Sometimes someone comes along and shows me a study that pushes the endeavor a little further and that is the type of help I hope we as the researchers can get from the readers.
For most of the stuff that the readers show me or direct me to, I look at the material to see if there is anything useful that I and other researchers can use. I am very grateful to the person who showed me the study “Engineering growing tissues” by Eben Alsberg. From just a quick Google search on Dr. Alsberg, it seems that he is cased in the Biomedical Engineering Department at Case Western University, which I remember had a very strong engineering school. I would look through his profile and research to see what other papers he has written about tissue engineering over the years. There are some interesting papers he has been a coauthor to, including…
- “Spatiotemporal regulation of chondrogenic differentiation with controlled delivery of TGF-β1 from gelatin microspheres in mesenchymal stem cell aggregates”
- “Stromal-cell-derived factor (SDF) 1-alpha in combination with BMP-2 and TGF-β1 induces site-directed cell homing and osteogenic and chondrogenic differentiation for tissue engineering without the requirement for cell seeding”
- “Engineered cartilage via self-assembled hMSC sheets with incorporated biodegradable gelatin microspheres releasing chondrogenic growth factor”
- “Controlled and sustained gene delivery from injectable, porous PLGA scaffolds”
- “Chondrogenic differentiation of human mesenchymal stem cell aggregates via controlled release of TGF-b1 from incorporated polymer microspheres.”
These studies are the most interesting to me but the last is is particularly attractive to read through. I guess I will get to it in another day.
It is interesting that he does a lot of research in the biomedical application of electrospinning, since I have stated that electrospinning is one of the more likely ways that human cartilage can be grown rather easily for growth plate re-implantation. I wrote a post about this idea entitled “Increase Height And Grow Taller Through Bioprinting And Electrospinning“. At this point, I will move away from Dr. Alsberg research and look at what other university tissue engineering and biomedical engineer professors have been doing research on.
The 2nd study that he would refer me to showed that there has been even more ways and methods that researchers have done in recent years that allowed for growth plate regeneration.
IGF-I RELEASING PLGA SCAFFOLDS FOR GROWTH PLATE REGENERATION
Sharath Kumar Chinnakavanam Sundararaj – Master’s Theses – May, 5th 2010 – UKnowledge
University of Kentucky, sharath.sundararaj@uky.edu
Abstract
Growth plate is a highly organized cartilaginous tissue found at the end of long bones and is responsible for longitudinal growth of the bones. Growth plate fracture leads to retarded growth and unequal limb length, which might have a lifelong effect on a person’s physical stature. This research is a tissue engineering approach for the treatment of growth plate injury. Insulin-like growth factor I (IGF-I), which can stimulate cartilage formation, was encapsulated within PLGA microspheres that were then used to form porous scaffolds. The release profile of the IGF-I from the PLGA scaffold showed a biphasic release pattern. In vitro studies were done by seeding rat bone marrow cells (BMCs) on the top of IGF-I encapsulated PLGA scaffolds, and the results showed an increase in cell multiplication and glycosaminoglycan content. The final in vivo studies were conducted by creating growth plate injury and implanting scaffolds in the tibiae of the New-Zealand white rabbits. Histological analysis of tissue sections showed regeneration of cartilage, albeit with disorganized structure, at the site of implantation of IGF-I encapsulated scaffolds. This work will be a significant step towards tissue engineering of growth plate cartilage.
KEYWORDS: PLGA, Tissue engineering, growth plate, drug delivery and IGF-I
Analysis #1: I have reviewed multiple Ph. D theses before and it was very mentally tiring work to read through what are usually 200+ pages of scientific data and charts. This Master’s Theses maybe only 70 pages but it still will take a lot of work to get through.
The overall theses is not to actually grow a growth plate from scratch using a seed from an autologous explant, but it is more towards trying to grow a similar physeal cartilage like the growth plate in the fractured area when the growth plate experiences a type of injury that might cause something like a bony bridge.
- IGF-1 was somehow put inside/encapsulated in microspheres that are made out of PLGA.
- The microspheres were used to make into porous scaffolds.
- The IGF-1 will eventually get released from the PLGA microspheres as either the microspheres and/or the scaffold starts to disintegrate
- The way that the IGF-1 is released is shown to have two phases.
The studies to look at the release profile and release characteristics of the IGF-1 was done AT FIRST in in-vitro environment.
- Some rat marrow cells were taken out from the actual lab animal (probably using a similar invasive method as a biopsy)
- The cells were put on top of the scaffold which already has the IGF-1 inside.
- The result is that there was an increase in glycosaminoglycan content and cell multiplication
The studies were then done AT THE END in vivo
- Some lab rabbits, of the New Zealand type was taken.
- The growth plate in their tibia was broken to create an injury, which left a defect or distracted area where intact, continuous growth plates used to be.
- The scaffold with the IGF-1 inside was put in the area of empty space left by the growth plate
- Histological analysis (which is just taking a microscope and looking at the tissue being analyzed to see the cell structure, cell number) of tissue sections showed regeneration of cartilage.
- The growth plate cartilage that was created however showed a disorganized structure
What is PLGA? – From Wikipedia – poly(lactic-co-glycolic acid) is a copolymer which is used in a host of Food and Drug Administration (FDA) approved therapeutic devices, owing to its biodegradability and biocompatibility
What is a Copolymer? – From Wikipedia – A heteropolymer or copolymer is a polymer derived from two (or more) monomeric species, as opposed to a homopolymer where only one monomer is used.
What is a Polymer? – From Wikipedia – is a large molecule composed of many subunits, known as monomers… Polymers range from familiar synthetic plastics such as polystyrene (of styrofoam) to natural biopolymerssuch as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many monomers
What is a Monomer? – From Wikipedia – refers to the organic molecules which form synthetic polymers, such as, for example, vinyl chloride, which is used to produce the polymerpolyvinyl chloride (PVC).
So what was the overall message of the Thesis?
(Page 2) Tissue engineering of cartilage is gaining heavy importance in the field of tissue engineering. But most of the research till now is mainly focused on the regeneration of articular cartilage and very little progress has been made in tissue engineering of growth plate. This work was aimed at providing a significant contribution towards tissue engineering of growth plate.
We hypothesized that microencapsulation of IGF-I in PLGA would be an appropriate growth factor delivery system for regeneration of growth plate cartilage both in vitro and in vivo.
THe 5th section of this Master’s Theses is on the Discussion. It is broken up into certain sections
- Release profile of protein encapsulated scaffolds degraded in PBS
- Release profile of protein adsorbed and protein encapsulated scaffolds
- Release profile of protein-encapsulated scaffolds degraded in cell culture medium
- Release profile of protein-encapsulated scaffolds degraded in cell culture medium
- along with macrophages
2nd part: Degradation of PLGA scaffolds
- Mass loss of scaffolds degraded in PBS
- Mass loss of scaffolds degraded in cell culture medium
3rd part: In vitro cell studies
- Seeding the cells with fibrin glue
- Confocal imaging of BMC-seeded scaffolds
- Analysis of GAG content from the BMCs
4th part: In vivo studies
- Scaffold used in the animal surgery
- Radiographic images
- Histology
Last section #6: CONCLUSION
The main aim of this research was to develop a biodegradable drug delivery device for the treatment of the growth plate injury. The regeneration of the growth plate cartilage in the site of injury has confirmed that the IGF-I was successfully released from the porous PLGA scaffold and induced the formation of chondrocytes and extracellular matrix. The release studies showed that microencapsulation of IGF-I was a suitable method for storage of the drug within the scaffold that is going to be released. The release studies and the in vitro cell studies confirmed that the device was capable of releasing the drug in a required pattern and bioactive state. The IGF-I encapsulated porous PLGA scaffold implanted in the rabbit model for treatment of growth plate injury has successfully regenerated cartilage at the site of injury, even though it was not effective in correcting the defect in the bone angle that was caused due to the injury. The results of this research has shown that using porous PLGA scaffolds with IGF-I encapsulated in the form of microspheres will serve as an appropriate drug delivery system for the cartilage regeneration. This work will be a significant step forward in the tissue engineering of growth plate cartilage.
Analysis #2
It seems that as long as there is some growth plate left in the animal, regeneration is possible using just a scaffold of the right type (this time the right material is PLGA) and some IGF-1. The IGF-1 did result in cartilage being regenerated but it did not manage to fix the defect in the bone angle that was originally induced to create the bone injury.
Me and the other researchers have found this type of thing before, and this theses shows that if some growth plates is missing, we can recreated it. The histological analysis seems to show that the chondrocytes that were in the newly created cartilage were not organized or columnar stacked like how they should be to have the hypertrophic zone which would lead to maximum longitudinal growth rates.
This suggests that while IGF-1 is affective alone in a scaffold, there might be some growth factors which might be better to towards forming chondrocytes that are more organized and in the right position for better growth chances.
Something to realize is that if there is NO growth plate cartilage left, then this method would not work There has to be at least some cartilage left. This method is similar to what we see in techniques which result in articular cartilage layer thickening where some articular cartilage is regenerated on the top surface to decrease osteoarthritis and cartilage degeneration associated with old age.
The problem is that if we are talking about adult human with absolutely no cartilage to start with, then wee need more than just a scaffold and a growth factor as a stimuli.
This study/theses was useful and will be used in future posts to show that it is possible to heal over defects in growth plate cartilage with new cartilage. However it is not enough for people with absolutely no physeal cartilage to start with.