Bone Marrow Stem Cells and Tissue Engineering Give a Woman a New Smile


Massive injuries to the face can cause bone loss and “tooth avulsion.” Medically speaking, avulsion simply refers to the detachment of a body structure from its normal location by means of surgery or trauma. Dental implants and help with lost teeth, but if the facial bone has suffered so much loss that you cannot place implants in them, then you are out of luck. Dental prostheses can help, but these do not always fit very well.

Darnell Kaigler and his group at the University of Michigan Center for Oral Health wanted to help a 45-year-old woman who had lost seven teeth and a good portion of her upper jaw bone (maxilla) as a result of massive trauma to the face. This poor lady had some dentures that did not fit well and a mouth that did not work well.

Bone can be grown from stem cells, but getting those stem cells to survive and do what you want them to do is the challenge of regenerative medicine. Therefore, Dr. Kraigler and his group used a new technique to help this young lady, and their results are reported in the December 2014 issue of the journal Stem Cells Translational Medicine.

First, Kraigler and his co-workers extracted bone marrow stem cells from a bone marrow aspiration that was taken from the upper part of the hip bone (the posterior crest of the ilium for those who are interested).  They used a product called ixmyelocel-T from Aastrom Biosciences in Ann Arbor , MI. This product is a patient-specific, expanded multicellular therapy, cell-processing system that selectively expands mesenchymal cells, monocytes and alternatively activated macrophages, up to several hundred times more than the number found in the patient’s bone marrow, while retaining many of the hematopoietic cells collected from only a small sample (50ml) of the patient’s bone marrow. Thus, the healing cells from the bone marrow are grown and made healthy, after which the cells were bagged and frozen for later use.

ixmyelocel-T

Then the patient was readied for the procedure by having the gum tissue cut and lifted as a flap of tissue (under anesthesia, or course). Then four holes were drilled into the bone and setting screws were inserted. This is an important procedure, because implanted stem cells will not survive unless they have blood vessels that can bring them oxygen and nutrients. By drilling these holes, the tissue responds by making new blood vessels. To this exposed surface, the bone marrow-derived stem cells were applied with a tricalcium phosphate (TCP). TCP is a salt that will induce mesenchymal stem cells to form bone. Once the TCP + stem cell mixture was applied to the gum, a collagen membrane was placed over it, and the gum was then sewn shut with sutures.

Cell transplantation procedure. Front view (A) and top view (B) of the initial clinical presentation showing severe hard and soft tissue alveolar ridge defects of the upper jaw. Following elevation of a full-thickness gingival flap, the images show front view (C) and top view (D) of the severely deficient alveolar ridge, clinically measuring a width of only 2–4 mm. Front view (E) and top view (F) of the placement of “tenting” screws in preparation of the bony site to receive the graft. Placement of the β-tricalcium phosphate (seeded with the cells 30 minutes prior to placement at room temperature) into the defect (G), with additional application of the cell suspension following placement of the graft in the recipient site (H). Placement of a resorbable barrier membrane (I) to stabilize and contain the graft within the recipient site, and top view (J) of primary closure of the flap.
Cell transplantation procedure. Front view (A) and top view (B) of the initial clinical presentation showing severe hard and soft tissue alveolar ridge defects of the upper jaw. Following elevation of a full-thickness gingival flap, the images show front view (C) and top view (D) of the severely deficient alveolar ridge, clinically measuring a width of only 2–4 mm. Front view (E) and top view (F) of the placement of “tenting” screws in preparation of the bony site to receive the graft. Placement of the β-tricalcium phosphate (seeded with the cells 30 minutes prior to placement at room temperature) into the defect (G), with additional application of the cell suspension following placement of the graft in the recipient site (H). Placement of a resorbable barrier membrane (I) to stabilize and contain the graft within the recipient site, and top view (J) of primary closure of the flap.

Four months later, the patient underwent a cone-beam computed tomography (CBCT) scan. The bone regrowth can be seen in the figure below.

Cone-beam computed tomography (CBCT) scans. CBCT scans were used to render three-dimensional reconstructions of the anterior segment of the upper jaw and cross-sectional (top view) radiographic images to show volumetric changes of the upper jaw at three time points. (A, B): The initial clinical presentation shows 75% jawbone width deficiency. (C, D): Immediately following cell therapy grafting, there is full restoration of jawbone width. (E, F): Images show 25% resorption of graft at 4 months and overall net 80% regeneration of the original ridge-width deficiency.
Cone-beam computed tomography (CBCT) scans. CBCT scans were used to render three-dimensional reconstructions of the anterior segment of the upper jaw and cross-sectional (top view) radiographic images to show volumetric changes of the upper jaw at three time points. (A, B): The initial clinical presentation shows 75% jawbone width deficiency. (C, D): Immediately following cell therapy grafting, there is full restoration of jawbone width. (E, F): Images show 25% resorption of graft at 4 months and overall net 80% regeneration of the original ridge-width deficiency.

According to the paper, there was an “80% regeneration of the original jawbone.”

Into this newly regenerated bone, permanent dental implants were placed. The results are shown below.

Complete oral rehabilitation. Clinical presentation of the patient prior to initiation of treatment (A) and following completed oral reconstruction (B). (C): Periapical radiographs of oral implants showing osseointegration of implants and stable bone levels at the time of placement, 6 months following placement, and 6 months following functional restoration and biomechanical loading of implants with a dental prosthesis.
Complete oral rehabilitation. Clinical presentation of the patient prior to initiation of treatment (A) and following completed oral reconstruction (B). (C): Periapical radiographs of oral implants showing osseointegration of implants and stable bone levels at the time of placement, 6 months following placement, and 6 months following functional restoration and biomechanical loading of implants with a dental prosthesis.

Pardon me, but permit me an unprofessional moment when I say that this is really cool.  Of course, this patient will need to be observed over the next several years to determine the longevity of her bone regeneration, but the initial result is certainly something to be excited about.

Tricalcium phosphate or TCP has been used to induce the bone-making activities of mesenchymal stem cells.  It has also been used in several animal studies as a delivery vehicle for mesenchymal stem cells (for example, see Rai B, et al., Biomaterials 2010, 31:79607970; Krebsbach PH, et al., Transplantation 1997, 63:10591069; Zhou J, et al., Biomaterials 2010, 31:11711179).  TCP also seems to support stem cell proliferation, survival, and differentiation into bone.  Kresbach and others showed that TCP most consistently yielded bone formation when used as a delivery vehicle for mesenchymal stem cells compared to other biomaterials commonly used, such as gelatin sponges and demineralized bone matrix.  However, there are no studies that have ascertained how well stem cells attach to TCP, and this attachment is an important factor in determining how many stem cells reach the site of injury.  This study by Kaigler and his group (A. Rajan and others) showed that a 30-minute incubation of the cells with TCP gave sufficient attachment of the cells to the TCP for clinical use.  The efficiency of this incubation period was also not affected by the temperature.  

The other exciting features of this paper, is that most of the materials used in this study were commercially available.  The bone marrow stem cell isolation technique was pioneered by Dennis JE, and others in their 2007 article in the journal Stem Cells (25:25752582).  Effective commercialization of this technique has shown the efficacy of this procedure for clinical use.  This paper also shows the clinical feasibility of using TCP as a delivery vehicle for mesenchymal stem cell-based bone treatments.

In conclusion, I will quote the authors: “Cell survival and seeding efficiency in the context of tissue engineering and cell-therapy strategies are critical parameters for success that have not been rigorously examined in a clinical context. This study defined optimized conditions for these parameters using an autologous stem cell therapy to successfully treat a patient who had a debilitating craniofacial traumatic deficiency. To our knowledge, there have been no other clinical reports of cell therapy for the treatment of craniofacial trauma defects. This clinical report serves as solid foundation on which to develop more expanded studies using this approach for the treatment of larger numbers of patients with other debilitating conditions (e.g., congenital disorders) to further evaluate efficacy and feasibility.”

Telling a Good Batch of Mesenchymal Stem Cells from a Lousy One


If a clinician isolates mesenchymal stem cells from the fat, bone marrow, or muscles of a patient, how can they tell if these cells will be effective? Short answer – they can’t. How well the cells grow in culture and how they look is the best indicator to date, but these indicators can fool you.

Fortunately, the highly productive laboratory of Darwin Prockop from the Institute of Regenerative Medicine at Texas A & M has discovered that the expression of a gene called TSG-6 can act as an indicator for human bone marrow mesenchymal stem cell quality.

In this paper, Prockop and others examined mice that had suffered damage to the surfaces of their eyes (corneas). To mitigate the inflammation in the eye, Prockop and his colleagues applied bone marrow-derived mesenchymal stem cells, but it was clear that the stem cell batches varied remarkably in their ability to regulate inflammation.

Prockop and his group then examined the genes expressed in the different batches of bone marrow-derived mesenchymal stem cells (MSCs) in order to determine if there was a gene that was consistently expressed in the effective batches as opposed to the ineffective batches.

Fortunately, they hit pay dirt. Reverse Transcriptase-PCR assays of human MSCs for the TSG-6 gene accurately predicted their ability of a specific batch of cells to modulate inflammation during corneal injury, or damage to the body wall (sterile peritonitis), or drug-induced injury to the lung. Thus, if you want implanted MSCs to modulate inflammation, then you want cells that express TSG-6 at a high level.

However, if you want MSCs that make bone, then you do not want cells that express high levels of TSG-6 because the levels of TSG-6 mRNA were negatively correlated with their potential for osteogenic (bone cell) differentiation in culture.

Additionally, when donated MSCs from male and female donors were examined and compared, it was clear that MSCs from female donors more effectively suppressed sterile inflammation, expressed higher levels of TSG-6, and had slightly less osteogenic potential than those from male donors.

Thus, TSG-6 is a marker that can measure the ability of a batch of MSCs to suppress inflammation. It is unclear if this same gene marker equally applies to other types of MSCs, but that will hopefully become clear with further work. Also, markers that correlate with the ability of these cells to do other types of regenerative activities might also result from experiments like these.