugs on tumor cells.

Study on the effect of IRE1a on cell growth and apoptosis via modulation PLK1 in ER stress response.

The mammalian unfolded protein response (UPR) protects the cell against the stress of misfolded proteins in the endoplasmic reticulum (ER). Failure to adapt to ER stress causes the UPR to trigger apoptosis. Inositol-requiring enzyme-1a (IRE1a), as one of three unfolded protein sensors in UPR signaling pathways, senses ER unfolded proteins through an ER lumenal domain that becomes oligomerized during ER stress. It is known to be important for ER stress-mediated apoptosis and cell growth, but the exact molecular mechanism underlying these processes remains unexplored. In this study, we report that knockdown of IRE1a by an siRNA silencing approach enhanced, whereas its overexpression inhibited, cell proliferation in Hepatoma cells. Besides, overexpression of IRE1a induced, while its repression inhibited, ER stress-mediated apoptosis in Hepatomas cells. Furthermore, we found that overexpressed IRE1a can down-regulate Polo-like kinase 1(PLK1) from mRNA and protein two levels. IRE1a-mediated induction of apoptosis and inhibition of proliferation in response to ER stress is through downregulation PLK1, an early trigger for G2/M transition known to be participated in regulating cell proliferation and cell apoptosis. Collectively, these findings reveal a novel critical role of IRE1a in ER stress-mediated apoptosis and the molecular mechanisms involved. IRE1a may be a useful molecular target for the development of novel predictive and therapeutic strategies in cancer.

Granulin epithelin precursor: a bone morphogenic protein 2-inducible growth factor that activates Erk1/2 signaling and JunB transcription factor in chondrogenesis.

Granulin epithelin precursor (GEP) has been implicated in development, tissue regeneration, tumorigenesis, and inflammation. Herein we report that GEP stimulates chondrocyte differentiation from mesenchymal stem cells in vitro and endochondral ossification ex vivo, and GEP-knockdown mice display skeleton defects. Similar to bone morphogenic protein (BMP) 2, application of the recombinant GEP accelerates rabbit cartilage repair in vivo. GEP is a key downstream molecule of BMP2, and it is required for BMP2-mediated chondrocyte differentiation. We also show that GEP activates chondrocyte differentiation through Erk1/2 signaling and that JunB transcription factor is one of key downstream molecules of GEP in chondrocyte differentiation. Collectively, these findings reveal a novel critical role of GEP growth factor in chondrocyte differentiation and the molecular events both in vivo and in vitro.

[One-stage total en bloc spondylectomy by anterior and posterior approaches for lumbar vertebral tumors].

OBJECTIVE: To investigate the surgical results of one stage total en bloc spondylectomy (TES) by anterior and posterior approaches for lumbar vertebral tumors and evaluate its benefit for these tumors. METHODS: A total of 21 patients with the lumbar vertebral tumor treated with on stage TES by posterior and anterior approaches from April 2003 to August 2007 were reviewed, which included 14 males and 7 females with an average age of 47.6 years. Thirteen patients were suffered with the primary lumbar vertebral tumors and 8 patients were diagnosed for the lumbar vertebral metastasis tumors. There were 8 of S3, 3 of I A and 2 of II according to Ennekinng stage system. And there were 1 of Grade B, 4 of Grade C, 8 of Grade D, and 6 of Grade E according to Frankel grade system. The spinal reconstruction was obtained by titanium mesh filled with autograft for benign and low-grade malignant tumors and methylmethacrylate-filled titanium mesh for malignant tumors. The spinal stability was enhanced by posterior internal fixation with rod-screw system. RESULTS: The operation time was 250 min and bleed loss was 2100 ml on average. The follow-up period lasted from 1.0 to 5.5 years. All cases had pain before operation, among which 14 cases obtained complete relief and 7 cases obtained partly relief after operation. In all cases with neurological deficit, they improved neurologically by more than one grade using the Frankel grading system. Up to now, 1 patient had be local recurrence after operation and 4 patients were dead on the following time. The others still are alive and no local recurrence. CONCLUSION: One-stage TES by anterior and posterior approaches for lumbar vertebral tumor is feasible, safe and effective to lumbar vertebral tumor resection and stability reconstruction, which has many advantages such as controlling local recurrence, spinal cord decompression thoroughly, relieving the pain, improving the life quality and prolonging the lifetime.

Knockdown of STIP1 inhibits the invasion of CD133­positive cancer stem­like cells of the osteosarcoma MG63 cell line via the PI3K/Akt and ERK1/2 pathways.

Osteosarcoma is the most common primary malignant tumor of the bone in adolescents and children, with high rates of metastasis and a poor prognosis. Recently, osteosarcoma cancer stem/stem­like cells (CSCs) have been identified as the main cause of recurrence and metastasis. Stress­induced phosphoprotein 1 (STIP1), a co­chaperone that binds to heat shock proteins 70 and 90, is abnormally expressed in several tumor cell lines, and may play an important role in tumor cell migration and invasion. These features indicate that STIP1 may represent a new therapeutic target for osteosarcoma CSCs. However, the role of STIP1 in osteosarcoma CSC migration and invasion remains largely unknown. In the present study, CD133­positive osteosarcoma CSCs were first isolated and cultured by magnetic cell sorting and serum­free medium suspension cell sphere culture, respectively. Knockdown of STIP1 by small interfering RNA significantly was then shown to inhibit the migration and invasion of these cells, possibly due to the regulation of the expression of matrix metalloproteinase (MMP)­2, MMP­9 and tissue inhibitor of metalloproteinase­2. Furthermore, data from the present study suggested that the knockdown of STIP1 decreased the levels of phosphorylated Akt and phosphorylated ERK1/2. In summary, these findings indicate that targeting STIP1 in osteosarcoma may constitute a viable molecular targeted therapy strategy for the inhibition of CSC invasion and migration.

[Differential proteomic analysis and function study of human prostate carcinoma cells with different osseous metastatic tendency].

OBJECTIVE: To investigate the differential protein expression profiles of human prostatic carcinoma cells with different metastatic tendency and to screen the osseous metastasis associated proteins and investigate their function. METHODS: Proteomics and Western blotting were applied to screen and identify the differentially expressed proteins in the prostatic carcinoma cells of different lines: line T3B with high osseous metastasis potential, line P2-4 with high lymphatic metastasis potential, and their common parent cell line PC-3. The eukaryotic expression vector carrying human Pgenesil-1/HMGB1 siRNA was constructed and transfected into T3B cells by Lipofectamine 2000 and the positive clones was screened by G418. Pgenesil-1/HMGB1 siRNA/T3B, Pgenesil-1/T3B, and T3B cells were inoculated into the left ventricles of nude mice. Twelve weeks later the mice were killed. The number of osseous metastatic nodules and osseous metastasis inhibition rate were calculated. The mice metastatic tumor cells were identified by immunohistochemistry. RESULT: Six differential expressed proteins, correlated with cytoskeleton, transcriptional control, cellular metabolism, and phosphorylation were identified by proteomics and Western blotting. The recombinant plasmid Pgenesil-1/HMGB1 siRNA was successfully constructed. The HMGB1 expression of the T3B cells transfected with Pgenesil-1/HMGB1 siRNA was significantly lower than those of the other 2 groups (both P <0.05). The number of osseous metastatic nodules of the mice inoculated with Pgenesil-1/HMGB1 siRNA/T3B was significantly less than those of the other 2 groups (both P < 0.05). The metastatic osseous tumor cells were identified as the human prostatic carcinoma cells. CONCLUSION: Osseous metastasis associated proteins exist in prostatic carcinoma cells of the line with high osseous metastasis potential. HMGB1 is closely related to the osseous metastasis of human prostatic carcinoma cells. siRNA targeting HMGB1 specifically suppresses the expression of HMGB1 gene in the human prostatic carcinoma cells with high osseous metastasis potential and effectively inhibits the osseous metastasis.

Ulinastatin Inhibits Osteoclastogenesis and Suppresses Ovariectomy-Induced Bone Loss by Downregulating uPAR.

Recent studies indicate that uPAR acts a crucial part in cell migration and the modulation of bone homeostasis. As a natural serine protease inhibitor, ulinastatin owns the capacity to reduce proinflammatory factors, downregulate the activation of NF-κB and mitogen-activated protein kinases (MAPKs) signaling pathways. Osteoclastogenesis has been demonstrated to be related with low-grade inflammation which involves cell migration, thus we speculate that ulinastatin may have a certain kind of impact on uPAR so as to be a potential inhibiting agent of osteoclastogenesis. In this research, we investigated the role which ulinastatin plays in RANKL-induced osteoclastogenesis both in vivo and in vitro. Ulinastatin inhibited osteoclast formation and bone resorption in a dose-dependent manner in primary bone marrow-derived macrophages (BMMs), and knockdown of uPAR could completely repress the formation of osteoclasts. At the molecular level, ulinastatin suppressed RANKL-induced activation of cathepsin K, TRAP, nuclear factor-κB (NF-κB) and MAPKs, and decreased the expression of uPAR. At the meantime, ulinastatin also decreased the expression of osteoclast marker genes, including cathepsin K, TRAP, RANK, and NFATc1. Besides, ulinastatin prevented bone loss in ovariectomized C57 mice by inhibiting the formation of osteoclasts. To sum up, this research confirmed that ulinastatin has the ability to inhibit osteoclastogenesis and prevent bone loss, and uPAR plays a crucial role in that process. Therefore, ulinastatin could be chosen as an effective alternative therapeutics for osteoclast-related diseases.

Corrigendum: Ulinastatin Inhibits Osteoclastogenesis and Suppresses Ovariectomy-Induced Bone Loss by Downregulating uPAR.

[This corrects the article DOI: 10.3389/fphar.2018.01016.].

Icariin Regulates the Bidirectional Differentiation of Bone Marrow Mesenchymal Stem Cells through Canonical Wnt Signaling Pathway.

Fat infiltration within the bone marrow is easily observed in some postmenopausal women. Those fats are mainly derived from bone marrow mesenchymal stem cells (BMMSCs). The increment of adipocytes derived from BMMSCs leads to decreased osteoblasts derived from BMMSCs, so the bidirectional differentiation of BMMSCs significantly contributes to osteoporosis. Icariin is the main extractive of Herba Epimedii which is widely used in traditional Chinese medicine. In this experiment, we investigated the effect of icariin on the bidirectional differentiation of BMMSCs through quantitative real-time PCR, immunofluorescence, western blot, and tissue sections in vitro and in vivo. We found that icariin obviously promotes osteogenesis and inhibits adipogenesis through detecting staining and gene expression. Micro-CT analysis showed that icariin treatment alleviated the loss of cancellous bone of the distal femur in ovariectomized (OVX) mice. H&E staining analysis showed that icariin-treated OVX mice obtained higher bone mass and fewer bone marrow lipid droplets than OVX mice. Western blot and immunofluorescence showed that icariin regulates the bidirectional differentiation of BMMSCs via canonical Wnt signaling. This study demonstrates that icariin exerts its antiosteoporotic effect by regulating the bidirectional differentiation of BMMSCs through the canonical Wnt signaling pathway.

An analysis on transcriptional regulation activity of human XBP1 gene 5' upstream DNA sequences.

OBJECTIVE: To analyze the transcription activation and possible regulation mechanism of human X-box binding protein 1(XBP1)gene 5'upstream DNA sequence in different cell lines. METHODS: Six kinds of XBP1 promoter deletion mutants were cloned into pGEM-Teasy vector, which included XBP1 gene 5' upstream -1039 to 66 bp,-859 to 66 bp,-623 to 66 bp,-351 to 66 bp,-227 to 66 bp,-227 to -45 bp respectively. Every deletion mutant sequence was cut from Teasy-XBP1p by KpnI and Xho I, and subcloned into pCAT3-Basic to produce a set of constructs termed as p1-XBP1p, p2-XBP1p, p3-XBP1p, p4-XBP1p, p5-XBP1p, p6-XBP1p, respectively. The transcription activity of each construct was detected after transiently transfecting K562, HepG2,NIH-3T3 and L0(2)cell with FuGENE 6 transfection reagent. Cells transfected by pCAT3-Basic or pCAT3-Promoter were used as negative and positive controls. The activity of chloramphenicol acetyltransferase(CAT), which reflects the transcription activation of the XBP1 gene promoter, was detected by ELISA after 48 hours of transfection. RESULTS: The reporter vectors of six kinds of XBP1 promoter deletion mutants were successfully constructed, as confirmed by restriction enzyme digestion and sequencing. The activities of p4-XBP1p and p5-XBP1p were higher than the other deletion mutants in K562 and HepG2. And the activity of p5-XBP1p was the highest in HepG2. There was no activity detected from any transfected NIH-3T3. CONCLUSION: The XBP1 gene promoter can transactivate its downstream gene to transcription. The core sequence of XBP1 promoter was implied between -227 bp and 66 bp. This sequence was connected with the transcriptional activity of XBP1 promoter closely. Its transcription activity varies with different cell lines. XBP1 promoter might drive gene expression with cell-type specificity.

[Effect of tacrolimus on apoptosis and expression of heat shock protein 70 after acute spinal cord injury in rats].

OBJECTIVE: To investigate the effect of tacrolimus on expression of heat shock protein 70 (HSP 70) after spinal cord injuries (SCI) in rats and the relationship between expression of HSP 70 and apoptosis of neural cells. METHODS: Seventy-two male rats were divided randomly into three groups: the sham-operation group, the injury group and the group treated with tacrolimus, and the latter two groups were SCI with a weight-drop impactor at the T(10) vertebrae level (10 g weight was dropped from a 4.0 cm height). The tacrolimus group was injected with tacrolimus 5 minutes after SCI, while the other groups received 0.9% saline likewise. The inclined plate and BBB (Basso, Beattie and Bresnahan) scales were used to evaluate hindlimb neurological function. The expression of HSP 70 mRNA after SCI was detected by using reverse transcription polymerase chain reactions (RT-PCR) and immunohistochemistry staining was performed to determine the protein expression of HSP 70 and Caspase-3. The apoptosis of neural cells was assessed with the terminal deoxynucleotidyl transferase-mediated deoxyuredine triphosphate-digoxin nick end labeling (TUNEL) method. RESULTS: Compared with the injury group, the expression of HSP 70 was significantly higher in the tacrolimus group, and the peak expression of HSP 70 mRNA and protein was respectively observed at 6, 24 h after SCI. Caspase-3-positive or TUNEL-positive cells were significantly less in the tacrolimus group than in the injury group. Neurological function score of the tacrolimus group was significantly better than that of the injury group. CONCLUSIONS: Tacrolimus may inhibit activity of Caspase-3, attenuate apoptosis of neural cells and ameliorate neurological function recovery after SCI by inducing high expression of HSP 70.