Flashcards in Dental stem cells and replacement teeth Deck (46):
where are the stem cells found in the tooth?
many places in the stem cells- pulp, SCAP cels at the root, dental follicle around the tooth germ, from salivary glands
what are SHED?
stem cells from human exfoliated dentition
are the stem cells from different parts in the teeth different?
how can you look at the differences in the types of stem cells from the mouth?
look at the mineral to matrix ratios
what can dental stem cells be differentiated into?
- muscles: DMD and heart valves
- hey originate from neural crest cells so can be used in neural regeneration
- oral muscosa epithelial cells have been used in corneal reconstruction
why is regenerating the pulp clinically interesting?
- once infected it can't be treated and the tooth has to be removed.
what are the two regenerative strategies in endodontics?
- is it better to work from inside the body by promoting wound healing or is it better to work 'outside' and create dental pulp which can be implanted
what does de novo mean?
it means from afresh- starting from scratch
how was teeth pulp grown de novo?
DPSC and SCAP isolated from the human third molars were seeded onto a poly-D,L-lactide/glycolide scaffold and inserted into the canal space of root fragments, followed by subcutaneous transplantation into SCID mice. Subsequent histological analysis of the tooth fragments 3–4 months after surgery indicated that the root canal space was completely filled with pulp-like tissue with well established vascularization. Moreover, a continuous layer of mineralized tissue resembling dentine was deposited on the existing dentinal walls of the canal
what does PDL mean?
peridontal ligament - gives elastic and mechanical support of the tooth. has collagen fibres and allows the teeth to move a bit in the cushion. If you have an implant then you miss this. It is important because if it gets inflamed then this results in gum disease
what is a cell based therapy for PDL regeneration?
- accelerate periodontal regeneration through two primary mechanisms:
- to use cells are carriers to deliver growth or cellular signals
- to provide cells that are able to differentiate to multiple cell types to promote regeneration
describe a study which used a combination of different types of stem cell together in order to produce a regenerated tooth
- using different types of set cells from oral cavity and biomaterial
- SCAP cells at the tip of the root, these cells have been cloned and used with the PDL cells at the ligament (SCAP cells are easily accessible)
- The SCAP cells have been cloned on a scaffold which is shaped as a root
- The pdl stem cells have been grown in a gel foam structure which grows around the scaffold
- these were implanted together as a construct into the
pig model and after 3 months they saw that it was well integrated dentine and periodontal ligament was formed..
from what tooth is a good source of all of the teeth stem cells?
the wisdom tooth root because they are often still developing a root
what does engineering cell sheets mean and how was it used?
A conceptually simpler approach to periodontal regeneration methods involves engineered cell sheets to facilitate human periodontal ligament (HPDL) cell transplantation . Periodontal ligament cells isolated from a human third molar tooth were cultured on poly(N-isopropylacryl-amide) (PIPAAm)-grafted dishes that induce spontaneous detachment of the cells as viable cell sheets upon low temperature treatment. HPDL cells sheets were implanted into athymic rats that had the periodontium and cementum removed from their first molars. Fibril anchoring resembling native periodontal ligament fibres, together with an acellular cementum-like layer, was observed, indicating that this technique could be applicable to future periodontal regeneration. Although promising, this approach does not take into account any replacement of bone that might be required.
- also done in dogs
how can you create personalised regenerative treatment??~
what are the processes of teeth development?
- induction: thinkening of the epithelium
- then the mesenchyme responds and drives the development
- morphogenesis in which there is the bud state, cap stage, bell stage.
then tooth eruption
how can yo use epithelium and mesenchymal cells to produce teeth in vitro?
- you mix the epithelial and mesnehcymal cells together
after 9 days you will see toothlets
- you then implant them in SCID (immunocompromised mice) and and then laced in the kidney capsule because the teeth can't grow outside- needs to be in vivo
- after 2 weeks a mineralised structure is formed
- after 4 weeks a tooth was revealed
how can you look at the similarities between tooth development tin the mouse and the human
- the stages are the same but the timing is very different
- This is hard in terms of engineering
- the human takes 42 days to develop- 8 times slower
how has the development of human teeth cells been looked at in vivo?
- they waited until the embryo was 10 weeks old (what embryo) and then dissociated tooth germ cells epithelium and mesenchymal
- the same mixing of mesenchymal and epithelial cells and then cultured for 2 weeks and then implanted under the kidney capsule of a SCID mouse for 3 weeks.
how have they tried to speed up the development of human teeth cells?
- they looked at what happens when the use human adult epithelial cells from a scratch of the gum
- then use these in experiment with mouse cells to see if they can be accelerated and if human cells can respond to the mouse mesenchymal cells
- they cultured them together ad then pt them in the kidney capsule after 6 weeks and they found that the root and the tooth was present
- they needed t oproove that this tooth is due to the combination of the two types of cells so had t look of human cell markers showing that the epithelial cells were contributing to the root development
- had to prove that at the malessez cells were human and they were (because these are the cels that are normally coming from epithelial cells.)
why is the tooth a perfect source of stem cells?
- different mesenchymal and or epithelial stem cells derived from tooth/oral tissues.
- they are very accessible
how are teeth formed ?
- via the interactions between oral epithelial cells and cranial near crest cell derived mesenchymal cells
what do the epithelial cells give rise to?
- the enamel forming ameloblasts
what has implicated dental pulp cells in neuronal regeneration?
DPSCs differentiate into functionally active neurons, and implanted DPSCs induce endogenous axon guidance, suggesting their potential as cellular therapy
what is a key difference between human exfoliated deciduous teeth and pulp stem cells?
the first has a higher proliferation rate and osteoindctive capacity in vivo
how can SHED cells been used for neurodegenerative disorders?
Transplantation of SHED spheres into the striatum of parkinsonian rats partially improved the apomorphine evoked rotation of behavioural disorders. The results of this study indicate that SHED might be a useful source of postnatal stem cells for PD treatment.
why are DPSCs as a clinica treatment preferable to SHEDs?
- SHEDs would need to be isolated during childhood but DPSCs can be taken from the adult
what can SCAPs differentiate into?
SCAP have the capacity to differentiate into odontoblasts and adipocytes
how can SCAPs and PDLSCs be used together for clinical regeneration?
- they made a root scaffold called HA/TCP carrier which they filled wit human SCAP cells, then they wrapped this with PDLSC in a foam and transplanted
-by co-transplanting SCAP cells (to form a root) and PDLSC (to form a periodontal ligament) into tooth sockets of mini pigs, dentine and periodontal ligament was formed. These findings suggest that this population of cells, together with PDLSC, could be used to create a biological root that could be used in a similar way as a metal implant, by capping with an artificial dental crown.
where could SCAPs be isolated from?
what are the outstanding question in terms of PDL regeneration?
the extent to which any reconstituted periodontium can maintain integrity and function during mastication over long periods of time.
what do some people claim about pulp regeneration protocol?
Recent studies using genetically marked cells in mice have suggested that adding stem cells makes little difference to the extent to which an empty pulp cavity regenerates because the majority of cells are provided by the vasculature (Sharpe P.T, unpublished data). Stem cell pulp restoration might therefore not be a problem of providing exogenous stem cells but one of surgically ensuring that an adequate blood supply is maintained after pulp removal.
what is the problem with the current procedure of teeth replacement?
Because these implants attach directly to the bone without the PDL ‘shock absorber’, the forces of mastication are transmitted directly to the bone, which is one reason implants can fail.
what is the major challenge and requirement for tooth regeneration?
forming a biological root.
where does the potential for odontogenic potential lie?
dental epithelium- Dental epithelium from pre-bud stages can induce tooth formation when combined with nonodontogenic mesenchyme as long as the mesenchymal cells have stem cell-like properties in common with neural crest cells
describe an experiment which demonstrated that non- dental mesenchyme could be induced to form dental tissue with the right epithelium
it was shown that expanded adult bone marrow stromal cells would form teeth in vitro when combined with inductive embryonic oral epithelium
describe the process of tooth regeneration by cell re-aggregation
These experiments actually demonstrate the ability of dissociated cells to re-aggregate, however, rather than the bioengineering of whole teeth. The cells used are obtained from embryonic tooth primordia, many of which are required to produce one tooth. When tooth germs are dissociated and allowed to re-associate in an extracellular matrix (scaffold), they ‘sort out’ and re-aggregate to reform the tooth germs [48,51]. The re-aggregation produces multiple small ‘toothlets’, whose shape bears no resemblance to that of the scaffold used
what is the main hindrance to regenerating teeth at the moment
No sources of epithelial cells capable of inducing odontogenesis have been identified to date, other than the endogenous dental epithelium of early stage embryos.
describe the most promising experiment in terms of finding a source of epithelium
Postnatal oral mucosal epithelium might also offer some potential as a replacement for embryonic dental epithelium, because cells isolated from young animals, grown as cell sheets and re-associated with dental mesenchyme from E12.5 embryos, can give rise to tooth-like structures
why is growing the root and not the crown important?
the crown can be easily made using enamel
why is finding suitable mesenchyme less troublesome, what can be used?
- non dental mesenchyme can be induced by dental epithelium - adult bone marrow stromal cells
what study has shown that epithelium and mesenchyme can be used together to induce teeth but what were the issues with this
The first demonstration of the success of adult non-dental cells being used to form a biotooth came from recombinations between embryonic tooth epithelium and adult bone marrow stromal cells (Ohazama et al., 2004). Subsequent studies have largely focused on the use of embryonic cells, and although it is clear that embryonic tooth primordia cells can readily form teeth following dissociation into single-cell populations and subsequent recombination, such cell sources have little rel- evance for the development of a clinical therapy.
what was the study that shown that human adult epithelial cells could be induced to form teeth my mouse embryonic dental mesnehcyme?
- Human gingival epithelial cells
- the isolation and
culture of a population of human adult
epithelial cells from oral mucosa that,
when combined with mouse embryonic
tooth-inducing mesenchyme cells, form
teeth. The epithelial cell contribution to
these teeth includes ameloblast-like cells
and rests of Malassez
what stem cell can be used for bone regeneration ?
describe how DPSCs can be used in bone regeneration and why they are a good choice
CD34+ DPSCs transplanted in the subcutaneous tissue of rats form a substantial number of bone nodules . Due to the superior efficiency in producing bone chips compared with BMSCs, DPSCs are considered one of the best candidates for bone regeneration