Lab Assessment 1
In Vitro Fertilization (IVF) is a popular method of Assisted Reproduction which allows for fertilization to occur under optimal conditions (which may not be achieved in those that are having trouble conceiving), with monitored hormone levels and calculated growth of the embryo so as to maximize implantation, and ideally, successful pregnancy. This research article endeavors to assess the different variables available in IVF to determine which method yields the most successful amount of pregnancies. The variables in question are whether the embryo should be fresh (within a hours of fertilization), or frozen-thawed (embryo frozen a few days after fertilization and thawed when the mother is ready to receive an embryo). Another variable considered is the developmental stage at which the embryo is implanted; some embryos are implanted at the cleavage stage (hours after fertilization) and others are implanted at the blastocyst stage (5 days after fertilization), this study also considered implants at the cleavage stage extended blastocyst stage however it did not clarify what this term means, and I was unable to find elsewhere what this means.
This study observed IVF cycles of 1891 women at the Wuhan Union Hospital between January and December of 2012. Of the 1891 women observed, 1150 had fresh embryo transfers and 741 had frozen thawed embryo transfers. Of the Fresh embryo transfers 993 were implanted at the cleavage stage (799 of them women were less than 35 years old and 194 were greater than or equal to 35 years old), and 157 were implanted at the blastocyst stage (131 were less than 35 years old, 26 greater than or equal to 35 years old). Of the 741 women with frozen thawed embryo transfers, 212 were implanted at the cleavage stage of embryonic development (159 women were less than 35 and 53 were greater than or equal to 35), 137 were implanted at the cleavage stage extended blastocyst stage (111 were less than 35, 26 were greater than or equal to 35) and 328 were implanted at the blastocyst stage (276 were less than 35, 52 were greater than or equal to 35). All of these women underwent traditional methods of IVF- that is they were initially treated with Gonadotropin Releasing Hormone to stimulate follicular development. When two or more follicles were greater than 18mm Human Chorionic Gonadotropin was injected to assist follicular maturation. 24-26 hours later the ova were collected (Ovum Pick Up/OPU) and 4-6 hours after OPU IVF or Intracytoplasmic Sperm Injection (ICSI) were performed on the ova. The embryos were assessed by morphology and rate of development and at day three they are transferred onto a blastocyst medium and cultured for 2-3 days until it forms a blastocyst. The blastocysts are socred according to the Gardner standard and usually 1-2 good embryos are implanted. The remaining viable embryos are cryopreserved via vitrification and may be used if the current IVF cycle is unsuccessful. The Estrogen and Progesterone levels are monitored and regulated throughout the process according to the characteristics of the patient. Clinical pregnancy was defined by the presence of a gestational sac with or without a heart beat 30 days after implantation.
From this experiment it was found that there was a greater amount of successful pregnancies in women less than 35 years old resulting from implantation of fresh embryos at the cleavage stage (52.7% success) as opposed to the blastocyst stage (35.88%). There was no statistically significant differences clinically between the two types of implantation [ie- multiple pregnancies, abortion or ectopic pregnancy]. There were also a significantly higher number of pregnancies in the cleavage stage [41.24%] vs the blastocyst stage [26.92%]. However, this was not that case for those whom has frozen-thawed embryo transfers, as there was generally a much greater success rate for pregnancy in those who had blastocyst stage transfers than those who had cleavage stage transfers. Furthermore, there is a significantly greater pregnancy rate between in fresh embryo transfers compared to frozen thawed embryo transfers at the cleavage stage. Overall, there was a greater incidence of clinical pregnancy resulting from fresh cleavage stage embryo transfers compared to any other type of transfer [ie fresh blastocyst stage, frozen thawed cleavage stage and frozen thawed blastocyst stage]. These researchers concluded that this type of implantation should be used under normal conditions, and other methods should only be considered if the mother is of compromised health (eg has Ovarian Hyper Stimulation Syndrome), in which case as fresh blastocyst stage embryo is used.
<pubmed>25017405 </pubmed> This article aimed to assess the success rate of clinical pregnancy of women at differing age groups whom have undergone assisted reproductive methods such as In-Vitro Fertilzation and Intracytoplasmic Sperm Injection. Based on previous literature it was expected that the success rate would decline as the woman ages, as typically the most successful IVF cycles are seen in women whom are 25-30 years old. Also based on natural conception rates, spontaneous conception rates begin to decrease around 31-35 years old, and women tend to have difficulty conceiving around the ages of 35-39. General fecundabilty (probability of released ovum becoming fertilized and resulting in a successful pregnancy in one menstrual cycle) tend t decrease as the woman reaches menopause (around the early fifties) and at 5-10 years prior to this (40-44 years old), half of the women have reduced reproductive capacity.
This study observed 2,900 women undergoing IVF at the KK Women and Children’s hospital, of which yielded 3,412 fresh IVF cycles. The women were classifies into sub groups based only on age [< 30 years; 30–35 years; 36–37 years; 38 years; 39 years; 40–44 years; and ≥ 45 years]. The IVF cycles were monitored and the average number of occytes, average duration of stimulation and fertilization rates were observed. Furthermore, the number of cycles until successful embryo transfer, clinically successfully pregnancy rates, miscarriage rates and multiple pregnancy rates were also reported. In this study, most of the patients undergoing IVF were between the ages of 30-35 and 36-37, and the least amount of patients belonged to the ≥ 45 years group. Of these, it was found that there was a 15% miscarriage rate in those younger than 30 years old, but this figure doubled to 30% at the age of 38 and among women aged 40-44, the miscarriage rate was as high as 55%. Only half of the women aged greater than 45 reached embryo transfer, and of those, none proceeded to successful clinical pregnancy. Furthermore, compared to other age groups, these women had the lowest amount of oocytes collected and the lowest fertilization rate with only 50% of oocytes proceeding to fertilization, compared to 95% in women less than 30 years old. However, it was found that there was no differences in mean duration of ovarian stimulation prior to ovum collection based on age. Finally, it was found that there was a general decreasing trend of successful clinical pregnancies as age increased in women undergoing IVF, as the rate of live births was highest in women who were less than 30 years old. The occurence of multiple births was highest in this age group also.
Overall it was found that the age of the woman undoubtedly has an effect on the reproductive capacity of a woman undergoing IVF. The researchers hypothesized that the general decreased success of an aging woman may be due to decreasing ovarian reserve, poorer oocyte quality, lower embryo implantation rates, altered hormonal environment resulting in ovulatory dysfunction and uterine problems. Male factors were also considered to be causative.
--Mark Hill These papers are suitable for the assessment exercise and you have included an appropriate summary. (5/5)
Lab Assessment 2
Mutation of Gene Wt1 Causes Aberrant Gonadal Development
- <pubmed>23497137 </pubmed>| 
--Mark Hill This is a relevant image. I have fixed a few formatting issues in the associated file information, don't include the .jpeg in the figure legend, see the image page history for changes. (5/5)
Lab Attendance: LAB 2
--Z3416697 (talk) 12:56, 20 August 2014 (EST) Forgot to do my attendance at the lab of week 3 given by guest Speakers Hayden Homer and Rob Gilchrist about meiosis, oocyte quality and various technologies in assisted reproduction
Lab Attendance week 4
Lab three Online Assessment
Genital system development is an extremely interesting area of embryology as it is not until the later stages of embryogenesis (around week 4-6) that sexual differentiation occurs in the fetus, and the sexual organs actually look very similar up until this point, and the formation of the correct sex organs depend really on whether the genital ridge releases Testosterone or oestrogen <pubmed>24240231</pubmed> <pubmed>24928207</pubmed> <pubmed>24741072</pubmed> --Z3416697 (talk) 20:10, 26 August 2014 (EST)
--Mark HillThese 3 references meet the assessment requirement, it appears that you have just included the references without a description? Your description of genital differentiation is not quite accurate and should be clarified by the future Genital Development Lecture. (4/5)
Lab 4 Attendance
Lab 4 Online Assessment
Hepatocellular carcinoma and other degenerative liver diseases often result in hepatic dysfunction and ultimately organ failure. To avoid this otherwise fatal diagnosis, bio-artificial livers and hepatocyte transplantation provides some leg- room whilst waiting on a full-organ transplant. However liver transplants, much like many other organs, are often hard to come by and are usually sensitive to the immune response of the host. As a result, researchers are looking towards stem cells as an answer to this problem. Mesenchymal stem cells derived from the Wharton’s Jelly of the umbilical Chord are often chosen because they have been found to have a slightly higher multipotency and immunogenicity. The umbilical stem cells were selected because they are more primitive compared to other Mesenchymal stem cells and do not express the major histocompatibility complex class II antigens- a key determinant in illiciting an immune response form the host. However, hepatocyte like cells derived from stem cells are not clinically used because they do not express enough functional proteins and do not exhibit a full level of metabolic activity.
This study aimed to identify and observe the transcription factors involved in hepatocyte differentiation from Human umbilical cord Mesenchymal Stem Cells (HuMSCs), they were particularly interested in Hepatocyte Nuclear Factor 4-alpha (HNF-4alpha) which is believed to behave like a “master gene” in driving hepatocyte differentiation and maturation. This study continued to expose the differentiating HuMSCs to excess amounts of HNF-4alpha and hypothesized a significant improvement in the differentiation status of the hepatocyte-like cells, providing a basis for future clinical application of HuMSCs in the treatment and management of liver diseases.
The research initially confirmed that the HuMSCs are of low immunogenicity- a critical issue with organ transplantation. Once this was confirmed, they observed that there was an up-regulation of functional hepatic enzymes once the differentiating hepatocyte-like stem cells were exposed to HNF-4alpha. An important finding they discovered that the time at which the stem cells were exposed to HNF-4alpha were integral in ensuring correct hepatocyte differentiation. Ultimately they concluded that the differentiation of HuMSCs could be improved by exposure to high levels of HNF-4alpha at specific times in the development of hepatocyte-like stem cells, an important discovery for the progression of the therapeutic application of stem cells.
The three shunts which are present in fetal development but are closed postnatally are:
• ductus arteriosis → channel between the pulmonary artery and aorta in the fetus which bypasses the lungs to distribute oxygenated blood from the placenta derived from the mothers circulation.
• ductus venosus → shunts a portion of the left umbilical vein blood flow which would flow directly to the inferior vena cava- allows b=oxygenated blood to bypass the liver.
• foramen ovale → allows passageway of blood from left atrium to right atrium in the fetus.
--[[User:Z8600021|Mark Hill] Very good, shunts are also correct (5/5)
Lab 5 Attendance
Lab 5 Online Assessment
Congenital Lobar emphysema (CLE) is a condition of the respiratory system which results in hyperinflation of one or more pulmonary lobes and is usually diagnosed postnatally, usually in the neonatal period- however there have been cases where CLE is not diagnosed until 10 years after birth. The clinical symptoms of CLE are often at birth as dyspnea, cyanosis and recurrent respiratory tract infections, as well as generalized neonatal respiratory distress and hyperinflation and hyperaeration of the pulmonary lobes- often seen as visible enlargements or imaged through CT. CLE is a rare disorder affecting only 1 in 20,000 to 30, 000 newborns, and appears to have a slight male predominance [3:1 male to female ratio], although the cause of this gender predilection is not fully understood.
The developmental causes of CLE are often as final result of a number of bronchopulmonary disturbances during development. These result from abnormal interactions between embryonic endodermal and mesodermal components of the lung which may result in abnormalities in airway or alveoli number and size, however the exact pathogenesis of CLE is not able to be determined in approximately half of cases. Another frequently observed cause of CLE is an obstruction of the developing airway, which creates a “ball valve” resulting in an uneven distribution of air- favoring greater airflow to the affected lobe during inspiration than is able to be cleared in expiration- resulting in air trapping. There may also be vascular abnormalities which produce compression, bronchial stenosis, bronchogenic cysts and congenital cytomegaloviral infections observed.
--[[User:Z8600021|Mark Hill] This is OK, your source citation is not from the highest quality journal nor related to developmental journals. It also does not look into developmental causes. (3/5)
Lab attendance week 8
Lab Report- week 8
This paper aims to identify the correlation between differing levels of androgen exposure during the fetal period on testosterone production from Leydig cells during adulthood. A low level of adult testosterone production in men is related to an increased rate of aging, as well as cardiometabolic syndromes, pro-inflammatory changes, frailty and increased mortality. Due to the impending clinical significance of such study, coupled with the limited understanding of fetal programming of Leydig cells, these researchers endeavored to find the influences of fetal exposure to androgens on the production of testosterone later in life. This paper hypothesizes that fetal programming of Leydig pro-genitor cells by exposure to androgens has a direct correlation to androgen production during puberty and adulthood, and further hypothesized that exposure to lower levels of androgens may result in the development of testosterone- dependent disorders such as male infertility.
Based on murine models, it was found that Leydig cells (interstitial cells of the testis which do not develop until puberty) are present in the fetal period as pro-genitor, or ‘stem’ cells, and manipulation of the transcription factors involved in the production and regulation of these stem cells can affect the behavior of adult testosterone production, an example of such a transcription factor is COUP-TFII. To briefly outline the findings of this study, it was initially identified that adult Leydig cells were derived from stem cells which were under COUP-TF11 transcriptional control. Once this was established, the researchers identified that these stem cells possessed androgen receptors, and that experimental reduction of androgens to these stem cells in the fetal period resulted in a reduced stem cell population in adulthood and subsequently adult Leydig cell failure. Another component of this study was to identify possible mechanisms where there would naturally be decreased or aberrant androgen exposure in the fetal period and hypothesized that it may primarily be due to altered histone methylation (an epigenetic event) at the gene promoter for steroidogeneic acute regulatory protein (H3K27me3). Ultimately these studies were done in the hopes of understanding the causes and fetal influences of reduced testosterone production in humans, which can have an impact on the development of diseases such as testosterone-dependent cardio-metabolic disorders, and even mortality in humans.
Identify the embryonic layers and tissues that contribute to the development of teeth
- Odontobolasts: These cells originate from the neural crest mesenchyme and differentiate under enamel epithelium influence. These cells have functions in dentiogenesis and secretes predentin which will ultimately calcify to dent.
- Ameloblasts: derived from the oral epithelium of the ectoderm- function to deposit tooth enamel after the initial production of dentin by odonotoblasts. Form the outer layer of tooth.
- Periodontal Ligament: specialised connective tissue which develops from the dental sac of the tooth. Acts as an anchor for the tooth.
--[[User:Z8600021|Mark Hill] I can see how this relates to genital (endocrine) development, but not directly to the assessment requirement. It is a good summary of the paper. Tooth is fine (4/5)
lab Attendance WEEK 9
lab report week 9
This paper endeavoured to provide an extensive overview of mammalian ovary development, drawing comparisons of human ovary development to that of sheep, mice and cattle. Whilst there are time differences between these mammalian species, it appears that structurally the development of the ovary is very similar provides a relevant model for human ovarian development. The ovary initially begins as a thickening of the coelomic epithelium on the medial aspect of the mesonephros. The mesonephros, which acts as a transient kidney in mammals, contributes to the tubules and cells in the ovary as it develops and regresses in females.
Primordial germ cells (PGCs) are an important key feature of ovigenesis. PGC’s, which originate from the endoderm of the yolk sac, migrate through the developing hindgut and along the dorsal mesentery and ultimately enter the developing gonads. This process occurs in days 7-11 in mouse, 17-21 in sheep and 18-31 in cattle. Once in the gonadal region, the PGC’s begin to proliferate. The KIT ligand plays an important role in germ cell proliferation and survival, as well as extracellular matrix proteins such as fibronectin. PGC’s being stem cells are multipotent in nature, and this is maintained by the expression of transcription factors such as OCT4, whose activity ceases at the initiation of meiosis in the ovary.
The ovarian role in sexual differentiation was often seen as the “less active” pathway, comparative to testis development in males. The process of gonadal sexual differentiation commences at day 12 of mice, 32 in sheep and 40 in cattle (still within the embryonic period of humans). Ovary and ovigerous cord formation, which is not dependent on the SRY gene, occurs at a relatively delayed time course and does not begin to emerge until day 40 of sheep. Upon sexual differentiation, there are at least 5 cell types recorded- ovarian surface epithelium, endothelial cells which form blood vessels, Mesenchymal cells, pre-granulosa cells and PGCs. Recent study also indicates that there are Gonadal Ridge Epithelial-Like (GREL) cells present at sexual differentiation which progress to form the genital ridge from the surface epithelium of the mesonephros. It was found that these GREL cells give rise to ovarian epithelium, and re involved in the initial establishment of germ-cell-pre-granulosa cell complexes. At this point, oogonia and pre-granulosa cells are distinct and are separated by remnants of smooth endoplasmic reticulum- indicative of steroid producing cells. Fetal sheep from as early as day 35 of gestation can produce hormones such as progesterone and androstenedione.
--[[User:Z8600021|Mark Hill] Good summary of a review paper, I prefer research articles to be used. The assessment was "embryonic Development" have you identified the embryonic period in these animal models? (4/5)
Lab attendance week 10
Lab assessment week 10
--Z3416697 (talk) 00:56, 15 October 2014 (EST) Group 1 This project is extremely well done. I found the overall layout of your work to be easy to read and succinct. It captured my attention throughout the entirety of the project and was engaging with the use of bullet points. I thought your use of diagrams was great in aiding the understanding of this topic, however I thought that more diagrams or pictures could be added in order to help the reader visualize exactly what’s going on. I thought that te developmental timeline was a great idea, however could benefit from some more images or diagrams to assist in understanding the developmental stages. I thought the historic findings sections was especially well done as it appears well researched and thoroughly informative. The abnormalities was also well done, however again could benefit from the addition of a few more diagrams.
I think that with the addition of more drawings needs to be some attention to detail when referencing and stating copyright. I’ve noticed that some pictures lack copyright and some don’t have a description, making it difficult to understand the context of the picture and to envisage how it relates to the content. Whilst this is mostly self explanatory- I think that because this is an informative piece it pays to spoon-feed us a bit. Also, your referencing could use a bit of a tidy, but that can easily be fixed before submission. I think that overall this has great potential to be a wonderful project and I look forward to seeing it at its completion!
Group 2 I think that this is a great start to the project. Your project appears well researched and informative, yet there are a few areas which need improvement to ensure that your project clearly demonstrates the developmental stages of renal development. I thought that over, the introduction was a good start to the project and clearly identifies the major components of the renal system and its functions. Because this is highly descriptive, I think it would benefit from a diagram or even video which could couple your description. The developmental timeline is a good idea, however I think severely lacks content. It would be a good idea to add a table or some form of diagrammatic representation of the historical findings, and the addition of pictures would greatly benefit the clarity of your work.
The current research is quite well done and seems heavily researched. There are areas which are a little bit too wordy at times, and your paragraphs are quite long- I think it would be of great benefit if you were to reduce your paragraphs into shorter bullet points so as to convey the main ideas that you are speaking about. Also, maybe a table would assist in ensuring the clarity of your work.
Overall, I think this is a great project and is off to a good start! There are a few things that need fixing- such as the developmental timeline, but I’m sure that it will come along nicely by the time submission is due.
Group 3 Overall this is a good project; I enjoyed the tailored diagrams and presentation of information in a succinct manner. Information is presented in a logical and coherent manner. The presentation of information into specific components such as foregut, mid gut, hind- gut is great.
The quality of research is exceptional and well presented. Specifically, the subsection of mid gut and the use of visual aids assist immensely in the translation of complex concepts into simple ones. The use of dot-points succeeds in summarizing the information into easily digestible sections. This also improves the clarity of the page. The use of subheadings also assists with the logical analysis of the project.
However, the referencing could potentially be more extensive. A further expansion on current research model and findings will prove to be instrumental in generation of a solid understanding of the project hand. I would recommend splitting recent findings into current research models and historic findings.
It would have been beneficial to see more information on the foregut section, as this would have provided a pronounced understanding of the topic at hand. It would assist in the comprehension of the data if the timeline were tabulated. Further expansion of the abnormalities would be needed. It would be great if the abnormalities in the hindgut were moved into the abnormal section. The grammar and punctuation is sound and the readability is good. The presentation of information is lucid and shows a sound understanding of the concepts involved.
Group 5 Overall I was very impressed with this project page. I loved your use of pictures and diagrams as it provided a great understanding of what was happening- and also, a lot of the images were quite interesting- which is a great thing for a project! I also enjoyed the use of bullet points- it was very to the point and it retained my attention throughout the piece. I did find, however, that the introduction was a bit short. Whilst it did cover most of what was required, I don’t think it hurts to be a bit more exhaustive in what you’re saying, because the introduction sets the mindset of the reader for the rest of the project- and if they have a clear understanding from the start, it makes it much easier when you are explaining more complex things such as the abnormalities later on.
Overall, I thought that the developmental timeline was extremely well done, and a highlight of your project. The rest of the developmental overview was quite well done, however I think in areas it was a bit sloppy, and it would be of great benefit to clear this up so as to improve the clarity of your work. Further, I enjoyed the succinctness of your paragraphs, it made it easy to read and wasn’t too much to take in at once.
I think that currently, your use of colour is a bit random in the recent findings. I think that this could really boost your project if you applied it to more areas of the page. As far as the content goes, I think that the recent findings is just too wordy and I began to lose my concentration a bit. I think maybe by forming more succinct dot points- you will be able to convey your message more clearly.
I think the historic findings could do with a bit more beefing up, but what you have so far is well done. The abnormalities is also very well done, and I think that your use of images really grab the readers attention.
I think that overall this project is shaping up to be a great one. I think you need to be careful and consistent with your referencing though as I noticed some sections lacked in-text citations.
Group 6 Overall, this is quite a good project considering the complexity of the system. I think that generally, this project would benefit from some restructuring, so as to improve the cohesiveness of your work. I think that an introduction is a good idea to organize your ideas and give the reader a good background when trying to understand some of the more difficult concepts. I think that the choice of sub headings should be advised. It is interesting that you have chosen to deviate from the given subheadings, and I understand for your system that that may be necessary- however I think that some structure or regular subheadings for each part may be a bit easier to control. Also I think an overall timeline is always a great idea as it provides a visual representation and puts things into perspective. I also think that some areas could use a bit more research, for example a large part of the pineal gland and hypothalamus appears to be missing and there are kind of “insert text here” sections- which I’m sure you’ll work on by the submission date. I also think its important to remember that your referencing needs to be carefully done and consistent. Currently it seems quite poorly organized, and I think overall could use with a few more resources for every section. I think because you are already deviating from the normal structure of things, it would be a good idea to leave your references until last, just so your work isn’t broken up even further. The abnormalities section is severely lacking- the table is a good idea, but make sure you fill it! Overall a good start, some places need some serious content others just need a tidy up.
Group 7 This project is coming along quite nicely! The introduction is very thorough and provides a really sound basis for the topics which you covered. I enjoyed the use of diagrams in your introduction- although I admit your flow diagram was very scary! I think you should be a bit more clear in your timeline of the human neural development – it took me a moment to figure out what was happening, so it may be a better idea to put all this information into a table. The images that you have used are great as they are relevant and provide interest to your project page. The referencing on them appears consistent and there doesn’t appear to be any copyright issues- so I think you should include a few more diagrams, just to make your message even clearer. The current research models could do with some reformatting. I don’t think it is a good idea to put the references at the start, and secondly it seems like your work is not so well structured. I think if you included some bullet points in your work, it would greatly aid the clarity. The abnormalities is off to a good start, I see that it is well researched but you want to consider adding some more pictures or diagrams just to make it a bit more visually appealing. Overall this project is off to a good start, I think it may be a good idea to leave all your references until the end just to make your work more cohesive.
Group 8 Firstly, I thought the “Making Gains” bit was great- and I can guess who came up with that. I know you’ll take it our prior to submission though haha. The structure of your project is quite good, and the subheadings would make it much easier to read- the only thing is you need to add more content! I think because your system encompasses quite a lot, it would be a better idea for you to put as much information as you can into tables and include diagrams- I saw that musculoskeletal development has quite a few visual resources so it you should use them! There are some areas where the content is really sparse, yet others where it is extremely heavy. In these areas, you may benefit from putting your information into bullet points so as to alleviate any confusion that may arise and overall enhance the clarity of your work. The references you have done are quite good, but there appears to be some missing.
Overall, I think your project would greatly benefit from the incorporation of images and diagrams. Because you are describing so much, a visual aid will help you immensely and also assist in retaining the attention of the reader throughout the entirety of the piece. Also, I see that you have deviated from the recommended headings. This may be a good idea to individualise your project- but make sure all topics are covered. I think it’s a good start considering you only have two team members, and I’m sure you will be able to pull it all together by the time it is due.
--[[User:Z8600021|Mark Hill] Fairly good peer reviews. You have both general and specific comments in your feedback as well as suggestions for improvement. A little too overboard with your positive comments. (8/10)
Lab Attendance week 11
--[[User:Z8600021|Mark Hill] Where is your summary? (0/5)
Lab attendance week 12
Stem cells usage in the fabrication of bioartificial organs is increasingly becoming a trending area of medical research due to its potential use as an alternative to live organ transplants, which have issues in donor scarcity and host rejection. This paper concerns the differentiation of induced pluripotent stem cells (iPSCs) to produce the phenotypes of lung epithelial cells, specifically the expression of Nkx2.1+lung/thyroid progenitor cells. A major issue regarding respiratory stem cell applications is that normal pulmonary function usually exists at very low oxygen tensions of 1-5%, whilst in-vitro differentiations of iPSC’s generally occur at room-air oxygen tension, which is about 20%. This study strives to identify the variances in stem cell quality when differentiation was carried out at oxygen tensions of 5% and 20% respectively. Briefly, this was done by testing the expression of Nkx2.1, a transcription factor which is involved in early lung development in the embryo and subsequently acts as a marker when determining the success of stem cell differentiation to lung tissue. Other transcription factors involved in early organogenesis such as Foxa2 and Sox17 were also tested.
To briefly outline the methods utilized in this study- pluripotent stem cells were obtained from mouse embryonic fibroblasts and were routinely maintained on an antibiotic inactivated basic murine stem cell medium. The oxygen tension differences were able to be created via a cell culture incubator. After the stem cells were cultured, they were generated into endodermal lung progenitors which utilized a step-wise differentiation protocol, performed at oxygen tensions of 5% and 20% respectively. The stem cell-derived lung progenitors were then left to mature for 10 days, and then tested by immunocytochemistry for differences in transcription factor expression based on the oxygen tensions they were exposed to.
Overall the results of the study found a positive result for stem cells exposed to lower oxygen tensions. It was observed that embryoid bodies (the first step in a differentiation protocol for pluripotent stem cells) were more efficiently formed at oxygen tensions of 5% compared to oxygen tensions of 20%. Furthermore, when comparing the inductions of the stem cells into the definitive endoderm it was found that there was a much higher level of the transcription factors involved in lung cell development at oxygen tensions of 5% compared to 20%. The transcription factors tested were Nkx2.1, Foxa2 and Sox17- all of which had elevated levels at a lower oxygen tension environment. Thus, we can conclude based on this study that stem cell differentiations are actually more effective at lower oxygen tensions- a result which is fortuitous when looking to develop stem cell cultures to be used in pulmonary environments, which naturally have lower oxygen tensions.
--[[User:Z8600021|Mark Hill] Good could have been briefer. (4/5)