Judges’ Queries and Presenter’s Replies

  • May 20, 2013 | 03:14 p.m.

    Hello, could you clarify your goals: are you working on creating or improving bio-materials to mimic tissues? Is your goal to compare the properties of hydrogel and GAGs?
    JB

  • Icon for: Jennifer Lei

    Jennifer Lei

    Presenter
    May 21, 2013 | 11:25 a.m.

    That is a great question! In our lab, we are able to utilize biomaterials and stem cells in a versatile manner. The goals on this poster are 2-fold, 1) We show that biomaterials can be utilized to better understand mesenchymal stem cell/adipocyte/osteoblast interactions in a disease state (i.e. diabetes), while not necessarily mimicking tissue, and 2) We show that mesenchymal stem cells can be manipulated (i.e. forced into aggregates) and modified with therapeutic agents (i.e. GAGs) as a cell-based therapy for different pathologies.

    Coming back to your specific question, we are not looking to compare the properties of hydrogels and GAGs, rather we utilize both for different orthopedic applications.

  • May 21, 2013 | 10:54 a.m.

    Nice work, The 10 min exposure to UV source, will it not change the cell characteristics, especially DNA damage or activation of certain transcription factors?
    b) What is the ratio of cell density to the hydrogel and photo initiator?
    c) Have you performed viability and proliferation studies on MSC spheroids coated with heparin?

  • Icon for: Jennifer Lei

    Jennifer Lei

    Presenter
    May 21, 2013 | 11:42 a.m.

    Thanks for the questions! It has been found in many experiments that the UV light for such a short exposure time does not negatively impact cell viability. The part of the polymerization process that is most harmful to the cells is the free radicals generated from the photoinitiator. To ensure that we do not seriously decrease cell viability, we use a very low concentration (0.05%) of photoinitiator and keep our exposure time to 10 minutes or less. We have found that we usually achieve 75-90% viability, which is standard in the field.
    b) Our cell density is usually about 100 million cells/mL and our photoinitiator, like I mentioned, is 0.05% of the precursor hydrogel solution. For instance, in a 100 uL hydrogel precursor solution, we have 1 million cells and 0.05 uL of the photoinitiator.
    c) We have performed viability studies on the heparin-coated MSC spheroids and we’ve seen that the cells are not negatively affected by this coating treatment and that the viability of the coated cells are comparable to the viability of the non-coated cells. We have not performed proliferation studies yet because in our experience, we have seen that the MSCs do not proliferate once aggregated into spheroid form unless treated with specific growth factors.

  • May 21, 2013 | 11:37 a.m.

    What orthopedic applications are you thinking of for your technology?

  • Icon for: Torri Rinker

    Torri Rinker

    Co-Presenter
    May 21, 2013 | 11:43 a.m.

    For our hydrogel-based platform to study cellular communication, we have studied diabetes, as you can see in the poster, and we are considering another study involving rheumatoid arthritis or another disease involving the joint.

    For our spheroid culture, we are looking at cell-based therapies that can treat cartilage or tendon defects.

  • Icon for: Zhaomin Yang

    Zhaomin Yang

    Judge
    May 21, 2013 | 08:17 p.m.

    What were normal and high glucose conditions and why was the effect of glucose examined?

  • Icon for: Torri Rinker

    Torri Rinker

    Co-Presenter
    May 21, 2013 | 08:46 p.m.

    We were interested in understanding more about cellular interactions in a disease state, specifically diabetes. Thus, since a consequence of diabetes is hyperglycemia (high levels of glucose), we chose to use both normal and high glucose levels for our experiments. The actual levels were determined based on previous literature and was either 1 g/L (normal) or 4 g/L (high).

  • May 21, 2013 | 08:40 p.m.

    Hi Heather,
    Interesting work and great explaination of biomaterials. Would you please explain Figure 1? It looks like you using a vital dye, and also staining nuclei Fig 1D. How does interpretation of E and F support your conclusion, that heparin coating does not compromise viability?

  • Icon for: Jennifer Lei

    Jennifer Lei

    Presenter
    May 22, 2013 | 12:11 a.m.

    Thank you for your question! Figure 1 characterizes the heparin coating on our MSC spheroids. The heparin used to coat the spheroids is tagged with Alexa Fluor 633 and does not interfere with the LIVE/DEAD imaging. Figures 1A and 1C represent LIVE/DEAD staining for the negative control and the heparin coated spheroids, respectively. Figures 1B and 1D image the actual heparin coating (not nuclei) through the AlexFluor tag for the two groups mentioned above. Figures 1E and 1F are also imaging the heparin-AlexaFluor coatings on the MSC spheroids, however, in a red channel and at the different coating concentrations of 5mg/mL and 10mg/mL, respectively. The vital dye (LIVE/DEAD) seen in 1A and 1C show that the coating does not compromise viability.

  • Further posting is closed as the competition has ended.

Presentation Discussion

  • Icon for: Joni Falk

    Joni Falk

    Faculty
    May 23, 2013 | 04:33 p.m.

    Very much enjoyed this inside look into the methodical work that goes on inside your lab. Thanks for sharing it!

  • Icon for: Jennifer Lei

    Jennifer Lei

    Presenter
    May 24, 2013 | 02:24 p.m.

    Thanks!

  • Small default profile

    Hsiu-mei Liao

    Guest
    May 24, 2013 | 01:19 a.m.

    Good job, Jennifer.

  • Icon for: Jennifer Lei

    Jennifer Lei

    Presenter
    May 24, 2013 | 02:24 p.m.

    Thank you!

  • Further posting is closed as the competition has ended.

  1. Jennifer Lei
  2. http://www.igert.org/profiles/4512
  3. Graduate Student
  4. Presenter’s IGERT
  5. Georgia Institute of Technology
  1. Torri Rinker
  2. http://www.igert.org/profiles/4914
  3. Graduate Student
  4. Presenter’s IGERT
  5. Georgia Institute of Technology

Orthopedic Applications for Human Mesenchymal Stem Cells Employing Advanced Biomaterials

Recently, stem cells have gained significant attention due to their regenerative potential to improve tissue healing and their capacity to differentiate into a variety of tissue types. Mesenchymal stem cells (MSCs) are a unique type of stem cell because they are found in adult tissues, making it possible for scientists to use a patient’s own MSCs to repair an injury. While such therapies have great promise, much remains unknown regarding stem cells interaction in the body. Thus, both biologist and engineers have developed methods to study stem cells both in the lab and in living organisms. We present two different manners in which MSCs, in conjunction with advanced biomaterials, can be used in orthopedic tissue engineering applications. First, a water-based biomaterial called a hydrogel is employed as a matrix in which MSCs can interact with adipoctyes (adult fat cells) and osteoblasts (adult bone cells), two cell types two cell types into which MSCs can differentiate. By modeling a diabetes pathology, we have learned how MSCs behave under disease conditions, which advances our understanding of how these cells can be used in regenerative medicine. Next, MSCs are aggregated and modified with negatively charged glycosaminoglycans (GAGs) that sequester and release different molecules. MSCs in aggregate form have therapeutic potential because they have anti-inflammatory effects. In addition to using MSCs as a regenerative tool, by controlling modification with different GAGs, the release of beneficial factors can be controlled and sustained over time at a potential injury site to facilitate healing and repair.