MIT Biomedical Engineering Society


Vol. 4 No. 3 November 2005 National Conference Grad School Primer Langer Interview Research: hES Research: Microfluidics Photo Gallery Student Research Printable Version	The BioTECH Quarterly MIT Research Highlight Cultivation of Human Embryonic Stem Cells without the Embryoid Body Step Enhances Osteogenesis in vitro By Dr. Jeff Kap, POSTDOCTORAL FELLOW, Albert Kwon ’08, and Hannah Seong ’08 Human embryonic stem cells (hESC) offer a potentially unlimited supply of cells that may be driven down specific lineages to give rise to all cell types in the body. Recently there has been great interest in exploring the osteogenic (bone growth) potential of hESCs, and to date two methods have been examined. In one method, osteogenic cells are derived from 3-dimenstional cell aggregates called embryoid bodies (EB) (Fig. 1A). EBs mimic the structure of the developing embryo and recapitulate many of the stages involved during its differentiation including the emergence of multiple cell types. As an engineer it is very difficult to exhibit control over the multiple cell-cell and cell-matrix contacts that are inherent in this system. An alternative method that has been tested but not well characterized avoids EBs through the immediate separation of hESC colonies into single cells which are then plated directly into a cell-adhesive culture dish (Fig. 1B). Using this method, one can presumably exhibit better control over the cell microenvironment and thus obtain more pure populations of progenitor cells. We have recently found that by omitting the embryoid body step, a significant increase in the number of bone nodules (which correlates with the number of osteoprogenitor cells) can be more rapidly achieved. Specifically, 7 times more bones nodules formed when the embryoid body step was omitted (Fig. 2). In addition, we found that these bone nodules formed after 2 weeks compared to after 4 weeks in cultures derived from EB. Furthermore, we found that regardless of the culture protocol, osteogenic cultures of hESC produced many of the hallmarks of de novo bone formation, including a mineralized collagenous matrix and an underlying cement line matrix (the cement line matrix is formed in the body during bone remodeling and serves to “glue” the old and new bone surfaces together). Taken together, the results indicate that omission of the embryoid body step during the differentiation of hESC into osteogenic cells can be used to rapidly increase osteogenic cell numbers which may be useful in applications such as tissue engineering or cell therapy. In addition, these results might be useful in other cell systems where high numbers of particular cell types are required. This research was done in the Langer Research Laboratory, with Albert Kwon ’08 and Hannah Seong ’08 involved as UROP students and Dr. Jeff Karp, Dr. Lino Ferreira, and Dr. Ali Khademhosseini serving as mentors. Figure 1. After hESC were cultured on mouse embryonic fibroblast feeder layers for 4 days, cell aggregates were removed with collagenase IV and either (A) suspended as EB for 5 days and then plated as a single cell suspension or (B) directly placed onto tissue culture petri dishes for 1 day followed by plating as a single cell suspension. Figure 2. Cells grown from EB produced (5.1 +- 2.4) bone nodules (stained for von Kossa and alkaline phosphatase). In comparison, cells grown without EB (insert) produced 39.1 +- 17.8 bone nodules. Albert and Hannah share about their research experience below: By Albert Kwon ’08, BIOLOGY, and Hannah Seong ’08, CHEMICAL ENGINEERING This research experience was an incredible opportunity for us to gain research skills and to learn about the area of tissue engineering and stem cell research. This was our first UROP experience at MIT that we began during our freshman year under the mentorship of Dr. Jeff Karp, who detailed the motivation for this project and conveyed all the necessary background information. Throughout this experience we learned aseptic cell culture techniques in addition to methods for performing various immunocytochemical and protein assays. As the project progressed, we observed how Dr. Karp and colleagues interacted to address various challenges that arose. We feel very privileged not only to have observed these interactions but also to have been given the opportunity to participate by contributing our opinions and ideas. We have learned a tremendous amount from this UROP project, which in turn has already had a great influence on our short and long term academic and career plans. It is truly incredible to be part of this project and to have been involved from the very beginning. Our work was recently accepted for publication in the journal Stem Cells (published online on October 27). We feel that stem cells-based tissue engineering has great potential and look forward to help further advance this field to clinical practice.
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The BioTECH Quarterly

MIT Research Highlight

Cultivation of Human Embryonic Stem Cells without the Embryoid Body Step Enhances Osteogenesis in vitro

By Dr. Jeff Kap, POSTDOCTORAL FELLOW, Albert Kwon ’08, and Hannah Seong ’08

Human embryonic stem cells (hESC) offer a potentially unlimited supply of cells that may be driven down specific lineages to give rise to all cell types in the body. Recently there has been great interest in exploring the osteogenic (bone growth) potential of hESCs, and to date two methods have been examined.

In one method, osteogenic cells are derived from 3-dimenstional cell aggregates called embryoid bodies (EB) (Fig. 1A). EBs mimic the structure of the developing embryo and recapitulate many of the stages involved during its differentiation including the emergence of multiple cell types. As an engineer it is very difficult to exhibit control over the multiple cell-cell and cell-matrix contacts that are inherent in this system.

An alternative method that has been tested but not well characterized avoids EBs through the immediate separation of hESC colonies into single cells which are then plated directly into a cell-adhesive culture dish (Fig. 1B). Using this method, one can presumably exhibit better control over the cell microenvironment and thus obtain more pure populations of progenitor cells.

We have recently found that by omitting the embryoid body step, a significant increase in the number of bone nodules (which correlates with the number of osteoprogenitor cells) can be more rapidly achieved. Specifically, 7 times more bones nodules formed when the embryoid body step was omitted (Fig. 2).

In addition, we found that these bone nodules formed after 2 weeks compared to after 4 weeks in cultures derived from EB. Furthermore, we found that regardless of the culture protocol, osteogenic cultures of hESC produced many of the hallmarks of de novo bone formation, including a mineralized collagenous matrix and an underlying cement line matrix (the cement line matrix is formed in the body during bone remodeling and serves to “glue” the old and new bone surfaces together).

Taken together, the results indicate that omission of the embryoid body step during the differentiation of hESC into osteogenic cells can be used to rapidly increase osteogenic cell numbers which may be useful in applications such as tissue engineering or cell therapy. In addition, these results might be useful in other cell systems where high numbers of particular cell types are required.

This research was done in the Langer Research Laboratory, with Albert Kwon ’08 and Hannah Seong ’08 involved as UROP students and Dr. Jeff Karp, Dr. Lino Ferreira, and Dr. Ali Khademhosseini serving as mentors.

Figure 1. After hESC were cultured on mouse embryonic fibroblast feeder layers for 4 days, cell aggregates were removed with collagenase IV and either (A) suspended as EB for 5 days and then plated as a single cell suspension or (B) directly placed onto tissue culture petri dishes for 1 day followed by plating as a single cell suspension.

Figure 2. Cells grown from EB produced (5.1 +- 2.4) bone nodules (stained for von Kossa and alkaline phosphatase). In comparison, cells grown without EB (insert) produced 39.1 +- 17.8 bone nodules.

Albert and Hannah share about their research experience below:

By Albert Kwon ’08, BIOLOGY, and Hannah Seong ’08, CHEMICAL ENGINEERING

This research experience was an incredible opportunity for us to gain research skills and to learn about the area of tissue engineering and stem cell research. This was our first UROP experience at MIT that we began during our freshman year under the mentorship of Dr. Jeff Karp, who detailed the motivation for this project and conveyed all the necessary background information.

Throughout this experience we learned aseptic cell culture techniques in addition to methods for performing various immunocytochemical and protein assays. As the project progressed, we observed how Dr. Karp and colleagues interacted to address various challenges that arose. We feel very privileged not only to have observed these interactions but also to have been given the opportunity to participate by contributing our opinions and ideas.

We have learned a tremendous amount from this UROP project, which in turn has already had a great influence on our short and long term academic and career plans. It is truly incredible to be part of this project and to have been involved from the very beginning. Our work was recently accepted for publication in the journal Stem Cells (published online on October 27). We feel that stem cells-based tissue engineering has great potential and look forward to help further advance this field to clinical practice.