Thesis (PhD (Physiological Sciences))--University of Stellenbosch, 2007. / SUPERFICIAL digital flexor tendon injury has a serious negative impact on the
competitive horse industry. Injured horses require up to a year of rest for recovery and
likelihood of re-injury upon return to normal activity is as high as 80 %. Tendon healing
requires (a) production of collagen by fibroblasts, to provide tensile strength and elasticity to
the tendon, (b) minimisation of restrictive fibrosis, which compromises tendon gliding
function and (c) minimisation of peritendinous adhesions. We review conventional
treatments for tendon healing before exploring stem cell application as a therapeutic
alternative. We promote the use of hematopoietic and mesenchymal stem cells derived from
adult peripheral blood - as opposed to bone marrow-derived stem cells or embryonic stem cell
sources - and review published research output in this regard. In conclusion, we outline our
research objectives and present and discuss our results in the chapters that follow.
Mononuclear cells - consisting of hematopoietic stem cells, mesenchymal stem cells
and leucocytes – were isolated from the peripheral blood of sheep and horses through red
blood cell lysis and blood plasma extraction. Cell counts and propidium iodide dye exclusion
viability tests were conducted on the cell pellets. Sheep sub samples were tested for CD45
expression and horse sub samples for CD4 and CD11a/18 cell surface markers by flow
cytometry for characterisation purposes. In both cases, separate sub samples were incubated
with matched immunoglobulin (IgG) isotypes, conjugated to fluorescein isothiocyanate
(FITC), to serve as controls. For the culture of mononuclear cells, 4.5 x 106 cells were
selected for autologous sheep injections, 3 x 106 CD45- cells for allogeneic sheep injections
(the latter excluding leucocytes that may induce an immune response) and 72 x 106 cells for
horse injections. These cells were incubated with bromo-deoxyuridine (BrdU), cultured and
subsets were extracted for a second round of cell counts and viability tests before being
resuspended in blood plasma. For the horse samples an additional 1 x 106 mononuclear cells
were incubated until reaching 60 % confluence and tested for myogenic differentiation. Low
cell mortality and lack of fluorescence from IgG-FITC controls reflected effective protocols
and a lack of false positive results. The fact that the equine cell population differentiated into
myotubes verified the presence of mesenchymal stem cells in injections.
We tested whether surgical incisions or collagenase injections best mimicked naturally
occurring tendon injuries and compiled macroscopic and microscopic descriptions of tendon
injury sites at seven weeks post-injury. The superficial digital flexor tendons of 27 sheep
received an incision, a collagenase injection or a saline control injection. After one week a number of sheep were sacrificed while the remainder received further saline treatment and
were sacrificed after another seven weeks. Tendons were examined through clinical
observations, image analysis of maximum tendon diameter, mechanical testing and
histological sectioning of affected tissues. Collagenase-induced injury resembled tendonitis
more closely than surgically-induced injury. Collagenase-injured tendons (a) induced
lengthier lameness in affected limbs, (b) were more swollen and difficult to palpate, (c)
assumed the bow appearance characteristic of natural injury, (d) experienced extensive
haemorrhage due to collagen lysis, (e) had decreased elasticity and capacity to carry loads and
stress, (f) displayed decreased stiffness due to collagen fibre disruption and (g) developed
severe inflammation. After seven weeks injured tendons displayed increased vascularisation
in the areas of haemorrhage and in the adjacent collagen matrix. High inflammation rates and
low collagen levels however still persisted.
Collagenase injections were used to induce tendonitis in the superficial digital flexor
tendons of 27 sheep. After one week these tendons received treatment with a control saline
solution, autologous peripheral blood mononuclear cells (MNCs) or allogeneic peripheral
blood CD45- MNCs. Healing rates were compared after a further seven week period by
conducting ultrasonographic evaluations, clinical observations, image analyses of maximum
tendon diameter, mechanical tests and histological investigations. Tendons treated with
MNCs displayed an improvement in echogenicity and fibre linearity, higher and more
organised collagen levels, stronger mechanical properties and less swelling. Although these
improvements were not always significant, they provided strong evidence to suggest marked
healing benefits over a longer time period.
Collagenase injections were used to induce tendonitis in the superficial digital flexor
tendons of four horses. After one week these tendons received treatment with either a control
saline solution or autologous peripheral blood mononuclear cells (MNCs). Healing rates were
compared after a further seven week period by conducting ultrasonographic evaluations,
clinical observations, image analysis of maximum tendon diameter and histological
investigations. Tendons treated with MNCs displayed significant improvements in fibre
linearity in the direct vicinity of the lesion, as well as recovery rate thereof, and experienced
less swelling when compared with their untreated counterparts. Healing trends suggested
that, given a longer period of observation post-injury, more significant improvements may
become apparent.
Human adipose tissue is known be an easily accessible and high yielding source of
multipotent mesenchymal stem cells. These stem cells could potentially be used for therapeutic advancement of tendon regeneration. Our first goal was to examine the in vitro
myogenic differentiation potential of adipose-derived, adherent mononuclear cells (MNCs)
from six adult sheep. The second goal was to characterise the population of cells isolated
through various available ovine specific, non-mesenchymal stem cell surface markers,
namely, CD1, CD31, CD34 and CD45. After incubation, only four of the six MNC cultures
started to proliferate. These four cultures all exhibited high myogenic differentiation ability.
The isolated cell populations did not express any of the non-mesenchymal stem cell specific
cell surface markers.
In conclusion, our data suggests that peripheral blood stem cells and adipose-derived
stem cells are important candidate cell types for therapeutic application to improve tendon
repair in horses and sheep. Sufficient time must be allowed following injury and prior to stem
cell treatment (at least one month) and a controlled exercise program should be followed posttreatment.
A larger sample size is required and at least six months of recovery before
macroscopic and histological repair can be analysed more accurately and conclusively.
Ultrasonography should be carried out on a continuous basis, as it is a non-invasive method of
monitoring change over time.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1146 |
| Date | 12 1900 |
| Creators | Strydom, Aliki Veruschka |
| Contributors | Niesler, C. U., Cruywagen, C. W., University of Stellenbosch. Faculty of Agrisciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
Page generated in 0.003 seconds