Dental stem cells and replacement teeth

Question 1

where are the stem cells found in the tooth?

Answer 1

many places in the stem cells- pulp, SCAP cels at the root, dental follicle around the tooth germ, from salivary glands

Question 2

what are SHED?

Answer 2

stem cells from human exfoliated dentition

Question 3

are the stem cells from different parts in the teeth different?

Answer 3

yes

Question 4

how can you look at the differences in the types of stem cells from the mouth?

Answer 4

look at the mineral to matrix ratios

Question 5

what can dental stem cells be differentiated into?

Answer 5

• osteoblasts
• 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

Question 6

why is regenerating the pulp clinically interesting?

Answer 6

• once infected it can’t be treated and the tooth has to be removed.

Question 7

what are the two regenerative strategies in endodontics?

Answer 7

• 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

Question 8

what does de novo mean?

Answer 8

it means from afresh- starting from scratch

Question 9

how was teeth pulp grown de novo?

Answer 9

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

Question 10

what does PDL mean?

Answer 10

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

Question 11

what is a cell based therapy for PDL regeneration?

Answer 11

• 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

Question 12

describe a study which used a combination of different types of stem cell together in order to produce a regenerated tooth

Answer 12

• 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..

Question 13

from what tooth is a good source of all of the teeth stem cells?

Answer 13

the wisdom tooth root because they are often still developing a root

Question 14

what does engineering cell sheets mean and how was it used?

Answer 14

A conceptually simpler approach to periodontal regeneration methods involves engineered cell sheets to facilitate human periodontal ligament (HPDL) cell transplantation [35]. 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

Question 15

how can you create personalised regenerative treatment??~

Answer 15

…

Question 16

what are the processes of teeth development?

Answer 16

• 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

Question 17

how can yo use epithelium and mesenchymal cells to produce teeth in vitro?

Answer 17

• 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

Question 18

how can you look at the similarities between tooth development tin the mouse and the human

Answer 18

• 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

Question 19

how has the development of human teeth cells been looked at in vivo?

Answer 19

• 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.

Question 20

how have they tried to speed up the development of human teeth cells?

Answer 20

• 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.)

Question 21

why is the tooth a perfect source of stem cells?

Answer 21

• different mesenchymal and or epithelial stem cells derived from tooth/oral tissues.
• they are very accessible

Question 22

how are teeth formed ?

Answer 22

• via the interactions between oral epithelial cells and cranial near crest cell derived mesenchymal cells

Question 23

what do the epithelial cells give rise to?

Answer 23

• the enamel forming ameloblasts

Question 24

what has implicated dental pulp cells in neuronal regeneration?

Answer 24

DPSCs differentiate into functionally active neurons, and implanted DPSCs induce endogenous axon guidance, suggesting their potential as cellular therapy

Question 25

what is a key difference between human exfoliated deciduous teeth and pulp stem cells?

Answer 25

the first has a higher proliferation rate and osteoindctive capacity in vivo

Question 26

how can SHED cells been used for neurodegenerative disorders?

Answer 26

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.

Question 27

why are DPSCs as a clinica treatment preferable to SHEDs?

Answer 27

• SHEDs would need to be isolated during childhood but DPSCs can be taken from the adult

Question 28

what can SCAPs differentiate into?

Answer 28

SCAP have the capacity to differentiate into odontoblasts and adipocytes

Question 29

how can SCAPs and PDLSCs be used together for clinical regeneration?

Answer 29

• 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.

Question 30

where could SCAPs be isolated from?

Answer 30

wisdom teeth

Question 31

what are the outstanding question in terms of PDL regeneration?

Answer 31

the extent to which any reconstituted periodontium can maintain integrity and function during mastication over long periods of time.

Question 32

what do some people claim about pulp regeneration protocol?

Answer 32

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.

Question 33

what is the problem with the current procedure of teeth replacement?

Answer 33

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.

Question 34

what is the major challenge and requirement for tooth regeneration?

Answer 34

forming a biological root.

Question 35

where does the potential for odontogenic potential lie?

Answer 35

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

Question 36

describe an experiment which demonstrated that non- dental mesenchyme could be induced to form dental tissue with the right epithelium

Answer 36

it was shown that expanded adult bone marrow stromal cells would form teeth in vitro when combined with inductive embryonic oral epithelium

Question 37

describe the process of tooth regeneration by cell re-aggregation

Answer 37

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

Question 38

what is the main hindrance to regenerating teeth at the moment

Answer 38

No sources of epithelial cells capable of inducing odontogenesis have been identified to date, other than the endogenous dental epithelium of early stage embryos.

Question 39

describe the most promising experiment in terms of finding a source of epithelium

Answer 39

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

Question 40

why is growing the root and not the crown important?

Answer 40

the crown can be easily made using enamel

Question 41

why is finding suitable mesenchyme less troublesome, what can be used?

Answer 41

• non dental mesenchyme can be induced by dental epithelium - adult bone marrow stromal cells

Question 42

what study has shown that epithelium and mesenchyme can be used together to induce teeth but what were the issues with this

Answer 42

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.

Question 43

what was the study that shown that human adult epithelial cells could be induced to form teeth my mouse embryonic dental mesnehcyme?

Answer 43

• 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

Question 44

what stem cell can be used for bone regeneration ?

Answer 44

DPSCs

Question 45

describe how DPSCs can be used in bone regeneration and why they are a good choice

Answer 45

CD34+ DPSCs transplanted in the subcutaneous tissue of rats form a substantial number of bone nodules [49]. Due to the superior efficiency in producing bone chips compared with BMSCs, DPSCs are considered one of the best candidates for bone regeneration

Question 46

describe how dental stem cells have been used to treat myocardial infarction

Answer 46

used human dental pulp stem cells (hDPSCs) in a rat myocardial infarction model in 2008, reporting an increase in the number of vessels and decrease in the size of infarct, concluding that hDPSCs secrete multiple proangiogenic apoptotic factors including VEGF