The cellular basis of mechanosensory Merkel-cell innervation during development

Touch sensation is initiated by mechanosensory neurons that innervate distinct skin structures; however, little is known about how these neurons are patterned during mammalian skin development. We explored the cellular basis of touch-receptor patterning in mouse touch domes, which contain mechanosensory Merkel cell-neurite complexes and abut primary hair follicles. At embryonic stage 16.5 (E16.5), touch domes emerge as patches of Merkel cells and keratinocytes clustered with a previously unsuspected population of Bmp4-expressing dermal cells. Epidermal Noggin overexpression at E14.5 disrupted touch-dome formation but not hair-follicle specification, demonstrating a temporally distinct requirement for BMP signaling in placode-derived structures. Surprisingly, two neuronal populations preferentially targeted touch domes during development but only one persisted in mature touch domes. Finally, Keratin-17-expressing keratinocytes but not Merkel cells were necessary to establish innervation patterns during development. These findings identify key cell types and signaling pathways required for targeting Merkel-cell afferents to discrete mechanosensory compartments.

Protective Mechanism of Adipose-Derived Stem Cells in Remodelling of the Skin Stem Cell Niche During Photoaging

BACKGROUND/AIMS

Skin photoaging is primarily caused by the functional attrition of skin stem cells. The skin stem cell niche plays an important role in maintaining stem cell survival and behaviour. In our study, we hypothesized that UVB irradiation induces skin photoaging by changing skin stem cell niches and that transferred adipose-derived stem cells (ADSCs) can remodel the niches by affecting the BMP signalling pathway and transdifferentiating into skin stem cells.

METHODS

Sixty-four C57BL/6J mice were divided into the following groups: a control group, the UVB group and the UVB+ADSCs group. Western blot assays, immunofluorescence analysis and real-time PCR were used to measure differences in the expression of niche components among the three groups. Furthermore, we tested whether transplanted ADSCs express skin stem cell markers, such as p63, α6-integrin and CD34.

RESULTS

The expression levels of Bmp4, its downstream factors Smad1 and MAPK1 and a regulatory factor of the niche, i.e., NFATc1, were lower in the UVB group than were those in the control group (P< 0.05) but higher in the UVB+ADSCs group than were those in the UVB group (P< 0.05). Compared with Bmp4, Nanog (a downstream factor of Bmp4), and MMP13 (a regulatory factor of the niche), ICAM-1 (a proinflammatory gene), p63 (a basal transcription factor), β1-integrin, Mtnr1a and Tyr (melanogenesis-related factors) showed the opposite expression trends (P< 0.05). Bmp2 and Collagen IV levels did not significantly change among the three groups (P> 0.05). Skin stem cell markers, such as p63, α6-integrin and CD34, were coexpressed in the ADSCs, which suggested the ADSCs may transdifferentiate into skin stem cells.

CONCLUSION

We found that UVB irradiation results in typical photoaging signs by altering skin stem cell niches and that Bmp4 was a key factor in BMP signalling in hair follicles. ADSCs reversed these typical photoaging signs by remodelling skin stem cell niches through BMP4 pathway modulation and transdifferentiation into skin stem cells.

Bone morphogenetic protein 4 and bone morphogenetic protein receptor expression in the pituitary gland of adult dogs in healthy condition and with ACTH-secreting pituitary adenoma

The purpose of this study was to investigate the expression of bone morphogenetic protein 4 (BMP4) and its receptors, bone morphogenetic protein receptor I (BMPRI) and BMPRII, in the pituitary gland of healthy adult dogs and in those with ACTH-secreting pituitary adenoma. Quantitative polymerase chain reaction analysis showed that the BMP4 messenger RNA expression level in the ACTH-secreting pituitary adenoma samples was significantly lower than that in the normal pituitary gland samples (P = 0.03). However, there were no statistically significant differences between samples with respect to the messenger RNA expression levels of the receptors BMPRIA, BMPRIB, and BMPRII. Double-immunofluorescence analysis of the normal canine pituitary showed that BMP4 was localized in the thyrotroph (51.3 ± 7.3%) and not the corticotroph cells. By contrast, BMPRII was widely expressed in the thyrotroph (19.9 ± 5.2%) and somatotroph cells (94.7 ± 3.6%) but not in the corticotroph cells (P < 0.001, thyrotroph cells vs somatotroph cells). Similarly, in ACTH-secreting pituitary adenoma, BMP4 and BMPRII were not expressed in the corticotroph cells. Moreover, the percentage of BMP4-positive cells was also significantly reduced in the thyrotroph cells of the surrounding normal pituitary tissue obtained from the resected ACTH-secreting pituitary adenoma (8.3 ± 7.9%) compared with that in normal canine pituitary (P < 0.001). BMP4 has been reported to be expressed in corticotroph cells in the human pituitary gland. Therefore, the results of this study reveal a difference in the cellular pattern of BMP4-positive staining in the pituitary gland between humans and dogs and further revealed the pattern of BMPRII-positive staining in the dog pituitary gland. These species-specific differences regarding BMP4 should be considered when using dogs as an animal model for Cushing's disease.

Expression analysis of bone morphogenetic protein 4 between fat and lean birds in adipose tissue and serum

The objectives of the present study were to characterize the tissue expression of chicken (Gallus gallus) bone morphogenetic protein 4 (BMP4) and compare differences in its expression in abdominal fat tissue and serum between fat and lean birds and to determine a potential relationship between the expression of BMP4 and abdominal fat tissue growth and development. The results showed that chicken BMP4 messenger RNA (mRNA) and protein were expressed in various tissues, and the expression levels of BMP4 transcript and protein were relatively higher in adipose tissues. In addition, the mRNA and protein expression levels of BMP4 in abdominal fat tissue of fat males were lower than those of lean males at 1, 2, 5, and 7 wk of age (P < 0.05). Furthermore, the serum BMP4 content of fat males was lower than that of lean males at 7 wk of age (P < 0.05). BMP4 mRNA expression levels were significantly higher in preadipocytes than those in mature adipocytes (P < 0.05), and the expression level decreased during differentiation in vitro (P < 0.05). These results suggested that chicken BMP4 might affect abdominal fat deposition through differences in its expression level. The results of this study will provide basic molecular information for studying the role of BMP4 in the regulation of adipogenesis in avian species.

Overexpression of the BMP4/SMAD signaling pathway in skull base chordomas is associated with poor prognosis

Chordomas are rare, locally invasive tumors with characteristic expression of the T-box transcription factor Brachyury. Little is yet known of the molecular events involved in the development of these tumors. Bone morphogenesis protein 4 (BMP4) signaling, which acts upstream of Brachyury in embryonic development, has been implicated in carcinogenesis in multiple malignancies. To explore the role of the canonical BMP4/SMAD signaling pathway in the pathogenesis of chordoma, we investigated, in 40 skull base chordomas, the expression of three major components of the signaling axis: BMP4, phospho-SMAD5 and SMAD4. Immunostaining revealed positive expression in 70%, 52.5% and 90% of cases, respectively. Eighteen (45%) of patients exhibited concurrent positive expression of these markers, which we defined as "high" expression of the BMP4/SMAD signaling pathway. Interestingly, when we compared the pattern of expression with clinicopathological parameters, we found that high expression of the pathway was more often observed in larger tumors (≥ 4 cm) than smaller ones (P = 0.010), and correlated significantly with dural invasion (P = 0.024). The Kaplan-Meier log-rank test showed that the 5-year overall survival rate for patients with high expression of the pathway was significantly lower than those with low expression (71.4% vs. 90.2%, P = 0.010). In conclusion, our results demonstrate for the first time that overexpression of the BMP4/SMAD signaling pathway could predict poor clinical outcome in skull base chordomas, suggesting activation of this pathway is involved in chordoma pathogenesis.

Expression of growth factors and growth factor receptors in human cleft-affected tissue

OBJECTIVE. To investigate cleft disordered tissue in children with cleft palate and cleft lip with or without alveolar clefting for detection of local tissue growth factors and growth factor receptors and compare findings. Design. Morphological analysis of human tissue. Patients. Three groups were studied: 14 patients with cleft palate at the age from eight months to 18 years and two months, 12 patients with cleft lip with or without alveolar clefting in the age from four months to 15 years and four months and 11 control patients. RESULTS. In general, cleft palate disordered tissue showed more prominent expression of BMP2/4 (z=3.574; p=0.0004) and TGFβ (z=2.127; p=0.033), while expression of TGFBR3 significantly higher was only in connective tissue (z=3.822; p=0.0001). Cleft lip affected tissue showed significantly pronounced expression of FGFR1 in general as well as separately in epithelium. CONCLUSIONS. The marked and statistically significant expression of BMP 2/4 in cleft palate disordered soft tissue probably is delayed, but still proliferation and differentiation as well as tissue, especially, bone remodeling contributing signal. Cleft palate affected tissue show more prominent expression of TGFβ, still the weak regional expression of TGFβ type III receptors prove the disordered tissue growth and changed TGFβ signalling pathway in postnatal pathogenesis. In general, expression of TGFβ, BMP 2/4 and FGFR1 is significantly different, giving evidence to the involvement of these mentioned factors in the cleft severity morphopathogenesis.

Effect of hyperbaric oxygen on neurological recovery of neonatal rats following hypoxic-ischemic brain damage and its underlying mechanism

OBJECTIVE

To investigate the mechanism underlying the effect of hyperbaric oxygen (HBO) on hypoxic/ischemic brain damage (HIBD) in a neonatal rat model.

METHODS

A total of 30 neonatal SD rats aged 7 days were randomly assigned into control group, HIBD group and HBO group (n=10 per group). Following HIBD modeling in neonatal rats, HBO treatment was performed for consecutive 7 days. Immunohistochemistry was done to measure the expression of bone morphogenetic protein-4 (BMP-4) and nestin in the hippocampus. In situ hybridization was employed to detect the mRNA expression of BMP-4 and nestin in the hippocampus. TUNEL staining was done to detect the apoptosis of nerve cells.

RESULTS

HIBD was successfully established in the present study. Among three groups, the protein expression of BMP-4 in the hippocampus was the highest in the HBO group, and the smallest in the HIBD group. The BMP-4 expression in the HIBD group was significantly lower than that in the control group. The protein expression of nestin in the hippocampus was the highest in the HBO group, and the smallest in the HIBD group. The nestin protein expression in the hippocampus of HIBD group was significantly lower than that in the control group. The mRNA expression of BMP-4 in the hippocampus was the highest in the HBO group, and the smallest in the HIBD group. The mRNA expression of nestin in the hippocampus was the highest in the HBO group, and the smallest in the HIBD group. The number of apoptotic cells was the largest in the HIBD group, and the number of apoptotic cells in the HBO group was still larger than that in the control group (P<0.01).

CONCLUSION

HBO may promote the neurological recovery in neonatal rats with HIBD, which may be attributed to the increased protein and mRNA expression of BMP-4 and nestin in the hippocampus and the inhibition of neural apoptosis.

O45-regulation of osteoblast differentiation and ECM remodeling by Bmp2/4 in vitro

Both of bone morphogenetic proteins 2 and 4 (Bmp2 and Bmp4) are two closely related members of the transforming growth factor beta superfamily and play diverse roles in normal and pathological processes. However, detail understandings of mechanisms through which Bmp2 and Bmp4 exert their effects remain elusive due to their functional compensations each other. To study roles of Bmp2/Bmp4 in osteoblast differentiation and extracellular matrix (ECM) remodeling, calvarial osteoblasts from Bmp2/4 conditional mice with Cre recombinase recognition site (loxP) were isolated and transfected with simian virus 40 large T antigen to generate immortalized BMP2C/C4C/C (iBMP2 C/C/4C/C) osteoblast lines. The BMP2/4 genes in the iBMP2 C/C/4C/C cells were double knocked out by Ad-Cre recombinase infection. Differentiation and mineralization of iBMP2C/C/4C/C knock-out (iBmp2C/C/4C/C KO) cells were detected by alkaline phosphatase (ALP) and alizarin (ALZ) red S staining analyses. ECM remodeling was also observed in fluorescent microscope. Cell differentiation was dramatically decreased in the iBMP2C/C/4C/C KO cells compared to that of the iBMP2C/C/4C/C osteoblasts. Mineralization was also reduced in these KO cells by ALZ staining. Furthermore, Bmp2/4 double knock-out cells have major defects in remodeling the ECM as reflected by changes in collagen type I processing. Here we for the first time demonstrate the establishment of iBmp2C/C/4C/C KO osteoblasts. Cell differentiation and mineralization in the iBmp2C/C/4C/C KO cells were decreased. Furthermore, ECM processing in these KO cells was impaired. This indicates that BMP2/4 play important roles in osteoblast differentiation and ECM remodeling.

Growth factors, genes, bone proteins and apoptosis in the temporomandibular joint (TMJ) of children with ankylosis and during disease recurrence

AIM OF STUDY was complex detection of appearance and distribution of growth factors, facial bone growth stimulating genes, ground substance proteins and apoptosis in bone of ankylotic TMJ in primary and repeatedly operated children.

MATERIALS AND METHODS

Ankylotic tissue was obtained during the arthroplastic surgery from two 6 years old children (boy and girl) with osseous type of disease. The girl underwent the repeated surgery in TMJ due to the same diagnosis in age of 12 years. Ankylotic tissue was proceeded for detection of BMP2/4, TGFβ, Msx2, osteopontin, osteocalcin immunohistochemically, and apoptosis. RESULTS demonstrated massive bone formation intermixed by neochondrogenesis the lack of BMP 2/4, but abundant number of TGFβ-containing cells in bone of all tested cases. Despite rich osteopontin positive structures in bone obtained from both - primary and repeated surgery, osteocalcin demonstrated variable appearance in 6 years aged children, but was abundant in joint 5 years later during disease recurrence. Expression of Msx2 varied widely before, but with tendency to decrease stabilized until few positive cells in bone of 12 years old girl. Apoptosis practically was not detected in primarily operated TMJ, but massively affected the supportive tissue in girl with recurrent ankylosis.

CONCLUSIONS

The lack of BMP2/4 expression in ankylotic bone proves the disorders in cellular differentiation with simultaneous compensatory intensification of cellular proliferation and/or growth by rich expression of TGFβ leading to the remodelling of TMJ. Mainly rich distribution of osteocalcin and osteopontin indicate the intensive mineralization processes of ankylotic bone. Persistent Msx2 expression is characteristic for the supportive tissue of recurrent ankylosis of TMJ and indicates the persistent stimulation of bone growth compensatory limitated by massive increase of programmed cell death.

Specific signaling molecule expressions in the interradicular septum in different age groups

INTRODUCTION

Orthodontic teeth movement is accompanied by the remodeling of alveolar bone, including the interradicular septum. Bone contains three cell types, osteoblasts, osteocytes, and osteoclasts that are in direct contact with all of the cellular elements in the bone marrow. Marrow is the source of both bone-building osteoblasts and bone destroying osteoclasts, and the turnover of bone occurs throughout life. Bone signalling molecules have important functions during osteogenesis, and they are active in the bone remodelling process. Patients involved in orthodontic treatment belong to different age groups: therefore age must be considered as a contributing factor compromising the osteogenetic potential of bone. The aim of the current study was to investigate the specific expression of signalling molecules in the interradicular septum in different age groups.

MATERIALS AND METHODS

The study group included 17 patients to whom the extraction of teeth was recommended as part of further orthodontic treatment. Patients (9 males and 8 females) - were divided into 3 groups 1st group - 12-14 years old); 2nd group - 15-22 years old; 3rd group - 23 years old or older. Expression of BMP 2/4, TGF-α, IL-1, IL-8, OPG, MMP-1, MMP-2, MMP-8, MMP-9, MMP-13, NGFR, NKpB 105, osteocalcin, and osteopontin in interradicular septum tissues was examined. TUNEL staining was also completed. The distribution of these factors was evaluated semi quantitalively.

RESULTS

In the interradicular septum bone structure, the expression levels of osteocalcin, osteoprotegerin, matrix metalloproteinases 8 and 9, and nuclear factor kappa B were determined in all samples. TUNEL staining was also done. Age related decreases in the mean values of signalling factors and the number of apoptotic cells were statistically significant.

CONCLUSION

Specific to interradicular septum osteoblasts and osteoclasts factors include osteoprotegerin, osteocalcin, matrix metalloproteinase 8, matrix metallproteniase 9, and nuclear factors kappa B. The mean expression levels of these proteins and the mean TUNEL staining statistically significantly decreased with age. This is preliminary study and more patients are necessary for more precise statistical analysis in the future.

[Effects of antenatal administration of dexamethasone and betamethasone on signal transduction of bone morphogenetic protein in the fetal lungs of rats]

OBJECTIVE

To study the role of antenatal glucocorticoid (dexamethasone and betamethasone) on bone morphogenetic protein (BMP) signal transduction of the rat fetal lungs.

METHODS

Fifteen pregnant rats were randomly divided into five groups: the rats treated with dexamethasone for 1 day (1D-DEX) or 3 days (3D-DEX), with betamethasone for 1 day (1D-BEX) or 3 days (3D-BEX) or with normal saline (control group), followed cesarean section on the 19th day of gestation. The mRNA levels of BMP4, BMPR-II, Smad1 and ATF-2 of fetal rat lungs were ascertained by reverse transcriptase polymerase chain reaction (RT-PCR). The expression of BMP4, BMPR-II, Smad1 and ATF-2 antigen expression in fetal lungs was assessed by immune histochemical staining. The expression of BMP4 and BMPR-II was determined by Western blot.

RESULTS

The levels of BMP4, BMPR-II and Smad1 mRNA expression were up-regulated in the 1D-BEX, 3D-BEX and 3D-DEX groups compared with those in the control group (P<0.05). The immune histochemiscal analysis showed that the expression of BMP4, BMPR-II, Phospho-Smad1 (pSmad1) and ATF-2 in the 1D-BEX, 3D-BEX and 3D-DEX groups was significantly higher than that in the control group (P<0.01). The results of Western blot demonstrated that the expression of BMP4 and BMPR-II protein increased significantly in the 1D-BEX, 3D-BEX and 3D-DEX groups when compared with the control group (P<0.01).

CONCLUSIONS

Betamethasone and dexamethasone may play important roles in the regulation of BMP signal transduction in the rat fetal lungs. Up-regulation of BMP4, BMPR-II and Smad1 might be one of crucial factors for the glucocorticoid-induced maturity of fetal lungs.

Bone morphogenetic protein signaling in the murine distraction osteogenesis model

A murine distraction osteogenesis model was standardized to allow analysis of the molecular pathways associated with postnatal de novo bone formation. The authors examined the presence and expression of Bone Morphogenetic Proteins (BMPs) -2, -3, -4, -6 and -7, and the BMP receptors Alk3 and Alk6 at different stages. Strong signals were detected for BMP-4 at the end of the distraction period and for BMP-6 during the entire experimental period. Signals for BMP-7 (Osteogenic Protein-1) were very low, suggesting a less important role during the normal process of distraction bone healing. Immunohistochemical staining revealed the presence of BMP-4 in the early chondroblasts, while BMP-6 was detected in the more mature cartilage cells. The data indicate a BMP molecular profile reminiscent of the embryonic maturation process in endochondral bone formation.